# Revised 1996 IPCC Guidelines Volume 3Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### C ONTENTS 

### .1 

# C ONTENTS

Acknowledgements

Preface

Overview of the IPCC Guidelines

Introduction to the Reference Manual



# C HAPTERS

1 Energy
1.1 Overview.........................................................................................................................................1-1
1.2 Data...................................................................................................................................................1-4
1.3 Fuel Combustion: Overview....................................................................................................1-7 1.4 Simple Methods (Tier 1) for Fuel Combustion ...............................................................1-7 1.5 Detailed Methods (Tiers 2 and 3) for Fuel Combustion............................................1-47 1.6 Fugitive Emissions: Overview................................................................................................1-99 1.7 Fugitive Emissions from Coal Mining and Handling......................................................1-99 1.8 Fugitive Emissions from Oil and Natural Gas Activities ...........................................1-114
1.9 Further Work...........................................................................................................................1-135
1.10 References..................................................................................................................................1-136



### 2 Industrial Processes
2.1 Overview.........................................................................................................................................2-1 2.2 General Methodology.................................................................................................................2-4
2.3 Cement Production.....................................................................................................................2-5

## C ONTENTS

C ONTENTS 

### .2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.4 Lime Production...........................................................................................................................2-8
2.5 Limestone and Dolomite Use.................................................................................................2-9
2.6 Soda Ash Production and Use..............................................................................................2-11
2.7 Production and Use of Miscellaneous Mineral Products ............................................2-13
2.8 Ammonia Production...............................................................................................................2-14
2.9 Nitric Acid Production.............................................................................................................2-17 2.10 Adipic Acid Production............................................................................................................2-19
2.11 Carbide Production...................................................................................................................2-20
2.12 Production of Other Chemicals...........................................................................................2-22
2.13 CO 2 Emissions from Metal Production...........................................................................2-26 2.14 Pulp and Paper Industries........................................................................................................2-39
2.15 Food and Drink..........................................................................................................................2-41 2.16 Production of Halocarbons and and Sulphur Hexafluoride.......................................2-42 2.17 Consumption of Halocarbons and Sulphur Hexafluoride..........................................2-43
2.18 References....................................................................................................................................2-64



### 3 Solvent and Other Product Use
3.1 Overview........................................................................................................................................3-1
3.2 NMVOC Emissions from Solvent and Other Product Use........................................3-2
3.3 References......................................................................................................................................3-4


### 4 Agriculture
4.1 Overview........................................................................................................................................4-1
4.2 Methane and Nitrous Oxide Emission from Domestic Livestock Enteric Fermentation and Manure Management.............................................................................4-3 Appendix A Data Underlying Default Emission Factors for Enteric Fermentation...................4-29 Appendix B Data Underlying Default Emission Factors for Manure Management...................4-37 Appendix C Derivation of Tier 2 Enteric Fermentation Equations for Methane.......................4-49
4.3 Methane Emissions from Rice Cultivation: Flooded Rice Fields .............................4-53 Appendix Intercomparability of Methane Emission Data from Rice Cultivation...................4-71 4.4 Greenhouse Gas Emissions from Agricultural Burning...............................................4-73 4.5 Greenhouse Gas Emissions from Agricultural Soils.....................................................4-87
4.6 References.................................................................................................................................4-125

## C ONTENTS

C ONTENTS 

### .3 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5 Land-Use Change & Forestry
5.1 Overview.........................................................................................................................................5-1
5.2 Basic Calculations......................................................................................................................5-11
5.3 CO 2 Emissions and Uptake by Soils from Land-Use Change and Management........................................................................................................................5-35
5.4 Refinements in Calculations...................................................................................................5-51 T5 Technical Appendix Deforestation Data...................................................................................................................5-59
5.5 References....................................................................................................................................5-65



### 6 Waste
6.1 Overview.........................................................................................................................................6-1 6.2 Methane Emissions from Solid Waste Disposal Sites.....................................................6-2 6.3 Methane Emissions from Wastewater Handling...........................................................6-13 6.4 Nitrous Oxide Emissions from Human Sewage............................................................6-28
6.5 Emissions from Waste Incineration....................................................................................6-28
6.6 References....................................................................................................................................6-30Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual ACKNOW.1 

# A CKNOWLEDGEMENTS

The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (Revised Guidelines) were accepted by the Intergovernmental Panel on Climate Change (IPCC) at its Twelfth Session (Mexico City, 11-13 September 1996). Earlier, Working Group 1 of the IPCC at its Sixth Session (Mexico City, 10 September 1996) had accepted and then forwarded the Revised Guidelines to the IPCC. The IPCC-XII recommended that the Revised Guidelines “are ready for use by Parties to the UN Framework Convention on Climate Change (UNFCCC) in the preparation of their National Communications with regard to inventories, at a time to be agreed by the Parties of the Convention.” It is, therefore, extremely gratifying that the consensus effort of nearly one hundred and forty scientists and national experts from more than thirty countries has resulted in the publication of the Revised Guidelines

. At the Fourth Session of the Subsidiary Body for Scientific and Technological Advice (SBSTA-4, Geneva, 16-18 December 1996), Parties to the Convention decided how, and when, the Revised Guidelines are to be applied. To assist Parties in meeting their commitments and targets, and to monitor progress, it is essential that national GHG emission inventories contain the best possible information for all major GHG sources and sinks. As such, inventories must be consistent, comparable, complete, and transparent. The Revised Guidelines provide such a methodology for the estimation and periodic update of national greenhouse gas (GHG) inventories, and thus comply with the requirements of Articles 4 and 12 of the UNFCCC.
The Revised Guidelines were developed over a two-year period and draw extensively upon the previous Guidelines . Where possible, the Revised Guidelines improved upon the early 1995 Guidelines by the synthesis and assessment of relevant new data. These improved data are critical for regions of the world where baseline information is still sparse. In areas of scientific advancement, existing methodologies were revised, and additional methodologies were developed and assessed. A Summary of the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories can be found in Annex 3 of the Reporting Instructions

. We are indebted to the Co-chairs of the IPCC Expert Groups and the Experts who generously supported this work. Their dedication to quality and timeliness was truly remarkable. Core funding for the IPCC Unit for GHG Inventories is provided through the IPCC Trust Fund. Other contributions, financial and otherwise, have been received from numerous governments (Canada, European Union, Netherlands, Norway, United Kingdom, United States) and several institutions, organisations and programmes (European Environment Agency, Institute of Environmental Studies, United Nations Environment Programme Country Studies, United States Country Studies Programme). We are most grateful to the governments of Brazil, Switzerland, Thailand and the United

## A CKNOWLEDGEMENTS

A CKNOW 

### .2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Kingdom for kindly hosting the meetings of the IPCC Expert Groups and the Greenhouse Gas Liaison Group (GILG) . We warmly thank the Co-chairmen and the members of the Technical Support Unit of Working Group I, and the staff of the IPCC/OECD/IEA GHG inventory programme. In this context, we particularly express our gratitude to Bo Lim and Karen Tréanton in their capacity as Co-editors of the Revised Guidelines , and Audrey Glynn-Garnier and Sharon Michel for formatting the Guidelines . Finally, we express our sincere appreciation to our Visiting Scientists, Yamil Bonduki, Alexey Kokorin, Isabelle Mamaty and Katrina Marekova for their invaluable input to this effort.

Professor B. Bolin Dr. N. Sundararaman Chairman of the IPCC Secretary of the IPCC

Contributors to the **Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories** 

Chapter 1: Energy

**Co-Chairs of Expert Group on Fuel Combustion** Simon Eggleston (United Kingdom). Jean-Yves Garnier (IEA). David Mobley (USA). **Expert/Author for Non-CO 2**  **Tier 1 Approach** K. Mareckova (Slovak Republic). **Experts/Authors for Harmonisation Between IPCC and CORINAIR Inventories** J. P. Fontelle (France), K. E. Joerss (Germany), T. Simmons (United Kingdom), K. Tréanton (IEA). **Experts/Authors for Emissions from Aircraft** N. A. Kilde (Denmark), and J. Olivier (The Netherlands). **Experts/Contributors** W. Barbour (USA), L. Beck (USA), P.L. Canegallo (Italy), F. Carnovale (Australia), M. Emmott (United Kingdom), G. McInnes (Denmark) J. Meijer (IEA), R. Montgomery (Luxembourg), H.S. Mukunda (India), T. Pulles (The Netherlands), E. Radwanski (Poland), S. Richardson (United Kingdom), M. Ritter (Austria), H. Saddler (Australia), Z. Samaras (Greece), and T. Simmons (United Kingdom).

## A CKNOWLEDGEMENTS

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual ACKNOW.3 Chapter 2: Industrial Processes

**Co-Chairs of Expert Group on Industrial Processes and ‘New Gases’** Art Jaques (Canada). Audun Rosland (Norway). **Secretary of the Expert Group** F. Weidemann (Norway). **Experts/Authors** H.T. Haukås (Norway), A. Jaques (Canada), F. Neitzert (Canada), A. Rosland (Norway), K. Rypdal (Norway), and F. Weidemann (Norway). **Experts/Contributors** F. Carnovale (Australia), M. T. Duarte Neves Anacleto (Portugal), C. Ebert (USA), T. Fukushima (Japan), E. Kvist (Sweden) J. Lupinacci (USA), K. Mareckova (Slovak Republic), A. McCulloch (United Kingdom), J.G.J. Olivier (The Netherlands), H. Oonk (The Netherlands), K.l Øren (Norway), G. Salway (United Kingdom), T. Simmons (United Kingdom), and V. Simpson (United Kingdom).

Chapter 4: Agriculture

**Co-Chairs of Expert Group on Nitrous Oxide from Agricultural Soils** Carolien Kroeze (The Netherlands). Arvin Mosier (USA). **Experts/Authors** C. Kroeze (The Netherlands), A. Mosier (USA), C. Nevison (USA), O. Oenema (The Netherlands), S. Seitzinger (USA), and O. van Cleemput (Belgium). **Experts/Contributors** L. Bakken (Norway), P. Bielek (Slovak Republic), S. Bogdanov (Bulgaria), Y. Bonduki (Venezuela), A. F. Bouwman (The Netherlands), R.A. Delmas (France), F.J. Dentener (The Netherlands), R. Francisco (Philippines), J. Freney (Australia), S. Frolking (USA), P. Groffman (USA), O. Heinemeyer (Germany), R. Karaban (Russian Federation), L. Klemedtsson (Sweden), P.A. Leffelaar (The Netherlands), E. Lin (China), K. Minami (Japan), W.J. Parton (USA), D.C. Parashar (India), R. Scholes (South Africa), R. Sherlock (New Zealand) K. Smith (United Kingdom), H.G. van Faassen (The Netherlands), E. Veldkamp (USA), G.L. Velthof (The Netherlands), and G.X. Xing (China).

**Chair of Expert Group on Methane Emissions from Rice Cultivation** Dieter H. Ehhalt (Germany). **Experts/Authors** R. Conrad (Germany), A. P. Mitra (India), H.U. Neue (Philippines), and R. Sass (USA).

## A CKNOWLEDGEMENTS

A CKNOW 

### .4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual **Experts/Contributors** S. Bhattacharya (India), K. Boonpragob (Thailand), O.T. Denmead (Australia), Y.A. Husin (Indonesia), M.C. Jain (India), P. Jermsawatdipong (Thailand), N. Krairapanond (Thailand), K. Minami (Japan), D.C. Parashar (India), D. Phantumvanit, S. Piamphongsant (Thailand), G.Y. Shi (China), O. Siriratpiriya (Thailand), S. Towprayoon (Thailand), G.X. Xing (China), L. Xu (China), and S.H. Yun (Republic of Korea).

Chapter 5: Land-use Change and Forestry

**Co-Chairs of Expert Group on Land-use Change and Forestry**  Sandra Brown (USA). Youba Sokona (Senegal). **Convening Experts/Authors** S. Brown (USA) and J. Winjum (USA). **Experts/Authors** A. Kokorin (Russian Federation) and M. Lorenzini (Italy). **Experts/Contributors** S. Amous (Tunisia), S. Calman (New Zealand), P. Cheng (Australia), H. Eriksson (Sweden), P. Frost (Zimbabwe), T. Karjalainen (Finland), J. Mindas (Slovak Republic), N.H. Ravindranath (India) and Y. Sokona (Senegal).

**Co-chairs of Expert Group on Emissions and Uptake of CO 2**  **from Soils** Arvin Mosier (USA). Keith Paustian (USA). **Convening Expert/Author** K. Paustian (USA). **Experts/Authors** H. Janzen (Canada), H. Tiessen (Canada), and M. van Noordwijk (Indonesia). **Experts/Contributors** O. Andrén (Sweden), E. Davidson (USA), H. Eswaran (USA), E. Fernandes (USA), P. Grace (Australia), R. Houghton (USA), J. Kimble (USA), T. Kolchingina (Russian Federation), R. Lal (USA), M. Scholes (South Africa), P. Smith (United Kingdom), G. Tian (Nigeria), P. Woomer (Kenya), and L. Zhong (China).

## A CKNOWLEDGEMENTS

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual ACKNOW.5 Chapter 6: Waste

**Co-Chairs of Expert Group on Waste** Elisabeth Aitchison (United Kingdom). Chris Franklin (United Kingdom). Tom Kerr (USA). Cindy Jacobs (USA). **Experts/Authors** E. Aitchison (United Kingdom), C. Franklin (United Kingdom), C. Jacobs (USA) and J. Woodbury (USA). **Experts/Contributors** D. Augenstein (USA), A.D. Bhide (India), D. Becker (The Netherlands), J. Bogner (USA), K. Butterback-Bahl (Germany), T. Beer (Australia), P. Czepiel (USA), L. de Rome (United Kingdom), D. Gaudioso (Italy), B. Hamelers (The Netherlands), K. Hogan (USA), N. A. Kilde (Denmark), A. Lifshits (Russian Federation), E. Matthews (USA), M. Meadows (United Kingdom), M. Milton (United Kingdom), P. Manczarski (Poland), H. Oonk (The Netherlands), F. Otieno (South Africa), R. Pipatti (Finland), S. Thorneloe (USA), A. van Amstel (The Netherlands), and I. Grietje Zeeman (The Netherlands).

**IPCC/OECD/IEA Secretariats** C. Allen (OECD), Y. Bonduki (IPCC/OECD), B.A. Callander (IPCC), J.C. Corfee-Morlot (OECD), J.Y. Garnier (IEA), A. Glynn-Garnier (IPCC/OECD), D.J. Griggs (IPCC), J. Lakeman (IPCC), B. Lim (IPCC/OECD), I. Mamaty (IPCC/OECD), J. Meijer (IEA), S. Michel (IEA), B. Nyenzi (IPCC), T. Simmons (IEA), J. Stein (IPCC/OECD), and K. Tréanton (IEA).

The **Revised 1996 IPPC Guidelines for National Greenhouse Inventories** contain material from the **1995 IPCC Guidelines for National Greenhouse Inventories (1995 Guidelines).**  The Co-Chairs of the previous Expert Groups are given in the **1995 Guidelines**

.Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### P REFACE 

### .1 

# P REFACE

Signature of the United Nations Framework Convention on Climate Change (UNFCCC) by around 150 countries in Rio de Janeiro in June 1992 indicated widespread recognition that climate change is potentially a major threat to the world's environment and economic development. The ultimate objective of the Convention is the stabilisation of greenhouse gas (GHG) concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. The Convention also calls for all Parties to commit themselves to the following objectives:

• to develop, update periodically, publish and make available to the Conference of the Parties (COP) their national inventories of anthropogenic emissions by sources and removals by sinks, of all GHG not controlled by the Montreal Protocol.

• to use comparable methodologies for inventories of GHG emissions and removals, to be agreed upon by the COP.
The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories Guidelines ( Revised Guidelines ) are intended to assist all Parties in implementing these objectives. Since 1991, development of the Revised Guidelines has been undertaken by the Working Group 1 of the IPCC under the IPCC/OECD/IEA Programme on National Greenhouse Gas Inventories . The objectives of the programme are:

• to develop and refine an internationally-agreed methodology and software for calculation and reporting of national GHG emissions;

• to encourage widespread use of the methodology by countries participating in the IPCC and Parties to the UNFCCC;

• to establish a data management system for collection, review and reporting of national data.
The Revised Guidelines are approved internationally and developed through an international process which has included:

• wide dissemination of drafts and collection of comments from national experts;

• testing of methods through development of preliminary inventories;

## P REFACE

P REFACE 

### .2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • country studies which ensure that methods are tested in a wide variety of national contexts;

• technical and regional workshops held in Africa, Asia, Latin America, Central Europe and Western Europe;

• informal expert groups convened to recommend improvements on specific aspects of the methodology.
The 1995 Guidelines were approved in November 1994. In March 1995, the Conference of the Parties (COP) of the Framework Convention on Climate Change adopted the Guidelines for the preparation of National Communications by Annex I Parties of the Convention. These Guidelines were more recently recommended for use by non-Annex I Parties at COP 2, July 1996. Recognising that the Guidelines are a living document, the IPCC approved a second phase of activity in 1994. The Revised Guidelines now include revised methodologies and default data for Fuel Combustion, Industrial Processes, Agricultural Soils, Land-Use Change and Forestry, Waste and Methane from Rice Fields. Several additional methodologies for the estimation of halofluorocarbons (HFCs), perfluorinated hydrocarbons (PFCs), sulphur hexafluoride (SF 6 ), ozone and aerosol precursors, and direct GHG (CO 2 , CH 4 , N 2 O) are in the Revised Guidelines

. Over the coming year, the Programme will continue to work on methods development, including assessment, monitoring, and validation of the Revised Guidelines . Unlike earlier programmes, products will no longer focus on revisions of the Revised Guidelines , as no major changes to the methods areanticipated for three to five years, with the possible exception of the landuse change and forestry sector. The new mode of operation places emphasis on the following areas:

• evaluation of the quality of national greenhouse gas inventory data;

• comparative scientific and technical analysis of alternative greenhouse gas inventory methodologies and their implication for policy;

• further methodological work in the area of land-use change and forestry;

• continued harmonisation with other international and national greenhouse gas inventory methodologies;

• updating emission factors and default data in all source/sink sectors of the Revised Guidelines

. Another area of general activity will be field testing of the IPCC Methodology. The object of this activity is to ensure that country experience gained through the implementation of the Revised Guidelines is incorporated into methods development and into future reiterations of the Revised Guidelines

.Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### O VERVIEW 

### .1 

# O VERVIEW OF THE 

# IPCC G UIDELINES

This document is one volume of the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories

. The series consists of three books:

• T HE G REENHOUSE G AS I NVENTORY R EPORTING I NSTRUCTIONS

• T HE G REENHOUSE G AS I NVENTORY W ORKBOOK

• T HE G REENHOUSE G AS I NVENTORY R EFERENCE M ANUAL These books together provide the range of information needed to plan, carry out and report results of a national inventory using the IPCC system.
The Reporting Instructions (Volume 1) provides step-by-step directions for assembling, documenting and transmitting completed national inventory data consistently, regardless of the method used to produce the estimates. These instructions are intended for all users of the IPCC Guidelines and provide the primary means of ensuring that all reports are consistent and comparable.
The Workbook (Volume 2) contains suggestions about planning and getting started on a national inventory for participants who do not have a national inventory available already and are not experienced in producing such inventories. It also contains step-by-step instructions for calculating emissions of carbon dioxide (CO 2 ) methane (CH 4 ), nitrous oxide (N 2 O), halocarbons (HFCs, PFCs), sulphur hexafluoride (SF 6 ), ozone and aerosol precursors, from six major emission source categories. It is intended to help experts in as many countries as possible to start developing inventories and become active participants in the inventories programme.
The Reference Manual (Volume 3) provides a compendium of information on methods for estimation of emissions for a broader range of greenhouse gases and a complete list of source types for each. It summarises a range of possible methods for many source types. It also provides summaries of the scientific basis for the inventory methods recommended and gives extensive references to the technical literature. It is intended to help participants at all levels of experience to understand the processes which cause greenhouse gas emissions and removals to occur and the estimation methods used in compiling inventories.

## O VERVIEW

O VERVIEW 

### .2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## Contents of the IPCC Guidelines All three volumes begin with the following sections: Acknowledgements Preface Overview of the IPCC Guidelines
The contents of each volume are as follows: Volume 1: Greenhouse Gas Inventory Reporting Instructions Introduction to the Reporting Instructions Chapter 1: Understanding the Common Reporting Framework Chapter 2: Reporting the National Inventory Tables: Sectoral Report Tables Summary Report Tables Overview Table Annex 1: Managing Uncertainties Annex 2: IPCC and CORINAIR Source Categories Glossary Volume 2: Greenhouse Gas Inventory Workbook
Introduction to the Workbook Module 1: Energy Module 2: Industrial Processes Module 3: Solvent and Other Product Use Module 4: Agriculture Module 5: Land-Use Change and Forestry Module 6: Waste Volume 3: Greenhouse Gas Inventory Reference Manual
Introduction to the Reference Manual Chapter 1: Energy Chapter 2: Industrial Processes Chapter 3: Solvent and Other Product Use Chapter 4: Agriculture Chapter 5: Land-Use Change & Forestry Chapter 6: Waste

## O VERVIEW

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### O VERVIEW 

### .3 

## Before you start... This diagram explains the stages needed to make a national inventory which meets IPCC standards.

Aggregate/transform data and put into standard format as outlined in the Reporting Instructions

Use software and

Workbook Use manual work sheets in Workbook Plan inventory Assemble data

Reporting recommendations - documentation - verification - uncertainty
Use Reporting Instructions

Final National Inventory

Do you want to use IPCC Computer Software Do you have a detailed

National Inventory? Yes

Yes No No

## O VERVIEW

O VERVIEW 

### .4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The flow diagram above illustrates how the different types of users (working at different levels of inventory detail) can use the various volumes of the Guidelines . You should recognise that reality is more complex than this simple explanatory chart. Many countries may have some parts of the inventory complete at a high level of detail but may only be getting started on other parts. It is quite likely that some users will need to do several iterations of the thinking process reflected in the diagram with regard to different parts of their inventory. The stages outlined in the flow diagram are: Question 1 Do you have a detailed national inventory?
Answer: Yes If your country already has a complete national inventory, you should transform the data it contains into a form suitable for use by IPCC. This means transforming it into a standard format. In order to do this, use Volume 1 of the IPCC Guidelines , Reporting Instructions. This gives details of the way in which data should be reported and documented.
Answer: No You should start to plan your inventory and assemble the data you will need to complete the Worksheets in this book. Refer to the Getting Started section of the Workbook

. Question 2 Do you want to use the IPCC computer software?
Answer: Yes If you want to use the IPCC software, you will still follow the instructions included in the Workbook to assemble the data you have collected into an inventory (see margin box). You will use the software instead of the printed worksheets to enter data.
Answer: No If you do not use the IPCC software, use the Workbook and the Worksheets it contains to assemble the data you have collected into an inventory. Finally... Inventory data should be returned to IPCC in the form recommended in the Reporting Instructions . It is important that, where you have used a methodology other than the IPCC Default Methodology, it is properly documented. This will ensure that national inventories can be aggregated and compared in a systematic way in order to produce a coherent regional and global picture.



## General Notes on the Guidelines Scope:

• The IPCC Guidelines are designed to estimate and report on national inventories of anthropogenic greenhouse gas emissions and removals. A VAILABILITY /U SE OF C OMPUTER S OFTWARE IPCC computer software is available with the IPCC Guidelines. The software includes the same simple default methods as presented in the Workbook and the Sectoral and Summary Tables for reporting inventories, as presented in the Reporting Instructions . It is available in English only. This version of the software is being produced in Excel 5.0. If you would like to receive a copy of the software, send a letter or fax
to:
IPCC UNIT FOR GHG INVENTORIES
Pollution Prevention and Control Division OECD, Environment Directorate 2, rue André-Pascal 75775 PARIS CEDEX 16 FRANCE FAX: (33-1) 45 24 78 76

## O VERVIEW

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### O VERVIEW 

### .5 In general terms “anthropogenic” refers to greenhouse gas emissions and removals that are a direct result of human activities or are the result of natural processes that have been affected by human activities. Users may include any human-induced emissions and removals in their inventory as long as they can be clearly documented and quantified.

• National inventories should include greenhouse gas emissions and removals taking place within national (including administered) territories and offshore areas over which the country has jurisdiction. There are, however, four qualifications of this principle in the Guidelines : (a) Emissions based upon fuel sold to ships or aircraft engaged in international transport should not be included in national totals but reported separately. (b) Emissions from road vehicles should be attributed to the country where the fuel is loaded into the vehicle. The error in national emissions introduced in the case of road transport is expected to be small. (c) Emissions from the combustion or decay of wood and wood products are assumed to take place in the country in which the wood was harvested and within a year of harvesting. This is because it has been determined that the most workable approach to estimating CO 2 emissions and removals from forests is to account for changes in stocks of standing biomass in forests and other locations. The simple assumption is that wood removed from stocks releases CO 2 emissions in the year and in the country where the wood was removed. While the IPCC method allows for accounting of exports and carbon stored in products, it does not yet provide a methodology, which is a priority for future work. (d) In line with the principle of national emissions, the IPCC methodology accounts for the bulk of greenhouse gas emissions related to fuel combustion in the country in which those emissions are released. The IPCC methodology for carbon stored in nonfuel products manufactured from fuels as raw materials takes into account emissions released from those products during their use or destruction. Emissions are attributed to the country where the conversion to non-energy products takes place, even when the products are traded internationally. This is believed to be a relatively small net error, but it is also a priority for future work. Data Quality and Time Frame:

• The data available to estimate anthropogenic greenhouse gas emissions resulting from fuel combustion are generally of a better quality than the data available to estimate greenhouse gas emissions and removals in the areas of agriculture and land use change/forestry. Accordingly, while the IPCC Guidelines request an emission figure for a single year in most source/sink sectors, three-year averages (with the base year in the middle) are preferred in the areas of agriculture and land use change/forestry. In addition, the IPCC Guidelines recognise that greenhouse gas emissions and removals in the area of land use change/forestry can occur over an extended period of time once the activity has been completed. For example, when estimating emissions

## O VERVIEW

O VERVIEW 

### .6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual from the abandonment of forests and grasslands, users are requested to estimate emissions related to two time periods of previous activity: (a) 0 - 20 years ago, and (b) 20 - 100 years ago.
Default Method:

• The IPCC Guidelines contain “default” methodologies for the estimation of greenhouse gas emissions and removals. Users are encouraged to go beyond these minimum default methods where possible, and report the results.
The IPCC Guidelines also include a number of “default” assumptions and data for use in the estimation of greenhouse gas emissions and removals. This default information is included primarily to provide users with a starting point from which they can develop their own national assumptions and data. Indeed, national assumptions and data are always preferred because the default assumptions and data may not always be appropriate for specific national contexts. In general, therefore, default assumptions and data should be used only when national assumptions and data are not available. Section 2 of the Introduction to the IPCC Greenhouse Gas Inventory Workbook provides information on the quality of the default data available in different greenhouse gas source/sink categories. When it is indicated that the data available are of low quality, users should recognise that the default data do not provide a basis for the development of a definitive inventory of that source/sink category.

• Many of the categories of greenhouse gas emissions and removals can be estimated only with large ranges of uncertainty. Quite naturally, some national experts have developed methods which are designed to produce ranges of estimates rather than point estimates for highly uncertain categories. The IPCC Guidelines , however, require that users provide a single point estimate for each gas and emissions/removal category. This is simply to make the task of compilation, comparison and evaluation of national reports manageable. Users are encouraged to provide uncertainty ranges or other statements of confidence or quality along with the point estimates. The procedures for reporting uncertainty information are discussed in the Greenhouse Gas Inventory Reporting Instructions

. Double Counting of Emissions: The methods proposed for the estimation of emissions sometimes simplify the inventory construction in order to use data which are more readily available than those needed for a detailed and more precise approach. In certain cases this may cause or increase the risk of double counting emissions. There are two areas where this may occur in the Guidelines

. 1) All countries preparing CO 2 inventories using the IPCC Guidelines are asked to estimate the emissions from fuel combustion using the IPCC Reference Approach either as the primary means of preparing the inventory or as a verification stage following the preparation of an inventory using national methods. The Reference Approach is a simple procedure which demands relatively little data and lends itself to wide-spread application as a "common denominator".

## O VERVIEW

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### O VERVIEW 

### .7 The Reference Approach provides an upper bound to CO 2 emissions inferred from the country's supply of fossil fuels by identifying the carbon content, subtracting from it the carbon stored in non-energy products and products made from fuels used as raw material, adjusting for carbon which remains unburnt and multiplying by 44/12. It is an upper bound 1 because some of the carbon will be emitted in forms other than CO 2 , in part because fuel combustion is not always complete but also because fuels may leak or evaporate. Consequently the CO 2 emissions figure obtained from the Reference Approach will include carbon emitted as CH 4 , CO or NMVOC. At the same time the Guidelines encourage countries to estimate separate inventories for these gases and when this is done these gases are reported twice, in their emitted form and as CO 2 . It is in this sense that they are "double counted". Use of the Reference Approach carries with it two consequences which should be carefully noted. Because the Reference Approach uses fossil fuel supply statistics as a basis for determining the carbon supply

• Not all carbon based emissions from fossil fuel are reported twice. The Reference Approach CO 2 estimate will not include emissions from combustion or release of fossil fuels for which the corresponding quantities (activity data) are not included in national production or import figures. Notable examples of activities which lead to emissions not included are the venting of natural gases from coal mining and handling and oil and gas production. Emissions from the flaring of natural gases are also excluded. As a result, when emissions from these activities are included in the relevant inventories using the fugitive emissions methodologies recommended in the Guidelines no "double counting" occurs.

• CO 2 emissions from biomass used as fuels are excluded from the total CO 2 emissions figure. The restriction of the Reference Approach to fossil fuels results from the sustainable nature of biofuels. The CO 2 emissions are, however, reported for information purposes. Note that non-CO 2 emissions from biofuels are included in their respective inventories. 2) Double counting may also occur when calculated emissions from the manufacture of products from fuels used as raw materials or from the use of fuels for their physical properties (e.g. lubricants) include emissions produced from the later destruction of these products. The double count will be with any separate reporting within the Waste module of the Guidelines of emissions from destruction. 3) When a national CO 2 inventory is constructed from emissions estimated for each source category using emission factors derived from measurements on combustion plant, care should be taken to include the CO 2 equivalent of other fossil carbon based emissions from the source

1 In practice, because of inaccuracies in the supply statistics and/or emission factors, CO 2 estimates from the Reference Approach may be less than those obtained by summing all CO 2 emissions from the combustion of fuel.

## O VERVIEW

O VERVIEW 

### .8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual category. In this manner, the resulting total CO 2 emissions can be compared with the result of the CO 2 Reference Approach as part of the inventory verification stage. If, however, CO 2 emission factors, derived from the carbon content of the fuel, are used then no addition of the CO 2 equivalent of carbon gases is required.Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### I NTRODUCTION 

### .1 

# I NTRODUCTION TO THE 

# R EFERENCE 

# M ANUAL

This Reference Manual is one of three volumes of the Revised 1996 IPCC Guidelines for National GHG Inventories. It provides a compendium of information on the various human activities which cause greenhouse gas emissions or removals to occur. It builds on work carried out in preparation of:

• OECD Report: Estimation of Greenhouse Gas Emissions and Sinks, Final Report From the OECD Experts Meeting, 18-21 February 1991 , (OECD, 1991).

• Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide, Amersfoort, NL, 3-5 February 1993 (van Amstel, 1993).

• 1995 IPCC Guidelines

. In preparing this document, the IPCC/OECD/IEA has also received valuable technical input from a number of international workshops and IPCC Expert Group Meetings. The overall purpose of these workshops was to provide a forum for experts to discuss ways to improve the methodologies and reporting procedures and to ensure widespread participation in the development process. Many of the recommendations received have been incorporated into this revised Reference Manual

. In general, the basic approach to estimating national emissions is similar across the various gases and human activities which are sources or sinks. Fundamentally, emissions are a product of activity data and emission factors. In reality, these calculations are often more complicated than this would indicate, with several steps being involved in the calculation of each of the general terms - activity data and emission factors. But it is useful to keep this general structure in mind as it provides an organising framework for all of the calculations and a means of evaluation and comparison.
The Reference Manual frequently provides a number of different possible methodologies or variations for calculating a given emission. In most cases these represent calculations of the same form but the differences are in the level of detail at which the original calculations are carried out. Wherever possible the methodology provides a "tiered" structure of calculations which describes and connects the various levels of detail at which national experts can work depending on the importance of the source category, availability of data, and other capabilities. All national experts are encouraged to work at the most detailed level which is possible and appropriate for their situation. The tiered structure ensures that estimates calculated at a very detailed level can be aggregated up to a common minimum level of detail for comparison with all other reporting countries.

## I NTRODUCTION

I NTRODUCTION 

### .2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The methodologies for the estimation of the emissions and removals of GHGs, which are presented and discussed in the Guidelines , are grouped by the main activity sectors, (chapters of this volume) namely, Energy, Industrial Processes, Solvent and Other Product Use, Agriculture, Land Use Change and Forestry, and Waste . In general, the source/sink activities are unique to their sector but there are cases, e.g., biomass burning, which occur in several sectors and are described in the chapters on Land-Use Change and Forestry, Energy and Agriculture

. The chapters are divided by subject areas and correspond to the same subject chapters in the Workbook . This document should be used by national experts as a reference tool to accompany the Workbook and the Reporting Instructions when constructing and reporting national inventories of GHG emissions and removals.



## References OECD (1991), Estimation of Greenhouse Gas Emissions and Sinks, Final Report from the OECD Experts Meeting, 18-21 February 1991 . The Organisation for Economic Co-operation and Development, Paris, France, revised August 1991. van Amstel, A.R. (ed.) (1993), Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control , Amersfoort, NL. 3-5 February 1993

. RIVM Report No. 481507003, Bilthoven, The Netherlands, July. IPCC/OECD/IEA (1995), IPCC Guidelines for National Greenhouse Gas Inventories, IPCC/OECD/IEA Inventory Programme, Paris, FranceRevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 1 

# E NERGY

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.1 

# 1. E NERGY



## 1.1 Overview This chapter discusses inventory methods for emissions of SO 2 and direct and indirect greenhouse gases from energy sources, comprising CO 2 , CH 4 , N 2 O, NO x , CO and NMVOC. Energy systems are extremely complex and widespread components of national economies. The full range of greenhouse gases is emitted from the production, transformation, handling and consumption of energy commodities. Chapter 2, Industrial Processes, discusses emissions which arise jointly from fuel use in industrial processes and provides guidance on attributing the emissions to the energy or industrial process categories. The various emissions from energy systems are organised in two main categories: Emissions from Fuel Combustion and Fugitive Emissions.

Emissions from Fuel Combustion
CO 2 emissions from fuel combustion are discussed separately and in some depth because they can be calculated accurately at a highly aggregated level, unlike other gases. CO 2 emissions are primarily dependent on the carbon content of the fuel. The IPCC Reference Approach for CO 2 emissions is a simple, accurate and internationally transparent approach which takes advantage of this fact.
CO 2 from energy activities can be estimated from energy supply data, with a few adjustments such as for carbon non-oxidised. Supply data for all commercial fuels are available from international data bases covering individual countries of the world. These data, together with typical carbon content figures, provide a sound starting point for the estimation of CO 2 inventories, particularly for global or regional studies. However, because fuel qualities and emission factors may differ markedly between countries, sometimes by as much as ten percent for nominally similar fuels, national inventories should be prepared using local emission factors and energy data where possible.
Unlike CO 2 , national inventories of CH 4 , N 2 O, NO x , CO and NMVOCs require more detailed information. Accurate estimation of their emissions depends on knowledge of several interrelated factors, including combustion conditions, technology, and emission control policies, as well as fuel characteristics. The methods must, in general, be applied at a detailed activity/technology level. CO 2 emissions may also be calculated at the more detailed level required for other gases. Indeed, when calculating non-CO 2 emissions national experts are encouraged to calculate CO 2 emissions at the same time, as reconciliation of total CO 2 emissions estimated in this manner with those obtained from the Reference Approach provides a valuable verification process. Procedures for estimating CO 2 and non-CO 2 emissions at the detailed or more aggregated levels of activity are presented in this chapter. The methods for estimating the gases are divided in “Tiers” encompassing different levels of activity and technology detail. Tier 1 methods are generally very simple requiring less data and expertise than the most complicated Tier 3 methods.
Fugitive Emissions In addition to the emission of greenhouse gases from fuel combustion, other emissions into the atmosphere occur in an unplanned or a deliberate manner. These are fugitive emissions. Fugitive emissions are intentional or unintentional releases of gases from anthropogenic activities. In particular, they may arise from the production, processing, transmission, storage and use of fuels, and include emissions from combustion only where it does not

## E NERGY

1.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual support a productive activity (e.g., flaring of natural gases at oil and gas production facilities). The most significant greenhouse gas emissions in this category are methane emissions from coal mining and from oil and gas systems. There are also emissions of other gases, such as CO 2 and NMVOCs as fugitive or by-product emissions from energy systems.



### 1.1.1 Recent Developments As part of Phase II of the IPCC/OECD/IEA Programme on National Greenhouse Gas (GHG) Inventories an expert group on GHG Emissions from Fuel Combustion was set up. The group included over forty experts from various geographical and professional backgrounds. The terms of reference of this group were to continue improving the estimation methodologies on emissions from fuel combustion which had been published in the IPCC Guidelines for National Greenhouse Inventories in March 1995. The issues addressed by the group can be divided into several broad areas:

• harmonisation of international emission estimation methodologies and reporting;

• improvement and review of emission factors;

• development of a new Tier 1 method for estimating non-CO 2 GHG and SO 2 emissions based on fuel consumption;

• development of a new Tier 2 method for estimating emissions from aircraft. In addition the group identified areas for further work. These are listed at the end of this chapter. The results of the group’s work on the final three items listed above are contained in the sections which follow. The experts’ conclusions following a review and discussion of the harmonisation of methodologies are summarised in the following statement.
Harmonisation of International Emission Estimation Methodologies and Reporting Two approaches to drawing up and presenting national emission inventories in comparable form are currently in use:

• The IPCC Guidelines for National Greenhouse Gas Inventories, and

• the joint EMEP/CORINAIR Atmospheric Emission Inventory Guidebook. Countries which are Parties to both Conventions have to apply both reporting procedures to each Convention. The IPCC approach meets FCCC needs for calculating national totals (without further spatial resolution) and identifying sectors within which emissions occur, whereas the EMEP/CORINAIR approach is technology based and includes spatial allocation of emissions (point and area sources). Both systems follow the same basic principles :

• complete coverage of anthropogenic emissions (CORINAIR also considers natural emissions);

• annual source category totals of national emissions;

• clear distinction between energy and non-energy related emissions;

• transparency and full documentation permitting detailed verification of activity data and emission factors.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.3 To date, considerable progress has been made in the harmonisation of the IPCC and EMEP/CORINAIR approaches. The IPCC Expert Group on Fuel Combustion has made changes to the fuel list and to the source/sink categories to allow more direct comparison of the two approaches:

• Biomass fuels will be allocated to the various source categories (CO 2 from biomass will not be reported in national totals).

• In order to estimate the full emissions of the industry sector, emissions from autoproduction should be included with emissions from other fuel use within industry. At the same time the emissions from the autoproduction of electricity and heat should be excluded from the energy transformation source category to avoid double counting. This change brings the IPCC source categories for manufacturing and transformation industries into line with those used by CORINAIR.

• Treatment of evaporative emissions (NMVOC) from road transport in the IPCC Tier 2 method is consistent with CORINAIR. Combustion and evaporative emissions should be reported separately. In the IPCC Tier 1 method, all emissions from road transport are included together under fuel combustion. The CORINAIR programme has now developed its approach further to include additional sectors and sub-divisions (e.g. the definition of civil aviation is now in line with the IPCC definition) so that a complete CORINAIR inventory, including emission estimates, can be used to produce reports in both the FCCC/IPCC or EMEP/CORINAIR reporting formats for submission to their respective Conventions. Minor adjustments based on additional local knowledge may be necessary to complete such reports for submission. One difference between the approaches remains:

• Spatial allocation of road transport emissions: here CORINAIR, with a view to the input requirements of atmospheric dispersion models, applies the principle of territoriality (emission allocation according to fuel consumption) whereas the IPCC is bound to the principle of political responsibility (allocation according to fuel sale). For the IPCC, countries with a big disparity between emissions from fuel sales and fuel consumption have the option of estimating true consumption and reporting the emissions from consumption and trade separately. However, national totals must be on the basis of fuel sales.



### 1.1.2 Organisation of the Chapter In addition to this introduction, this chapter is organised into four separate substantive sections covering fuel combustion and fugitive emissions:

• Simple Methods (Tier 1) : Emissions from all sources of combustion are estimated on the basis of the quantities of fuel consumed and average emission factors. The IPCC Reference Approach for CO 2 is presented together with new methods for the estimation of CO 2 and non-CO 2 emissions from the main source categories.

• Detailed Methods (Tiers 2/3) : Emission estimations are based on detailed fuel/technology information covering stationary and mobile sources.

• Fugitive emissions from coal mining and handling : Emissions are generated as a result of the mining and handling of coal, primarily methane emissions from coal mining. Other emissions of GHGs from coal mine and waste fires are briefly discussed.

## E NERGY

1.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Fugitive emissions from oil and natural gas activities : Methane emissions from natural gas flaring and venting, and from natural gas production, transmission and distribution are the most important for this category. CO 2 emissions from venting and flaring are included as are NMVOC emissions from production, processing and distribution of oil and oil products. A new section briefly describes the estimation of emissions of ozone precursors and SO 2 from refineries.



## 1.2 Data

1.2.1 Data Sources
Activity Data Subject to the requirements outlined below and intended to ensure the comparability of country inventories, the IPCC approach to the calculation of emission inventories encourages the use of fuel statistics collected by an officially recognised national body, as this is usually the most appropriate and accessible activity data. In some countries, however, those charged with the task of compiling inventory information may not have ready access to the entire range of data available within their country and may wish to use data specially provided by their country to the international organisations whose policy functions require knowledge of energy supply and use in the world. There are, currently, two main sources of international energy statistics: the International Energy Agency of the Organisation for Economic Co-operation and Development (OECD/IEA), and the United Nations (UN). The primary energy data sources cited in this report include:

• From the OECD/IEA: Energy Statistics and Balances of Non-OECD Countries (OECD/IEA, 1996b); Energy Balances of OECD Countries (OECD/IEA, 1996a); and Energy Statistics of OECD Countries (OECD/IEA, 1996 c ).

• From the United Nations: Energy Statistics Yearbook (UN, 1996). Both international organisations collect energy data from the national administrations of their member countries through systems of questionnaires. The data gathered are therefore “official” data. To avoid duplication of reporting, where countries are members of both organisations, the UN receives copies of the IEA questionnaires for the OECD member countries rather than requiring these countries to complete the UN questionnaires. When compiling its statistics of non-OECD member countries the IEA, for certain countries, uses UN data to which it may add additional information obtained from the national administration, consultants or energy companies operating within the countries. Statistics for other countries are obtained directly from national sources. The number of countries covered by the IEA publications is fewer than that of the UN. 1

Emission Factors Emissions of GHGs from fuel combustion and fuel supply activities are calculated by multiplying levels of activity by emission factors usually expressed as mass of pollutant per

1 Approximately 130 countries (of about 170 UN Member countries) are included in the IEA data, but the countries it includes account for about 98 per cent of worldwide energy consumption and nearly all energy production.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.5 energy unit of activity (e.g. kg N 2 O/TJ). The most commonly used activity measure for energy-related emissions is the amount of fuel burned or, where fugitive emissions are concerned, the amount of fuel produced or distributed. In some cases other measures of activity are used, most notably in calculating emissions from the transport sector. A number of international and national sources of energy activity data and industry emission factors exist largely as a result of international and national analyses of alternative control policies for SO x , NO x and NMVOC. A few sources have also recently emerged on various other GHGs. The more detailed factors (for gases other than CO 2 ) do not relate directly to national energy activity data described below, but require some additional information. The sources of emission factor data, and procedures for making these linkages are discussed in the context of specific gases and source types, in the relevant sections which follow.



### 1.2.2 Comparability of Reporting In order to meet the objectives of the IPCC/OECD/IEA programme, inventories must be readily comparable. This requires a large measure of commonality of definitions of activities (source/sink categories) and fuel product groups and the use of a reporting discipline which makes evident the construction of the inventory from the activity data. Specific guidelines for reporting have been prepared. In order to reduce the uncertainty created by possibly different definitions, the IPCC Reporting Instructions have largely adopted definitions utilised by the IEA for the regular collection of energy data from OECD member countries. The active co-operation between the UN Statistical Division (New York), the UN ECE (Geneva), Eurostat and the IEA has ensured that there are now very few differences between the definitions employed by these organisations for the collection of their energy data. The IEA definitions may be found in the Glossary at the end of the Reporting Instructions (Volume 1). Although common standards for the collection of data by international organisations exist the presentation of the data collected can be different. At least five aspects of energy data presentations need to be checked prior to using data for greenhouse gas inventories:

• Are the energy data expressed in terms of net calorific values (NCV) or gross calorific values (GCV)? 2 Since most of the world uses net calorific values, the IPCC Guidelines uses net calorific values.

• Are non-commercial fuels, including wood and other biomass fuels, included? 3

• Are wood waste, agricultural wastes or waste-derived fuels included if combusted for energy production? These fuels should be accounted for in the IPCC methodology, but are included with biomass fuels.

2 The IEA generally reports data in net calorific values. The difference between the net and the gross calorific value of a fuel is the heat of condensation of moisture in the fuel during combustion. The net calorific value excludes this. The IEA assumes that net calorific values are 5 per cent lower than gross calorific values for oil and coal, and 10 per cent lower for natural gas.
3 While some of these fuels (such as wood) may be included in national orinternational data sets, it is likely that they are underestimated due to poor recordkeeping and lack of statistical information for non-commercial fuels.

## E NERGY

1.6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Is non-energy fuel usage (if non-oxidised) accounted for? 4

• How are international bunker fuels for air and ship transport treated? 5 Given responses to these questions, several adjustments may need to be made to the energy data being used in order to formulate a complete inventory of greenhouse gases. If published IEA data are being used the following corrections must be made: 1 Consumption of vegetal fuels in non-OECD countries should be added to commercial fuel consumption. Estimates of the former are available in the IEA publication cited. Consumption of vegetal fuels, as declared by OECD countries in their reports to the IEA, are included as “Combustible Renewables and Wastes” in the IEA statistics for these countries. 2 International energy statistics show fuel consumption by industrial and commercial electricity generators (autoproducers) as an identified part of fuel use by the energy industries. In order to harmonise inventory preparation with the EMEP/CORINAIR methods, countries preparing IPCC inventories should include autoproducer fuel consumption in the industry and commercial sectors and remove it from energy industries. See Recent Developments above. 3 Care is required when estimating the amount of fuel used without oxidation in the manufacture of non-energy products. IEA data generally cover only deliveries to the industry sector manufacturing such products. Some of the fuels delivered will be oxidised by the user. See Chapter 2, Industrial Processes, Overview.
4 IEA data do not include deliveries of oil for international air transport as part of the International Bunkers data. Where data are available they are identified as part of the national transport sector fuel consumption. UN estimates are available for many countries.



### 1.2.3 Uncertainty
The Reporting Instructions , Volume 1, make explicit provision for the reporting of estimates from all source categories identified in the Standard Data Tables. Energy activity data and emission factors are both subject to wide variations through uncertainties in basic data, identification of fuel qualities, calorific values and measurements in emissions. Furthermore, the uncertainties in estimates of fugitive emissions can be larger than those from fuel combustion as wider ranges in natural resource conditions and operations practice exist for fuel extraction and processing. This topic is discussed further in Section 1.8.7. Managing and combining uncertainty estimates from several sources is discussed in Appendix 1 to the Reporting Instructions

.

4 This is normally reported in primary energy requirements but is not combusted and therefore does not contribute directly to greenhouse gas emissions.

5 International bunker fuels are combusted in ships at sea and by airplanes (both undertaking international movements) and therefore should be included in global greenhouse gas estimations. Following guidance from the INC, the IPCC recommends that every country estimate emissions from international bunker fuels sold within national boundaries, but that these emissions would be reported separately and, as far as possible, excluded from national totals.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.7 

## 1.3 Fuel Combustion: Overview In the initial stages of the IPCC/OECD/IEA programme it was recognised that work on both methods development and national inventories needed to be prioritised, as it was not possible to deal with all of the gases and sources simultaneously. Priority was given to the direct GHGs in the order: carbon dioxide, methane and nitrous oxide (IPCC/OECD, 1991). In Phase II of the Guidelines development, an attempt has been made to identify default methods for a simplified Tier I method for estimating emissions of the GHGs and SO 2 . The purpose of a Tier 1 method is to assist countries that cannot access detailed fuel use and technology data to develop emission inventories. Consequently, the Tier 1 method should enable at least rough emission estimations of CO 2 , CH 4 , N 2 O, NO x , CO and NMVOC using energy statistics, and of SO 2 by using additional assumptions on the sulphur content of the fuels.
The Tier 1 method should be used in cases where no detailed information is available on fuel type, technology and operating conditions. If countries have more exact national emission factors, these (and not the default factors) should be used. Countries wanting to do more detailed emission estimations may use the Tier 2 method described in Section 1.5. A third option which may be used (Tier 3) is the CORINAIR 94 methodology which is described in the EEA TF Emission Inventory Guidebook and is available on CD-ROM 6

.


## 1.4 Simple Methods (Tier 1) for Fuel Combustion

The Tier 1 method for CO 2 is fairly well established and is explained in Section 1.4.1. For non-CO 2 gases, a simplified methodology has been developed to estimate emissions by applying emission factors to fuel statistics which are organised by sector. In reality, emissions of these gases depend on the fuel type used, combustion technology, operating conditions, control technology, and on maintenance and age of the equipment. However, since it is unlikely that many countries will have this detailed data, the Tier 1 method ignores these refinements (see Box 1). Section 1.4.2 provides average non-CO 2 emission factors for the agreed IPCC source categories together with additional information on the range of these factors and their use. The proposed values are based on emission factors included in Radian Corporation (1990), US EPA (1995), the EDGAR database 7 , the CORINAIR 1990 database and scientific reports from different countries. SO 2 emission factors are estimated using a formula based on sulphur content in the fuel. The compilation of default factors for biomass fuels in the “Other Sectors” has been based on measurement data reported by Smith and Ramakrishna (1990), Berdowski et al. (1993a and 1993b), Delmas (1993), Smith et al. (1993), Delmas et al. (1995), Veldt and Berdowski (1995) and Brocard et al. (1996).

6 The CD-ROM may be obtained by contacting the European Environment Agency, Kongens Nytorv 6, 1050 Copenhagen, Denmark.

7 EDGAR Version 2.0 was developed by TNO and RIVM and is a set of global emission inventories of greenhouse gases and ozone-depleting substances for all anthropogenic and most natural sources on a per country basis and on 1 o x 1 o grid (Olivier et al., 1995).

## E NERGY

1.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual For aircraft, the emission factors for the Tier 1 method are based on the fleet average values of NO x , CO and NMVOC of the global inventories compiled by NASA, ECAC/ANCAT, WSL and NLR [Wuebbles et al. (1993); Olivier (1995); Brok (1995)].

B OX 1 M AIN F UEL G ROUPS In the Tier 1 method for non-CO 2 gases, the fuels are aggregated into the following main groups:

• coal

• natural gas

• oil gasoline for transport; diesel oil for transport; other oil products.

• biomass wood / wood waste; charcoal; other biomass and wastes (includes dung, agricultural, municipal and industrial wastes, bagasse and agricultural residues). Note: Refer to Section 1.2 of the Common Reporting Framework in the Reporting Instructions for details on which products are included in each of the main groups.
The default emission factors are internally consistent and it is essential to preserve this consistency when replacing the default by local values so that total emissions of carbon (for example) do not exceed the carbon available in the fuel.



### 1.4.1 Carbon Dioxide (CO 2 

### ) Emissions In this section the methodology for estimating CO 2 emissions from energy is discussed. Carbon dioxide (CO 2 ) is the most common greenhouse gas produced by anthropogenic activities, accounting for about 60 per cent of the increase in radiative forcing since preindustrial times (IPCC, 1992). By far the largest source of CO 2 emissions is from the oxidation of carbon when fossil fuels are burned, which accounts for 70-90 per cent of total anthropogenic CO 2 emissions. When fuels are burned, most carbon is emitted as CO 2 immediately during the combustion process. Some carbon is released as CO, CH 4 , or non-methane hydrocarbons, which oxidise to CO 2 in the atmosphere within a period from a few days to 10-11 years. The IPCC methodology accounts for all of the carbon from these emissions in the total for CO 2 emissions. The other carbon-containing gases are also estimated and reported separately (see following sections for methodologies for estimating CH 4 , CO, and NMVOCs). 8

8 It is important to note that there is an intentional double counting of carbon emitted from combustion. This format treats the non-CO 2 gases as a subset of CO 2 emissions and ensures that the CO 2 emission estimates reported by each country represent the entire amount of carbon that would eventually be present in the atmosphere as CO 2 . The

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.9 Fuel combustion is widely dispersed throughout most activities in national economies making assembly of a complete record of the quantities of each fuel type consumed in each "end use" activity a considerable task which some countries have not yet completed. Fortunately, it is possible to estimate national CO 2 emissions by accounting for the carbon in fuels supplied to the economy. This is the basis of the IPCC Reference Approach. The supply of fuels is simple to record and is more likely to be available in many countries than detailed end use consumption statistics. The Reference Approach requires statistics for production of fuels and their external trade as well as changes in their stocks. It also needs a limited number of figures for the consumption of fuels used for non-energy purposes where carbon may be stored. It uses a simple assumption: once carbon is brought into a national economy in fuel, it is either saved in some way (e.g., in increases of fuel stocks, stored in products, left unoxidised in ash) or it must be released to the atmosphere. In order to calculate the carbon released it is not necessary to know exactly how the fuel was used or what intermediatetransformations it underwent. In this respect the methodology may be termed a “topdown” approach compared with the “bottom-up” methods used for other gases. As stated in the Overview , this does not mean that a “bottom-up” approach should not be followed for estimating CO 2 emissions but the total emissions must be compared with those obtained from the Reference Approach. A “bottom-up” method for CO 2 is briefly discussed later in this section. When estimating CO 2 emissions from fuel combustion there are a number of points of a statistical, technical or procedural nature which affect several of the estimation methods.

• Fuel Carbon and Energy Content: There is considerable variation in the carbon and energy content by weight of fuels. However, expressing the carbon emission factor as the carbon content per unit of energy released reduces this variation because of the close link between the carbon content and energy value of the fuel. It is natural therefore that all fuel supply and consumption data for combustion emission calculations be expressed in energy units. Energy data expressed in other units should be converted to terajoules before use.

• Unoxidised Carbon: When energy is consumed not all of the carbon in the fuel oxidises to CO 2 . Incomplete oxidation occurs due to inefficiencies in the combustion process that leave some of the carbon unburned or partly oxidised as soot or ash.

• Stored Carbon: Some of the fuel supplied to an economy is used as a raw material (or feedstock) for manufacture of products such as plastics, fertiliser, or in a non-energy use (e.g. bitumen for road construction, lubricants). In some cases, the carbon from the fuels is oxidised quickly to CO 2 . In other cases the carbon is stored (or sequestered) in the product, sometimes for as long as centuries. The amounts stored for long periods are called stored carbon and should be deducted from the carbon emissions calculation. Estimation of stored carbon requires data on fuel used as feedstock and/or quantities of non-energy fuel products produced. The calculations are discussed within each of the alternative approaches presented in this section.

• Bunker Fuels: The IPCC methodology subtracts the quantities delivered to and consumed by ships or aircraft for international transport from the fuel supply to the country. In this manner, the CO 2 emissions arising from the use of international bunkers

reasons for this double counting are discussed in the Overview of the IPCC Guidelines, General Notes on the Guidelines.

## E NERGY

1.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual are not included in the national total. To simplify the preparation of global estimates, these emissions should be brought together in a separate table.

• Biomass Fuels: Biomass fuels are included in the national energy and emissions accounts for completeness. These emissions should not be included in national CO 2 emissions from fuel combustion. If energy use, or any other factor, is causing a long term decline in the total carbon embodied in standing biomass (e.g. forests), this net release of carbon should be evident in the calculation of CO 2 emissions described in the Land Use Change and Forestry chapter. All of the above issues are addressed within the methods presented in the remainder of this section.
Approaches For Estimating CO 2 Emissions The estimation process can be divided into six steps that lead to figures for CO 2 emissions from fuel combustion. 1 Estimate consumption of fuels by fuel/product type. 2 Convert the fuel data to a common energy unit (TJ), if necessary.
3 Select carbon emission factors for each fuel/product type and estimate the total carbon content of the fuels. 4 Estimate the amount of carbon stored in products for long periods of time. 5 Account for carbon not oxidised during combustion. 6 Convert emissions of carbon to full molecular weight of CO 2 .



### 1.4.1.1 IPCC R EFERENCE 

### A PPROACH

Estimate Fuel Consumption The first step of the IPCC Reference Approach is to estimate apparent consumption of fuels within the country. This requires a balance of primary fuels produced, plus imports, minus exports, minus international bunkers and minus net changes in stocks. In this way carbon is brought into the country from energy production and imports (adjusted for stock changes) and moved out of the country through exports and international bunkers. In order to avoid double counting it is important to distinguish between primary fuels, which are fuels found in nature such as coal, crude oil and natural gas, and secondary fuels or fuel products, such as gasoline and lubricants, which are derived from primary fuels. To calculate the supply of fuels to the country, the following data are required for each fuel and inventory year:

• the amounts of primary fuels produced (production of secondary fuels and fuel products is excluded);

• the amounts of primary and secondary fuels and fuel products imported;

• the amounts of primary and secondary fuels and fuel products exported;

• the amounts of primary and secondary fuels used in international bunkers;

• the net increases or decreases in stocks of fuels.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.11 The apparent consumption of primary fuels is, therefore, calculated from the above data

as:
Apparent Consumption = Production + Imports - Exports - International Bunkers - Stock Change.
An increase in stocks is a positive stock change which withdraws supply from consumption. A stock reduction is a negative stock change which, when subtracted in the equation, causes an increase in apparent consumption. Apparent consumption of secondary fuels should be added to primary apparent consumption. The production (or manufacture) of secondary fuels should be ignored in the calculations because the carbon in these fuels will already have been included in the supply of primary fuels from which they were derived; for instance, the estimate for apparent consumption of crude oil already contains the carbon from which gasoline would be refined. Apparent consumption of secondary fuels is calculated as follows:
Apparent Consumption = Imports - Exports - International Bunkers - Stock Change.
Note that this calculation can result in negative numbers for apparent consumption. This is a perfectly acceptable result for the purposes of this calculation since it indicates a net export or stock increase in the country

. Since carbon content typically varies by fuel type, data should be reported for detailed categories of fuel and product types as shown in Table 1-1. The table also illustrates the inputs and calculations recommended for the IPCC Reference Approach.

## E NERGY

1.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-1 IPCC R EFERENCE A PPROACH E NTRIES AND C ALCULATIONS FOR S TEPS (1) AND (2) (1) (2) (3) (4) (5) (6) (7) (8)

Fuel Production Imports Exports International Bunkers Stock Change Apparent Consumption (a) Conversion Factor Apparent Consumption (TJ) A) Liquid Fossil sum (b) sum Primary Fuels 1) Crude Oil input input input NA input calc input calc 2) Orimulsion input input input NA input calc input calc 3) N. Gas Liquids input input input NA input calc input calc Secondary Fuels / Products 4) Gasoline NA input input input input calc input calc 5) Jet Kerosene NA input input input input calc input calc 6) Other Kerosene NA input input NA input calc input calc 7) Shale Oil NA input input NA input calc input calc 8) Gas / Diesel Oil NA input input input input calc input calc 9) Residual Fuel Oil NA input input input input calc input calc 10) LPG NA input input NA input calc input calc 11) Ethane NA input input NA input calc input calc 12) Naphtha NA input input NA input calc input calc 13) Bitumen NA input input NA input calc input calc 14) Lubricants NA input input input input calc input calc 15) Petroleum Coke NA input input NA input calc input calc 16) Refinery Feedstocks NA input input NA input calc input calc 17) Other Oil NA input input NA input calc input calc B) Solid Fossil sum sum Primary Fuels 18) Anthracite (c) input input input NA input calc input calc 19) Coking Coal input input input NA input calc input (d) calc 20) Other Bit. Coal input input input input input calc input (d) calc 21) Sub-bit. Coal input input input input input calc input (d) calc 22) Lignite input input input NA input calc input (d) calc 23) Oil Shale input input input NA input calc input calc 24) Peat input input input NA input calc input calc Secondary Fuels 25) BKB & Patent Fuel NA input input NA input calc input calc 26) Coke Oven/Gas Coke NA input input NA input calc input calc C) Gaseous Fossil sum sum 27) Natural Gas (Dry) input input input NA input calc input calc
Total (e) sum sum Information Entries Biomass Total sum sum 28) Solid Biomass input input input NA input calc input calc 29) Liquid Biomass input input input NA input calc input calc 30) Gas Biomass input input input NA input calc input calc

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.13 T ABLE 1-1 ( CONTINUED ) IPCC R EFERENCE A PPROACH E NTRIES AND C ALCULATIONS FOR S TEPS (3) TO (6) (8) (9) (10) (11) (12) (13) (14)

Fuel Apparent Consumption (TJ) Carbon Emission Factor (f) (t C/TJ) Carbon Content (Gg C) Carbon Stored (Gg C) Net Carbon Emissions

(Gg C) Actual Carbon Emissions

(Gg C) Actual CO 2 Emissions (Gg CO 2 )

A) Liquid Fossil sum sum sum sum sum sum Primary Fuels 1) Crude Oil calc 20.0 calc calc calc calc 2) Orimulsion calc 22.0 calc calc calc calc 3) N. Gas Liquids calc 17.2 calc calc calc calc Secondary Fuels / Products 4) Gasoline calc 18.9 calc calc calc calc 5) Jet Kerosene calc 19.5 calc calc calc calc 6) Other Kerosene calc 19.6 calc calc calc calc 7) Shale Oil calc 20.0 calc calc calc calc 8) Gas / Diesel Oil calc 20.2 calc Table 1-5 calc calc calc 9) Residual Fuel Oil calc 21.1 calc calc calc calc 10) LPG calc 17.2 calc Table 1-5 calc calc calc 11) Ethane calc 16.8 calc Table 1-5 calc calc calc 12) Naphtha calc (20.0) calc Table 1-5 calc calc calc 13) Bitumen calc 22.0 calc Table 1-5 calc calc calc 14) Lubricants calc (20.0) calc Table 1-5 calc calc calc 15) Petroleum Coke calc 27.5 calc calc calc calc 16) Refinery Feedstocks calc (20.0) calc calc calc calc 17) Other Oil calc (20.0) calc calc calc calc B) Solid Fossil sum sum sum sum sum sum Primary Fuels 18) Anthracite (c) calc 26.8 calc calc calc calc 19) Coking Coal calc 25.8 calc Table 1-5 calc calc calc 20) Other Bit. Coal calc 25.8 calc calc calc calc 21) Sub-bit. Coal calc 26.2 calc calc calc calc 22) Lignite calc 27.6 calc calc calc calc 23) Oil Shale calc 29.1 calc calc calc calc 24) Peat calc 28.9 calc calc calc calc Secondary Fuels 25) BKB & Patent Fuel calc (25.8) calc calc calc calc 26) Coke Oven/Gas Coke calc 29.5 calc calc calc calc C) Gaseous Fossil sum sum sum sum sum sum 27) Natural Gas (Dry) calc 15.3 calc Table 1-5 calc calc calc
Total (e) sum sum sum sum sum sum Information Entries Biomass Total sum sum sum sum sum 28) Solid Biomass calc 29.9 calc calc calc calc 29) Liquid Biomass calc (20.0) calc calc calc calc 30) Gas Biomass calc (30.6) (g) calc calc calc calc

## E NERGY

1.14 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-1 ( CONTINUED ) IPCC R EFERENCE A PPROACH E MISSIONS FROM I NTERNATIONAL B UNKERS (I NTERNATIONAL M ARINE AND A IR T RANSPORT ) (h)
(15) (16) (17) (18) (19) (20)

Fuel Quantities delivered (i) Conversion Factor (TJ/units) Quantities Delivered

(TJ) Carbon Emission Factor (t C/TJ) Carbon Content

(t C) Carbon Content
(Gg C) A) Solid Fossil Primary Fuels 1) Other Bituminous Coal input input calc 25.8 calc calc 2) Sub-Bituminous Coal input input calc 26.2 calc calc Liquid Fossil Secondary Fuels 3) Gasoline input input calc 18.9 calc calc 4) Jet Kerosene input input calc 19.5 calc calc 5) Gas / Diesel Oil input input calc 20.2 calc calc 6) Residual Fuel Oil input input calc 21.1 calc calc 7) Lubricants input input calc (20.0) calc calc
Total sum

T ABLE 1-1 ( CONTINUED ) IPCC R EFERENCE A PPROACH E MISSIONS FROM I NTERNATIONAL B UNKERS (I NTERNATIONAL M ARINE AND A IR T RANSPORT ) (21) (22) (23) (24) (25)

Fuel Fraction of Carbon Stored Carbon Stored (Gg C) Net Carbon Emissions Actual Carbon Emissions

(Gg C) Actual CO 2 Emissions (Gg CO 2 ) A) Solid Fossil Primary Fuels 1) Other Bituminous Coal NA calc calc calc calc 2) Sub-Bituminous Coal NA calc calc calc calc Liquid Fossil Secondary Fuels 3) Gasoline NA calc calc calc calc 4) Jet Kerosene NA calc calc calc calc 5) Gas / Diesel Oil NA calc calc calc calc 6) Residual Fuel Oil NA calc calc calc calc 7) Lubricants 0.5 calc calc calc calc
Total sum

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.15 T ABLE 1-1 (C ONTINUED )

E XPLANATORY N OTES
calc = value to be calculated, NA = not applicable (a) Apparent Consumption = Production + Imports - Exports - International Bunkers - Stock Changes. A stock build is positive; a stock draw is negative. (b) Apparent Consumption for the aggregate categories of Liquid Fossil, Solid Fossil, Gaseous Fossil, and Biomass Fuels equal the sum of Apparent Consumption over the fuel types within the appropriate categories. (c) If anthracite is not separately identifiable, include it with Other Bituminous Coal. (d) If data are in 10 3 t, separate conversion factors are available for Production, Imports and Exports in Table 1-2. Each of these entries should be multiplied by the appropriate conversion factor. Then, the results should be summed to find Apparent Consumption in TJ (Column 8). (e) Total should include Liquid, Solid, and Gaseous Fossil Fuel subtotals only. Biomass subtotals are for reference purposes only and should not be included in the totals. (f) If value is in parenthesis it is a default value until a fuel-specific CEF is determined. (g) Based on the assumption that 50 per cent of the carbon in the biomass is converted to methane. (h) The bunker emissions are not to be added to national totals. (i) See Column 4, “International Bunkers”.

_________________________________________________________________________

Convert Fuel Data to a Common Energy Unit (if necessary)
In the OECD/IEA Energy Statistics , and other energy data compilations, production and consumption of solid and liquid fuels are specified in 10 3 tonnes. To convert tonnes to terajoules, net calorific values (NCV) must be applied. The values to convert from 10 3 tonnes to terajoules are in Table 1-2. In some cases, particularly for coal, different NCVs are given for production, imports and exports in a given country and are used to convert each category separately when calculating apparent consumption. For international bunkers and stock changes national experts can use a weighted average of the different NCVs, or use the one for the coal type which meets the largest share of total apparent consumption. For refined products the NCVs from 10 3 tonnes to terajoules do not normally vary greatly by country and global default values are provided in Table 1-3. 9 National experts may use more detailed locally available NCVs. In this case, the values used should also be reported and documented. If original data are expressed in other energy units such as British thermal units (Btu's) or million tons of oil equivalent (Mtoe), they should be converted to terajoules using standard conversion factors. If energy data are already available in terajoules on a net calorific value basis, no conversion is necessary and Column 7 of Table 1-1 can be ignored.

9 Throughout the Guidelines net calorific values are used and expressed in SI units or multiples of SI units (for example TJ/kt). The term Conversion Factor has two uses. First, as net calorific value, to convert quantities expressed in natural units to energy units, and second as a scaling factor to convert one form of energy unit to another (e.g., Btu’s to GJ).

## E NERGY

1.16 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-2 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR S ELECTED N ON -OECD C OUNTRIES (Terajoule per kilotonne)
Albania Algeria Angola Cabinda Argentina Armenia Azerbaijan Bahrain Bangladesh Belarussia Benin Bo livia

OIL
Crude Oil 41.45 43.29 42.75 42.29 - 42.08 42.71 42.16 42.08 42.58 43.33
NGL - 43.29 - 42.50 - - 42.71 42.71 - - 43.33
COAL
Hard Coal
Production - 25.75 - 24.70 -

------ Imports 27.21 25.75 - 30.14 18.58 18.58 - 20.93 25.54 - - Exports - - - 24.70 18.58 18.58 - - 25.54 - - Lignite and Sub-Bituminous Coal
Production 9.84

---------- Imports - - - - 14.65 14.65 - - 14.65 - - Exports 9.84 - - - 14.65 14.65 - - 14.65 - -
Coal Products
Patent Fuel/BKB - - - - 29.31 29.31 - - 29.31 - -
Coke Oven/Gas Coke 27.21 27.21 - 28.46 25.12 25.12 - - 25.12 - -Brazil Brunei Bulgaria Cameroon Chile China Colombia Congo Cuba Cyprus Czech Republic
OIL
Crude Oil 42.54 42.75 42.62 42.45 42.91 42.62 42.24 42.91 41.16 42.48 41.78
NGL 45.22 42.75 - - 42.87 - 41.87

---- COAL
Hard Coal
Production 18.42 - 24.70 - 28.43 20.52 27.21 - - - 24.40 Imports 30.56 - 24.70 - 28.43 20.52 - - 25.75 25.75 23.92 Exports -

---- 20.52 27.21 - - - 27.98 Lignite and Sub-Bituminous Coal
Production - - 7.03 - 17.17 - - - - - 12.26 Imports -

---------- Exports -

--------- 15.26
Coal Products
Patent Fuel/BKB - - 20.10

------- 21.28
Coke Oven/Gas Coke 28.30 - 27.21 - 28.43 28.47 20.10 - 27.21 - 27.01 Note: A few of these countries have become OECD members subsequent to the production of this table. Crude oil conversion factors are based on weighted average production data. The conversion factors are those used by the IEA in the construction of energy balances. Source: OECD/IEA, 1993b.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.17 T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR S ELECTED N ON -OECD C OUNTRIES (Terajoule per kilotonne)Ecuador Egypt Estonia Ethiopia Gabon Georgia Ghana Guatemala Hong Kong Hungary India

OIL
Crude Oil 42.45 42.54 - 42.62 42.62 42.08 42.62 42.45 - 40.36 42.79
NGL 42.45 42.54 - - - - - - - 45.18 43.00
COAL
Hard Coal
Production - - - - - 18.58 - - - 16.42 19.98 Imports - 25.75 18.58 - - 18.58 25.75 - 25.75 26.33 25.75 Exports - - 18.58 - - 18.58 - - - 24.15 19.98 Lignite and Sub-Bituminous Coal
Production - - 14.65 - - - - - - 10.55 9.80 Imports - - 14.65 - - 14.65 - - - 9.91 - Exports - - 14.65 - - 14.65 - - - - -
Coal Products
Patent Fuel/BKB - - 20.10 - - 29.31 - - - 21.44 20.10
Coke Oven/Gas Coke - 27.21 25.12 - - 25.12 - - 27.21 30.11 - Indonesia Iran Iraq Israel Ivory Coast Jamaica Jordan Kazakhstan Kenya Kuwait Kyrgyzstan
OIL
Crude Oil 42.66 42.66 42.83 42.54 42.62 42.16 42.58 42.08 42.08 42.54 42.08
NGL 42.77 42.54 42.83 - - - - - - 42.62 -
COAL
Hard Coal
Production 25.75 25.75 - - - - - 18.58 - - 18.58 Imports 25.75 25.75 - 26.63 - 25.75 - 18.58 25.75 - 18.58 Exports 25.75 - - - - - - 18.58 - - 18.58 Lignite and Sub-Bituminous Coal
Production - - - - - - - 14.65 - - 14.65 Imports - - - - - - - 14.65 - - 14.65 Exports - - - - - - - 14.65 - - 14.65
Coal Products
Patent Fuel/BKB - - - - - - - 29.31 - - 29.31
Coke Oven/Gas Coke 27.21 - - - - - - 25.12 - - 25.12
Note: A few of these countries have become OECD members subsequent to the production of this table. Crude oil NCVs are based on weighted average production data. The NCVs are those used by the IEA in the construction of energy balances. Source: OECD/IEA, 1993b.

## E NERGY

1.18 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR S ELECTED N ON -OECD C OUNTRIES (Terajoule per kilotonne)
Latvia Lebanon Libya Lithuania Malaysia Malta Mexico Moldova Morocco Mozambique Myanmar OIL
Crude Oil - 42.16 43.00 42.08 42.71 - 42.35 - 43.00 - 42.24
NGL - - - - 43.12 - 46.81 - - - 42.71
COAL
Hard Coal
Production - - - - 25.75 - 24.72 - 23.45 25.75 25.75 Imports 18.58 - - 18.59 25.75 25.75 30.18 18.58 27.63 25.75 25.75 Exports 18.58 - - 18.59 25.75 - 22.41 18.58 - -

- Lignite and Sub-Bituminous Coal
Production - - - - - - - - - - 8.37 Imports 14.65 - - 14.65 - - - 14.65 - -

- Exports 14.65 - - 14.65 - - - 14.65 - -

- Coal Products
Patent Fuel/BKB 29.31 - - 29.31 - - - 29.31 - -

- Coke Oven/Gas Coke 25.12 - - 25.12 27.21 - 27.96 25.12 27.21 - 27.21 Nepal Neth. Antilles Neutral Zone Nigeria North Korea Oman Pakistan Panama Paraguay Peru Philippines
OIL
Crude Oil - 42.16 42.12 42.75 42.16 42.71 42.87 42.16 42.54 42.75 42.58
NGL - - - - - - - - - 42.75

- COAL
Hard Coal
Production - - - 25.75 25.75 - 18.73 - - 29.31 20.10 Imports 25.12 - - - 25.75 - 27.54 25.75 - 29.31 20.52 Exports - - - 25.75 25.75 - - - - -

- Lignite and Sub-Bituminous Coal
Production - - - - 17.58 - - - - - 8.37 Imports - - - - - - - - - -

- Exports - - - - - - - - - -

- Coal Products
Patent Fuel/BKB - - - - - - - - - -

- Coke Oven/Gas Coke - - - 27.21 27.21 - - - - 27.21 27.21 Note: A few of these countries have become OECD members subsequent to the production of this table. Crude oil NCVs are based on weighted average production data. The NCVs are those used by the IEA in the construction of energy balances. Source: OECD/IEA, 1993b.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.19 T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR S ELECTED N ON -OECD C OUNTRIES (Terajoule per kilotonne) Poland Qatar Romania Russia Saudi Arabia Senegal Singapore South Africa South Korea Slovak Republic Sri Lanka

OIL
Crude Oil 41.27 42.87 40.65 42.08 42.54 42.62 42.71 44.13 42.71 41.78 42.16
NGL - 43.00 - - 42.62 - - - - - -
COAL
Hard Coal
Production 22.95 - 16.33 18.58 - - - 25.09 19.26 - - Imports 29.41 - 25.12 18.58 - - - - 27.21 23.92 25.75 Exports 25.09 - - 18.58 - - - 25.09 - - - Lignite and Sub-Bituminous Coal
Production 8.36 - 7.24 14.65 - - - - - 12.26 - Imports - - 7.24 14.65 - - - - - - - Exports 9.00 - - 14.65 - - - - - 15.26 -
Coal Products
Patent Fuel/BKB 20.93 - 14.65 29.31 - - - - - 21.28 -
Coke Oven/Gas Coke 27.76 - 20.81 25.12 - - 27.21 - - 27.01 - Sudan Syria Chinese Taipei Tajikistan Tanzania Thailand Trinidad / Tobago Tunisia Turkmenistan Ukraine Utd ArabEmirates
OIL
Crude Oil 42.62 42.04 41.41 42.08 42.62 42.62 42.24 43.12 42.08 42.08 42.62
NGL - - - - - 46.85 - 43.12 - - -
COAL
Hard Coal
Production - - 25.96 18.58 25.75 - - - - 21.59 - Imports - - 27.42 18.58 - 26.38 - 25.75 18.58 25.54 - Exports - - - 18.58 - - - - 18.58 21.59 - Lignite and Sub-Bituminous Coal
Production - - - - - 12.14 - - - 14.65 - Imports - - - 14.65 - - - - 14.65 14.65 - Exports - - - 14.65 - - - - 14.65 14.65 -
Coal Products
Patent Fuel/BKB - - - 29.31 - - - - 29.31 29.31 -
Coke Oven/Gas Coke - - - 25.12 27.21 27.21 - 27.21 25.12 25.12 - Note: A few of these countries have become OECD members subsequent to the production of this table. Crude NCVs are based on weighted average production data. The NCVs are those used by the IEA in the construction of energy balances. Source: OECD/IEA, 1993b.

## E NERGY

1.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR S ELECTED N ON -OECD C OUNTRIES (Terajoule per kilotonne)Uruguay Uzbekistan Venezuela Viet Nam Yemen FormerYugoslavia Zaire Zambia Zimbabwe

OIL
Crude Oil 42.71 42.08 42.06 42.61 43.00 42.75 42.16 42.16 -
NGL - - 41.99 - - - - - -
COAL
Hard Coal
Production - 18.58 25.75 20.91 - 23.55 25.23 24.71 25.75 Imports - 18.58 - - - 30.69 25.23 - 25.75 Exports - 18.58 25.75 20.91 - - - 24.71 25.75 Lignite and Sub-Bituminous Coal
Production - - - - - 8.89 - - - Imports - 14.65 - - - 16.91 - - - Exports - 14.65 - - - 16.90 - - -
Coal Products
Patent Fuel/BKB - 29.31 - - - 20.10 29.31 - -
Coke Oven/Gas Coke - 25.12 27.21 27.21 - 26.90 27.21 - 27.21 Note: A few of these countries have become OECD members subsequent to the production of this table. Crude oil NCVs are based on weighted average production data. The NCVs are those used by the IEA in the construction of energy balances. Source: OECD/IEA, 1993b.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.21 T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR OECD C OUNTRIES (Terajoule per kilotonne)
Aust ralia Austria Belgium Canada Denmark Finland France Ger many Greece Iceland Ireland Italy

OIL
Crude Oil 43.21 42.75 42.75 42.79 42.71 42.66 42.75 42.75 42.75 - 42.83 42.75
NGL 45.22 45.22 - 45.22 - - 45.22

- 45.22 - - 45.22 Refinery Feedst. 42.50 42.50 42.50 42.50 42.50 42.50 42.50 42.50 42.50 - 42.50 42.50
COAL Coking Coal
Production 28.34 - - 28.78 - - 28.91 28.96

---- Imports - 28.00 29.31 27.55 - 34.33 30.50 28.96 - 27.44 29.10 30.97 Exports 28.21 - - 28.78 - - - 28.96

---- Other Bituminous Coal and Anthracite (a)

Production 24.39 - 25.00 28.78 - - 26.71 24.96 - - 26.13 26.16 Imports - 28.00 25.00 27.55 26.09 26.38 25.52 26.52 27.21 25.85 29.98 26.16 Exports 25.65 - 25.00 28.78 26.09 - 26.43 31.71 - - 26.13 -
Sub-Bituminous Coal
Production 17.87 - 18.06 17.38 - - -

- ---- Imports - - - - - - -

- ---- Exports - - 18.20 - - - -

- ---- Lignite
Production 9.31 10.90 - 14.25 - - 17.94 8.41 5.74 - - 10.47 Imports - 10.90 21.56 - - - 17.94 14.88 - - 19.82 10.47 Exports - 10.90 - 14.25 - - - 8.40

---- Coal Products
Patent Fuel/BKB 21.00 19.30 23.81 - 18.27 - 28.80 20.64 15.28 - 20.98 -
Coke Oven/Gas Coke 25.65 28.20 29.31 27.39 31.84 28.89 28.71 28.65 29.30 26.65 32.66 29.30 (a) In IEA statistics Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination. The NCVs for oil and coal are those used by the IEA in the construction of energy balances. The NCVs for coal product groupings listed are calculated from the values of their constituents. Source: OECD/IEA, 1993a.

## E NERGY

1.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-2 ( CONTINUED ) 1990 C OUNTRY -S PECIFIC N ET C ALORIFIC V ALUES FOR OECD C OUNTRIES (Terajoule per kilotonne)Japan Luxembourg Netherlands NZ Norway Portugal Spain Sweden Switzer -land Turkey UK USA

OIL
Crude Oil 42.62 - 42.71 43.12 42.96 42.71 42.66 42.75 42.96 42.79 42.83 42.71
NGL 46.05 - 45.22 46.05 45.22 - 45.22 - - - 46.89 45.22 Refinery Feedst. 42.50 - 42.50 44.80 42.50 42.50 42.50 42.50 42.50 42.50 42.50 42.50
COAL Coking Coal
Production 30.63 - - 28.00 - - 29.16 - - 33.49 29.27 29.68 Imports 30.23 - 29.30 28.00 - 29.30 30.14 30.00 - 33.49 30.07 - Exports - - - 28.00 - - - - - - 29.27 29.68
Other Bituminous Coal and Anthracite (a)

Production 23.07 - - 26.00 28.10 - 21.07 14.24 - 29.30 24.11 26.66 Imports 24.66 29.30 29.30 - 28.10 26.59 25.54 26.98 28.05 27.21 26.31 27.69 Exports - - 29.30 - 28.10 - 23.00 26.98 28.05 - 27.53 28.09
Sub -Bituminous Coal
Production - - - 21.30 - 17.16 11.35 - - - - 19.43 Imports - - - - - - 11.35 - - - - - Exports

- - - - - - -- ---- Lignite
Production - - - 14.10 - - 7.84 - - 9.63 - 14.19 Imports - 20.03 20.00 - - - - 8.37 - 12.56 - - Exports - - 20.00 - - - - - - - - 14.19
Coal Products
Patent Fuel/BKB 27.05 20.10 23.53 - - - 20.31 20.10 21.76 20.93 26.26 -
Coke Oven/Gas Coke 28.64 28.50 28.50 - 28.50 28.05 30.14 28.05 28.05 29.28 26.54 27.47 (a) In IEA statistics Anthracite is combined with Other Bituminous Coal

– the NCVs given above reflect this combination. The NCVs for oil and coal are those used by the IEA in the construction of energy balances. The NCVs for coal product groupings listed are calculated from the values of their constituents. Source: OECD/IEA, 1993a.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.23 T ABLE 1-3 N ET C ALORIFIC V ALUES FOR O THER F UELS (TJ/10 3 tonnes)
Refined Petroleum Products Gasoline (aviation and auto) 44.80 Jet Kerosene 44.59
Other Kerosene 44.75
Shale Oil 36.00
Gas/Diesel Oil 43.33
Residual Fuel Oil 40.19
LPG 47.31
Ethane 47.49 Naphtha 45.01
Bitumen 40.19
Lubricants 40.19
Petroleum Coke 31.00 Refinery Feedstocks 44.80 Refinery Gas 48.15
Other Oil Products 40.19
Other Products
Coal Oils and Tars derived from Coking Coal 28.00
Oil Shale 9.40
Orimulsion 27.50 Source: OECD/IEA, Paris, 1996a.

Select Carbon Emission Factors and Estimate Carbon Content Carbon emission factors may vary considerably both among and within primary fuel types:

• For natural gas, the carbon emission factor depends on the composition of the gas which, in its delivered state, is primarily methane, but can include small quantities of ethane, propane, butane, and heavier hydrocarbons. Natural gas flared at the production site will usually be "wet", i.e., containing far larger amounts of nonmethane hydrocarbons. The carbon emission factor will be correspondingly different.

• Carbon content per unit of energy is usually less for light refined products such as gasoline than for heavier products such as residual fuel oil.

• For coal, carbon emissions per tonne vary considerably depending on the coal's composition of carbon, hydrogen, sulphur, ash, oxygen, and nitrogen.
Estimates of carbon emission factors for fuels from several studies are summarised in Table 1-4.

## E NERGY

1.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-4 C ARBON E MISSION FACTORS FOR F UELS FROM D IFFERENT S TUDIES (t C/terajoule, net calorific value basis) (a)

Study Anthracite Bit. Coal Sub-Bit. Coal Lignite Peat

Marland & Rotty (1984) 25.5 (a)
Marland & Pippin (1990) 25.4 (a)
Grubb (1989) 26.8 (a) 25.8 (a) 27.6 (a) 28.9 (a)
OECD (1991) 25.8 (a,b)
Study Crude Oil Gaso line Kero sene Gas/Diesel Oil Fuel Oil Natural Gas Marland & Rotty (1984) 21.0 (a) 15.2 (a)
Marland & Pippin (1990) 21.0 (a) 19.4 (a) 19.4 (a) 19.9 (a) 21.1 (a,c) 15.3 (a)
Grubb (1989) 20.0 (a) 18.9 (a) 19.5 (a) 20.0 (a) 21.1 (a) 15.3 (a)
OECD (1991) 20.0 15.3 (a) Values were originally based on gross calorific value; they were converted to net calorific value by assuming a 5% difference in calorific value for coal and oil, and 10% for natural gas. These percentage adjustments are the IEA assumptions on how to convert from gross to net calorific values. (b) Average value for all coal: sub-bituminous through anthracite. (c) Midpoint of range from 20.7 for light fuel oil (#4 fuel oil) to 21.6 for residual fuel oil (#6 fuel oil).

One approach for estimating the carbon emission factors was presented by Marland and Rotty (1984). For natural gas, the carbon emission factor was based on the actual composition of dry natural gas. They sampled the composition of natural gas from 19 countries and then calculated a weighted average global gas composition, breaking the gas out into methane, ethane, propane, other hydrocarbons, CO 2 and other gases. The composition of the gas then determined both the calorific values of the gas and the carbon content. The carbon emission factor of the gas (t C/terajoule, using gross calorific values) was expressed using the following relationship:

C g = 13.708 + (0.0828 x 10 -3 ) x (H v - 37 234)

where C g is the carbon emission factor of the gas in t C/terajoule (TJ) and H v is the calorific value of the gas (gross calorific value, see OECD/IEA, 1996a) in kJ/cubic metre

. The coefficients of the equation (13.708, 0.0828 x 10 -3 , and 37 234) were estimated using regression analysis based on data from the 19 countries

. The carbon content of oil was assumed to be a function of the API gravity: using an estimate of world average API gravity of 32.5 o + 2 o , they estimated a composition of 85 + 1 per cent carbon

. Converting this to units of carbon per terajoule yielded an estimate of 21.0 t C/TJ on a net calorific value basis (assuming 42.62 terajoules per kilotonne, gross calorific value, as reported in Marland & Rotty, 1984)

. For coal, the literature suggested that the carbon content of coal was predominantly a function of the energy content (calorific value) and that the carbon content on a per tonne coal-equivalent basis was around 74.6 + 2 per cent (Marland and Rotty 1984)

. The carbon emission factor was estimated to be 25.5 t C/TJ. The approach used by Grubb (1989) to estimate carbon emission factors is very similar but based on more recent research

. All carbon emission factors were originally reported on a gross calorific value basis, but are converted here to a net calorific value basis

. He provides carbon factors for methane, ethane, propane, and butane and using data from

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.25 Marland and Rotty (1984), estimates an average emission factor for natural gas of 15.3 t C/TJ + 1 per cent

. For oil and some refined petroleum products the estimates are based on data from the literature, as summarised in Table 1-4

. The carbon emission factor of coal, excluding anthracite, was defined as:

C c = 32.15 - (0.234 x H v )

where C c is the carbon emission factor in t C/TJ and H v is the gross calorific value of the coal when the calorific value is from 31 to 37 TJ/kilotonne on a dry mineral matter free (dmf) basis. Anthracites fall outside this range and a value of 26.8 t C/TJ is used. Since the publication of the original OECD Background Document (OECD 1991),additional information has been made available on carbon emission factors. At an IPCCsponsored workshop in October 1992 (IPCC/OECD, 1993), experts recommended several revised emission factors based on national inventory submissions to the OECD. Additional emission factors were also made available based on the work of the expert group on GHG Emissions from Fuel Combustion during Phase II of the IPCC/OECD/IEA Programme on National GHG Inventories in 1996. The IPCC Reference Approach relies primarily on the emission factors from Grubb (1989), with additions from other studies as discussed above, to estimate total carbon
content

. The suggested carbon emission factors are listed in Table 1-1

. The basic formula for estimating total carbon content is:
Total Carbon Content (Gg C) = ∑

Apparent Energy Consumption (by fuel type in TJ) x Carbon emission factor (by fuel type in t C/TJ) x 10 -3
Apparent consumption of the fuels is estimated in Table 1-1 (Column 6)

. The carbon emission factors for the fuels are average values based on net calorific value

. This approach has been recommended by the IPCC because it explicitly treats each major fuel type differently according to its carbon emission factor. When countries use local values for the carbon emission factors they should note the differences from the default values and provide documentation supporting the values used in the national inventory calculations.

Estimate Carbon Stored in Products The next step is to estimate the amount of fossil fuel carbon that is stored in non-energy products and the portion of this carbon expected to oxidise over a long time period (e.g., greater than 20 years). All fossil fuels are used for non-energy purposes to some degree

. Natural gas is used for ammonia production. LPGs are used for a number of purposes, including production of solvents and synthetic rubber. A wide variety of products is produced from oil refineries, including asphalt, naphthas and lubricants. Two by-products of the coking process, oils and tars, are used in the chemical industry. Not all non-energy uses of fossil fuels, however, result in storage of carbon. For example, the carbon from natural gas used in ammonia production is oxidised quickly. Many products from the chemical and refining industries are burned or decompose within a few years. Several approaches for estimating the portion of carbon stored in products are reviewed in Box 2.

## E NERGY

1.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual B OX 2 A PPROACHES FOR E STIMATING C ARBON S TORED IN P RODUCTS The approach used by Marland and Rotty (1984) relied on historical data for determining non-energy applications and varied depending on fossil fuel type. For natural gas they assume that close to 1/3 of the carbon used for non-energy purposes (equivalent to 1 per cent of total carbon from natural gas production) does not oxidise over long periods of time. For oil products they assume that some portion of LPG, ethane, naphthas, asphalt and lubricants does not oxidise quickly. Specifically, they assume that about 50 per cent of LPG and ethane from gas processing plants is sold for chemical and industrial uses and that 80 per cent of this amount, or 40 per cent of all LPG and ethane, goes into products that store the carbon. About 80 per cent of the carbon in naphthas is assumed to end up in products such as plastics, tires, and fabrics and oxidises slowly. All of the carbon in asphalt is assumed to remain unoxidised for long periods, while about 50 per cent of the carbon in lubricants is assumed to remained unoxidised. For coal they assume that on average 5.91 per cent of coal going to coke plants ends up as light oil and crude tar, with 75 per cent of the carbon in these products remaining unoxidised for long periods. Grubb (1989) basically uses the Marland and Rotty (1984) approach, but suggests several changes, including higher estimates of methane losses during production and transportation of natural gas to market and a wide range of estimates concerning the fraction of carbon in refinery products that remain unoxidised. He does use Marland and Rotty's estimate of the amount of carbon in coal that does not oxidise, but also quantifies the amount of carbon emissions from SO 2 scrubbing (in which CO 2 is released during the chemical interactions in the desulphurisation process) using the formula: (% sulphur by weight) x (coal consumption) x 12/32. Okken and Kram (1990) introduce the concept of actual and potential emissions of CO 2 where potential emissions are defined as carbon that is stored in products from non-energy uses or by-products from combustion and actual emissions as all carbon from fuels that are emitted immediately or within a short period of time. Actual emissions plus potential emissions equal total carbon in the fuels. They assume that carbon from the following non-energy uses of fossil fuels oxidises quickly: fertiliser production (ammonia), lubricants, detergents, volatile organic solvents, etc. Carbon from the following non-energy uses of fossil fuels remains stored for long periods of time (in some cases, hundreds of years): plastics, rubber, bitumen, formaldehyde, and silicon carbide.

For the IPCC Reference Approach, the suggested formula for estimating carbon stored in products for each country is:
Total Carbon Stored (Gg C) = Non-Energy Use (10 3 t) x Conversion Factor (TJ/10 3 t)

x Emission Factor (t C/TJ) x Fraction Carbon Stored x 10 -3

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.27 Most of the suggested categories conform to those used by Marland and Rotty (1984) and include naphthas, bitumen (asphalt), lubricants, LPG, and coal oils and tars. The data available from the UN reports (e.g., 1996) correspond to these categories, with the exception of coal oils and tars, which are not reported. The assumptions of 75 per cent for naphtha as a feedstock and 50 per cent for gas/diesel oil as a feedstock, used in Table 1-5 (Column 6) should be viewed as potential overestimates, since not all of the carbon from the intermediate products will be stored. For example, carbon emissions may occur due to losses in the production of final products or incineration of final products. At this time these percentages can be used as the upper bound when determining stored carbon. This suggested approach for estimating carbon stored in products is illustrated in Table 1-5. Whenever possible, countries should substitute assumptions that represent more accurately the practices within their own countries and provide documentation for these assumptions. The resulting estimates from Table 1-5 (Column 7) should be subtracted from carbon content of apparent consumption to determine net carbon emissions that could be oxidised. This calculation is done by entering the values from Table 1-5 (Column 7) for the relevant fuels/products into Table 1-1 (Column 11). In Table 1-1, carbon stored in products is subtracted from total carbon in the fuels (“carbon content”) to get net carbon available for emission (“net carbon emissions”). Currently the fraction of carbon stored applied to the carbon content of the fuels used for product manufacture takes into account the release of carbon from the use or destruction of the products in the short term. The fraction is therefore lower than the fraction of carbon entering the products (see Box 2). The emissions resulting from the use or destruction of the products may occur in:

• industrial processes – both the production of non-fuel products from energy feedstocks, and the emissions from use of these products in industrial processes (e.g., oxidation of anodes made from petroleum coke which occurs during aluminium production);

• other end uses of products (e.g., lubricants oxidised in transportation);

• waste disposal – particularly incineration of plastics and other fossil fuel based products.

## E NERGY

1.28 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-5 E STIMATION OF C ARBON S TORED IN P RODUCTS
1
Estimated Fuel Quantities (a) 2
Conversion

Factor 3
Estimated

Fuel Quantities (b) 4
Emission Factor 5
Carbon Content (c) 6
Fraction Carbon Stored 7
Carbon Stored (d)

Product/Fuel (e) (Original Units) TJ/Units (TJ) (t C/TJ) (Gg C) (Gg C)
Lubricants calc Table 1-3 calc Table 1-1 calc 0.50 calc
Bitumen calc Table 1-3 calc Table 1-1 calc 1.0 calc
Coal Oils and Tars from Coking Coal calc (f) Table 1-3 calc Table 1-1 (g) calc 0.75 calc

Naphtha as Feedstock calc Table 1-3 calc Table 1-1 calc 0.75 calc
Gas/Diesel Oil as Feedstock calc Table 1-3 calc Table 1-1 calc 0.50 calc
Natural Gas as Feedstock calc Table 1-3 calc Table 1-1 calc 0.33 calc
LPG as Feedstock calc Table 1-3 calc Table 1-1 calc 0.80 calc
Ethane as Feedstock calc Table 1-3 calc Table 1-1 calc 0.80 calc (a) Either Apparent Consumption plus domestic (manufactured) production, or Feedstock Use. (b) Estimated Fuel Quantities in TJ (Col. 3) equals Estimated Fuel Quantities (Col. 1) times a Conversion Factor (Col. 2). (c) Carbon Content (Col. 5) equals Estimated Fuel Quantities in TJ (Col. 3) times an Emission Factor (Col. 4). (d) Carbon Stored (Col. 7) equals Carbon Content (Col. 5) times Fraction Carbon Stored (Col. 6) divided by 10 3

. (e) This is an incomplete list of products/fuels which account for the majority of carbon stored. Where data are available for other fuels, the estimation of stored carbon is strongly encouraged. (f) Use 6% of apparent consumption of Coking Coal. (g) Use the emission factor for coking coal (25.8 t C/TJ).

Estimate Carbon Unoxidised During Fuel Use A small part of the fuel carbon entering combustion escapes oxidation but the majority of this carbon is later oxidised in the atmosphere. It is assumed that the carbon that remains unoxidised is stored indefinitely. Based on work by Marland and Rotty (1984), since 1991 the IPCC has been recommending that 1 per cent of the carbon in fossil fuels would remain unoxidised. This assumption was based on the following findings from Marland and Rotty for the amount unoxidised:

• For natural gas, less than 1 per cent of the carbon is unoxidised during combustion and remains as soot in the burner, stack, or in the environment.

• For oil 1.5% ±1% passes through the burners and is deposited in the environment without being oxidised. This estimate is based on 1976 US statistics of emissions of hydrocarbons and total suspended particulates.

• For coal 1% ±1% of carbon supplied to furnaces is discharged unoxidised, primarily in the ash. However, several countries have commented that the amount of carbon remaining unoxidised is more variable than indicated by the 1 per cent assumption across all fuels. For example, it has been noted that the amount of unburnt carbon varies depending on several factors, including type of fuel consumed, type of combustion technology, age of the equipment, and operation and maintenance practices. Information submitted by the Coal Industry Advisory Board of the OECD (Summers 1993), provided the following observations for coal combustion technologies:

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.29 • Unoxidised carbon from electric power stations in Australia averaged about 1 per cent. Test results from stoker-fired industrial boilers, however, were higher, with unoxidised carbon amounting to 1 to 12 per cent of total carbon with coals containing from 8 to 23 per cent ash. As average values, 2 per cent carbon loss was suggested for best practices, 5 per cent carbon loss for average practices, and 10 per cent carbon loss for worst practices. In those cases when coal is used in the commercial or residential sectors, carbon losses would be on the order of 5 to 10 per cent (Summers, 1993).

• In related work British Coal has provided information on the percentage of unburnt carbon for different coal combustion technologies:
Pulverised Coal 1.6% Travelling Grate Stoker 2.7-5.4%
Underfeed Stoker 4.0-6.6% Domestic Open Fire 0.6-1.2%
Shallow Bed AFBC 10 Up to 4.0%
PFBC/CFBC 10 3.0%

• Evaluations at natural gas-fired boiler installations indicate that combustion efficiency is often 99.9 per cent at units reasonably well-maintained. It is clear from the available information that a single global default assumption of 1 per cent unoxidised carbon is not always accurate. While some additional information is available to refine the assumptions for this portion of the methodology, most of the new information requires some level of detail on the type of technology in which the fuel is combusted or information on which sector is consuming the fuel. The Reference Approach requires data only on the amount of fuels consumed in a country, not data by technology type or sector of the economy. As a result, based on the information available at this point, the default values presented in Table 1-6 are recommended for the percentage of carbon oxidised during combustion by fuel. It should be recognised that the value for coal is highly variable based on fuel quality and technology types. National experts are encouraged to vary this assumption if they have data on these factors, suggesting that different average values for their countries are appropriate. It is clear from the information available at this time that additional research should be conducted on this topic.

T ABLE 1-6 F RACTION OF C ARBON O XIDISED (R ECOMMENDED D EFAULT A SSUMPTIONS )
Coal (a) 0.98
Oil and Oil Products 0.99
Gas 0.995 Peat for electricity generation (b) 0.99 (a) This figure is a global average but varies for different types of

coal, and can be as low as 0.91. (b)The fraction for peat used in households may be much lower.

10 AFBC = Advanced Fluidised Bed Combustion CFBC = Circulating Fluidised Bed Combustion PFBC = Pressurised Fluidised Bed Combustion

## E NERGY

1.30 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Convert carbon emissions to full molecular weight CO 2 Net carbon emissions (Column 12 in Table 1-1) are then multiplied by the fraction of carbon oxidised to give actual carbon emissions (Column 13 of Table 1-1), and then summed across all fuel types, to determine the total amount of carbon oxidised from the combustion of fuel. To express the results as carbon dioxide (CO 2 ), total carbon oxidised should be multiplied by the molecular weight ratio of CO 2 to C, (44/12).



### 1.4.1.2 E MISSIONS 

### B Y 

### S OURCE 

### C ATEGORIES

A sectoral breakdown of national CO 2 emissions using the defined IPCC source categories is needed for monitoring and abatement policy discussions. The IPCC Reference Approach provides a rapid method to estimate the total CO 2 emissions from fuels supplied to the country but it does not break down the emissions by sector. The development of a Tier 1 method giving non-CO 2 GHG emissions by sector (Section 1.4.2) has been extended to CO 2 so that sectoral information can be obtained simply for this gas. However, the range of the carbon emission factors for fuels and the special consideration given to CO 2 emissions from biofuels mean that the calculations for CO 2 differ in a number of respects from those used for the non-CO 2 gases. The more detailed calculations used for this approach are essentially similar in content to those used for the Reference Approach.
The formula is:

carbon emissions

= ∑

fuel consumption expressed in energy units (TJ) for each sector x carbon emission factor - carbon stored x fraction oxidised

There are seven key considerations when calculating CO 2 emissions by sector some of which have already been discussed for the Reference Approach:

• Identification of the quantities of fuels consumed (combusted) in energy industries;

• A clear understanding of how emissions from electricity generation and heat are treated;

• Identification of the fraction of carbon released during the use of fuels for non-energy purposes;

• Adjustments for carbon unoxidised;

• Identification of the quantities of fuels used for international transport;

• Separation of the emissions from the combustion of biofuels;

• Separation of the quantities of fuels used in the Agriculture/Forestry/Fisheries between mobile sources and stationary plant.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.31 Quantities of fuels combusted in the energy industries. For emission calculations there are three principal groups of activities involving fuels in the energy and transformation sector: (i) The transformation of primary fuels into secondary fuels by physical or chemical processes not involving combustion of the primary fuel. For example, manufacture of petroleum products from crude oil. (ii) The production of heat for sale or for electricity generation. (iii) Combustion of fuels to support the main energy extraction or production business of the enterprise. For example, use of refinery gas for heating distillation columns, use of colliery methane at mines for heating purposes. Activities within the first group are mainly those of refining and manufacture of solid fuels and derived gases. By definition, group (i) does not lead to fuel combustion emissions. Only fuels entering the activities in groups (ii) and (iii) should be considered for the calculation of emissions. The underlying model of carbon flow which drives the reporting for the energy and transformation sector is that primary fuel carbon entering group (i) will appear either in the secondary products or be lost as fugitive emissions which are reported separately in Category 1B, Fugitive Emissions from Fuels. Carbon in secondary products will be partly or entirely stored or combusted either: 1) within the transformation industry as a group (iii) activity (e.g, refinery fuel or coke oven gas for heating coke ovens), or 2) as a group (ii) activity, or 3) by final consumers outside the energy industry. In short therefore, because the pathways for carbon leaving a transformation process are covered by reporting on the worksheets in Module 1, there is no need to report quantities of primary fuels used exclusively for refining or solid fuel manufacture, notably, crude oil and coking coal. If, however, a country does use crude oil for electricity generation, for example, then the relevant quantity should be reported. The scope of the activities to be included under group (ii) also needs further definition and this will be considered now.
Generation of electricity and heat The Overview to this chapter (Section 1.1) describes the steps taken to harmonise reporting and inventory compilation required from those countries completing inventories according to both IPCC and EMEP/CORINAIR reporting requirements. An important step towards harmonisation has been the decision to align the IPCC reporting of emissions from electricity and heat generation by autoproducers (see Box 3) with that of CORINAIR.
In the 1995 Guidelines emissions from autoproducers were included with those from main power producers (referred to as “Public Electricity and Heat”). In this edition of the Guidelines , emissions from autoproduction are attributed to the industrial or commercial branches in which the generation activity occurs. Emissions reported under “Public Electricity and Heat” should be those from main power producers only.

## E NERGY

1.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual B OX 3 A UTOPRODUCERS An autoproducer of electricity or heat is an enterprise which generates electricity or sells heat as a secondary activity, i.e., not as its main business. This should be contrasted with main power producers who generate electricity or who sell heat as their main business (primary activity) and may be publicly or privately owned. Supplies from main power producers are referred to as “Public” electricity and heat supply although an increasing part of public supply is being met by autoproducers.

Wherever possible the quantities of fuel used for, and the resulting emissions from, autoproduction should be identified in the worksheets used for this calculation. The worksheets make provision for this. As a growing amount of public electricity supply comes from autoproduction, calculation of the related emissions will assist identification of total emissions from electricity generation.
Carbon release during the non-energy use of fuels The calculation of carbon content of fuels consumed, as a step for the estimation of the CO 2 emissions from fuel combustion, must be adjusted for the quantities of carbon which are stored within products made from fuels used as raw materials or within products used for their physical properties rather than combusted (e.g., bitumen or lubricants). The approach used to do this and the types of fuels involved are fully discussed under “Stored Carbon” in Section 1.4.1.1 and the arguments will not be repeated. There are two aspects of this adjustment, however, which need to be mentioned explicitly here because the calculation of carbon release at the level of fuel deliveries permits certain simplifications not available at the level of fuel supplies used for the Reference Approach. This arises because the Reference Approach estimates emissions from the supply of primary fuels and external trade in secondary fuels whereas the sectoral approach usesthe carbon content of delivered fuels from which the full quantities of fuels entering longterm storage may be identified. 1 Bitumen and coal tars are usually not combusted but used in a manner which causes most of the carbon content to enter long-term storage. As a result, these products are excluded from the calculation of fuel combustion emissions and do not feature in the list of commodities on the worksheet. 2 Other fuels that are only partly combusted are included within the worksheet and the fraction of carbon entering long-term storage estimated by means of a carbon storage factor. A similar method is used for the Reference Approach. In the present sectoral calculation, however, no special steps are required to obtain deliveries data as the approach relies on them for all of its calculations.
Adjustments For Carbon Unoxidised As discussed above under the Reference Approach, the amount of carbon that may remain unoxidised from combustion activities can vary for many reasons, including type of fuel consumed, type of combustion technology, age of the equipment, and operation and maintenance practices. Since the present approach relies on more disaggregated fuel consumption data, it is possible to specify the assumptions for unoxidised carbon by application. Unless other data are available, countries should use as default values the assumptions recommended in the Reference Approach: 2 per cent of carbon in fuel consumed is unoxidised for coal, 1 per cent for oil-derived fuels, 0.5 per cent for natural

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.33 gas and 1 per cent for peat used for electricity generation. In addition, the following assumptions (from Summers, 1993) are recommended:

• For stoker-fired industrial boilers an average value for carbon unoxidised is 5 per cent. If countries believe that their operation and maintenance procedures achieve maximum efficiency, a 2 per cent carbon loss is suggested. If these procedures are believed to lead to very poor efficiency, then a 10 per cent carbon loss is recommended.

• In those cases when coal is used in the commercial or residential sectors, the assumption for unoxidised carbon should be 5 per cent. Clearly, much additional research needs to be done in this area. These adjustments are suggested as initial default values. As more work is done, countries are encouraged to report any additional information they may have to refine understanding of the amount of carbon unoxidised in various applications.
Fuels used for international transport The exclusion from national totals of emissions from (bunker) fuels used for international marine and air transport has been discussed in Section 1.4.1.1, Reference Approach. As in that approach, the emissions from international bunkers should not be omitted entirely but reported separately on the worksheet. The definitions of national and international
movements for ships and aircraft are covered under the “Definition of Source Categories” (Energy) in Volume 1, Reporting Instructions

.
Combustion of biofuels
CO 2 emissions from the combustion of biomass fuels are not to be included in the total national CO 2 emissions but should be reported separately on the worksheet.

Fuel use for mobile sources and stationary plant in the Agriculture/Forestry/ Fisheries sector The separation of fuel combustion between the two types of combustion sources in this sector has been introduced to permit the aggregation of CO 2 emissions from them with the emissions of the non-CO 2 gases. Whatever methods are used for estimating the quantities of fuels used by these two types when calculating the non-CO 2 emissions from this sector should be used for CO 2 . Delivery statistics do not usually distinguish between combustion plant types in any economic activity sector.



### 1.4.2 Non-CO 2 

### Emissions

1.4.2.1 M ETHANE 

### (CH 4 

### ) E MISSIONS FROM 

### F UEL 

### C OMBUSTION The contribution of fuel combustion to global emissions of methane is minor and the uncertainty is high. For these reasons, an aggregated fuel/sector split is sufficient for a Tier 1 approach, although exact product detail needs to be determined for CH 4 from biomass combustion. Fuel wood, charcoal, agricultural residues, agricultural waste and municipal waste combustion is by far the major contributor to CH 4 emissions within the fuel combustion group. Traditional charcoal making, which is a typical smouldering process, is a large source of methane which should be reported under Fugitive Emissions

## E NERGY

1.34 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual from Energy. Consequently, CH 4 emissions from developing countries with large biomass consumption could be significant. Methane is produced in small quantities from fuel combustion due to incomplete combustion of hydrocarbons in fuel. The production of methane is dependent on the temperature in the boiler/stove. In large, efficient combustion facilities and industrial applications, the emission rate is very low, with utility emission rates being less than I per cent of average rates for residential coal combustion. In smaller combustion sources, emission rates are higher, particularly when smouldering occurs. The highest rates of methane emissions from fuel combustion occur in residential applications (small stoves and open burning).
The CH 4 emissions from mobile sources are a function of the methane content of the motor fuel, the amount of hydrocarbons passing unburnt through the engine, the engine type, and any post-combustion controls. In uncontrolled engines the proportion of methane emissions is highest at low speeds and when the engine is idle. Poorly tuned engines may have a particularly high output of CH 4 . The general method for estimating CH 4 can be described as:
Emissions = ∑ (EF ab x Activity ab )
where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; and b = Sector-activity. The following default emission factors have been developed by the IPCC based on the CORINAIR90 database, the CORINAIR 1994 default emission factors, the EDGAR Version 2.0 database, National Communications to the FCCC, Berdowski, et al. (1993a and 1993b), Radian Corporation (1990) and US EPA (1995). Additional research will need to be undertaken to further improve the quality of the emission factors.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.35 T ABLE 1-7 CH 4 D EFAULT (U NCONTROLLED ) E MISSION F ACTORS ( IN KG /TJ)

Coal (a) Natural Gas Oil Wood/ Wood Waste Charcoal Other Biomass and Wastes (c)
Energy Industries 1 1 3 30 (b) 200 (b) 30 Manufacturing Industries and Construction 10 5 2 30 200 30

Transport Aviation (d) 0.5
Gasoline Diesel Road 50 20 (e) 5 Railways 10 5 Navigation 10 5

Other Commercial/Institutional 10 5 10 300 200 300 Sectors Residential 300 5 10 300 200 300 Agriculture/ Forestry/ Stationary 300 5 10 300 200 300
Fishing Mobile 5 5 Note: These factors are considered as the best available global default factors to date. (a) The emission factors for brown coal may be several times higher than those for hard coal. (b) These factors are for fuel combustion in the energy industries. For charcoal production, please refer to Table 1-14, Default Non-CO 2 Emission Factors for Charcoal Production. (c) Includes dung and agricultural, municipal and industrial wastes. (d) In the cruise mode CH 4 emissions are assumed to be negligible (Wiesen et al., 1994). For LTO cycles only (i.e., below an altitude of 914 metres (3000 ft.)) the emission factor is 5 kg/TJ (10% of total VOC factor) (Olivier, 1991). Since globally about 10% of the total fuel is consumed in LTO cycles (Olivier, 1995), the resulting fleet averaged factor is 0.5 kg/TJ. (e) Emission factors for 2-stroke engines may be three times higher than those for 4-stroke engines.



### 1.4.2.2 N ITROUS 

### O XIDE 

### ( N 2 

### O) E MISSIONS FROM 

### F UEL 

### C OMBUSTION As with methane, the contribution of fuel combustion to global emissions of N 2 O is minor and the uncertainty is high. Reliable emission factors are not yet available for all sources. For these reasons, an aggregated fuel/sector split is sufficient for a Tier 1 approach. Nitrous oxide is produced directly from the combustion of fossil fuels. It has been determined that lower combustion temperatures (particularly below 1200 K) cause higher N 2 O emissions with a maximum of N 2 O production occurring around 1000 K. For combustion temperatures below 800 K or over 1200 K the emissions of N 2 O are negligible (de Soete, 1993). Compared to emissions from conventional stationary combustion units, emissions of nitrous oxides from fluidised bed combustion are relatively high (Rentz et al., 1992). Nitrous oxide is formed by different catalytic reduction processes. For more detailed information on N 2 O chemistry see de Soete (1993). The mechanisms of N 2 O chemistry seem to be relatively well understood, but experimental data are limited.
N 2 O emissions from vehicles have only recently been studied in detail. Global emissions from this source are still thought to be small relative to total anthropogenic emissions, but may be substantially higher when emission controls (especially catalysts on road vehicles) are used.

## E NERGY

1.36 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Published emission rates for non-commercial fuel combustion, in particular fuelwood, charcoal, agricultural wastes and dung are few and it is uncertain whether they are representative for global application (Olivier, 1993). The general method for estimating N 2 O can be described as:
Emissions = ∑ (EF ab x Activity ab )
where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; and b = Sector-activity. The following default emission factors have been developed by the IPCC based on the CORINAIR90 database, the CORINAIR 1994 default emission factors, Radian Corporation (1990), the EDGAR Version 2.0 database, National Communications to the FCCC and de Soete (1993). Additional research will need to be undertaken to further improve the quality of the emission factors.

T ABLE 1- 8 N 2 O D EFAULT (U NCONTROLLED ) E MISSION F ACTORS ( IN KG /TJ)

Coal (a) Natural Gas Oil Wood/ Wood Waste Charcoal Other Biomass and Wastes (c)
Energy Industries 1.4 0.1 0.6 4 (b) 4 (b) 4 Manufacturing Industries and Construction 1.4 0.1 0.6 4 4 4

Transport Aviation 2
Gasoline Diesel Road 0.1 0.6 (d) 0.6 Railways 1.4 0.6 Navigation 1.4 0.6

Other Commercial/Institutional 1.4 0.1 0.6 4 1 4 Sectors Residential 1.4 0.1 0.6 4 1 4 Agriculture/ Forestry/ Stationary 1.4 0.1 0.6 4 1 4
Fishing Mobile 0.1 0.6 Note: These factors are considered as the best available global default factors to date. (a) Brown coals may produce less N 2 O than bituminous coals; some measurements have shown that N 2 O emissions by hard coal combustion in power plants may be negligible. N 2 O emissions from FBC are generally about 10 times higher than from boilers. (b) These factors are for fuel combustion in the energy industries. For charcoal production, please refer to Table 1- 14 , Default Non-CO 2 Emission Factors for Charcoal Production. (c) Includes dung and agricultural, municipal and industrial wastes. (d) When there is a significant number of cars with 3-way catalysts in the country, road transport emission factors should be increased accordingly. E mission factors for 2- stroke engines may be three times higher than those for 4-stroke engines.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.37 1.4.2.3 N ITROGEN 

### O XIDES 

### (NO X 

### ) E MISSIONS FROM 

### F UEL 

### C OMBUSTION Nitrogen oxides 11 are indirect greenhouse gases. They have been the target of environmental policies for their role in forming ozone (O 3 ), as well for their direct acidification effects. Fuel combustion activities are the most significant anthropogenic source of NO x . Within fuel combustion, the most important sources are the energy industries and mobile

sources. Generally two different formation mechanisms can be distinguished:

• formation of “fuel NO” from the conversion of chemically bound nitrogen in the fuel,

• formation of “thermal NO” from the fixation of the atmospheric nitrogen in the combustion process (Joint EMEP/CORINAIR, February 1996). The majority of NO x emitted from coal (80-90 per cent) is formed from fuel nitrogen. Thermal NO x contributes less than 20 per cent and depends on combustion temperature. Excess air and high temperatures found in some firing configurations encourage the production of NO x and these conditions are dependent on boiler type and operation of technology. For oil, the share of fuel NO x may be less than 50 per cent. From gaseous fuels, only “thermal NO” is formed.
The NO x emissions from mobile sources are related to the air-fuel mix and combustion temperatures, as well as pollution control equipment. For uncontrolled vehicles the proportion of NO x emissions from a diesel-fuelled vehicle is generally lower than that for a gasoline-fuelled vehicle, and lower for a light-duty vehicle than that for a heavy-duty vehicle. Heavy-duty vehicles contribute significant emissions, which are difficult to reduce. The general method for estimating NO x can be described as:

Emissions = ∑ (EF ab x Activity ab )

where:
EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ);

a = Fuel type; and b = Sector-activity. If abatement technologies for NO x emissions reduction are used, the estimated emission factors of NO x should be adjusted. Reduction efficiency (n) values for different types of abatement may vary; primary measures may range from 5 to 50 per cent (Joint EMEP/CORINAIR, 1996) and secondary measures from 50 to 95 per cent (Rentz, et al., 1992). The following default values can be used for the reduction efficiency of primary measures in coal-fired installations when no information concerning the type of installation is available (Joint EMEP/CORINAIR, 1996).

11 The convention in this document is that NO x (NO+NO 2 ) emissions from fossil fuel combustion are expressed on a full molecular basis assuming that all NO x emissions are emitted as NO 2 .

## E NERGY

1.38 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Default Values for Reduction Efficiency (n) Type of primary measure Hard coal Lignite no measure (mainly relevant for old installations) 0 % 0 % old installations / optimised operation 15 - 20 % 15 %
old installation / retrofitted 50 % 50 %
new installation 40 % 35 %

Due to large differences in emission factors for various sectors, fuel consumption should be allocated to the IPCC main source category groups. Nitrogen oxides emission factors are available by detailed fuel/sector split for most of the fuel combustion sources. The following default emission factors have been developed by the IPCC based on the CORINAIR90 database, Radian Corporation (1990), US EPA (1995), the EDGAR Version 2.0 database, and National Communications to the FCCC. The aggregated emission factors in this table allow a rough estimation of NO x emissions.

T ABLE 1-9 NO X D EFAULT (U NCONTROLLED ) E MISSION F ACTORS ( IN KG /TJ) (a)

Coal Natural Gas Oil Wood/ Wood Waste Charcoal Other Biomass and Wastes (b)
Energy Industries 300 150 200 100 (c) 100 (c) 100 Manufacturing Industries and Construction 300 150 200 100 100 100

Transport Aviation 300
Gasoline Diesel Road 600 600 800 (d) Railways 300 1200 Navigation 300 1500

Other Commercial/Institutional 100 50 100 100 100 100 Sectors Residential 100 50 100 100 100 100 Agriculture/ Forestry/ Stationary 100 50 100 100 100 100 Fishing Mobile (e) 1000 1200

Note: These factors are considered as the best available global default factors to date. The emission factors may be reduced to take into account reduction efficiencies, see default values for reduction efficiencies given above. (a) NO x emission factors for small combustion facilities tend to be much smaller than for large facilities due to lower combustion temperatures. (b) Includes dung and agricultural, municipal and industrial wastes. (c) These factors are for fuel combustion in the energy industries. For charcoal production, please refer to Table 1-14, Default Non-CO 2 Emission Factors for Charcoal Production. (d) Assuming the major part is consumed by Heavy Duty Vehicles (HDV). When a country has a relatively high proportion of passenger cars running on diesel, the average emission factor may be substantially lower, as is indicated in Tables I - 31 to 1 - 34. (e) The countries should, when possible, allocate the fuel consumption to road and off-road traffic. Emission factors for ships, boats, locomotives and farm equipment may be more than double those of duty vehicles.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.39 1.4.2.4 C ARBON 

### M ONOXIDE 

### (CO) E MISSIONS FROM 

### F UEL 

### C OMBUSTION Carbon monoxide is an indirect greenhouse gas. The majority of CO emissions from fuel combustion come from motor vehicles. Another large contributor is the residential sector with small combustion equipment. Carbon monoxide is an intermediate product of the combustion process and in particular under stoichiometric combustion conditions. The formation mechanism of CO is directly influenced by usage patterns, technology type and size, vintage, maintenance, and operation of the technology. Emission rates may vary by several orders of magnitude for facilities that are poorly operated or improperly maintained, such as might be the case of older units. Size and age of unit may indicate that in smaller and older units, combustion is less controlled and hence emissions are likely to be higher than from larger and newer plants. In addition, many wood stoves (where there is a great variation in technology by geographic region) have particularly high emissions due to their largely inefficient combustion of fuel. Carbon monoxide emissions from mobile sources are a function of the efficiency of combustion and post combustion emission controls. Emissions are highest when air-fuel mixtures are rich, with less oxygen than required for complete combustion. This occurs especially in idle, low speed, and cold start conditions in spark ignition engines. The general method for estimating CO can be described as:

Emissions = ∑ (EF ab x Activity ab )

where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; and b = Sector-activity. Due to large differences in emission factors for various sectors, fuel consumption must be allocated to the IPCC main activity groups. Carbon monoxide emission factors are available by detailed fuel/sector split for most of the fuel combustion sources. The following default emission factors have been developed by the IPCC based on the CORINAIR90 database, Radian Corporation (1990), US EPA (1995), the EDGAR Version 2.0 database, and National Communications to the FCCC. The aggregated emission factors in this table allow a rough estimation of CO emissions.

## E NERGY

1.40 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-10 CO D EFAULT (U NCONTROLLED ) E MISSION F ACTORS ( IN KG /TJ)

Coal Natural Gas Oil Wood/ Wood Waste Charcoal Other Biomass and Wastes (a)
Energy Industries 20 20 15 1000 (b) 1000 (b) 1000 Manufacturing Industries and Construction 150 30 10 2000 4000 4000

Transport Aviation (c) 100
Gasoline Diesel Road 400 8000 (d) 1000 Railways 150 1000 Navigation 150 1000

Other Commercial/Institutional 2000 50 20 5000 7000 5000 Sectors Residential 2000 50 20 5000 7000 5000 Agriculture/ Forestry/ Stationary 2000 50 20 5000 7000 5000 Fishing Mobile 400 1000
Note: These factors are considered as the best available global default factors to date. (a) Includes dung and agricultural, municipal and industrial wastes. (b) These factors are for fuel combustion in the energy industries. For charcoal production, please refer to Table 1-14, Default Non-CO 2 Emission Factors for Charcoal Production. (c) The emission factor for aviation in the above table is for jet kerosene. The emission factor for aviation gasoline ranges from 10 000 to 20 000 kg/TJ (default value: 15 000 kg/TJ). (d) Generally the emission factors for gasoline vehicles are highest for motorcycles and passenger cars without emissions control equipment.



### 1.4.2.5 N O N 

### - M ETHANE 

### V OLATILE 

### O RGANIC 

### C OMPOUNDS 

### (NMVOC) E MISSIONS FROM 

### F UEL 

### C OMBUSTION Non-Methane Volatile Organic Compounds 12 are indirect greenhouse gases. The most important sources of NMVOCs from fuel combustion activities are mobile sources and residential combustion (especially biomass combustion). Emissions of NMVOC (e.g., olefins, ketones, aldehydes) are the product of incomplete combustion. They are directly influenced by fuel used, usage patterns, technology type and size, vintage, maintenance and operation of the technology. Emission rates may vary by several orders of magnitude for facilities that are poorly operated or improperly maintained, such as might be the case of older units.

The emissions are very low for large-combustion plants. NMVOC emissions tend to decrease with increases in plant size and increasing efficiency of the combustion process.

12 Non-methane volatile organic compounds: all hydrocarbon compounds, including those where hydrogen atoms are partly, or fully, replaced by other atoms (S,N,O, halogens) excluding those inventoried under the Montreal protocol. They are volatile under ambient air conditions and expressed as mass units as measured.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.41 In addition, wood stoves (where there is a great variation in technology by geographic region) may have particularly high emissions rates of NMVOC due to their largely inefficient combustion of fuel.
The NMVOC emissions from mobile sources are a function of the amount of hydrocarbons passing unburnt through the engine. This depends on engine type, fuel used, use of post-combustion emission controls (e.g., catalytic converters) and driving regime. The emissions are generally highest at low speeds and when the engine is idle. Poorly tuned engines may have a particularly high output of hydrocarbon compounds. NMVOC evaporative emissions from gasoline mobile sources should be accounted for here. The general method for estimating NMVOC can be described as:

Emissions = ∑ (EF ab x Activity ab )

where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; and b = Sector-activity. Due to large differences in emission factors for various sectors, fuel consumption must be allocated to the IPCC main activity groups.
Extensive NMVOC emission factor data are available for most of the fuel combustion sources. The following default emission factors have been developed by the IPCC based on the CORINAIR90 database, Radian (1990), US EPA (1995), the EDGAR Version 2.0 database, and National Communications to the FCCC. The aggregated emission factors in this table allow a rough estimation of NMVOC emissions.

## E NERGY

1.42 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1- 11 NMVOC D EFAULT (U NCONTROLLED ) E MISSION F ACTORS ( IN KG /TJ)

Coal Natural Gas Oil Wood/ Wood Waste Charcoal Other Biomass and Wastes (a)
Energy Industries 5 5 5 50 (b) 100 (b) 50 Manufacturing Industries and Construction 20 5 5 50 100 50

Transport Aviation (c) 50
Gasoline Diesel Road 5 1500 (d) 200 Railways 20 200 Navigation 20 200

Other Commercial/Institutional 200 5 5 600 100 600 Sectors Residential 200 5 5 600 100 600 Agriculture/ Forestry/ Stationary 200 5 5 600 100 600
Fishing Mobile 5 200
Note: These factors are considered as the best available global default factors to date. (a) Includes dung and agricultural, municipal and industrial wastes. (b) These factors are for fuel combustion in the energy industries. For charcoal production, please refer to Table 1- 14 , Default Non-CO 2 Emission Factors for Charcoal Production. (c) The emission factor for aviation in the above table is for jet kerosene. The emission factor for aviation gasoline is 300 kg/TJ. (d) These factors are the sum of combustion and evaporative emissions from gasoline use. The NMVOC emission factors for mobile sources from evaporation of gasoline vary with the ambient temperature. In general, in the “ warmer ” countries the emission factors will be higher than in “ colder ” countries.



### 1.4.2.6 S ULPHUR 

### D IOXIDE 

### (SO 2 

### ) E MISSIONS FROM 

### F UEL 

### C OMBUSTION Sulphur dioxide is not a “greenhouse gas” but its presence in the atmosphere may influence climate. SO 2 can react with a variety of photochemically produced oxidants to form sulphate aerosols. The concentration of these particles is increasing due to the burning of fossil fuels which contain sulphur. Over limited regions of the northern hemisphere, the effect of these particles is comparable in size, although opposite in effect, to that of human generated greenhouse gases up to the present time. Any effect of sulphur dioxide emissions on climate change can be expected to be strongly regional in character - but studies of this with climate models need to be carried out (Houghton, 1994). Although SO 2 is not a direct greenhouse gas, it is an aerosol precursor and as such, has a cooling effect on climate. Anthropogenic SO 2 emissions world-wide amount to 70-80 million tonnes per year (Mt/y) (Vernon and Jones, 1993). This compares with natural emissions of 18-70 Mt/y (IPCC, 1992). There is, however, a paucity of information on the relative contribution of sulphur emissions arising from combustion, due to lack of detailed information on the sulphur level of the fuel consumed. More than 80 per cent of anthropogenic SO 2 arises from fuel combustion, with three-quarters of this arising from coal (Vernon, 1990). At present an estimated 10 Mt/y of coal-related SO 2 emissions are removed by flue-gas desulphurisation technology world-wide (Ando, 1992).

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.43 The general method for estimating SO 2 can be described as:

Emissions = ∑ ( EF ab x Activity ab )

where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; and b = Sector-activity. The emissions of sulphur oxides (SO x ) are directly related to the sulphur content of the fuel, which for coal can vary from below 0.5 to over 10 per cent by weight. The majority of coals currently in use are in the range 0.5 to 3 per cent. Generally the “southern hemisphere” coals contain less sulphur than “northern hemisphere” coals. For fuel oil (including heavy fuel oil) sulphur content varies from 0.3 to over 5 per cent. Lighter products may contain minimal sulphur (<0.3 per cent), whilst heavy fuel oil can contain from up to 3-5 per cent sulphur. Currently the world average sulphur content of crude oil is around 1.3 per cent, although there are considerable variations between different sources (Vernon and Jones, 1993). The sulphur content of gas is usually negligible.
The SO 2 13 emission factors can be estimated as:

EF SO 2 [kg/TJ] = s 100 1 00 - r 100 1 0 0 - n 100 

### 2 x 

### ( ) x x 1 0 6 x 

### ( ) x 

### ( ) 1 Q

where: EF = Emission Factor (kg/TJ); 2 = SO 2 /S [kg/kg]; s = Sulphur content in fuel [%]; r = Retention of sulphur in ash [%]; Q = Net calorific value [TJ/kt]; 10 6 = (Unit) conversion factor; and n = Efficiency of abatement technology and/or reduction efficiency [%]. Sulphur appears in coal as pyritic sulphur (FeS 2 ), organic sulphur, sulphur salts and elemental sulphur. Pyritic and organic sulphur account for the vast majority of sulphur in coal and both types are responsible for SO x formation. The sulphur is released when the coal is burnt, mainly oxidised to SO 2 . Usually less than 1-2 per cent of the total sulphur is released as SO 3

.

13 Sulphur dioxide (SO 2 + SO 3 expressed as SO 2 mass equivalent).

## E NERGY

1.44 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-12 S AMPLE AND D EFAULT V ALUES OF S ULPHUR C ONTENT ( S ) IN F UEL Fuel (IPCC grouping) Default value (a)

[%] CORINAIR 90 (b)
range

[%]

Coal - low S 0.5 ≥ 0.001
- medium S 1.5 - - high S 3.0 ≤ 16.1 Heavy fuel oil - low S 1.0 ≥ 0.001
- medium S 3.0 (c)

- - high S 4.0 ≤ 4.0 Light fuel oil/diesel - low S 0.3 ≥ 0.14 - high S 1.0 ≤ 1.0 Diesel (road) 0.3 0.1-1.0 Gasoline (road) 0.1 0.012 - 0.15 Jet kerosene 0.05 0.0001-0.3 (d)

Oil shale 1.5(1.3-1.7) (e) NAV Natural gas negligible NAV Municipal waste 0.003 0.003
Industrial waste 0.2 0.200 - 1.000 Black liquor 1.5 0.004 - 8.09

Fuelwood 0.2 0.001-0.06
Other biomass < 0.03 0.001 - 0.800 (a) To be used only if no better information is available. (b) Fuels used in CORINAIR 90 inventories in the Czech Republic, Denmark, France, Hungary, Italy, the Netherlands, Poland and the Slovak Republic. (c) The medium value refers to the default for marine bunkers. (d) Values reported in literature. (e) Values from Estonia.

During fuel combustion, part of the sulphur is retained in ash. The sulphur retention in ash for coal ranges from 5 to 60 per cent, (usually less than 10 per cent). The proportion depends upon the composition of the ash. The sulphur retention in ash for liquid fuels and biomass is minimal and can be disregarded.

Default Values for the Sulphur Retention (r) in Ash [%]

Hard coal 5
Brown coal 30

If abatement technologies for SO x emissions reduction are used, the estimated emission factors for SO 2 should be correspondingly reduced. Reduction efficiency values for different types of abatement technologies may vary between 45 and 95 per cent (Rentz, et al., 1992).

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.45 

### 1.4.3 Biomass Data The tables below provide data for use within the Reference Approach or for the calculation of all emissions by source categories using the methods described in Sections 1.4.1 and 1.4.2.

T ABLE 1-13 E NERGY C ONTENT OF B IOMASS F UELS : D EFAULT N ET C ALORIFIC V ALUES
Biomass Fuel Moisture Content (% mcwb) (a) Typical Net Calorific Value (b) (MJ/kg) Reference

BASIC BIOFUEL TYPES:
Fuelwood (c) 20 15 Hall et al. (1994b) Charcoal 30 Hall and Mao (1994a) Dung 12 GOB (1987) Bagasse 50 8 Leach and Gowen (1987) Agricultural Waste 15 Leach and Gowen (1987) Other Waste 11 US EPA (1995)
EXAMPLES OF SPECIFIC BIOFUELS:
Wood Wet, freshly cut 40 10.9 Leach and Gowen (1987) Air-dry, humid zone 20 15.5 Leach and Gowen (1987) Air-dry, dry zone 15 16.6 Leach and Gowen (1987) Oven-dry 0 20.0 Leach and Gowen (1987)
Charcoal 5 29.0 Leach and Gowen (1987) Bagasse Wet 50 8.2 Leach and Gowen (1987) Air-dry 13 16.2 Leach and Gowen (1987) Dung cakes (dried) 12 12.0 Leach and Gowen (1987)

OTHER AGRICULTURAL RESIDUES:
Coffee Husks 12 16.0 Leach and Gowen (1987) Ricehulls (air-dry) 9 14.4 Leach and Gowen (1987)
Wheat straw 12 15.2 Leach and Gowen (1987) Maize (stalk) 12 14.7 Leach and Gowen (1987) Maize (cobs) 11 15.4 Leach and Gowen (1987) Cotton gin trash 24 11.9 Leach and Gowen (1987)
Cotton stalk 12 16.4 Leach and Gowen (1987) Coconut husks 40 9.8 Leach and Gowen (1987)
Coconut shells 13 17.9 Leach and Gowen (1987) (a) mcwb : moisture content weight basis. (b) Typical values to be considered as rough approximations. (c) Assuming air dry wood.

Values for estimating the amount of carbon released through charcoal production and consumption, the wood-to-charcoal factor, are stated to be between 4 and 8. If no local information is available, 6 kg of wood input per kg of charcoal may be used as default

## E NERGY

1.46 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual (FAO, 1990). In many developing countries, there are usually no cross checks on the quality of charcoal. Consequently, substandard charcoal will be passed on as charcoal. Typical wood to charcoal conversion factors in many developing countries would range from 2.5 to 3.5 and rarely beyond this. This also implies that the carbon fraction of charcoal is around 0.6 to 0.7. Default emission factors related to the production of charcoal are presented in the Table I-14

T ABLE I-14 D EFAULT N ON -CO 2 E MISSION F ACTORS FOR C HARCOAL P RODUCTION ( IN KG /TJ)
Compound Default Emission Factor (kg/TJ of Wood Input) (a) Default Emission Factor (kg/TJ of Charcoal Produced)
CH 4 300 1000
N 2 O NAV NAV
NO x 5 10
CO 2000 7000
NMVOC 600 1700
SO 2 NAV NAV (a) Assuming 1 kg charcoal is produced from 6 kg wood and the energy content for wood and charcoal is 15 and 30 MJ/kg respectively, 1 TJ charcoal produced is equivalent to 3 TJ wood input.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.47 

## 1 . 5 D e t a i l e d Met h od s (T i e r s 2 a n d 3 ) f or F u e l Combustion

1.5.1 Overview Identification and quantification of greenhouse gas emissions by source category and economic sector, together with a sound understanding of plant combustion conditions, are essential for the study of abatement procedures and the formulation of abatement policy options. Equally, assessment of the effects of emissions on the atmosphere and climate requires detailed data on the magnitude and spatial distribution of pollutant emissions. Both sets of requirements are served by the estimation of emissions from combustion activities categorised by plant types at a level of detail for which an emission factor can be reasonably narrowly specified. Studies of the products of combustion from many types of plant under different operating conditions have resulted in a growing database of emission factors linking the emission rate to the activity. Estimation methodologies using these emission factors are described and discussed in this section. In what follows, the emission sources are grouped into stationary and mobile sources and representative emission factors for them are assembled for use in a simple formula common to the majority of cases. The distinction between Tier 1 methods and those of Tiers 2 and 3 rests mainly on the reliance of the first on widely available fuel supply data which, by its nature, takes no account of the combustion technology to which the fuel is delivered. Distinguishing between Tiers 2 and 3 is less easily done as there is a steadily increasing degree of refinement and detail in the emissions estimation process as the methods are developed from one tier to another. However, Tier 2 methods may be regarded as those dividing fuel consumption on the basis of sample or engineering knowledge between technology types which are sufficiently homogenous to permit the use of representative emission factors. Tier 3 methods generally estimate emissions from activity figures (kilometre travelled or tonne-kilometre carried, not fuel consumption) and specific fuel efficiency or fuel rates or, alternatively, using an emission factor or factors expressed directly in terms of a unit of activity. A new methodology, developed from that used by CORINAIR, has been introduced for the estimation of emissions from aircraft. Revised emission factors are also given for emissions from many types of stationary combustion and road transport in the United States and Europe.
Estimating CO 2 It follows from the arguments given above for the construction of detailed emission estimates that a country will also benefit from the estimation of CO 2 emissions in parallel with the calculation of non-CO 2 inventories despite the existence of Tier 1 methods for CO 2 estimation. The Overview to this Chapter also emphasises this point. Most of the tables of emission factors for mobile sources, but few of the tables for stationary sources, have figures for CO 2 . In cases where CO 2 emission factors are not given the carbon emission factors provided for the fuel types listed for the Tier 1 methods will suffice. If different fuel qualities are used in different applications national experts may wish to vary the emission factors accordingly.
Where CO 2 emission factors are given in this Chapter they include all carbon based molecule emissions from the process. This ensures that CO 2 totals constructed by summing the results of the detailed estimation of emissions (the “bottom-up” approach)

## E NERGY

1.48 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual will be comparable with the IPCC Reference Approach described under Tier 1 methods above. The Reference Approach provides a simple transparent and verifiable means of accounting for all of the carbon in fuels which could be emitted to the atmosphere. Because of the complexity of covering all sources of fuel combustion and obtaining the related data it does not automatically follow that summing emissions from the many detailed sources will result in a figure close to that obtained from the Reference Approach. Consequently, verification of CO 2 totals against the Reference Approach is an obligation of the IPCC reporting system. Use of carbon emission factors based on the fuel’s carbon content also implies that adjustments may be needed (depending on the combustion process under consideration) for any carbon unoxidised. Carbon remaining unoxidised after combustion is discussed in Section 1.4.1.1. Where emission estimates are prepared by plant type the general information given in the section cited may be used when more specific carbon unoxidised factors are not available. At the level of process detail implicit in Tiers 2 and 3, quantities of fuel combusted should be known or fairly well estimated and quantities delivered for the manufacture of non-energy products identified and excluded. Where this is not the case estimates of carbon stored in manufactured products will need to be made in collaboration with national experts preparing estimates of emissions from Industrial Processes to ensure that there is no double counting of emissions.



### D ATA 

### S OURCES National experts working on detailed emission of non-CO 2 GHGs (particularly the indirect gases) and SO 2 should consult the extensive literature on emission factors and other estimation procedures which has been developed by other inventory programmes outside of the framework of the IPCC/OECD/IEA programme. These data generally contain more technology detail, and are further broken down by size of the various technologies. For mobile sources, data generally contain more vehicle and control technology detail, and are further broken down by operating conditions (e.g., catalyst vintages, driving cycles). The nature of these control assumptions should be known and carefully matched with actual conditions in the country when selecting the specific factors to be used. Some key examples of data sources are:

• Default Emission Factors Handbook (European Environment Agency Task Force, Bouscaren, 1992)

• CORINAIR Working Group on Emission Factors for Calculating 1990 Emissions from Road Traffic, Volume 1: Methodology and Emission Factors (Eggleston, et al., 1992)

• CORINAIR Working Group on Emission Factors for Calculating 1990 Emissions from Road Traffic, Volume 2: COPERT Model, Users Manual (Andrias, et al., 1992)

• Atmospheric Emission Inventory Guidebook (Joint EMEP/CORINAIR, European Environment Agency, 1996)

• US EPA's Compilation of Air Pollutant Emissions Factors (AP-42), 4th Edition 1985, (US EPA, 1985a and 1985b), 5th Edition 1995 (US EPA, 1995) and Supplement F, (US EPA, 1993b)

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.49 • US EPA's MOBILE5a (US EPA 1994a). Contact Terry Newell, US EPA Office of Mobile Sources, 2565 Plymouth Road, Ann Arbor MI 48105, USA; tel: (313) 668- 4462, Email: Newell.Terry@epamail.epa.gov or access the latest information on mobile sources on the world wide web at http://www.epa.gov/OMSWWW/omshome.htm.

• Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory (Stockton and Stelling, 1987)

• Proceedings of the TNO/EURASAP Workshop (TNO, 1993)

• EMEP and CORINAIR Emission Factors and Species Profiles for Organic Compounds. (Veldt, 1991)

• Transport Statistics for Europe (UN ECE, 1989)

• World Road Statistics (International Road Federation, 1990)

• Other compilations of emission factors include - Netherlands Bakkum, et al., 1987, Okken, 1989 - Norway Statens forurensningstilsyn, 1990 - Germany Brieda and Pakleppa, 1989, Fritsche, 1989, Rentz et al., 1988, Walbeck, et al., 1988 - Japan JAERI, 1988 - United Kingdom Eggleston and McInnes, 1987 - UNEP Country Studies - US Country Studies, US CSP, 1996 - National Communications to the FCCC



### 1.5.2 Stationary Combustion

1.5.2.1 O VERVIEW

This section considers emissions of NO x , N 2 O, CO, CH 4 , SO 2 and NMVOCs from stationary combustion plant. Estimation of CO 2 emissions at the level of detail of Tiers 2 and 3 is described in Section 1.5.1. The section focuses on emissions from the combustion of commercial fuels, which include virtually all fossil fuels and biomass fuels traded commercially and used in large combustion plants. Non-CO 2 emissions from combustion of biomass are estimated in exactly the same manner as fossil fuel combustion emissions. 14

. Emissions of non-CO 2 greenhouse gases across activities (sectors and subsectors) will depend upon fuel, technology type and pollution control policies. Emissions will also vary with the size and vintage of the combustion technology, its maintenance, and its operation. Most of a country’s NO xemissions arise from stationary fuel combustion. As defined here (i.e., excluding "traditional" small scale use of biomass), this category generally contributes a smaller but still significant share of national emissions of CO and NMVOC, and, to a lesser extent, of N 2 O and CH 4 . These two gases are nonetheless discussed in some detail because of their priority status within the IPCC/OECD/IEA programme.

14 See Section 1.4.3 for a discussion of CO 2 emissions from biomass combustion.

## E NERGY

1.50 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual A section on SO 2 has been added to the Tier 1 methodology. In the more detailed Tier 2 approach the same basic formula should be applied to more detailed fuel information.



### 1.5.2.2 R ECOMMENDED 

### M ETHODOLOGY

General Method Estimation of emissions from stationary sources can be described using the following basic formula:

Emissions = ∑ (EF abc x Activity abc )

where: EF = Emission Factor (kg/TJ); Activity = Energy Input (TJ); a = Fuel type; b = Sector-activity; and c = Technology type.
Total emission for a particular country is the sum across activities, technologies and fuels of the individual estimates. Emission estimation is based on at least three distinct sets of assumptions or data: 1) emission factors; 2) energy activities; and 3) relative share of technologies in each of the main energy activities. Sources of the emission factors and energy activity data that are relevant internationally are described briefly below and suggestions on appropriate use of such data are made. Technology share or technology splits for each of the various energy activities are needed at least on a national level for non-CO 2 greenhouse gas estimation since emission levels are affected by the technology type. Unfortunately, there is no complete international source of data on technology splits and, as a result, each country will need to develop its own technology splits for each energy activity. The main steps in the inventory method can be summarised as follows: 1 Determine the source and form of the best available, internationally verifiable, national (or sub-national) energy activity data. 2 Based on a survey of national energy activities, determine the main categories of emission factors. 3 Compile best available emission factor data for the country, preferably from national sources. If no national sources are available, select from the options described here. Selection among the options should be based on the similarity of the country to the source of original measurements for types of technology and operating conditions across main energy activities. The selection should also consider the extent to which control technologies may be in place and requires the ability to clearly separate and understand control policy assumptions that may be embedded in the emission factor data.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.51 4 Based on the form of the selected emission factors, identify the technology categories to be used in the national inventory. 15 5 Using these assumptions on technology categories, develop estimates for each of the greenhouse gases for each main activity. 6 Sum the individual activity estimates to arrive at the national inventory total for each of the greenhouse gases.
Technology Splits for Energy Data National data or assumptions on the technology shares of each of the main source sector categories which have been identified as important in each country are necessary to create the linkage between national energy balances and the emission factors. Again, this may be based on "bottom-up" data collection at as detailed a level as individual sources, or it may be more of a “top-down” allocation based on statistical sampling, or engineering judgement. The objective is to match up fuel use, by fuel type, with specific technologies or classes of technologies, for which credible emission factors for non-CO 2 gases can be provided.

Emission Factor Data
Emission factors for all non-CO 2 greenhouse gases from combustion activities vary to lesser or greater degrees with:

• fuel type

• technology

• operating conditions

• maintenance and vintage of technology and so represent the average emission performance of similar technologies. They are therefore technology specific, but may still represent a wide distribution of possible values because of the influence of the other three factors above. When available, the standard deviation of the emission factor should be used to show the range of possible emission factors, and hence emissions, for each particular energy activity. 16



### 1.5.2.3 E MISSION 

### F ACTORS Some tables of representative emission factors for NO x , 17 CO, CH 4 , N 2 O and NMVOCs by main technology and fuel types (based on Radian, 1990) were presented in the preliminary methodology manual (OECD, 1991) distributed by the IPCC. This information is still useful in showing the range and variation of sources and emission rates, and it is

15 This may also require assumptions about the control technologies in place.

16 Unfortunately, the standard deviation of emission factors is rarely reported with emission factor data. One study shows that when considered, variation of emission factors within an energy activity vary widely, from 20 to more than 50 per cent (Eggleston and McInnes, 1987).

17 The convention in this document is that NO x emissions from fossil fuel combustion are expressed on a full molecular basis assuming that all NO x emissions are emitted as NO 2 .

## E NERGY

1.52 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual reproduced in Tables 1-15 to 1-19 for the major categories. 18 All factors are expressed on a kilograms per terajoule of energy input basis (unless stated otherwise) and are stated on a full molecular weight basis. These data are taken from Radian (1990) and show uncontrolled emission factors for each of the technologies indicated. These emission factor data therefore do not include the level of control technology that might be in place in some countries. For instance, for use in countries where control policies have significantly influenced the emission profile, either the individual factors or the final estimate will need to be adjusted. It may be necessary to make adjustments to "raw" emission estimates to account for control technologies in place. Alternative control technologies, with representative percentage reductions, are shown in Tables 1-20 to 1-23 (Radian, 1990) for the main control technologies applicable to each sector. These tables reflect technologies in use for large stationary sources in OECD countries. Preliminary indications are that, in the rest of the world, control technologies are not typically used (see OECD/IEA, 1991). These data should be used in combination with the uncontrolled emission factors to develop a "net" representative emission factor for each of the technologies to be characterised in the national emission profile; alternatively, the emission estimate for each technology could be adjusted downward according to the indicated percentage reduction and the estimated penetration of the control technology. Table 1-24 provides the fuel property assumptions upon which the Radian data are based. The emission factor data in these tables are provided primarily for illustrative purposes. These factors could be used as a starting point or for comparison by national experts working on detailed "bottom-up" inventories. More detail on current emission factors and references is presented in the section on Data Sources.
No emission factors for SO 2 are presented in Tables 1-15 to 1-19. These emission factors should be estimated based on the sulphur content of the fuels (see Section 1.4.2.6, Sulphur Dioxide Emissions from Fuel Combustion). In many countries, biomass is used in traditional, small-scale facilities and open stoves. Emission factors presented in Tables I-16, 1-18 and 1-19 are for industrial combustion and large-scale facilities.

18 Note: several printing errors occurred in the 1995 Guidelines . These have been corrected here.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.53 T ABLE 1-15 U TILITY B OILER S OURCE P ERFORMANCE Emission Factors (kg/TJ energy input) Basic Technology Configuration CO CH 4 NO x N 2 O NMVOCs
Coal Pulverised Bituminous Combustion Dry Bottom, wall fired 9 0.7 380 1.6 NAV Dry Bottom, tangentially fired 9 0.7 250 0.5 NAV Wet Bottom 9 0.9 590 1.6 NAV Bituminous Spreader Stokers With and without re-injection 87 1.0 240 1.6 NAV Bituminous Fluidised Bed Combustor Circulating Bed 310 1.0 68 96 NAV Bubbling Bed 310 1.0 270 96 NAV Bituminous Cyclone Furnace 9 0.2 590 1.6 NAV Anthracite Stokers 10 NAV 160 NAV NAV Anthracite Fluidised Bed Combustors 5.2 NAV 31 NAV NAV Anthracite Pulverised Coal Boilers 310 NAV NAV NAV NAV Pulverised Lignite Combustion Dry Bottom, tangentially fired NAV NAV 130 NAV NAV Dry Bottom, wall fired 45 NAV 200 NAV NAV Lignite Cyclone Furnace NAV NAV 220 NAV NAV Lignite Spreader Stokers NAV NAV 100 NAV NAV Lignite Atmospheric Fluidised Bed 2.8 NAV 63 42 NAV Oil Residual Fuel Oil/Shale Oil Normal Firing 15 0.9 200 0.3 NAV Tangential Firing 15 0.9 130 0.3 NAV Distillate Fuel Oil Normal Firing 16 0.9 220 0.4 NAV Tangential Firing 16 0.9 140 0.4 NAV Distillate Fuel Gaseous Turbines 21 NAV 300 NAV NAV Large Diesel Fuel Engines >600hp (447kW) 350 4.0 1300 NAV NAV Natural Gas Boilers 18 0.1 (a) 250 NAV NAV Large Gas-Fired Gas Turbines >3MW 46 6* 190 NAV NAV Large Dual-Fuel Engines 340 240 1300 NAV NAV Municipal Solid Waste (MSW) Mass Burn Waterwall Combustors 22 NAV 170 NAV NAV MSW - Mass Feed (a) 98 NAV 140 NAV NAV Source: US EPA (1995). (a) Adapted from Radian, 1990.

## E NERGY

1.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-16 I NDUSTRIAL B OILER P ERFORMANCE Emission Factors (kg/TJ energy input) Basic Technology Configuration CO CH 4 NO x N 2 O NMVOCs
Coal Bit./Sub-bit. Overfeed Stoker Boilers 110 1.0 130 1.6 NAV Bit./Sub-bit. Underfeed Stoker Boilers 190 14 170 1.6 NAV Bit./Sub-bit. Hand-fed Units 4800 87 160 1.6 NAV Bituminous/Sub-bituminous Pulverised Dry Bottom, wall fired 9 0.7 380 1.6 NAV Dry Bottom, tangentially fired 9 0.7 250 0.5 NAV
Wet Bottom 9 0.9 590 1.6 NAV Bituminous Spreader Stokers 87 1.0 240 1.6 NAV Bit./Sub-bit. Fluidised Bed Combustor Circulating Bed 310 1.0 68 96 NAV Bubbling Bed 310 1.0 270 96 NAV
Anthracite Stokers 10 NAV 160 NAV NAV
Anthr. Fluidised Bed Combustor Boilers 5.2 NAV 31 NAV NAV
Anthracite Pulverised Coal Boilers NAV NAV 310 NAV NAV
Oil
Residual Fuel Oil Boilers 15 3.0 170 0.3 NAV
Distillate Fuel Oil Boilers 16 0.2 65 0.4 NAV
Small Waste Oil Boilers <0.1MW 15 NAV 58 NAV NAV LPG Boilers Propane 17 NAV 96 NAV NAV
Butane 16 NAV 97 NAV NAV Small Stationary Internal Comb. Engines Gasoline <250hp (186 kW) 27 NAV 0.7 NAV NAV Diesel <600hp (447 kW) 0.4 NAV 1.9 NAV NAV Large Stationary Diesel Engines >600hp (447 kW) 0.3 0.0 1.3 NAV NAV
Natural Gas Large Boilers >100 MBtu/h (293 MW) 18 1.4 250 NAV NAV Small Boilers 10-100 MBtu/h (29.3-293 MW) 16 1.4 64 NAV NAV Heavy Duty Nat. Gas Compressor Eng. Turbines 2.0 0.6 4.1 NAV NAV 2-Cycle Lean Burn 4.7 17 33 NAV NAV 4-Cycle Lean Burn 5.1 13 39 NAV NAV 4-Cycle Rich Burn 20 2.9 28 NAV NAV
Wood
Fuel Cell/Dutch Oven Boilers 290 NAV 17 NAV NAV
Stoker Boilers 590 15 65 NAV NAV
FBC Boilers 61 NAV 87 NAV NAV Bagasse/Ag. Waste Boilers NAV NAV 68 NAV NAV
MSW
MSW Boilers Mass Burn Waterwall 22 NAV 170 NAV NAV Mass Burn Rotary Waterwall 36 NAV 110 NAV NAV Mass Burn Rotary Refrac. Wall 64 NAV 120 NAV NAV Modular, Excess Air NAV NAV 120 NAV NAV Modular, Starved Air 14 NAV 150 NAV NAV Refuse Derived Combustors 90 NAV 240 NAV NAV Source: US EPA (1995).

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.55 T ABLE 1-17 K ILNS , O VENS , AND D RYERS S OURCE P ERFORMANCE Emission Factors (kg/TJ energy input) (a) Industry Source CO CH 4 NO x N 2 O NMVOCs Cement, Lime Kilns - Natural Gas 83 1.1 1,111 NAV NAV Cement, Lime Kilns - Oil 79 1.0 527 NAV NAV Cement, Lime Kilns - Coal 79 1.0 527 NAV NAV Coking, Steel Coke Oven 211 1 35 (b) NAV 16 (b) Chemical Processes, Wood, Asphalt, Copper, Phosphate Dryer - Natural Gas 11 1.1 64 NAV NAV

Chemical Processes, Wood, Asphalt, Copper, Phosphate Dryer - Oil 16 1.0 168 NAV NAV

Chemical Processes, Wood, Asphalt, Copper, Phosphate Dryer - Coal 179 1.0 226 NAV NAV

Source: Radian, 1990. (a) Values were originally based on gross calorific value; they were converted to net calorific value by assuming that net calorific values were 5 per cent lower than gross calorific values for coal and oil, and 10 per cent lower for natural gas. These percentage adjustments are the OECD/IEA assumption on how to convert from gross to net calorific values. (b) Joint EMEP/CORINAIR (1996).

## E NERGY

1.56 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-18 R ESIDENTIAL S OURCE P ERFORMANCE Emission Factors (kg/TJ energy input) Basic Technology Configuration CO CH 4 NO x N 2 O NMVOCs
Coal Anthracite Space Heaters NAV 150 55 NAV NAV
Coal Hot Water Heaters (a) 18 NAV 160 NAV NAV
Coal Furnaces (a) 480 NAV 230 NAV NAV
Coal Stoves (a) 3600 NAV 180 NAV NAV
Oil
Residual Fuel Oil 15 1.4 170 NAV NAV
Distillate Fuel Oil 16 0.7 65 NAV NAV
Furnaces 16 5.8 59 0.2 NAV Propane/Butane Furnaces (a) 10 1.1 47 NAV NAV
Natural Gas
Furnaces 18 NAV 43 NAV NAV
Gas Heaters (a) 10 1 47 NAV NAV
Wood
Wood Pits (a) 4900 200 150 NAV NAV Fireplaces 11000 NAV 110 NAV NAV
Stoves Conventional 10000 210 120 NAV NAV Non-catalytic 6100 NAV NAV NAV NAV Catalytic 4500 380 87 NAV NAV Pellet, Certified 1700 NAV 600 NAV NAV Pellet, Exempt 2300 NAV NAV NAV NAV Masonry Heater Exempt 6500 NAV NAV NAV NAV Source: US EPA (1995). (a) Adapted from Radian, 1990.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.57 T ABLE 1-19 C OMMERCIAL S OURCE P ERFORMANCE Emission Factors (kg/TJ energy input) Basic Technology Configuration CO CH 4 NO x N 2 O NMVOCs
Coal
Coal Boilers (a) 200 10 240 NAV NAV
Oil
Residual Fuel Oil/Shale Oil 15 1.4 170 0.3 NAV
Distillate Fuel Oil 16 0.7 65 0.4 NAV Waste Oil Space Heaters Vaporising Burner 5.0 NAV 33 NAV NAV Atomising Burner 6.3 NAV 48 NAV NAV LPG Boilers Propane 8.4 NAV 71 NAV NAV
Butane 12 NAV 70 NAV NAV
Natural Gas
Boilers 9.4 1.2 45 2.3 NAV
Wood Incineration - high efficiency (a) 440 NAV 130 NAV NAV
Waste
Mass Burn Waterwall 22 NAV 170 NAV NAV
Combustors NAV NAV NAV NAV NAV
MSW Boilers (a) 19 NAV 460 NAV NAV Source: US EPA (1995). (a) Adapted from Radian, 1990.

## E NERGY

1.58 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-20 U TILITY E MISSION C ONTROLS P ERFORMANCE

Technology Efficiency Loss (a)

(%) CO Reduction (%) CH 4 Reduction (%) NO x Reduction (%) N 2 O Reduction (%) NMVOCs Reduction (%) Date Available (b)

Low Excess Air (LEA) -0.5 + + 15 NAV NAV 1970 Overfire Air (OFA) - Coal 0.5 + + 25 NAV NAV 1970
OFA - Gas 1.25 + + 40 NAV NAV 1970
OFA - Oil 0.5 + + 30 NAV NAV 1970
Low NO x Burner (LNB) - Coal 0.25 + + 35 NAV NAV 1980 LNB - Tangentially Fired 0.25 + + 35 NAV NAV 1980
LNB - Oil 0.25 + + 35 NAV NAV 1980
LNB - Gas 0.25 + + 50 NAV NAV 1980 Cyclone Combustion Modification 0.5 NAV NAV 40 NAV NAV 1990 Ammonia Injection 0.5 + + 60 NAV NAV 1985 Selective Catalytic Reduction (SCR) - Coal 1 8 + 80 NAV NAV 1985

SCR - Oil, AFBC 1 8 + 80 NAV NAV 1985
SCR - Gas 1 8 + 80 60 NAV 1985 Water Injection - Gas Turbine Simple Cycle 1 + + 70 NAV NAV 1975

SCR - Gas Turbine 1 8 + 80 60 NAV 1985
Retrofit LEA -0.5 + + 15 NAV NAV 1970
Retrofit OFA - Coal 0.5 + + 25 NAV NAV 1970
Retrofit OFA - Gas 1.25 + + 40 NAV NAV 1970
Retrofit OFA - Oil 0.5 + + 30 NAV NAV 1970
Retrofit LNB - Coal 0.25 + + 35 NAV NAV 1980
Retrofit LNB - Oil 0.25 + + 35 NAV NAV 1980
Retrofit LNB - Gas 0.25 + + 50 NAV NAV 1980
Burners Out of Service 0.5 + + 30 NAV NAV 1975 (a) Efficiency loss as a percentage of end-user energy conversion efficiency (ratio of energy output to energy input for each technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement. (b) Date technology is assumed to be commercially available. Note: A "+" indicates negligible reduction. Source: Radian, 1990.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.59 T ABLE 1-21 I NDUSTRIAL B OILER E MISSION C ONTROLS P ERFORMANCE

Technology Efficiency Loss (a)

(%) CO Reduction (%) CH 4 Reduction (%) NO x Reduction (%) N 2 O Reduction (%) NMVOCs Reduction (%) Date Available (b)

Low Excess Air (LEA) -0.5 + + 15 NAV NAV 1970 Overfire Air (OFA) - Coal 0.5 + + 25 NAV NAV 1970
OFA - Gas 1.25 + + 40 NAV NAV 1970
OFA - Oil 0.5 + + 30 NAV NAV 1970
Low NO x Burner (LNB) - Coal 0.25 + + 35 NAV NAV 1980
LNB - Oil 0.25 + + 35 NAV NAV 1980
LNB - Gas 0.25 + + 50 NAV NAV 1980
Flue Gas Recirculation 0.5 + + 40 NAV NAV 1975 Ammonia Injection 0.5 + + 60 NAV NAV 1985 Selective Catalytic Reduction (SCR) - Coal 1 8 + 80 NAV NAV 1985

SCR - Oil, AFBC 1 8 + 80 NAV NAV 1985
SCR - Gas 1 8 + 80 60 NAV 1985
Retrofit LEA -0.5 + + 15 NAV NAV 1970
Retrofit OFA - Coal 0.5 + + 25 NAV NAV 1970
Retrofit OFA - Gas 1.25 + + 40 NAV NAV 1970
Retrofit OFA - Oil 0.5 + + 30 NAV NAV 1970
Retrofit LNB - Coal 0.25 + + 35 NAV NAV 1980
Retrofit LNB - Oil 0.25 + + 35 NAV NAV 1980
Retrofit LNB - Gas 0.25 + + 50 NAV NAV 1980 (a) Efficiency loss as a percentage of end-user energy conversion efficiency (ratio of energy output to energy input for each technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement. (b) Date technology is assumed to be commercially available. Note: A "+" indicates negligible reduction. Source: Radian, 1990.

## E NERGY

1.60 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-22 K ILN , O VENS , AND D RYERS E MISSION C ONTROLS P ERFORMANCE

Technology Efficiency Loss (a)

(%) CO Reduction (%) CH 4 Reduction (%) NO x Reduction (%) N 2 O Reduction (%) NMVOCs Reduction (%) Date Available (b)

LEA - Kilns, Dryers -6.4 + + 14 NAV NAV 1980 LNB - Kilns, Dryers 0 + + 35 NAV NAV 1985

SCR - Coke Oven 1.0 8 + 80 60 NAV 1979 Nitrogen Injection NAV NAV NAV 30 NAV NAV 1990 Fuel Staging NAV NAV NAV 50 NAV NAV 1995 (a) Efficiency loss as a percentage of end-user energy conversion efficiency (ratio of energy output to energy input for each technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement. (b) Date technology is assumed to be commercially available. Note: A "+" indicates negligible reduction. Source: Radian, 1990.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.61 T ABLE 1-23 R ESIDENTIAL AND C OMMERCIAL E MISSION C ONTROLS P ERFORMANCE

Technology Efficiency Loss (a)

(%) CO Reduction (%) CH 4 Reduction (%) NO x Reduction (%) N 2 O Reduction (%) NMVOCs Reduction (%) Date Available (b)

Catalytic Woodstove -44 90 90 -27 NAV NAV 1985 Non-Catalytic Modified Combustion Stove -30 15 50 -5 NAV NAV 1985

Flame Retention Burner Head -9 28 NAV NAV NAV NAV
Controlled Mixed Burner Head -7 43 NAV 44 NAV NAV

Integrated Furnace System -12 13 NAV 69 NAV NAV Blueray Burner/Furnace -12 74 NAV 84 NAV NAV
M.A.N. Burner -13 NAV NAV 71 NAV NAV 1980
Radiant Screens -7 62 NAV 55 NAV NAV Secondary Air Baffle NAV 16 NAV 40 NAV NAV
Surface Comb. Burner NAV 55 NAV 79 NAV NAV
Amana HTM -21 -55 NAV 79 NAV NAV Modulating Furnace -7 NAV NAV 32 NAV NAV
Pulse Combuster -36 NAV NAV 47 NAV NAV Catalytic Combuster -29 NAV NAV 86 NAV NAV Replace Worn Units NAV 65 NAV NAV NAV NAV Tuning, Seasonal Maintenance -2 16 NAV NAV NAV NAV Reduced Excessive Firing -19 14 NAV NAV NAV NAV Reduced Excessive Firing with New Retention Burner -40 14 NAV NAV NAV NAV

Positive Chimney Dampers -8 11 NAV NAV NAV NAV
Increased Thermostat Anticipator -1 43 NAV NAV NAV NAV

Night Thermostat Cutback -15 17 NAV NAV NAV NAV
Low Excess Air -0.8 NAV NAV 15 NAV NAV 1970
Flue Gas Recirculation 0.6 NAV NAV 50 NAV NAV 1975
Over-fire Air 1 NAV NAV 20-30 NAV NAV 1970
Low NO x Burners 0.6 NAV NAV 40-50 NAV NAV 1980 (a) Efficiency loss as a percentage of end-user energy conversion efficiency (ratio of energy output to energy input for each technology) due to the addition of an emission control technology. Negative loss indicates an efficiency improvement. (b) Date technology is assumed to be commercially available. Source: Radian, 1990.

## E NERGY

1.62 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-24 N ET C ALORIFIC V ALUES FOR P RECEDING T ABLES (a) ( THESE VALUES SHOULD NOT BE USED TO CALCULATE INVENTORIES , SEE NOTE BELOW )
Fuel Net Calorific Value (TJ/kilotonne)
GAS Butane 44.4 Propane 47.1 Natural Gas 52.3 LIQUID Crude Oil 40.9 Crude Shale Oil 42 Diesel/Distillate 42.9 Gasoline 46.5 Residual Oil 42 SOLID Bagasse/Agriculture 8.8 Bituminous Coal 28.7 Anthracite 27.2 Lignite 15.9 MSW 10.7 Wood 11.5 NOTE: These values are given for information only and refer to the preceding tables. They should not be used by countries to convert energy data to TJ for the inventories. The default net calorific values used in the **Guidelines** have not been changed and can be found in the **Reference Manual** Tables I-2 and 1-3. Source: US EPA (1995). (a) Values in preceding tables were originally based on gross calorific value; they were converted to net calorific value by assuming that net calorific values were 5 per cent lower than gross calorific values for coal and oil, and 10 per cent lower for natural gas. These percentage adjustments are the OECD/IEA assumption on how to convert from gross to net calorific values.



### 1.5.3 Mobile Combustion

1.5.3.1 O VERVIEW Emissions of greenhouse gases from mobile sources, including carbon dioxide (CO 2 ), carbon monoxide (CO), nitrogen oxides (NO x ), methane (CH 4 ), nitrous oxide (N 2 O) and non-methane volatile organic compounds (NMVOCs) are most easily estimated by major transport activity, i.e., road, air, rail, and ships

. However, as road transport and aviation account for the majority of mobile-source fuel consumption (e.g., 82 per cent in 1988 for the OECD), followed by air transport (about 13 per cent), greater priority has been attached to the development of emission models and inventories for road vehicles and aircraft. The diversity of the types of mobile source and the range of characteristics which affect emission factors are amply demonstrated by the tables included in this section for both road and air transport. Recent work has both updated and strengthened the data given and a fuller methodology for estimating aircraft emissions has been introduced based upon the EMEP/CORINAIR work in this field. Despite these advances more work is needed to fill in many gaps in knowledge of emissions from certain vehicle types and on

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.63 the effects of ageing on catalytic control of road vehicle emissions

. Equally, there is very little information on the appropriate emission factors for road transport in developing countries where age of fleet, maintenance and patterns of use are different from those in industrialised countries. It should be recalled that transport is a significant source of CO 2 emissions and emission factors for CO 2 emissions are provided in the following tables to permit the estimation of CO 2 at this detailed level.



### 1.5.3.2 R ECOMMENDED METHODOLOGY Estimation of mobile source emissions is a very complex undertaking that requires consideration of many parameters, including:

• transport class

• fuel consumed

• operating characteristics

• emission controls

• maintenance procedures

• fleet age The need for data on several parameters and the wide variety of conditions that can affect the performance of each category of mobile source makes it very difficult to generalise their emission characteristics. Also, within the transport sector, the primary measure of activity is less likely than in other sectors to be fuel consumption. The underlying general emissions model may be expressed as:

Emissions = ∑ (EF abc x Activity abc )

where: EF = emission factor Activity = amount of energy consumed or distance travelled for a given mobile source activity a = fuel type (diesel, gasoline, LPG, bunker, etc.) b = vehicle type (e.g., passenger, light-duty or heavy-duty for road vehicles)
c = emission control which implies the following steps:

• Determine the amount of energy consumed by fuel type for the major transport modes using national data or, as an alternative, IEA or UN international data sources (all values should be reported in terajoules).

• For each fuel type, determine the amount of energy that is consumed by each vehicle type, e.g., light-duty gasoline vehicles, etc. (all units are in terajoules)

. If distance travelled is the activity measure, determine the total distance travelled by each vehicle type

. In this case, the energy consumption associated with these distance travelled figures should be calculated and aggregated by fuel for comparison

## E NERGY

1.64 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual with national energy balance figures

. If necessary, further subdivide each vehicle type into uncontrolled and key classes of emission control technology.

• Multiply the amount of energy consumed, or the distance travelled by each category of vehicle or vehicle/control technology, by the appropriate emission factor for that category

. Data presented in the next section (Emission Factors) can be used as a starting point

. However, national experts are encouraged to consult other data sources referenced in this chapter or locally available data before determining appropriate factors for a particular country.

• Emissions of each pollutant can be summed across all categories of fuel and technology type, including for all levels of emission control, to determine total emissions from mobile source-related activities.

Emission Factors The tables given for road transport summarise results of a detailed analysis of mobilesource emission factors covering North American and European vehicles and conditions. Recently published work has permitted the updating of figures appearing in the 1995 edition of the Guidelines. The US emission factors for mobile sources, published in the 1995 edition, were developed using the MOBILE4 model. This was one of a series of emissions models developed and periodically updated by the US Environmental Protection Agency for use in its analysis of motor vehicle regulatory and policy issues

. The MOBILE4 model is now out of date. Since the analysis done in 1991, several improvements have been based on new information and vehicle testing results. Emission factors developed using the latest version of the MOBILE model (MOBILE5a) are higher for most pollutants. The US tables included here contain this latest information.
CO 2 factors are derived from the carbon content of the fuels and therefore include the carbon present in other carbon molecule based emissions. The European data are drawn from the CORINAIR COPERT model. However, for actual calculations of national emissions, users are encouraged to also consult a range of recent and more detailed information sources (see Data Sources in Section 1.5.1)

. Particularly for indirect GHGs, more comprehensive sources are available based on programmes outside the GHG emissions area. Emission factor estimates are presented for CO 2 , CO, NO x , N 2 O, CH 4 and NMVOCs for several classes of non-road vehicles - railway locomotives, ships and boats, farm and construction equipment. This section on mobile sources also contains a more comprehensive explanation of a methodology for the estimation of emissions from aircraft and greater specificity of aircraft/engine emission factors for NO x . All emission factor data are stated on the basis of full molecular weight of the respective pollutant; NO x factors are stated as NO 2 . Emission Factors for Mobile Sources in Developing Countries In highly populated developing countries the estimated emissions per kilometre travelled should be altered. First, there are virtually no catalytic converters on the vehicles

. Second, the number of accelerations and decelerations that the vehicle will undergo is much larger than for corresponding travel in countries that are less populated and have well arranged highway systems. The measured pollutant value of NO x in an engine at constant rpm conditions is about 1.0 g/MJ for the United States and for Europe. However, for highly populated developing countries 1.8 g/MJ should be used.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.65 Further information on emission factors for developing countries is available from Riveros et. al (1995), Bose (1996) and other sources listed in the bibliography.



### 1.5.3.3 R OAD 

### V EHICLES

United States Emission Estimates Technical Approach
The US emissions estimates for NO x , CO, CH 4 and NMVOC from highway vehicles were developed directly from the US EPA’s MOBILE5a model. The model calculates exhaust emission factors for gasoline and diesel fuelled US vehicles, based on the year in which they were manufactured. For gasoline vehicles, it also calculates VOC emissions due to evaporative, running and refuelling losses (VOC emissions from diesel vehicles due to these causes are negligible). Assumptions To develop emission estimates for different control technology types, calculations were carried out for specific model years during which US vehicles were equipped with the technology in question

. Table 1-25 shows the correspondence between the technology types and the US model years used to represent them in the model. Average lifetime emissions were calculated for each vehicle type based on their assumed lifetimes. The model uses a two-step linear function to estimate deterioration rates from vehicle mileage

. Linear equations are fitted to vehicle emission estimates at 0 and 50 000 miles and 50 000 and 100 000 miles and from the results lifetime average factors were calculated. The emission factors calculated by MOBILE5a are affected by assumptions regarding average speeds, ambient temperature, diurnal temperature range, altitude and fuel volatility that are provided to the model. They are also affected by the assumed presence or absence of inspection/maintenance (I/M) programmes and anti-tampering programmes as well as the type of I/M programme used. The model calculates emission factors using three seasonal conditions: Spring/Fall, Winter and Summer. The model was also run with three different I/M scenarios; no I/M programme, basic I/M and enhanced I/M. Where I/M influences emissions, the emission factors given in the tables included here are shown as range estimates with the lower value representing the enhanced I/M and the upper value reflecting no I/M. Since there is no I/M programme for diesel vehicles in the United States the diesel vehicle emission factors generated by the model for different I/M programmes were the same. The average speed assumed by the model is 31.4 km/h - typical of uncongested urban driving (see Table 1

**-** 26).

## E NERGY

1.66 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-25 E MISSION C ONTROL T ECHNOLOGY T YPES AND US V EHICLE M ODEL Y EARS U SED TO R EPRESENT T HEM Technology Model Year Gasoline Passenger Cars and Light Trucks
Uncontrolled 1964 Non-catalyst controls 1973 Oxidation catalyst 1978 Early three-way catalyst 1983 Three-way catalyst 1996 Heavy-Duty Gasoline Vehicles
Uncontrolled 1968 Non-catalyst control 1983 Three-way catalyst 1996 Diesel Passenger Cars and Light Trucks
Uncontrolled 1978
Moderate control 1983
Advanced control 1996 Heavy-Duty Diesel Vehicles
Uncontrolled 1968
Moderate control 1983
Advanced control 1996 Motorcycles
Uncontrolled 1973 Non-catalyst controls 1996

T ABLE 1-26 A SSUMED A MBIENT T EMPERATURE , D IURNAL R ANGE AND R EID V APOUR P RESSURE FOR D IFFERENT S EASONS
Ambient Temperature ( ° C) Diurnal Range ( ° C) Reid Vapour Pressure (kPa)

Spring/Fall 16 7 to 24 62
Winter 2 -7 to 10 103
Summer 29 21 to 38 54

The estimated vehicle fuel economies were also used to calculate fuel specific and energy specific emission factors for all of the pollutants

. Energy specific emission factors were based on the net calorific value of the fuel in each case

. Since emission and fuel consumption tend to vary in parallel (vehicles and operating modes causing high emission rates also tend to result in high fuel consumption, and vice-versa) these energy specific emission factors are expected to be more generally applicable than the factors in grams per kilometre and their use is to be preferred.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.67 B OX 4 L IMITATIONS OF M OBILE 5 A R ESULTS Emission factors for many greenhouse gases from road vehicles have been developed using the MOBILE5a Model (a) as presented in Tables 1-27 to 1-33. This model is one of a series of emissions models developed and periodically updated by the US Environmental Protection Agency for use in its analysis of motor vehicle regulatory and policy issues. The model has been used to derive average emission factors for NO x , CO, and NMVOC by class of vehicle and for gasoline and diesel fuel. Calculations for other gases and for alternative fuels were done separately. All “global” average emission factors like these should be considered illustrative and should not be directly used in national emissions calculations. Such values are by necessity based on “global” average assumptions in several key areas. Average emission factors by class of vehicle are sensitive to very specific assumptions including those about

• vehicle models, average age and accumulated mileage

• per cent driving in cold start, hot start and stabilised conditions

• average driving speed

• ambient temperature

• fuel comparison

• rates of tampering with control systems

• proper maintenance Obviously, many of these assumed conditions will vary significantly from country to country and even by region within countries. For example, the light-duty gasoline vehicle class does not include two-stroke engines, which are not used in the United States, but are important in Central and Eastern Europe. Therefore, “global” illustrative factors should not be used to calculate actual emissions in a specific country. For the above reasons, illustrative emission factors should not be directly used for national calculations. National inventory experts should consult the more detailed references on mobile source emission factors and use these sources to develop or adapt emission factors which are appropriate for their specific conditions. The expert group on GHG emissions from fuel combustion has identified the need for more detailed guidance and assistance to national experts on the development of locally applicable emission factors as a priority for future work.
(a) The MOBILE5a Model and its User Guide can be obtained from Terry Newell, US EPA Office of Mobile Sources, 2565 Plymouth Road, Ann Arbor MI 48105, USA; tel: (313) 668-4462, Email: Newell.Terry@epamail.epa.gov or access the latest information on mobile sources on the world wide web at http://www.epa.gov/OMSWWW/omshome.htm.

N 2 O emission from internal combustion engines is not well understood and data on emissions are scarce. The 1995 edition of the Guidelines contained supplementary information used by the Canadian Government, based on a review of data available in 1994 (Ballantyne et al., 1994). The Canadian estimates show that N 2 O emissions from vehicles with three-way catalysts increased markedly during the first 15 to 20 000 km, so that earlier estimates based on tests of low mileage vehicles are too low

. These results are summarised in Box 5

. The US tables, included in this section, use the Canadian data to estimate N 2 O emissions from gasoline passenger cars

. For light-duty gasoline trucks and motorcycles, fuel specific N 2 O emissions were assumed to be the same as for the corresponding passenger car technology

. N 2 O emissions per kilometre were then

## E NERGY

1.68 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual calculated from the fuel specific emissions and the fuel consumption characteristics for each class. In the absence of direct data, N 2 O emissions from heavy-duty gasoline trucks were estimated by assuming that their fuel specific emissions were similar to those for passenger cars with similar technology

. N 2 O emission factors for heavy-duty diesel trucks were derived from emissions for these vehicles reported by Dietzmann, Parness and Bradow (1980). The corresponding fuel specific emission rates were used to estimate N 2 O emissions from light-duty diesel vehicles in the absence of information on this class.

B OX 5 R ECENT I NFORMATION ON N 2 O M EASUREMENTS Since the initial illustrative emission factors were estimated in 1991, a number of measurement studies have been carried out to improve understanding of vehicle N 2 O emissions. A paper by Ballantyne, et al., (1994) summarised measurements in Canada, the United States and Europe.
Canadian US Measurements European Values Used in Measurements (Dasch, 1992) Measurements Canadian (Ballantyne, et al., (De Soete, 1989) National Inventory 1994) mg/miles g/km mg/miles g/km mg/miles g/km mg/miles g/km New three-way catalysts 21-126 0.013-0.078 13-101 0.008-0.06 60-170 0.037-0.106 60 0.04 Aged three-way 72-211 0.045-0.131 - - 260-356 0.162-0.221 280 0.17
Oxidation catalyst - - 3-66 0.002-0.04 120 0.075 120 0.075 No catalyst - - 2.4-4.8 0.001-0.003 8-32 0.005-0.02 32 0.02
Results of this analysis are presented by categories defined by the US EPA as listed below: **Table 1-27: Light-duty gasoline passenger cars** - vehicles with rated gross weight less than 8 500 lb (3 855 kg) designed primarily to carry 12 or fewer passengers . Six levels of gasoline-vehicle control technology are shown: 1 Uncontrolled (still typical of most vehicles around the world).2 Non-catalyst emission controls - including modifications to ignition timing and airfuel ratio to reduce emissions, exhaust gas recirculation (EGR), and air injection into the exhaust manifold. 3 Oxidation catalyst systems normally including many of the same techniques, plus a two-way catalytic converter to oxidise hydrocarbons and CO. 4 "Early" three-way catalyst results representative of vehicles sold in the United States in the early to mid-1980s, which were mostly equipped with carburettors having electronic "trim". 5 "Advanced" three-way catalyst values based on current US technology vehicles, using electronic fuel injection under computer control. 6 Low Emission Vehicles (LEV) are expected to include sequential multi-port fuel injection with adaptive learning, more sophisticated computer diagnostics and heated catalysts with secondary air injection. **Table 1-28: Light-duty gasoline trucks** - vehicles having rated gross vehicle weight less than 8 500 lb (3 855 kg), and which are designed primarily for transportation of cargo or

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.69 more than 11 passengers at a time, or which are equipped with special features for offroad operation. They include most pickup trucks, passenger and cargo vans, four-wheel drive vehicles, and derivatives of these

. The technology classifications used are the same as those for gasoline passenger vehicles. **Table 1-29: Heavy-duty gasoline vehicles** - manufacturer's gross vehicle weight rating exceeding 8 500 lb (3 855 kg)

. This includes large pickups, vans and specialised trucks using pickup and van chassis, as well as the larger "true" heavy-duty trucks, which have gross vehicle weights of eight short tons or more

. In the United States, the large pickups and vans in this category greatly outnumber the heavier trucks, so that the emission factors calculated by MOBILE5a, and fuel economy estimates, are more representative of these vehicles

. Three levels of emission control technology are shown:
1 Uncontrolled

. 2 Non-catalyst emission controls, including control of ignition timing and air-fuel ratio to minimise emissions, EGR, and air injection into the exhaust manifold to reduce hydrocarbons and CO emissions

. 3 Three-way catalyst technology presently used in the United States includes electronically-controlled fuel injection, EGR, air injection, and electronic control of ignition timing, as well as the catalyst itself. **Table 1-30: Light-duty diesel passenger cars** - a diesel passenger car designed primarily to carry fewer than 12 passengers, with gross vehicle weight less than 8 500 lb (3 855 kg)

. Three levels of emission control technology are shown:
1 Uncontrolled. 2 Moderate emissions control (achieved by changes in injection timing and combustion system design)

. 3 Advanced emissions control utilising modern electronic control of the fuel injection system, and exhaust gas recirculation. **Table 1-31: Light-duty diesel trucks** - light-duty diesel trucks defined like their gasoline counterparts, including weight, utility, and off-road operation features

. The technology classifications are the same as those for diesel passenger cars. **Table 1-32: Heavy-duty diesel vehicles** - the classification for heavy-duty diesel vehicles is the same as for gasoline vehicles, but the characteristics of US vehicle fleets are different

. Heavy-duty diesel vehicles are primarily large trucks, with gross vehicle weight ratings of 10 to 40 tons

. Therefore, the MOBILE5a emission factors are more representative of large trucks (and buses) than the smaller pickup and van-type vehicles, and this is reflected in the fuel economy estimates

. Three levels of control are presented:
1 Uncontrolled

. 2 Moderate control (typical of 1983 US engines). 3 Advanced control (for engines meeting US 1991 emissions standards)

. **Table 1-33: Motorcycles** - The MOBILE5a emission factors for these vehicles are based on the US motorcycle population, which probably reflects higher average power ratings and fuel consumption than for many developing countries

. The factors for uncontrolled motorcycles include a mixture of two-stroke and four-stroke engines, with the VOC emissions due primarily to the two-strokes, and the NO x to the four-stroke engines

. The factors for motorcycles with non-catalyst emission controls reflect four-stroke engines only, as US emission control regulations have essentially eliminated two-stroke engines from the market

.

## E NERGY

1.70 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-27 E STIMATED E MISSION F ACTORS F OR US G ASOLINE P ASSENGER C ARS EMISSIONS Season NO x CH 4 NMVOC CO N 2 O CO 2 Low-Emission Vehicle Technology; (a) Assumed Fuel Economy: 8.5 km/litre (11.8 l/100 km) Spring/Fall 0.26-0.34 0.02-0.03 0.30-0.46 3.15-5.30 - - Summer 0.25-0.32 0.02-0.03 0.32-0.47 2.69-4.67 - - Winter 0.31-0.39 0.03-0.04 0.29-0.51 4.78-7.60 - - Average (g/km) 0.27-0.34 0.02-0.03 0.30-0.47 3.44-5.72 0.040 280 Average (g/kg fuel) 3.07-3.91 0.25-0.38 3.42-5.35 38.96-64.77 0.453 3172.31 Average (g/MJ) 0.070-0.089 0.006-0.009 0.078-0.122 0.885-1.472 0.010 72.098 Three-Way Catalyst Control; (a) Assumed Fuel Economy: 8.3 km/litre (12.0 l/100 km) Spring/Fall 0.41-0.48 0.02-0.03 0.49-0.66 3.62-5.78 - - Summer 0.39-0.46 0.02-0.03 0.80-0.95 2.90-4.89 - - Winter 0.47-0.56 0.03-0.04 0.37-0.60 6.35-9.14 - - Average (g/km) 0.42-0.50 0.03 0.54-0.72 4.12-6.40 0.170 285 Average (g/kg fuel) 4.67-5.53 0.28-0.39 6.00-7.99 45.92-71.22 1.892 3172.31 Average (g/MJ) 0.106-0.126 0.006-0.009 0.136-0.182 1.044-1.619 0.043 72.098 Early Three-Way Catalyst; (a) Assumed Fuel Economy: 8.0 km/litre (12.5 l/100 km) Spring/Fall 0.41-0.51 0.03-0.04 0.63-0.81 4.77-7.08 - - Summer 0.39-0.49 0.03-0.04 1.44-1.62 4.46-6.87 - - Winter 0.50-0.63 0.04-0.06 0.45-0.70 7.75-10.42 - - Average (g/km) 0.43-0.54 0.03-0.05 0.79-0.99 5.44-7.86 0.170 298 Average (g/kg fuel) 4.55-5.71 0.37-0.48 8.41-10.52 57.93-83.73 1.810 3172.31 Average (g/MJ) 0.103-0.130 0.008-0.011 0.191-0.239 1.317-1.903 0.041 72.098 Oxidation Catalyst; Assumed Fuel Economy: 6.2 km/litre (16.1 l/100 km) Spring/Fall 1.10-1.17 0.05-0.07 1.26-1.76 8.79-14.96 - - Summer 0.84-0.90 0.06-0.08 2.58-3.25 12.16-20.79 - - Winter 1.29-1.38 0.07-0.09 1.07-1.66 12.28-19.72 - - Average (g/km) 1.08-1.16 0.06-0.08 1.54-2.11 10.51-17.61 0.075 383 Average (g/kg fuel) 8.97-9.58 0.50-0.63 12.77-17.48 87.08-145.95 0.622 3172.31 Average (g/MJ) 0.204-0.218 0.011-0.014 0.290-0.397 1.979-3.317 0.014 72.098 Non-Catalyst Control; Assumed Fuel Economy: 4.5 km/litre (22.2 l/100 km) Spring/Fall 1.33-1.37 0.10-0.12 1.97-2.36 14.76-21.63 - - Summer 1.06-1.09 0.11-0.13 4.06-4.61 20.59-30.70 - - Winter 1.35-1.40 0.13-0.15 1.62-2.05 17.53-26.09 - - Average (g/km) 1.27-1.31 0.11-0.13 2.41-2.84 16.91-25.01 0.020 531 Average (g/kg fuel) 7.56-7.82 0.65-0.75 14.38-17.00 101.06-149.45 0.125 3172.31 Average (g/MJ) 0.172-0.178 0.015-0.017 0.327-0.386 2.297-3.397 0.003 72.098 Uncontrolled; Assumed Fuel Economy: 4.7 km/litre (21.3 l/100 km) Spring/Fall 1.54 0.12-0.14 5.72-6.06 28.23-38.04 - - Summer 1.31 0.11-0.12 9.76-10.07 28.22-38.04 - - Winter 1.83 0.16-0.17 4.24-4.66 30.89-41.63 - - Average (g/km) 1.56 0.13-0.14 6.36-6.71 28.89-38.94 0.020 506 Average (g/kg fuel) 9.76 0.82-0.90 39.88-42.09 181.14-244.14 0.130 3172.31 Average (g/MJ) 0.222 0.019-0.020 0.906-0.957 4.117-5.549 0.003 72.098 (a) Recent measurement results (De Soete, 1993, Ballantyne, et al., 1994) have shown that N 2 O emissions from aged catalysts, e.g., tested after driving 15 000 - 25 000 km, are substantially higher than from new catalyst-equipped cars. Tests on comparable models show aged catalysts emitting from roughly 30% more to almost 5 times the rate of new equipment. As indicated in Box 5, Environment Canada has used a value almost 5 times as high for aged catalysts in its national inventory calculations.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.71 T ABLE 1-28 E STIMATED E MISSION F ACTORS FOR US L IGHT - DUTY G ASOLINE T RUCKS . EMISSIONS Season NO x CH 4 NMVOC CO N 2 O CO 2 Low-Emission Vehicle Technology; (a) Assumed Fuel Economy: 6.0 km/litre (16.7 l/100 km) Spring/Fall 0.31-0.40 0.02-0.04 0.30-0.50 3.57-6.03 - - Summer 0.29-0.38 0.02-0.03 0.31-0.50 2.87-5.11 - - Winter 0.37-0.47 0.03-0.05 0.34-0.62 6.02-9.33 - - Average (g/km) 0.32-0.41 0.02-0.04 0.31-0.53 4.01-6.62 0.058 396 Average (g/kg fuel) 2.50-3.23 0.18-0.29 2.43-4.13 31.30-51.71 0.450 3172.31 Average (g/MJ) 0.057-0.073 0.004-0.007 0.055-0.094 0.711-1.175 0.010 72.098 Three-Way Catalyst Control; (a) Assumed Fuel Economy: 6.0 km/litre (16.7 l/100 km) Spring/Fall 0.49-0.59 0.02-0.04 0.47-0.69 4.45-7.08 - - Summer 0.47-0.56 0.02-0.03 0.66-0.87 3.64-6.05 - - Winter 0.57-0.69 0.04-0.05 0.47-0.77 7.68-11.22 - - Average (g/km) 0.50-0.61 0.03-0.04 0.52-0.76 5.06-7.86 0.236 396 Average (g/kg fuel) 4.04-4.86 0.21-0.30 4.14-6.06 40.46-62.87 1.890 3172.31 Average (g/MJ) 0.092-0.111 0.005-0.007 0.094-0.138 0.920-1.429 0.043 72.098 Early Three-Way Catalyst; (a) Assumed Fuel Economy: 4.8 km/litre (20.8 l/100 km) Spring/Fall 0.63-0.76 0.05-0.07 0.74-1.04 6.49-9.97 - - Summer 0.60-0.73 0.05-0.07 1.34-1.65 5.97-9.52 - - Winter 0.76-0.93 0.08-0.10 0.76-1.19 9.58-13.54 - - Average (g/km) 0.65-0.80 0.06-0.08 0.90-1.23 7.13-10.75 0.227 396 Average (g/kg fuel) 5.23-6.36 0.47-0.63 7.16-9.82 56.96-85.86 1.810 3172.31 Average (g/MJ) 0.119-0.144 0.011-0.014 0.163-0.223 1.294-1.951 0.041 72.098 Oxidation Catalyst; Assumed Fuel Economy: 4.8 km/litre (20.8 l/100 km) Spring/Fall 1.15-1.28 0.07-0.09 1.48-2.31 9.56-18.76 - - Summer 0.77-0.86 0.09-0.11 2.70-3.85 13.72-27.86 - - Winter 1.34-1.50 0.10-0.12 1.30-2.30 13.47-26.33 - - Average (g/km) 1.10-1.23 0.08-0.10 1.74-2.69 11.58-22.93 0.097 498 Average (g/kg fuel) 7.03-7.84 0.52-0.66 11.08-17.16 73.77-146.07 0.620 3172.31 Average (g/MJ) 0.160-0.178 0.012-0.015 0.252-0.390 1.677-3.320 0.014 72.098 Non-Catalyst; Assumed Fuel Economy: 4.0 km/litre (25.0 l/100 km) Spring/Fall 1.62-1.68 0.12-0.14 3.09-3.55 18.41-27.08 - - Summer 1.28-1.32 0.13-0.15 5.80-6.39 23.76-35.80 - - Winter 1.67-1.72 0.15-0.17 2.29-2.83 23.08-34.24 - - Average (g/km) 1.55-1.60 0.13-0.15 3.57-4.08 20.92-31.05 0.023 601 Average (g/kg fuel) 8.17-8.45 0.69-0.80 18.85-21.55 110.41-163.90 0.120 3172.31 Average (g/MJ) 0.186-0.192 0.016-0.018 0.428-0.490 2.509-3.725 0.003 72.098 Uncontrolled; Assumed Fuel Economy: 4.1 km/litre (24.4 l/100 km) Spring/Fall 1.84 0.12-0.14 6.87-7.24 29.92-40.29 - - Summer 1.56 0.11-0.12 11.07-11.41 29.91-40.29 - - Winter 2.18 0.16-0.17 5.31-5.77 33.17-44.09 - - Average (g/km) 1.85 0.13-0.14 7.53-7.92 30.73-41.24 0.024 579 Average (g/kg fuel) 10.16 0.71-0.79 41.26-43.37 168.36-225.95 0.130 3172.31 Average (g/MJ) 0.231 0.016-0.018 0.938-0.986 3.826-5.135 0.003 72.098 (a) Recent measurement results (De Soete, 1993, Ballantyne, et al., 1994) have shown that N 2 O emissions from aged catalysts, e.g., tested after driving 15 000 - 25 000 km, are substantially higher than from new catalyst-equipped cars. Tests on comparable models show aged catalysts emitting from roughly 30% more to almost 5 times the rate of new equipment. As indicated in Box 5, Environment Canada has used a value almost 5 times as high for aged catalysts in its national inventory calculations.

## E NERGY

1.72 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-29 E STIMATED E MISSION F ACTORS F OR US H EAVY -D UTY G ASOLINE V EHICLES
EMISSIONS
Season NO x CH 4 NMVOC CO N 2 O CO 2 Three-Way Catalyst Control; (a) Assumed Fuel Economy: 2.3 km/litre (43.5 l/100 km) Spring/Fall 1.69-1.74 0.07-0.08 0.88-1.03 6.06-7.49 - -
Summer 1.76-1.81 0.07 1.64-1.80 6.22-7.67 - -
Winter 1.81-1.86 0.07-0.08 0.65-0.79 6.75-8.35 - - Average (g/km) 1.74-1.78 0.07-0.08 1.01-1.16 6.27-7.75 0.606 1017 Average (g/kg fuel) 5.42-5.56 0.21-0.24 3.17-3.62 19.57-24.19 1.890 3172.31 Average (g/MJ) 0.123-0.126 0.005 0.072-0.082 0.445-0.550 0.043 72.098 Non-Catalyst Control; Assumed Fuel Economy: 2.3 km/litre (43.5 l/100 km) Spring/Fall 2.37-2.39 0.12-0.13 3.97-4.20 27.04-32.15 - -
Summer 1.85-1.88 0.12-0.13 9.92-10.20 40.28-47.89 - -
Winter 2.54-2.56 0.12-0.13 1.71-1.97 30.12-35.81 - - Average (g/km) 2.28-2.31 0.12-0.13 4.89-5.14 31.12-37.00 0.591 1036 Average (g/kg fuel) 6.98-7.06 0.36-0.41 14.98-15.75 95.28-113.28 1.810 3172.31 Average (g/MJ) 0.159-0.161 0.008-0.009 0.341-0.358 2.166-2.575 0.041 72.098 Uncontrolled; Assumed Fuel Economy: 1.8 km/litre (55.6 l/100 km) Spring/Fall 3.48-4.13 0.26-0.29 13.38-14.55 97.66-115.91 - -
Summer 2.83-3.38 0.25-0.29 19.97-21.11 111.10-131.87 - -
Winter 4.11-4.88 0.26-0.29 12.01-13.38 103.06-122.33 - - Average (g/km) 3.47-4.13 0.25-0.29 14.68-15.90 102.37-121.51 0.054 1320 Average (g/kg fuel) 8.35-9.92 0.61-0.70 35.30-38.21 246.08-292.08 0.130 3172.31 Average (g/MJ) 0.190-0.226 0.014-0.016 0.802-0.868 5.593-6.638 0.003 72.098 (a) Recent measurement results (De Soete, 1993, Ballantyne, et al., 1994) have shown that N 2 O emissions from aged catalysts, e.g., tested after driving 15 000 - 25 000 km, are substantially higher than from new catalyst-equipped cars. Tests on comparable models show aged catalysts emitting from roughly 30% more to almost 5 times the rate of new equipment. As indicated in Box 5, Environment Canada has used a value almost 5 times as high for aged catalysts in its national inventory calculations.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.73 T ABLE 1-30 E STIMATED E MISSION F ACTORS F OR US D IESEL P ASSENGER C ARS
EMISSIONS
Season NO x CH 4 NMVOC CO N 2 O CO 2 Advanced Control; Assumed Fuel Economy: 10.0 km/litre (10 l/100 km) Spring/Fall 0.42 0.01 0.17 0.56

- - Summer 0.42 0.01 0.17 0.56

- - Winter 0.44 0.01 0.19 0.58

- - Average (g/km) 0.43 0.01 0.17 0.56 0.007 237 Average (g/kg fuel) 5.68 0.06 2.32 7.54 0.09 3172.31 Average (g/MJ) 0.129 0.001 0.053 0.171 0.002 72.098 Moderate Control; Assumed Fuel Economy: 9.6 km/litre (10.4 l/100 km) Spring/Fall 0.54 0.01 0.17 0.56

- - Summer 0.54 0.01 0.17 0.62

- - Winter 0.54 0.01 0.17 0.56

- - Average (g/km) 0.54 0.01 0.17 0.58 0.01 248 Average (g/kg fuel) 6.88 0.08 2.17 7.35 0.13 3172.31 Average (g/MJ) 0.156 0.002 0.049 0.167 0.003 72.098 Uncontrolled; Assumed Fuel Economy: 7.5 km/litre (13.3 l/100 km) Spring/Fall 0.67 0.01 0.24 0.61

- - Summer 0.67 0.01 0.24 0,.61

- - Winter 0.67 0.01 0.24 0.61

- - Average (g/km) 0.67 0.01 0.24 0,.61 0.014 319 Average (g/kg fuel) 6.62 0.12 2.39 6.04 0.14 3172.31 Average (g/MJ) 0.150 0.003 0.054 0.137 0.003 72.098

## E NERGY

1.74 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-31 E STIMATED E MISSION F ACTORS F OR US L IGHT -D UTY D IESEL T RUCKS
EMISSIONS
Season NO x CH 4 NMVOC CO N 2 O CO 2 Advanced Control; Assumed Fuel Economy: 7.2 km/litre (13.9 l/100 km) Spring/Fall 0.49 0.01 0.24 0.64 - -
Summer 0.49 0.01 0.24 0.64 - -
Winter 0.49 0.01 0.24 0.64 - - Average (g/km) 0.49 0.01 0.24 0.64 0.024 330 Average (g/kg fuel) 4.70 0.08 2.35 6.11 0.23 3172.31 Average (g/MJ) 0.107 0.002 0.053 0.139 0.005 72.098 Moderate Control; Assumed Fuel Economy: 7.2 km/litre (13.9 l/100 km) Spring/Fall 0.68 0.01 0.24 0.64 - -
Summer 0.68 0.01 0.24 0.64 - -
Winter 0.68 0.01 0.24 0.64 - - Average (g/km) 0.68 0.01 0.24 0.64 0.063 331 Average (g/kg fuel) 6.52 0.08 2.34 6.10 0.60 3172.31 Average (g/MJ) 0.148 0.002 0.053 0.139 0.014 72.098 Uncontrolled; Assumed Fuel Economy: 5.7 km/litre (17.5 l/100 km) Spring/Fall 0.92 0.01 0.49 1.01 - -
Summer 0.92 0.01 0.49 1.01 - -
Winter 0.92 0.01 0.49 1.01 - - Average (g/km) 0.92 0.01 0.49 1.01 0.031 415 Average (g/kg fuel) 7.02 0.10 3.76 7.73 0.24 3172.31 Average (g/MJ) 0.159 0.002 0.086 0.176 0.005 72.098

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.75 T ABLE 1-32 E STIMATED E MISSION F ACTORS FOR US H EAVY D UTY D IESEL V EHICLES EMISSIONS
Season NO x CH 4 NMVOC CO N 2 O CO 2 Advanced Control; Assumed Fuel Economy: 2.4 km/litre (41.7 l/100 km) Spring/Fall 3.52 0.04 0.86 4.36

- - Summer 3.52 0.04 0.86 4.36

- - Winter 3.52 0.04 0.86 4.36

- - Average (g/km) 3.52 0.04 0.86 4.36 0.025 987 Average (g/kg fuel) 11.32 0.14 2.78 14.01 0.08 3172.31 Average (g/MJ) 0.257 0.003 0.063 0.318 0.002 72.098 Moderate Control; Assumed Fuel Economy: 2.4 km/litre (41.7 l/100 km) Spring/Fall 7.96 0.05 1.13 5.01

- - Summer 7.96 0.05 1.13 5.01

- - Winter 7.96 0.05 1.13 5.01

- - Average (g/km) 7.96 0.05 1.13 5.01 0.025 1011 Average (g/kg fuel) 24.96 0.16 3.55 15.71 0.08 3172.31 Average (g/MJ) 0.567 0.004 0.081 0.357 0.002 72.098 Uncontrolled; Assumed Fuel Economy: 2.2 km/litre (45.5 l/100 km) Spring/Fall 10.30 0.06 1.63 4.85

- - Summer 10.30 0.06 1.63 4.85

- - Winter 10.30 0.06 1.63 4.85

- - Average (g/km) 10.30 0.06 1.63 4.85 0.031 1097 Average (g/kg fuel) 29.79 0.18 4.70 14.03 0.09 3172.31 Average (g/MJ) 0.677 0.004 0.107 0.319 0.002 72.098

T ABLE 1-33 E STIMATED E MISSION F ACTORS F OR US M OTORCYCLES EMISSIONS
Season NO x CH 4 NMVOC CO N 2 O CO 2 Non-catalytic Control; Assumed Fuel Economy: 10.8 km/litre (9.3 l/100 km) Spring/Fall 0.37 0.12 2.26 13.77 - -
Summer 0.31 0.12 2.59 16.74 - -
Winter 0.43 0.14 2.47 18.01 - - Average (g/km) 0.37 0.13 2.39 15.57 0.002 219 Average (g/kg fuel) 5.40 1.83 36.60 225.14 0.03 3172.31 Average (g/MJ) 0.123 0.042 0.786 5.117 0.001 72.098 Uncontrolled; Assumed Fuel Economy: 8.9 km/litre (11.2 l/100 km) Spring/Fall 0.19 0.25 5.87 21.78 - -
Summer 0.16 0.24 5.96 21.55 - -
Winter 0.22 0.31 6.93 24.09 - - Average (g/km) 0.19 0.26 6.16 22.30 0.002 266 Average (g/kg fuel) 2.29 3.13 73.33 265.51 0.02 3172.31 Average (g/MJ) 0.052 0.071 1.667 6.034 0.001 72.098

## E NERGY

1.76 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual European Emission Estimates The European emission estimates for NO x , CH 4 , NMVOC (total VOC minus CH 4 ), CO, N 2 O and CO 2 are based on the COPERT90 model, developed for the Commission of the European Communities. 19 The calculation is based on five main types of input parameters:

• total fuel consumption

• vehicle park

• driving condition

• emission factors

• other parameters For these main types of input parameters, additional information (e.g., on vehicle classes, production years etc.) is needed in order to carry out the calculations. The methodology is defined in such a way that it uses the firm technical data and that national variations among European countries can be incorporated. The variations may include such things as composition of vehicle park, vehicle age, driving patterns, some fuel parameters and a few climatic parameters. Other variations which may exist, for example, variations in vehicle maintenance, mountain driving etc., are not accounted for because there is not enough data available to do so. Vehicle categories The vehicle categories chosen by CORINAIR 1990 do not meet all the requirements for modelling vehicle emissions considered important by the working group. In particular the age of vehicle (year of production) and the engine technology are not sufficiently reflected. Thus, for the purpose of the COPERT work only, a more detailed vehicle category split has been developed.

Hot Emissions These emissions depend on a variety of factors including the distance that each vehicle travels, its speed (or road type), its age and engine size. The basic formula for estimating hot emissions using an experimentally obtained emission factor is:
Emissions [g] = emission factor [g/km] . vehicle kilometres per year [km] The emission factors and vehicle kilometres are in most cases split into certain classes of road types and vehicle categories. However, for many countries the only data known with any certainty are the total fuel consumption of gasoline, diesel and LPG, not vehicle kilometres. It is therefore suggested that fuel consumption data are used to check vehicle mileage where they are known and to make a final fuel balance.

Cold Start Emissions Cold starts result in additional emissions. They take place under all three (urban, rural and highway) driving conditions, but seem to be most significant for urban driving. In

19 As is the convention throughout these Guidelines , CO 2 emissions are calculated to include the carbon emitted as CO and as VOC.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.77 principle they occur for all vehicle categories. However, emission factors are available or can be reasonably estimated only for gasoline, diesel and LPG passenger cars and - assuming that these vehicles behave like passenger cars - light-duty vehicles

. Consequently, only these categories are covered by the methodology. Moreover, cold start emissions are considered not to be a function of vehicle age.
Cold start emissions are calculated as emissions additional to emissions that would be expected if all vehicles had only hot engines. A factor, the ratio of cold to hot emissions, is used and applied to the fraction of kilometres driven with cold engines. These factors may vary from country to country. Different driving behaviour, road conditions and climate as well as trip length affect the warm up time and the fraction of distance travelled with cold engines. These factors can be taken into account, but again information may not be available to do this thoroughly in all countries, so that estimates have to close identified gaps. Evaporative VOC Emissions There are three primary sources of evaporative emissions from vehicles: i) diurnal (daily) emissions; ii) hot soak emissions; and iii) running losses. These are estimated separately. Again they are affected by factors that vary from country to country. All three types of evaporative emissions are significantly affected by the volatility of the gasoline being used, the absolute ambient temperature and temperature changes, and vehicle design characteristics. For hot soak emissions and running losses the driving pattern is also of importance. In general, the estimation of evaporative emissions from gasoline vehicles involves a large number of uncertainties which can not be resolved without carrying out further
measurements. Application of the baseline methodology to the different vehicle categories and pollutants Due to gaps in knowledge, the baseline methodology can not be applied in full and in the same way to all vehicle categories. Moreover, there are variations depending on the pollutant considered. In general, one can distinguish between four methods:

## E NERGY

1.78 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Method A Hot emissions are calculated based on: - the total annual kilometres driven per vehicle; - the share of kilometres driven under the driving modes “urban”, “rural” and “highway”; - the average speed of the vehicles under the driving modes “urban”, “rural” and “highway”; - speed-dependent hot emission factors.
Cold start emissions are calculated based on: - the average trip length per vehicle trip; - the average monthly temperature; - temperature and trip length dependent cold start correction factor. Evaporative emissions are calculated based on: - the fuel volatility (RVP); - the average monthly temperature and the average monthly temperature variation; - fuel volatility and temperature dependent emission factors.

Method B The total annual emissions per vehicle are calculated based on: - the total annual kilometres driven per vehicle; - the share of kilometres driven under the driving modes “urban”, “rural” and “highway”; - the average speed of the vehicles under the driving modes “urban”, “rural” and “highway”; - speed-dependent emission factors.
Note: for diesel passenger cars, cold start extra emissions for CO, NO x and NMVOC, as well as extra fuel consumption, are added using the method described under A. For LPG passenger cars a simplified method is used.

Method C The total annual emissions per vehicle are calculated based on: - the total annual kilometres driven per vehicle; - the share of kilometres driven under the driving modes “urban”, “rural” and “highway”; - driving mode dependent emissions factors. Note: for gasoline and diesel light-duty vehicle, cold start extra emissions for CO, NO X and NMVOC, as well as fuel consumption, are added using the method described under A. For gasoline light-duty vehicles, NMVOC evaporative emissions are added using the method described under A.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.79 Method D The total annual emissions per vehicle category are calculated based on: - the total annual fuel consumption of the vehicle category and/or the total annual kilometres driven by the vehicle category; - fuel consumption and/or kilometre related emission factors. Note: For two wheelers NMVOC evaporative emissions are added using the method described under A.

T ABLE 1-34
S UMMARY OF P RECISION I NDICATORS OF THE E MISSION E STIMATES AND OF C ALCULATION M ETHODS A PPLIED FOR THE D IFFERENT V EHICLE C ATEGORIES AND P OLLUTANTS (A, B, C, D: Method Indicators - 1, 2, 3, 4: Precision Indicators) Vehicle Category NO x CO NMVOC CH 4 N 2 O CO 2 Fuel Passenger Cars Gasoline A/1 A/1 A/1 C/1 C/3 D/1 A/1 Diesel B/1 B/1 B/1 C/2 C/3 D/1 B/1 LPG B/1 B/1 B/1 - - D/1 B/1 Two stroke C/2 C/2 C/2 C/4 C/4 D/2 C/2 Light-Duty Vehicles C/1 C/1 C/1 C/3 C/4 D/1 C/1 Heavy-Duty Vehicles C/2 C/2 C/2 C/4 D/4 D/2 C/2 Two Wheelers D/2 D/2 D/2 D/4 - D/2 D/2 Evaporation Passenger Cars - - A/3 (a)

---- Light-Duty Vehicles - - C/4 (a)

---- Two Wheelers - - D/4 - - - -
Cold Start Passenger Cars Conventional Gas. A/2 A/2 A/2 - - A/2 A/2 Catalyst Gasoline A/3 A/3 A/3 - - A/2 A/3 Diesel A/3 A/3 A/3 - - A/3 A/3 LPG B/3 B/3 B/3 - - B/3 B/3 Light Duty Vehicles C/4 C/4 C/4 - - C/4 C/4 1: Statistically significant emission factors based on a sufficiently large set of measured and reevaluated data. 2: Emission factors non-statistically significant based on a small set of measured and re-evaluated data. 3: Emission factors estimated on the basis of available literature. 4: Emission factors estimated applying similarity considerations and/or extrapolation. (a) Only for gasoline engine vehicles.

For the IPCC Guidelines , the emission factors from the COPERT model are presented using the American vehicle and control type categories, for ease of comparison. The emission factors have been calculated using data from 15 western and eastern European countries. Therefore the vehicle usage pattern, such as average speed and frequency of cold starts, climatic conditions like the monthly average temperature, and the fuel

## E NERGY

1.80 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual characteristics of these countries are incorporated in the figures. The emission factors provided are therefore valid for an average European situation. In developing the following tables, a net calorific value of 43.5 TJ/kt was assumed for gasoline, 42.4 TJ/kt for diesel and 46.1 TJ/kt for LPG.

T ABLE 1-35 E UROPEAN E MISSION C ONTROL T ECHNOLOGY T YPES AND C ORRESPONDING EU L EGISLATION AND M ODEL Y EARS

T ECHNOLOGY L EGISLATION (M ODEL Y EAR ) Uncontrolled Pre ECE (up to 1970) Early non-catalyst controls ECE 15 00 to 02 (1971-1979) Non-catalyst controls ECE 15 03 to 04 (1980-early 1990s) Oxidation catalyst 88/76/EEC (1988-1991) Three-way catalyst 91/441/EEC (1989-1995)

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.81 T ABLE 1-36 E STIMATED E MISSION F ACTORS FOR E UROPEAN G ASOLINE P ASSENGER C ARS
E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Uncontrolled: Assumed Fuel Economy 8.9 km/l (11.2 l/100 km) Total g/km 2.2 0.07 5.3 46 0.005 270 Exhaust 2.2 0.07 3.9 46 0.005 270 Evaporative (a) 1.4 g/kg fuel 27 0.8 63 550 0.06 3180 g/MJ 0.6 0.02 1.5 13 0.001 73 Early non-catalyst controls: Assumed Fuel Economy 10.6 km/l (9.4 l/100 km) Total g/km 2.0 0.08 5.2 29 0.005 225 Exhaust 2.0 0.08 3.8 29 0.005 225 Evaporative (a) 1.4 g/kg fuel 29 1.1 74 405 0.07 3180 g/MJ 0.7 0.03 1.7 9.3 0.002 73 Non-catalyst controls: Assumed Fuel Economy 12.0 km/l (8.3 l/100 km) Total g/km 2.3 0.07 4.5 19 0.005 200 Exhaust 2.3 0.07 3.2 19 0.005 200 Evaporative (a) 1.3 g/kg fuel 37 1.1 72 300 0.08 3180 g/MJ 0.8 0.03 1.7 6.9 0.002 73 Oxidation catalyst: Assumed Fuel Economy 12.3 km/l (8.1 l/100 km) Total g/km 1.4 0.07 1.4 7.5 0.005 190 Exhaust 1.4 0.07 1.0 7.5 0.005 190 Evaporative (a) 0.4 g/kg fuel 22 1.2 24 125 0.08 3180 g/MJ 0.5 0.03 0.6 2.9 0.002 73 Three-way catalyst: Assumed Fuel Economy 11.8 km/l (8.5 l/100 km) Total g/km 0.5 0.02 0.5 2.9 0.05 205 Exhaust 0.5 0.02 0.4 2.9 0.05 205 Evaporative (a) 0.06 g/kg fuel 8.2 0.3 7.1 45.9 0.8 3180 g/MJ 0.12 0.007 0.2 1 0.02 73 2-stroke: Assumed Fuel Economy 9.2 km/l (10.9 l/100 km) Total g/km 0.8 0.08 12 12 0.005 260 Exhaust 0.8 0.08 10.7 12 0.005 260 Evaporative (a) 1.5 g/kg fuel 9.3 1.0 164 150 0.06 3180 g/MJ 0.2 0.02 3.8 3.4 0.001 73 (a) Including diurnal, soak and running losses

## E NERGY

1.82 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-37 E STIMATED E MISSION F ACTORS FOR E UROPEAN D IESEL P ASSENGER C ARS E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Moderate control: Assumed Fuel Economy 13.7 km/l (7.3 l/100 km)
Total g/km 0.7 0.005 0.2 0.7 0.01 190 g/kg fuel 11 0.08 3.0 12 0.2 3140 g/MJ 0.3 0.002 0.07 0.3 0.004 74

T ABLE 1-38 E STIMATED E MISSION F ACTORS FOR E UROPEAN D IESEL L IGHT -D UTY V EHICLES E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Moderate control: Assumed Fuel Economy 9.2 km/l (10.9 l/100 km)
Total g/km 1.4 0.005 0.4 1.6 0.02 280 g/kg fuel 16 0.06 4.6 18 0.2 3140 g/MJ 0.4 0.001 0.1 0.4 0.004 74

T ABLE 1-39 E STIMATED E MISSION F ACTORS FOR E UROPEAN D IESEL H EAVY -D UTY V EHICLES E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Moderate control: Assumed Fuel Economy 3.3 km/l (29.9 l/100 km)
Total g/km 10 0.06 1.9 9.0 0.03 770 g/kg fuel 42 0.2 8.0 36 0.1 3140 g/MJ 1.0 0.006 0.2 0.9 0.003 74

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.83 T ABLE 1-40 E STIMATED E MISSION F ACTORS FOR E UROPEAN G ASOLINE L IGHT -D UTY V EHICLES E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Moderate control: Assumed Fuel Economy 7.4 km/l (13.6 l/100 km) Total g/km 2.9 0.08 6.1 37 0.006 325 Exhaust 2.9 0.08 4.8 37 0.006 325 Evaporative (a) 1.3 g/kg fuel 29 0.8 59 360 0.06 3180 g/MJ 0.7 0.02 1.4 8.3 0.001 73

T ABLE 1-41 E STIMATED E MISSION F ACTORS FOR E UROPEAN G ASOLINE H EAVY -D UTY V EHICLES E MISSIONS NO x CH 4 VOC CO N 2 O CO 2 Uncontrolled: Assumed Fuel Economy 4.4 km/l (22.5 l/100 km) Total g/km 6.9 0.1 5.4 58 0.006 535 Exhaust 6.9 0.1 5.4 58 0.006 535 Evaporative (a) g/kg fuel 40 0.7 32 346 0.04 3180 g/MJ 0.9 0.02 0.8 7.9 0.001 73

T ABLE 1-42 E STIMATED E MISSION F ACTORS FOR E UROPEAN M OTORCYCLES E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 M OTORCYCLES < 50 CC Uncontrolled: Assumed Fuel Economy 41.7 km/l (2.4 l/100 km) Total g/km 0.05 0.1 6.5 10 0.001 57 Exhaust 0.05 0.1 6.2 10 0.001 57 Evaporative (a) 0.3 g/kg fuel 2.8 5.6 359 550 0.06 3180 g/MJ 0.06 0.1 8.3 13 0.001 73 M OTORCYCLES > 50 CC 2 STROKE Uncontrolled: Assumed Fuel Economy 25.0 km/l (4.0 l/100 km) Total g/km 0.08 0.15 16 22 0.002 95 Exhaust 0.08 0.15 15 22 0.002 95 Evaporative (a) 1.0 g/kg fuel 2.7 5.0 530 730 0.07 3180 g/MJ 0.06 0.1 12 17 0.002 73 M OTORCYCLES > 50 CC 4 STROKE Uncontrolled: Assumed Fuel Economy 19.6 km/l (5.1 l/100 km) Total g/km 0.30 0.20 3.9 20 0.002 120 Exhaust 0.30 0.20 3.4 20 0.002 120 Evaporative (a) 0.5 g/kg fuel 7.9 5 105 530 0.05 3180 g/MJ 0.2 0.1 2.4 12 0.001 73 (a) Including diurnal, soak and running losses

## E NERGY

1.84 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Road Vehicles - Alternative Fuels Alternative motor vehicle fuels such as natural gas, liquefied petroleum gas (LPG), methanol and ethanol are presently being used in a limited way, and are the subjects of a great deal of research and development effort aimed at increasing their usage in the future. This section presents some preliminary estimates of the emissions to be expected from vehicles using these fuels, based on fuel properties and the limited emissions data available. 20
Natural gas Because natural gas is mostly methane, natural gas vehicles (NGVs) have lower exhaust NMVOC emissions than gasoline vehicles, but higher emissions of methane

. There are no evaporative or running-loss emissions, while refuelling emissions and cold-start emissions are lower

. These conditions reduce both NMVOC and CO emissions relative to gasoline vehicles

. CO 2 emissions from NGVs will be lower than for gasoline vehicles, since natural gas has a lower carbon content per unit of energy

. It is possible to attain increased efficiency by increasing the compression ratio

. Optimised heavy-duty NGV engines can approach diesel efficiency levels

. NO x emissions from uncontrolled NGVs may be higher or lower than comparable gasoline vehicles, depending on the engine technology

. NO x emissions from NGVs are more difficult to control using three-way catalysts. N 2 O emissions from NGVs were not included. Table 1-43 shows three types of NGVs: passenger cars, gasoline-type heavy-duty vehicles, and diesel-type heavy-duty vehicles. 21 Two sets of emission factors are shown for each: uncontrolled (typical of a simple natural gas conversion, without catalytic converter or optimisation for emissions) and advanced control (reflecting an engine and catalytic converter factory-produced and optimised for natural gas). The estimates for the passenger car and gasoline-type heavy-duty vehicle are based on a gasoline-type engine, converted to use natural gas. For the uncontrolled vehicles, no changes in the engine are assumed beyond the fitting of a natural gas mixer and modified spark timing such that the efficiency would be the same. For the vehicles with advanced control, a higher compression ratio is assumed to give 15 per cent better fuel efficiency. For the diesel-type heavy-duty vehicles, the engine assumed is a diesel-type engine, converted to lean, Otto-cycle operation using natural gas. The uncontrolled case reflects no further optimisation beyond the conversion, while the controlled case includes extensive combustion optimisation for NO x control and an oxidation catalytic converter. Liquefied petroleum gas LPG is primarily propane (or a propane/butane mixture) rather than methane which affects the composition of exhaust VOC emissions, but otherwise is similar to natural gas. Evaporative and refuelling emissions are virtually zero, and CO and exhaust NMVOC emissions are usually lower than gasoline vehicles. The CO 2 emissions should be somewhat lower than gasoline, due to the lower carbon-energy ratio, and the higher

20 Actual emission levels from these vehicles may be very different, and further testing is needed to confirm these estimates.

21 The emissions considered are only those of the vehicle itself – additional emissions due to, e.g., compression or liquefaction of gas for storage on the vehicle, leakage from pipelines, etc. are not included, nor are the potential emissions credits due to, e.g., production of methane from biomass. This is consistent with the treatment of emissions from vehicles using oil-based fuels.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.85 octane level allows some increase in efficiency, although less than for natural gas. NO x emissions from LPG vehicles tend to be higher than for gasoline, but can also be controlled using three-way catalysts. N 2 O emissions were not included. Table 1-44 shows two types of LPG vehicles. The engines and technologies considered are the same as those for natural gas, except that the lean, diesel-derived natural gas engine with propane is not considered.
Methanol and Ethanol The two alcohols have similar properties, and are discussed together. Development efforts have focused primarily on mixtures of alcohols with gasoline, in flexible fuel vehicles, capable of running on any combination of gasoline and up to 85 per cent methanol or ethanol. Engines and emission control systems are similar to those for advanced-technology gasoline vehicles, and the overall energy efficiency and emissions properties are similar. Table 1-46 shows estimated emissions for a vehicle of this type using M85 (85% methanol / 15% gasoline) fuel. Also shown are some rough em issions estimates for heavy-duty vehicles equipped with methanol or ethanol engines.

## E NERGY

1.86 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-43 E STIMATED E MISSION F ACTORS F OR US L IGHT - A ND H EAVY -D UTY N ATURAL G AS V EHICLES
NO x CH 4 NMVOC CO N 2 O CO 2 Passenger Cars Advanced Control; Assumed Fuel Economy: 14.9 km/m 3
g/km 0.5 0.7 0.05 0.3 NAV 133 g/kg fuel 10.3 14.5 1.0 6.2 NAV 2750 g/MJ 0.21 0.29 0.02 0.12 NAV 56.1 Uncontrolled; Assumed Fuel Economy: 6.5 km/m 3
g/km 2.1 3.5 0.5 4.0 NAV 305 g/kg fuel 19.0 31.6 4.5 36.1 NAV 2750 g/MJ 0.38 0.63 0.09 0.72 NAV 56.1 Heavy-Duty Vehicles: Stoichiometric Engine (compare with gasoline) Advanced Control; Assumed Fuel Economy: 3.6 km/m 3
g/km 2.6 3.0 0.20 1.0 NAV 550 g/kg fuel 13.0 15.0 1.0 5.0 NAV 2750 g/MJ 0.26 0.30 0.02 0.10 NAV 56.1 Uncontrolled; Assumed Fuel Economy: 2.2 km/m 3 g/km 5.7 10.0 1.4 12.0 NAV 900 g/kg fuel 17.4 30.6 4.3 36.7 NAV 2750 g/MJ 0.35 0.61 0.09 0.73 NAV 56.1 Heavy-Duty Vehicles: Lean Burn Engine (compare with diesel) Advanced Control; Assumed Fuel Economy: 2.4 km/m 3 g/km 4.0 4.0 0.40 1.5 NAV 825 g/kg fuel 13.3 13.3 1.3 5.0 NAV 2750 g/MJ 0.27 0.27 0.03 0.10 NAV 56.1 Uncontrolled; Assumed Fuel Economy: 2.0 km/m 3 g/km 23.0 10.0 2.0 8.0 NAV 990 g/kg fuel 63.9 27.8 5.6 22.2 NAV 2750 g/MJ 1.28 0.56 0.11 0.44 NAV 56.1

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.87 T ABLE 1-44 E STIMATED E MISSION F ACTORS F OR US L IGHT - A ND H EAVY -D UTY LPG V EHICLES

. NO x CH 4 NMVOC CO N 2 O CO 2 Passenger Cars
Advanced Control g/km 0.5 0.03 0.25 0.3 NAV 170 g/kg fuel 8.8 0.6 4.4 5.3 NAV 3000 g/MJ (a) 0.19 0.01 0.10 0.11 NAV 63.1
Uncontrolled g/km 2.1 0.18 3.5 8.0 NAV 356 g/kg fuel 17.7 1.5 29.5 67.5 NAV 3000 g/MJ 0.38 0.03 0.64 1.45 NAV 63.1 Heavy-Duty Vehicles: Stoichiometric Engine (compare with gasoline)
Advanced Control g/km 2.6 0.15 0.70 1.0 NAV 695 g/kg fuel 11.2 0.6 3.0 4.3 NAV 3000 g/MJ 0.24 0.01 0.07 0.09 NAV 63.1
Uncontrolled g/km 5.7 0.4 8.0 24.0 NAV 1020 g/kg fuel 16.8 1.2 23.5 70.6 NAV 3000 g/MJ 0.36 0.03 0.51 1.52 NAV 63.1 (a) Berdowski, et al. (1993a) suggest a CH 4 emission factor of 0.013 g/MJ for this vehicle/technology class.

T ABLE 1-45 E STIMATED E MISSION F ACTORS FOR E UROPEAN LPG P ASSENGER C ARS E MISSIONS NO x CH 4 NMVOC CO N 2 O CO 2 Moderate control: Assumed Fuel Economy 8.9 km/l (a) (11.2 l/100 km)
Total g/km 2.2 0.06 1.5 7.1 - 180 g/kg fuel 37 1.0 25 120 - 3030 g/MJ 0.9 0.02 0.6 2.6 - 65 (a) Under 5 bar pressure

## E NERGY

1.88 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-46 E STIMATED E MISSION F ACTORS FOR US L IGHT - AND H EAVY - DUTY M ETHANOL V EHICLES E MISSIONS
NO x CH 4 NMVOC CO N 2 O CO 2 Passenger Cars (M85 Fuel)
Advanced Control g/km 0.5 0.02 0.66 3.14 NAV 183 g/kg fuel 4.5 0.2 5.9 28.0 NAV 1632 g/MJ 0.19 0.01 0.25 1.19 NAV 69.7 Heavy-Duty Vehicles - Methanol-Diesel Engine - M100 Fuel
Advanced Control g/km 4.0 0.1 1.50 4.0 NAV 908 g/kg fuel 6.1 0.2 2.3 6.1 NAV 1375 g/MJ 0.30 0.01 0.11 0.30 NAV 68.8



### 1.5.3.4 S URFACE 

### N O N 

### - R OAD 

### S OURCES Emission factors are provided for major non-road vehicle source categories including farm and construction equipment, railway locomotives, boats, and ships (all primarily equipped with diesel engines), jet aircraft, and gasoline-fuelled piston aircraft. Table 1-47 presents emission factors specific to the United States, but may be applicable to other regions as well. The emission factors for diesel engines used in railway locomotives, farm equipment such as tractors and harvesters, construction equipment such as bulldozers and cranes, and diesel boats, are from Weaver (1988). N 2 O emission factors for off-road diesels are assumed to be the same as those for heavy-duty onhighway diesel engines.Large ocean-going cargo ships are driven primarily by large, slow-speed and mediumspeed diesel engines, and occasionally by steam turbines and gas turbines (the latter in high power-weight ratio vessels such as fast ferries and warships). The number of vessels equipped with steam or gas-turbine propulsion is small, however, since these vessels are unable to compete with the more efficient diesels in most applications. The results shown for NO x and CO are from Hadler (1990) 22 . N 2 O emissions for these engines were assumed to be the same, on a fuel-specific basis, as those for other heavy-duty diesels, and VOC emissions from these large diesels are probably negligible.

22 Other sources consulted for comparison are Melhus (1990), Bremnes (1990), Alexandersson (1990).

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.89 T ABLE 1-47 E STIMATED E MISSION F ACTORS F OR US N ON -R OAD M OBILE S OURCES

UNCONTROLLED EMISSIONS

NO x CH 4 NMVOC CO N 2 O CO 2 Ocean-Going Ships g/kg fuel 87 NAV NAV 1.9 0.08 3212 g/MJ 2.1 NAV NAV 0.046 0.002 77.6

Boats g/kg fuel 67.5 0.23 4.9 21.3 0.08 3188 g/MJ 1.6 0.005 0.11 0.50 0.002 75.0
Locomotives g/kg fuel 74.3 0.25 5.5 26.1 0.08 3188 g/MJ 1.8 0.006 0.13 0.61 0.002 75.0 Farm Equipment g/kg fuel 63.5 0.45 9.6 25.4 0.08 3188 g/MJ 1.5 0.011 0.23 0.60 0.002 75.0 Construction and Industrial Equipment g/kg fuel 50.2 0.18 3.9 16.3 0.08 3188 g/MJ 1.2 0.004 0.09 0.38 0.002 75.0 Jet and Turboprop Aircraft g/kg fuel 12.5 0.087 0.78 5.2 NAV 3149 g/MJ 0.29 0.002 0.018 0.12 NAV 72.8 Gasoline (Piston) Aircraft g/kg fuel 3.52 2.64 24 1034 0.04 3172 g/MJ 0.08 0.06 0.54 24 0.0009 72.1

A detailed experimental assessment of exhaust emissions from a broad cross section of ship categories including bulk carriers, container ships, dredgers, ferries, tankers and tugs has recently been completed by Lloyd’s Register (1995). The vessels evaluated by Lloyd’s Register were powered by in-service diesel engines of various vintages and sizes, and tested without modification. A total of sixty engines on fifty vessels were tested under steady-state conditions, and a further eight vessels were tested under transient engine loads by Lloyd’s Register (1995). Emission factors reported by Lloyd’s Register for medium and slow speed diesel engines are considered to be the best available to date and have been adopted in this study (see Table 1-48). In the absence of data on the relative time spent under steady state versus transient engine loads, steady state engine emission rates are adopted in this study for ocean-going ships. For detailed regional studies, it is recommended that surveys of engine type and mode of operation be undertaken to establish fleet emission rates for non-CO 2 gases.For slow to medium speed diesel engines, considered to be representative of large oceangoing cargo ships, Lloyd’s Register (1995) reported NO x emission rates of 57 and 87 kg/tonne of fuel, respectively. In the absence of data on the fleet composition of slow versus medium speed diesel engines for ocean going fleets, a NO x emission factor of 72

## E NERGY

1.90 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual kg/tonne of fuel is recommended. The corresponding emission rate documented by IPCC (1995) was 87 kg/tonne of fuel. Emission rates for CH 4 and NMVOC for ocean-going ships were not reported by IPCC (1995). In this study, CH 4 and NMVOC emission rates are estimated from hydrocarbon (HC) data reported by Lloyd’s Register according to CH 4 = 0.12 x HC and NMVOC = HC - CH 4 . Lloyd’s Register reported a CO emission rate of 7.4 kg/tonne of fuel for slow to medium speed diesel engines. In this study, the value of 7.4 kg CO/tonne of fuel is adopted for slow to medium speed diesel engines on ocean-going ships.
Emission factors for small engines mainly used in pleasure crafts and small fishing boats can be found in Table 1-49 under the heading “Inland waterways” for diesel engines as well as for 2-stroke and 4-stroke gasoline engines. The difference in emission rates noted above, illustrates the importance of characterising fleet engine types and fuel use for regional scale emissions from marine and other nonroad sources.

T ABLE 1-48 D EFAULT M ARINE E MISSION F ACTORS
CH 4 N 2 O NO x CO NMVOC Ocean-going Ships (diesel engines*) g/MJ 0.007 0.002 1.8 0.18 0.052 * Mostly using heavy fuel oil.

Table 1-49 presents emission factors for non-road vehicles in Europe. These estimates were produced for CORINAIR using national data and information compiled by Andrias et al., 1994.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.91 T ABLE 1-49 E STIMATED E MISSION F ACTORS FOR E UROPEAN N ON -R OAD M OBILE S OURCES AND M ACHINERY

P ART 1: D IESEL E NGINES
E MISSIONS NO x CH 4 (a) NMVOC (a) CO N 2 O CO 2 Diesel Engines g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ Agriculture 50 1.2 0.17 0.004 7.3 0.17 16 0.37 1.3 0.03 3140 73 Forestry 50 1.2 0.17 0.004 6.5 0.15 15 0.35 1.3 0.03 3140 73 Industry 49 1.1 0.17 0.004 7.1 0.16 16 0.37 1.3 0.03 3140 73 Household 48 1.1 0.17 0.004 10 0.23 23 0.53 1.2 0.03 3140 73 Railways 40 0.9 0.18 0.004 4.7 0.11 11 0.25 1.2 0.03 3140 73 Inland waterways 42 1.0 0.18 0.004 4.7 0.11 11 0.25 1.3 0.03 3140 73

P ART 2: G ASOLINE E NGINES E MISSIONS NO x CH 4 (a) NMVOC (a) CO N 2 O CO 2 Gasoline 4-stroke g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ Agriculture 7.6 0.17 3.7 0.08 74 1.7 1500 33 0.07 0.002 3200 71 Forestry

---- -- - - - - 3200 71 Industry 9.6 0.21 2.2 0.05 43 1.0 1200 27 0.08 0.002 3200 71 Household 8.0 0.18 5.5 0.12 110 2.5 2200 79 0.07 0.002 3200 71 Railways

---- -- - - - - - - Inland waterways 9.7 0.22 1.7 0.04 34 0.76 1000 22 0.08 0.002 3200 71 Gasoline 2-stroke g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ g/kg g/MJ Agriculture 1.7 0.04 6.2 0.14 620 14 1100 25 0.02 0.0004 3200 71 Forestry 1.6 0.04 7.7 0.17 760 17 1400 31 0.02 0.0004 3200 71 Industry 2.1 0.05 6.0 0.13 600 13 1100 31 0.02 0.0004 3200 71 Household 1.8 0.04 8.1 0.18 810 18 1600 36 0.02 0.0004 3200 71 Railways - - - - - - - - -

- - 71 Inland waterways 2.7 0.06 5.1 0.11 500 11 890 20 0.02 0.0004 3200 71 (a) Including diurnal, soak and running losses.



### 1.5.3.5 A IRCRAFT Background information While the emission factors for aircraft in the Tier 1 approach are fleet average factors for NO x , CO and NMVOC as derived from global inventories compiled by NASA, ECAC/ANCAT and others, this section presents a more refined Tier 2 method. The methodology includes four sub-activities:

## E NERGY

1.92 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual B OX 6
O VERVIEW OF THE A CTIVITIES I NCLUDED CORINAIR94
IN THE P RESENT M ETHODOLOGY CLASSIFICATION ( A ) Domestic airport traffic (LTO (b) -cycles < 914m (3000 ft) altitude) SNAP (c) code 080501 International airport traffic (LTO-cycles < 914m (3000 ft) altitude) SNAP code 080502
Domestic cruise traffic ( > 914m (3000 ft) altitude (d) ) SNAP code 080503
International cruise traffic ( > 914m (3000 ft) altitude (d) ) SNAP code 080504

(a) CORINAIR uses a round figure of 1000 metres (for 3000 feet) as the cut-off. (b) LTO is short for the Landing and Take-Off cycle. (c) SNAP codes refer to the joint EMEP/CORINAIR Methodology, used in Europe. (d) Including further climbout from and descent to 914 metres (3000 feet) altitude.

Activities include all civil commercial use of airplanes consisting of scheduled and charter traffic of passengers and freight. This also includes taxiing. Military and private aviation activities are not included because respectively, it is unlikely that detailed information is available and fuel usage is proportionately very small. However, theoretically this method could also be used for the estimation of the emissions of military aircraft. In that case, these emissions should be reported under 1A5 “Other” and not with domestic or international aviation. Operations of aircraft are divided into two parts:

• The Landing/Take-Off (LTO) cycle 23 which includes all activities near the airport that take place under the altitude of 914 metres (3000 feet). This includes engines running idle, taxi-in and out, and climbing and descending under this altitude. In aircraft industry-related literature (e.g., the ICAO), the cut-off altitude is often 3000 feet which corresponds to 914 metres.

• Cruise is defined as all activities that take place at altitudes above 914 metres (3000 feet). No upper limit is given. This also includes further climb-out from and descent to an altitude of 914 metres.

Activities For the purposes of the emissions inventory a distinction is made between domestic and international flights 24

.

23 Some statistics count either a landing or a take-off as one operation. However it is **both** one take-off and one landing, that together define one LTO-operation.

24 If an aircraft goes from one airport in one country to another in the same country and then leaves to a third airport in another country, the first flight stage is considered a domestic trip while the second is considered an international trip. It is not important whether the airport is a domestic or an international airport. In addition, the type of

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.93 • Domestic aviation (1 A 3 a ii) includes all civil domestic passenger and freight traffic inside a country. All flight stages between two airports in one country are considered domestic no matter the nationality of the carrier or the subsequent destination of the aircraft.

• International aviation (1 A 3 a i) includes all civil air traffic coming to or leaving acountry. It is assumed that the number of out-bound flights equals the number of inbound flights.

• LTOs take the classification (domestic or international) of the flight stage to which they belong. As most flights are regarded as return flights, fuel used during landing and take-off will be regarded as equal to a take-off and landing.
Techniques In general, there exist two types of engines (Olivier, 1991):

• reciprocating piston engines , where energy is extracted from a combustion chamber by means of a piston and crank mechanism which drives the propellers to give the aircraft momentum; and

• gas turbines , where compressed air is heated by combustion in a combustion chamber and the major part of the released energy is used for propulsion of the aircraft. Part of the energy contained in the hot air flow is used to drive the turbine which in turn drives the compressor. Turbojet engines use energy only from the expanding exhaust stream for propulsion, whereas turbofan and turboprop engines use energy to drive an extra turbine which drives a fan or propeller respectively, for propulsion.

Emissions Air traffic as a source of combustion emissions varies with respect to the type of fuel which is being used, the location (altitude) of the exhaust gases, the types and the efficiency of the engines, and the length of the flight. Emissions come from jet kerosene and aviation gasoline which are used as fuel on the aircraft. This Tier 2 methodology is only applicable for jet fuel used in jet engines. Aviation gasoline is only used in small aircraft (often referred to as “general aviation”) and generally represents less than 1 per cent of fuel consumption for aviation. As a result, no attempt has been made to estimate emission factors for private aviation as this represents such a small proportion of global consumption. Use of energy, and therefore emissions, is dependent on the aircraft operations and the time spent at each stage 25 . A substantial part of the fuel consumption takes place outside

activity (LTO, cruise, domestic, international) is independent of the nationality of the carrier. This treatment of domestic and international differs from that recommended to states by the International Civil Aviation Organization (ICAO,1994). ICAO defines as domestic all flight stages flown between domestic points by an airline registered in that state and therefore excludes flights between domestic points by foreign airlines.

25 Note: The reference LTO cycle that was used to estimate the emission factors has a cycle time of 32.9 minutes made up of the four individual Times in Mode (TIM) according to ICAO recommendations. Depending on whether there is more or less congestion at the airport this time may be shorter or longer. In particular, taxi times may differ substantially between large metropolitan airports and small airports. This can be

## E NERGY

1.94 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual the LTO-cycle. Studies indicate that in national airspace 60-80 per cent of NO x and 80-90 per cent of SO 2 and CO 2 is emitted at altitudes above 914 metres (3000 feet). For CO it is about 50 per cent and for VOC it is about 20-40 per cent (Olivier, 1991). Globally, however, 80 to 90 per cent of these emissions are emitted above an altitude of 914 metres (3000 feet) (Olivier, 1995). Besides the combustion of fuel in the LTO and cruise activities, fuelling and fuel handling in general, maintenance of aircraft engines and fuel jettisoning to avoid accidents are emission sources. In the wintertime, anti-ice and de-ice treatment of wings and aircraft is a source of emissions at airport complexes. Many of the substances used flow off the wings when planes are idling, taxiing, and taking off, and then evaporate. These emissions are, however, not included in the methodology.

Emission factors
For LTO cycles, Table 1-50 gives relevant examples from the ICAO Engine Exhaust Emissions Databank (ICAO, 1995). This provides emission factors for LTO cycles for a large number of engines treated under standard conditions. Another useful source of aircraft emission factors is the FAA Aircraft Emission database, US Office of Environment and Energy (1991), derived from an early draft version of the ICAO database. For cruise activities, average NO x emission factors related to fuel consumption have been estimated and are displayed in Table 1-51. The cruise emission factors take into account the number of engines fitted to each specific aircraft. Where aircraft types used in a country are not displayed in Tables 1-50 or 1-51, data for the nearest equivalent type in either of those tables can be used or alternatively the average emission factors displayed in Table 1-52 can be used. Please note that when using the emission factors, the assumptions on sulphur content in the fuel should be taken into account. The factors have been calculated assuming a weight percentage of 0.05 per cent 26 . Actual values of sulphur content in jet kerosene vary between 0.0001 and 0.3 per cent.

calculated for individual airports and individual aircraft as a Tier 3 methodology (see last paragraph of Section 1.3).

26 For example, if the sulphur content of fuel used is 0.01 per cent, the emission factor for SO 2 should be divided by 5 to show the corresponding factor.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.95 Recommended Methodology The fundamental basis of the recommended Tier 2 methodology is presented schematically in Figure 1.

x EF x EF

x EF x EF

Emissions for Domestic

LTO Emissions for International LTO Domestic Cruise Fuel Use

Emissions for

Domestic

Cruise Emissions for International

Cruise International Cruise Fuel Use Fuel Sold for International Use Fuel Sold for Domestic

Use Number of LTO’s for Domestic

Flights

Domestic LTO Fuel Use International LTO Fuel Use Fuel Consumption per Domestic LTO Fuel Consumption per International LTO Number of LTO’s for International Flights Total National Number of LTO’s Total National Fuel Sold for Aircraft

Figure 1: Estimation of Aircraft Emissions with the Tier 2 Method

To use the Tier 2 method, the aircraft types used for both domestic and international aviation, as well as the number of LTO’s carried out with the various aircraft types, must be known. If such information is available, it is recommended that the emission factors in Table 1-52 be used. If information on LTO’s is not available, it is recommended that the Tier 1 method be used.

## E NERGY

1.96 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The emissions calculated using Tier 2 should be reported following the IPCC Reporting Instructions :

• I A 3 a i International aviation (international bunkers) - note: as far as possible, these emissions are to be excluded from national totals and reported separately.

• I A 3 a ii Domestic aviation

T ABLE 1-50 E XAMPLES O F A IRCRAFT T YPES A ND E MISSION F ACTORS F OR LTO C YCLES A S W ELL A S F UEL C ONSUMPTION P ER A IRCRAFT T YPE
Emission factors (kg/LTO) Fuel consumption ( kg/LTO) Aircraft type (a) CO 2 CH 4 (b) N 2 O (c) NO X CO NMVOC (b) SO 2 (d)
A300 5470 1.0 0.2 27.21 34.4 9.3 1.7 1730 A310 4900 0.4 0.2 22.7 19.6 3.4 1.5 1550 A320 2560 0.04 0.1 11.0 5.3 0.4 0.8 810 BAC1-11 2150 6.8 0.1 4.9 67.8 61.6 0.7 680 BAe 146 1800 0.16 0.1 4.2 11.2 1.2 0.6 570 B707 * 5880 9.8 0.2 10.8 92.4 87.8 1.9 1860 B727 4455 0.3 0.1 12.6 9.1 3.0 1.4 1410 B727 * 3980 0.7 0.1 9.2 24.5 6.3 1.3 1260 B737-200 2905 0.2 0.1 8.0 6.2 2.0 0.9 920 B737 * 2750 0.5 0.1 6.7 16.0 4.0 0.9 870 B737-400 2625 0.08 0.1 8.2 12.2 0.6 0.8 830 B747-200 10680 3.6 0.3 53.2 91.0 32.0 3.4 3380 B747 * 10145 4.8 0.3 49.2 115 43.6 3.2 3210 B747-400 10710 1.2 0.3 56.5 45.0 10.8 3.4 3390 B757 4110 0.1 0.1 21.6 10.6 0.8 1.3 1300 B767 5405 0.4 0.2 26.7 20.3 3.2 1.7 1710 Caravelle * 2655 0.5 0.1 3.2 16.3 4.1 0.8 840 DC8 5890 5.8 0.2 14.8 65.2 52.2 1.9 1860 DC9 2780 0.8 0.1 7.2 7.3 7.4 0.9 880 DC10 7460 2.1 0.2 41.0 59.3 19.2 2.4 2360 F28 2115 5.5 0.1 5.3 54.8 49.3 0.7 670 F100 2340 0.2 0.1 5.7 13.0 1.2 0.7 740 L1011* 8025 7.3 0.3 29.7 112 65.4 2.5 2540 SAAB 340 945 1.4(E) 0.03(E) 0.3(E) 22.1(E) 12.7(E) 0.3(E) 300(E) Tupolev 154 6920 8.3 0.2 14.0 116.81 75.9 2.2 2190 Concorde 20290 10.7 0.6 35.2 385 96 6.4 6420 GAjet 2150 0.1 0.1 5.6 8.5 1.2 0.7 680 Source: ICAO (1995). (a) Except where indicated, values are for world fleet weighted LTO fuel and emissions performance. The average age of aircraft in service is 10-20 years old. Values for aircraft types marked with a * are specific to older types with poorer emissions performance. Aircraft can be equipped with different engines. (b) Assuming 10% of total VOC emissions in LTO cycles are methane emission (Olivier, 1991). (c) Estimates based on Tier 1 default values. (d) The sulphur content of the fuel is assumed to be 0.05%. (E) indicates that the figure is based on estimations.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.97 T ABLE 1-51 E MISSION F ACTORS OF NO x FOR V ARIOUS A IRCRAFT AT C RUISE L EVELS
Aircraft Emission Factor for NO x (g/kg) ANCAT NASA Average
A300 NAV 14.4 NAV
A310 11.5 13.6 12.5
A320 11.7 12.1 11.9
BAC 1-11 7.1 9.3 8.2
BAe 146 6.7 7.7 7.2
B727 8.0 8.7 8.4
B737-200 6.8 7.7 7.3
B737-400 8.3 9.6 9.0
B747-200 16.7 14.2 15.5
B747-400 15.8 13.9 14.9
B757 13.1 12.6 12.9
B767 10.0 12.2 11.1
DC8 12.4 5.6 9.0
DC9 7.6 8.1 7.9
DC10 17.5 13.2 15.4
F28 8.5 8.5 8.5
F100 8.4 6.4 7.4
MD80 8.3 10.6 9.5
TU154 NAV 8.7 NAV
Concorde 19.9 NAV NAV GAjet 6.7 NAV NAV Source: Gardner et al. (1997) and Baughcum et al. (1996).

## E NERGY

1.98 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-52 D EFAULT E MISSION F ACTORS AND F UEL C ONSUMPTION FOR A IRCRAFT

(LTO E MISSION F ACTORS ARE G IVEN ON A P ER A IRCRAFT B ASIS )

Domestic

Fuel Emission Factors Consumption CO 2 CH 4 (a) N 2 O (b) NO x CO NMVOC (a) SO 2 (c)

LTO average fleet (kg/LTO) 850 2680 0.3 0.1 10.2 8.1 2.6 0.8

LTO old fleet (kg/LTO) 1000 3150 0.4 0.1 9.0 17 3.7 1.0

Cruise (kg/t of fuel) 3150 0 0.1 11 7 0.7 1.0

International

Fuel Emission Factors Consumption CO 2 CH 4 (a) N 2 O (b) NO x CO NMVOC (a) SO 2 (c)

LTO average fleet (kg/LTO) 2500 7900 1.5 0.2 41 50 15 2.5

LTO old fleet (kg/LTO) 2400 7560 7 0.2 23.6 101 66 2.4

Cruise (kg/t of fuel) 3150 0 0.1 17 5 2.7 1.0
Note: The emission factors were calculated as weighted averages for a number of typical aircraft. For domestic traffic, the average fleet is represented by Airbus A320, Boeing 727, Boeing 737--400 and Mc Donald Douglas DC9 and MD80 aircraft. The old fleet is represented by Boeing B737 and McDonald Douglas DC9. For international traffic, the average fleet is represented by Airbus A300, Boeing B767, B747 and McDonald Douglas DC10, whilst the old fleet is represented by the Boeing B707, Boeing B747 and McDonald Douglas DC8. The data for LTO are shown in Table 1-50. Cruise data were taken from Wuebbles et al. (1993). The emission factors for cruise are considered as the best available default factors to date. (a) For CH 4 and NMVOC it is assumed that the emission factors for LTO cycles be 10% and 90% of total VOC, respectively (Olivier, 1991). Studies indicate that during cruise no methane is emitted (Wiesen et al., 1994). (b) Estimates based on Tier 1 default values. (c) Sulphur content of the fuel is assumed to be 0.05% for both LTO and cruise activities

.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.99 

## 1.6 Fugitive Emissions: Overview During all of the stages from the extraction of fossil fuels through to their final use the escape or release of gaseous fuels or volatile components or absorbed gases may occur. The methodologies for the estimation of these emissions (mostly methane) are presented in the sections which follow and are limited to activities conducted within the confines of the energy industries. Emissions from the use of road vehicle fuels are covered under fuel combustion. Emissions from solvents use are estimated within Chapter 3 but emissions arising from the manufacture of solvents within refineries are subsumed within the estimation of emissions from refineries in Section 1.8 Fugitive Emissions from Oil and Natural Gas Activities.



## 1.7 Fugitive Emissions from Coal Mining and Handling

1.7.1 Overview This section covers fugitive emissions of greenhouse gases (GHGs) from production, processing, handling and utilisation of coal. Intentional or unintentional releases of gases such as methane in mining are included here, as are emissions from inadvertent combustion of coal in coal mine fires

. By far the most important component of this subcategory is methane (CH 4 ) emissions from the mining and handling of coal

. The bulk of this section, therefore, deals with these emissions

. Two other fugitive emission sources are discussed briefly at the end of the section

. These are burning coal mines and waste piles, which emit CO 2 , and SO 2 scrubbing, which is also a source of CO 2 . There are very likely other fugitive emissions associated with the coal fuel cycle

. If important sources are identified, these will be considered for inclusion in future editions of the Guidelines

.



### 1.7.2 CH 4 

### from Coal Mining and Handling

1.7.2.1 G ENERAL 

### M ETHODOLOGY The process of coal formation, commonly called coalification, inherently generates methane and other by-products

. The formation of coal is a complex physio-chemical process occurring over millions of years

. The degree of coalification (defined by the rank of the coal) determines the quantity of methane generated and, once generated, the amount of methane stored in the coal is controlled by the pressure and temperature of the coal seam and by other, less well-defined characteristics of the coal

. The methane will remain stored in the coal until the pressure on the coal is reduced, which can occur through the erosion of overlying strata or the process of coal mining

. Once the methane has been released, it flows through the coal toward a region of lower pressure (such as a coal mine) and into the atmosphere (Boyer, 1990)

. Methane emissions from coal mining in 1990 contributed an estimated 23 to 39 Tg of global methane emissions (US EPA, 1993 a ; CIAB, 1992; Airuni and Zeidenvarg, 1992). The amount of CH 4 generated during coal mining is primarily a function of coal rank and depth, gas content, and mining methods, as well as other factors such as moisture. Coal

## E NERGY

1.100 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual rank represents the differences in the stages of coal formation and depends on the pressure and temperature history of the coal seam; high coal ranks, such as bituminous coal, contain more CH 4 than low coal ranks, such as lignite. Depth is important because it affects the pressure and temperature of the coal seam, which in turn determines how much CH 4 is generated during coal formation. If two coal seams have the same rank, the deeper seam will hold larger amounts of CH 4 because the pressure is greater at lower depths, all other things being equal. As a result, the methane emission factors for surface-mined coal are assumed to be lower than for underground mining. In most underground mines, methane is removed by ventilating large quantities of air through the mine and exhausting this air (typically containing a concentration of 1 per cent methane or less) into the atmosphere. In some mines, however, more advanced methane recovery systems may be used to supplement the ventilation systems and ensure mine safety. These recovery systems typically produce a higher concentration product, ranging from 35 to 95 per cent methane. In some countries, some of this recovered methane is used as an energy source, while other countries vent it to the atmosphere. Recent technological innovations are increasing the amount of medium- or high-quality methane that can be recovered during coal mining and the options available to use it. Thus, methane emissions could be reduced from this source in the future. In surface mines, exposed coal faces and surfaces, as well as areas of coal rubble created by blasting operations, are believed to be the major sources of methane. As in underground mines, however, emissions may come from the overburden (in limited cases where these strata contain gas), which is broken up during the mining process, and underlying strata, which may be fractured and destressed due to removal of the overburden. Because surface-mined coals are generally lower rank and less deeply buried, they do not tend to contain as much methane as underground-mined coals. Thus, emissions per tonne of coal mined are generally much lower for surface mines. Research is underway in the United States and elsewhere to increase the understanding of CH 4 emissions from surface mines (Kirchgessner et al., 1993; USGS, 1993). A portion of the CH 4 emitted from coal mining comes from post-mining activities such as coal processing, transportation, and use. Coal processing involves the breaking, crushing, and thermal drying of coal, making it acceptable for sale. Methane is released mainly because the increased surface area allows more CH 4 to desorb from the coal. Transportation of the coal contributes to CH 4 emissions, because CH 4 desorbs directly from the coal to the atmosphere while in transit (e.g., in railroad cars). Use of metallurgical coal also emits methane. For instance, in metallurgical coke production, coal is crushed to a particle size of less than 5 mm, vastly increasing the surface area of the coal and allowing more CH 4 to desorb. During the coking process, methane, carbon monoxide, and other volatile gases are released. In modern coke ovens, this gas is typically collected and used as a fuel source, but in older coke ovens, particularly those used in less developed regions, coke gas is vented to the atmosphere (Boyer et al., 1990; coke production is covered in Chapter 3). Some methane is also released from coal waste piles and abandoned mines. Coal waste piles are comprised of rock and small amounts of coal that are produced during mining along with marketable coal. There are currently no emission measurements for this source. Emissions are believed to be low, however, because much of the methane would likely be emitted in the mine and the waste rock would have a low gas content compared to the coal being mined. Emissions from abandoned mines may come from unsealed shafts and from vents installed to prevent the build-up of methane in mines. There is very little information on the number of abandoned mines, and no data are currently available on emissions from these mines. Most available evidence indicates that methane flow rates decay rapidly once deep mine coal production ceases (Williams and Mitchell, 1992;

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.101 Creedy, 1991). In some abandoned mines, however, methane can continue to be released from the surrounding strata for many years. In Belgium, France, and Germany, for example, several abandoned mines are currently being used as a source of methane which is being added to the gas system (Smith and Sloss, 1992; KfA, 1993). Due to the absence of measurement data for both coal waste piles and abandoned mines, no emissions estimates have been developed for these sources.

Review of Previous Methane Emission Estimation Studies Over the years, a variety of methane emissions estimates have been developed for coal mining, as shown in Table 1-53. As the table shows, the variation in estimates has been quite large, although more recent studies are showing more similar results. Many of the emission studies conducted to date have confronted difficulties in developing estimation methodologies and these have resulted in the widely varying estimates and large uncertainties. These difficulties include:

• Absence of data on which to base estimates: Many studies were developed without access to detailed data on methane emissions associated with various components of the coal cycle. For certain sources such as surface mines and postmining activities, moreover, reliable emissions measurements are still lacking.

• Use of national data to develop global estimates: Some studies have relied on data from a single country to estimate global methane emissions from coal mining. This approach can introduce large errors into the estimates, due to the difficulty of generalising from one country's coal characteristics and mining conditions to those of other countries. Mining experience has shown that there are frequently significant differences in methane emission factors within countries, coal basins, and even coal mines for a variety of geological and other reasons.

• Failure to include all possible emission sources: Some studies prepared to date have only estimated underground coal mining emissions from ventilation systems and have not included emissions from degasification systems, or post-mining emissions. In addition, many estimates have assumed emissions from surface mines to be negligible and have not included this source. At this point, moreover, there are still potential emission sources, such as abandoned mines, for which emissions cannot be estimated due to the absence of necessary data.

• Over-reliance on statistical estimation methodologies: Several studies have estimated global emission factors using statistical models that relate methane emissions to various coal properties. For the most part, these models have proven unreliable when estimates are compared to those developed using more detailed country-specific information. The principal problem with using statistical methodologies is the number of variables that can affect methane emissions. Mining experience has shown that a complete understanding of methane emissions requires detailed examination of coal and geological characteristics and that methane emissions can be highly variable within mines, basins and countries. Collecting comprehensive data and developing statistical models that can reliably predict emissions on a global basis is thus very difficult. In general, the results of the more recent country-specific and global methane emission studies are likely to be more reliable than previous efforts. For several of the major coal producing countries, for example, detailed data on methane emissions from underground mine ventilation and degasification systems are reported to central institutes and are publicly available. More recent studies have been able to use these data in preparing and validating their estimates of methane emissions from underground mines. Data are still

## E NERGY

1.102 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual lacking on emissions from surface mines and post-mining activities, thus even the emission estimates from more recent studies should be considered uncertain.
Suggested Emission Estimation Methods Methane emission estimates should be developed for the three principal sources of methane emissions: underground mines, surface mines, and post-mining activities. To assist in developing these estimates, the IPCC recommends use of a "tiered" approach for estimating emissions. For each source, two or more approaches (or "tiers") are presented for estimating emissions, with the first tier requiring basic and readily available data and higher tiers requiring additional data. Selection among the tiers will depend upon the quality of the data available in the country.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.103 T ABLE 1-53 S UMMARY OF E MISSIONS E STIMATES FROM S ELECTED S TUDIES Study Author Emissions Estimate

(Tg) Year of Estimate Methodological Issues

Koyama (1963) 20 1960 Hard coal only; no emissions estimates for surface mining or post-mining activities. 1960 coal production data.

Hitchcock & Wechsler (1972) 8 - 28 1967 Post-mining not included; source of emission factors, particularly low end, unspecified. 1967 coal production data.

Seiler (1984) 30 1975 Based on Koyama, with 1975 coal production data.

Crutzen (1987) 34 NA Source of emission factors unclear. Hard coal only; no emissions estimates for surface mining or post-mining activities.

Okken & Kram (1989) 15 - 45 NA Source of emission factors unclear. Hard coal only; no emissions estimates for surface mines or postmining activities.

Zimmermeyer (1989) 24 NA Only underground mining considered; no emissions estimates for surface mines or postmining activities.

Seltzer & Zittel (1990) 23 NA Adjusted Zimmermeyer by: (1) including surface mines; (2) assuming that 15 per cent of underground mining emissions (3.6 Tg) not emitted to the atmosphere due to methane utilisation.

Barns & Edmonds (1990) 25 1986 Assumed mathematical relationship between coal rank and depth and that in-situ methane content was equal to the mining emission factor.

Boyer et al. (1990) 33 - 64 1988 Statistical approach related methane emissions to in situ methane content. Correlation based on US data only. Large uncertainty in application of results for global estimates.

Hargraves (1990) 29 NA Method based on current methane production rates due to continued coalification. Airuni and Zeidenvarg (1992) 28 1990 Methodology unspecified.

CIAB (1992) 24 1990 Country specific data used where available for underground mines. Surface and post-mining emissions developed using low emission assumptions. No uncertainty analysis.

US EPA (1993c) 23 - 39 1990 Country specific data used where available for underground mines. Global average emission factors for rest of countries for underground mines and for all surface mining and post-mining emissions.

## E NERGY

1.104 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.7.2.2 U NDERGROUND 

### M INING Methane emissions from underground mines should include estimated emissions from ventilation systems and from degasification systems, if any of a country's mines use degasification systems to supplement ventilation. In the approaches outlined below, methods of estimating emissions from both of these sources are presented. Three possible approaches are suggested by the IPCC, with the choice among them depending upon the availability of data and the degree to which coal mining is considered a significant source of emissions by particular countries. Two of the methods, the “Global” and the “Country or Basin Average” methods are essentially identical in form; only the degree of detail and specificity in choice of emission factor(s) differs. The third, “Mine Specific” method relies on the assembly of methane emission measurements taken at coal mines. In the first two methods, Tiers 1 and 2, ranges of emission factors are given in terms of m 3 CH 4 /tonne of coal produced. The structure of the estimation is simply
Emissions (Gg CH 4 ) = Emission Factor (m 3 CH 4 / tonne) x tonnes of coal produced x Conversion Factor (Gg/10 6 m 3 )
A single value from the range of emission factors should be used to prepare the emissions estimate. The relevant coal production figure will be that for the country or the coal basin depending upon the method selected. Factors are given in the table below which permit the conversion of the volume emitted to mass. For those countries with comparatively large methane emissions from coal mining, the use of more detailed estimation methodologies may be warranted. In countries producing smaller quantities of coal, however, the most simple approach may provide a reasonably accurate first approximation of CH 4 emissions from underground mines.
Tier 1: Global Average Method The simplest method for estimating methane emissions is to multiply underground coal production by a factor drawn from a range of factors representing global average emissions from underground mining, including both ventilation and degasification system emissions. This method may be selected in cases where total coal production from underground mines is available but more detailed data are not. The Tier 1 Equation is shown below.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.105 E QUATION 1 T IER 1: G LOBAL A VERAGE M ETHOD – U NDERGROUND M INES CH 4 Emissions (Gg) = CH 4 Emission Factor (m 3 CH 4 /tonne of coal mined) x Underground Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 ) Where:

 the Emission Factor should be chosen from the following range Low CH 4 Emission Factor = 10 m 3 /tonne High CH 4 Emission Factor = 25 m 3 /tonne

 Conversion Factor converts the volume of CH 4 to a weight measure and

is the density of methane at 20°C and 1 atmosphere, namely: 0.67 Gg / 10 6 m 3
The IPCC recommends revised global average emission factors of 10 to 25 m 3 /tonne of coal mined (not including emissions from post-mining activities which should be calculated separately). This range reflects the findings of various country studies, as shown in Table 1-54. As more detailed emissions data are published by various countries, the factors can be further revised, if necessary.

T ABLE 1-54 E STIMATED U NDERGROUND E MISSION F ACTORS FOR S ELECTED C OUNTRIES Country Emission Factors (m 3 /tonne) Source

Former Soviet Union 17.8 - 22.2 US EPA, 1993c
United States 11.0 - 15.3 US EPA, 1993a Germany (East & West) 22.4 Zimmermeyer, 1989 United Kingdom 15.3 BCTSRE, 1992
Poland 6.8 - 12.0 Pilcher et al., 1991

Czechoslovakia 23.9 Bibler et al., 1992

Australia 15.6 Lama, 1992
Tier 2: Country or Basin Specific Method The suggested Tier 2 approach – called the "Country or Basin Specific Method" – can be used to refine the range of emission factors used for underground mining by incorporating some additional country or basin-specific information. Basically, this method enables a country with limited available data to determine a more appropriate and probably narrower range of emission factors for their underground mines. For many countries, it is expected that this range will fall within the global average emission factor range of 10 to 25 m 3 /tonne. The range of possible emission factors is not constrained under the Tier 2 approach, however, and some countries may find that their underground mining emission factors lie outside the global average emission factor range. The calculation procedure is identical to that described in Tier 1. To implement the Tier 2 approach, national experts must examine measurement data from at least a limited number of underground coal mines in their country or region. Using this data, either statistical analysis or expert judgement should be applied to

## E NERGY

1.106 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual develop a reasonable range of emission factors for the country or region. 27 Making this estimate will require judgement on the part of the estimator as to the adequacy of the available data and its uncertainty. If sufficient expertise is not available to make such judgements, it is recommended that the Tier 1 approach (the Global Average Method) be used instead. In some cases, measurement data on emissions from mines may be unavailable but a country will still seek to develop a narrower estimate based on other types of available data. In such cases, a country may seek to develop a simple emissions model based on physical principles or make judgements based on an evaluation of available data. Among the key types of data that should be considered in such a model or evaluation are:

• the gas content of the coal, which contributes to the total amount of methane available for emission during mining;

• the amount of coal within the strata above and below the mined coal seam, which also contributes to the total amount of methane available for emission during mining; and,

• the method of mining, which determines the amount of ground that is disturbed by mining the coal and the extent to which the mining process liberates methane contained in the mined coal seam and in the strata surrounding it. It should be noted that while the Tier 2 approach can provide some additional information about methane emissions in a particular country or coal basin, the estimates will still be quite uncertain because of the absence of comprehensive and reliable emissions data. This approach should thus be used only in cases where there is a strong need to make an estimate drawn from a narrower range than the Tier 1 (Global Average Method) and not enough data are available to prepare an estimate using the Tier 3 (Mine Specific Method) described in the next section. It should further be noted that an estimate from the narrower range will not necessarily be more accurate than that developed under Tier 1. In all cases where the Tier 2 approach is used, a detailed discussion of the types of data available and the manner used to determine the refined range of emission factors should be presented, so as to allow for the independent verification of the estimate and ensure comparability with estimates being prepared by other countries.
Tier 3: Mine Specific Method Because methane is a serious safety hazard in underground mines, many countries have collected data on methane emissions from mine ventilation systems, and some also collect data on methane emissions from mine degasification systems. Where such data are available, the more detailed Tier 3 approach – called the "Mine Specific Method" – should provide the most accurate estimate of methane emissions from underground mines. Since these data have been collected for safety, not environmental reasons, however, it is necessary to ensure that they account for total emissions from coal mines. The key issues that should be considered when using mine safety data, as well as the recommendations of the IPCC for resolving them, are shown in Table 1-55.

27 If measurement data is available for most or all or a country's underground coal mines, the Tier 3 approach – called the "Mine Specific Method" – should be used to estimate emissions



### .

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.107 Treatment of Methane Utilisation All of the methods described above, with the possible exception of the Mine Specific Method, assume that all of the methane liberated by mining will be emitted to the atmosphere. In many countries, however, some of the methane recovered by mine degasification systems is used as fuel instead of being emitted. Wherever possible, the emission estimates should be corrected for the amount of methane that is used as fuel, by subtracting this amount from total estimated emissions. In several countries, data on the disposition of methane recovered by degasification systems (i.e., whether it is used or emitted to the atmosphere) can be obtained from the coal industry or energy ministries. Poland, for example, reports that its mine degasification systems recovered 286 million m 3 of methane in 1989, of which 201 million

m 3 was used and the remaining 85 million m 3 was emitted to the atmosphere (Polish Central Mining Institute, 1990). Regardless of the method used to develop the emissions estimates, the Polish emission estimate should be adjusted to reflect the use of methane by subtracting 201 million m 3 from total emissions. In some countries figures for the quantity of gas recovered from mines may not be available from the mining industry. Nevertheless estimates may be constructed if the users of the gas are known and they are able to give data for their consumption. Consumption may also be inferred if it is known that the gas is used to fuel a particular plant of a known capacity (e.g. if the methane is used to fuel a gas turbine of a known size).

T ABLE 1-55 K EY I SSUES F OR C ONSIDERATION W HEN U SING T IER 3 – M INE S PECIFIC M ETHOD
ISSUE DESCRIPTION RECOMMENDATION

Where and how are ventilation system emissions monitored? When used to develop overall methane emission estimates, the optimal location for ventilation air monitors is at the point where ventilation air exhausts to the atmosphere. If ventilation emissions are not monitored at the point of exhaust, emission data should be corrected based on estimated additional methane emissions between the point of measurement and the point of exhaust to the atmosphere. Are ventilation system emissions monitored and/or reported for all mines? In some countries, emissions are only reported for "gassy mines". Estimates should be developed for non-gassy mines as well. Estimates can be prepared using information about the definitions of gassy and non-gassy mines and data on the total number of mines and the coal production at these mines.

Are methane emissions from degasification systems reported? Some countries collect and report methane emissions from ventilation and degasification systems, while others only report ventilation system emissions. Both emission sources must be included in emissions estimates. If degasification system emissions are not included, those mines with degasification systems should be identified and estimates prepared on emissions from their degasification systems. Emissions estimates can be based on knowledge about the efficiency of the degasification system in use at the mine or the average efficiency of degasification in the country.

The sources of any adjustments to emissions that are made to reflect the utilisation of methane should be clearly specified, to permit the independent verification of the emissions estimates

. In the absence of data, estimated adjustments for the use of methane should not be undertaken

.

## E NERGY

1.108 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.7.2.3 S URFACE 

### M INING Two possible approaches for estimating methane emissions from surface mining are suggested by the IPCC

. For the most part, these approaches resemble those developed for underground mining, but the results will be much more uncertain due to the absence of emissions data

. Methane emissions from surface mining are assumed to arise from two sources: the coal mined and the surrounding strata exposed during the mining process

. In the Tier 1 approach, (Global Average Method) the separation of these sources is ignored and a single emission factor is used

. In the Tier 2 approach (Country or Basin Specific Method), emission factors for each source are required. If emissions measurements are developed in the future, it should be possible to refine these methodologies.
Tier 1: Global Average Method As for underground mining, the simplest Tier 1 approach for surface mines – called the "Global Average Method" – is to multiply surface coal production by an emission factor selected from a global range, within which most emission factors are believed to lie.

E QUATION 2 T IER 1: G LOBAL A VERAGE M ETHOD – S URFACE M INES CH 4 Emissions (Gg) = CH 4 Emission Factor (m 3 CH 4 /tonne of coal mined) x Surface Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 ) Where:

• the Emission Factor should be chosen from the following range: Low CH 4 Emission Factor = 0.3 m 3 /tonne High CH 4 Emission Factor = 2.0 m 3 /tonne

• Conversion Factor converts the volume of CH 4 to a weight measure, and is the density of methane at 20°C and 1 atmosphere, namely: 0.67 Gg/ 10 6 m 3

In the original IPCC methodology, an average emission factor of 2.5 m 3 /tonne was recommended (OECD, 1991), based on the results of Boyer et al. (1990) and including emissions from post-mining operations. Based on more recent analyses and additional studies, a revised emission factor range of 0.3 to 2.0 m 3 /tonne is recommended by the IPCC, not including post-mining emissions (US EPA, 1993c; CIAB, 1992; BCTSRE, 1992; CMRC, 1990; Kirchgessner et al., 1993).
Given the lack of information and measurements on methane emissions from surface mines, this range must be considered extremely uncertain, and it should be refined in the future as more data become available.
Tier 2: Country or Basin Specific Method A second tier estimation of methane emissions – called the "Country or Basin Specific Method" – can be used if additional information is available on in-situ methane content and other characteristics of a country's surface-mined coals

. This approach enables a country to develop emission factors that better reflect specific conditions in their countries

.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.109 Depending on the degree of detail desired, emissions can be estimated for specific coal basins or countries, using the equation below.

E QUATION 3 T IER 2: C OUNTRY OR B ASIN S PECIFIC M ETHOD – S URFACE M INES CH 4 Emissions (Gg) = [ In-Situ Gas Content (m 3 CH 4 /tonne) x Surface Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 )] + [Assumed Emission Factor for Surrounding Strata (m 3 CH 4 /tonne) x Surface Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 )] Where:

• In-Situ Gas Content and Assumed Emission Factor for Surrounding Strata are described in the text.

• Conversion Factor converts the volume of CH 4 to a weight measure and is the density of methane at 20°C and 1 atmosphere, namely: 0.67 Gg /10 6 m 3

In Equation 3, In-Situ Gas Content represents the methane actually contained in the coal being mined, as determined by measuring the gas content of coal samples

. Average values for a coal mine, coal basin or country could be developed, depending on the level of detail in the estimate

. For surface mines, unlike underground mines, it is frequently assumedthat all of the methane contained in the coal is released during mining and that postmining emissions from surface-mined coals are effectively zero (BTSCRE, 1992; CIAB, 1992; CMRC, 1990)

. Some countries may choose to modify this assumption based on their specific conditions

. Care should be taken, however, to ensure that any emissions assumed to occur during post-mining activities are subsequently estimated.
Assumed Emission Factor for Surrounding Strata represents the possibility that more methane will be emitted during surface mining than is contained in the coal itself because of emissions from the strata below (or in limited cases, above) the coal seam

. Some countries have assumed that there are no emissions from surrounding strata associated with surface-mined coals (BTSCRE, 1992; CMRC, 1990)

. However, if available information indicates that there are gas-bearing strata surrounding the mined coal seam and that these strata are emitting their gas in conjunction with the mining, countries should include these emissions in their estimates.
Emission factors for the surrounding strata can be developed using one of two approaches

. Ideally, the assumed emission factor should be based on an evaluation of the gas content of the surrounding strata and verified by measurements

. If such data are unavailable, an alternative method of developing an emission factor is to assume that some multiple of the gas content of the mined coal is emitted by the surrounding strata

. It should be noted, however, that the alternative approach is highly speculative given the lack of data upon which to base such an assumption.

## E NERGY

1.110 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.7.2.4 P OST 

### - M INING Like surface mining emissions, there are currently few measurements of methane emissions from post-mining activities

. In fact, many past studies have overlooked this emission source, while others have developed only rudimentary estimation methodologies

. Two possible approaches for estimating emissions from post-mining activities are recommended by the IPCC.
Tier 1: Global Average Method For the most simple estimates, a global average emission factor can be multiplied by coal production for underground and surface mining, as shown in the equation below

. It is important to distinguish between underground- and surface-mined coals because the gas contents are likely to be very different and hence emissions could vary significantly.

E QUATION 4 T IER 1: G LOBAL A VERAGE M ETHOD – P OST -M INING A CTIVITIES Underground CH 4 Emissions (Gg) = CH 4 Emission Factor (m 3 CH 4 /tonne of coal mined) x Underground Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 )
Surface CH 4 Emissions (Gg) = CH 4 Emission Factor (m 3 CH 4 /tonne of coal mined) x Surface Coal Production (Mt) x Conversion Factor (Gg/10 6 m 3 )

Where:

• Underground CH 4 Emission Factors are in the range of: 0.9 to 4.0 m 3 /tonne

• Surface CH 4 Emission Factors are in the range of: 0 to 0.2 m 3 /tonne

• Conversion Factor converts the volume of CH 4 to a weight measure and is the density of methane at 20°C and 1 atmosphere, namely: 0.67 Gg/10 6 m 3

Underground-Mined Coals: The IPCC recommends emission factors of 0.9 to 4.0 m 3 /tonne for underground-mined coal, based on recent studies (CIAB, 1992; BCTSRE, 1992; US EPA, 1993c).
Surface-Mined Coals: Emission factors of 0 to 0.2 m 3 /tonne are recommended by the IPCC for post-mining activities involving surface-mined coal (CIAB, 1992; CMRC, 1990; US EPA, 1993c).
Tier 2: Country or Basin Specific Method
Emissions estimates can be refined if additional data are available on coal characteristics

. This method may be preferable if higher tier methods have been used to estimate emissions from underground and surface mines

. The equation below summarises the approach for preparing refined emission estimates.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.111 E QUATION 5 T IER 2: C OUNTRY OR B ASIN S PECIFIC M ETHOD – P OST -M INING A CTIVITIES a) Underground CH 4 Emissions (Gg) = In-Situ Gas Content (m 3 CH 4 /tonne) x Underground Coal Production (Mt) x Fraction of Gas Released During

Post-Mining Activities (%) x Conversion Factor (Gg/10 6 m 3 )

When Necessary: b ) Surface CH 4 Emissions (Gg) = In-Situ Gas Content (m 3 CH 4 /tonne) x Surface Coal Production (Mt) x Fraction of Gas Released During

Post-Mining Activities (%) x Conversion Factor (Gg/10 6 m 3 ) Where:

• In-Situ Gas Content and Fraction of Gas Released During Mining are described in the text

• Conversion Factor converts the volume of CH 4 to a weight measure and is the density of methane at 20°C and 1 atmosphere, namely: 0.67 Gg/10 6 m 3

In-Situ Gas Content represents the methane actually contained in the coal being mined, as determined by measuring gas contents in coal samples

. Average values for a coal mine, coal basin or country could be developed, depending on the level of detail in the estimate. Fraction of Gas Released During Post-Mining Activities represents the percentage of the in-situ gas content that is assumed to be emitted during post-mining activities

. There are three key issues related to the estimation of this fraction:

• For Surface-Mined Coal: In most cases, if the Tier 2 approach is used to estimate methane emissions from surface mines, post-mining emissions from surface-mined coals are assumed to be zero

. In these cases, the use of Equation 5(b) is unnecessary and countries should be careful to avoid double counting

. However , if a country has not assumed that all of the methane contained in surface-mined coal is released during mining, Equation 5(b) should be used to estimate post-mining emissions and the value selected for "Fraction of Gas Released During Post-Mining Activities" should be consistent with the emission factor selected to estimate emissions during surface mining.

• For Underground-Mined Coal: The assumed fractions for underground mining will be based on information about coal permeability, desorption rates, mining methods and other factors

. Recent studies have assumed that 25 to 40 per cent of the in-situ CH 4 content of underground mined coal is emitted during post-mining activities (US EPA, 1993a; BCTSRE, 1992)

.

• Fraction of Methane Not Emitted: It is currently assumed that all of the CH 4 contained in mined coal will be emitted to the atmosphere, although it is possible that a fraction could remain in the coal until the point of combustion and be burned instead of emitted

. At this time, estimates of the extent to which this may be the

## E NERGY

1.112 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual case have not been developed

. If countries have such information, however, they could further incorporate this factor into Equation 5.
Total Emissions from Coal Mining Activities Total methane released as a result of coal mining activities will be the summation of emissions from underground mining (ventilation and degasification systems), surface mining, and post-mining activities

. The IPCC recommends that emissions be estimated for each of these categories, in tonnes of CH 4 , then aggregated to determine total national methane releases

. To the extent that methane that would otherwise have been released to the atmosphere is recovered and used as fuel, the recovered quantity and its use should be reported and the quantity subtracted from the emission total.
Availability and Quality of Activity Data Data are readily available to develop general emissions estimates using the Tier 1 approach – the Global Average Methods – for underground, surface mining as well as post-mining activities

. For these estimates, the only data required are country statistics on underground and surface coal production, which are available from domestic sources, such as energy ministries, or from the OECD/IEA, which publishes Coal Information (OECD/IEA, 1996)

. The IPCC recommends that countries involve their coal mining personnel in the development of emissions estimates as much as possible, because of the improved accuracy of emissions estimates prepared with more detailed coal and mining data

. The availability and quality of data collected by mining personnel for mine safety purposes should be assessed on a case-by-case basis, however, to ensure that it can be used appropriately for preparing emissions estimates. The IPCC further recommends that future efforts attempt to better characterise the factors affecting methane emissions from coal mining for those countries and emission sources with limited data, so as to develop more refined emission factors

. Specific activities should include:

• Obtaining more data on coal and geological characteristics in selected coal-producing countries;

• Monitoring emissions from surface mines and post-mining activities; and,

• Monitoring emissions from closed or inactive mining operations, and some other potential methane sources, such as mine water.



### 1.7.3 CO 2 

### Emissions From Coal Mining and Handling

1.7.3.1 B URNING 

### C OAL 

### D EPOSITS 

### A ND 

### W ASTE 

### P ILES Marland and Rotty (1984) estimated that burning of coal in coal deposits is less than 0.3 per cent of total coal produced and that burning of all coal in waste banks in the United States over a ten year period would represent less than 1 per cent of US coal consumption

. Subsequently, they chose to ignore these emissions

. If these sources are estimated, the amount of coal burned in waste piles and coal deposits must be specified along with an emission factor that represents the percentage of coal

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.113 that is carbon times the percentage of carbon oxidised

. We suggest an arbitrary value of 50 per cent of the carbon present in the coal to represent this emission factor; this value would be highly variable from one country to another and one site to another

. This assumption of 50 per cent for an emission factor should be evaluated to determine its validity

. The formula for calculating these emissions would be:

E QUATION 6 Emissions from Coal Burning (Gg C) = Quantity of Coal Burned (10 3 t) x Emission Factor Where:

• The Emission Factor is: Percentage of Carbon in Coal x Percentage of Carbon Oxidised;

(and the default value is 50%)

Note that other GHGs such as N 2 O, CO, NO x , etc. are also emitted from combustion of coal wastes.



### 1.7.3.2 SO 2 

### S CRUBBING

When SO 2 scrubbing (or flue gas desulphurisation) technology is used in conjunction with combustion of coal, the process, which removes sulphur dioxide from the flue gas, also releases CO 2 from the chemical reactions during the process

. This can be considered a fugitive emission resulting from coal use

. Typically, calcium carbonate reacts with sulphur oxides in flue gas to produce calcium sulphate and carbon dioxide

. Marland and Rotty (1984) suggest that CO 2 emissions from SO 2 scrubbing are small enough to be ignored in global calculations

. However, for completeness, some national experts may wish to include this subcategory

. To estimate carbon emissions from SO 2 scrubbing, the approach is derived from Grubb (1989) with slight modifications

. In Grubb's approach, carbon emissions would equal the total amount of coal combusted in plants equipped with scrubbers times the fraction of sulphur by weight in the coal, adjusted for the differences in molecular weight between carbon and sulphur (12/32)

. Since this procedure assumes that all of the sulphur is removed, it should be adjusted by the sulphur removal efficiency of the desulphurisation process (an average removal efficiency of 90 per cent is suggested)

. The formula for calculating these emissions would be:

E QUATION 7 Emissions from SO 2 Scrubbing (Gg C) = Total Coal Consumption (10 3 t) x Fraction burned in plants equipped with scrubbers(%) x Average Sulphur Content of Coal in these plants (%) x Sulphur Removal Efficiency (default value is 90%) x 12/32 (i.e., the Carbon/Sulphur Ratio)

Finally, to convert from carbon emissions (in Gg) into CO 2 emissions (in Gg), it is necessary to multiply by 44/12, the molecular weight ratio of CO 2 to C.

## E NERGY

1.114 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 1.8 Fugitive Emissions from Oil And Natural Gas Activities

1.8.1 Overview This section covers fugitive emissions of greenhouse gases (GHGs) from oil and natural gas activities

. The category includes all emissions from the production, processing, transport and use of oil and natural gas, and from non-productive combustion

. It excludes use of oil and gas or derived fuel products to provide energy for internal use, in energy production processing and transport

. The latter are considered fuel combustion and treated in an earlier section of this chapter

. Fugitive emissions do include, however, emissions which result from the combustion of natural gas during flaring operations. By far the most important components of this subcategory are methane emissions from oil and gas production, and from all aspects of natural gas activities

. The majority of this section identifies and describes different methane emission sources from oil and natural gas, and presents a default methodology to estimate these emissions on a national level

. The basis for estimating methane emissions from oil and gas is, however, weak for most regions at this time

. Only a few detailed studies of emissions rates have been performed

. Better emissions data that take into account region- and country-specific factors are needed

. Information currently available indicates that gas production and transmission in the former USSR and Eastern Europe are by far the most important sources, accounting for perhaps 50 per cent of global CH 4 emissions from oil and natural gas. Because the data are so limited at present, global and regional estimates of CH 4 emissions from this source category should be considered highly uncertain. The IPCC/OECD/IEA programme has not yet addressed the indirect GHGs (including NMVOCs) in detail. However, the Joint EMEP/CORINAIR method offers both a simplified and a more detailed approach to the estimation of ozone precursors and SO 2 . Considerable information has been obtained in other national and international emissions inventory programmes for NMVOCs because of the importance of these gases for local and regional (as well as global) pollution. References to some of the available sources of emission factor data and other information for calculating emissions from this category are provided in the last subsection of this section.
Background Fugitive emissions of methane from oil and gas activities probably account for about 30 to 60 Tg per year of global methane emissions. Sources of fugitive emissions within oil and gas systems include: releases during normal operation, such as emissions associated with venting and flaring, chronic leaks or discharges from process vents, emissions during maintenance, and emissions during system upsets and accidents.



### 1.8.2 Oil and Natural Gas Activities Oil and gas activities are divided into three main parts, for this discussion:
1 Oil and Gas Production : Oil and gas are withdrawn from underground formations using on-shore and off-shore wells and are often taken simultaneously from the same geological formation, and then separated. Gathering lines are generally used to bring the crude oil and raw gas streams to one or more collection

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.115 point(s) within a production field. Because methane is the major component of natural gas, leaks or venting from these systems result in methane emissions. Oil and/or gas are produced in approximately 186 countries world-wide. 2 Crude Oil Transportation and Refining : Crude oil is transported by pipelines and tankers to refineries where it is stored in tanks for a period of time. Methane is present, in varying degrees, in crude oil, and leaks or venting of vapours during transport and storage result in methane emissions, particularly from crude oil tankering. Refineries process crude oil into a variety of hydrocarbon products such as gasoline and kerosene. During the refining process, dissolved gases are separated some of which may be leaked or vented during processing. Refinery outputs, referred to as "refined products," generally contain negligible amounts of methane. Consequently, methane emissions are not estimated for transporting and distributing refined products. Refineries are operated in 102 countries. 3 Natural Gas Processing, Transportation, and Distribution : Natural gas is processed to recover heavier hydrocarbons, such as ethane, propane and butane, and to prepare the “dried” gas for transport to consumers. Most gas is transported through transmission and distribution pipelines. A small amount of gas is shipped by tanker as liquefied natural gas (LNG). Because for the time being only a small portion of gas is transported as LNG, emissions from LNG facilities are not included in default emission methods. The following are the main processing, transportation, and distribution activities:

• Gas processing plant: Natural gas is usually processed in gas plants to produce products with specific characteristics. Depending on the composition of the unprocessed gas, a variety of processes may be used to remove most of the heavier hydrocarbons, or condensate, from the gas. The processed, marketable, gas is then injected into the natural gas transmission system and the heavier hydrocarbons are marketed separately. Unintentional leaks of methane occur during natural gas processing.

• Transmission pipelines: Transmission facilities are high pressure lines that transport gas from production fields, processing plants, storage facilities, and other sources of supply over long distances to distribution centres, or large volume customers. Although transmission lines are usually buried, a variety of above-ground facilities support the overall system including metering stations, maintenance facilities, and compressor stations located along the pipeline routes. These activities use gas from the pipeline as fuel and may emit methane.

• Distribution systems: Distribution pipelines are extensive networks of generally small diameter, low pressure pipelines. Gas enters distribution networks from transmission systems at "gate stations" where the pressure is reduced for distribution within cities or towns. As with transmission pipelines emissions from leaks or supporting facilities may take place.



### 1.8.3 Sources of Methane Emissions from Oil and Natural Gas Activities Emissions from oil and gas activities can be categorised into: (1) emissions during normal operations; (2) maintenance; and (3) system upsets and accidents. Typically the majority of emissions are from normal operations.

## E NERGY

1.116 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1 Normal Operations: . Emissions from normal operations can be divided into two main source categories: (1) venting and flaring and (2) discharges from process vents, chronic leaks, etc. Venting and Flaring - Venting and flaring refers to the disposal of gas that cannot be contained or otherwise handled. Such venting and flaring activities are associated with combined oil and gas production and take place in production areas where gas pipeline infrastructure is incomplete and the natural gas is not injected into reservoirs (emissions from process vents are not included here - see below). Venting activities release methane because the vented gas typically has a high methane content. If the excess gas is burned in flares the emissions of methane will depend on how efficient the burning processes are. Generally the combustion efficiency for flare sources are assumed to be between 95 and 100 per cent. However a new study based upon measurements carried out by Norwegian Oil Industry Association - OLF (1993) indicates very small amounts of unburned methane from flares, less than 0.1 per cent of the gas flared. To estimate the methane emissions from venting and flaring activities satisfactorily it is required to know the flare efficiency rates and the division between the quantity of gas vented and gas flared.
The combined quantity of gas vented and flared is reported by countries that produce oil and gas (Barns and Edmonds, 1990). A few countries also are able to report separately gas vented and gas flared. The reliability of the data is questionable in many cases because vented and flared amounts are not normally metered but inferred from the difference between total production and disposals. Discharges from Process Vents, Chronic Leaks etc. - These include:

• Emissions from pneumatic devices (gas-operated controls such as valves and actuators) depend on the size, type, age of the devices, the frequency of their operation and the quality of their maintenance.

• Leaks from system components are unintentional and usually continuous releases resulting from the failure of a seal or the development of a flaw, crack or hole in a component designed to contain or convey oil or gas. Connections, valves, flanges, instruments, and compressor shafts can develop leaks from flawed or worn seals, while pipelines and storage tanks can develop leaks from cracks or from corrosion.

• Emissions from process vents, such as vents on glycol dehydrators and vents on crude oil tankers and storage tanks resulting from normal operation of the facilities. However such process vents are minor methane sources in most gas production facilities.

• Emissions from starting and stopping reciprocating engines and turbines.

• Emissions during drilling activities, e.g., gas migration from reservoirs through wells.
2 Maintenance: Includes regular and periodic activities performed in the operation of the facility. These activities may be conducted frequently, such as launching and receiving scrapers (“pigs”) in a pipeline, or infrequently, such as evacuation of pipes ("blowdown") for periodic testing. In each case, the required procedures release gas from the affected equipment. Releases also occur during maintenance of wells ("well workovers") and during replacement or maintenance of fittings. 3 System Upsets and Accidents: System upsets are unplanned events in the system, the most common of which is a sudden pressure surge resulting from the failure of a pressure regulator. The potential for unplanned pressure surges is

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.117 considered during facility design, and facilities are provided with pressure relief systems to protect the equipment from damage due to the increased pressure. Relief systems vary in design. In some cases, gases released through relief valves may be collected and transported to a flare for combustion or re-compressed and re-injected into the system. In these cases, methane emissions associated with pressure relief events will be small. In older facilities, relief systems may vent gases directly into the atmosphere or may send gases to flare systems where complete combustion may not be achieved. The frequency of system upsets varies with the facility design and operating practices. In particular, facilities operating well below capacity are less likely to experience system upsets and resulting emissions. Emissions associated with accidents are also included under the category of upsets. Occasionally, gas transmission and distribution pipelines are accidentally ruptured by construction equipment or other activities. Table 1-56 lists the most important sources of emissions within each segment of the oil and gas industry. Based on available information, the sources listed as "major" account for the majority of emissions from each segment. Because data are limited and, because there is considerable diversity among oil and gas systems throughout the world, other possible sources are listed which may, in some cases, be important contributors to emissions.

T ABLE 1-56 M ETHANE E MISSIONS FROM O IL AND N ATURAL G AS A CTIVITIES Segment Major Emission Sources Other Possible Emission Sources
Oil and Gas Production Oil and Gas Wells Gathering lines Treatment facilities Venting Normal operations: fugitive emissions; deliberate releases from pneumatic devices and process
vents Flaring, maintenance, system upsets and accidents

Crude oil transportation and Refining Pipelines Tankers Storage tanks Refineries Normal operations: fugitive emissions; deliberate releases from process vents at refineries, during loading and unloading of tankers and storage tanks Flaring, maintenance, system upsets and accidents

Natural Gas Processing, Transportation, and Distribution Gas Plants Underground storage reservoirs Transmission Pipelines Distribution Pipelines Normal operations: fugitive emissions; deliberate releases from pneumatic devices and process
vents Flaring, maintenance, system upsets and accidents



### 1.8.4 Available Emissions Data Only very limited data are available that describe methane emissions from natural gas and oil activities. Estimating the types of emissions defined above is complicated by the fact

## E NERGY

1.118 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual that emissions rates from similar activities in various regions and countries are influenced by differences in the industry's supporting infrastructure, operating and maintenance practices, and level of technology used. Because natural gas and oil activities are complex, it is not easy to define simple relationships between emissions and gross descriptors of the activities undertaken. The available published data were reviewed to identify emissions estimates that include: a detailed consideration of the physical attributes of oil and gas systems; the operation and maintenance characteristics of key facilities; and country- or region-specific factors that may influence emission rates. The following data were identified:

• Surveys: Several studies have surveyed system operators to estimate emissions as a fraction of production or throughput. These studies include Alphatania (1989), AGA (1989), and INGAA (1989). While these studies provide a basis for identifying the activities that operators believe are likely to be major sources of emissions, they are not based on detailed assessments of emission rates and therefore do not provide a quantitative basis for making estimates of methane emissions from oil and natural gas activities.

• Estimates Based on “Reported Unaccounted For Gas”: Several studies, such as Hitchcock and Wechsler (1972), Abrahamson (1989) and Cicerone and Oremland (1988), have assumed that emissions can be approximated by reported amounts of "unaccounted for" gas. Unaccounted for gas is defined as the difference between gas production and gas consumption on an annual basis. Like estimates of venting and flaring, unaccounted for gas often is used as an accounting convenience to balance company or national production and consumption estimates. The use of unaccounted for gas estimates as estimates of emissions is questionable because factors other than emissions account for the majority of the gas listed as unaccounted for. These include: meter inaccuracies, use of gas within the system itself, theft of gas (PG&E, 1990), variations in temperature and pressure and differences in billing cycles and accounting procedures between companies receiving and delivering the gas (INGAA, 1989). Furthermore, because known releases of gas are not reflected in unaccounted for gas estimates, such as emissions from compressor exhaust, the unaccounted for gas estimates cannot unambiguously be considered an upper or lower bound on emissions.

• Engineering Studies and Measurements: A small number of studies are based on detailed engineering and/or field measurement analyses. Several engineering analyses have considered the manner in which actual or model facilities are built and operated, and extrapolate facility emissions to a system-wide basis. Several measurement studies have measured emissions from operating facilities or identified actual leaks and extrapolated these measurements to estimate system-wide emissions. In general, data from engineering studies and measurements are the preferred basis for emission estimates. However, only a few of these types of studies have been performed, thereby limiting the ability to estimate emissions nationally, regionally and globally from oil and gas systems. Table 1-57 lists the studies identified and the information they contain. The methane emissions estimates from the studies in the table have been converted to common units of kilograms of emissions per petajoule of energy (kg/PJ). A total of five studies are listed, with emissions estimates for parts of North America (US EPA, 1992), Eastern Europe (Rabchuk et al., 1991), and Western Europe (Schneider-Fresenius et al., 1989, Norwegian SPCA, 1992b and Norwegian Oil Industry Association OLF, 1993). Additionally, Barns and Edmonds (1990) present estimates based on a global assessment. Further studies are needed to improve the basis for making emissions estimates.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.119 T ABLE 1-57 S UMMARY OF M ETHANE E MISSION F ACTORS Data source Study methodology Emission factors Applicability US EPA (1992) Compilation of estimates from: Oil and Gas Production:
All emissions have been scaled down to 1988 energy consumption or production levels • detailed engineering analyses

• field measurement studies 290 - 4 670 kg/PJ of oil produced Emissions from non-gas producing oil wells including fugitive emissions and maintenance emissions in the USA 39 590 - 104 220 kg/PJ of gas produced Emissions from gas production, including fugitive emissions, dehydrator venting, bleeding from pneumatic devices, maintenance, and systems upsets in the USA
2 870 - 13 920 kg/PJ of total oil and gas produced Venting and flaring emissions from oil and gas production and fugitive emissions from gasproducing oil wells in the USA Crude Oil Transportation and Refining: 110 - 1 666 kg/PJ of oil refined Emissions from oil refining and related oil storage tanks in the USA Natural Gas Processing, Transmission and Distribution: 59 660 - 116 610 kg/PJ of gas consumed Emissions from gas processing, transmission and distribution including fugitive emissions, dehydrator venting, bleeding from pneumatic devices, maintenance, and system upsets in the USA Rabchuk et al. (1991) Compilation of estimates from: Oil and Gas Production:

• previous measurement studies

• official data for 1989 218 000 - 567 600 kg/PJ of gas produced Emissions from leakages at gas wells including routine equipment venting in the former USSR Natural Gas Processing, Transmission and Distribution: 340 000 - 715 800 kg/PJ of gas consumed Emissions from leakages at underground storage facilities, compressor stations, linear part of main pipelines and distribution networks in the former USSR
Schneider-Fresenius et al. (1989) Compilation of results from: Oil and Gas Production:

• Batelle study's 1988 literature survey 14 800 - 270 00 kg/PJ of gas produced Emissions from gas production and treatment facilities in Germany Natural Gas Processing, Transmission and Distribution: 58 000 - 111 000 kg/PJ of gas consumed Emissions from transportation, distribution and storage of gas in Germany

## E NERGY

1.120 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-57 (C ONTINUED ) S UMMARY OF M ETHANE E MISSION F ACTORS Data source Study Methodology Emission Factors Applicability Barns and Edmonds (1990) Compilation of: Oil and Gas Production: official reports and projections on international emissions 96 000 kg/PJ of natural gas production Emissions from gas production and separation facilities in the world 6 300 - 1 019 000 kg/PJ of gas production Emissions from venting and flaring activity by region of the world Norwegian SPCA (1992b) Summary of: Oil and Gas Production:
emissions estimates for 1989 based on: 12 800 kg/PJ of gas produced Emissions from cold vents and fugitive emissions
information and measurements collected from oil companies 3 200 kg/PJ of gas produced Flare and gas turbines

and industry associations 200 kg/PJ of gas produced Pre-production emissions (well testing) Crude oil transportation: 2 500 kg/PJ oil tankered Emissions from offshore loading of crude oil Natural gas processing: 1 800 kg/PJ of gas processed Emissions from one Norwegian gas processing terminal Norwegian Oil Industry Association (OLF), 1993 Summary of emission estimates based on: Oil and Gas Production:

information and measurements collected from oil associations 3 000 - 7 500 kg/PJ of gas produced Emissions from cold vents and fugitive emissions 100 - 400 kg/PJ of gas produced Pre-production emissions



### 1.8.5 Recent Revisions to Emission Factors The above methodology and emission factors are based on the report of an expert group convened to advise the IPCC/OECD/IEA programme on methods and data in this specific area (Ebert, et al., 1993). Since that group delivered its report in mid-1993, a more recent analysis (US EPA, 1994b) has provided a somewhat different interpretation of some emission factors. While this very detailed analysis endorses the basic tiered methodology included in this Manual , the emission factors it derives differ from those presented here. This evaluation was based on essentially the same set of measurement data as cited in this Manual , but draws different results from the limited available data. The results of the recent US EPA analysis are summarised in Table 1-58. The most significant differences are in natural gas processing, transportation and distribution, where a more detailed set of emission factor ranges are recommended for non-OECD countries, some which are based on production of natural gas and some which are based on consumption of natural gas (which is the case for all of the factors provided above). Where emission factors are provided for more than one subcategory, they are intended to be additive, and would result in a higher total emissions estimates. Other differences in this US EPA analysis are that venting and flaring emissions for Western Europe are based on oil rather than gas production, and there are minor revisions to some factors for fugitive and other emissions from gas production. These differences are significant, even given the overall uncertainty in this category, and should be considered carefully by national experts in regions where emissions from this

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.121 source category are significant. It is hoped that the differences can be resolved or explained in more detail in a subsequent version of these Guidelines

.

T ABLE 1-58 R EVISED R EGIONAL E MISSION F ACTORS F OR M ETHANE F ROM O IL A ND G AS A CTIVITIES (kg/PJ)

Source Type Basis Western Europe US & Canada Former USSR, Central & Eastern Europe Other Oil Exporting Countries Rest of the World

OIL & GAS PRODUCTION Fugitive and Other Maintenance Emissions from Oil Production Oil Produced 300 - 5 000 300 - 5 000 300 - 5 000 300 - 5 000 300 - 5 000

Fugitive and Other Maintenance Emissions from Gas Production Gas Produced 15 000 - 27 000 46 000 - 84 000 140 000 - 314 000 46 000 - 96 000 46 000 - 96 000

Venting & Flaring from Oil and Gas Production Oil & Gas Produced (a) - 3 000 - 14 000 -

- -

Oil Produced 1 000 - 3 000 - -

- - Gas Produced - - 6 000 - 30 000 758 000 - 1 046 000 175 000 - 209 000 CRUDE OIL TRANSPORTATION, STORAGE AND REFINING Transportation Oil Tankered 745 745 745 745 745 Refining Oil Refined 90 - 1 400 90 - 1 400 90 - 1 400 90 - 1 400 90 - 1 400 Storage Tanks Oil Refined 20 - 250 20 - 250 20 - 250 20 - 250 20 - 250 NATURAL GAS PROCESSING, TRANSPORT AND DISTRIBUTION
Emissions from Processing, Distribution and Transmission Gas Produced - - 288 000 - 628 000 288 000 (high) (b) 288 000 (high) (b)

Gas Consumed 72 000 - 133 000 57 000 - 118 000 - 118 000 (low) (c) 118 000 (low) (c)
Leakage at industrial plants and power stations Non-residential Gas Consumed (d) - - 175 000 - 384 000 0 - 175 000 0 - 175 000
Leakage in the residential and commercial sectors Residential Gas Consumed (e) - - 87 000 - 192 000 0 - 87 000 0 - 87 000
(a) In the US and Canada, the emissions are based on total production of both oil and gas produced. (b) The emission factor of 288 000 kg/PJ of gas produced is used only for the high emissions estimate. (c) The emission factor of 118 000 kg/PJ of gas consumed is used only for the low emissions estimate. (d) Gas consumption by utilities and industries. (e) Gas consumption by the residential and commercial sectors. Source: US EPA (1994b).

## E NERGY

1.122 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.8.6 Methodologies For Estimating Methane Emissions A three-tiered approach is presented for estimating methane emissions from oil and gas activities. The specific tiers are listed below in the order of increasing sophistication, data requirements, and accuracy:

• Tier 1 - Production-Based Average Emission Factors Approach,

• Tier 2 - Mass Balance Approach, and

• Tier 3 - Rigorous Source-Specific Approach. Countries should select the approach or combination of approaches that is most suited to their circumstances. Some important considerations may include the relative contribution of oil and natural gas to total methane emissions for the country, the available information and resources, and the complexity of the local oil and gas industry. Regardless of the method that is used, the results must be aggregated back to a Tier 1 format to provide a consistent basis for comparison. Note that methane emissions from combustion plant and incomplete combustion in flaring processes in the non-oil and gas industry are excluded. They are accounted for separately in the section on methane emissions from combustion and industry. Tier 1 - Production-Based Average Emission Factors Approach This is the simplest approach for estimating CH 4 emission from oil and gas activities, and is the only one that does not require any direct interaction with the oil and gas industry and associated regulatory agencies. Accordingly, it is the least reliable of the methods. The required activity data may be easily referenced from published documents of the IEA or the United Nations Statistical Division, and the necessary emission factors are provided in this document. The Tier 1 Approach can be used as a starting point for any country, and may be all that is needed where the emissions from a country's oil and gas industry are comparatively small and/or where data or resources are not available to pursue a more rigorous approach.
Production Base: To estimate emissions, the following steps are recommended as a default estimation procedure: 1 Global oil and gas systems have been divided into regions with relatively homogeneous oil and gas system characteristics. Each country should decide which system characterisation best fits its own oil and gas system(s). 2 For each region, representative emission factors for each activity within each segment have been selected with the objective of taking into account the various system designs and operating practices found in each region. 3 For each country, country-specific activity levels must be obtained and multiplied by the appropriate emission factor. Emission factors for countries should be selected from those corresponding to the appropriate region. As more data become available for oil and gas producing activities within different countries, the default methodology described above (including activity data and emission factors) should be refined. Each step is discussed below in more detail. Regional Definitions: Regions have been defined considering the limitations in data on emission factors and activity levels, but also recognising the key differences in oil and gas systems that are found globally. The following five regions are recommended at this time:

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.123 • USA and Canada: The United States is a large producer and importer of oil and is a large producer of gas. Detailed emissions estimates are available for the United States.

• Former USSR and Eastern Europe: Indications are that emission rates from this region are much higher than emission rates from other regions, in particular for the gas system. This region includes the former USSR (which is by far the largest oil and gas producer in the region), Albania, Bulgaria, Czech & Slovak Republics, Hungary, Poland, Romania, and the former Yugoslavia.

• Western Europe: This region is a net importer of oil and gas, and mainly produces oil and gas off shore. This region includes: Austria, Belgium, Denmark, Faroe Islands, Finland, France, Germany, Gibraltar, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom.

• Other Oil Exporting Countries: This region includes the world's other major oil producing countries: the 11 OPEC members (Algeria, Libya, Nigeria, Venezuela, Indonesia, Iran, Iraq, Kuwait, Qatar, Saudi Arabia and the United Arab Emirates), Gabon, Ecuador and Mexico. Generally, these countries produce large quantities of oil and have limited markets for gas.

• Rest of the World: This region includes the remaining countries of Asia, Africa, Middle East, Oceania and Latin America. In defining these regions, countries with relatively similar oil and gas systems were aggregated. Additional investigation would likely improve the definition of the regions.
Emission Factors: As discussed above, the basis for selecting emission factors is weak because very few detailed studies of emissions have been performed. Using the information summarised in Table 1-57, emission factors should be selected by industry segment and emission type for each of the regions. In some cases data from the United States were used when region-specific information was not available.
Tables 1-60 to 1-64 offer emission factors for each region. Emission factors from US EPA (1992) were used for the United States. Key emission factors for Eastern Europe and the Former USSR were taken from Rabchuk et al. (1990) and Barns and Edmonds (1990). Estimates were used for emission factors for venting and flaring for the several regions, including Eastern Europe. Studies by Schneider-Fresenius et al. (1989) and Norwegian SPCA (1992b) were adopted as representative of emission factors for Western European gas production, venting and flaring. No region-specific data were available for the Other Oil Exporting countries and the Rest of the World. Emission factors in these regions are expected to fall between the relatively low rates found in North America and Western Europe and the relatively high rates found in Eastern Europe. Consequently, a range of emission factors is suggested for these regions unless more information can be obtained. Activity Levels: Data on the quantity of oil and gas produced, refined, and consumed can be obtained from the IEA or the UN Statistical Division. Sources are described in Section 1.2.1 Data Sources. Data on oil refining capacity can be used to approximate oil refined. Data on oil tankered were not available by region. It is important for national experts to ensure that production figures used in calculation of apparent consumption for CO 2 emissions estimates (described in the Tier 1 method for CO 2 ) are consistent with those used in this section.

## E NERGY

1.124 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Tier 2 - Mass Balance Approach The Mass Balance Approach is only recommended for oil system releases of CH 4 , and should not be used for releases from natural gas activities. No Tier 2 method exists for natural gas activities. This is a priority for future work. The Mass Balance Approachemploys standard, generally easy-to-obtain, oil and gas data (i.e., production volumes, gasto-oil ratios (GORs), and gas compositions) to estimate the maximum amount of methane that could be emitted to the atmosphere by different sectors of the oil and gas industry. These amounts are then scaled to reflect actual emissions by applying appropriate emission factors. The minimum emission factors account for the amount of gas that is disposed of by control devices, consumed by combustion equipment, conserved, or reinjected. Leak emission factors account for the amounts lost through leaks from these control/utilisation systems. The basic procedures for performing the mass balance calculations for each oil and gas activity are set out below. Total CH 4 emissions is the sum of emissions for each of these activities. Default data and factors are provided where possible.
Oil Production: Emissions from oil production may be estimated using the relation,

where
E Oil-P = methane emissions from oil production (Tg/year) Q Oil-P = oil produced (m 3 /year) GOR = gas to oil ratio; defines the amount of gas produced (in volume) per unit of oil produced (in volume). (m 3 /m 3 , or dimensionless).
Y CH 4 = methane Fraction; the volume of gas dissolved in the oil that is methane, on a volume basis, for example, 0.1 m 3 of methane per 1.0 m 3 of gas. (may be considered dimensionless)
K Oil-P = emission factor for oil production, see below (dimensionless)
D GOR = density of methane at the temperature and pressure at which the GOR is estimated, (g/m 3 ). The relevant temperature and pressure may vary, depending on the values used to calculate the GOR. For example, at 0°C and a pressure of 1 atmosphere, the density of methane is 715.4 g/m 3 , and at 20°C, and a pressure of 1 atmosphere, the density of methane is 666.6 g/m 3

.

The first two terms (Q Oil-P and GOR) estimate the total amount of gas that is withdrawn from the ground while the oil is produced. The term Y CH 4 converts the total gas quantity into the quantity of methane (still on a volume basis). The emission factor (K Oil-P ) is the fraction of the total gas withdrawn that is emitted. At most, K Oil-P = 1. To put the emissions estimate on a mass basis, D GOR is used to estimate grams, and the conversion to teragrams follows. 

### E Oil-P 

### = × ×× × ×

− − − 

### Q GOR Y K D

Oil P CH Oil P GOR 4 

### 10 12

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.125 The values of the emission factors are determined using the equations presented below.



### K Q QQ Q Q GOR Oil P Gas fuel Gas Inj Gas flared Gas other

Oil P − − −− −

− 

### = − ++ +

× min 

### 1

where,
K Oil-P min = minimum emission factor for oil production (dimensionless) Q Oil-P = oil produced (m 3 /year) GOR = gas to oil ratio (dimensionless) Q Gas-fuel = quantity of gas used as fuel (m 3 /year) Q Gas-flared = quantity of gas flared (m 3 /year) Q Gas-inj = quantity of gas injected back into ground (m 3 /year) Q Gas-other = quantity of gas accounted for in some other manner and that is not emitted (m 3 /year)

The minimum emission is the amount of gas not otherwise accounted for. If no gas is used as fuel, flared, injected, or otherwise handled, then the minimum emission factor is 1; (i.e., all the gas withdrawn from the ground in conjunction with the oil is emitted). If some amount of gas is accounted for, then the minimum emission factor is 1 minus the portion accounted for. Emissions also occur due to leaks. The leak emissions are the amount of gas leaked during various types of handling. If no gas is used as fuel, flared, injected, or otherwise handled, then the leaks are zero. If some amount of gas is managed in these ways, then the leak emission is the amount of gas handled times the leak rate, which is expressed as a fraction. The following is the equation for the leak emission factor: 

# ( ) 

# ( ) ( ) 

# ( ) K Q L Q LQ L Q L Q GOR Oil P Gas fuel fuel Gas inj inj Gas flared flared gas other other

Oil P leak − − −− −

− 

### = × + ×+ × + ×

×

K Oil-P leak = emission factor for leaks in the systems used to handle gas during oil production Q Oil-P = oil produced (m 3 /year) GOR = gas to oil ratio; defines the amount of gas produced (in volume) per unit of oil produced (in volume) (dimensionless) Q Gas-fuel = quantity of gas used as fuel (m 3 /year) Q Gas-flared = quantity of gas flared (m 3 /year) Q gas-inj = quantity of gas injected back into ground (m 3 /year) Q Gas-other = quantity of gas accounted for in some other manner (m 3 /year)
L x = leak rates for the handling of the gas in the various ways, expressed as a fraction (e.g., 0.01) (dimensionless) The total emission factor for oil production is then estimated as: 

### KK K

Oil P Oil P Oil P leak −− − 

### = +
min

## E NERGY

1.126 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual If none of the gas is controlled or utilised (i.e., L x= 1 for all x), then the emission factor (K Oil-P ) is equal to one. This situation occurs when it is not economical to conserve or reinject the gas (e.g., there is no local market for the gas and the volumes are relatively small) and when venting of the gas is preferable to disposal by flaring. It is not then necessary to evaluate the different paths by which CH 4 emissions may occur (e.g., fugitive equipment leaks, process venting, system upsets, etc.) in these cases since the end effect is the same: essentially all the CH 4 produced is emitted to the atmosphere. Crude Oil Transportation and Refining: The crude oil from production facilities will initially contain a certain amount of gas in solution. This gas, particularly the CH 4 fraction, evaporates quickly as this oil progresses through the storage and transportation systems en route to the refinery. When the oil reaches the refinery, it is usually fully weathered and essentially free of any CH 4 . Accordingly, the basic mass balance relation for oil transportation and refining activities may be expressed as follows:
E Oil-T = Q Oil-T x F x Y F-CH 4 x K Oil-T x D F x 10 -12 

### where, E Oil-T = methane emissions from crude oil transportation and refining (Tg/year) Q Oil-T = oil transported and refined (m 3 /year) F = factor defining the amount of gas in solution with the crude oil (per unit of oil by volume) (Dimensionless) 

### Y

F CH

− 4 = methane fraction; the fraction of the gas in solution in the oil that is methane, on a volume basis, for example, 0.1m 3 of methane per 1.0 m 3 of gas. (Dimensionless)
K Oil-T = emission factor for oil transportation and refining, see below. (Dimensionless).
D F = density of methane at the temperature and pressure at which F is estimated (g/m 3 ). The relevant temperature and pressure may vary, depending on the values used to calculate F. For example, at 0°C and at a pressure of 1 atmosphere, the density of methane is 715.4 g/m 3 , and at 20°C and 1 atmosphere, the density of methane is 666.6 g/m 3

. The first two terms (Q Oil-T and F) estimate the total amount of gas that is in solution with the crude oil. The term Y F-CH 4 converts the total gas quantity into the quantity of methane (still on a volume basis). The emission factor (K Oil-T ) is the fraction of the total gas in solution that is emitted (at most, K Oil-T = 1). To put the emissions estimate on a mass basis, D F is used to estimate grams, and the conversion to teragrams follows. The value of the solution gas factor and the corresponding mole fraction of methane is determined by the type of crude oil (light, medium, heavy, or crude bitumen), the composition of the associated gas, and the initial vapour pressure of the crude oil when it is placed in the storage tanks or compartments at the production site. Typically, the initial vapour pressure will be equal to the operating pressure of the first vessel upstream of the storage facilities. Table 1-59 presents some estimated values for these two parameters at onshore and offshore facilities. Better estimates may be determined by performing site specific process simulations.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.127 T ABLE 1-59 S OLUTION G AS F ACTORS AND C ORRESPONDING CH 4 M OLE F RACTIONS FOR D IFFERENT T YPES OF C RUDE O IL P RODUCTION AT O NSHORE AND O FFSHORE F ACILITIES
Type of Crude Oil Onshore and Offshore Facilities
F SOLUTION GAS FACTOR Y F-CH 4 MOLE FRACTION Light 3.3 to 5.0 0.5642
Medium 3.2 to 5.0 0.1001 Heavy (Primary) 1.0 0.8723 Heavy (Thermal) 8.3 0.6666

The value of the system adjustment factor is determined using the equation below:



### K Q Q FY Oil T Collected CH

Oil T F CH −

− − 

### = − × × 1 4

4 

### Q Collected CH 4 = the amount of methane collected, and not emitted, during transportation and refining.
Often this amount is zero
Other terms defined above.
In the absence of any data regarding the volume of CH 4 collected, the value of system adjustment factor should be set to a default value of one.
Exploration and Drilling Losses
Total CH 4 emissions from the exploration and drilling sector will usually be small compared to the amount emitted by other sectors of the oil and gas industry. Consequently, a simple Tier 1 approach is perhaps most appropriate for use here.
The basic relation is shown below:
E D = N wells . F D where,
E D = total CH 4 emissions (Tg) from drilling and testing of oil and gas wells,
N wells = number of wells drilled and tested, and
F D = average amount of CH 4 emitted per well (Tg/well).
Tier 3 - Rigorous Source-Specific Evaluations Approach Rigorous source-specific evaluations will generally involve compiling the following types of information and may require significant interaction with industry and associated regulatory agencies:

• detailed inventories of the amount and types of process infrastructure (e.g., wells, minor field installations, and major production and processing facilities),

## E NERGY

1.128 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • production disposition analyses (e.g., oil and gas production; vented, flared and reinjected volumes of gas; and fuel gas consumption),

• accidental releases (i.e., well blow-outs and pipeline ruptures),

• typical design and operating practices and their impact on the overall level of emission control. The amount of emissions is then assessed by applying appropriate emission factors, empirical correlations, process simulation results, and field measurements to these data. Some examples of detailed emission inventories that have been developed in this manner are listed below:

• US Environmental Protection Agency (US EPA). Anthropogenic Methane Emissions in the United States. Estimates for 1990: Report to the Congress. October 1992 (US EPA, 1993).

• Picard, D.J., B.D. Ross, and D.W.H. Koon. A Detailed Inventory of CH 4 and VOC Emissions from Upstream Oil and Gas Operations in Alberta. Clearstone Engineering Ltd., for the Canadian Petroleum Association, March 1992 (Picard et al., 1992).

• UK Offshore Operators Association Ltd. (1992). Methane Emissions From Offshore Oil & Gas Exploration & Production Activities. Submitted to The Watt Committee on Energy, 1993.

• Norwegian Oil Industry Association - OLF. Report from OLF Environmental Programme - Phase 2. 1993.



### 1.8.7 Uncertainty Some of these studies do analyse uncertainties, but emissions estimates in general are very uncertain. The overall magnitude of the emissions estimates that will be obtained for some countries using the methods and assumptions outlined in this chapter is driven by two key studies:

• Rabchuk et al. (1991) report that emissions from gas production and transportation in the former USSR is very high, about 3 to 7 per cent of total gas production. Recent visits to this region indicate that system construction, maintenance, and operations may be consistent with high emissions rates (Craig, 1992). However, a better quantitative evaluation is needed to validate the current emissions estimates.

• Barns and Edmonds (1990) report emissions from venting and flaring by region. The emissions estimates for the OPEC countries are relatively high, and account for most of the emissions from this category. The safety concerns associated with venting, and the value of re-injecting gas into oil reservoirs to maintain reservoir pressures, would tend to render the high emissions estimates questionable. Improved data are needed to resolve this question. The adoption of emission factor estimates from US EPA (1992) for various regions also adds uncertainty to the overall estimates. US oil and gas production facilities and refineries are subject to emission control requirements. The US emission factors, particularly for refining, may under-estimate emissions in other regions. Nevertheless, this may not be a significant global uncertainty since, if the emission factors for oil production and oil refining were increased by a factor of 10 for the entire world, the estimate of total global emissions would only increase by about 1 to 6 Tg for 1988.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.129 T ABLE 1-60 USA AND C ANADA - E MISSION F ACTORS Emissions Type Emission factor kg/petajoule Source

Oil and Gas Production
Oil
Gas
Oil & Gas 290 - 4 670 of Oil Production
39 590 - 104 220 of Gas Production
2 870 - 13 920 of Oil & Gas Production US EPA (1992) US EPA (1992) US EPA (1992) Crude Oil Transportation and Refining Transportation Refining Storage Tanks 745 of Oil Tankered
90 - 1 400 of Oil Refined
20 - 260 of Oil Refined API (1987) US EPA (1992) US EPA (1992) Natural Gas Processing, Transport, and Distribution Gas Processing Gas Pipelines
Gas Distribution 59 660 - 116 610 of Gas Consumption

..

..

.. US EPA (1992)

..

..

..

T ABLE 1-61 E ASTERN E UROPE AND F ORMER USSR - E MISSION F ACTORS Emissions Type Emission factor kg/petajoule Source

Oil and Gas Production
Oil
Gas
Oil & Gas 290 - 4 670 of Oil Produced
218 000 - 567 600 of Gas Produced

6 300 - 29 700 of Gas Produced US EPA (1992) Rabchuk et al. (1991) Barns and Edmonds (1990) Crude Oil Transportation and Refining Transportation Refining Storage Tanks 745 of Oil Tankered
90 - 1 400 of Oil Refined
20 - 260 of Oil Refined API (1987) US EPA (1992) US EPA (1992) Natural Gas Processing, Transport, and Distribution Gas Processing Gas Pipelines
Gas Distribution 340 000 - 715 800 of Gas Consumption

..

..

.. Rabchuk et al. (1991)

..

..

..

## E NERGY

1.130 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 1-62 W ESTERN E UROPE - E MISSION F ACTORS Emissions Type Emission factor kg/petajoule Source

Oil and Gas Production
Oil
Gas

Oil & Gas 290 - 4 670 of Oil Produced
14 800 - 27 000 of Gas Produced

13 000-16 000 of Gas Produced
3 000-8 000 of Gas Produced US EPA (1992)
Schneider-Fresenius et al. (1989) Norwegian SPCA (1992) Norwegian O.I.A. OLF (1993) Crude Oil Transportation and Refining Transportation

Refining Storage Tanks 745 of Oil Tankered
2 500 of Oil Tankered
90 - 1 400 of Oil Refined
20 - 260 of Oil Refined API (1987) Norwegian SPCA (1992) US EPA (1992) US EPA (1992) Natural Gas Processing, Transport, and Distribution Gas Processing Gas Pipelines
Gas Distribution 58 000 - 111 000 of Gas Consumption

1 800 of Gas Processed

..

.. Schneider-Fresenius et al. (1989)

Norwegian SPCA (1992)

..

..

T ABLE 1-63 O THER O IL E XPORTING C OUNTRIES - E MISSION F ACTORS Emissions Type Emission factor kg/petajoule Source

Oil and Gas Production
Oil
Gas

Oil & Gas 290 - 4 670 of Oil Produced
39 590 - 96 000 of Gas Produced

739 470 - 1 019 220 of Gas Produced US EPA (1992) US EPA (1992) and Barns

and Edmonds (1990) Barns and Edmonds (1990) Crude Oil Transportation and Refining Transportation Refining Storage Tanks 745 of Oil Tankered
90 - 1 400 of Oil Refined
20 - 260 of Oil Refined API (1987) US EPA (1992) US EPA (1992) Natural Gas Processing, Transport, and Distribution Gas Processing Gas Pipelines
Gas Distribution 116 610 - 340 000 of Gas Consumption

..

..

.. US EPA (1992 and Rabchuk et al. (1991)

..

..

..

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.131 T ABLE 1-64 R EST OF THE W ORLD - M ETHANE E MISSION F ACTORS Emissions Type Emission factor kg/petajoule Source

Oil and Gas Production
Oil
Gas

Oil & Gas 290 - 4 670 of Oil Produced
39 590 - 96 000 of Gas Produced

170 000 - 209 000 of Gas Produced US EPA (1992) US EPA (1992) and Barns and Edmonds. (1990) Barns and Edmonds (1990) Crude Oil Transportation and Refining Transportation Refining Storage Tanks 745 of Oil Tankered
90 - 1 400 of Oil Refined
20 - 260 of Oil Refined API (1987) US EPA (1992) US EPA (1992) Natural Gas Processing, Transport, and Distribution Gas Processing Gas Pipelines
Gas Distribution 116 610 - 340 000 of Gas Consumption

..

..

.. US EPA (1992 and Rabchuk et al. (1991)

..

..

.. 

### 1.8.8 Fugitive Emissions of Other GHGs Methane is by far the most important greenhouse gas emitted on a fugitive basis from oil and gas activities. However, other GHGs are clearly emitted and should be included in a comprehensive national inventory. After methane, the most significant fugitive emissions from oil and gas activities are of non-methane volatile organic compounds (NMVOCs). Oil and gas are largely composed of organic compounds, and releases through evaporation or leakages are likely at all stages wherever the fuels or their products come into contact with the atmosphere. Fugitive emissions from refining, transport and distribution of oil products are a major component of national NMVOC emissions in many countries. The IPCC/OECD/IEA programme has not yet addressed the indirect GHGs (including NMVOCs) in detail. However, the Joint EMEP/CORINAIR Guidebook offers both a simplified and a more detailed approach to the estimation of ozone precursors and SO 2 . The relevant tables and accompanying text are summarised below. National experts interested in including the other fugitive emissions of GHGs from oil and natural gas systems should consult the existing literature which provides detailed emission factors and procedures for calculating emissions. Some key examples are:

• Default Emission Factors Handbook (EEATF, 1992);

• Proceedings of the TNO/EURASAP Workshop (TNO Inst. of Environmental Sciences, 1993);

• Atmospheric Emission Inventory Guidebook (Joint EMEP/CORINAIR, 1996);

• EMEP and CORINAIR Emission Factors and Species Profiles for Organic Compounds. (Veldt, 1991);

• US EPA's Compilation of Air Pollutant Emissions Factors (AP-42), 5th Edition 1995 (US EPA, 1995);

## E NERGY

1.132 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory (Stockton and Stelling, 1987).



### 1.8.9 Refineries

O VERVIEW A basic refinery converts crude petroleum into a variety of sub-products. Principal products of a refinery may include liquid fuels, coke, feedstocks and primary petrochemicals (like ethylene). This section covers basic refineries, not the synthesis of petrochemicals. Chemical production is included in Chapter 2, Industrial Processes, whether or not the actual production takes place at a refinery or in a separate plant. Storage and handling of intermediates and products may account for between 1 to 8 per cent of a country’s NMVOC emissions. There are also significant non-combustion emissions of SO 2 , NO x , and CO.
Refinery Operations Refinery operations include separation processes (distillation and gas processing), petroleum conversion processes (cracking, coking, catalytic reforming, alkylation, polymerisation), petroleum treating processes (desulphurisation, chemical sweetening, acid gas removal, deasphalting) and blending. Vacuum distillation, catalytic cracking, thermal cracking, sweetening, blowdown systems, sulphur recovery and asphalt blowing have been identified as being potentially significant sources of SO 2 and NMVOCs from these sources. Storage and handling of petroleum products will lead to NMVOC emissions.



### S IMPLE 

### M ETHODOLOGY FOR 

### O ZONE 

### P RECURSORS AND 

### S O 2 A simple estimation can be made on the basis of throughput and single emission factors. However in most cases more detailed information may be available and the more detailed approach outlined in the Joint EMEP/CORINAIR Guidebook (1996) under SNAP code 40100 or in the following section here should be adopted. This considers the actual processes taking place in the refinery and the throughput of crude and products. While emission rates will depend on the specific process and equipment in a refinery, its state of maintenance and the sulphur content of the crude oil, a very simple estimate can be made on the basis of the throughput of crude oil and simple emission factors alone. The default emission factors are shown in Table 1-65.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.133 T ABLE I-65 N ON -C OMBUSTION E MISSION F ACTORS FOR P ETROLEUM R EFINING . S IMPLE M ETHODOLOGY (KG/M 3 R EFINERY F EEDSTOCK E . G ., C RUDE O IL )

P OLLUTANT E MISSION F ACTOR S OURCES
SO 2 (a) 0.8 Vacuum tower, catalytic cracker, fluid coking, sulphur plant, SWS, incinerator, caustic regeneration, vents, off gases, others
NO x (a) 0.05 Catalytic cracking
CO (a) 0.08 Fluid catalytic cracker only
NMVOC (b) 0.53 Fugitive and process emissions

Source : (a) EMEP/CORINAIR (1996). (b) based on CPPI and Environment CANADA (1991).

NMVOC Emissions estimates vary widely

. The proposed default value is 0.53 kg/m 3 input

. Estimates range from 0.085 kg/m 3 from the best West European refinery to 10 kg/m 3 for a Russian refinery. In practice it may be possible to use a more detailed approach where some of the makeup of the refinery is known or where only some of the emission activities are known

. Some of these constituent parts are outlined below as an alternative to the above approach.



### D ETAILED 

### M ETHODOLOGY FOR 

### O ZONE 

### P RECURSORS AND 

### S O 2 In the detailed methodology, emissions are calculated separately from sub processes in the refinery

. The total emissions are the sum of the emissions from each individual sub process

. The calculations should be based on plant specific data.
**Fluid Catalytic Cracking (SNAP 40102)**
Emission factors for a petroleum refinery which uses a fluid catalytic cracking system are shown in Table I-66.

T ABLE I-66 N ON -C OMBUSTION E MISSION F ACTORS FOR R EFINERIES (F LUID C ATALYTIC C RACKING KG/M 3 O IL T REATED IN THE F LUID C ATALYTIC C RACKER )

P OLLUTANT E MISSION F ACTOR (V ALUE ) E MISSION F ACTOR (R ANGE )
SO 2 1.4 0.286-1.505
NO x 0.2 0.107-0.416
CO 39.2 NA
NMVOC 0.6 NA

Source: US EPA (1985a, 1995).

## E NERGY

1.134 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual No emission factors are currently available for cracking of coal to fluid products.
**Sulphur recovery plants (SNAP 40103)** Sulphur recovery is the conversion of hydrogen sulphide to elemental sulphur. Emission factors are based on the amount of elemental sulphur produced and are shown in Table I-67.

T ABLE I-67 N ON -C OMBUSTION E MISSION F ACTORS FOR R EFINERIES AND S ULPHUR R ECOVERY P LANTS . (KG/T ONNE S ULPHUR )

P OLLUTANT E MISSION F ACTOR
SO 2 139 Source : US EPA (1993b).

**Storage and handling (SNAP 40104)** Emissions of NMVOC result from evaporation from tanks during storage, displacement of vapour during volume changes, loading and unloading and spillages

. Storage may occur at a refinery or at separate locations

. Emissions depend on the type and state of the tanks

. Emission factors are suggested in Table I-68

. Where nothing is known the highest factor should be used

. The activity statistic is the crude oil throughput of the refineries.

T ABLE I-68 N ON -C OMBUSTION E MISSION F ACTORS FOR R EFINERIES (S TORAGE AND H ANDLING . G/KG O IL T HROUGHPUT )

C ONDITION E MISSION F ACTOR

• Majority of volatile products are stored in floating roof tanks with secondary seals 0.2

• Majority of volatile products are stored in floating roof tanks with only primary seals 0.7

• Majority of volatile products are stored in fixed roof tanks 4.9 Source : EMEP/CORINAIR (1996).

These emissions are intended to account for evaporative losses during storage and the displacement losses resulting from the loading and unloading of storage tanks. Emissions from this source may be higher in countries with a warm climate.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.135 

## 1.9 Further Work At the end of the Experts’ Meeting on GHG Emissions from Fuel Combustion (Abingdon, 29-30 March 1996), experts were asked to identify areas for future work on emissions from energy. The subsequent list was then prioritised into short/medium-term activities and longer-term activities.
Short to Medium term (1-3 years): 1. Perform sensitivity analysis to assess importance of emission factors for various
sectors. 2. Critically assess key emission factors found during sensitivity analysis, and key calorific values and activity data. 3. Enhance the EDGAR emission factors that feed into the Tier I methodology with information from US country studies and from other sources. 4. Critically compare IPCC emission factors and methodology with US EPA (1995) and CORINAIR.
5. Perform a literature search on emission factors:

• Mobile sources in developing countries

• N 2 O (all sources)

• Biomass (especially fuelwood)
6. Perform more research on emission factors for developing countries, including emission factors for biomass. 7. Enhance the section on fugitive emissions: coal mines (CH 4 ), oil & gas industry (CH 4 and NMVOC). 8. Analyse double counting with Industrial Processes section of IPCC Guidelines . Reevaluate the default carbon stored values provided in the Guidelines , including the fate of carbon stored in petroleum products. 9. Add a category for non-fuel energy related emissions, such as from geothermal energy, CH 4 from flooding to create reservoirs, etc. 10. Evaluate the adequacy of guidelines. 11. Compare the results obtained by using Tier 1 and Tier 2 calculations for the nonCO 2 gases. 12. Investigate the possibility of reporting inventories and background information on the Internet.
Long term: 1. Develop/update software to support computation and reporting of both the Tier I and Tier 2 approaches. 2. Enhance reliability of biomass consumption figures. 3. Perform statistical analysis of data reported, and validate results with globally measured concentrations of all direct greenhouse gases.

## E NERGY

1.136 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 1.10 References Abrahamson D. (1989), Relative Greenhouse Effect of Fossil Fuels and the Critical Contribution of Methane , presented to The Oil Heat Task Force. AGA (1989), Natural Gas Transmission and Distribution Methane Emissions , AGA, Engineering Technical Note, Arlington, VA, USA. Airuni, A.T. and V.E. Zeidenvarg (1992), The Role of Coal Production in the Global Contamination of the Biosphere by Methane , Russian Institute of Comprehensive Mineral Resources Exploitation, Moscow, Russia. Alexandersson, A. (1990), “The Swedish investigation - Exhaust emissions from ships”. Proc. EMEP Workshop on Emissions from Ships . Oslo, Norway, June 7-8, 1990. State Pollution Control Authority, Oslo, Norway. Alphatania (1989 ), Methane Leakage from Natural Gas Operations . The Alphatania Group. Ando, J. (1992), Global Environment and Energy Economics, Energy in Japan , 113. 36-46 (January). Andrias, A., D. Zafiris and Z. Samaras (1992), CORINAIR “Working group on emission factors for calculating 1990 emissions from road traffic”, Volume 2: COPERT Users Manual, September. Andrias, A., Z. Samaras and K.H. Zierock (1994), “The Estimation of the Emissions of ‘Other Mobile Sources and Machiner’ Supbparts ‘Off-Road Vehicles and Machines, Railways and Inland Waterways’ in the European Union”, EC Study Contract B4-3040/93/000803/B3, Berlin, Germany. API (American Petroleum Institute) (1987), Atmospheric Hydrocarbon Emissions from Marine Vessel Transfer Operations , API publication 2514A, Washington, DC, USA. Archer, Leonie J. (1993), Aircraft Emissions and the Environment, Oxford Institute for Energy Studies, EV 17, UK. Baas, J. (1991), “Study of literature on emission of nitrous oxide by road traffic” (in Dutch with English summary). TNO Report No. R91/322. IMW-TNO, Delft, The Netherlands, November 1991. Bakkum, A., and C. Veldt (1986), PHOXA: Statistical Data and Emission Factors . MT-TNO, Department of Environmental Technology, Apeldoorn, The Netherlands. Bakkum, A., H. Bartelds, J.A. Duiser, and C. Veldt (1987), Handbook of Emission Factors: Part 3 - Emissions from Stationary Sources . Ministry of Housing, Physical Planning, and Environment (VROM), Government Publishing Office, The Hague, The Netherlands, November. Ballantyne, V.F., P. Howes and L. Stephanson (1994), “Nitrous oxide emissions from light duty vehicles.” Society of Automotive Engineers Technical Paper Series 940304. Barns, D.W. and J.A. Edmonds (1990), An Evaluation of the Relationship between the Production and Use of Energy and Atmospheric Methane Emissions , TR047, US DOE/NBB0088P, US Department of Energy, Washington, DC, USA. Baughcum, S.L., T.G. Tritz, S.C. Henderson, and D.C. Pickett (1996), Scheduled Civil Aircraft Emission Inventories for 1992: Database Development and Analysis, NASA Contractor Report 4700, April 1996.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.137 BCTSRE (1992), Quantification of Methane Emissions from British Coal Mine Sources , prepared by British Coal Technical Services and Research Executive for the Working Group on Methane Emissions, The Watt Committee on Energy, UK. Berdowski, J., J. Olivier and C. Veldt (1993 a ), “Methane from fuel combustion and industrial processes”. In A.R. van Amstel, (ed .), Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control . RIVM Report No. 481507003, Bilthoven, The Netherlands. Berdowski, J., L. Beck, S. Piccot, J. Olivier and C. Veldt (1993 b ), “Working group report: methane emissions from fuel combustion and industrial sources”. In A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control

. RIVM Report No. 481507003, Bilthoven, The Netherlands. Bibler, C.J., et al. (1992), Assessment of the Potential for Economic Development and Utilisation of Coalbed Methane in Czechoslovakia . EPA/430/R-92/1008, US Environmental Protection Agency, Office of Air and Radiation, Washington, DC, USA. Bose, R. (1996), Energy Demand and Environmental Implications in Urban Transport Case of Delphi , Atmospheric Environment Vol. 30, No. 3, pp. 403-412. Boyer, C.M., et. al (1990), Methane Emissions from Coal Mining: Issues and Opportunities for Reduction , EPA-400/9-90/008, US Environmental Protection Agency, Office of Air and Radiation, Washington, DC, USA. Bremmes, P.K. (1990), “Calculations of exhaust gas emissions from sea transport: Methodology and results”. Proc. EMEP Workshop on Emissions from Ships . Oslo, Norway, June 7-8, 1990. State Pollution Control Authority, Oslo, Norway. Brocard, D., C. Lacaux and J.P. Lacaux (1996), Emissions from the Combustion of Biofuels in Western Africa, to be published in: Levine, J.S. (ed.) (1996), Biomass Burning and Global Change , MIT Press, Cambridge, Mass., USA. Brok, P.H.H. (1995), Personal communication 18.10.1995. Data developed in the framework of EDGAR/LULU, National Aerospace Laboratory (NLR), Amsterdam, the Netherlands. Canadian Petroleum Products Institute (CPPI) and Environment Canada (1991), Atmospheric Emissions from Canadian Petroleum Refineries and the Associated Gasoline Distribution System for 1988 . CPPI Report No. 91-7. Prepared by B.H Levelton and Associates Ltd. and RTM Engineering Ltd. CIAB (1992), Global Methane Emissions from the Coal Industry , prepared by the Coal Industry Advisory Board, Global Climate Committee/International Energy Agency, Paris, France. Cicerone, R.J. and R.S. Oremland (1988), "Biogeochemical aspects of atmospheric methane," Global Biogeochemical Cycles , Vol. 2, No. 4, Dec. 1988, pp. 299 - 327. CMRC (1990), Methane Emissions from Canadian Coal Operations: A Quantitative Estimate , prepared by B. Hollingshead, Coal Mining Research Company, CI 8936, Devon, Alberta, Canada. Craig, Bruce. (1992), Personal communication. US Environmental Protection Agency, Global Change Division, Washington, DC, USA.

## E NERGY

1.138 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Creedy, D.P. (1991), "An introduction to geological aspects of methane occurrence and control in British deep coal mines," Quarterly Journal of Engineering Geology , No. 24, pp. 209-220. Crutzen, P.J. (1987), "Role of the tropics in atmospheric chemistry," in Geophysiology of Amazonia , R. Dickenson, ed. John Wiley, New York, USA, pp. 107-132. Dasch, J.M. (1992), “Nitrous oxide emissions from vehicles”, Journal of Air and Waste Management Association, 42:63-67 (January). Delmas, R. (1993), “An overview of present knowledge on methane emission from biomass burning”. In A.R, van Amstel (ed.). Proceedings of an International IPCC Workshop: Methane and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control , 3-5 February 1993, Amersfoort, NL. RIVM Report No. 481507003, Bilthoven, The Netherlands, July. Delmas, R., J.P. Lacaux and D. Brocard (1995 ), Determination of Biomass Burning Emission Factors: Methods and Results , Env. Mon. and Assessment 38, 181-204. De Soete, G.G. (1989), “Updated evaluation of nitrous oxide emissions from industrial fossil fuel combustion”. Institut français du pétrole, Ref. 37-559. De Soete, G.G. (1993), “Nitrous oxide from combustion and industry: Chemistry, emissions and control”. In A.R. van Amstel, (ed .), Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control . RIVM Report No. 481507003, Bilthoven, The Netherlands. Ebert, C., D. Picard, P. Pope, and A. Roslund (1993), “Methane emissions from oil and natural gas systems: A methodology to estimate national emissions.” In A.R, van Amstel (ed.). Proceedings of an International IPCC Workshop: Methane and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control, 3-5 February 1993, Amersfoort, NL. RIVM Report No. 481507003, Bilthoven, The Netherlands, July. Eggleston, H.S. and G. McInnes (1987), Method for the Compilation of UK Air Pollutant Emission Inventories, ISBN-0-85624-493-7. Warren Spring Laboratory, Stevenage, UK. Eggleston, H.S. et al. (1992), CORINAIR “Working group on emission factors for calculating 1990 emissions from road traffic”, Volume 1: Methodology, Final Report , December. Joint EMEP/CORINAIR (1996), Atmospheric Emission Inventory Guidebook . Volume 1, 2. European Environment Agency Task Force (EEATF) (1992), Default Emission Factor Handbook. FAO (1990), FAO Yearbook , Forest products 1979-1990, FAO Forestry series no. 25. FAO Statistics series no. 103, Food and Agricultural Organization of the UN, Rome, Italy. Fritsche, U. (1989), Zusammenstellung von klimarelevanten Emissionsdaten für Energiesysteme in der BRD, Endbericht, Germany. Gardner et al. (1997), ANCAT/EC2 Aircraft Emission Inventories. Report produced by the European Civil Aviation Conference’s Group of Experts on the Abatement of Nuisances Caused by Air Transport (ANCAT) and the European Commission.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.139 GOB (Government of Bangladesh) (1987), Bangladesh Energy Planning Project (BEPP), Final Report, Vol. I-VII, Sir Halcrow and Partners, Motor Columbus Consulting Engineering Inc., Petronus Consultants SA in association with TSL and PSL. Grubb, M.J. (1989), On Coefficients for Determining Greenhouse Gas Emissions From Fossil Fuel Production and Consumption. Energy and Environmental Programme, Royal Institute of International Affairs, London, UK, April. Prepared for IEA/OECD Expert Seminar on Energy Technologies for Reducing Emissions of Greenhouse Gases , Paris, France. Hadler, C. (1990), “Investigation of exhaust gas emission from heavy fuel operated diesel engines on board ships”. Proc. EMEP Workshop on Emissions From Ships . Oslo, Norway, June 7-8, 1990. State Pollution Control Authority, Oslo, Norway. Hall, D.O. and Y.S. Mao (eds.) (1994a), Biomass Energy and Coal in Africa , Zed Books, London, UK. Hall, D.O., F. Rosillo-Calle and J. Woods (1994b ), Biomass Utilization in Households & Industry; Energy Use and Development , Chemosphere 29:5, pp. 1099-1119. Hao, W.M., S.C. Wofsy, M.B. McElroy, J.M. Beer and M.A. Toqan (1987), “Sources of atmospheric nitrous oxide from combustion”. Journal of Geophysical Research 92:3098-3104. Hargraves, A.J. (1990), "Coal seam gas and the atmosphere," in Greenhouse and Energy , North Ryde, NSW, Australia. Hitchcock D.R. and A.E. Wechsler (1972), Biological Cycling of Atmospheric Trace Gases, prepared for the National Aeronautics and Space Administration, Washington, DC, USA. Houghton, J. (1994), Global Warming, the Complete Briefing , Oxford, UK. IAEA (1993), Assessment of Data Bases on Energy Demand and Supply in Terms of their Adequacy for Use in Studies of Greenhouse Gas Emissions: Report of Advisory Group Meeting , IAEA, Vienna, 5-7 April, 1993. International Atomic Energy Agency, Vienna, Austria. ICAO (1994), Manual on the ICAO Statistics Programme , (Doc. 9069), International Civil Aviation Organization, Montreal, Canada. ICAO (1995), Engine Exhaust Emissions Databank . First Edition-1995. ICAO doc. 9646- AN/943. INGAA (1989 ), Global Warming and Methane Loss from Interstate Natural Gas Pipeline , (Interstate Natural Gas Association of America Rate and Policy Analysis Department, Washington, DC, USA. International Petroleum Encyclopedia (1990), Vol 23, PennWell Publishing Co., Tulsa, Oklahoma, USA. International Road Federation (1990), World Road Statistics 1986-1990 . Edition 1990, Washington, DC and Geneva, Switzerland, September. IPCC (1992), Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment . The Intergovernmental Panel on Climate Change (World Meteorological Organisation/United Nations Environment Programme). Cambridge University Press, UK.

## E NERGY

1.140 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual IPCC/OECD (1991), Proceedings of a Workshop on National GHG Emission Methods, Geneva, 3-7 December, 1991. Intergovernmental Panel on Climate Change, Working Group I, Bracknell, UK and Organisation for Economic Co-operation and Development, Environment Directorate, Paris, France. IPCC/OECD (1993), IPCC/OECD Workshop on National GHG Inventories: Transparency in Estimation and Reporting, 1 October, 1992, Bracknell, UK. IPCC/OECD Joint Programme on National GHG Inventories, Intergovernmental Panel on Climate Change and Organisation for Economic Co-operation and Development, Paris, France, April. JAERI (1988), Data provided through personal communication with Mr. Doug Hill, Operating Agent for the IEA Energy Technology Systems Analysis Project (ETSAP), Annex III, Japanese Atomic Energy Research Institute, Japan. Johansson, T.B., H. Kelly, A.K.N. Reddy and R.H. Williams (1992), Renewable Energy: Sources for Fuels and Electricity . Island Press, Washington, DC, USA. KfA (1993), personal communication from W. Katscher. Kirchgessner, D.A., S.D. Piccot and J.D. Winkler (1993), "Estimate of global methane emissions from coal mines," Chemosphere. Koyama, T. (1963), "Gaseous metabolism in lake sediment and paddy soils and the production of atmospheric methane and hydrogen ," Journal of Geophysical Research , 68 (13): 3971. Lacaux, J.P., H. Cachier and R. Delmas (1993), “Biomass burning in Africa: An overview of its impact on atmospheric chemistry.” In P.J. Crutzen and J.G. Goldammer (eds.) Fire in the Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires , J. Wiley & Sons Ltd. Lama, R.D. (1992), "Methane gas emissions from coal mining in Australia: Estimates and control strategies." In Proceedings of the IEA/OECD Conference on Coal, the Environment and Development: Technologies to Reduce Greenhouse Gas Emissions , IEA/OECD, Paris, France, pp. 255-266. Leach, G. and M. Gowen (1987), Household Energy Handbook; an Interim Guide and Reference Manual , World Bank Technical Paper no. 67, World Bank, Washington D.C., USA. Levine, J.S. (ed.) (1990), Global Biomass Burning: Atmospheric, Climatic and Biospheric Implications . The MIT Press, Cambridge, MA, USA. Linak, W.P., J.A. McSorley, R.E. Hall, J.V. Ryan, R.K. Srivastava, J.O.L. Wendt and J.B. Mereb (1990), “Nitrous oxide emissions from fossil fuel combustion”

. Journal of Geophysical Research 95:7533-7541. Lloyd’s Register (1995), Marine Exhaust Emissions Research Programme, Lloyd’s Register House, Croydon, England. Marland, G. and A. Pippin (1990), "United States emissions of carbon dioxide to the Earth's atmosphere by economic activity," Energy Systems and Policy , Volume 14, pp. 319-336. Marland, G., and R.M. Rotty (1984), “Carbon dioxide emissions from fossil fuels: A procedure for estimation and results for 1950-1982”, Tellus 36b:232-261. Melhus, O. (1990), “NO x emission factors from marine diesel engines”. Proc. EMEP Workshop on Emissions from Ships . Oslo, Norway, June 7-8, 1990. State Pollution Control Authority, Oslo, Norway.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.141 Montgomery, T.A., G.S. Samuelsen and L.J. Muzio (1989), “Continuous infrared analysis of N 2 O in combustion products”

. Journal of the American Chemical Society 39:721- 726. Norwegian SPCA (1992a), Emissions of Greenhouse Gases in Norway - 1989. National versus IPCC estimation method (Transparency study ). Rapport 92:29, State Pollution Control Authority, Norway. Norwegian SPCA (1992b), Letter on “Methane emissions from oil activities” from Audun Rosland, State Pollution Control Authority to Craig D. Ebert, ICF Incorporated. Norwegian Oil Industry Association - OLF (1993), Report from OLF Environmental Programme - Phase 2

. OECD (1991), Estimation of Greenhouse Gas Emissions and Sinks; Final Report from OECD Experts Meeting 18-21 February 1991. Prepared for the IPCC, Paris, France. OECD/IEA (1996), Coal Information , International Energy Agency, OECD, Paris, France. OECD/IEA (1991), Greenhouse Gas Emissions: The Energy Dimension . International Energy Agency, OECD, Paris, France. OECD/IEA (1993a), Energy Balances of OECD Countries, 1990-1991 . International Energy Agency, OECD, Paris, France. OECD/IEA (1993 b ), Energy Statistics and Balances of Non-OECD Countries: 1990-1991. International Energy Agency, OECD, Paris, France. OECD/IEA (1996a), Energy Balances of OECD Countries, 1993-1994 . International Energy Agency, OECD, Paris, France. OECD/IEA (1996b), Energy Statistics and Balances of Non-OECD Countries: 1993-1994. International Energy Agency, OECD, Paris, France. OECD/IEA (1996c), Energy Statistics of OECD Countries, 1993-1994 . International Energy Agency, OECD, Paris, France. Okken, P.A. (1989), “Impact of NO x and CO 2 constraints on the Netherlands energy system.” In: Proceedings of the 8th World Clean Air Congress , The Hague, The Netherlands, September. Okken, P.A. and T. Kram (1989), “CH 4 /CO - Emission from fossil fuels global warming potential”, paper presented at the IEA/ETSAP - Workshop , Paris, France, June 1989. ESC-WR-89-12, Petten, The Netherlands, Energy Study Centre, Netherlands Energy Research Foundation. Okken, P.A., and T. Kram (1990), “Calculation of actual CO 2 emissions from fossil fuels”

. Presented at ETSAP-IV Workshop Petten, the Netherlands, 9-12 April 1990 and IPCC Preparatory Workshop
, Paris
, France, 22-23 May 1990. Olivier, J.G.J. (1991), Inventory of Aircraft Emissions: a Review of Recent Literature . RIVM Report No. 736 301 008. RIVM, Bilthoven, The Netherlands, November 1991. Olivier, J.G.J. (1993), “Working group report: nitrous oxide missions from fuel combustion and industrial processes”. In A.R. van Amstel, (ed.), Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control . RIVM Report No. 481507003, Bilthoven, The Netherlands. Olivier, J.G.J (1995), Scenarios for Global Emissions from Air Traffic, National Institute of Public Health and Environment (RIVM), Report No. 773 002 003, Bilthoven, the Netherlands.

## E NERGY

1.142 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Olivier, J.G.J, A.F. Bouwman, C.W.M. van der Maas, J.J.M Berdowski, C. Veldt, J.P.J. Bloos, A.J.H. Visschedijk, P.Y.J. Zandveld and J.L. Haverlag (1995), Description of EDGARVersion 2.0; A set of global emission inventories of greenhouse gases and ozonedepleting substance for all anthropogenic and most natural sources on a per country basis and on 1 o x 1 o grid . National Institute of Public Health and Environment (RIVM), RIVM Report No. 771060 002, TNO-MEP Report No. R96/119. Bilthoven, the Netherlands. PG&E (1990), Unaccounted for Gas Project Summary Volume Pacific Gas & Electric Company Research & Development, San Ramon, CA, USA; GRI-90/0067.1. Picard, D.J., B.D. Ross and D.W.H. Koon (1992), A Detailed Inventory of CH 4 and VOC Emissions from Upstream Oil and Gas Operations in Alberta . Clearstone Engineering Ltd., for the Canadian Petroleum Association, March 1992. Pilcher, R.C., et al. (1991), Assessment of the Potential for Economic Development and Utilisation of Coalbed Methane in Poland . EPA/400/1-91/032, US Environmental Protection Agency, Washington, DC, USA. Polish Central Mining Institute (1990), Official Polish Methane Emissions Data for 1989, provided to Raven Ridge Resources, November 1990. Prigent, M. and G. De Soete (1989), Nitrous Oxide N 2 O in Engines Exhaust Gases - A First Appraisal of Catalyst Impact. SAE Paper No. 890492, SAE International, Warrendale, PA, USA. Rabchuk, V.I, N.I. Ilkevich and Y.D. Kononov (1991), A Study of Methane Leakage in the Soviet Natural Gas Supply System , prepared for the Battelle Pacific Northwest Laboratory, Siberian Energy Institute, Irktsk, USSR. Radian Corporation (1990), Emissions and Cost Estimates for Globally Significant Anthropogenic Combustion Sources of NO x , N 2 O, CH 4 , CO, and CO 2 . Prepared for the Office of Research and Development, US Environmental Protection Agency, Washington, D.C., USA. Radian Corporation (1992) Venting and Flaring Emissions from Production, Processing, and Storage in the US Natural Gas Industry , Updated Draft Report prepared for the US EPA and the Gas Research Institute. Rentz, O., H.D, Haasis, T. Morgensterm, F. Pewrello-Aracena, J. Remmers and G. Schons (1988), Optimal Control Strategies for Reducing Emissions from Energy Conversion and Energy Use . Institute for Industrial Production, Karlsruhe, Germany, March. Rentz, O., R. Dorn, R. Holschumacher and C. Padberg (1992), Application of advanced SO 2 and NO x emission control technologies at stationary combustion installations in OECD countries , Institute for Industrial production, University of Karlsruhe, Germany. Riveros, H., J. Tejeda, L. Ortiz, A. Julián-Sánchez, H. Riveros-Rosas (1995), Hydrocarbons and Carbon Monoxide in the Atmosphere of Mexico City , J. Air & Waste Manage Assoc. 45: 973-980. Ryan, P. and K. Openshaw (1991), “Assessment of biomass energy resources: A discussion of its need and methodology”, World Bank Energy Series Paper No. 48

. Washington, DC, USA. Schneider-Fresenius, W., R.A. Hintz, U. Hoffmann-Meienbrock, W. Klopffer and J. Wittekind (1989) Determination of Methane Emission into the Atmosphere due to Losses in the Natural Gas Supply System of the Federal Republic of Germany - Contribution of Methane to the Global Greenhouse Effect . Battelle-Institut, Frankfurt, Germany.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.143 Seiler, W. (1984), "Contribution of biological processes to the global budget of CH 4 in the atmosphere." In: Current Perspectives in Microbial Ecology , American Society for Microbiology, Washington, DC, USA. Seltzer, H. and W. Zittel (1990), Emissions of Methane Gas Affecting the Climate: An Investigation of Global Methane Emissions from the Use of Fossil Fuels, Waste Incineration, Agriculture, and the Earth , LBST-Report No. 10/90, Ottobrunn, Germany. Smith, I.M. and L.L. Sloss (1992), Methane Emissions from Coal: IEA Perspectives . IEAPER/04, London, UK, November 1992. Smith, K.R. and J. Ramakrishna (1990), Biomass Fuels and Health , in: Lamptey et al. (1990), Bioenergy , Wiley Eastern Ltd, IDRC, Ottawa, Canada. Smith, K.R., M.A.K. Khalil, R.A. Rasmussen, S.A. Thornloe, F. Manegdeg and M. Apte (1993), Greenhouse Gas Emissions from Biomass and Fossil Fuel Stoves in Developing Countries: a Manila pilot study , Chemosphere 26:1-4, pp. 479-505. Southern California Gas Company (SOCAL) (1992), Unaccounted for Gas Project Summary Volume SOCAL Research & Development, Los Angeles, CA, USA. Statens forurensningstilsyn (1990), Klimagass Regnskap for Norge . Oslo, Norway. Stockton, M.B. and J. Stelling (1987), Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory . EPA-600/7-87-015. Office of Research and Development, US EPA, Washington, DC, USA. Summers, G. (1993), Personal communication on behalf of the Coal Industry Advisory Board, Global Climate Committee, 22nd July. Susuki, M., M. Nakazawa, T. Hidaka and M. Kaneko (1992): “Study on N 2 O emission from motor vehicles” . Proc. of the 33 rd Annual meeting of the Japan Society of Air Pollution , 347, Osaka, Japan, 1992. TNO (1993), Proceedings of the TNO/EUROSAP Workshop , Delft, June 1993. TNO, Institute of Environmental Sciences, Petten, The Netherlands. UK Offshore Operators Association Ltd (1993), Methane Emissions From Offshore Oil & Gas Exploration & Production Activities . Submitted to The Watt Committee on Energy. UN (1996), 1994 Energy Statistics Yearbook . United Nations, New York, USA. UN ECE (1989), Annual Bulletin of Transport Statistics for Europe: Volume XXXIX . United Nations, New York, USA. US CSP (1996), Greenhouse Gas Emission Inventories. Interim results from the US Country Studies Program . Environmental Science and Technology Library 9. Kluwer Acad. Publishers, UK. US DOE/EIA (1992), Analysis of the Relationship Between the Heat and Carbon Content of US Coals . Energy Information Administration, Department of Energy, USA, September. US EPA (1985a), “Compilation of Air Pollutant Emission Factors ”, Vol. I, Stationary Point and Area Sources, AP-42, 4 th Edition 1985; Suppl. A/1986, Suppl. B/1988, Suppl. C/1990. Environmental Protection Agency, USA. US EPA (1985b), “Compilation of Air Pollutant Emission Factors” : Highway Mobile Sources . AP-42, Fourth Edition, Ann Arbor, Michigan, USA.

## E NERGY

1.144 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual US EPA (1992), Procedures for Emission Inventory Preparation , Vol. IV: Mobile Sources, EPA-450/4-81-026d. US EPA (1993a). Anthropogenic Methane Emissions in the United States: Estimates for 1990, Report to the US Congress , US Environmental Protection Agency, Office of Air and Radiation, Washington, DC, USA. US EPA (1993b), “Compilation of Air Pollutant Emission Factors” , Vol. I, Stationary Point and Area sources, AP-42, Supplement F. US Environmental Protection Agency, USA. US EPA (1993c), Global Anthropogenic Methane Emissions: Estimates for 1990, Report to the US Congress , , US Environmental Protection Agency, Office of Policy, Planning and EvaluationWashington, DC, USA. US EPA (1994a), User's Guide to Mobile5 (Mobile Source Emission Factor Model , EPA-AAAQAB-94-01, US Environmental Protection Agency, Office of Mobile Sources, , Ann Arbor, MI, USA. US EPA (1994b), International Anthropogenic Methane Emissions, Estimates for 1990 (Report to Congress). EPA 230-R-93-010, , US Environmental Protection Agency, Office of Policy Planning and EvaluationWashington, DC, USA. US EPA (1995), Compilation of Air Pollutant Emission Factors . Vol. I: Stationary Point and Area Sources, 5th Edition, AP-42; US Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, USA. US GS (1993), personal communication. US Office of Environment and Energy (1991), FAA Aircraft Emission Database User’s Manual. Veldt, C. (1991), Development of EMEP and CORINAIR Emission Factors and Species Profiles for emissions of Organic C ompounds. IMET-TNO Report 91-299. Veldt, C. and J.J.M. Berdowski (1995), GEIA-note on the combustion of biomass fuels (Emission factors for CO, CH 4 and NMVOC), TNO-MW-R94/218, Delft, the Netherlands. Vernon, J.L. (1990), “Coal and Environmental Quality Throughout the 1990s and Sulphur Emissions Worldwide”, Energy Business Review , 1(2), pp. 35-60 (Oct-Dec 1990). Venon, J.L. and T. Jones (1993), Sulphur and Coal , IEA Coal Research, IEACR/57, London, UK. Weaver, C.S. (1988), Feasibility and Cost-Effectiveness of Controlling Emissions from Diesel Engines Used in Rail, Marine, Construction, Farm, and Other Mobile Off-Highway Equipment . Report under EPA Contract No. 68-01-7288, Radian Corporation, Sacramento, CA, USA. Wiesen, P., J. Kleffmann, R. Kortenbach and K.H. Becker (1994 ), Nitrous Oxide and Methane Emissions from Aero Engines , Geophys. Res. Lett. 21:18 2027-2030. Williams, A. and C. Mitchell (1992), Methane Emissions from Coal Mining , Department of Fuel and Energy, The University of Leeds, Leeds, UK. Wuebbles, D.J., S.L. Baughcum, M. Metwally and R.K. Seals Jr. (1993) Emissions Scenario Development , Emissions scenarios committee report in: Stolarski, R.S. and H.L. Wesoky (1993), The Atmospheric Effects of Stratospheric Aircraft : a third program report. NASA, Reference Publication RP-1313

.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 1.145 Zeedijk, H. (1986), “Emissions by Combustion of Solid Fuels in Domestic Stoves”. Proc. 7 th World Clean Air Congress , Sydney, Australia, H.F. Hartmann (ed.)., Vol. IV, pp. 78-85. Zimmermeyer, G. (1989), Methane Emissions and Hard Coal Mining , Glückaufhaus, Essen, Germany, Gesamtverband des deutschen Steinkohlenbergbaus, personal communication.Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 2 

# I NDUSTRIAL 

# P ROCESSES

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.1 

# 2. INDUSTRIAL PROCESSES

2.1 Overview Greenhouse gas emissions are produced from a variety of industrial activities which are not related to energy. The main emission sources are industrial production processes which chemically or physically transform materials. During these processes, many different greenhouse gases, including CO 2 , CH 4 , N 2 O, and PFCs, can be released. Cement production is a notable example of an industrial process that releases a significant amount of CO 2 . Different halocarbons (and SF 6 ) are also consumed in industrial processes or used as alternatives to ozone depleting substances (ODS) in various applications. Table 2-1 gives an overview of potential industrial emission sources of GHGs and ozone and aerosol precursors (NO x , NMVOCs, CO and SO 2 ). In some instances industrial process emissions are produced in combination with fuel combustion emissions and it may be difficult to decide whether a particular emission should be reported within the energy or industrial processes sector. Where the main purpose of the fuel combustion is to use the heat released, the resulting emissions are included as energy emissions, not industrial process emissions. There are, however, some chemical processes or stages of processes, which oxidise carbon as a feedstock and are exothermic. The reduction of iron in a blast furnace through the combustion of coke is an example. Invariably the heat released is used within the processes or for other energy needs of the producer. However, in this case, since the primary purpose of coke oxidisation is to produce pig iron, the emissions are considered to be industrial. In some cases not all fuel feedstock delivered to petrochemical plants is used for manufacture of other products. Some feedstock may in fact be used for energy purposes in the sense that it is combusted for the heat released. This may be included as energy in the national energy balance, but not necessarily. The separation of the feedstock and energy uses and the identification of any fuel by-products from the processes is a notoriously difficult area of energy statistics. Where a country has difficulty in distinguishing whether an emission is energy- or industrial-based, compilers of industrial-process emissions statistics should liaise closely with their energy counterparts and compare their basic data for fuel use in the industrial processes to avoid double counting. All emissions, including evaporative emissions, which occur in energy transformation activities are discussed in the Energy Chapter. Emissions from petrochemical processes are, however, covered in this chapter. Emissions of NMVOCs from use of solvents are discussed in the chapter “Solvents and other product use” even if they originate from an industrial process.
CO 2 from use of biological carbon as feedstock and fermentation processes should not be reported under “Industrial Processes” or any other sector of the IPCC Guidelines if they originate from sources of carbon that are from a closed cycle. Non-combustion industrial processes resulting in N 2 O emissions are recognised as important anthropogenic contributors to global N 2 O emissions. It is estimated that this source category represents 10 to 50 per cent of anthropogenic N 2 O emissions and 3 to 20 per cent of all global emissions of N 2 O (IPCC, 1992). The main sources of industrial anthropogenic N 2 O emissions are adipic acid and nitric acid production.

## I NDUSTRIAL 

## P ROCESSES

2.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF 6 ) are used as alternatives to ozone depleting substances being phased out under the Montreal Protocol. Current and expected applications of these compounds include refrigeration and air-conditioning, fire extinguishing, aerosols, solvents, and foam production. These chemicals are either emitted instantaneously or slowly being leaked out over time. Many of these compounds have high global warming potentials (GWPs) and long atmospheric lifetimes. Consumption of HFCs, and to some extent PFCs and SF 6
, is expected to grow substantially in the next decades due to their importance as substitutes for ozone depleting substances. HFCs, PFCs and SF 6 are also emitted from industrial processes, such as production of aluminium, magnesium and halocarbons (e.g., HCFC-22). In some countries PFC emissions from industrial processes could be an important contributor to national GHG emissions, due to high GWPs. Much of the information on the greenhouse gases contained within this chapter is based on four key documents: ” Anthropogenic Emissions of CO 2 , CH 4 and N 2 O in Norway ”, (Rypdal, 1993), “ Greenhouse gas emissions in Norway”, Norwegian Pollution Control Authority (1994), “ Workbook for Industrial Emissions and Solvent Use ”, National Greenhouse Gas Inventory Committee, Australia (Workbook, Australia, 1995), and the previous version of the Industrial Processes Chapter in the IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 1995). In addition, several experts, within and outside of the Industrial Processes Expert Group, have contributed to this chapter.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.3 T ABLE 2-1 POTENTIAL E MISSIONS FROM INDUSTRIAL PROCESSES . Process Greenhouse Gases Ozone and Aerosol Precursors

CO 2 CH 4 N 2 O PFC SF 6 HFC NO x NMVOC CO SO 2 Mineral Products Cement production x x Lime production x x
Limestone use x Soda Ash prod. and use x Asphalt roofing x x Road paving xx x x
Other x x x x x x Chemical industry

Ammonia x x x x x
Nitric acid x x Adipic acid x x x x

Urea x

Carbides x x x x x Caprolactam x

Petrochemicals x x x x x
Metal Production Iron, steel and ferroalloys x x x x x x
Aluminium x x x x x x x x Magnesium x x x x x x
Other metals x x x x x x x
Other Pulp and paper xx x x Food and drink production x
Production of halocarbons x x x

Use of halocarbons and SF 6 xxx
Other sources x x x x x x x x x x The table does not necessarily cover all potential GHGs or industrial sources. A cross in the table does not imply that the emission estimations methodology is available in this report or that the emission of a given source and gas is significant.

## I NDUSTRIAL 

## P ROCESSES

2.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 2 . 2 G e n e r a l Met h od ol ogy

2.2.1 Overview The general methodology employed to estimate emissions associated with each industrial process involves the product of activity level data, e.g., amount of material produced or consumed, and an associated emission factor per unit of consumption/production according to the following method:

TOTAL ij = A j x EF ij
where:
TOTAL ij = process emission (tonnes) of gas i from industrial sector j
A

j = amount of activity or production of process material in industrial sector j (tonnes/yr)
EF ij = emission factor associated with gas i per unit of activity in industrial sector j (tonne/tonne) This general method represents the fundamental relationship to evaluate industrial process emissions. It should be noted, however, that a number of mathematical steps may be involved in reducing more complex mathematical formulae to the simplified form of the formula above. In cases where mathematical transformations are involved, justifications are presented. Often process emissions from a certain industrial sector are caused by emissions from a few plants in each country. Therefore, measurement data are often available. Emission estimates should be based on such data if they exist instead of a more generalised methodology. Even if measurements are not available, calculations should preferably be based on plant-specific data.



### 2.2.2 Approaches to Avoid Double Counting of C O 2 The IPCC Methodology for national GHG inventories requires an intentional double reporting of NMVOCs, methane and carbon monoxide, firstly in their individual inventories, and as CO 2 equivalent in the national CO 2 inventory. Whether an explicit addition to the CO 2 inventory is required depends on how the national CO 2 inventory has been calculated. Guidance on this point is contained under “Double Counting of Emissions” (See Overview) contained in each volume of the IPCC Guidelines.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.5 

## 2.3 Cement Production

2.3.1 Overview Carbon dioxide emitted during the cement production process represents the most important source of non-energy industrial process of global carbon dioxide emissions. Cement production accounts for about 2.4 per cent of total global industrial and energy CO 2 emissions (Marland et al., 1989). Carbon dioxide is produced during the production of clinker and intermediate product from which cement is made. High temperatures in cement kilns chemically change raw materials into cement clinker (greyish-black pellets about the size of 12 mm-diameter marbles). Specifically, calcium carbonate (CaCO 3 ) from limestone, chalk or other calcium-rich materials is heated, forming lime (calcium oxide or CaO) and carbon dioxide in a process called calcination or calcining :

CaCO 3 + Heat → CaO + CO 2

This lime combines with silica-containing materials, provided to the kiln as clays or shales, to form dicalcium or tricalcium silicates, two of the four major compounds in cement clinker (Griffin, 1987). The clinker is then removed from the kiln, cooled, and pulverised into an extremely fine grey powder. During this operation a small amount of gypsum is added to regulate the setting time of the cement. The finished product is called "Portland" cement 1

. It should be noted that when poured concrete is curing, some CO 2 is reabsorbed by the concrete from the atmosphere. This CO 2 reabsorption is, however, believed to be only a small fraction of the CO 2 emission resulting from cement production and is therefore usually ignored in emission calculations. Most of the cement currently produced in the world is of Portland cement type, which contains 60 per cent to 67 per cent lime by weight. Other speciality cements are lower in lime, but are typically used in small quantities. Research is underway on cement formulations that have similar structural properties to Portland cement, but require less lime (Tresouthick and Mishulovich, 1990). Carbon dioxide emissions from cement production are essentially directly proportional to lime content, so production of cements lower in lime yield less CO 2 . Because CO 2 is emitted during clinker production (rather than cement production itself), emission estimates should be based on the lime content and production of clinker

. Estimating emissions based on the lime content and production of finished cement ignores the consideration that some domestic cement may be made from imported clinker, or that some finished cement may use additional lime that is not accounted for in the cement calculations. Clinker statistics, however, may not be readily available in some countries. If this is the case, cement statistics can be used. The differences between the lime content and production of clinker and cement, in most countries , are not significant enough to affect the emission estimates.

1 In some countries, e.g., Japan, an effort has been made to substitute blast furnace slag for lime. If this non-Portland type forms a significant quantity of cement production, it can reduce the average emission factor.

## I NDUSTRIAL 

## P ROCESSES

2.6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.3.2 Emission Estimation Methodology for CO 2 Estimation of CO 2 emissions from cement production is accomplished by applying an emission factor, in tonnes of CO 2 released per tonne of clinker produced, to the annual clinker output. 2 The emission factor (EF) is the product of the fraction of lime used in the cement clinker and a constant reflecting the mass of CO 2 released per unit lime.

EF clinker = Fraction CaO x (44.01 g/mole CO 2 / 56.08 g/mole CaO)

or EF clinker = Fraction CaO x 0.785

There are two methods for calculating this emission factor. The first is to assume an average CaO fraction in clinker. Since clinker is mixed with gypsum, which contains no lime per unit, to make cement, clinker has a higher lime percentage than finished cement. The average clinker lime percentage has been estimated to be 64.6 per cent. 3 This number when multiplied by the molecular weight ratio of CO 2 /CaO (0.785) gives a clinker emission factor of 0.5071 tonnes of CO 2 /tonne of clinker produced.

EF clinker = 0.646 x 0.785 = 0.5071

A second method is to assemble country or regional data on clinker production by type and clinker CaO content by type, then calculate a weighted average for cement lime content in the country. In most countries, the difference in the results of these two methods is likely to be small; any error in the lime content assumption is likely to be smaller than the uncertainty in clinker and cement production figures (Griffin, 1987). If information on clinker production is not readily available, an emission factor in tonnes of CO 2 released per tonne of cement produced can be applied to annual cement production instead. This approach has been followed by Marland et al. (1989), who took the average CaO content of cement to be 63.5 per cent, yielding an emission factor of 0.4985 CO 2 /cement (0.136 tonne CO 2 as C/tonne cement).

EF cement = 0.635 x 0.785 = 0.4985

Additional research indicates that "masonry cement", as opposed to "Portland cement", requires additional lime, over and above the lime used in its clinker. The following formula can be used to account for this activity:

2 Note that the estimation of CO 2 from energy use during cement production is explained in the energy chapter; these emissions should be reported under Energy: Fuel Combustion activities.

3 Gregg Marland, ORNL, personal communication.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.7 a x (All Cement Production) x ((1-1/(1+b)) x c) x 0.785

= tonnes CO 2 from CaO added to masonry cement

where: a = fraction of all cement produced that is masonry cement (e.g., 0.1- 0.2) b = fraction of weight added to masonry cement by non-plasticiser additives such as lime, slag, and shale (e.g., 0.03, 0.05) c = fraction of weight of non-plasticiser additives that is lime (e.g., 0.6- 0.8)
a x (All Cement Production) = masonry cement production ((1-1/(1+b)) x c) = fraction of lime in masonry cement not attributable to clinker ((1-1/(1+b)) x c) x 0.785 = an emission factor of CO 2 from masonry cement additives

The recommended method for estimating CO 2 emissions from cement production is to multiply the most reliable figures available for tonnes of clinker produced by an emission factor of 0.5071 tonne CO 2 /tonne clinker. Alternatively, cement production can be multiplied by an emission factor of 0.4985 tonne CO 2 /tonne cement

. International cement production data are available from the United Nations (1988) and from the U.S. Bureau of Mines (1988). In some countries, national data may be available from appropriate government ministries. There is substantial overlap between the U.S. Bureau of Mines and the UN data sets, but the former is more complete. Published information is also available from the European Cement Association (CEMBUREAU, 1990).



### 2.3.3 Emissions Estimation Methodology for SO 2 EMEP/CORINAIR has classified cement production as both an industrial combustion and an industrial process (SNAP codes 30311 and 40612, respectively). However, no description of emission factors for the non-combustion emissions are presented. A default methodology is, therefore, presented below.
SO 2 emissions will originate from sulphur in the fuel and in the clay raw material. Most (about 70-95 per cent) of the SO 2 generated in the process will be absorbed in the produced alkaline clinker (U.S. EPA 1995). The fuel emissions are counted as energy emissions while the SO 2 from the clay should be counted as non-combustion emissions. A non-combustion emission factor of 0.3 kg SO 2 /tonne cement has been calculated from measurements in Norwegian plants (Rypdal 1995). This factor may vary from plant to plant as the sulphur content of raw materials and degree of absorption will vary. If no information on sulphur content and degree of absorption is available and there are no measurement data, a factor of 0.3 kg SO 2 /tonne cement is suggested.

## I NDUSTRIAL 

## P ROCESSES

2.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 2.4 Lime Production

2.4.1 Overview Calcined limestone (or quicklime) is formed by heating limestone to decompose the carbonates. This is usually done at high temperatures in a rotary kiln and the process releases carbon dioxide. Depending on the product requirements (e.g., metallurgy, pulp and paper, construction materials, effluent treatment, water softening, pH control and soil stabilisation), primarily high calcium limestone (calcite) is processed in this manner from the quarried limestone to produce quicklime in accordance with the following reaction:

CaCO 3 (limestone) + heat → CaO (quicklime) + CO 2

Hydrated (slaked) lime is also produced, with additional hydration operations, at some facilities. Dolomitic limestone or magnesite may also be processed at high temperature to obtain dolomitic lime (and release CO 2 ) in accordance with the following reaction:

CaCO 3 . Mg CO 3 (dolomite) + heat → CaO

. MgO (dolomitic lime) + 2CO 2

The production of lime involves a series of steps comparable to those used in the production of Portland cement clinker. These include quarrying the raw materials, crushing and sizing, calcining (i.e., high temperature heat processing ~ 1100° C) the raw materials to produce lime, hydrating the lime to calcium hydroxide followed by miscellaneous transfer, storage and handling operations.



### 2 . 4 . 2 E m i s s i o n s E s t i m a t i o n M e t h o d o l o g y f o r C O 2 The mass of CO 2 produced per unit of lime manufactured may be estimated from the molecular weights and the lime content of products. On the basis of the calcination reaction, one mole of carbon dioxide is formed for each mole of quicklime produced from burning calcium carbonate. This was used to derive an emission factor based on the amount of quicklime produced (ORTECH, 1991), assuming complete dissociation of the carbonate rock and no reabsorption of CO 2 by lime in the kiln. In instances where dolomitic limestone is calcined, the emission factor was derived based on the lime: magnesia product (ORTECH, 1991). The emission factors are tabulated in Table 2-2. For high calcium lime, CO 2 emissions are estimated according to:

EF = 44.01 g/mole CO 2 /56.08 g/mole CaO = 785 kg CO 2 /tonne high calcium lime

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.9 For dolomitic lime, CO 2 emissions are estimated according to:
EF = 2 x 44 .01 g/mole CO 2 /96.39 g/mole CaO • MgO = 913 kg CO 2 /tonne dolomitic lime

The coefficient 2 relates to the stoichiometric ratio of CO 2 to CaO . MgO in the calcination process. Both formulas assume pure lime, but in some cases the purity may range from 85 to 95 per cent (Workbook, Australia, 1995). In these cases, the formulas should be adjusted according to the lime purity.

T ABLE 2-2 S UMMARY OF E MISSION F ACTORS

Process Component Emission Factor Reference
Lime Kiln-Calcite Feed CO 2 0.79 tonnes CO 2 /tonnes quicklime produced ORTECH, 1991

Lime Kiln-Dolomite Feed CO 2 0.91 tonnes CO 2 /tonnes dolomitic lime ORTECH, 1991

The consumption of lime may in cases result in the removal of CO 2 from the atmosphere. The use of hydrated lime (for water softening) for example, results in CO 2 reacting with lime to form calcium carbonate. Lime is also used as a CO 2 absorbent for atmospheric control in the storage of fruit. At this time, data is not available to reliably estimate the extent of atmospheric CO 2 removal from the use of lime.



### 2.4.3 Emissions Estimation Methodology for SO 2 Details for deriving emissions for this sector are not yet available. SO 2 should be considered. The non-combustion emissions will depend on the sulphur content and mineralogical form (pyrite or gypsum) of the stone feed, the quality of the lime produced and the type of kiln (U.S. EPA 1995). In this process, SO 2 emissions from combustion will usually exceed the non-combustion emissions (U.S. EPA 1995). Until more information becomes available, it is recommended that only emissions from fuel combustion (Energy Chapter) are considered.



## 2.5 Limestone and Dolomite Use

2.5.1 Overview Limestone (CaCO 3 ) and dolomite (CaCO 3 . MgCO 3 ) are basic raw materials having commercial applications in a number of industries including metallurgy (e.g., iron and steel), glass manufacture, agriculture, construction and environmental pollution control. In industrial applications involving the heating of limestone or dolomite at high temperatures, CO 2 is generated.

## I NDUSTRIAL 

## P ROCESSES

2.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual CO 2 from liming of soils should be reported in the Land-use Change and Forestry Chapter. Limestone and dolomite used in cement and lime production should be reported under that industry sector. Under this section are inventoried all other uses of limestone and dolomite which produce CO 2 emissions.



### 2.5.2 Emissions Estimation Methodology for CO 2 The mass of CO 2 emitted from the use of limestone and dolomite may be estimated from a consideration of consumption, purity of the raw materials and the stoichiometry of the chemical processes. Emission factor, EF ls , for limestone use:

EF ls = f x [44.01 g/mole CO 2 ] / [(100.09 g/mole CaCO 3 )] = (440 x f ) kg CO 2 / tonne limestone

where: f is the fractional purity of limestone in CaCO 3 per tonne of total raw material weight (if unknown, the default factor for f is equal to 1). Emission factor, EF ls , for dolomite use:

Ef

d = f x [2 x 44.01 g/mole CO 2 ] / [(184.41 g/mole CaCO 3  MgCO 3 )] = (477 x f) kg CO 2 / tonne dolomite

The total CO 2 emission from limestone and dolomite use in Gg/yr calculated as:

Total Id = {(A ls x EF ls ) + (A d x EF d ) }/10 6 = {(440 x f x A ls ) + (477 x f x A d )}/10 6

where:
Total ld is the process emission of CO 2 from limestone and dolomite use (Gg/yr)
A ls is the consumption of limestone (tonnes/yr). Consumption is assumed to equal material mined (or dredged) plus material imported minus material exported. The consumption entering this calculation excludes limestone used for producing cement and lime, agriculture and processes where CO 2 is not generated.
A d is the consumption of dolomite (tonnes/yr). Consumption is assumed to equal material mined plus material imported minus material exported. The consumption entering this calculation excludes limestone used for producing lime and magnesium, and processes where CO 2 is not generated.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.11 

## 2.6 Soda Ash Production and Use

2.6.1 Overview Soda ash (sodium carbonate, Na 2 CO 3 ) is a white crystalline solid that is used as a raw material in a large number of industries including glass manufacture, soap and detergents, pulp and paper production and water treatment. Carbon dioxide is emitted from the use of soda ash, and may be emitted during production, depending on the industrial process used to manufacture soda ash.
Emissions of CO 2 from the production of soda ash vary substantially with the manufacturing process. Four different processes may be used commercially to produce soda ash. Three of these processes, monohydrate, sesquicarbonate and direct carbonation, are referred to as natural processes. The fourth, the Solvay process, is classified as a synthetic process.About 25 per cent of the world production is produced from natural sodium carbonatebearing deposits referred to as natural processes. During the production process, trona (the principal ore from which natural soda ash is made) is calcined in a rotary kiln and chemically transformed into a crude soda ash. Carbon dioxide and water are generated as by-products of this process. Carbon dioxide emissions can be estimated based on the following chemical reaction:

Na 2 CO 3 x NaHCO 3 x 2H 2 O → 3Na 2 CO 3 + 5H 2 O + CO 2 Trona Soda Ash

According to this reaction, it takes 10.27 tonnes of trona to produce 1 tonne of carbon dioxide. Hence, for natural soda ash production, emissions of carbon dioxide can be calculated by the following formula:

EF = 0.097 tonne CO 2 / tonne of Trona

About 75 per cent of the world production is synthetic ash made from sodium chloride. In the Solvay process, sodium chloride brine, limestone, coke and ammonia are the raw materials in a series of reactions leading to the production of soda ash. Ammonia, however, is recycled and only a small amount is lost. The series of reactions involved in the Solvay process may be presented as follows:

CaCO 3 + heat → CaO + CO 2 CaO + H 2 O → Ca(OH) 2 NaCl + H 2 O + NH 3 + CO 2 → NaHCO 3 + NH 4 Cl

2NaHCO 3 + heat → Na 2 CO 3 + CO 2 + H 2 O Ca(OH) 2 + 2NH 4 Cl → CaCl 2 + 2NH 3 + 2H 2 O

## I NDUSTRIAL 

## P ROCESSES

2.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The net overall reaction may be summarised as:

CaCO 3 + 2NaCl → Na 2 CO 3 + CaCl 2

From the series of reactions presented above, CO 2 is generated in two pyrolysis processes. The CO 2 generated is captured, compressed and directed to Solvay precipitating towers for consumption in a mixture of brine (aqueous NaCl) and ammonia. Although CO 2 is generated as a by-product, the carbon dioxide is recovered and recycled for use in the carbonation stage and in theory the process is neutral, i.e., generation of CO 2 equals uptake. In practice, however, CO 2 is emitted to the atmosphere during the production of soda ash because more CO 2 is produced than is stoichiometrically required. The excess CO 2 is produced by calcining limestone with metallurgical grade coke (approximately 7 per cent of limestone weight). In order to avoid double counting, CO 2 emissions associated with the use of coke in soda ash production should be accounted for separately and those emissions associated with the non-energy use of coke subtracted from the totals in the combustion section. Carbon dioxide emissions are associated with the use of soda ash. Some of the major uses include glass manufacture, chemicals, soaps, detergents and flue gas desulphurisation. For each of these uses, it is assumed that for each mole of soda ash use, one mole of CO 2 is emitted (U.S. EPA, 1994b).



### 2.6.2 Emission Estimation Methodology for CO 2 Soda Ash Production From stoichiometric considerations, the industrial process emission of CO 2 associated with the Solvay process is zero. The excess CO 2 emitted from soda ash production originates from coke oxidation (see the Energy Chapter for appropriate emission rate for coke combustion and use appropriate national statistics on coke use in soda ash production). For processes utilising trona, emissions can be calculated by the following formula:

EF = 0.097 tonne CO 2 / tonne of Trona

During the production of soda ash in the Solvay process, calcium chloride is produced. In cases where calcium chloride is discharged to the sea, calcium chloride dissolves to form calcium and chloride ions. Calcium ions in turn take part in a number of chemical reactions, including the sequestering of carbonate ions to form calcium carbonate which represents a sink for CO 2 . Available experimental data from Australia indicate that approximately 0.23 tonnes of CO 2 is sequestered from the ocean for each tonne of soda ash produced (Workbook, Australia, 1995).

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.13 Soda Ash Use For each mole of soda ash use, one mole of CO 2 is emitted, so that the mass of CO 2 emitted from the use of soda ash may be estimated from a consideration of consumption data and the stoichiometry of the chemical process as follows:

EF = 44.01 g/mole CO 2 /105.99 g/moleNa 2 CO 3 = 415 kg CO 2 /tonne Na 2 CO 3



## 2 . 7 P r od u c t i on a n d U s e of Mi s c e l l a n e ou s Mineral Products

2.7.1 Asphalt Roofing Production This is the production of saturated felt, roofing and siding shingles and roll roofing and sidings. Most of these products are used in roofing and other building applications. Emissions from these processes can be estimated from the national total mass of products. The emission factors in Table 2-3 given in the EMEP/CORINAIR Guidebook (SNAP 40610) are default factors.

T ABLE 2-3 E MISSION F ACTORS FOR A SPHALT R OOFING P RODUCTION ( KG / TONNE PRODUCT )

Emission Factor (Saturation with Spray) Emission Factor (Saturation without Spray)
NMVOC 0.13 - 0.16 0.046 - 0.049 CO NAV 0.0095 NAV = Not Available
Asphalt blowing (SNAP 60310) is the process of polymerising and stabilising asphalt to improve its weathering characteristics. Air blown asphalts are used in the production of asphalt roofing products. The blowing may take place in a refinery, an asphalt processing plant or an asphalt roofing plant. This activity leads to emissions of NMVOC. The emission factors in the EMEP/CORINAIR Guidebook range from 0.1 to 30 kg total organic compounds/tonne asphalt blown depending on the degree of control and it may be assumed that all the mass of asphalt used for non-paving use will be blown.

## I NDUSTRIAL 

## P ROCESSES

2.14 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.7.2 Road Paving with Asphalt Asphalt road surfaces are composed of compacted aggregate and asphalt binder. Gases are emitted from the asphalt plant, the road surfacing operations and from the subsequent road surface. The emissions of NMVOC depend on the type of asphalt (slow, medium or rapid cure) and the amount of diluent. Emission factors given in Table 2-4 use the default assumptions given in the EMEP/CORINAIR Guidebook (SNAP 40611). The amount of diluent used is usually lower in warm countries than in the colder, and hence lower emission factors may be expected in warm countries.

T ABLE 2-4 E MISSION FACTORS FOR ROAD PAVING WITH ASPHALT ( KG / TONNE ASPHALT )

SO 2 NO x CO NMVOC Asphalt Plant 0.12 0.084 0.035 0.023
Road Surface NAV NAV NAV 320

If the tonnes of asphalt paved is not known but rather the area paved, a conversion factor of 100 kg asphalt/m 2 road surface may be used.



### 2.7.3 Production of Other Mineral Products There may be several other mineral production processes emitting pollutants. These are probably not significant on a global scale, but may be significant on a national or local scale. There is generally little information about emissions from these processes. One emission source is the production of concrete pumice stone. As for cement production, SO 2 emissions will originate from the fuel use and sulphur in clay. About 45 per cent of the SO 2 generated in the process will be sequestered in the product. An emission factor of about 0.5kg SO 2 /tonne product has been calculated from measurements in Norwegian plants (Rypdal 1995), and used where plant-specific data are not available. NMVOCs may be emitted from manufacture of glass. An emission factor of 4.5 kg/tonne product has been derived from CASPER (1995).



## 2 . 8 Am m on i a P r od u c t i on

2.8.1 Overview In most instances, anhydrous ammonia is produced by catalytic steam reforming of natural gas (mostly CH 4 ) or other fossil fuels. As can be seen in the following reactions with methane as a feedstock, carbon dioxide is produced.

C + H 2 O → CO + H 2 CH 4 + H 2 O → CO + 3H 2 N 2 + 3H 2 → 2NH 3

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.15 In general, the processes that affect CO 2 emissions in the production of ammonia are:

• carbon monoxide shift at two temperatures using iron oxide, copper oxide and/or chromium oxide catalyst for conversion to carbon dioxide;

• carbon dioxide absorption by a scrubber solution of hot potassium carbonate, monoethanolamine (MEA), Sulfinol (alkanol amine and tetrahydrothiophene dioxide) or others;

• methanation of residual CO 2 to methane with nickel catalysts to purify the synthesis gas. Natural gas is used as the feedstock in most plants, while other fuels (e.g., heavy oils) may be used with the partial oxidation process. In addition, plants may use by-product hydrogen, rather than natural gas, to produce ammonia (thereby eliminating the release of CO 2 from the synthesis process) (CFI, 1992). The production of ammonia represents a significant non-energy industrial source of CO 2 emissions.



### 2 . 8 . 2 P r o c e s s D e s c r i p t i o n The primary release of CO 2 at plants using the natural gas catalytic steam reforming process occurs during regeneration of the CO 2 scrubbing solution with lesser emissions resulting from condensate stripping. Carbon Dioxide Regenerator After absorption of CO 2 from the process gas, the saturated scrubbing solutions (e.g., potassium carbonate, MEA, etc.) are regenerated (i.e., for re-use) with steam stripping and/or boiling to release CO 2 from the bicarbonates according to the following reactions:

Heat 2KHCO 3 → K 2 CO 3 + H 2 O + CO 2 Heat (C 2 H 5 ONH 2 ) 2 + H 2 CO 3 → 2C 2 H 5 ONH 2 + H 2 O + CO 2

The stripping gas, containing CO 2 and other impurities, may be directed to a urea plant (where operational), to a liquid carbonic acid plant, or vented to the atmosphere (Environment Canada, 1987). Condensate Stripper Cooling the synthesis gas after low temperature shift conversion forms a condensate containing small quantities of CO 2 and other process impurities. The condensate is stripped by steam, whereby the components may be vented to the atmosphere, but normally recycled to the process together with the process stream (U.S. EPA, 1985).



### 2.8.3 Emission Estimation Methodology for CO 2 Emissions of CO 2 will depend on the amount and composition of gas (or oil) used in the process. It is assumed that all carbon will be emitted to air. It is recommended that inventory contributions are compiled using point source methods due to the rather limited number of plants. Where greatest accuracy is desired, this will require direct contact with producers. Alternatively, total sector emissions may be determined on an area source basis using available emission factors and methods noted below.

## I NDUSTRIAL 

## P ROCESSES

2.16 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The most accurate method of estimation will be:

Emission (kt) = Consumption of gas (kt) x carbon content x 44/12

If the gas consumption is not available, an alternative is to calculate the emissions from the ammonia production:

Emission (kt) = Production of ammonia x Emission factor

In both cases, in order to avoid double counting, the quantities of oil or gas used must be subtracted from the quantity reported under energy and non-energy use in the Energy Chapter

. The CO 2 from ammonia production may be used for producing urea or dry ice. This carbon will only be stored for a short time. Therefore, no account should consequently be taken for intermediate binding of CO 2 in downstream manufacturing processes and products.
Emission Factor Information If the emissions are calculated from the gas or oil consumption, the standard emission factors suggested in the energy chapter will be relevant. The carbon content of natural gas may vary, and it is recommended that this is determined for each plant. Some emission factors related to the production of ammonia are shown in Table 2-5.

T ABLE 2-5 A MMONIA P RODUCTION E MISSION F ACTORS Country Emission Factor a , b Tonne CO 2 /tonne NH 3 produced Reference

Canada c 1.6 Jaques, 1992 Industrial Chemicals, 1980 Norway 1.5 Norsk Hydro, 1996

a Reductions should be applied to account for any ammonia that is produced from by-product hydrogen. b Figure for Norway excludes gas used as a fuel. It is not clear if this is included in the Canadian figure. The figures are dependent on the carbon content in the feedstock.

c Assumes 812 m 3 gas/tonnes NH 3 and 0.525 kg carbon/m 3 gas.



### 2 . 8 . 4 E m i s s i o n E s t i m a t i o n M e t h o d o l o g y f o r Ozone Precursors and SO 2 The production of ammonia is described in Section 2.8.1. However, emission methods have not yet been developed for the EMEP/CORINAIR Guidebook (SNAP 40403).
SO 2 , NO x , CO and NMVOC may be emitted in addition to CO 2 . Default emission factors for uncontrolled emissions in Table 2-6 are taken from U.S. EPA 1995.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.17 T ABLE 2-6 E MISSION FACTORS FOR AMMONIA PRODUCTION ( KG / TONNE PRODUCT )

SO 2 TOC a CO Desulphurisation 0.03 3.6 6.9 Carbon dioxide regenerator NE 0.5 1.0 Condensate steam stripper NE 0.6 NE
Total 0.03 4.7 7.9

a Total organic compounds NE = negligible

There will usually be few ammonia plants in a country, and it is recommended that emissions from plant specific data be estimated.



## 2.9 Nitric acid Production

2.9.1 Overview The production of nitric acid (HNO 3 ) generates nitrous oxide (N 2 O) as a by-product of the high temperature catalytic oxidation of ammonia (NH 3 ). Nitric acid is used as a raw material mainly in the manufacture of nitrogenous-based fertiliser. Nitric acid may also be used in the production of adipic acid and explosives (e.g., dynamite), for metal etching and in the processing of ferrous metals. Nitric acid production involves three distinct chemical reactions:

4NH 3 + 5O 2 → 4NO + 6H 2 O 2NO + O 2 → 2NO 2 3NO 2 + H 2 O → 2HNO 3 + NO

Nitrous oxide generation during the production of nitric acid is not well documented. Nitrogen oxidation steps under overall reducing conditions are considered to be potential sources of N 2 O. Nitric oxide (NO), an intermediate in the production of nitric acid, is also documented to readily decompose to N 2 O and nitrogen dioxide (NO 2 ) at high pressures for a temperature range of 30 to 50 ° C (Cotton and Wilkinson, 1988).



### 2.9.2 Emission Data of N 2 

### O Table 2-7 gives examples of emissions factors from nitric acid production plants, based on measurements. Emission rates depend upon technology and operating conditions.

## I NDUSTRIAL 

## P ROCESSES

2.18 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-7 E MISSION FACTORS FOR N 2 O FROM NITRIC ACID PRODUCTION

Emission Factor kg N 2 O/tonne nitric acid Reference

USA 2-9 a Reimer et al., 1992 Norway: - modern, integrated plants <2 Norsk Hydro, 1996 - atmospheric pressure plants 4-5 “ - medium pressure plants 6-7.5 ” Japan 2.2-5.7 Japan Environment Agency, 1995 a. Emission factors up to 19 kg N 2 O/tonne nitric acid have been reported for plants not equipped with nonselective catalytic reduction technology (NSCR) (Choe et al., 1993; Olivier, 1996; Oonk, 1996).


### 2.9.3 Emission Estimation Methodology for N 2 

### O There are usually only very few plants in each country producing nitric acid, so measured data on N 2 O emissions are often available. These data also take into account the effect of any abatement technology installed at the specific plants. Emissions vary significantly from one plant to another, and if measured data are available, emission estimates should be based upon such data. Every effort should therefore be made to obtain measurement data. However, if such data are not available, emissions should be calculated from production data of nitric acid within a country, and specific emission figures based on the actual technology, for which Table 2-7 can be consulted. When no measured data exist, specific emission factors at the upper end of the appropriate range should be chosen.

N 2 O-emissions = Production level x Specific Emission Factor



### 2.9.4 Emission Estimation Methodology for NO X Nitric acid is produced from the catalytic oxidation of ammonia. The process is described in Section 2.9.1 and in the EMEP/CORINAIR Guidebook (under SNAP 40402). In addition to the GHGs described in Section 2.9.1, there may be non-combustion emissions of NO x . Emissions are estimated from the amount of nitric acid produced. Factors range from 0. 1- 1.0 NO x /tonnes acid produced for the direct strong acid production process to 10- 20 kg/tonnes acid produced for the low pressure process. 12.0 kg NO x /tonnes nitric acid should be used where the process and technology details are not known. There will usually be few nitric acid plants in a country, and it is recommended that emissions are calculated from plant specific data.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.19 

## 2.10 Adipic Acid Production

2.10.1 Overview Adipic acid is used in the manufacture of a large number of products including synthetic fibres, coatings, plastics, urethane foams, elastomers and synthetic lubricants. The production of Nylon 6.6 accounts for the bulk of adipic acid use. Adipic acid is a dicarboxylic acid manufactured by a two-stage process. The first stage of manufacturing involves the oxidation of cyclohexane or cyclohexanone to form a cyclohexanone/cyclohexanol mixture. The mixture is then oxidised by nitric acid in the presence of a catalyst to form adipic acid. N 2 O is generated as a by-product of the nitric acid oxidation stage:

(CH 2 ) 5 CO + (CH 2 ) 5 CHOH + wHNO 3 (Cyclohexanone) (Cyclohexanol)

→ HOOC(CH 2 ) 4 COOH (Adipic Acid) + x N 2 O + yH 2 O

Adipic acid production also results in the emissions of NMVOC, CO and NO x . Process emissions from the production of adipic acid vary substantially with the level of emission control employed.



### 2 . 1 0 . 2 E m i s s i o n E s t i m a t i o n M e t h o d o l o g y f o r N 2 

### O Adipic acid production unavoidably produces N 2 O as a by-product with an associated emission factor (for unabated emissions) of 300g N 2 O/kg adipic acid produced (Thiemens and Trogler, 1991). Japanese emissions (measured at 264 g N 2 O/kg adipic acid) are consistent with this value (Japan Environment Agency, 1995).

N 2 O emissions (kg) = Adipic Acid Production(tonnes) x 300 kg N 2 O/ tonne Adipic Acid

Often, the abatement of N 2 O results from the treatment of the off-gases 4 in a reductive furnace. A number of adipic acid producers treat the off-gases with the aim of reducing NO x emissions, but the treatment also destroys N 2 O (Reimer et al., 1992). There is a range of abatement efficiencies attainable with currently available technologies. Any reduction in N 2 O emissions due to the installation of abatement systems should be assessed on a plant-specific basis where possible.

4 “Off-gases” are gases that are released from the process.

## I NDUSTRIAL 

## P ROCESSES

2.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2 . 1 0 . 3 E m i s s i o n E s t i m a t i o n M e t h o d o l o g y f o r Ozone Precursors The production of adipic acid is described in Section 2.10.1 and (under SNAP 40521) in the EMEP/CORINAIR Guidebook. The EMEP/CORINAIR Guidebook indicates that there may be emissions of CO 2 , NO and NO 2 in addition to N 2 O, but does not propose emission factors at present. Furthermore, European reported emission data indicate that pollutants other than N 2 O are not significant (CORINAIR-90). U.S. EPA emission factors are given in Table 2-8 (U.S. EPA 1995).

T ABLE 2-8 E MISSION FACTORS FOR ADIPIC ACID PRODUCTION ( KG / TONNE PRODUCT )

NO X CO VOC
8.1 34.4 43.3



## 2 . 1 1 C a r b i d e P r od u c t i on

2.11.1 CO 2 

### and CH 4 

### from Silicon Carbide Production In the production of silicon carbide , CO 2 is released as a by-product from a reaction between quartz and carbon. Petrol coke is used as a carbon source. Silicon carbide is extremely hard and is widely used as an abrasive. The formula describing the reaction is given below but in practice it does not proceed in the stoichiometric proportions indicated.

O 2 SiO 2 + 3C → SiC + 2CO → 2CO 2

Some carbon, about 35 per cent, is sequestered in the product. Generally, the emissions from silicon carbide production can be calculated from a mass balance approach as:

CO 2 emissions (tonnes) = A x C (100-S) x 3.67 x 10 -4

where: A = consumption of coke in tonnes C = per cent carbon content in coke S = per cent carbon input sequestered in product

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.21 Typical default values for Norwegian plants for C (carbon content in coke) are 97 per cent and for S (sequestered carbon in product), 35 per cent. This implies a typical emission factor of 2.3 tonnes CO 2 /tonne coke. More carbon is actually needed in the process than calculated from a stoichiometric reaction. The suggested emission factors are calculated from coke input in Norwegian plants. The excess carbon is oxidised during the process, little is left as ash (Raaness, 1991). The petrol coke used in this process may contain volatile compounds which will form methane. Some of this methane will escape to the atmosphere, particularly during the start up. Measurements at Norwegian plants suggest emission factors of 10.2 kg/tonne petrol coke or 11.6 kg/tonne carbide product.



### 2.11.2 CO 2 

### from Calcium Carbide Production Calcium carbide is made by heating calcium carbonate and subsequently reducing CaO with carbon (e.g., petrol coke). Both steps lead to emissions of CO 2 . Some carbon will be sequestered in the product. The most important application of calcium carbide is producing acetylene. Consequently, the sequestering will be for a short time only (less than a few years) and may be disregarded. On the other hand Ca(OH) 2 is produced as a by-product in the acetylene production. This Ca(OH) 2 will react with CO 2 to form CaCO 3 . Hence, the CO 2 emitted from the limestone may be said to be recycled.
Production of CaC 2 :

CaCO 3 → CaO + CO 2 CaO + 3C → CaC 2 + CO ( → CO 2 )

Use of carbide:

CaC 2 + 2H 2 O → Ca(OH) 2 + C 2 H 2 → 2CO 2

The CO gas will in most plants be utilised as energy. 1.8 tonnes CO 2 /tonne calcium carbide will be released in the production process. In addition, 1.1 tonnes CO 2 /tonne calcium carbide will be released when the carbide is used. The CO 2 emissions may be lowered by utilising the gas when producing dicyanodiamide from carbide (Olsen 1991). Limestone contains about 98 per cent CaCO 3 . 1750 kg limestone (or 950 kg CaO) and 640 kg reducing agent (including 20 kg carbon electrodes) are required to produce 1 tonne carbide. Emissions may be calculated from the use of raw materials (limestone and coke) or from the production.

## I NDUSTRIAL 

## P ROCESSES

2.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The emission factors in Table 2-9 are suggested in the latter case:

T ABLE 2-9 E MISSION FACTORS ( KG CO 2 / TONNE CARBIDE )

Limestone 760
Reduction 1090 Use of product 1100

The theoretical emission factor calculated from a stoichiometric reaction is 1.37 tonne CO 2 /tonne carbide (for the carbonate and coke step). Excess carbon is however oxidised in the process. The suggested emission factors are calculated from the actual use of raw materials in a Norwegian plant. The emission factor for acetylene use is calculated from the actual (not stoichiometric) carbon content of carbide. Also note that the CaO (lime) might be produced at another plant than the carbide plant. In this case, the emissions from the CaO step should be reported as emissions from lime production (Section 2.4) and only the emissions from the reduction step and use of product should be reported as emissions from calcium carbide production.



### 2 . 1 1 . 3 P r e c u r s o r s a n d S O 2 

### from Carbide Production Emission methods have not yet been developed for the EMEP/CORINAIR Guidebook. SO 2 is potentially emitted from the production processes due to sulphur in the raw coke material. Silicon carbide: The emissions are most accurately calculated from the consumption of coke, the sulphur content of the coke, and the degree of control. In addition, CO is emitted due to incomplete oxidation of carbon coke. An emission factor of 0.4 tonne CO/tonne petrol coke has been determined for Norway (Rosland 1987), but this factor will be highly plant specific. Calcium carbide: Nearly 100 per cent of the SO 2 potentially emitted will be sequestered in the product (Rypdal 1995, Rosland 1987). An emission factor of 1.5 kg SO 2 /tonne coke is given in U.S. EPA 1995, but no experimental methods or assumptions are given. CO is generated in the process, but is usually oxidised in the process, used as a fuel or flared. This should be checked for the relevant plants.



## 2.12 Production of Other Chemicals

2.12.1 N 2 

### O Emissions Production of chemicals other than nitric acid and adipic acid may be sources of nitrous oxide, but more studies are needed to determine whether they represent a significant source of N 2 O. Production of caprolactam, acrylonitrile, and catalytic cracking of oil, may be significant sources. Generally, suggested sources are related to either a process using a N-compound or a catalytic reduction step. Compared to emissions associated with

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.23 adipic acid and nitric acid production, the N 2 O emissions from this source category will probably be small. Caprolactam is a widely used chemical intermediate. Most of the 3 million tonnes produced per year is used in the production of nylon-6 (Fisher and Crescenti, 1994). Different methods are used for the manufacture of caprolactam. They are all based on catalytic oxidation of ammonia. In the Netherlands, caprolactam production was identified as a significant industrial source of N 2 O (Kroeze, 1994). In order to increase the yield of gasoline from oil, certain fractions from the oil are treated in a catcracker. Crude oil contains some nitrogen, and the nitrous oxide emissions from the cracking process may be significant. Depending on the regional market for light and medium-light oil products, catalytic cracking is more or less important in a specific region. A few studies on emissions from this source have been performed in the Netherlands but presently data are not available to suggest a methodology (Oonk, 1996). Therefore, a general recommended method for estimation of N 2 O emissions from these sources is not given here.



### 2.12.2 CH 4 

### Emissions Although most methane sources from industrial processes individually are small, collectively they may be significant. Chemical manufacturing processes, e.g., carbon black, ethylene, dichloroethylene, styrene and methanol, are potential sources of methane. However, sources other than those mentioned here may be of importance. Few data on emissions are presently available. These are presented in Table 2-10:

TABLE 2-10
EMISSION FACTORS ( G CH 4 / KG P RODUCTION )

Emission factor (g CH 4 /kg production) Reference

Carbon black 11 Shareef et al., 1988, Stockton and Stelling 1987. Ethylene 1 Shareef et al., 1988, Stockton and Stelling 1987. Dichloroethylene 0.4 Shareef et al., 1988, Stockton and Stelling 1987. Styrene 4 Shareef et al., 1988, Stockton and Stelling 1987. Methanol 2 Shareef et al., 1988, Stockton and Stelling 1987. Coke 0.5 Schade, 1980, Barnard, 1990.

## I NDUSTRIAL 

## P ROCESSES

2.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.12.3 Emissions of Ozone Precursors and SO 2 This section is concerned with emissions from small point sources. However, total emissions from these sources may be important. Only a simple methodology is suggested here. It should be noted that some of these sources may be individually very important in certain countries. In these cases a more detailed methodology should be used, based on plant specific data. The EMEP/CORINAIR Guidebook and the U.S. EPA guidelines should be consulted for advise on detailed methodologies and process descriptions. A summary of default emission factors and ranges is given in Table 2-11. Ranges given for VOC emissions from many processes are quite large. Emission factors are likely to be quite process specific. For instance, polystyrene is manufactured in various grades by batch or continuous process. Higher emission factors are associated with the lower molecular weight of polystyrenes. The variation in emission factors from plants using the continuous process is quite large, depending upon the type of vacuum system employed (U.S. EPA 1995). Evaporative emissions from petrochemical industries may be higher in warm than in temperate countries.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.25 T ABLE 2-11 E MISSION FACTORS FOR MISCELLANEOUS PRODUCTION PROCESSES IN CHEMICAL INDUSTRIES . ( KG / TONNE PRODUCT )

Source SNAP SO 2 NO x NMVOC CO Acrylonitrile 40520 -

- 1 (0.4-100)

- Acrylonitrile Butadiene Styrene (ABS) Resins 40515 -

- 27.2 (1.4-27.2)

-

Carbon black 40409 3.1 0.4 40 (5-90) 10 (5-14) Ethylbenzene 40518 -

- 2 (0.1-2)

- Ethylene and propylene 40501/40502 -

- 1.4

- Formaldehyde 40517 -

- 5 (0-8)

- Graphite 40411 -

- NAV

- Phtalic anhydride 40519 -

- 6.0 (1.3-6.0)

- Polypropylene 40509 -

- 12 (0.35-12)

- Polystyrene 40511 -

- 5.4 (0.2-5.4)

- Polyethene - Low density 40506 -

- 3

- Polyethene - Linear low density - -

- 2

- Polyethene - High density 50507 -

- 6.4

- Polyvinylchloride 40508 -

- 8.5 (0.14-8.5)

- Styrene 40510 -

- 18 (0.25-18)

- Styrene butadiene 40512-14 -

- NAV

- 1,2, dichloroethane 40503 -

- 7.3 (0.2-7.3)

- Sulphuric acid 40401 17.5 (1-25)

- - - Titanium dioxide 40410 14.6 (0.9-14.6)

- - - Urea 40408 NAV NAV NAV NAV Vinyl chloride a 40504
1,2, dichloroethane 40505 -

- 2.2

- Source: EMEP/CORINAIR guidebook, except the CASPER project (CASPER 1995).
a The emission factors should be used for the monomer and polymer separately even if they are produced at the same plant unless otherwise specified. NAV = Not available. Note: Ranges in brackets.

## I NDUSTRIAL 

## P ROCESSES

2.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 2.13 CO 2 

## Emissions from Metal Production

2.13.1 CO 2 

### from Metal Production - General Methodology With a few exceptions, commercial production of metals from ores requires the use of carbon as a reducing agent. If the ore contains carbonate, CO 2 originating from the ore will also be emitted during production. On the other hand, carbon may also be sequestered in the metal. The metal may be reduced by using coal, coke, prebaked anodes and coal electrodes. Wood chips and charcoal may also be used in some of the processes, but the resulting CO 2 emissions are not counted in Chapter 2 as net emissions. These net emissions of CO 2 should, however, be reported in the Land-Use Change and Forestry Chapter. Coke is produced from coal or refinery residuals (petrol coke). Prebaked anodes and electrodes are produced from coal. By-product fuel (coke oven gas and blast furnace gas) are produced in some of the processes. These fuels may be sold or used within the plant. They may or may not be included in the national energy balance. Care should consequently be taken not to double count emissions. The following general formula may be used to estimate the emissions:
Mass Reducing Agent x Emission Factor + (Carbon ore - Carbon metal) x 3.67 = Emission (tonnes CO 2 )

The first part of this formula (the amount of reducing agent used combined with an emission factor) will usually be most important and probably be sufficient for making a first estimate of the emissions. The emission factors in Table 2-12 are suggested as default.

T ABLE 2-12 CO 2 EMISSION FACTORS FOR METAL PRODUCTION GENERALLY ( TONNE CO 2 / TONNE REDUCING AGENT )
Reducing Agent Emission Factor a

Coal b 2.5
Coke from coal b 3.1
Petrol coke 3.6
Prebaked anodes and coal electrodes 3.6

a If better information on actual carbon content is not available nationally or cannot be calculated from data in the Energy Chapter. b Derived from data in the Energy Chapter

In addition, CO 2 will be emitted from baking (prebaked anodes). In the aluminium industry about 5 per cent of the non-combustion CO 2 emissions using the prebaking technology will be from baking. No data is available for other metal industries using prebaked anodes.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.27 

### 2 . 1 3 . 2 O v e r v i e w o f E m i s s i o n s o f O z o n e Precursors and SO 2 

### from Metal Production Production of most metals may generate emissions of SO 2 , CO, NO x and NMVOC. Emissions of SO 2 originate from sulphur in the reducing agents and in the ores. The emissions will also depend on control technologies and the extent to which sulphur is sequestered in the products.
NO x is produced primarily by the high temperate oxidisation of nitrogen in air. In metal production, most NO x emissions usually occur as a result of fuel combustion. However, high temperate metal production processes (such as roasting and reduction), which occur in the presence of air, will also produce nitrogen oxides. These NO x emissions are in principle included in this section, but are often impossible to distinguish from the fuel NO x . CO is formed due to incomplete oxidation of the reducing carbon. This CO may in many plants be used as a fuel, and double counting of emissions already counted as energy must be avoided. In addition, small amounts of NMVOCs may be emitted during parts of some of the processes, especially those involving coal.



### 2.13.3 Iron and Steel

2.13.3.1 Overview Iron is produced through the reduction of iron oxide (ore) using metallurgical coke as the reducing agent in a blast furnace. Steel is then subsequently made from iron and scrap in other furnaces. This sector includes two types of facilities. Large integrated primary iron and steel plants have coking, smelting and refining capacities to produce steel from raw coal and iron ore. Other, smaller plants produce iron and steel from coke generated off-site. The coke oven used at an integrated plant is identical to that used at off-site coking facilities. In the integrated plant, coke oven gases (COGs) are used both for oven under firing and combustion in the blast furnace and other parts of the process. Common to all plants is a blast furnace, which reduces raw ore to molten pig iron by heating in the presence of carbon and oxygen. Coke, the source of carbon, has been estimated to be consumed at a rate of about 450 kg/tonne of hot metal (Rankin and Wright, 1992). “Flux” in the form of limestone (CaCO 3 ) or dolomite is also added to the furnace at a rate of about 250 kg/tonne of iron (U.S. EPA 1986). Steel may be produced in a basic oxygen furnace (BOF), an electric arc furnace (EAF), an induction furnace or an open hearth furnace. The open hearth type is the oldest technology. Low carbon steel is produced in a BOF, where a mixture of pig iron and iron scrap is remelted in the presence of pure oxygen, which oxidises the dissolved carbon to carbon monoxide or carbon dioxide. Carbon and alloy steels are produced in an EAF, a refractory-lined pot which utilises electric heating through graphite electrodes which are consumed in the process. This type is charged with 100 per cent scrap iron.

## I NDUSTRIAL 

## P ROCESSES

2.28 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.13.3.2 Emission Estimation Methodology for C O 2 Process emissions of carbon dioxide in an iron and steel plant take place primarily as a result of coke oxidisation. Additional emissions occur as the limestone flux gives off carbon dioxide during reduction of pig iron in the blast furnace, but this source is covered as emissions from limestone use (Section 2.5). During steel production, CO 2 emissions also take place as a result of graphite electrode consumption in the EAF. Pig iron (impure iron) contains about 4-4.5 per cent carbon by weight. In the conversion of pig iron to steel the carbon content is reduced to below 2 per cent by weight. The process takes place in a steel furnace which has been charged with pig iron, usually recycled iron or steel and alloying elements to improve material properties. As the carbon is removed from the pig iron, CO 2 and CO are evolved. The lost CO-carbon is eventually converted to carbon dioxide by combustion. This should not be considered as an energy emission, as it is inherently part of the iron reduction process. Care should be taken not to double count these emissions (when performing the energy balance). The most accurate methodology is to calculate the emissions from the amount of reducing agent used as described in 2.13.1. Parsons (1977) and ORTECH (1994) have studied the consumption of carbon at iron and steel production facilities. These results have been summarised by Environment Canada (1996). Emission factors per unit iron or steel produced are shown in Table 2-13.

T ABLE 2-13 CO 2 EMISSION FACTOR FOR IRON AND STEEL PRODUCTION ( TONNES CO 2 / TONNE IRON OR STEEL PRODUCT )
Country Description Emission Factor Reference
Canada a Integrated facility b (coke plus iron and/or steel production). 1.6 Environment Canada (1996)

a Includes CO 2 produced by coke and coke oven gas consumption. It does not include any form of conventional energy consumption. The emission factor applies to both iron or iron plus steel production, since uncertainty in the estimates overshadow the incremental difference in CO 2 emissions. b Environment Canada has reported an emission factor of approximately 1.5 tonnes CO 2 /tonne iron or steel for a non-integrated facility. This is, however, a rather uncertain value. Note: Figures exclude CO 2 from flux (CaCO 3 ) consumption.



### 2.13.3.3 Emission Estimation Methodology for Ozone Precursors and SO 2 Emissions from iron and steel may originate from various stages of the production process. Iron production:

• Blast Furnace Charging: Primary iron production in smelters. No process emission factors are given in the EMEP/CORINAIR Guidebook (SNAP 40202). In the CASPER model (CASPER 1995) emission factors of NMVOC are given as 100 g/tonne product (range 20-200) and CO is given as 1330 g/tonne product (range 1180-20000).

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.29 Preliminary research from Environment Canada suggests that sulphur dioxide emissions from the blast furnace may be 1000-3000 g SO 2 /tonne of iron produced.

• Pig Iron Tapping: This involves the removal of the molten pig iron from the smelter. While it does give rise to emissions of a range of heavy metals, according to the EMEP/CORINAIR Guidebook no appreciable emissions of the four gases occur. In the CASPER model (CASPER 1995) the following emission factors are given: SO 2 : 30 g/tonne product, NO x : 76 g/tonne product, CO: 112 g/tonne product and NMVOC: 20 g/tonne product. Steel production:

• Open Hearth Furnace: Steel is produced in the open hearth furnace fired by gas or fuel oil. No data exist for process emission from open hearth furnaces.

• Basic Oxygen Furnace Steel Plant: Pure oxygen is blown into the furnace via a lance. Burning CO maintains exothermic conditions. Most CO emissions are therefore eliminated. The EMEP/CORINAIR Guidebook (SNAP 40206) provides no emission factors for the gases.

• Electric Furnace Steel Plant: This type of furnace is usually charged with 100 per cent scrap iron. Graphite electrodes conduct current through the metal to heat the charge. Emissions are dependent upon the quality of scrap metal and operating conditions. The EMEP/CORINAIR Guidebook (SNAP 40207) does not give any emission factors for the gases of interest. Steel processing:

• Rolling Mills: Rolling mills use a range of different processes and emit differing amounts of pollutants according to the specific processes used. Most of the emissions from rolling mills are from the fuel used to heat the process. However cold-rolling will emit a range of gases in addition to the fuel combustion emissions. The emission factors expressed as the amount of steel cold rolled are taken from the EMEP/CORINAIR Guidebook (SNAP 40208) and are shown in Table 2-14. Note that SO 2 , NO 2 and CO emission factors are only given for process smelter gas (as sometimes used for rolling pretreatment).

T ABLE 2-14 E MISSION FACTORS FOR ROLLING MILLS ( G / TONNE STEEL PRODUCED )
Pollutant Emission Factor (default) Emission Factor (Range)
SO 2 a 45 30-60
NO x a 40 20-50
CO a 1 0.3-1
NMVOC 30 20-30

a from process smelter gas

## I NDUSTRIAL 

## P ROCESSES

2.30 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.13.4 Ferroalloys

2.13.4.1 Overview Ferroalloy is the term used to describe concentrated alloys of iron and one or more metals such as silicon, manganese, chromium, molybdenum, vanadium and tungsten

. These alloys are used for deoxidising and altering the material properties of steel

. Ferroalloy facilities manufacture concentrated compounds which are delivered to steel production plants to be incorporated in alloy steels

. Ferroalloy production involves a metallurgical reduction process which results in significant carbon dioxide emissions. In ferroalloy production, raw ore, coke and slagging materials are smelted together under high temperature

. A commonly used technology is the submerged-arc open-top electric furnace (EAF) (Environment Canada, 1983; Ontario Research Foundation, 1981)

. In the EAF, heating is accomplished by passing current through graphite electrodes suspended in a cup-shaped, refractory-lined steel shell

. Carbon reduction of the metallic oxides occurs as both coke and graphite electrodes are consumed. During ferroalloy smelting, the reduction reaction takes place at a high temperature

. Carbon captures the oxygen from the metal oxides to form CO, while the ores are reduced to molten base metals

. The component metals then combine in the solution

. For example, the following reaction occurs in the production of 50 per cent ferrosilicon (AWMA, 1993):

Fe 2 O 3 + 2 SiO 2 + 7C → 2FeSi + 7CO

Primary emissions in covered arc furnaces consist almost entirely of CO as opposed to CO 2 , due to the strong reducing environment (ORTECH, 1994)

. All CO is assumed, however, to be converted to CO 2 within days afterwards.


### 2.13.4.2 Emission Estimation Methodology for C O 2 The most accurate methodology is to calculate the emissions from the amount of reducing agent used as described in Section 2.13.1

. Alternatively, the emissions may be calculated from the production volume

. However, it is impossible to suggest default factors for this process

. Ferroalloy production may more or less be based on biological carbon (wood and wood waste)

. To the extent that the biocarbon is replaced and that electricity is produced from e.g., hydro power, the production of ferroalloys may in principle be CO 2 free

. However, in most countries a production based on biocarbon only will not be economical feasible

. The suggested emission factors (Table 2.15) assume (if not otherwise specified) that all carbon is fossil and are derived from a material balance made by SINTEF (SINTEF 1991a) and Streibel (1974).

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.31 T ABLE 2.15 CO 2 EMISSION FACTORS FOR FERROALLOY PRODUCTION ( TONNES / TONNE PRODUCT )
Type Ferroalloy Emission Factor
Ferrosilicon - 50%Si 2-2.7
Ferrosilicon - 75%Si 3.9
Ferrosilicon - 90%Si 4.8-6.5
Silicon metal a 4.3 Ferromanganese 1.6 Silicon manganese 1.7
Ferrochromium 1.3
Ferrochromium-silicon NAV

a All producers probably use some biocarbon in order to obtain the desired product properties. 1.6 tonne bioCO 2 /tonne silicon may be considered as a minimum value and is not included in the emission factor in the table. NAV = Not Available



### 2.13.4.3 Emission Estimation Methodology for Ozone Precursors and SO 2 SO 2 , CO, NO x and NMVOC are potentially emitted in the production process as described in Section 2.13.2. Sulphur may be sequestered in the products. For ferromanganese and silicon manganese 98-99 per cent of the sulphur from ore and coke will be sequestered. Of the remaining ferroalloys, assume 5 per cent of the sulphur is sequestered (Rypdal 1995, Rosland 1987). In the CASPER model (CASPER 1995) a factor of 35 g/tonne product has been suggested for ferrosilicon.
NO x will originate from production of ferrosilicon and silicon metal. A factor of 11.7 kg/tonne product has been determined (Rypdal 1995). However, this factor is highly uncertain, and there may also be emissions from the production of other ferroalloys. In the CASPER model (CASPER 1995) 0.05 kg/tonne has been suggested. The emissions of NMVOC originate from coal or coke. The emissions are calculated from the consumption of coal and coke. An emission factor of 1.7 kg/tonne is suggested (Rypdal 1995). The U.S. EPA has published uncontrolled CO emission factors for various ferroalloy products (U.S. EPA 1985). These vary with furnace type. Some of these factors are presented in Table 2-16.

## I NDUSTRIAL 

## P ROCESSES

2.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-16 CO EMISSION FACTORS FOR FERROALLOY PRODUCTION ( KG CO/ TONNE METAL )

Metal Covered Furnace Sealed Furnace
Ferrosilicon - 50%Si 1.09 NAV
Ferrosilicon - 75%Si 1.62 NAV Silicon Manganese NAV 0.84 Source: U.S. EPA reported by ORTECH (1994). NAV = not available.



### 2.13.5 Aluminium

2.13.5.1 Overview Primary aluminium is produced in two steps

. First bauxite ore is ground, purified and calcined to produce alumina. Following this, the alumina is electrically reduced to aluminium by smelting in large pots. During the reduction process, the aluminium smelting pot acts as the electrolysis cell. The pot itself, a shallow steel container, forms the cathode, while the anode consists of one or more carbon blocks suspended in it. In the pot, alumina (Al 2 O 3 ), is dissolved in a fluoride bath consisting primarily of cryolite, Na 3 AlF 6 . Passing electrolysis current through the cell also causes a heating effect through the resistance of the cell which maintains the electrolyte in a liquid state. Molten aluminium is evolved while the anode is consumed in the reaction. However, the carbon functions as a fuel cell and as such substitutes electrical energy consumption. The aluminium forms at the cathode and gathers on the bottom of the pot. The favoured gaseous reaction product is CO 2 :

Al 2 O 3 + 3/2C → 2Al + 3/2 CO 2

Most carbon dioxide is evolved from the reaction of the carbon anode with alumina, but some is formed as the anode reacts with other sources of oxygen (especially air). This occurs during cell operation and, in the case of prebaked electrodes, during anode production at the aluminium plant. Three types of reduction cells are in use: prebaked anode, horizontal stud S ; derberg anode and vertical stud S ; derberg anode. Prebaked anodes have been preferred over S ; derberg cells during the last 20 years because they are more productive and efficient with respect to electrical energy consumption and emit fewer organic compounds (U.S. EPA 1995).


### 2.13.5.2 Emission Estimation Methodology for C O 2 CO 2 emissions may be calculated from the amount of reducing agents used as described in Section 2.13.1. Alternatively, the emissions may be estimated from the production volume of primary metal and the specific consumption of carbon. Emissions factors for

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.33 CO 2 are suggested in Table 2-17 based on SINTEF 1991b and ORTECH 1994. The production and use of carbon anodes for aluminium smelting is a very well established process. Evidence suggests that there is little variation in CO 2 emissions from plants utilising similar technologies. It is very likely that use of the appropriate emission factor, along with the correct activity data, will produce accurate estimates.

T ABLE 2-17 CO 2 EMISSION FACTORS FOR PRIMARY ALUMINIUM PRODUCTION ( TONNES / TONNE PRODUCT )
Pollutant Soderberg Process Prebaked Anode Process

CO 2 1.8 1.5



### 2.13.5.3 Emission Estimation Methodology for Ozone Precursors and SO 2 Emissions of carbon monoxide, nitrogen oxide and sulphur dioxide can be estimated from the amount of aluminium produced

. Emissions may originate from the production process and baking of anodes

. No distinction between the Soderberg and prebaked method is given in the EMEP/CORINAIR Guidebook (SNAP 40301)

. The suggested emission factors are shown in Table 2-18

. No information is given about the degree of control.

T ABLE 2-18 E MISSION FACTORS FOR ALUMINIUM PRODUCTION

( KG / TONNE PRIMARY ALUMINIUM PRODUCED )

Pollutant Process Emission Factor (Default) Emission Factor (Range)
SO 2 Electrolysis 14.2 10-17.5 Anode baking 0.9 0.8-1.0
NO x Electrolysis 2.15 1.3-3.0 Anode baking NE NE CO Electrolysis 135 27-680 Anode baking 400 NAV NE = negligible. NAV = not available.

## I NDUSTRIAL 

## P ROCESSES

2.34 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.13.6 PFCs from Aluminium Production

2.13.6.1 Overview Two PFCs, carbon tetrafluoride (CF 4 ) and carbon hexafluoride (C 2 F 6 ), are known to be emitted from the process of primary aluminium smelting. Aluminium is smelted in large pots by an electrolytic reduction process using carbon electrodes. The pot itself forms the cathode, while the anode consists of one or more carbon blocks. During production, alumina (Al 2 O 3 ) is dissolved in a fluoride melt consisting primarily of cryolite, Na 3 AlF 6 . PFCs are formed during a phenomenon known as the Anode Effect (AE), when alumina levels are low. A forced reaction results when molten fluoride salts at high temperature combine with carbon at the anode to favour the formation of CF 4 and C 2 F 6 . This occurs because, during an AE, voltage rises to a level greater than that corresponding to the Gibbs energy of formation for these gases (Laval University, 1994). When the melt becomes depleted of alumina (reduction to a level of 1.5-2.0 wt %), the AE occurs and the cell voltage rises from the normal value of 4-5 volts to 20-50 volts. This happens very suddenly and, in theory, is due to a sudden increase in electrical resistance across the anode-bath interface. As a result, the voltage rises to continue delivering current across the higher resistance. Competing reactions begin to occur to produce CO, CF 4 and C 2 F 6 in addition to CO 2 . It is believed that the carbon anode becomes completely covered by gas during the AE. The two reactions of interest at this point are:

Na 3 AlF 6 + 3/4C = Al + 3NaF + 3/4CF 4

Na 3 AlF 6 + C = Al + 3NaF + 1/2C 2 F 6

The overall anode gas composition below the anode during an anode effect may be approximately 15 % wt CF 4 , 20 wt % CO 2 , 65 wt % CO and 1 wt % C 2 F 6 (Thonstad, Oygard and Diep, 1994). AEs typically occur between 0.3 to 3 times daily on a given cell and last on the order of 2 to 20 minutes (Unisearch, 1994).



### 2.13.6.2 Emission Data
Measured Emission Data In 1992, the Norwegian aluminium industry measured the emissions of PFCs from their smelters. The measurements in production cells were performed with a photoacoustic gas monitor (Norsk Hydro, 1996), (See Table 2-19). The results were different for prebaked lines (0.02 to 0.18 kg CF 4 /tonne Al) and Søderberg lines (0.15 to 0.9 kg CF 4 /tonne Al).

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.35 T ABLE 2-19 M EASURED EMISSIONS OF PFCS FROM PRIMARY ALUMINIUM PRODUCTION Norway (Norsk Hydro, 1996) Canada (Schiff ,1994)

CF 4 C 2 F 6 CF 4 C 2 F 6 Cell Technology kg/tonne Al kg/tonne Al kg/tonne Al kg/tonne Al Side Worked Prebaked (SWPB) NAV NAV 1.19 a 0.067 a Horizontal Stud Søderberg (HSS) NAV NAV 0.82 a 0.14 a Vertical Stud Søderberg (VSS) 0.15-0.9 0.006-0.04 0.4 b NAV Centre Worked Prebaked (CWPB) 0.02-0.18 0.001-0,008 0.045-0.53 c 0.007-0.032 c

a Based on samples from one plant. b Samples from one plant-value has been adjusted to compensate for error.
c Based on sampling 5 plants. NAV = Not Available.

In Australia, all aluminium smelters use pre-baked cell technology. Emission factors from the Australian aluminium industry are reported to be 0.53 kg CF 4 /tonne Al, and 0.05 kg C 2 F 6 /tonne Al (Workbook, Australia, 1995). A study of Canadian aluminium plants found CF 4 emission factors to be between 0.045 and 1.2 kg. per tonne of aluminium produced (Unisearch, 1994). The emission factor for C 2 F 6 was between 0.007 and 0.14 kg per tonne. The Canadian study further subdivided the Søderberg and Prebaked technologies into two separate categories (Table 2-19). This subdivision narrows the emission range for each category. PFC emissions increase with frequency, intensity and duration of anode effects. The Norwegian study reported the frequency variation to be 0.03-0.24 AE per cell-day in Prebaked lines, and 1.0-2.76 AE per cell-day in Søderberg lines. Canadian data show AE frequency to vary between 0.2 and 2.6 per cell-day in all lines. Uncertainty in all measurements is relatively high (of the order of 50 per cent).
Estimated Emission Data A preliminary U.S. EPA study suggested a range of 0.01 to 1.2 kg of CF 4 per tonne of aluminium produced by any technology (U.S. EPA, 1994a). This range is an average based on measured emissions from aluminium smelters in the United States, Canada and Norway. These values may underestimate emissions from other aluminium producing regions. CICERO (1992) and, Khalil and Rasmussen (1985) have studied trends in atmospheric CF 4 . The studies made projections based on the assumption that all atmospheric CF 4 originates from aluminium production. Though data are subject to large uncertainties, both papers lead to the conclusion that the average emission rate from aluminium smelting is around 1 kg per tonne metal.The global emissions of PFCs to the atmosphere from all aluminium smelters was reestimated for 1995 (Harnisch and Borchers, 1995), and reported to be closer to 1.4 kg CF 4 /per tonne Al, and 0.2 kg C 2 F 6 /per tonne Al (Tabereaux, 1995). The distribution of four different cell technologies on a global scale is given in Table 2-20, together with estimated CF 4 emissions.

## I NDUSTRIAL 

## P ROCESSES

2.36 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-20 E STIMATED GLOBAL CF 4 EMISSIONS FROM SMELTERS WITH VARIOUS CELL TECHNOLOGIES Type of Cell Technology Per Cent of World Production kg CF 4 /tonne Al

Modern Prebaked 20 0.05 HS Søderberg 11 1.0
“Older” Prebaked 40 1.75 VS Søderberg 29 2.0 Weighted average for all plants world-wide 100 1.40

Source : Tabereaux, 1995.

Calculation of Emission Data Tabereaux (1995) has proposed a method for PFC emission calculation. He states that the generation of CF 4 in electrolysis cells follows Faraday’s Law (i.e., the quantity of gas generated depends on the flow of electrical current in the cell). At 100 per cent efficiency, 13.68 g of CF 4 is formed for every kiloampere-minute (kA min) duration of the anode effect. For example, CF 4 emissions for an aluminium smelter having an average percentage (p) of 16 per cent CF 4 in pot gas during anode effects (AE), 91 per cent current efficiency (CE) for aluminium production, 0.5 anode effects per pot day (AEF), and anode effect duration (AED) of 2.5 minutes can be calculated from:
Kg CF 4 / tonne Al = (kg CF 4 /kA min) / (kg Al/kA min) x (1000 kg/tonne) x (p/CE) x AEF x AED = 13.68 / 8.05) x (0.16 / 0.91) x (0.5) x (2.5) = 0.373



### 2.13.6.3 Emission Estimation Methodology for PFCs
Measurements
Since emissions of CF 4 and C 2 F 6 vary so significantly from one aluminium smelter to the next, depending on cell type and AE parameters, the estimations will be highly uncertain unless actual emission measurements have been made. Every effort should be made to obtain such data.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.37 Calculations It is recognised that measurements are both expensive and time-consuming. It may, however, be much easier to make a limited survey of AE frequency and duration at smelters. In such cases, it is recommended that specific CF 4 emissions for anode effects longer than 2 minutes are calculated as follows:
kg CF 4 /tonne Al = 1.698 x (p / CE) x AEF x AED

p = average fraction of CF 4 in the pot gas during anode effects Prebaked: p = 0.08 (8%) Søderberg: p = 0.04 (4%) CE = current efficiency expressed as a fraction, rather than a percentage AEF = number of anode effects per pot day
AED = anode effect duration in minutes
It is recommended that the default rate for C 2 F 6 emissions be 1/10 that of CF 4 . Estimations It is recommended that estimates are used only when no measured data exist. Specific emission factors should be chosen according to the type of technology used as shown in Tables 2-19 and 2-20 and applied to national primary aluminium production data for each technology. The following method may then be used to give an estimate of the annual CF 4 emissions from a smelter with a given cell technology.

CF 4 emission (kg) = EF (tech) (kg CF 4 /tonne Al) x pp (tech) (tonnes)

where:
EF (tech) = emission factor by technology (from Table 2-20)

pp (tech) = primary aluminium production by technology



### 2.13.7 Other Metal Production

2.13.7.1 Emissions of CO 2 This includes production of all non-ferrous metals except aluminium. The metals may be produced using carbon as reducing agents or by other methodologies. Whether carbon is emitted or not depends on the production process. Some ores are not reduced with carbon. Hence, CO 2 emissions from these processes are low. The general methodology suggested, where emissions are calculated from the consumption of reducing agents and the carbon content of ores, is recommended. An overview of production processes is given in Table 2-21. Some metals may be produced from alternative production methods.

## I NDUSTRIAL 

## P ROCESSES

2.38 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-21 P RODUCTION PROCESSES FOR SOME METALS Metal Main Ore(s) Carbon Reduction Electrolysis (without carbon) Other (non-CO 2 )
Chromium a FeCr 2 O 4 , PbCrO 4 x Copper Cu 2 S, CuFeS 2 , Cu 2 O, x x (SO 2 ) Gold Element x x Lead PbS x x (SO 2 ) Magnesium Carbonate x x Mercury HgS x (SO 2 ) Molybdenium MoS 2 x (SO 2 ) Nickel NiS, NiO x x x (SO 2 ) Platinum Element, PtS x Silicon b SiO 2 , Si-O-alkali x Silver Ag 2 S, element x Tin SnO 2 x Titanium TiO 2 , FeTiO 3 x c Tungsten WO 3 x Uranium U x O y x Zinc ZnS, ZnCO 3 x x x (SO 2 )

a See also ferroalloy production b See also ferroalloy production and carbide production
c Two step reduction process, involving first C + Cl 2 , then Mg Note: The appearance of (SO 2 ) in the final column indicates that the production process is a major world-wide source of SO 2 emissions.

In the case of magnesium and other metals in a carbonate ore, the carbon emitted from the ore should be taken into account in addition to the coke reducing agent.



### 2.13.8 SF 6 

### Used in Aluminium and Magnesium Foundries In the magnesium industry, SF 6 is used as a cover gas in foundries to prevent oxidation of molten magnesium. The Norwegian producer of magnesium has assessed whether SF 6 used as a cover gas reacts with other components in the furnaces. The results so far indicate that SF 6 is quite inert. For the time being it is therefore assumed that all SF 6 used as cover gas is emitted to the atmosphere. The consumption figures are therefore used as emission estimates.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.39 In the aluminium industry SF 6 is used as a cover gas only for special foundry products. As SF 6 is assumed to be inert, SF 6 emissions should equal consumption:

Emission of SF 6 = Consumption of SF 6 in magnesium and aluminium foundries



## 2.14 Pulp and Paper Industries

2.14.1 Overview Pulp and paper production has three major processing steps: pulping, bleaching and paper production

. The type of pulping and the amount of bleaching used depend on the nature of the feedstock and the desired quality of the end product

. Kraft (sulphate) pulping is the most widely used pulping process and is typically used to produce strong paper products

. The Kraft pulping process includes bleaching, chemical recovery and byproduct recovery. Sulphite pulping is another chemical pulping process

. It produces a weaker paper than some other types of pulping, but the pulp is less coloured, making it more suitable for printing, often with little bleaching

.


### 2 . 1 4 . 2 S i m p l e M e t h o d o l o g y f o r O z o n e Precursors and SO 2 Simpler methodologies are presented in the EMEP/CORINAIR Guidebook for three paper pulping processes;

• Kraft (SNAP 40602),

• Acid sulphite (SNAP 40603)

• Neutral sulphite semi-chemical process (SNAP 40604). Only data for the Kraft and Acid sulphite processes are available. In the Kraft pulping process sodium sulphide and sodium hydroxide are used to chemically dissolve the lignin that binds the cellulose fibres

. Emission factors are based on the production of air-dried pulp and are shown in Table 2-22 as suggested in the EMEP/CORINAIR Guidebook

. The emissions of SO 2 may be lower in new mills than the older ones (U.S. EPA 1995).

## I NDUSTRIAL 

## P ROCESSES

2.40 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-22 N ON - COMBUSTION EMISSION FACTORS FOR PAPER AND PULP PRODUCTION - K RAFT PULPING ( KG / TONNE DRIED PULP )
Pollutant Emission Factor (Default) Emission Factor (Range)
SO 2 7 0.005-10
NO x 1.5 0.017-1.5
VOC a 3.7 0.1-4.9
CO b 5.6 NAV

a Note, VOC is defined as the total gaseous non-methane organic compounds which include sulphur compounds. b Ref: U.S. EPA 1995. NAV = Not Available

The acid sulphite pulping process is similar to the Kraft process except that a sulphurous acid solution is used to dissolve the lignin in the wood. This solution is buffered by the use of bisulphide of sodium, magnesium, calcium or ammonium. SO 2 is considered to be the major pollutant. There are at least four types of processes: ammonium based (NH 3 ), calcium based (Ca), magnesium based (M g O) and sodium based (Na) (U.S. EPA, 1995). Emissions factors from U.S. EPA, 1995 are given in Table 2-23.

T ABLE 2-23 N ON COMBUSTION EMISSIONS FROM PAPER AND PULP PRODUCTION - A CID SULPHITE PULPING ( KG / TONNE DRIED PULP )
Pollutant Type of Process Emission Factor (Default) Emission Factor (Range)
SO 2 NH 3 , Ca, MgO and Na 30 8-50



### 2 . 1 4 . 3 D e t a i l e d M e t h o d o l o g y f o r O z o n e Precursors and SO 2 The preferred methodology is to use continuous measurements data which may be available for SO 2 and NO x . This is only feasible in modern plants where the number of measure points to be monitored is limited

. Detailed emission factors related to the various processes are given in the EMEP/CORINAIR Guidebook.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.41 

## 2.15 Food and Drink

2.15.1 Alcoholic Beverages NMVOCs are produced during the processing of cereals and fruits in preparation for the fermentation processes The activity rate is the total annual production. The emission factors given in the EMEP/CORINAIR Guidebook (SNAP 40606-40608) are shown in Table 2-24.

T ABLE 2-24 E MISSION FACTORS FOR ALCOHOLIC BEVERAGE PRODUCTION ( KG / HL BEVERAGE )
Beverage Emission Factor
Wine 0.08
Red wine 0.08
White wine 0.035
Beer 0.035 Spirits (unspecified) 15 Malt whiskey 15 Grain whiskey 7.5 Brandy 3.5

The emission factors and sources are derived for Europe; there may be different processes and emission factors in other parts of the world.



### 2.15.2 Bread Making and Other Food The relevant precursor gas emitted during food production (SNAP 40605) is NMVOC. Emissions from processes not included are vegetable oil extraction (SNAP 60404), tobacco products and alcoholic beverages (see Section 2.15.1). Emissions are included from all processes in the food chain which occur after the slaughtering of animals or harvesting of crops. Food production is divided into seven categories each with its own emission factor. The emission factors given in the EMEP/CORINAIR Guidebook are shown in Table 2-25. The activity rate is the total annual production of food. The emission factors and sources are derived for Europe; there may be different processes and emission factors in other parts of the world.

## I NDUSTRIAL 

## P ROCESSES

2.42 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 2-25 E MISSION FACTORS FOR BREAD AND OTHER FOOD PRODUCTION ( KG / TONNE )

Food Production Process Emission Factor Meat, fish and poultry 0.3 Sugar 10 Margarine and solid cooking fats 10
Cakes, biscuits and breakfast cereals 1
Bread 8
Animal Feed 1 Coffee roasting 0.55



## 2 . 1 6 E m i s s i on s Rel a t e d t o P r od u c t i on of Halocarbons and Sulphur Hexafluoride (HFCs, PFCs and SF 6 

## )

2.16.1 By-product Emissions Chemical by-products of industrial processes, substances which are different from the desired end-product, may be released into the atmosphere. It is well known that HFC-23 is produced along with HCFC-22 and it is estimated that the HFC-23 released from this source is currently equivalent to 4 per cent of the production of HCFC-22 (U.S. EPA, 1994b) assuming no abatement measures. In the Tier 1 methodology (Section 2.17.3), this factor, or a similar number derived for the particular country's circumstances, can be used to estimate national emissions of HFC-23 from the total national HCFC-22 production (for both potentially dispersive and feedstock end-uses). Problems with collecting specific component data can be circumvented by providing a single number for total emissions of HFC-23.

By-product Emissions (tonnes) = By-product Factor (tonnes/tonne) x Total HCFC-22 Production (tonnes)

For the Tier 2 methodology (Section 2.17.4), a potentially more accurate estimate is the sum of factory specific emissions determined using standard methods to estimate the composition and flowrate of gas streams vented to atmosphere. In this case:

By-product Emissions = 

## ∑ i 

## ∑ j 

# ∫ t 

### f ijCij

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.43 where: the sum over all i plants, over all j streams in each plant of the emitted flows f and concentrations c is integrated over time (t). Other by-product emissions of HFCs, PFCs and other greenhouse gases from chemical production processes should be identified and treated in the same way.



### 2.16.2 Fugitive Emissions Fugitive emissions of a chemical occur during the production and distribution of a chemical. In this chapter, fugitive emissions associated with use are not addressed specifically, being counted in the emissions related to consumption (see Section 2.17). In the case of fluorocarbon processes, fugitive emissions have been estimated to be approximately 0.5 per cent of the total production of each compound (UNEP, 1994). In the Tier 1 methodology, this factor, or a similar number derived for the particular country's circumstances, can be used to estimate national fugitive emissions of individual HFCs and PFCs associated with national production. Problems with collecting specific component data can be circumvented by providing a single number for total emissions of each HFC and PFC.

Fugitive Emissions (tonnes) = Fugitive Release Factor (tonnes/tonne) x Individual HFC or PFC Production (tonnes)

For a Tier 2 methodology, a potentially more accurate estimate is the sum of factory specific emissions determined using standard methods to estimate the composition and flowrate of gas streams vented to atmosphere. In this case:

Fugitive Emissions = 

## ∑ i 

## ∑ j 

# ∫ t 

### f ijCij

where: the sum over all i plants, over all j streams in each plant of the emitted flows f and concentrations c integrated over time (t).



## 2 . 1 7 E m i s s i on s Rel a t e d t o C on s u m p t i on of Halocarbons and Sulphur Hexafluoride (HFCs, PFCs, and SF 6 

## )

2.17.1 Overview Partially fluorinated hydrocarbons (HFCs), perfluorinated hydrocarbons (PFCs), and sulphur hexafluoride (SF 6 ) are serving as alternatives to ozone depleting substances (ODS) being phased out under the Montreal Protocol. Current and expected application areas of HFCs and PFCs include (Kroeze, 1995; U.S. EPA, 1992b):

## I NDUSTRIAL 

## P ROCESSES

2.44 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual - refrigeration and air conditioning - fire suppression and explosion protection
- aerosols - solvent cleaning - foam blowing - other applications 5 Primary uses of SF 6 include: - gas insulated switch gear and circuit breakers - fire suppression and explosion protection - other applications 6 Partially and fully fluorinated hydrocarbons (HFCs and PFCs) are not controlled by the Montreal Protocol because they do not contribute to depletion of the stratospheric ozone layer.
HFCs are chemicals containing only hydrogen, carbon, and fluorine. Prior to the Montreal Protocol and the phase-out of various ozone depleting substances (ODS), theonly HFCs produced were HFC-152a, which is a component of the refrigerant blend R500, and HFC-23, a low temperature refrigerant which is a by-product of HCFC-22 7 production. HFC-134a entered production in 1991 and a variety of other HFCs are now being produced (Enquete Commission, 1994).PFCs are chemicals containing only carbon and fluorine. PFCs have been produced commercially for 30 years, primarily for use as cooling/heating agents in specialised market segments and in vapour phase reflow soldering and electronic safety testing (Kroeze, 1995). Like HFC emissions, PFC emissions result from two sources; emissions from commercial use of PFCs and emissions as by-products of industrial processes. PFCs are anthropogenic compounds; no natural sources have been found, though a small, but as yet unidentified, natural source of one PFC is suspected (Abrahamson, 1992).
SF 6 is a particularly potent GHG with a 100-year GWP of 23,900 and an estimated lifetime of about 3200 years (IPCC, 1996)(Table 2-26). The chemicals (HFCs, PFCs, SF 6 ) are of concern, however, because they have high global warming potentials and long atmospheric residence times. Table 2-26 gives an overview over the most important HFCs and PFCs (U.S. EPA, 1992b; UNEP, 1994; Kroeze, 1995), including application area and GWP relative to CO 2 (100 year integration time). The various HFCs and PFCs have very different strengths as GHGs. PFCs have particularly high GWPs. The consumption pattern with respect to the individual gases must be known, therefore, or estimated with reasonable accuracy, to achieve useful estimates for the contribution to global warming from emission of these groups of chemicals.

5 HFCs and PFCs may be used in sterilisation equipment, for tobacco expansion applications, and as solvents in the manufacture of adhesives, coating and inks.

6 SF 6 may be used as an insulating medium, tracer, in leak detectors, and in various electronic applications. Aluminium and magnesium foundries are also major users of SF 6 , but the emissions associated with these industries are covered in Section 2.13.8

7 HCFCs - hydrochlorofluorocarbons.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.45 As CFCs, halons, carbon tetrachloride, methyl chloroform, and, ultimately, HCFCs are phased out, HFCs are likely be widely used as replacements. PFCs may be used to a limited extent. Even though up to 75 per cent of current application of CFC may be covered by different technologies in the future (McFarland and Kaye, 1992), HFC use is expected to grow substantially.
NF 3 is another gas which is likely to contribute to global warming. It may be used for chip etching (Cook, 1995) but is not included here.

T ABLE 2-26 P OTENTIAL A PPLICATION AREAS AND GLOBAL WARMING POTENTIALS (GWP S ) FOR HFC S , PFC S , AND SF 6
Chemical GWP a Refrigeration and Air Conditioning Fire Suppression and Explosion Protection Aerosols Solvent Cleaning Foam Blowing Other Applications b

HFC-23 11700 x x
HFC-32 650 x
HFC-125 2800 x x x x x
HFC-134a 1300 x x x x x
HFC-143a 3800 x x
HFC-152a 140 x x x
HFC-227ea 2900 x x x x
HFC-236fa 6300 x x
HFC-245ca 560 x x
HFC-356 x
HFC-43-10 x
PFC-116 9200 x
PFC-218 7000 x
PFC-410 7000 x
PFC-614 x x
Other PFCs c x
SF 6 d 23900 x x

a 100 year time horizon (IPCC, 1996). b Other applications include sterilisation equipment, tobacco expansion applications, and as solvents in the manufacture of adhesive coatings and inks (Kroeze, 1995; U.S. EPA, 1992b).

c E.g., PFC-512, PFC-612, PFC-716, PFC-819. d Gas insulated switchgear and circuit breakers.

## I NDUSTRIAL 

## P ROCESSES

2.46 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2 . 1 7 . 2 G e n e r a l M e t h o d o l o g y Emissions from industrial processes can be estimated in two ways; as potential emissions, Tier 1, (a and b), and as actual emissions, Tier 2. Potential emissions of a certain chemical are equal to the amount of virgin chemical consumed in the country minus the amount of chemical recovered for destruction or export in the year of consideration. All chemicals consumed will eventually be emitted to the atmosphere over time if not destroyed 8 , and in the long term (e.g., 50 yrs), potential emissions will equal actual emissions. However, the method does not take into account accumulation or possible release 9 of chemical in various products and equipment, which means over the short term (e.g., 10-15 yrs) estimates may become very inaccurate. Since accumulation is thought to be the dominant process at the present time, potential emission calculations will strongly over estimate emissions. The error is minimised when enough time has passed for HFC/PFC-containing equipment and products to begin to be retired. However, as long as emissions lag behind consumption and consumption continues to grow, the overestimation will persist. The error is zero only if there is no delay in emissions or if the consumption growth rate is zero for a long period of time. Actual emission estimates take into account the time lag between consumption and emission, which may be considerable in some application areas, e.g., closed cell foams, refrigeration and fire extinguishing equipment. Time lag results from the fact that a chemical is placed in new products and then slowly leaks out over time. A household refrigerator, for example, emits only small amounts of refrigerant through leakage and emissions during servicing throughout its lifetime and most of its charge is not released until its disposal, many years after production. The amount of a chemical escaping to the atmosphere in a given year will only be similar to the quantity consumed in a static situation with respect to chemical usage pattern, market development, system or product design and tightness, servicing and recovery practices, etc. This is very different from the current situation. Since countries are only beginning to use and produce the chemicals, only a small fraction of products with HFCs/PFCs are being stored in the market. Until a more stationary situation is established, which may take 15-20 years for industrialised countries and an additional 10 years for developing countries, the time lag between consumption and emission has to be taken into account to achieve reasonably correct estimates for annual emissions. Hence, actual emissions estimates are the most accurate with respect to emissions in individual years, provided that the necessary information is available for their calculation. If essential data are not available, the potential emission calculations provide a more simple approach for reasonable emission estimates. The following procedures described for HFCs/PFCs are applicable for SF 6 as well.

8 The destruction of fluorocarbons could be costly but there are several destruction processes recommended by the Parties to the Montreal Protocol: liquid injection incineration; reactor cracking; gaseous/fume oxidation; rotary kiln incinerators; cement kilns; plasma destruction; municipal solid waste incinerators (foams only).

9 If non-halocarbon technology takes over market shares.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.47 

### 2.17.3 Tier 1: Basic Method

2.17.3.1 Overview Potential emission calculations are regarded as the basic methodology for HFC and PFC emission estimates, which any country should apply. However, if relevant information is available, it is recommended that emissions are reported according to the Tier 2 methodology in Section 2.17.4. Since net consumption of a chemical equals production plus imports minus exports, the calculation formula for the basic method (Tier 1) is as follows:

Potential Emissions = Production + Imports - Exports - Destruction

Although destruction of HFCs and PFCs is currently not practised, and may be technically difficult (U.S. EPA, 1995), it should be included as a future option to reduce emissions. By-product emissions during HFC/PFC production and fugitive emissions related to production and distribution have to be calculated separately, as described in Section 2.16. Production refers to production of new chemical. Reprocessing of recovered fluid should not be included. Imports and exports include bulk chemicals and may or may not include the quantity of chemical contained in products, such as refrigerators, air-conditioners, packaging materials, insulating foams, fire extinguishers etc. There are two versions of Tier 1 (a and b) depending upon whether HFCs/PFCs in products are taken into account. In Tier 1a, chemicals contained in products are not considered. In Tier 1b, chemicals contained in products are considered. The reason for two versions is that it is expected that there may be difficulties in many countries with the availability of data regarding imports and exports of HFCs/PFCs in products, at least in the short term. The Tier 1b methodology is preferred if relevant data are available. Irrespective of the Tier 1 methodology chosen, emissions with respect to individual HFCs and PFCs have to be reported. Information on the practical use of the various commercial types of HFC/PFC refrigerants, blowing agents, solvents, etc. will be required. Many of these products are mixtures of two to four HFCs/PFCs, and the composition of fluids for similar purposes may vary according to individual formulas developed by the different chemical companies.



### 2.17.3.2 Tier Ia Quantities of HFCs/PFCs contained in various products imported into or exported from a country may be difficult to estimate. In Tier 1a, only chemicals imported or exported in bulk are considered in the calculation of potential emissions, which is a similar approach presently used to report Ozone Depleting Substances (ODS) under the Montreal Protocol. The following definitions apply:

Imports = Imported HFC/PFC in bulk Exports = Exported HFC/PFC in bulk

## I NDUSTRIAL 

## P ROCESSES

2.48 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The application of Tier 1a may lead to underestimation or overestimation of potential emissions, depending on whether the majority of HFC/PFC containing products is being imported or exported. Data on production and exports of chemicals in bulk should be available from chemical companies. Information on imports of chemicals in bulk may be available from customs services. National environmental protection authorities may keep records of HFCs/PFCs destroyed, if any.
Potential emission data for each individual chemical should be calculated according to the scheme in Table 2-27:

T ABLE 2-27 C ALCULATION SCHEME FOR POTENTIAL EMISSIONS ACCORDING TO T IER 1a
Reporting year: Type of chemical (e.g., HFC-134a):
Production of chemical tonnes + Import of chemical in bulk tonnes - Export of chemical in bulk tonnes
- Destruction of chemical tonnes = Sum (potential emission of chemical) tonnes
Emissions related to production and distribution of HFCs/PFCs have to be taken into account as described in Section 2.16.2.



### 2.17.3.3 Tier 1b Tier 1b is an extension of Tier 1a and includes HFCs/PFCs contained in various products which are imported and exported. The following definitions then apply:

Imports = Imported chemical in bulk + quantity of chemical imported in HFC/PFC containing products

Exports = Exported chemical in bulk + quantity of chemical exported in HFC/PFC containing products

Data on production and exports of HFCs/PFCs in bulk should be available from the chemical companies to their national governments. Information on imports of bulk chemicals should be available from customs services, as well as imports and exports of products and equipment containing HFCs or PFCs. National environmental protection authorities may keep records of HFCs/PFCs destroyed. To calculate the potential emissions according to Tier 1b, the calculation scheme in Table 2-27 has to be extended to include the import and export of chemicals in products. Table 2-28 demonstrates a possible set-up for calculation of emissions from exports/imports and the results should be added to the emissions calculated using Table 2-27. In Table 2-28, HFC-xxx is used as an example to demonstrate the procedure, which in practice will have to be performed for individual HFCs and PFCs, and with SF 6

.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.49 T ABLE 2-28 A DDITIONAL CALCULATIONS FOR ESTIMATING POTENTIAL EMISSIONS ACCORDING TO T IER 1 B Refrigeration

G HFC

- xxx = G(Unit i) x n (Unit i) x F HFC

- xxx (Unit i) + - - - - - + G(Unit m) x n (Unit m) x F HFC

- xxx (Unit m)

where:
G HFC- xxx = total import (export) of HFC-xxx in precharged refrigeration units 10 G(Unit i) = refrigerant charge in a refrigeration unit of type "i" (i = i → m) n(Unit i) = number of refrigeration units of type "i" imported (exported)
F HFC- xxx = fraction of component HFC-xxx 11 in the refrigerant (mixture) of a unit of type "i" Foam products 12

G HFC

- xxx = V(Foam i) x J HFC

- xxx (Foam i) + - - - - - - - + V(Foam m) x J HFC

- xxx (Foam m)

where:
G HFC

- xxx = total import (export) of HFC-xxx in foams (flexible and rigid) V(Foam i) = volume of foam of type "i" imported (exported) (i = i → m) J HFC- xxx = remaining amount of blowing agent HFC-xxx per volume unit of foam of type "i "

10 "Refrigeration units" may be refrigerators, ice machines, AC window units, splitunits, chillers etc. Typical charge ranges for various types of equipment are given in Section 2.17.4.2.

11 Many refrigeration units will contain HFC/PFC-mixtures. The fraction of each chemical (HFC-xxx) has to be considered.

12 Include insulating and non-insulating foams in a variety of products, like refrigerators, insulation panels, pour-in-place sprays, car seats, furniture, bedding, packaging material etc.

## I NDUSTRIAL 

## P ROCESSES

2.50 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Fire extinguishers

G HFC

- xxx = G (Unit i) x n (Unit i) x F HFC

- xxx (Unit i) + - - - - + G (Unit m) x n (Unit m) x F HFC

- xxx (Unit m)

where:
G HFC

- xxx = total import (export) of HFC-xxx in precharged fire extinguishers G(Unit i) = charge of fire extinguishing agent in a fire extinguishing unit of type "i" (i = 1 → m) n(Unit i) = number of fire extinguishing units of type "i" imported (exported)

F HFC-xxx = fraction of component HFC-xxx 13 in the fire extinguishing agent of a unit of type "i"

Solvents

G HFC

- xxx = G (Solvent i) x F HFC

- xxx (Solvent i) + - - - - - - - + G (Solvent m) x F HFC

- xxx (Solvent m)

where:
G HFC- xxx = total import (export) of HFC-xxx in solvents

G(Solvent i) = quantity of solvent of type "i" imported (exported) (i = i → m)
F HFC

- xxx = fraction of component HFC-xxx 14 in solvent of type "i"

Aerosols

G HFC- xxx = G(Can i) x n (Can i) + - - - - - - - + G(Can m) x n (Can m)

where:
G HFC

- xxx = total import (export) of HFC-xxx in aerosol cans G(Can i) = charge of HFC-xxx propellant in an aerosol can of type "i" (i = i → m) n(Can i) = number of aerosol cans of type "i" imported (exported)

13 Most fire extinguishing units will contain HFC/PFC-mixtures. The fraction of each chemical (HFC-xxx) has to be considered.

14 Solvents will normally not be pure HFCs or PFCs. The fraction of the HFC/PFC in consideration (HFC-xxx) has to be considered.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.51 

### 2.17.4 Tier 2: Advanced Method

2.17.4.1 Overview
The advanced method, Tier 2, contains actual emission calculations for each individual chemical, comparable with methods currently applied by AFEAS for CFCs and HCFCs (Gamlen et al., 1986; Fisher and Midgley, 1993; AFEAS, 1995). This is the preferred method if input data are available. Some countries may have the relevant information available already to apply the Tier 2 methodology. However, countries that do not are recommended to establish routines to report HFC/PFC emissions according to Tier 2. The Tier 2 methodology: a) calculates or estimates the consumption of each individual HFC and PFC chemical at a rather detailed level, e.g., refrigerators, other stationary refrigeration/AC equipment, soft foam, hard foam etc., to establish the volume basis for emission calculations. b) estimates emissions on the basis of the consumption distribution from (a), and emission characteristics related to various processes and equipment, also taking current service and recovery practices into account. Table 2-29 gives examples of current HFC/PFC use distribution among various application areas in certain countries. Since HFCs and PFCs have only recently entered the market, the relative size of each area will change over time and will have to be updated. This information may allow countries with similar practices to those in Table 2-29 to make first order estimates for their own HFC/PFC consumption and distribution.

T ABLE 2-29 E XAMPLE DISTRIBUTION OF HFC/PFC USE BY APPLICATION AREA (1994)
Country Refrigeration Air Conditioning Foam Blowing Solvent Fire Extinguishing Aerosol Propellant Other Applications

Norway
Sweden
United Kingdom a 99%
90%
76% <1%
5%
12% 0%
0%
0% <1%
0%
7% 0%
5%
5% 0%
0%
0%

a March Consulting Group (1996), UK Use and Emissions of Selected Halocarbons , A Study for the UK Department of Environment.

Any given application area may employ several types of HFC/PFC fluid. Consumption figures should be collected or estimated and the type of HFC/PFC used should be identified. Nevertheless, real emission data for a given year will never be exactly known, irrespective of the refinement of the estimation methods. Cross checking of integrated emission figures against real net consumption of HFC/PFC, together with judgement of banking over the same period of time must be performed at regular intervals, and the input factors have to be adjusted to achieve agreement over time. Examples of how the Tier 2 methodology may be applied are given in the remainder of this chapter.

## I NDUSTRIAL 

## P ROCESSES

2.52 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2 . 1 7 . 4 . 2 E s t i m a t i o n O f E m i s s i o n s O f H F C s And PFCs From Use In Refrigeration And Air Conditioning Equipment
Overview HFCs and PFCs are potential replacements to the use of CFCs and HCFCs inrefrigeration and air conditioning equipment. A wide array of such equipment is used globally. For the purposes of emission estimation, refrigeration and air-conditioning systems are classified into three categories, according to emission characteristics:

• Household refrigerators and freezers;

• Other stationary refrigeration and air conditioning equipment, including: - cold storage warehouses; - retail food refrigeration; - industrial process refrigeration; - commercial and industrial appliances such as refrigerated vending machines, ice machines, dehumidifiers, and water coolers; - refrigerated transport including trucks, trains, and ships with refrigerated compartments; - commercial and residential air conditioning including chillers, heat pumps, window air conditioners, centralised air conditioners.

• Mobile air conditioners used to cool the passenger compartment of automobiles, trucks, buses, and trains. HFC-134a is the primary fluorocarbon substitute for CFC-12 in many refrigeration and air-conditioning applications including refrigerators, chillers, and mobile air conditioners. Other HFCs may also be used in refrigeration applications, particularly as components of blends. These include HFC-23, HFC-32, HFC-125, HFC-143a, and HFC-152a (Du Pont, 1994; Fay, 1995). PFC-218 is used as a component in refrigerant blends from (at least) one manufacturer. PFC-116 may be used in a blend as a substitute for R-503. Inaddition, a significant portion of the refrigerant market may be taken over by nonhalocarbon technologies (McFarland & Kay, 1992).

Calculation methods Gas emissions from refrigeration and air conditioning systems result from:

• losses during system erection/assembly 15 ;

• emissions from the stock of existing systems (small leakages, breakdowns, venting at service);

• venting of refrigerant at system disposal. Methods for estimating average emission rates for the above-mentioned sectors are outlined below.

15 e.g., losses from using HFC/PFC as tracer gas for checking leak tightness, losses in relation to system development and testing etc.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.53 The quantity of refrigerant emitted during system assembly is related to the amount charged by the following empirical formula:

E QUATION 1 E assembly , t= E charged , t • (k/100)

where:
E assembly,t = emissions during system manufacture/assembly in year t
E charged,t = the amount of refrigerant charged into new systems in year t k = assembly losses in per cent of the amount charged

The amount charged (E charged
, t ) should include all systems which are charged in the country, including those which are made for export. Systems that are imported precharged should not be considered. Typical range for the emission factor k is 2-5 per cent (Radian Corp., 1986). For some types of unit production, alternative leak detection methods may be used. Assembly losses may then be less than indicated here, and in some cases may be negligible. Annual leakage from the stock , including venting during service, is commonly expressed in per cent of total amount of “banked” refrigerant in the existing stock of systems. Emission rates related to current system design and service practices are available from half a century of CFC and HCFC refrigeration. The following calculation formula applies:

E QUATION 2 E operation , t= E stock , t • (x/100)

where:
E operation , t = amount of HFC/PFC emitted during system operation in year t
E stock
, t = amount of HFC/PFC stocked in existing systems in year t x = annual leakage rate in per cent of total HFC/PFC charge in the stock, per cent.

In calculating the refrigerant “bank” (E stock
, t ) all systems in operation in the country (home-made and imported) have to be considered. Examples of typical leakage rates (x) for various types of equipment describing the respective refrigeration sectors are given later in this section. The amount of refrigerant released from scrapped systems depends on the amount of refrigerant left at the time of disposal, and the portion recovered. Normally, less refrigerant is left than was originally charged. From a technical point of view, the major part of the remaining fluid can be recovered. To estimate emissions at system disposal, the following calculation formula is applicable:

## I NDUSTRIAL 

## P ROCESSES

2.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual E QUATION 3 

### E disposal , t = 

### Ei charge (t - n) • (y/100) • (100 - z )/100

or 

### E disposal , t= 

### Ei charge (t - n) • 

### Q

where:
E disposal
, t = amount of HFC/PFC emitted at system disposal in year t
Ei charge (t-n ) = amount of HFC/PFC initially charged into new systems installed in year (t-n) n = average equipment lifetime, years y = amount of HFC/PFC in systems at time of disposal in per cent of initial charge, per cent z = amount of HFC/PFC recovered in per cent of actual charge (“recovery efficiency”), per cent Q = amount of HFC/PFC emitted at system disposal in per cent of the quantity of chemical originally charged into the system, per cent Q=y (100-z)/100

In estimating the amount of refrigerant initially charged into the systems (E i charged, (t-n) ), both systems charged in the country (for home market) and systems imported precharged should be taken into account. First charge of systems made for export should not be considered. Values applicable to n, y and z are discussed later in this section when dealing with the respective sectors. Total emissions in year t will then be found as the sum of emissions at assembly, during operational life and at disposal:

E QUATION 4 

### E total , t = 

### E assembly , t + 

### E operation , t + 

### E disposal, t

Estimating input data for actual emission calculations To provide a good basis for emission calculations according to Tier 2, it appears that much detailed information (Equations 1-3) about HFC/PFC use is required. The most important information is reliable estimates for the overall consumption and consumption distribution. In principle, there are two different approaches to determine consumption figures. One is to estimate the amounts and types of each chemical from the number of refrigerating and air conditioning systems in question ("bottom-up approach"). Alternatively, one may start with more general registrations or estimates of HFC/PFC use for refrigeration purposes, and distribute these figures among the various sectors according to the relative magnitude of each sector ("top-down approach"). A reasonably good distribution key has to be developed also with respect to the individual types of

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.55 HFCs/PFCs. Refrigeration and air conditioning organisations in the country may possess useful data with respect to the information required. A bottom-up approach may work well when estimating emissions from refrigerating units of similar type and design, the number of which may be large but known (such as refrigerators, AC units, mobile air conditioners etc.). The top-down approach is more general, and probably more practical for systems which are erected and charged at site, and for production of systems with large variations in purpose, design and charge. This approach is less likely to under-estimate emissions, since it is based on total HFC/PFC consumption figures. It may be practicable to apply elements from both approaches. However, one has to be cautious about double counting. Examples demonstrating the top-down approach are provided in Table 2-30, which shows distribution of individual HFCs/PFCs within the same sectors.

T ABLE 2-30 D ISTRIBUTION OF INDIVIDUAL HFC S /PFC S IN REFRIGERATION , I N N ORWAY AND S WEDEN , IN 1994

HFC-23 HFC-32 HFC-125 HFC-134 A HFC-143 A HFC-152 A PFC-218

Household Norway 0 0 0 100% 0 0 0 refrigeration Sweden 0 0 0 100% 0 0 0
Other stationary Norway <1% <1% 19% 71% 7% 2% <1%
equipment Sweden <1% <1% <5% 95% <5% <1% <1%

Mobile air Norway 0 0 0 100% 0 0 0 conditioning Sweden 0 0 0 100% 0 0 0

Estimated amounts of the various "base chemicals" going into each specified sector may follow from total quantities HFCs/PFCs consumed and the distribution keys laid down in Table 2-29. Since HFCs and PFCs have only recently entered the market, consumption figures for the various chemicals relative to each other may change somewhat over time. These figures may be useful for countries with similar practices as those shown in the table, to make first estimates for their own HFC/PFC consumption distribution in refrigeration.
Estimating emissions from household refrigeration
Information for household refrigerators and freezers is very reliable, and emission rates in the form of leakages and service losses are very low. Average lifetime is expected to be 15 years (n in Equation 3 is equal to 15). Even though a refrigerator is sensitive with respect to low charge, it is estimated that only 1 per cent of the units in operation fail each year due to loss of charge (U.S. EPA, 1992a), resulting in an average refrigerant loss per year of 1 per cent of the total quantity banked in the stock. A certain, but small amount of the charge of those refrigerators reaching the average lifetime will have escaped during operation. The remaining charge is emitted upon disposal of the refrigerator (Kroeze 1995; U.S. EPA 1992a). This was common practice until recently. Over the past 2-4 years, recovery and recycling practices have been

## I NDUSTRIAL 

## P ROCESSES

2.56 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual established in many countries to minimise CFC emission. Similar practices may be applied to reduce HFC/PFC emission as well. In the industrialised world, the overwhelming majority of household refrigerators are not serviced during their lifetime (U.S. EPA, 1992a). However, recharging is very common in many developing countries, and 2 to 3 charges during the lifetime of a fridge may be typical. From this it may be deduced that the average failure rate is higher in these countries, and the physical lifetime of a refrigerator may be longer. Emission of HFCs/PFCs during assembly, operation and disposal of household refrigerators and freezers in the year t are to be calculated according to Equations 1-4. Emission factors related to system assembly, operation and disposal (k, x and Q respectively) should be chosen according to each country's experience. Example of common range of variation for k in the past is given under Calculation Methods earlier in this section. It is believed that k for household refrigerators and freezers belongs to the lower part of the range (2 per cent). In those cases where trace gases other than the refrigerant itself are used for leak detection, e.g., helium, k becomes practically zero. American experience with respect to annual leakage rate, as referenced above, indicates that a typical value for x in developed countries may be 1 per cent. The remaining charge after 15 years (y in Equation 2) is not well known, but is believed to be in the order of 90 per cent. If recovery and recycling are not practised (z in Equation 3 is equal to zero), Q becomes equal to 90 per cent. However, if one allowed for the recovery and recycling which is possible now, Q could decrease to 40 per cent. The practical recovery rate (z) for refrigerant in refrigerators is just below 50 per cent (McCulloch, 1994). Kroeze indicates a range of recovery of 30-60 per cent (Kroeze, 1995), which is consistent with the figure given by McCulloch (1994). Reasonable estimates for the number of refrigerators and freezers manufactured in a country are generally available, as well as the number of imported and exported units and the total stock. The amount of refrigerant banked in the stock can be calculated by multiplying the number of units with average charge sizes. American refrigerators have an average charge of 170 grams, while the corresponding figures for Europe and Japan are 140 grams and 137 grams respectively (Fischer et al., 1991; Fujimoto, 1991). Refrigerators made in developing countries may have different (probably larger) average charges than those values indicated above.
Emissions from Other Stationary Refrigeration and Air Conditioning Equipment Other stationary refrigeration and air conditioning equipment is not usually hermetically sealed and therefore has higher leak rates and requires servicing on a regular basis to replace refrigerant leaked over time. In addition, these units typically have much larger charge sizes than household refrigeration equipment. Emissions of HFCs/PFCs during assembly, operation and disposal of other stationary refrigeration and air conditioning equipment in the year t are to be calculated according to Equations 1 to 4. Emission factors related to system assembly, operation and disposal (k, x and Q respectively) should be chosen according to each country's experience. Average system lifetime is expected to be 15 years (n in Equation 3 is equal to 15). An example of a common range of historical variation for k is given under Calculation Methods earlier in this section. It is believed that k for factory built systems (unit

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.57 systems) belongs to the lower part of the range (2-3 per cent), while k for systems erected and charged at site are higher (4-5 per cent). Various references (Enquete Commission, 1994; U.S. EPA, 1993; McCulloch, 1994) seem to agree that leakage emissions from other stationary equipment are approximately 17 per cent on average (x = 17%). Since all systems leak, the average charge at the point of disposal will be less than the amount initially charged into the systems (and after topping up at service). However, exact figures are not known. If country specific data are not available, 90 per cent of that initially charged may be assumed for calculation purposes (y in Equation 2 represents 90 per cent). The charge remaining in the equipment upon retirement is normally vented (z in Equation 3 is equal to zero), which means that Q equals 90 per cent. Emissions at assembly, during operation, and at disposal may be reduced through the implementation of future actions designed to reduce leakage and disposal emissions. Specifically, leakage rates in other stationary refrigeration and air conditioning equipment can be reduced through the use of improved valves and fittings that minimise such emissions, and emissions that occur upon service and disposal of equipment can be reduced through the use of recovery or recycling technologies. Assuming the implementation of these technologies, leakage emissions can be reduced to as low as 3 per cent (x = 3%) per year and emissions upon retirement of equipment can be reduced by as much as 80 per cent (z = 80%, Q = 18%). Refrigerant charge may vary over a wide range, dependent upon system size and design. The following range may indicate orders of magnitude (U.S. EPA, 1993):

• Residential air conditioning: 2 to 3 kg

• Transport Refrigeration: 8 kg

• Retail Food Refrigeration: 10 to 230 kg

• Chillers: 75 to 900 kg

• Industrial Process Refrigeration: 340 to 9100 kg

• Commercial and industrial appliances: 0.10 to 0.50 kg To apply the bottom-up approach, reliable average values for system charge sizes valid for each country will be required to develop useful estimates.
Emissions from Mobile Air Conditioning (MAC) Car air conditioners are relatively leaky systems that require frequent servicing. Estimates for current applications are that approximately one-third of the charge is leaked each year (McCulloch, 1994), and that the remaining charge in equipment is emitted upon its retirement. Car air conditioners have typical lifetimes of 11 years (small cars) to 15 years (trucks) (UNEP, 1989). On average, a lifetime of 12 years may be assumed (n in Equation 3 is equal to 12). Emission of HFCs/PFCs during assembly, operation and disposal of mobile air conditioners in the year t are to be calculated according to Equations 1-4. Emission factors related to system assembly, operation and disposal (k, x and Q respectively) should be chosen according to each country's experience.
New HFC systems may have less leakage, e.g., 10-20 per cent (x = 10-20%) (Arai, personal communication, 1996).

## I NDUSTRIAL 

## P ROCESSES

2.58 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Example of common range of variation for k in the past is given under Calculation Methods earlier in this section. It is believed that k for MACs belongs to the upper part of the range (4-5 per cent). With respect to x, a typical value according to past CFC/HCFC experience, as referenced above, is, about one third (x = 30%). Since MACs are generally more leaky than stationary systems, average charge at the point of disposal will most probably be less than typical values for stationary systems. However, exact figures are not known. If country specific data are not available, 75 per cent of that initially charged may be assumed for calculation purposes (y in Equation 2 is equal to 75 per cent). In most cases, the refrigerant is vented at disposal (z in Equation 3 is zero), which means that Q equals 75 per cent. With improved system components, such as improved seals, fittings, and hosing, and the use of recycling at service, emissions from MACs during normal use (x) should eventually be reduced to 10 per cent of the charge per year In addition, recycling at disposal provides the opportunity to reduce emissions upon retirement by more than 80 per cent. If recycling is fully utilised, emission at disposal may decrease to 15 per cent of the amount originally charged (Q =15%). According to UNEP Technical Options Report (UNEP, 1989), typical refrigerant charges in mobile air conditioners are 1.2 kg/unit for cars and 1.5 kg/unit for trucks. MACs in newer cars may have a lower charge, e.g., 800 g which is typical for Japanese passenger cars (Nagayama, 1996).



### 2.17.4.3 Estimation of Emissions of HFCs and PFCs from Foam Blowing HFCs are potential replacements for CFCs and HCFCs in the manufacture of insulating, cushioning, and packaging foams. The specific compounds that may be used include HFC125, HFC-134a, HFC-143a, and HFC-152a (Kroeze, 1995; U.S. EPA, 1992b). HFCs and PFCs may potentially be used as alternative blowing agents in the manufacture of open cell foam products such as cushioning and packaging foams. For open cell foams, HFC and PFC emissions occur at the time of manufacture and are equal to 100 per cent of the total quantity of chemical used as the blowing agent (U.S. EPA, 1992a; Fisher and Midgley, 1993). As a result total HFC or PFC emissions in year t for open cell foam can be calculated as follows:

Emissions of HFCs or PFCs in year t

= 100% of the quantity of HFCs or PFCs sold for blowing open cell foam in year t

The total quantity of HFCs or PFCs used in blowing open cell foam can be calculated as the quantity (in kg or tonnes) of foam manufactured in a given year times the quantity of HCF or PFC used per kilogram or tonne of open cell foam produced. Kroeze (1995) estimates that approximately 55 per cent of the HFC or PFC used as blowing agent in the manufacture of open cell foams could potentially be recycled. If such recycling occurs, total emissions from open cell foam manufacture would still be 100 per cent of the chemical sold for foam blowing purposes but this would be less because the

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.59 amount in use would be reduced by a quantity equal to that recycled. Provided that 55 per cent of the blowing agent is recycled, the gas used for the blowing process will be a mixture of 45 per cent virgin chemical and 55 per cent recycled chemical. For insulating (closed cell) foams, only about 10 per cent of the blowing agent is released during the blowing of the foam, while the remaining chemical is contained in the insulation. This quantity remaining in the foam is slowly released over the 20 to 25 year lifetime of the foam (Gamlen et al., 1986). HFC or PFC emissions from insulating foam in year t are therefore calculated as follows:

Emissions of HFCs or PFCs in year t

= 10 per cent of the total quantity of HFC or PFC used in manufacturing new insulating foam in year t

+ 4.5 per cent of the quantity of original HFC or PFC charge blown into the insulated foam manufactured between year t and year t-20

The total quantity of HFCs or PFCs used in blowing insulating foam can be calculated as the quantity (in kg or tonnes) of new foam manufactured in a given year times the quantity of HFC or PFC used per kilogram or tonne of new insulating foam produced and with 10 per cent production lost added. Typically, the blowing agent accounts for 6-15 per cent of the total foam weight (Fischer et al., 1991). The total quantity of HFC or PFC contained in the existing stock of insulating foam can be calculated as the product of the total quantity of insulating foam in use in year t and the average charge of chemical contained in each tonne of such installed insulating foam. Finally, Kroeze (1995) estimates that approximately half of the quantity of chemical emitted during the blowing of insulating foam could be reduced through recycling and/or leakage control and that approximately 80 per cent of the HFCs or PFCs contained in insulating foam at retirement could be recycled or destroyed (approximately 30 to 40 per cent of the charge remains in the foam upon retirement). If such potential future actions are implemented, then emissions in year t from insulating foam can be calculated as follows:

Emissions of HFCs or PFCs in year t

= 5% of the total quantity of HFC or PFC sold for use in manufacturing new insulating foam in year t

+ 3.6% of the total HFC or PFC contained in the existing stock of insulating foam in year t.

The production losses of 5 per cent represents net losses, that is the amount of blowing agent escaped from the process minus the amount of blowing agent recovered.

## I NDUSTRIAL 

## P ROCESSES

2.60 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2 . 1 7 . 4 . 4 E s t i m a t i o n o f E m i s s i o n s o f H F C s , PFCs, and SF 6 

### from Fire Extinguishing HFCs and PFCs are potential replacements for Halon 1211 in portable fire extinguishers and Halon 1301 in total flooding fixed fire extinguishing systems. Potential substitutes include HFC-23, HFC-125, HFC-227ea, PFC-410, and PFC-614 (U.S. EPA, 1992b; Kroeze, 1995). McCulloch (1992) estimates that total halon emissions can be estimated as 60 per cent of total halon 1211 contained in new portable halon fire extinguishers installed each year, and as 35 per cent of total Halon 1301 contained in new total flooding equipment installed each year. The remaining amounts of chemical, 40 per cent for portable fire extinguishers and 65 per cent for total flooding equipment respectively, add to the bank of fire extinguishing chemicals. Replacement HFCs and PFCs for fire extinguishing equipment are likely to be emitted at lower rates than the halons they replace, due to improved testing and practising procedures. Until these new procedures are adopted, however, emission rates for replacement chemicals may be similar to those for existing systems. The method used to estimate emissions here is appropriate for the mature market for fire extinguishing agents. Transition to HFCs and PFCs in this market would result in a relatively rapid increase in the banks of these materials held in equipment while the bank of halons would decline. Unless there is a requirement to replace the halons bank, the equations developed for halon emissions should be appropriate for HFCs and PFCs in this application and so the estimate for HFC or PFC emissions from portable equipment in year t would be:

Emissions of HFCs or PFCs in year t

= 60 per cent of the total quantity of HFC or PFC used in new portable halocarbon fire extinguishing equipment installed in year t

Similarly, emissions estimates in year t for total flooding equipment can be calculated as:

Emissions of HFCs or PFCs in year t

= 35 per cent of the total quantity of HFC or PFC used new fixed halocarbon fire extinguishing equipment installed in year t

Finally, McCulloch estimates that HFC and PFC emissions from the fire extinguishing equipment sector could eventually be reduced to 30 per cent of total sales for portable systems and 15 per cent of sales for fixed systems based on improved housekeeping, servicing, and bank management practices.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.61 Emission of sulphur hexafluoride from fire extinguishing equipment
Some of the new substitutes for halon in fire extinguishing equipment contain sulphur hexafluoride, SF 6 , probably in blends with HFC. If the products contain SF 6 , it is emitted to the atmosphere in the same manner as HFC or PFC. The equations for the estimation of HFC and PFC emissions from fire extinguishing equipment are therefore also valid for SF 6 , since they have to be adjusted for the proportion of the SF 6 in the original blend. Emissions of SF 6 are to be calculated according to the proportion of this chemical in the blend.



### 2.17.4.5 Estimation of Emissions of HFCs and PFCs from Aerosol Products HFCs may be used as replacements for CFCs and HCFCs in aerosol propellants in industrial and technical applications, and household, medical and personal care products. The HFCs that may be used include HFC-125, HFC-134a, 152a, and HFC-227ea (Kroeze, 1995; U.S. EPA, 1992b). Gases from aerosols are usually released shortly after production, on average six months after sale in the United States and Europe. During use of aerosols, 100 per cent of the chemical is emitted (Gamlen et al., 1986; U.S. EPA, 1992a). For this methodology, aerosol emissions are estimated to be one half of the current year sales of the aerosol plus one half of the previous year sales (Gamlen et al., 1986). In other words, aerosol emissions in year t can be calculated as follows:

Emissions of HFCs in year t

= 50% of the quantity of HFCs contained in aerosols sold in year t

+ 50% of the quantity of HFC contained in aerosols sold in year t-1

This calculation accounts for the six month lag from purchase to use. Total aerosol use each year can be calculated as the number of aerosol cans sold in a given year times the charge of HFC or PFC in each can. Finally, Kroeze (1995) points out that technologies do not exist to reduce emissions from aerosol cans.



### 2.17.4.6 Estimation of Emissions of HFCs and PFCs from Solvents HFCs and PFCs may be used as replacements for CFC-113 in metal cleaning, electronics, and precision cleaning applications and as replacements for aerosol cleaning. The compounds that may be used include HFC-43-10, PFC-614, PFC-512, PFC-612, PFC-716, and PFC-819 (Kroeze, 1995; U.S. EPA, 1992b). Chemicals used as cleaning agents are emitted during, or shortly after, use and are typically 100 per cent of total use (Fisher and Midgley, 1993; U.S. EPA, 1992a). This methodology assumes that solvents, on average, are used six months after they are sold. Total HFC or PFC emissions in year t can therefore be calculated as follows:

## I NDUSTRIAL 

## P ROCESSES

2.62 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Emissions of HFCs or PFCs in year t

= 50% of the quantity of HFCs or PFC sold for use in solvent applications in year t

+ 50% of the quantity of HFCs sold for use in solvent applications in year t-1

It has been estimated that solvent emissions can be reduced by up to 80 per cent through the use of improved housekeeping and recycling practices.



### 2.17.4.7 Estimation of Emissions of HFCs and PFCs from Other Applications Other Applications Other applications in which HFCs and PFCs may replace CFCs and HCFCs include sterilisation equipment, tobacco expansion applications, and use as solvents in the manufacture of adhesives, coatings, and inks. The specific compounds include HFC-125, HFC-134a, and HFC-227ea (Kroeze, 1995; U.S. EPA, 1992b). For other applications, it is assumed that all HFCs and PFC are released within 6 months after production. Emissions in the year t can be calculated as follows:

Emissions of HFCs or PFCs in year t

= 50% of the quantity of HFCs/PFCs sold for other applications in year t

+ 50% of the quantity of HFCs/PFCs sold in year t-1



### 2.17.4.8 Sulphur Hexafluoride (SF 6 

### ) Emissions
Primary uses of SF 6 Primary uses of SF 6 include the following:
Gas-Insulated Switchgear and Circuit Breakers
SF 6 is used as an insulation medium in high tension electrical equipment including gas insulated switchgear (GIS) and circuit breakers.
Fire suppression and explosion protection Some of the new gases placed on the market as substitutes for halons in fire extinguishing equipment, may contain up to 20 per cent sulphur hexafluoride, SF 6 . These applications are described in Section 2.17.4.4. Globally, it is estimated that about 80 per cent of SF 6 is used in gas-insulated switchgear and circuit breakers, 5 to 10 per cent in the magnesium and aluminium industries, and 5 to 10 per cent in a number of smaller applications (Ko et al., 1993).

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.63 Other applications
SF 6 is used in a variety of additional applications including as an insulating medium in sound proof windows, in leak detectors, gas-air tracers, and various electronic applications. The use of SF 6 in production of aluminium and magnesium is covered under Section 2.13.8.
Recommended methodology for estimating SF 6 emissions
Total emissions of SF 6 used in GIS application and circuit breakers can be assumed to be approximately 1 per cent of the total quantity of SF 6 contained in such equipment each year (NILU, 1993). In addition, if it is assumed that GIS equipment has a lifetime of 30 years, then approximately 70 per cent of the SF 6 will remain in the equipment upon retirement and will then be released upon disposal of the equipment (NILU, 1993). Total emissions from GIS applications can therefore be estimated as:

Emissions of SF 6 in year t

= 1% of the total charge of SF 6 contained in the existing stock of equipment in year t

+ 70% of the quantity of equipment manufactured in year t-30.

The total charge of SF 6 contained in equipment can be estimated as the product of the total quantity of equipment in operation and the typical charge size of equipment. Charge sizes for GIS equipment rated to 50 kV or more can range from hundreds to thousands of kilos per installation, and for low-voltage switches contain 1-2 kg per installation (Kroeze, 1995). If data on the total stock of GIS are unavailable, then it should be assumed that emissions equal consumption.

## I NDUSTRIAL 

## P ROCESSES

2.64 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 2.18 References

Abrahamson, D. (1992), “Aluminium and global warming.” Nature pp. 356, 484. AFEAS (1995), Production, Sales and Atmospheric Release of Fluorocarbons through 1993

. AFEAS Program Office, Washington, DC 20005, USA. Air and Waste Management Association (AWMA) (1993), The Air Pollution Engineering Manual, Chapter 14: Metallurgical Industry. Ferroalloy Particulate Emissions. A. J

. Buonicore and W. Davis (eds). Van Nostrand Reinhold, New York. Barnard, W.R. (1990 ), Emission Factors for Iron and Steel Sources-Criteria and Toxic Pollutants

. EPA-600/2-90-024 (PB 90-242314), USA. CASPER (1995) Holtmann, T O. Rentz, Z. Samaras, Y. Tymbanidis, T. Zachariadis, M. Aslanoglou, K. Kulicke and K-H. Zierock, Development of a methodology for forecasting atmospheric emissions from relevant stationary and mobile sources, Karlsruhe, Thessaloniki, Berlin, Project report, November, 1995. CEMBUREAU (1990), World Cement Market in Figures and World Statistics Review

. CICERO (1992), An Assessment of the Role of CF 4 and C 2 F 6 as Greenhouse Gases. I.S.A. Isaksen (ed.) Oslo, Norway. CFI (1992), Letter from the Canadian Fertiliser Institute to Environment Canada (personal communication). Choe J.S., P.J. Gook and F.P. Petrocelli (1993), Developing N 2 O abatement technology for the nitric acid industry . Paper presented at the 1993 ANPSG Conference, Destin, Florida, USA, 6 October, 1993. Cook, E. (1995), Lifetime Commitments: Why Climate Policy-makers Can’t Afford to Overlook Fully Fluorinated Compounds . World Resources Institute. Cotton, F.A. and G. Wilkinson (1988), Advanced Inorganic Chemistry , 5 th Edition, ISBN 0- 471-84997-9. Wiley, New York, USA. Du Pont (1994), Information presented at the Tenth Meeting of the International Negotiating Committee, Geneva, 27 August, 1994. E.I. du Pont de Nemours and Co., Inc., Delaware, USA. EMEP/CORINAIR (1996), Joint Atmospheric Emission Inventory Guidebook (1st edition). Enquete Commission (1994), Responsibility for the Future, Options for Sustainable Management of Substance Chains and Material Flows . Interim report submitted by the 12th German Bundestag’s Enquete Commission on the “Protection of Humanity and the Environment-Assessment Criteria and Prospects for Environmentally Sound Product Cycles in Industrial Society”, Economica Verlag , ISBN 3-87081-044-4, Bonn, Germany. Environment Canada (1983), A Nationwide Survey of Emission of Air Contaminants. Environment Canada Report. EPS 3-EP-83-10, Ottawa, Canada. Environment Canada (1987), Review of the Canadian Fertiliser Industry and Evaluation of Control Technology . Conservation and Protection Report EPS 2/AG/1. Environment Canada (1996), CO 2 Emission Factors for the Iron and Steel Industry. Internal memo, F. Neitzert, March 1996.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.65 Fay, K.J. (1995), Critique of Articles by C. Kroeze Concerning Potential Effect of HFC Policy on Global Greenhouse Gas Emissions . Alliance for Responsible Atmospheric Policy and International Climate Change Partnership, Arlington VA, USA. Fischer S.K., P.J. Hughes, P.D. Fairchild, C.L. Kusik, J.T. Dieckmann, E.M. McMahon and N. Hobday, (1991). Energy and Global Warming Impacts of CFC Alternative Technologies . AFEAS and U.S. Dept. of Energy, Alternative Fluorocarbons Environmental Acceptability Study, Washington DC, USA. Fisher, D.A. and P.M. Midgley (1993), “The production and Release to the Atmosphere of CFCs 113, 114 and 115.” Atmospheric Environment 27A (2):271-276. Fisher, W.B. and L. Crescenti (1994), “Caprolactam.” In: Kirk-Othmer Encyclopedia of Chemical Technology , 4 th Edition, Vol. 4, Wiley Interscience, New York. Fujimoto, R. (1991), (personal communication) 27 February, 1989 from Mr. Fujimoto of Hitachi Ltd. to Ms. Jean Lupinacci of the U.S. Environmental Protection Agency. [Referenced in: Energy and Global Warming Impacts of CFC Alternative Technologies. Alternative Fluorocarbons Environmental Acceptability Study (AFEAS)], U.S. Department of Energy. Gamlen, P.H., B.C. Lane, P.M. Midgley and J.M. Steed (1986), “The Production and Release to Atmosphere of CCl 3 F and CCl 2 F 2 (chlorofluorocarbons CFC-11 and CFC12).” Atmospheric Environment 20(6):1077-1085. Griffin, R.C. (1987), “CO 2 release from cement production, 1950-1985.” In: Marland, G., T.A. Boden, R.C. Griffin, S.F. Huang, P. Kanciruk, and T.R. Nelson, Estimates of CO 2 Emissions from Fossil Fuel Burning and Cement Manufacturing, Based on the United Nations Energy Statistics and the U.S. Bureau of Mines Cement Manufacturing Data. Report No. #ORNL/CDIAC-25, Carbon Dioxide Information Analysis Centre, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA. May 1989, pp. 643-680. Harnisch, J. and R. Borchers (1995), Proceedings of the Conference on Pollution of the Troposphere and Stratosphere Exchange of Air Masses and Related Monitoring , Munich, Germany, 19-22 June, 1995, European Optical Society, Vol. 2506. Industrial Chemicals (1980), W.l. Faith, D.B. Keyes and R.L. Clark (eds.), 3 rd Edition, John Wiley and Sons, New York, New York, USA. IPCC (1992), Climate Change 1992, the Supplementary Report to the IPCC Scientific Assessment, U.K. J.T. Houghton, B. A. Callander and S. K. Varney (eds), Cambridge University Press, Cambridge, IPCC/OECD/IEA (1995), IPCC Guidelines for National Greenhouse Gas Inventories, IPCC/OECD/IEA Inventory Programme, Paris, France. IPCC (1996), Climate Change 1995 . The Science of Climate Change . J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg and K. Maskell (eds), Cambridge University Press, Cambridge, U.K. Japan Environment Agency (1995), Study of Emission Factors for N 2 O from Stationary Sources

. Jaques, A.P. (1992), Canada's Greenhouse Gas Emissions: Estimates for 1990 . Environment Canada Report EPS 5/AP/4. Khalil, M.A.K. and R. Rasmussen (1985), “Atmospheric Carbon Tetrafluoride (CF 4 ): Sources and Trends.” Geophysical Res. Lett. 12:671-672.

## I NDUSTRIAL 

## P ROCESSES

2.66 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Ko, M.K., N.D. Sze, W.C. Wang, G. Shia, A. Goldman, F.J. Murcray, D.G. Murcray and C.P. Rinsland (1993), “Atmospheric sulphur hexafluoride: sources, sinks and greenhouse warming.” J. Geophysical Research 98 (D6):10499-10507. Kroeze, C. (1994), Nitrous oxide-emission inventory and options for control in the Netherlands

. RIVM Report No. 773001004, RIVM, Bilthoven, The Netherlands. Kroeze, C. (1995), Fluorocarbons and SF 6 : Global emission inventory and control . RIVM Report No. 773001007, Bilthoven, The Netherlands. Laval University (1994) , Polyfluorocarbons and the Environment (Their Effect on the Atmospheric Equilibrium) : study for Environment Canada. March Consulting Group (1996), UK Use and Emissions of Selected Halocarbons . A study for the UK Department of Environment. Marland, G., T.A. Boden, R.C. Griffin, S.F. Huang, P. Kanciruk and T.R. Nelson (1989), Estimates of CO 2 Emissions from Fossil Fuel Burning and Cement Manufacturing, Based on the United Nations Energy Statistics and the U.S

. Bureau of Mines Cement Manufacturing Data. Report No. #ORNL/CDIAC-25, Carbon Dioxide Information Analysis Centre, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.McCulloch, A. (1992), “Global production and emissions of bromochlorofluorodifluoromethane and bromotrifluoromethane (Halons 1211 and 1301).” Atmospheric Environment26:1325-1329. McCulloch, A. (1994), “Sources of hydrochlorofluorocarbons, hydrofluorocarbons and fluorocarbons and their potential emissions during the next twenty five years.” Environ. Monitoring and Assessment 31:167-174. McFarland, M. and J. Kaye (1992), “Hydrochlorofluorocarbons and ozone.” Photochem. Photobiol. 55:911-925. NILU (1993), SF 6 as a Greenhouse Gas-An Assessment of Norwegian and Global Sources and the Global Warming Potential. Norwegian Institute for Air Research. Lillestrom, Norway. December, 1993. Nagayama, (1996) Tohru Nagayama, Global Environment Department, Environment Agency, Japan. Comment to IPCC Draft Guideline, 1996. Norsk Hydro (1996), personal communication with Norsk Hydro a.s, Norway. Norwegian Pollution Control Authority. SFT (1994), Greenhouse Gas Emissions in Norway. Inventories and Estimations methods. September, 1994. Report 94:02. Oslo. Olivier, J. (1996), personal communication (Restored from Norwegian version). Olsen, S.E. (1991), Kalsiumkarbid og CO 2 , STF34 A91142. SINTEF. Ontario Research Foundation and SNC/GECO Canada Inc. (1981), A Nationwide Inventory of Anthropogenic Sources and Emissions of Primary Fine Particulate Matter. Prepared for Environment Canada, 1981. Oonk, H. (1996), personal communication. ORTECH International (1991), Compilation of an Ontario Gridded Carbon Dioxide and Nitrous Oxide Emission Inventory . Ortech Report No. P-91-50-6436/OG ORTECH International (1994), Inventory Methods for Estimating Canadian Emissions of Greenhouse Gases, Report to Environment Canada, May, 1994.

## 2 I NDUSTRIAL 

## P ROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 2.67 Parsons, T. (1977), Industrial Process profiles for Environmental Use: Chapter 24, The Iron and Steel Industry. Report by Radian Corp. to U.S.EPA, NTIS PB-266 226. Radian Corp. (1986), Evaluation of Potential Ozone Depleting Substances, Emissions and Control: Draft report retail food for store refrigeration , U.S. EPA, October 1986 Raaness, O. (1991), Silisiumkarbid og CO 2 , STF34 A91134. SINTEF 1991. Rankin W. J. and J. K. Wright, (1992), Greenhouse Strategies for the Metallurgical Industry. Minerals, Metals and the Environment Conference, Manchester, UK. Reimer, R.A., R.A. Parrett and C.S. Slaten (1992), Abatement of N 2 O emission produced in adipic acid. Proc. of the 5 th Int. Workshop on Nitrous Oxide emissions, Tsukuba Japan, 1-3 July, 1992. Rosland, A. (1987), Utslippskoeffisienter. Oversikt over koeffisienter for utslipp til luft og metoder for å beregne disse . Norwegian Pollution Control Authority, Oslo. Rypdal, K. (1993), Anthropogenic Emissions of the Greenhouse Gases CO 2 , CH 4 and N 2 O in Norway. A documentation of methods of estimation, activity data and emission factors. Statistics Norway. Report 93/24. Rypdal, K. (1995), Anthropogenic Emissions of SO 2 , NO x , NMVOC and NH 3 in Norway

. Rapporter Statistic Norway, 95/16, Oslo. Schade, H. (1980), Die Schadstoffemissionen der Eisen-und Stahlindustrie in den Belastungsgebieten Buhrgebiet-West und Ruhrgebiet-Ost . Schriftenr. d. Landesanstalt für Immissionsschutz des Landes N.W. 52: 55-62, Germany. Schiff, H., Unisearch Associates (1994), Presentation at PFC WORKSHOP, London, March, 1994. Also, Measurements of CF 4 and C 2 F 6 in the Emissions from Canadian Aluminium Smelters by Tuneable Diode Absorption Laser Spectroscopy, April, 1994 Shareef, G.S., W.A. Butler, L.A. Bravo and M.B. Stockton (1988), Air emissions species manual Vol. 1 . Volatile Organic Compounds (VOC) Species Profiles. EPA-450/2- 88-003a (PB 88-215792); Addendum (1989), EPA-450/2-88-003 c (PB 90- 146416), USA. Sintef (1991a), Ferrolegering og CO 2 STF34 A91056. 8 May 1991. Sintef Norway Sintef (1991b), Reduserte CO 2 -utslipp i aluminiumelektrolysen ved bruk av inert anoder. STF34 A91175, 19 September 1991. Sintef, Norway Stockton M.B., and J.H.E. Stelling (1987), Criteria pollutant emission factors for the 1985 NAPAP emissions inventory. U.S. EPA Washington DC, USA. Ouverage, EPA600/7-87-015 XV-211. Streibel, H. (1974), “Silicon”, in Chemical and Process Technology Encyclopedia, D. Considine (ed.). McGraw Hill, Montreal. Tabereaux, A. T. (1995), 5 th Australian Aluminium Smelter Technology Workshop , Sydney, October 1995. Thiemens, M.H. and W.C. Trogler (1991), “Nylon production; an unknown source of atmospheric nitrous oxide.” Science: 251:932-934. Thonstad, Oygard and Diep (1994), On the Formation and Decomposition of C-F Gases in Aluminium Cells . PFC Workshop, London, UK. March, 1994.

## I NDUSTRIAL 

## P ROCESSES

2.68 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Tresouthick, S.W. and A. Mishulovich (1990), Energy and environment considerations for the cement industry . In conference proceedings Energy and Environment in the 21st Century . Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. 26-28 March, 1990. B-110 to B-123. UNEP (United Nations Environment Programme) (1989), Montreal Protocol on Substances That Deplete the Ozone Layer. Refrigeration, Air Conditioning and Heat Pumps Technical Options Report 1989. UNEP (1994), Report of the Technology and Economic Assessment Panel to the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer, p. 9-1, UNEP, Nairobi, March 1994. United Nations (1988), United Nations Statistical Yearbook . United Nations, New York, USA. Unisearch Associates (1994), Measurements of CF 4 and C 2 F 6 in the Emissions from Canadian Aluminium Smelters by Tuneable Diode Absorption Laser Spectroscopy . Unisearch Associates. Ontario, Canada. 5 April,1994. U.S. Bureau of the Mines (1988), Cement Minerals Yearbook , authored by Wilton Johnson. U.S. Bureau of the Mines, U.S. Department of the Interior, Washington DC, USA. U.S. Environmental Protection Agency (1985), Criteria Pollutant Emissions Factors. Volume 1, Stationary Point and Area Sources . AP-42 4 th Edition (and Supplements A and B). U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA. U.S. Environmental Protection Agency (1986), Compilation of Air Pollutant Emission Factors. AP-42, Supplement A, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA. U.S. Environmental Protection Agency (1992a), Regulatory Impact Analysis: Compliance with Section 604 of the Clean Air Act for the Phaseout of Ozone Depleting Chemicals, 1992

. U.S. Environmental Protection Agency (1992b), Risk Screen on the Use of Substitutes for Class I Ozone Depleting Substances Prepared in Support of the Significant New Alternatives Policy Program (SNAP), 1992. U.S. Environmental Protection Agency (1993), Regulatory Impact Analysis Prepared in Support of the National Recycling and Emissions Reduction Program , prepared for the U.S. EPA by ICF. U.S. Environmental Protection Agency (1994a), Preliminary Method for Estimating Country Emissions of CF 4 and C 2 F 6 . Cindy Jacobs, July, 1994. U.S. Environmental Protection Agency (1994b), Inventory of U.S

. Greenhouse Gas Emissions and Sinks: 1990-1993 , p. 38, U.S. EPA, Washington DC, USA. EPA 230-R-94- 014. U.S. Environmental Protection Agency (1995), Comment from U.S

. EPA to second draft of Chapter 8, December, 1995. Workbook, Australia (1995), Workbook for Industrial Emissions and Solvent Use , National Greenhouse Gas Inventory Committee, Department of the Environment, Sport and Territories, Australia, Workbook 7.0.

## 1 E NERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 3 

# S OLVENT AND 

# O THER 

# P RODUCT 

# U S E

## 1 3 S OLVENT AND 

## O THER 

## P RODUCT 

## U SE

RGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 3.1 

# 3 S OLVENT AND 

# O THER 

# P RODUCT 

# U SE



## 3.1 Overview Solvents and related compounds are important for greenhouse gas (GHG) and other emission inventories because they are a significant source of emissions of non-methane volatile organic compounds (NMVOCs). No other GHGs are emitted in significant amounts from the use of solvents and related compounds, which include chemical cleaning substances used in dry cleaning, printing, metal degreasing, and a variety of industrial applications as well as household use. Also included in this category are paints, lacquers, thinners and related materials used in coatings in a variety of industrial, commercial and household applications. Table 3-1 lists some of the potentially important subcategories included under this source category. This category also includes evaporative emissions of greenhouse gases arising from other types of product use. This included, for example, N 2 O emissions from medical use. Emissions arising from the use of hydrofluorocarbons (HFCs) in applications like refrigeration, air conditioning, fire extinguishers, solvents foam-blowing, cooling and aerosols should be reported in Industrial Processes under category 2F. All of the substances included here contain significant amounts of NMVOC. Emissions are produced through evaporation of the volatile chemicals when these products are exposed to air. Non-methane volatile organic compounds (NMVOCs) are often emitted in significant quantities from evaporation during the variety of dispersed activities discussed above. These emissions are sometimes referred to as "area" sources because they occur in large numbers of small dispersed applications, rather than from large centralised industrial processes (or "point" sources). Solvent and other product use is treated as a separate category in detailed inventory procedures (e.g., CORINAIR) because the nature of this area source requires a somewhat different approach to emissions estimation than that used for calculating other emissions categories. The IPCC Guidelines treats the category separately for this reason.

## S OLVENT AND 

## O THER 

## P RODUCT 

## U SE

3.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 3.2 NMVOC Emissions from Solvent and Other Product Use NMVOC emissions estimates are characterised by high uncertainty. This is especially true for the solvent use source category on a global scale. The contribution of this source category is believed to be quite significant. A preliminary analysis estimated total global NMVOC release from solvent use to be about 11 per cent of total NMVOC emissions (Watson, et al., 1991). Based on national GHG emissions inventories, NMVOC emissions from these sources can represent a much larger share of the total NMVOC emissions for some countries. NMVOC from solvent use represents 31 per cent of the total NMVOC emissions for both Italy and Denmark. (ENEA, 1991, Fenger et al., 1990) The Netherlands estimates solvent use to account for 25 per cent, and both Finland and the United States estimate emissions to be 24 per cent of their total NMVOC emissions (van den Born et al., 1991, Boström et al., 1992, US EPA, 1991). By contrast, emissions from solvent use in Nigeria were only 3 per cent of the total NMVOC (Obioh et al., 1992).



### 3.2.1 Estimating Emissions The wide variations in national emissions from solvent and other product use highlight the differences in their use between countries and some of the difficulties associated with accurately estimating emissions from these sources. There are two basic approaches to estimation of emissions from Solvent and Other Product Use, which depend on the availability of data on the activities producing emissions and the emission factors.
1 Production-based - In some cases, solvent or coating use is associated with centralised industrial production activities, such as automobile and ship production, textile manufacture, paper coating, chemical products manufacture, etc. In these cases it is generally possible to develop NMVOC emission factors based on unit of product output. These are based on the amount of paint, solvents, or other chemically volatile products consumed per unit of production of the final products. Once reasonable factors are developed it is straightforward to estimate annual emissions based on production data which are generally available on an annual basis for most countries. Industrial production data is also compiled and published by international organisations (e.g., United Nations, 1992) and these data can be used to supplement locally available data. 2 Consumption-based - In many applications of paints, solvents and similar products, the end uses are too small-scale, diverse, and dispersed to be tracked directly. Therefore emissions estimates are generally based on total consumption (i.e., sales) of the solvents, paints, etc. used in these applications. The assumption is that once these products are sold to end users, they are applied and emissions produced relatively rapidly. For most surface coating and general solvent use, this approach is used. Emission factors are developed based on the likely ultimate release of NMVOC to the atmosphere per unit of product consumed. These emission factors can then be applied to sales data for the specific solvent or paint products. The IPCC/OECD joint programme has not produced any original work on estimation of NMVOCs from the use of these products. This is for two reasons. First, NMVOC is a greenhouse gas (actually a class of gases) covered under the programme, but it has been

## 3 S OLVENT AND 

## O THER 

## P RODUCT 

## U SE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### . 3.3 assigned a lower priority for national experts just initiating greenhouse gas inventory work. Most methods development work within the IPCC/OECD programme has focused on providing methods and default information for the first priority gases - CO 2 , CH 4 , and N 2 O, which are direct greenhouse gases. Second, NMVOCs are among the gases already under heavy scrutiny in national and international inventory programmes because of their role as local and regional air pollutants. Hence there is a large and growing body of literature containing guidance on estimation procedures and emission factors for NMVOCs from a number of source categories, including from solvents and other products. National experts who are already familiar with these procedures and have emissions data available or under development, should report these data to the IPCC/OECD programme, as discussed in Volume 1: Reporting Instructions

. Other experts needing information should consult the existing major references such as:

• Default Emission Factor Handbook (EEATF, 1992);

• US EPA's Compilation of Air Pollutant Emissions Factors (AP-42) (US EPA, 1985) and Supplement F (AP-42) (US EPA, 1993);

• Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory (Stockton and Stelling, 1987).

• Proceedings of the TNO/EURASAP Workshop (TNO Inst. of Environmental Sciences, 1993).

• EMER/CORINAIR (1996) Joint Emission Inventory Guidebook (1st edition).



### 3.2.2 Uncertainties Because NMVOC emission controls vary widely throughout the world, it is important for national experts to account for the level of emission control application in their country. Also, there may be significant differences among countries regarding the processes and equipment used. These differences can affect the level of NMVOC emissions. Finally, because estimates based on consumption data provide only an approximation of the activities associated with the manufacture of all products within a particular subcategory, there is a degree of uncertainty in the estimates (Watson, et al., 1991).

T ABLE 3-1 P OTENTIALLY I MPORTANT S UBCATEGORIES I NCLUDED U NDER S OLVENT AND O THER P RODUCT U SE Surface coating (e.g., painting) operations Applications of paints, lacquer, enamel and primer to cans, wood products, metal parts, buildings, etc. Use of thinning solvents. Paper coating operations Coating operations, mixing and use of thinning solvents. Printing and Publishing Press operations, lithography, use of thinning solvents. General Solvent Use Vapour degreasing, dry cleaning, textile manufacture, household solvent use. Production of Automobiles and Trucks Surface coating, cleaning/degreasing operations. Ship building Surface coating, cleaning/degreasing operations. Chemical Products Manufacture and Processing Solvents are used in a variety of applications in the manufacturing of chemicals and chemical products.

## S OLVENT AND 

## O THER 

## P RODUCT 

## U SE

3.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 3.3 References Boström, S., R. Backman, M. Hupa (1992), Greenhouse Gas Emissions in Finland 1988 and 1990, Energy, Industrial, and Transport Activities . Published by Innsinööritoimisto Prosessikemia, Finland. EMEP/CORINAIR (1996), Joint Atmospheric Emission Inventory Guidebook (1st Edition). EEATF (1992), Default Emission Factor Handbook

. ENEA (1991), National Emission Inventories of SO x , NO x , NMVOCs, CO, TSP, NH 3 , CH 4 , CO 2 , N 2 O in Italy, 1985-1989 , Italy. Fenger, J., J. Fenhann, N. Kilde (1990), Danish Budget for Greenhouse Gases . Nordic Council of Ministers, Copenhagen, Denmark, Nord 1990:97. Obioh, I.B., A.F. Oluwole, F.A. Akeredolu (1992), “The methodology and status of greenhouse gases (GHG) inventory In Nigeria: 1988 inventory results.” Paper presented at the IPCC/OECD Workshop on National Inventories of GHGs , Hadley Centre, Bracknell, UK. Stockton M.B., and J.H.E. Stelling (1987), Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory . US EPA Washington, Ouverage, EPA-600/7-87-015 XV-211. TNO Institute of Environmental Sciences (1993), Proceedings of the TNO/EURASAP Workshop on the Reliability of VOC Emission Databases . Edited by H.P. Baars, P.J.H. Builtjes, M.P.J. Pulles, C. Veldt, IMW-TNO Publication P 93/040, Delft, The Netherlands. United Nations (1992), United Nations Statistical Yearbook . United Nations Statistical Office, New York, US. US Environmental Protection Agency, Office of Air Quality Planning and Standards (1985), Compilation of Air Pollutant Emission Factors (Fourth Edition), Volume I: Stationary Point and Area Sources . EPA-AP-42 (GPO 055-000-00251-7), Research Triangle Park. US Environmental Protection Agency, Office of Air Quality Planning and Standards (1991) National Air Pollutant Emission Estimates 1940-1989 . EPA-450/4-91-004, Research Triangle Park. US Environmental Protection Agency (1993), Office of Air Quality Planning and Standards. 1985. Compilation of Air Pollutant Emission Factors, Volume I: Stationary Point and Area Sources . EPA-AP-42, Supplement F. van den Born, G.J., A.F. Bouwman, J.G.J. Olivier, and R.J. Swart (1991), The Emission of Greenhouse Gases in the Netherlands (Report no. 222901003). National Institute of Public Health and Environmental Protection, The Netherlands. Watson, J.J., J.A. Probert and S.D. Picot (1991), Global Inventory of Volatile Organic Compound Emissions from Anthropogenic Sources . Prepared for the Office of Research and Development, US EPA, Washington, D.C., US.

## 4 A GRICULTURE

IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 4 

# A GRICULTURE

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.1 

# 4. A GRICULTURE



## 4.1 Overview Agricultural activities contribute directly to emissions of greenhouse gases through a variety of different processes. This chapter discusses four greenhouse gas-emitting activities:

• CH 4 and N 2 O emissions from domestic livestock (enteric fermentation and manure management)

− **CH 4**  **emissions from enteric fermentation in domestic livestock** Methane is produced in herbivores as a by-product of enteric fermentation, a digestive process by which carbohydrates are broken down by micro-organisms into simple molecules for absorption into the bloodstream. Both ruminant animals (e.g., cattle, sheep) and some non-ruminant animals (e.g., pigs, horses) produce CH 4 , although ruminants are the largest source since they are able todigest cellulose, a type of carbohydrate, due to the presence of specific microorganisms in their digestive tracts. The amount of CH 4 that is released depends on the type, age, and weight of the animal, the quality and quantity of the feed, and the energy expenditure of the animal.

− **CH 4**  **emissions from manure management** CH 4 is produced from the decomposition of manure under anaerobic conditions. These conditions often occur when large numbers of animals are managed in a confined area (e.g., dairy farms, beef feedlots, and swine and poultry farms), where manure is typically stored in large piles or disposed of in lagoons.

− **N 2**  **O emissions from manure management** During storage of manure, some manure nitrogen is converted to N 2 O. Emissions of N 2 O related to manure handling before the manure is added to soils are included in this source category. (Manure-related N 2 O emissions from soils are considered agricultural soil emissions).

• CH 4 emissions from rice cultivation Anaerobic decomposition of organic material in flooded rice fields produces methane, which escapes to the atmosphere primarily by transport through the rice plants. The amount emitted is believed to be a function of rice species, number and duration of harvests, soil type and temperature, irrigation practices, and fertiliser use. The seasonally integrated CH 4 flux depends upon the input of organic carbon, water regimes, time and duration of drainage, soil type etc.

• CH 4 , CO, N 2 O, and NO X emissions from agricultural burning (savanna and agricultural burning)

– **CH 4**  **, CO, N 2**  **O, and NO X**  **emissions from the prescribed burning of**

**savannas** The burning of savannas – areas in tropical and subtropical formations with continuous grass coverage – results in the instantaneous emissions of carbon

## A GRICULTURE

4.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual dioxide, but because the vegetation regrows between burning cycles, the carbon dioxide released into the atmosphere is reabsorbed during the next vegetation growth period. Net CO 2 emissions are therefore assumed to be zero. However, savanna burning also releases gases other than CO 2 , including methane, carbon monoxide, nitrous oxide and oxides of nitrogen. Unlike CO 2 emissions, these are net emissions.

– **CH 4**  **, CO, N 2**  **O, and NO X**  **emissions from the burning of agricultural residues**  The burning of crop residues is not thought to be a net source of carbon dioxide because the carbon released to the atmosphere is reabsorbed during the next growing season. However, this burning is a significant source of emissions of methane, carbon monoxide, nitrous oxide, and nitrogen oxides. It is important to note that some crop residues are removed from the fields and burned as a source of energy, especially in developing countries. Non-CO 2 emissions from this type of burning are dealt with in the Energy module of this manual. Crop residue burning must be properly allocated to these two components in order to avoid double counting.

• CH 4 , CO 2 , and N 2 O emissions from agricultural soils
Emissions of N 2 O from agricultural soils are primarily due to the microbial processes of nitrification and denitrification in the soil. Three types of emission can be distinguished: direct soils emissions, direct soil emissions of N 2 O from animal production (including stable emissions to be reported under Manure Management) and indirect emissions. Increases in the amount of nitrogen added to the soil generally result in higher N 2 O emissions (Bouwman, 1990). Direct soil emissions may result from the following nitrogen input to soils: (1) synthetic fertilisers, (2) nitrogen from animal waste, (3) biological nitrogen fixation, (4) reutilised nitrogen from crop residues, and (5) sewage sludge application. In addition, cultivation of organic soils may increase soil organic matter mineralisation and, in effect, N 2 O emissions. Direct soil emissions of N 2 O from animal production include those induced by grazing animals. Emissions from other animal waste management systems are reported under “Manure Management’’. Indirect N 2 O emissions take place after nitrogen is lost from the field as NO x , NH 3 or after leaching or runoff. Agricultural soils may also emit or remove CO 2 and/or CH 4 . For example, peat compost used as a soil amendment in agriculture and gardening may result in CO 2 emissions or removals. Carbon emissions from organic, mineral and limed soils are discussed in Chapter 5.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.3 

## 4.2 Methane And Nitrous Oxide Emissions From Domestic Livestock Enteric Fermentation And Manure Management

4.2.1 Overview of Methane and Nitrous Oxide Emissions from Livestock
This section covers methane and nitrous oxide emissions from enteric fermentation and the management of manure from domestic livestock. Cattle are the most important source of methane from enteric fermentation in most countries because of their high numbers, large size, and ruminant digestive system. Methane emissions from manure management are usually smaller than enteric fermentation emissions, and are principally associated with confined animal management facilities where manure is handled as a liquid. This section presents a brief overview of the key factors affecting methane and nitrous oxide emissions from these sources. The methods for estimating methane emissions are then presented. 1 The method for estimating nitrous oxide emissions from manure management is presented in Section 4.5.3.

Enteric Fermentation Methane is produced during the normal digestive processes of animals. The amount of methane produced and excreted by an individual animal is dependent primarily on the following:

• Digestive System The type of digestive system has a significant influence on the rate of methane emission. Ruminant animals have the highest emissions because a significant amount of methane-producing fermentation occurs within the rumen. The main ruminant animals are cattle, buffalo, goats, sheep and camels. Pseudo-ruminant animals (horses, mules, asses) and monogastric animals (swine) have relatively lower methane emissions because much less methane-producing fermentation takes place in their digestive systems.

• Feed Intake Methane is produced by the fermentation of feed within the animal's digestive system. Generally, the higher the feed intake, the higher the methane emission. Feed intake is positively related to animal size, growth rate, and production (e.g., milk production, wool growth, or pregnancy). The amount of methane emitted by a population of animals is calculated by multiplying the emission rate per animal by the number of animals. To reflect the variation in emission rates among animal types, the population of animals is divided into subgroups, and an emission rate per animal is estimated for each subgroup. Types of population subgroup are recommended in the method 2

.

1 All GHG emissions from the burning of animal waste are estimated in Section 1.4; Greenhouse Gas Emissions from Burning Traditional Biomass Fuels. CO 2 from the burning of animal waste is part of a closed cycle and is not counted as net CO 2 . 2 Countries are encouraged to carry out emissions inventory calculations at a finer level of detail if possible. Many countries have available more detailed information than

## A GRICULTURE

4.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Human management of wildlife can affect the total number of animals and therefore their emissions, though the associated emissions are believed to be small. The key issue is distinguishing those emissions resulting from human interventions from those emissions that would have occurred naturally. No methodology for estimating these emissions is presented here, though they may be estimated if national experts can fully document their approach, including all assumptions and methods. If these emissions are estimated, they should be reported in the “Other” subcategories of the Enteric Fermentation and Animal Wastes Tables (4 A & B) of Volume 1: Reporting Instructions

. Manure Management
Livestock manure is principally composed of organic material. When this organic material decomposes in an anaerobic environment (i.e., in the absence of oxygen), methanogenic bacteria, as part of an interrelated population of micro-organisms, produce methane. The principal factors affecting methane emission from animal manure are the amount of manure produced and the portion of the manure that decomposes anaerobically. The amount of manure that is produced is dependent on the amount produced per animal and the number of animals. The portion of the manure that decomposes anaerobically depends on how the manure is managed. When manure is stored or treated as a liquid (e.g., in lagoons, ponds, tanks, or pits), it tends to decompose anaerobically and produce a significant quantity of methane. When manure is handled as a solid (e.g., in stacks or pits) or when it is deposited on pastures and rangelands, it tends to decompose aerobically and little or no methane is produced. To estimate methane emission, the animal population must be divided into subgroups to reflect the varying amounts of manure produced per animal, and the manner in which the manure is handled. Population subgroups are recommended in the method. Nitrous oxide is formed when manure nitrogen is nitrified or denitrified. The amount of N 2 O released depends on the system and duration of waste management. Emissions of N 2 O taking place during storage or handling of manure (i.e., before the manure is added to soils) are reported under “ Manure Management”. Manure-induced N 2 O emissions from soils are considered soil emissions ( See Section 4.5 of this Reference Manual).

was used in constructing default values here. Countries may wish to calculate emissions estimates at a finer level of detail by subcategory – further disaggregating recommended activity categories and subcategories – or they may choose to subdivide the categories on some other basis which they feel is appropriate to their particular national circumstances. Working at finer levels of disaggregation does not change the basic nature of the calculations. Once emissions have been calculated at whatever is determined by the national experts to be the most appropriate level of detail, results should also be aggregated up to the minimum standard level of information requested in the IPCC proposed methodology. This will allow for comparability of results among all participating countries. The data and assumptions used for finer levels of detail should also be reported to the IPCC to ensure transparency and replicability of methods. Volume 1: Reporting Instructions discusses these issues in more detail.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.5 B OX 1 H UMAN WASTE USED AS FERTILISER Human waste is sometimes used as fertiliser, and can result in emissions or removals of CH 4 , N 2 O or CO 2 . At present, no methodology can be recommended for estimating CH 4 and CO 2 emissions. N 2 O emissions from Human waste are described in Chapters 4 & 6. The development of a methodology specifically for this source has been identified as an area for future work. Countries are nevertheless encouraged to estimate emissions from this source if they are able to do so. CH 4 emissions from this source can be estimated in one of at least two ways:

• Emissions from human waste used as fertiliser may be estimated in the present section by adapting the methodology for estimating emissions from livestock manure to use the data provided below. In this case, the estimate should be reported in the “Other” line in Tables 4 A & B in Volume 1: Reporting Instructions

. Bhattacharya et al. (1993) has reported these characteristics of human
waste: Dry waste per day = 0.107 kg/head/day Fractional carbon content = 0.375 And Thomas (1994, in press) reports the following values: Volatile solid production = 0.06 kg/head/day Dry matter production = 0.09 kg/head/day Fractional carbon content = 4.46% of dry matter

• These emissions can also be estimated using the methodology for sewage treatment in the Waste section. In this case, the emissions should then be treated as wastewater disposed of in aerobic (shallow) ponds, and should be reported in Table 6 B. In any case, care should be taken to avoid double counting emissions from this source.



### 4 . 2 . 2 I n v e n t o r y M e t h o d f o r M e t h a n e – O v e r v i e w
The method for estimating methane emission from enteric fermentation and manure management requires three basic steps: Step 1: Divide the livestock population into subgroups and characterise each subgroup. It is recommended that national experts use three year averages of activity data if available. This is to help prevent bias in the event that the base year of the inventory was an exceptional year not representative of the country’s normal activity level. Step 2: Estimate emission factors for each subgroup in terms of kilograms of methane per animal per year – separate emission factors are required for enteric fermentation and

manure. Step 3: Multiply the subgroup emission factors by the subgroup populations to estimate subgroup emission, and sum across the subgroups to estimate total emission. These three steps can be performed at varying levels of detail and complexity. This chapter presents the following two approaches:

## A GRICULTURE

4.6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Tier 1 A simplified approach that relies on default emission factors drawn from previous studies. The Tier 1 approach is likely to be sufficient for most animal types in most countries.

• Tier 2 A more complex approach that requires country-specific information on livestock characteristics and manure management practices. The Tier 2 approach is recommended when the data used to develop the default values do not correspond well with the country's livestock and manure management conditions. Because cattle characteristics vary significantly by country, it is recommended that countries with large cattle populations consider using the Tier 2 approach for estimating methane emissions from cattle and cattle manure. Similarly, because buffalo and swine manure management practices vary significantly by country, it is recommended that countries with large buffalo and swine populations consider using the Tier 2 approach for estimating methane emissions for manure from these animals.
Some countries for which livestock emissions are particularly important may wish to go beyond the Tier 2 method and incorporate additional country-specific information in their estimates. Although countries are encouraged to go beyond the Tier 2 approach presented below when data are available, these more complex analyses are only briefly discussed here. Table 4-1 summarises the recommended approaches for the livestock emissions included in this inventory.

T ABLE 4-1 D OMESTIC L IVESTOCK I NCLUDED IN THE M ETHODS Livestock Recommended Emissions Inventory Methods
Enteric Fermentation Manure Management Dairy Cattle Tier 2 a Tier 2 a Non-dairy Cattle Tier 2 a Tier 2 a
Buffalo Tier 1 Tier 2 a Sheep Tier 1 Tier 1
Goats Tier 1 Tier 1
Camels Tier 1 Tier 1
Horses Tier 1 Tier 1
Mules and Asses Tier 1 Tier 1
Swine Tier 1 Tier 2 a Poultry (Not Estimated) Tier 1

a The Tier 2 approach is recommended for countries with large livestock populations. Implementing the Tier 2 approach for additional livestock subgroups may be desirable when the subgroup emissions are a large portion of total methane emissions for the country.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.7 

### 4 . 2 . 3 I n v e n t o r y M e t h o d f o r M e t h a n e – T i e r 1 Approach This Tier 1 method is simplified so that only readily-available animal population data are needed to estimate emissions. Default emission factors are presented for each of the recommended population subgroups. Each step is discussed in turn.



### T IER 

### 1: S TEP 

### 1 – L IVESTOCK 

### P OPULATIONS

The average annual population of livestock is required for each of the livestock categories listed in Table 4-1. In some cases the population fluctuates during the year. For example, a census done before calving will give a much smaller number than a census done after calving. A representative average of the population is therefore needed. In the case of poultry and swine, the number of animals produced each year exceeds the annual average population because the animals live for less than 12 months. The population data can be obtained from the FAO Production Yearbook (FAO, 1990) or similar country-specific livestock census reports. The dairy cattle population is estimated separately from other cattle (see Table 4-2). Dairy cattle are defined in this method as mature cows that are producing milk in commercial quantities for human consumption. This definition corresponds to the dairy cow population reported in the FAO Production Yearbook. In some countries the dairy cattle population is comprised of two well-defined segments: high-producing "improved" breeds in commercial operations; and low-producing cows managed with traditional methods. These two segments can be combined, or can be evaluated separately by defining two dairy cattle categories. However, the dairy cattle category does not include cows kept principally to produce calves or to provide draft power. Low productivity multi-purpose cows should be considered as non-dairy cattle. Data on the average milk production of dairy cattle is also required. These data are expressed in terms of kilograms of whole fresh milk produced per year per dairy cow, and can be obtained from the FAO Production Yearbook or similar country-specific reports. If two or more dairy cattle categories are defined, the average milk production per cow is required for each category. Finally, the livestock populations must be described in terms of warm, temperate, or cool climates for purposes of estimating emissions from livestock manure. Data on the annual average temperature of the regions where livestock are managed should be used as follows:

• Areas with annual average temperatures less than 15 ° C are defined as cool.

• Areas with annual average temperatures from 15 ° C to 25 ° C inclusive are defined as temperate.

• Areas with annual average temperatures greater than 25 ° C are defined as warm. For each livestock population, the fraction in each climate should be estimated. These data can be developed from country-specific climate maps and livestock census reports. To the extent possible, the temperature data should reflect the locations where the livestock are managed. If necessary, data from nearby cities can be used. Table 4-2 summarises the animal population data that must be collected in Step 1.

## A GRICULTURE

4.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-2
A NIMAL P OPULATION D ATA C OLLECTED IN T IER 1 S TEP 1

Livestock Data Collected Population Milk Production Population By Climate (%) (# head) (kg/head/yr) Cool Temperate Warm Dairy Cattle Average Annual Population Milk Production per Head % Cool % Temp. % Warm

Non-dairy Cattle Average Annual Population Not Applicable (NA) % Cool % Temp. % Warm

Buffalo Average Annual Population (NA) % Cool % Temp. % Warm

Sheep Average Annual Population (NA) % Cool % Temp. % Warm

Goats Average Annual Population (NA) % Cool % Temp. % Warm

Camels Average Annual Population (NA) % Cool % Temp. % Warm

Horses Average Annual Population (NA) % Cool % Temp. % Warm

Mules and Asses Average Annual Population (NA) % Cool % Temp. % Warm

Swine Average Annual Population (NA) % Cool % Temp. % Warm

Poultry Average Annual Population (NA) % Cool % Temp. % Warm

Data can be obtained from the FAO Production Yearbook and country-specific livestock census reports. Climates are defined in terms of average annual temperature as follows: Cool = less than 15 ° C; Temperate = from 15 ° C to 25 ° C inclusive; Warm = greater than 25 ° C.



### T IER 

### 1: S TEP 

### 2 – E MISSION 

### F ACTORS The purpose of this step is to select emission factors that are most appropriate for the country's livestock characteristics. Default emission factors for enteric fermentation and manure management have been drawn from previous studies, and are organised by region for ease of use. The basis for the emission factors, described more fully under Tier 2, includes the following:

• Enteric Fermentation:

− Feed Intake : Feed intake is estimated based on the energy intake required by the animal for maintenance (the basic metabolic functions needed to stay alive) and production (growth, lactation, work, and gestation). The livestock characteristics required to estimate feed intake are taken from regional and country-specific studies and include: population structure (portion of adults and young), weight, rate of weight gain, amount of work performed, portion of cows giving birth each year, and milk production per cow.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.9 − Conversion of Feed Energy to Methane : The rate at which feed energy is converted to methane is estimated based on the quality of the feed consumed – low quality feed has a slightly higher methane conversion rate. Feed quality is assessed in terms of digestibility on a regional basis.

• Manure Management:

− Manure Production : Manure production is estimated based on feed intake and digestibility, both of which are used to develop the enteric fermentation emission factors.

− Methane Producing Potential : Methane producing potential (referred to as B o ) is the maximum amount of methane that can be produced from a given quantity of manure. The methane producing potential varies by animal type and the quality of the feed consumed. Reported measurements for selected animals are used.

− Methane Conversion Factor (MCF) : The MCF defines the portion of the methane producing potential (B o ) that is achieved. The MCF varies with the manner in which the manure is managed and the climate, and can theoretically range from 0 to 100 per cent. Manure managed as a liquid under hot conditions promotes methane formation and emissions. These manure management conditions have high MCFs, of 65 to 90 per cent. Manure managed as dry material in cold climates does not readily produce methane, and consequently has an MCF of about 1 per cent. Laboratory measurements were used to estimate MCFs for the major manure management techniques.

− Manure Management Practices : Regional assessments of manure management practices are used to estimate the portion of the manure that is handled with each manure management technique.
The data used to estimate the default emission factors for enteric fermentation and manure management are presented in Appendix A and Appendix B respectively, at the end of this section.
Table 4-3 shows the enteric fermentation emission factors for each of the animal types except cattle. As shown in the table, emission factors for sheep and swine vary for developed and developing countries. The differences in the emission factors are driven by differences in feed intake and feed characteristic assumptions (see Appendix A). Although point estimates are given for the emission factors, an uncertainty of about +20 per cent exists due to variations in animal management and feeding. Deviations from the emission factors can be larger than 20 per cent under specialised feeding or management conditions. Table 4-4 presents the enteric fermentation emission factors for cattle. A range of emission factors is shown for typical regional conditions. As shown in the table, the emission factors vary by over a factor of four on a per head basis. While the default emission factors shown in Table 4-4 are broadly representative of the emission rates within each of the regions described, emission factors vary among countries within regions. Also, as with the emission factors shown in Table 4-3, an uncertainty of about +20 per cent exists due to variations in animal management and feeding. Animal size and milk production are important determinants of emission rates for dairy cows. Relatively smaller dairy cows with low levels of production are found in Asia, Africa, and the Indian subcontinent. Relatively larger dairy cows with high levels of production are found in North America and Western Europe.

## A GRICULTURE

4.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-3 E NTERIC F ERMENTATION E MISSION F ACTORS ( KG PER HEAD PER YR ) Livestock Developed Countries Developing Countries
Buffalo 55 55 Sheep 8 5
Goats 5 5
Camels 46 46
Horses 18 18
Mules and Asses 10 10
Swine 1.5 1.0 Poultry Not Estimated Not Estimated
All estimates are ± 20 % Sources: Emission factors for buffalo and camels from Gibbs and Johnson (1993). Emission factors for other livestock from Crutzen et al. (1986).

Animal size and population structure are important determinants of emission rates for non-dairy cattle. Relatively smaller non-dairy cattle are found in Asia, Africa, and theIndian subcontinent. Also, many of the non-dairy cattle in these regions are young. Nondairy cattle in North America, Western Europe and Oceania are larger, and young cattle constitute a smaller portion of the population 3

. Select emission factors from Tables 4-3 and 4-4 by identifying the region most applicable to the country being evaluated. The data collected on the average annual milk production by dairy cows should be used to help select a dairy cow emission factor. If necessary, interpolate between dairy cow emission factors shown in the table using the data collected on average annual milk production per head. Table 4-5 shows the default manure management emission factors for each animal type except cattle, buffalo, and swine. Separate emission factors are shown for developed and developing countries, reflecting the general differences in feed intake and feed characteristics of the animals in the two regions. These emission factors reflect the fact that virtually all the manure from these animals is managed in dry manure management systems, including pastures and ranges, drylots, and daily spreading on fields (Woodbury and Hashimoto, 1993).

3 For each animal category, it is important to use the average weight of the animal during the year for estimating emissions. Because the weights of mature animals may fluctuate seasonally, a representative weight should be selected that considers conditions throughout the year. For growing animals, the average weight is generally less than the final (or end) weight of the animal at the end of the year. Growth rate statistics should be used to estimate the average weight during the year for purposes of estimating emissions.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.11 T ABLE 4-4 E NTERIC F ERMENTATION E MISSION F ACTORS FOR C ATTLE Regional Characteristics Cattle Type Emission Factor (kg/head/yr) Comments

**North America** : Highly productive commercialised dairy sector feeding high quality forage and grain. Separate beef cow herd, primarily grazing with feed supplements seasonally. Fast-growing beef steers/heifers finished in feedlots on grain. Dairy cows are a small part of the population. Dairy

Non-dairy 118

47 Average milk production of 6,700 kg/head/yr

Includes beef cows, bulls, calves, growing steers/heifers, and feedlot cattle. **Western Europe** : Highly productive commercialised dairy sector feeding high quality forage and grain. Dairy cows also used for beef calf production. Very small dedicated beef cow herd. Minor amount of feedlot feeding with grains. Dairy

Non-dairy 100

48 Average milk production of 4,200 kg/head/yr.
Includes bulls, calves, and growing steers/heifers. **Eastern Europe** : Commercialised dairy sector feeding mostly forages. Separate beef cow herd, primarily grazing. Minor amount of feedlot feeding with grains. Dairy

Non-dairy 81

56 Average milk production of 2,550 kg/head/yr.

Includes beef cows, bulls, and young.
**Oceania** : Commercialised dairy sector based on grazing. Separate beef cow herd, primarily grazing rangelands of widely varying quality. Growing amount of feedlot feeding with grains. Dairy cows are a small part of the population. Dairy

Non-dairy 68

53 Average milk production of 1,700 kg/head/yr.

Includes beef cows, bulls, and young.

**Latin America** : Commercialised dairy sector based on grazing. Separate beef cow herd grazing pastures and rangelands. Minor amount of feedlot feeding with grains. Growing non-dairy cattle comprise a large portion of the population. Dairy

Non-dairy 57

49 Average milk production of 800 kg/head/yr.

Includes beef cows, bulls, and young.
**Asia** : Small commercialised dairy sector. Most cattle are multi-purpose, providing draft power and some milk within farming regions. Small grazing population. Cattle of all types are smaller than those found in most other regions. Dairy

Non-dairy 56

44 Average milk production of 1,650 kg/head/yr.
Includes multi-purpose cows, bulls, and young **Africa and Middle East** : Commercialised dairy sector based on grazing with low production per cow. Most cattle are multi-purpose, providing draft power and some milk within farming regions. Some cattle graze over very large areas. Cattle of all types are smaller than those found in most other regions. Dairy

Non-dairy 36

32 Average milk production of 475 kg/head/yr.
Includes multi-purpose cows, bulls, and young

**Indian Subcontinent** : Commercialised dairy sector based on crop by-product feeding with low production per cow. Most bullocks provide draft power and cows provide some milk in farming regions. Small grazing population. Cattle in this region are the smallest compared to cattle found in all other regions. Dairy

Non-dairy 46

25 Average milk production of 900 kg/head/yr.
Includes cows, bulls, and young. Young comprise a large portion of the population

## A GRICULTURE

4.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-5 M ANURE M ANAGEMENT E MISSION F ACTORS ( KG PER HEAD PER YR ) Livestock Developed Countries Developing Countries Cool Temp. a Warm Cool Temp. a Warm Sheep 0.19 0.28 0.37 0.10 0.16 0.21
Goats 0.12 0.18 0.23 0.11 0.17 0.22
Camels 1.6 2.4 3.2 1.3 1.9 2.6
Horses 1.4 2.1 2.8 1.1 1.6 2.2
Mules and Asses 0.76 1.14 1.51 0.60 0.90 1.2 Poultry b 0.078 0.117 0.157 0.012 0.018 0.023 The range of estimates reflects cool to warm climates. Climate regions are defined in terms of annual average temperature as follows: Cool = less than 15 ° C; Temperate = 15 ° C to 25 ° C inclusive; and Warm = greater than 25 ° C. The Cool, Temperate and Warm regions are estimated using MCFs of 1 %, 1.5 % and 2 %, respectively. a Temp. = Temperate climate region. b Chickens, ducks, and turkeys. All estimates are +20 %. Sources: Emission factors developed from: feed intake values and feed digestibilities used to develop the enteric fermentation emission factors (see Appendix A); MCF, and B o values reported in Woodbury and Hashimoto (1993). All manure is assumed to be managed in dry systems, which is consistent with the manure management system usage reported in Woodbury and Hashimoto (1993).

The ranges of values shown in Table 4-5 reflect the range of Methane Conversion Factor values of 1 to 2 per cent. The higher value is appropriate for manure managed in warm climates, while the lower value is appropriate for manure managed in cooler and dryer climates. A middle value is assigned to temperate conditions. The uncertainty in the emission factors remains substantial, however, because field measurements are required to validate the laboratory measurements that form the basis for the MCFs used in the analysis. Appendix B, at the end of this section, summarises the data used to estimate the emission factors shown in Table 4-6. The climate data collected in Step 1 is used to select the emission factors from Table 4-6. A weighted average emission factor for each animal type is computed by multiplying the percentages of the animal populations in each climate region by the emission factor for each climate region. For example, if sheep in a developing country were 25 per cent in a temperate region and 75 per cent in a warm region, the emission factor for sheep would be estimated at about 0.2 kg/head/yr as follows: Emission Factor = (25% x 0.16) + (75% x 0.21) = 0.1975 kg/head/yr. An alternative way of handling these calculations is to sub-divide the category of sheep into two populations: one in warm and one in temperate region. Calculations could then be done separately and summed. Because the manure from cattle, buffalo, and swine is managed in a variety of ways, including both dry and liquid systems, the variations in manure management practices among regions and countries must be considered to develop emission factors for these animals. Table 4-6 presents emission factors based on regional manure management practices described in Safley et al. (1992).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.13 T ABLE 4-6 M ANURE M ANAGEMENT E MISSION F ACTORS FOR C ATTLE , S WINE AND B UFFALO

Regional Characteristics Livestock Type Emission Factor by Climate Region a (kg/head/yr)
Cool Temperate Warm
North America : Liquid-based systems are commonly used for dairy and swine manure. Non-dairy manure is usually managed as a solid and deposited on pastures or ranges. Dairy Cattle Non-dairy Cattle Swine 36 1 10 54 2 14 76 3 18

Western Europe : Liquid/slurry and pit storage systems are commonly used for cattle and swine manure. Limited cropland is available for spreading

manure. Dairy Cattle Non-dairy Cattle Swine Buffalo 14 6 3 3 44 20 10 8 81 38 19 17 Eastern Europe : Solid based systems are used for the majority of manure. About one-third of livestock manure is managed in liquid-based systems. Dairy Cattle Non-dairy Cattle Swine Buffalo 6 4 4 3 19 13 7 9 33 23 11 16
Oceania : Virtually all livestock manure is managed as a solid on pastures and ranges. About half of the swine manure is managed in anaerobic lagoons. Dairy Cattle Non-dairy Cattle Swine 31 5 20 32 6 20 33 7 20
Latin America : Almost all livestock manure is managed as a solid on pastures and ranges. Buffalo manure is deposited on pastures and ranges. Dairy Cattle Non-dairy Cattle Swine Buffalo 0 1 0 1 1 2 1 1 2 1 2 2
Africa : Almost all livestock manure is managed as a solid on pastures and ranges. Dairy Cattle Non-dairy Cattle Swine 1 0 0 1 1 1 1 1 2
Middle East : Over two-thirds of cattle manure is deposited on pastures and ranges. About one-third of swine manure is managed in liquid-based systems. Buffalo manure is burned for fuel or managed as a solid. Dairy Cattle Non-Dairy Cattle Swine Buffalo 1 1 1 4 2 1 3 5 2 1 6 5

Asia : About half of cattle manure is used for fuel with the remainder managed in dry systems. Almost 40% of swine manure is managed as a liquid. Buffalo manure is managed in drylots and deposited in pastures and ranges. Dairy Cattle Non-dairy Cattle Swine Buffalo 7 1 1 1 16 1 4 2 27 2 7 3

Indian Subcontinent : About half of cattle and buffalo manure is used for fuel with the remainder managed in dry systems. About one-third of swine manure is managed as a liquid. Dairy Cattle Non-dairy Cattle Swine Buffalo 5 2 3 4 5 2 4 5 6 2 6 5

a Cool climates have an average temperature below 15 ° C; temperate climates have an average temperature from 15 ° C to 25 ° C inclusive; warm climates have an average temperature above 25 ° C. All climate categories are not necessarily represented within every region. For example, there are no significant warm areas in Eastern or Western Europe. Similarly, there are no significant cool areas in Africa and the Middle East. See Appendix B for the derivation of these emission factors. Note: Significant buffalo populations do not exist in North America, Oceania, or Africa.

As shown in the table, the emission factors for dairy cattle range between 81 kg/head/ yr in warm parts of Western Europe to 0 kg/head/ yr

in cool parts of Latin America. The

## A GRICULTURE

4.14 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual emission factors for non-dairy cattle range between 38 kg/head/yr in warm parts of Western Europe to 1 kg/head/ yr in cool parts of North America and Latin America. In addition to climate, the range of emission factors is due to the manure management practices used in each region. For example, the emission factors for North American dairy cattle manure and European dairy and non-dairy cattle manure are relatively high because the manure is often managed using liquid systems that promote methane production. The emission factors for North American non-dairy cattle and for all animals in Africa and the Middle East are relatively low because their manure is generally managed using dry systems that do not promote methane production. To select emission factors from Table 4-6, first identify the appropriate region, such as Latin America. Within that region, identify the animal type of interest. For that animal type three values are given for the three climate regions. Compute a weighted average emission factor for the animal type by multiplying the percentages of the animal population in each climate region by the emission factor for each climate region. Appendix B summarises the estimates of manure management system usage and MCFs that underlie the emission factors in Table 4-6. As with the other manure management emission factors, there is substantial uncertainty in the estimates shown in Table 4-6 because field measurements are required to validate the laboratory measurements that form the basis for the MCFs used in the analysis, and because there is uncertainty and variability in the manner in which manure is managed in each region.



### T IER 

### 1: S TEP 

### 3 – T OTAL 

### E MISSION To estimate total emission the selected emission factors are multiplied by the associated animal population and summed. The emission estimates should be reported in gigagrams (Gg). Because the emission factors are reported in kilograms per head per year, the total emissions in Gg is estimated as follows for each animal category:
emission factor (kg/head/ yr ) x population (head) / (10 6 kg/Gg) = emissions Gg/ yr . As a point of reference, in 1990 total annual global methane emissions from domestic livestock enteric fermentation were of the order of 0.060 to 0.100 Gg (Gibbs and Johnson, 1993). Enteric fermentation emissions from countries with large populations of livestock may be on the order of 0.001 to 0.005 Gg per year. Countries with smaller populations of livestock would likely have emissions of less than 0.001 Gg per year. In 1990 total annual global methane emissions from manure management was on the order of 0.010 to 0.018 Gg (Woodbury and Hashimoto, 1993). Manure management emissions from countries where manure is managed in liquid-based systems may be on the order of 0.001 to 0.002 Gg per year. Countries where manure is not managed in liquid-based systems would likely have emissions of much less than 0.001 Gg per year.



### 4.2.4 Tier 2 Approach for Methane Emissions From Enteric Fermentation The Tier 2 approach is recommended for estimating methane emissions from enteric fermentation from cattle for those countries with large cattle populations. As contrasted with the Tier 1 method, this approach requires much more detailed information on the cattle population. Using this detailed information, more precise estimates of the cattle

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.15 emission factors are developed. When the Tier 2 method is used the default emission factors listed in Tier 1 for cattle are not used. This Tier 2 approach is similar to the August 1991 OECD method (OECD, 1991), with some modifications:

• The Blaxter and Clapperton (1965) equation is replaced with a recommended set of methane conversion rate "rules of thumb."

• Feed energy intake requirements for pregnancy have been added.

• The energy requirements required for grazing have been reduced based on newly available data from AAC (1990).

• The equations used to relate gross energy intake to net energy used by the animal have been made more general to fit a wider variety of feed conditions. The three steps outlined for Tier 1 are also used here.



### E NTERIC 

### F ERMENTATION 

### T IER 

### 2: S TEP 

### 1 – L IVESTOCK 

### P OPULATION To develop precise estimates of emissions, cattle should be divided into categories of relatively homogeneous groups. For each category a representative animal is chosen and characterised for the purpose of estimating an emission factor. Table 4-7 presents a set of recommended representative cattle types. Three main categories, Mature Dairy Cattle, Mature Non-dairy Cattle, and Young Cattle, are recommended as the minimum set of representative types. The subcategories listed should be used when data are available. In particular, the sub-population of cows providing milk to calves should be identified among non-dairy cattle because the feed intake necessary to support milk production can be substantial. In some countries the feedlot category is needed so that the implications of the high-grain diets can be incorporated.

T ABLE 4-7 R ECOMMENDED R EPRESENTATIVE C ATTLE T YPES Main Categories Subcategories Mature Dairy Cattle Dairy Cows used principally for commercial milk production Mature Non-dairy Cattle Mature Females:

• Beef Cows: used principally for producing beef steers and heifers

• Multiple-Use Cows: used for milk production, draft power, and other

uses
Mature Males:

• Breeding Bulls: used principally for breeding purposes

• Draft Bullocks: used principally for draft power Young Cattle Pre-Weaned Calves Growing Heifers, Steers/Bullocks and Bulls Feedlot-Fed Steers and Heifers on High-Grain Diets

## A GRICULTURE

4.16 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual For each of the representative animal types defined, the following information is required:

• annual average population (number of head);

• average daily feed intake (megajoules (MJ) per day and kg per day of dry matter); and

• methane conversion rate (percentage of feed energy converted to methane). Generally, data on average daily feed intake are not available, particularly for grazing animals. Consequently, the following data should be collected for estimating the feed intake for each representative animal type 4 :

• weight (kg);

• average weight gain per day (kg); 5

• feeding situation: confined animals; animals grazing good quality pasture; and animals grazing over very large areas;

• milk production per day (kg/day); 6

• average amount of work performed per day (hours/day);

• percentage of cows that give birth in a year; 7 and

• feed digestibility (%). 8 These data should be obtained from country-specific cattle evaluations. Some data, such as weight, weight gain, and milk production, may be available from production statistics. Care should be taken to use the live cattle weights, as contrasted with slaughter weights. Appendix A, at the end of this section, lists the data used to develop the default emission factors presented in Tier 1. Individual country data can be compared to the data presented in Appendix A to ensure that the data collected are reasonable. Data on methane conversion rates are also not generally available. The following rules of thumb are recommended for the methane conversion rates:

• Developed Countries. A 6 per cent conversion rate (±0.5 per cent) is recommended for all cattle in developed countries except feedlot cattle consuming diets with a large quantity of grain. For feedlot cattle on high grain diets a rate of 4 per cent (±0.5 per cent) is recommended. In circumstances where good feed is available (i.e., high digestibility and high energy value) the lower bounds of these ranges can be used. When poorer feed is available, the higher bounds are more appropriate.

• Developing Countries. Several recommendations are made for different animal management situations in developing countries:

4 In many, if not most, cattle management circumstances, the principal driving factors that affect feed intake are: weight, milk production and feed digestibility.
5 This may be assumed to be zero for mature animals.

6 Milk production is required for dairy cows and non-dairy cows providing milk to calves.

7 This is only relevant for mature cows.
8 Feed digestibility is defined as the proportion of energy in the feed that is not excreted in the faeces. Digestibility is commonly expressed as a percentage (%). Common ranges for feed digestibility for cattle are 50% to 60% for crop by-products andrangelands; 60% to 70% for good pastures, good preserved forages, and grainsupplemented forage-based diets; and 75% to 85% for grain-based diets fed in feedlots.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.17 − All dairy cows and young cattle are recommended to have a conversion rate of 6.0 per cent (±0.5 per cent). These cattle are generally the best-fed cattle in these regions.

− All non-dairy cattle, other than young stall-fed animals, consuming low-quality crop by-products, are recommended to have a conversion rate of 7.0 per cent (±0.5 per cent) because feed resources are particularly poor in many cases in these regions.

− Grazing cattle are recommended to have a conversion rate of 6.0 per cent (±0.5 per cent), except for grazing cattle in Africa, which are recommended to have a rate of 7.0 per cent (±0.5 per cent) because of the forage characteristics found in many portions of tropical Africa. These rules of thumb are a rough guide based on the general feed characteristics andproduction practices found in many developed and developing countries. Countryspecific exceptions to these general rules of thumb should be taken into consideration as necessary based on detailed data from cattle experts.



### E NTERIC 

### F ERMENTATION 

### T IER 

### 2: S TEP 

### 2 – E MISSION 

### F ACTORS

The emission factors for each category of cattle are estimated based on the feed intake and methane conversion rate for the category. Feed intake is estimated based on the feed energy requirements of the representative animals, subject to feed-intake limitations. The net energy system described in NRC (1984 and 1989) is recommended as the starting point for the estimates. Because the NRC system was developed for feeding conditions in temperate regions, several adjustments were made to avoid potential biases when applied to evaluate feed-energy intakes for tropical cattle (see Appendix C). Comparisons with alternative feeding systems (e.g., ARC, 1980) indicate that the emissions estimates are not sensitive to the feeding system used as the basis for making the estimates. The net energy system specifies the amount of feed energy required for the physiological functions of cattle, including maintenance, growth and lactation. Feed energy requirements for work have also been estimated, and are included in this analysis for the draft animals in developing countries. Energy requirements for pregnancy have also been added for the portion of cows that give birth in each year. The following information is required to estimate feed energy intakes:

• Maintenance Maintenance refers to the apparent feed energy required to keep the animal in energy equilibrium, i.e., there is no gain or loss of energy in the body tissues (Jurgens, 1988). For cattle, net energy for maintenance (NE m ) has been estimated to be a function of the weight of the animal raised to the 0.75 power (NRC, 1984):

E QUATION 1 NE m (MJ/day) = 0.322 x (weight in kg) 0.75 NRC (1989) recommends that lactating dairy cows be allowed a slightly higher maintenance allowance: NE m (MJ/day) = 0.335 x (weight in kg) 0.75 dairy cows}

## A GRICULTURE

4.18 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Feeding Additional energy is required for animals to obtain their food. Grazing animals require more energy for this activity than do stall-fed animals. The following energy requirements are added for this activity based on their feeding situation: 9

E QUATION 2 NE feed = Confined animals (pens and stalls): no additional NE m ; Animals grazing good quality pasture: 17 % of NE m ; and

Animals grazing over very large areas: 37 % of NE m .

• Growth The energy requirements for growth can be estimated as a function of the weight ofthe animal and the rate of weight gain. NRC (1989) presents formulae for largeand small-frame males and females, the estimates of which vary by about ± 25 per cent. The equation for large-frame females is recommended, which is about the average for the four types:

E QUATION 3 NE g (MJ/day) = 4.18 x {(0.035 W 0.75 x WG 1.119 ) + WG}

where:

W = animal weight in kilograms (kg); and WG = weight gain in kg per day.

The relationships for NE g were developed for temperate agriculture conditions, and may over-estimate energy requirements for tropical conditions, particularly for draft animals that may have a lower fat content in their weight gain (Graham, 1985). However, no data are available for improving the estimates at this time.

• Lactation Net energy for lactation has been expressed as a function of the amount of milk produced and its fat content (NRC, 1989):

E QUATION 4 NE l (MJ/day) = kg of milk/day x (1.47 + 0.40 x Fat %)
At 4.0 per cent fat, the NE l in MJ/day is about 3.1 x kg of milk per day.

• Draft Power Various authors have summarised the energy intake requirements for providing draft power (e.g., Lawrence, 1985; Bamualim and Kartiarso, 1985; and Ibrahim, 1985). The strenuousness of the work performed by the animal influences the energy requirements, and consequently a wide range of energy requirements have been estimated. The values by Bamualim and Kartiarso show that about 10 per cent of

9 The original OECD method recommended slightly higher energy additions. These revised figures are based on newly-published information in AAC (1990).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.19 NE m requirements are required per hour of typical work for draft animals. This value is used as follows:

E QUATION 5 NE draft (MJ/day) = 0.10 x NE m x hours of work per day

• Pregnancy Daily energy requirements for pregnancy are presented in NRC (1984). Integrating these requirements over a 281-day gestation period yields the following equation:

E QUATION 6 NE pregnancy (MJ/281-day period) = 28 x calf birth weight in kg
The following equation can be used to estimate the approximate calf birth weight as a function of the cow's weight: 10

E QUATION 7 Calf birth weight (kg) = 0.266 x (cow weight in kg) 0.79

Manipulating Equations 6 and 7, in conjunction with Equation 1, shows that the NE required for pregnancy is about 7.5 per cent of NE m for the range of cow sizes considered in this analysis. Therefore, a factor of 7.5 per cent of NE m is added to account for the energy required for pregnancy for the portion of cows giving birth each year. Based on these equations, each of the net energy components for each of the cattle categories can be estimated from the data collected in Step 1: weight in kilograms; feeding situation; weight gain per day in kilograms; milk production in kilograms of 4 per cent fatcorrected milk; number of hours of work performed per day; and portion that give birth. These net energy requirements must be translated into gross energy intakes. Also, by estimating the gross energy intake, the net energy estimates can be checked for reasonableness against expected ranges of feed intake as a percentage of animal weight. To estimate gross energy intake, the relationship between the net energy values and gross energy values of different feeds must be considered. This relationship can be summarised briefly as follows: Digestible Energy = Gross Energy - Faecal Losses Metabolisable Energy = Digestible Energy - Urinary and Combustible Gas Losses Net Energy = Metabolisable Energy - Heat Increment

-------------------------------------------------------------------------------------------------------

---- Net Energy = Gross Energy - Faecal Losses - Urinary and Combustible Gas Losses - Heat Increment

10 This species-specific equation from Robbins and Robbins (1979) was adjusted to the mean cow and calf weight of a typical beef breed of cattle. This adjustment increases the coefficient in the equation from 0.214 to 0.266.

## A GRICULTURE

4.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The quantitative relationship among these energy values varies among feed types. Additionally, the values depend on how the feeds are prepared and fed, and the level at which they are fed. For the purposes of this method, simplifying assumptions are used to derive a relationship between net energy and digestible energy that is reasonably representative for the range of diets typically fed to cattle. Gross energy intake is then estimated using this relationship and the digestibility data collected in Step 1. Given the digestibility of the feed (defined in Step 1), a general relationship between digestible energy and metabolisable energy can be used as follows (NRC, 1984):

E QUATION 8 Metabolisable Energy (ME) = 0.82 x Digestible Energy (DE)
Equation 8 is a simplified relationship; larger (smaller) methane conversion rates would tend to reduce (increase) the coefficient to values below (above) 0.82. NRC (1984) presents separate quantitative relationships between metabolisable energy and net energy used for growth versus net energy used for other functions. Using Equation 8, the NRC relationships can be re-arranged to quantify the ratio of NE to DE, as follows:

E QUATION 9 NE/DE = 1.123 - (4.092 x 10 -3 x DE%) + (1.126 x 10 -5 x (DE%) 2 ) - 25.4/DE%

E QUATION 10 NE g /DE = 1.164 - (5.160 x 10 -3 x DE%) + (1.308 x 10 -5 x (DE%) 2 ) - 37.4/DE%

where: NE/DE = the ratio of net energy consumed for maintenance, lactation, work and pregnancy to digestible energy consumed; NE g /DE = the ratio of net energy consumed for growth to digestible energy consumed; and DE% = digestible energy as percentage of gross energy, expressed in per cent (e.g., 65%).

Because the NRC (1984) relationships were developed based on diets with relatively high digestibilities (generally above 65 per cent), they may not be appropriate for the relatively low digestibility diets that are commonly found in tropical livestock systems. In particular, the non-linear nature of the relationships could appear to increase the estimates of feed intake for low-digestibility feeds. An apparent increase in feed intake would lead to an apparent increase in emissions estimates.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.21 Based on a review of other energy systems (e.g., ARC, 1980), a linear relationship between digestible energy and net energy was derived for digestibilities below 65 per cent as follows (see Appendix C):

E QUATION 11 NE/DE = 0.298 + (0.00335 x DE%)

E QUATION 12 NE g /DE = -0.036 + (0.00535 x DE%)

Given the estimates for feed digestibility (from Step 1) and equations 9 through 12, the gross energy intake (GE in MJ/day) can be estimated as follows:

E QUATION 13 

# ( ) 

# ( ) ( ) { } GE NE NE NE NE NE DE NE m feed l draft pregnancy

g 

### = + ++ + ×

+ 

       100 %
NE DE NE DE g

where: {NE/DE} is computed from equation 9 for digestibility greater than 65 per cent and from equation 11 for digestibility less than or equal to 65 per cent; {NE g /DE} is computed from equation 10 for digestibility greater than 65 per cent and from equation 12 for digestibility less than or equal to 65 per cent; and DE% is digestibility in per cent (e.g., 60%). To check the estimate of daily gross energy intake from Equation 13, the estimate can be converted in daily intake in kilograms by dividing by 18.45 MJ/kg. This estimate of intake in kilograms should generally be between 1.5 per cent and 3.0 per cent of the animal's weight. Using Equation 13 and the cattle data summarised in Appendix A, Gibbs and Johnson (1993) found that the intake estimates are consistent with expected intakes as a percentage of body weight and previously published values. For example, the intake estimate for Indian cattle is the equivalent of about 10,000 MJ per year of metabolisable energy (ME). Winrock (1978) estimates the average ME requirements for Indian cattle at 10,600 MJ per year. Similarly, the ME values implied for U.S.A dairy and non-dairy cows are 58,000 MJ and 31,000 MJ per year, respectively, which are similar to estimates of 62,000 MJ and 31,700 MJ derived in US EPA (1993). Consequently, for a diverse set of conditions, the intake estimates correspond to reasonably expected ranges from previously published estimates.

## A GRICULTURE

4.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual To estimate the emission factor for each cattle type, the feed intake is multiplied by the methane conversion rate (from Step 1) as follows:

E QUATION 14 Emissions (kg/yr) = [Intake (MJ/day) x Y m x (365 days/yr)] / [55.65 MJ/kg of methane]

where Y m is the methane conversion rate expressed in decimal form (such as 0.06 for 6 per cent). The result of this step of the method is an emission factor for each cattle type defined in Step 1.



### E NTERIC 

### F ERMENTATION 

### T IER 

### 2: S TEP 

### 3 – T OTAL 

### E MISSIONS To estimate total emissions the selected emission factors are multiplied by the associated animal population and summed. As described above under Tier 1, the emissions estimates should be reported in gigagrams (Gg).



### 4.2.5 Tier 2 Approach for Methane Emissions from Manure Management The Tier 2 approach provides a more detailed method for estimating methane emissions from manure management systems. The Tier 2 approach is recommended for countries with large cattle, buffalo and swine populations managed under confined conditions. Compared to the Tier 1 approach, this method requires additional detailed information on animal characteristics and the manner in which manure is managed. Using this additional information, emission factors are estimated that are specific to the conditions of the country, and the default emission factors from Tier 1 are not used. The Tier 2 approach is similar to the original OECD method described in OECD (1991). Improvements to the method have been made to incorporate more recent figures on methane conversion factors and to link the method more closely to the animal characteristic data collected for estimating enteric fermentation.



### M ANURE 

### M ANAGEMENT 

### T IER 

### 2: S TEP 

### 1 – L IVESTOCK 

### P OPULATIONS To develop precise estimates of emissions, the animals should be divided into relatively homogeneous groups. For each category a representative animal is chosen and characterised for purposes of estimating an emission factor. Suggested categories for cattle are discussed above under the enteric fermentation Tier 2 method and are summarised in Table 4-7. Similar categories can be used for buffalo. Categories for swine could include sows, boars, and growing animals (farrows to finishers). For each of the representative animal types defined, the following information is required:

• annual average population (number of head) by climate region (cool, temperate, and warm);

• average daily volatile solids (VS) excretion (kg of dry matter per day); 11

11 Volatile solids (VS) are the degradable organic material in livestock manure.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.23 • methane-producing potential (B o ) of the manure (cubic metres (m 3 ) of methane per kg of VS);

• manure management system usage (percentage of manure managed with each management system). Population data are generally available from country-specific livestock census reports. As described above under Tier 1, the portion of each animal population in cool, temperate, and warm climate regions is required. Often, data on average daily VS excretion are not available. Consequently, the VS values may need to be estimated from feed intake levels. The enteric fermentation Tier 2 method should be used to estimate feed intake levels for cattle and buffalo. 12 For swine, country-specific swine production data may be required to estimate feed intake. To develop the default emission factors for swine presented in Tier 1, average feed intake estimates for swine in developed and developing countries were used from Crutzen et al. (1986) (see Appendix B, at the end of this section). Once feed intake is estimated, the VS excretion rate is estimated as: 13

E QUATION 15 VS (kg dm/day) = Intake (MJ/day) x (1 kg/18.45 MJ) x (1 - DE%/100) x (1-ASH%/100)

where: VS = VS excretion per day on a dry weight basis;
dm = dry matter;
Intake = the estimated daily average feed intake in MJ/day;
DE% = the digestibility of the feed in per cent (e.g., 60%);
ASH% = the ash content of the manure in per cent (e.g., 8%).

For cattle, the DE% value used should be the same value used to implement Tier 2 for enteric fermentation. The ash content of cattle and buffalo manure is generally around 8 per cent. For swine, the default emission factors were estimated using 75 per cent and 50 per cent digestibility for developed and developing countries, respectively, and an ash content of 2 per cent and 4 per cent for developed and developing countries, respectively. Appendix B summarises the data used to estimate the VS excretion rates for cattle, buffalo, and swine. The maximum methane-producing capacity for the manure (B o ) varies by species and diet. Country-specific data should be used where feasible. A range of representative B o values

12 By using the enteric fermentation Tier 2 method to estimate feed intake, consistency is assured in the data underlying the emissions estimates for both enteric fermentation and manure management.

13 The energy density of feed is about 18.45 MJ per kg of dry matter. This value is relatively constant across a wide range of forage and grain-based feeds commonly consumed by livestock.

## A GRICULTURE

4.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual for cattle, buffalo, and swine populations were used to develop the default emission factors as follows (see Appendix B):

• Dairy Cattle

− Developed Countries: 0.24 m 3 /kg VS

− Developing Countries: 0.13 m 3 /kg VS

• Non-dairy Cattle

− Developed Countries: 0.17 m 3 /kg VS

− Developing Countries: 0.10 m 3 /kg VS

• Buffalo in all regions: 0.10 m 3 /kg VS

• Swine

− Developed Countries: 0.45 m 3 /kg VS

− Developing Countries: 0.29 m 3 /kg VS The portion of manure managed in each manure management system must also be collected for each representative animal type. Table 4-8 summarises the main types of manure management systems. The first four types in the table, pasture, daily spread, solid storage, and drylot, are all dry manure management systems. These systems produce little or no methane. The wet manure management systems, liquid/slurry, anaerobic lagoon, and pit storage, are the primary sources of manure methane emissions. To implement this Tier 2 method, at a minimum the proportion of manure managed in wet and dry systems must be estimated.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.25 T ABLE 4-8 M ANURE M ANAGEMENT S YSTEMS AND M ETHANE C ONVERSION F ACTORS (MCF S ) System MCF by Climate a Source Cool Temperate Warm Pasture/Range/Paddock: the manure from pasture and range grazing animals is allowed to lie as is, and is not managed. 1% 1.5% 2% b

Daily Spread: manure is collected in solid form by some means such as scraping. The collected manure is applied to fields regularly (usually daily). 0.1% 0.5% 1% b

Solid Storage: manure is collected as in the daily spread system, but is stored in bulk for a long period of time (months) before any disposal. 1% 1.5% 2% b

Drylot: in dry climates animals may be kept on unpaved feedlots where the manure is allowed to dry until it is periodically removed. Upon removal the manure may be spread on fields. 1% 1.5% 5% b

Liquid/Slurry: these systems are characterised by large concrete lined tanks built into the ground. Manure is stored in the tank for six or more months until it can be applied to fields. To facilitate handling as a liquid, water may be added to the manure. 10% 35% 65% b

Anaerobic Lagoon: anaerobic lagoon systems are characterised by flush systems that use water to transport manure to lagoons. The manure resides in the lagoon for periods from 30 days to over 200 days. The water from the lagoon may be recycled as flush water or used to irrigate and fertilise fields. 90% 90% 90% c

Pit Storage: liquid swine manure may be stored in a pit while awaiting final disposal. The length of storage time varies, and for this analysis is divided into two categories: less than one month or greater than one month. < 30 Days 5% 18% 33% b

> 30 Days 10% 35% 65% b Anaerobic Digester: the manure, in liquid or slurry form, is anaerobically digested to produce methane gas for energy. Emissions are from leakage and vary with the type of digester. 5-15% 5-15% 5-15% d

Burned for Fuel: manure is collected and dried in cakes and burned for heating or cooking. Emissions occur while the manure is stored before it is burned. Methane emission associated with the combustion of the manure are not considered here. Combustion-related emissions are estimated in the Traditional Biomass Fuels Section of the Energy chapter. 5-10% 5-10% 5-10% e

a Cool climates have an average temperature below 15 ° C; temperate climates have an average temperature from 15 ° C to 25 ° C inclusive; warm climates have an average temperature above 25 ° C. b Hashimoto and Steed (1993). c Safley et al., (1992) and Safley and Westerman (1992). d Yancun et al. (1985), Stuckey (1984) and Lichtman (1983). e Safley et al. (1992). The default emission factors presented in Tier 1 are based on manure management system usage data collected by Safley et al. (1992). Appendix B presents these data by region for cattle, buffalo and swine. Although the data in Appendix B can be used as defaults, country-specific data, e.g., obtained through a survey, would improve the basis for implementing the Tier 2 method. The resulting estimates must show the portion of manure from each animal type managed within each management system, by climate region.

## A GRICULTURE

4.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### M ANURE 

### M ANAGEMENT 

### T IER 

### 2: S TEP 

### 2 – E MISSION 

### F ACTORS

Emission factors are estimated for each animal type based using the data collected in Step 1 and the methane conversion factors (MCFs) for each manure management system. The MCF defines the portion of the methane producing potential (B o ) that is achieved. The MCF varies by manure management system and climate and can range between 0 and 100 per cent. Table 4-8 presents the latest available MCF estimates for the major manure management systems that have been developed.
To calculate the emission factor for each animal type, a weighted average methane conversion factor (MCF) is calculated using the estimates of the manure managed by waste system within each climate region. The average MCF is then multiplied by the VS excretion rate and the B o for the animal type. In equation form, the estimate is as follows:

E QUATION 16
EF i = VS i x 365 days/yr x B oi x 0.67 kg/m 3 x jK ∑ MCF jK x MS% ijK

where:
EF i = annual emission factor (kg) for animal type i (e.g., dairy cows); VS i = daily VS excreted (kg) for animal type i ; B oi = maximum methane producing capacity (m 3 /kg of VS) for manure produced by animal type i ; MCF jk = methane conversion factors for each manure management system j by climate region k ; and MS% ijk = fraction of animal type i 's manure handled using manure system j in climate region k

.


### M ANURE 

### M ANAGEMENT 

### T IER 

### 2: S TEP 

### 3 – T OTAL 

### E MISSIONS To estimate total emissions the selected emission factors are multiplied by the associated animal population and summed. As described above under Tier 1, the emissions estimates should be reported in gigagrams (Gg).



### 4.2.6 Beyond Tier 2 for Methane
The default values used in the Tier 1 and 2 methods were derived from available livestock and manure management data and are generally representative of regional conditions. Because livestock and manure management conditions can vary significantly across and within countries, the default values may not reflect adequately the conditions in a given country. Additionally, the variability of conditions has not been well characterised to date. The emissions estimates can be improved by going beyond the Tier 2 default data and collecting key country- or region-specific data. Data elements that would benefit from data collection initiatives (such as targeted surveys of major livestock types) include the following:

• Cattle weight In many regions the weights of cattle are not well quantified.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.27 • Feed intake Field data on feed intake would be valuable for validating the feed intake estimates made under Tier 2 for cattle.

• Manure production Field data on manure production by livestock would be valuable for validating the manure production estimates made under Tier 2.

• Manure management Field data on manure management system usage would improve the basis for making the estimates. Considerations of seasonal management practices could be incorporated into the data. In addition to these data collection initiatives, measurement programmes can be used to improve the basis for making the estimates. In particular, measurements of emissions from manure management systems under field conditions is needed. Techniques for making these measurements are described in IAEA (1992). Additionally, measurements of the maximum methane producing ability of manure (B o ) from livestock in tropical regions is needed. Additionally, new techniques are being deployed to measure emissions from cattle under field conditions (Johnson et al., 1993). Using these techniques, coefficients used in Tier 2 can be verified (such as the methane conversion rate) and the emissions estimates can be validated. Targeted assessments of tropical cattle populations would be most valuable.



### 4.2.7 Inventory Method for Nitrous Oxide - Overview
The method for estimating N 2 O emissions from manure management is described in detail in Section 4.5.3 of this Reference Manual, where emissions from several animal waste management systems are considered. All emissions of N 2 O taking place before the manure is added to soils are to be reported under ‘’Manure Management’’. These include emissions from anaerobic lagoons, liquid systems, solid storage and drylot, and ‘’other systems’’. Emissions resulting from manure used for fuel are included in the Energy Chapter. All manure-induced soil emissions are considered soil emissions here.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.29 

## Appendix A D a t a U n d e r l y i n g Met h a n e D e f a u l t E m i s s i on Factors For Enteric Fermentation This appendix presents the data used to develop the default emission factors for methane emissions from enteric fermentation. The detailed information presented for cattle and buffalo was developed in Gibbs and Johnson (1993). The Tier 2 method was implemented with these data to estimate the default emission factors for cattle and buffalo. Also presented are the summary data from Crutzen et al. (1986) that were used to estimate the emission factors for the other species.4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.31TABLEA-1DATA FOR ESTIMATINGENTERICFERMENTATIONEMISSIONFACTORS FORDAIRYCATTLERegionsWeightkgWeight Gainkg/dayFeeding Situation Milkkg/dayWorkhrs/day% PregnantDigestibility ofFeed %CH4Conversion%North Americaa6000 Stall Fed 18.4 090%65%6%Western Europe5500 Stall Fed 11.5 090%60%6%Eastern Europeb5500 Stall Fed 7.0 080%60%6%Oceaniac5000 Stall Fed 4.7 080%60%6%Latin Americad4000 Pasture/Range 2.2 080%60%6%Asiae3500 Stall Fed 4.5 080%60%6%Africa & Middle East2750 Stall Fed 1.3 067%60%6%Indian Subcontinentf2750 Stall Fed 2.5 050%55%6%a Based on estimates for the United Statesb Based on estimates for the former USSRc Based on estimates for Australia.d Based on estimates for Brazil.e Based on estimates for China.f Based on estimates for India.Source: Gibbs and Johnson (1993).AGRICULTURE4.32Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEA-2DATA FORESTIMATINGENTERICFERMENTATIONEMISSIONFACTORS FORNON-DAIRYCATTLETypeWeightkgWeight Gainkg/dayFeeding Situation Milkkg/dayWorkhrs/dayPregnant%Digestibility of Feed%CH4Conversion % Day Weighted PopulationMix %Emission Factorskg/head/yrNorth AmericaaMature Females 500 0.0 Pasture/Range 3.3 0.0 80% 60%6.0% 36%69Mature Males 800 0.0 Pasture/Range 0.0 0.0 0% 60%6.0% 2%75Calves on milk 100 0.9 Pasture/Range 0.0 0.0 0% NA0.0% 16%0Calves on forage 185 0.9 Pasture/Range 0.0 0.0 0% 65%6.0% 8%42Growing heifers/steers 265 0.7 Pasture/Range 0.0 0.0 0% 65%6.0% 17%47Replacement/growing 375 0.4 Pasture/Range 0.0 0.0 0% 60%6.0% 11%56Feedlot cattle 415 1.3 Stall Fed 0.0 0.0 0% 75%3.5% 11%37Western EuropeMature Males 600 0.0 Pasture/Range 0.0 0.0 0% 60%6.0% 22%60Replacement/growing 400 0.4 Pasture/Range 0.0 0.0 0% 60%6.0% 54%84Calves on milk 230 0.3 Pasture/Range 0.0 0.0 0% 65%0.0% 15%0Calves on forage 230 0.3 Pasture/Range 0.0 0.0 0% 65%6.0% 8%33Eastern EuropebMature Females 500 0.0 Pasture/Range 3.3 0.0 67% 60%6.5% 30%74Mature Males 600 0.0 Pasture/Range 0.0 0.0 0% 60%6.5% 22%65Young 230 0.4 Pasture/Range 0.0 0.0 0% 60% 6.0% 48%40OceaniacMature Females 400 0.0 Pasture/Range 2.4 0.0 67% 55%6.0% 51%63Mature Males 450 0.0 Pasture/Range 0.0 0.0 0% 55%6.0% 11%55Young 200 0.3 Pasture/Range 0.0 0.0 0% 55% 6.0% 38%39a Based on estimates for the United States.b Based on estimates for the former USSR.c Based on estimates for Australia.4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.33TABLEA-2 (CONTINUED)DATA FORESTIMATINGENTERICFERMENTATIONEMISSIONFACTORS FORNON-DAIRYCATTLETypeWeightkgWeight Gainkg/dayFeeding Situation Milkkg/dayWorkhrs/dayPregnant%Digestibility ofFeed %CH4Conversion%Day WeightedPopulation Mix %Emission Factorskg/head/yrLatin AmericadMature Females 400 0.0 Large Areas 1.1 0.067%60% 6.0% 37% 58Mature Males 450 0.0 Large Areas 0.0 0.00%60% 6.0% 6% 57Young 230 0.3Large Areas 0.0 0.00%60% 6.0% 58% 42AsiaeMature Females-Farming 325 0.0 Stall Fed 1.10.5533%55% 6.5% 27% 48Mature Females-Grazing 300 0.0 Pasture/Range 1.10.0050%60% 6.0% 9% 41Mature Males-Farming 450 0.0 Stall Fed 0.01.370%55% 6.5% 24% 58Mature Males-Grazing 400 0.0 Pasture/Range 0.00.000%60% 6.0% 8% 44Young 200 0.2 Pasture/Range 0.00.000%60% 6.0% 32% 31AfricaMature Females 200 0.0 Stall Fed 0.30.5533%55% 6.5% 13% 31Draft Bullocks 275 0.0 Stall Fed 0.01.370%55% 6.5% 13% 40Mature Females-Grazing 200 0.0 Large Areas 0.30.0033%55% 7.5% 6% 46Bulls - Grazing 275 0.0 Large Areas 0.00.000%55% 7.5% 25% 55Young 75 0.1 Pasture/Range 0.00.000%60% 6.0% 44% 14Indian SubcontinentfMature Females 125 0.0 Stall Fed 0.60.0033%50% 7.5% 40% 31Mature Males 200 0.0 Stall Fed 0.02.740%50% 7.5% 10% 41Young 80 0.1 Stall Fed 0.00.000%50% 6.0% 50% 17d Based on estimates for the Brazil.e Based on estimates for the China.f Based on estimates for India.Source: Gibbs and Johnson (1993)AGRICULTURE4.34Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEA-3DATA FORESTIMATINGENTERICFERMENTATIONEMISSIONFACTORS FORBUFFALOType WeightkgWeight Gainkg/dayFeeding Situation Milkkg/dayWorkhrs/dayPregnant%Digestibilityof Feed %CH4Conversion%DayWeighedPopulationMix%EmissionsFactorskg/head/yrIndian SubcontinentaAdult Males350 - 550 0.00Stall Fed0.00 1.370%55% 7.5 14% 55 - 77Adult Females250 - 450 0.00Stall Fed2.70 0.5533%55% 7.5 40% 57 - 80Young100 - 300 0.15Stall Fed0.00 0.000%55% 7.5 46% 23 - 50Other CountriesbAdult Males350 - 550 0.00Stall Fed0.00 1.370%55% 7.5 45% 55 - 77Adult Females250 - 450 0.00Stall Fed0.00 0.5525%55% 7.5 45% 45 - 67Young100 - 300 0.15Stall Fed0.15 0.000%55% 7.5 10% 23 - 50a Based on estimates for India.b Based on estimates for China.Source: Gibbs and Johnson (1993).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.35 T ABLE A-4 D ATA FOR E STIMATING E NTERIC F ERMENTATION E MISSION F ACTORS FOR O THER A NIMALS Animal Type Feed Intake (MJ/head/day) Methane Conversion Factor (%) Sheep Developed Countries 20 6% Developing Countries 13 6% Goats Developed Countries 14 5% Developing Countries 14 5% Camels Developed Countries 100 7% Developing Countries 100 7% Horses Developed Countries 110 2.5% Developing Countries 110 2.5% Mules/Asses Developed Countries 60 2.5% Developing Countries 60 2.5% Swine Developed Countries 38 0.6% Developing Countries 13 1.3% Poultry Developed Countries Not Estimated Developing Countries Sources: Feed intake and methane conversion for all animals from Crutzen et al (1986). Methane conversion for camels modified as in Gibbs and Johnson (1993).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.37 

## Appendix B Data Underlying Methane Default Emission Factors for Manure Management This appendix presents the data used to develop the default emission factors for methane emissions from manure management. The detailed information presented for cattle and buffalo was developed in Gibbs and Johnson (1993). The swine feed intake data are from Crutzen et al. (1986). The manure management system usage data and B o estimates are from Safley et al. (1992). The methane conversion factor (MCF) data are from Woodbury and Hashimoto (1993). The Tier 2 method was implemented with these data to estimate the default emission factors for cattle, buffalo, and swine. Also presented are the summary feed intake data from Crutzen et al. (1986) and the manure-related data from Safley et al. (1992) and Woodbury and Hashimoto (1993) that were used to estimate the emission factors for the other species.4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.39TABLEB-1FEEDINTAKE ANDMANUREPRODUCTION FORCATTLERegion Livestock Category Sub-PopulationMass(kg)FeedDigest(%)EnergyIntake(MJ/day)FeedIntake(kg/day)CategoryPopulation%Manure(kg/h/d dm)VS(kg/h/d)Bo(m3CH4/kgVS)North America Dairy Cattle Average 600 65% 299.5 16.2 100% 5.68 5.23 0.24Non-dairy Cattle Mature Females 500 60% 174.0 9.4 36% 3.77 3.47 0.17Mature Males 800 60% 189.3 10.3 2% 4.10 3.78 0.17Young on milk 100 NA NA NA 15% negligible negligible 0.17Young 185 65% 107.2 5.8 8% 2.03 1.87 0.17Young 265 65% 120.1 6.5 17% 2.28 2.10 0.17Young 375 60% 143.2 7.8 11% 3.10 2.86 0.17Feedlot 415 75% 161.8 8.8 11% 2.19 2.02 0.17Avg. Non-dairy Cattle 357 53% 128.0 6.9 100% 2.55 2.35 0.17Western Europe Dairy Cattle Average 550 60% 254.7 13.8 100% 5.52 5.08 0.24Non-dairy Cattle Mature Males 600 60% 152.5 8.3 22% 3.31 3.04 0.17Young Replacements 400 60% 149.8 8.1 55% 3.25 2.99 0.17Young Calves 230 65% 83.7 4.5 23% 1.59 1.46 0.17Avg. Non-dairy Cattle 405 61% 135.1 7.3 100% 2.88 2.65 0.17AGRICULTURE4.40Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-1 (CONTINUED)FEEDINTAKE ANDMANUREPRODUCTION FORCATTLERegionLivestockCategorySub-Population Mass(kg)FeedDigestibility(%)EnergyIntake(MJ/day)Feed Intake(kg/day)CategoryPopulation%Manure(kg/h/d dm)VS(kg/h/d)Bo(m3CH4/kgVS)Eastern EuropeDairy CattleAverage 550 60% 207.2 11.2100%4.49 4.130.24Non-dairy CattleMature Females 500 60% 172.9 9.430%3.75 3.450.17Mature Males 600 60% 152.5 8.321%3.31 3.040.17Young 230 60% 102.2 5.549%2.22 2.040.17Avg. Non-dairy Cattle 391 60% 134.4 7.3100%2.91 2.680.17OceaniaDairy CattleAverage 500 60% 174.1 9.4100%3.77 3.470.24Non-dairy CattleMature Females 400 55% 160.5 8.752%3.91 3.600.17Mature Males 450 55% 138.8 7.510%3.38 3.110.17Young 200 55% 98.6 5.338%2.41 2.210.17Avg. Non-dairy Cattle 330 55% 134.9 7.3100%3.29 3.030.17Latin AmericaDairy CattleAverage 400 60% 145.9 7.9100%3.16 2.910.13Non-dairy CattleMature Females 400 60% 148.0 8.037%3.21 2.950.10Mature Males 450 60% 144.0 7.85%3.12 2.870.10Young 230 60% 107.5 5.858%2.33 2.140.10Avg. Non-dairy Cattle 305 60% 124.4 6.7100%2.70 2.480.104AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.41TABLEB-1 (CONTINUED)FEEDINTAKE ANDMANUREPRODUCTION FORCATTLERegionLivestockCategorySub-Population Mass(kg)FeedDigestibility(%)EnergyIntake(MJ/day)Feed Intake(kg/day)CategoryPopulation%Manure(kg/h/d dm)VS(kg/h/d)Bo(m3CH4/kgVS)Africa & Middle EastDairy CattleAverage 275 60% 92.8 5.0100%2.01 1.850.13Non-dairy CattleMature Females 200 55% 73.2 4.013%1.79 1.640.10Mature Males Draft 275 55% 93.2 5.113%2.27 2.090.10Mature FemalesGrazing200 55% 93.6 5.15%2.28 2.100.10Mature Males Grazing 275 55% 112.3 6.125%2.74 2.520.10Young 75 60% 36.2 2.044%0.78 0.720.10Avg. Non-dairy Cattle 173 57% 70.6 3.8100%1.68 1.540.10AsiaDairy CattleAverage 350 60% 141.6 7.7100%3.07 2.820.13Non-dairy CattleMature FemalesFarming325 55% 113.2 6.127%2.76 2.540.10Mature FemalesGrazing300 60% 105.0 5.79%2.28 2.090.10Mature Males Farming 450 55% 134.9 7.324%3.29 3.030.10Mature Males Grazing 400 60% 112.5 6.18%2.44 2.240.10Young 200 60% 79.3 4.332%1.72 1.580.10Avg. Non-dairy Cattle 319 57% 106.8 5.8100%2.49 2.290.10IndianDairy CattleAverage Dairy Cow 275 55% 117.7 6.4100%2.87 2.640.13SubcontinentNon-dairy CattleMature Females 125 50% 63.8 3.540%1.73 1.590.10Mature Males 200 50% 83.7 4.510%2.27 2.090.10Young 80 50% 43.2 2.350%1.17 1.080.10Avg. Non-dairy Cattle 110 50% 55.5 3.0100%1.50 1.380.10Ash content estimated at 8%. Cattle characteristics from Gibbs and Johnson (1993).AGRICULTURE4.42Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-2FEEDINTAKE ANDMANUREPRODUCTION FORSWINE ANDBUFFALORegion LivestockCategorySub-Population Mass(kg)FeedDigestibility(%)EnergyIntake(MJ/day)Feed Intake(kg/day)CategoryPopulation%Manure(kg/h/ddm)VS(kg/h/d)Bo(m3CH4/kg VS)Developing Countries Swine Average28 50% 13.0 0.7 100%0.350.34 0.29Developed Countries Swine Average82 75% 38.0 2.1 100%0.510.50 0.45Indian SubcontinentaBuffalo Adult Males450 55% 134.5 7.3 14%3.283.02 0.10Adult Females350 55% 139.0 7.5 40%3.393.12 0.10Young200 55% 74.0 4.0 46%1.801.66 0.10Average295 55% 108.0 5.9 100%2.652.43 0.10Rest of WorldbBuffalo Adult Males450 55% 134.5 7.3 45%3.283.02 0.10Adult Females350 55% 114.0 6.2 45%2.782.56 0.10Young200 55% 74.0 4.1 10%1.801.66 0.10Average380 55% 119.0 6.5 100%2.912.68 0.10a Estimates based on data for India.b Estimates based on data for China.Ash content taken as 8% for buffalo and 2% and 4% for swine in developed and developing countries, respectively.Sources: Buffalo characteristics from Gibbs and Johnson (1993). Swine feed intake estimates from Crutzen et al. (1986).4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.43TABLEB-3MANUREMANAGEMENTEMISSIONFACTORDERIVATION FORDAIRYCATTLEClimate Manure Management System MCFsLagoon Liquid/SlurrySolidStorageDrylot Pasture/RangeDailySpreadDigesterBurnedfor FuelOtherCool 90% 10% 1% 1% 1%0.1%10%10% 1%Temperate 90% 35% 1.5% 1.5% 1.5% 0.5%10%10% 1%Warm 90% 65% 2% 5% 2% 1%10%10% 1%Region Dairy Cattle Characteristics Manure Management System Usage (MS%)EMISSIONFACTORSkg CH4/ hd / yrMassa(kg)Bo(m3CH4/kg Vs)VSb(kg/hd/day)CoolTemperateWarmNorth America 600 0.24 5.2 10% 23% 18% 5% 0% 37%0%0% 7% 36 54 76Western Europe 550 0.24 5.1 0% 40% 18% 0% 19% 20%0%2% 1% 14 44 81Eastern Europe 550 0.24 4.1 0% 18% 68% 0% 13% 1%0%0% 0% 6 19 33Oceania 500 0.24 3.5 16% 1% 0% 0% 76% 8%0%0% 0% 31 32 33Latin America 400 0.13 2.9 0% 1% 1% 0% 36% 62%0%0% 0% 0 1 2Africa 275 0.13 1.9 0% 0% 1% 0% 83% 5%0%6% 4% 1 1 1Middle East 275 0.13 1.9 0% 1% 2% 0% 80% 2%0%17% 0% 1 2 2Asia 350 0.13 2.8 4% 38% 0% 0% 20% 29%2%7% 0% 7 16 27Indian Subcontinent 275 0.13 2.6 0% 1% 0% 0% 27% 19%1%51% 0% 5 5 6a Average dairy cow mass for each region.b Average VS production for per head per day for the average dairy cow.Emission Factors (EF) for a climate region, k, are calculated as follows:EF = B VS 365 MS% MCFkojj=1all manure systemsjk×× × ×∑AGRICULTURE4.44Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-4MANUREMANAGEMENTEMISSIONFACTORDERIVATION FORNON-DAIRYCATTLEClimateManure Management System MCFsLagoon Liquid /SlurrySolidStorageDrylot Pasture /RangeDailySpreadDigester Burnedfor FuelOtherCool 90% 10% 1% 1% 1%0.1% 10% 10% 1%Temperate 90% 35% 1.5% 1.5% 1.5% 0.5% 10% 10% 1%Warm 90% 65% 2% 5% 2% 1% 10% 10% 1%Region Non-dairy CattleCharacteristicsManure Management System Usage (MS%)EMISSIONFACTORSkg CH4/ hd / yrMassa(kg)Bo(m3CH4/kg VS)VSb(kg/hd/day)CoolTemperateWarmNorth America 357 0.17 2.4 0% 1% 0% 14% 84% 0% 0% 0% 1%12 3Western Europe 405 0.17 2.7 0% 50% 0% 2% 38% 0% 0% 2% 8%620 38Eastern Europe 391 0.17 2.7 0% 28% 0% 0% 26% 0% 0% 0% 46%413 23Oceania 330 0.17 3.0 3% 0% 0% 6% 91% 0% 0% 0% 0%56 7Latin America 305 0.10 2.5 0% 0% 0% 0% 99% 0% 0% 0% 1%11 1Africa 173 0.10 1.5 0% 0% 0% 1% 95% 1% 0% 3% 0%01 1Middle East 173 0.10 1.5 0% 0% 0% 1% 79% 2% 0% 17% 2%11 1Asia 319 0.10 2.3 0% 0% 0% 46% 50% 2% 0% 2% 0%11 2Indian Subcontinent 110 0.10 1.4 0% 1% 0% 4% 22% 20% 1% 53% 0%22 2a Average non-dairy cow mass for each region.b Average VS production for per head per day for the average non-dairy animal.Emission Factors (EF) for a climate region, k, are calculated as follows:EF = B VS 365 MS% MCFko jj=1all manure systemsjk×× × ×∑4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.45TABLEB-5MANUREMANAGEMENTEMISSIONFACTORDERIVATIONFORBUFFALOClimate Manure Management System MCFsLiquid/SlurryDrylot Pasture/RangeDaily Spread DigesterBurned forFuelOtherCool10.0% 1.0% 1.0% 0.1% 10.0%10.0%1.0%Temperate 35.0% 1.5% 1.5% 0.5% 10.0%10.0%1.0%Warm65.0% 5.0% 2.0% 1.0% 10.0%10.0%1.0%Region Buffalo Characteristics Manure Management System Usage (MS%)EMISSIONFACTORSkg CH4/ hd / yrMassakgBom3CH4/kg VSVSbkg/hd/dayCoolTemperateWarmNorth America (not applicable)Western Europe 380 0.10 3.9 20% 79% 0% 0% 0%0%0% 3 8 17Eastern Europe 380 0.10 3.9 24% 0% 29% 0% 0%0%47% 3 9 16Oceania (not applicable)Latin America 380 0.10 3.9 0% 0% 99% 0% 0%0%1% 1 1 2Africa (not applicable)Middle East 380 0.10 3.9 0% 0% 20% 19% 0%42%19% 4 5 5Asia 380 0.10 3.9 0% 41% 50% 4% 0%5%0% 1 2 3IndianSubcontinent295 0.10 3.1 0% 4% 19% 21% 1%55%0% 4 5 5a Average buffalo mass for each region.b Average VS production for per head per day for the average buffalo.Emission Factors (EF) for a climate region, k, are calculated as follows:EF = B VS 365 MS% MCFko jj=1all manure systemsjk×× × ×∑AGRICULTURE4.46Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-6MANUREMANAGEMENTEMISSIONFACTORDERIVATION FORSWINEClimate Manure Management Systems MCFsLagoon Liquid/SlurrySolidStorageDrylot Pit<1 monthPit>1 monthDailySpreadDigester OtherCool 90% 10% 1% 1% 5% 10%0.1% 10% 1%Temperate 90% 35% 1.5% 1.5% 18% 35% 0.5% 10% 1%Warm 90% 65% 2% 5% 33% 65% 1% 10% 1%Region Swine Characteristics Manure Management System Usage (MS%)EMISSIONFACTORSkg CH4/ hd / yrMassakgBom3CH4/kg VSVSbkg/hd/dayCoolTemperateWarmNorth America 820.45 0.5 24% 1% 2% 16% 10% 26% 0% 0% 19% 10 14 18Western Europe 82 0.45 0.5 0% 0% 21% 2% 3% 73% 0% 0% 1% 3 10 19Eastern Europe 82 0.45 0.5 8% 0% 39% 14% 19% 19% 0% 0% 1% 4 7 11Oceania 820.45 0.5 54% 0% 3% 15% 0% 0% 0% 0% 28% 20 20 20Latin America 280.29 0.3 0% 8% 10% 41% 0% 0% 2% 0% 40% 0 1 2Africa 280.29 0.3 0% 6% 6% 87% 1% 0% 0% 0% 0% 0 1 2Middle East 28 0.29 0.3 0% 14% 0% 69% 0% 17% 0% 0% 0% 1 3 6Asia 280.29 0.3 0% 40% 0% 54% 0% 0% 0% 7% 0% 1 4 7IndianSubcontinent28 0.29 0.3 9% 22% 16% 30% 3% 0% 9% 8% 3% 3 4 6a Average swine mass for each region.b Average VS production for per head per day for the average swine.Emission Factors (EF) for a climate region, k, are calculated as follows:EF = B VS 365 MS% MCFko jj=1all manure systemsjk×× × ×∑4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.47TABLEB-7MANUREMANAGEMENTEMISSIONFACTORDERIVATION FOROTHERLIVESTOCKAnimal Animal Characteristics Manure Management SystemMCFsaEmission Factorsakg CH4/ hd / yrMass(kg)Digest(%)Intake/d(kg Feed)% Ash(Dry Basis)VS/day(kg VS)Bo(m3/kg VS)MCFCoolMCFTemperateMCFWarmCoolTemperateWarmSheep Developed Countries 43 60%1.08 8.0 0.40 0.19 1% 1.5% 2% 0.19 0.280.37Developing Countries 28 50%0.70 8.0 0.32 0.13 1% 1.5% 2% 0.10 0.160.21Goats Developed Countries 30 60%0.76 8.0 0.28 0.17 1% 1.5% 2% 0.12 0.180.23Developing Countries 30 50%0.76 8.0 0.35 0.13 1% 1.5% 2% 0.11 0.170.22Camels Developed Countries 217 50%5.42 8.0 2.49 0.26 1% 1.5% 2% 1.59 2.383.17Developing Countries 217 50%5.42 8.0 2.49 0.21 1% 1.5% 2% 1.28 1.922.56Horses Developed Countries 238 70%5.96 4.0 1.72 0.33 1% 1.5% 2% 1.39 2.082.77Developing Countries 238 70%5.96 4.0 1.72 0.26 1% 1.5% 2% 1.09 1.642.18Mule/AssesDeveloped Countries 130 70%3.25 4.0 0.94 0.33 1% 1.5% 2% 0.76 1.141.51Developing Countries 130 70%3.25 4.0 0.94 0.26 1% 1.5% 2% 0.60 0.901.19PoultrybDeveloped Countries 1.1 NRcNR NR 0.10 0.32 1% 1.5% 2% 0.078 0.1170.157Developing Countries NR NR NR NR0.02 0.24 1% 1.5% 2% 0.012 0.0180.023a The range of estimates reflects cool to warm climates. Cool climates have an average annual temperature below 15°C; temperate climates have an average annual temperature between 15°C and25°C; and warm climates have an average annual temperature above 25°C.b Poultry include chickens, ducks, and turkeys.c Not reported.Sources: Except for poultry, emission factors were developed from: feed intake values and feed digestibilities used to develop the enteric fermentation emission factors (see Appendix A); MCF, and Bovalues reported in Woodbury and Hashimoto (1993). All manure is assumed to be managed in dry systems, which is consistent with the manure management system usage reported in Woodburyand Hashimoto (1993). Emission factors for poultry are based on Safley et al. (1992) and Woodbury and Hashimoto (1993).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.49 

## Appendix C Derivation of Tier 2 Enteric Fermentation Equations For Methane This appendix summarises the derivation of the relationship between net energy (NE) and digestible energy (DE) that is used to estimate total feed-intake requirements for cattle. This derivation is drawn from Gibbs and Johnson (1993). As described in the main text, the relationship among the energy values of feed consumed by cattle can be summarised as follows: Digestible Energy = Gross Energy - Faecal Losses Metabolisable Energy = Digestible Energy - Urinary and Combustible Gas Losses Net Energy = Metabolisable Energy - Heat Increment

-------------------------------------------------------------------------------------------------------

---- Net Energy = Gross Energy - Faecal Losses - Urinary and Combustible Gas Losses - Heat Increment NRC (1984) presents the following quantitative relationships among these energy values: ME = 0.82 x DE (C.1)
NE m = (1.37 x ME) - (0.138 x ME 2 ) + (0.0105 x ME 3 ) - 1.12 (C.2)
NE g = (1.42 x ME) - (0.174 x ME 2 ) + (0.0122 x ME 3 ) - 1.65 (C.3)
where: DE = digestible energy in Mcal/kg (dry matter basis); ME = metabolisable energy in Mcal/kg (dry matter basis);
NE m = net energy for maintenance in Mcal/kg (dry matter basis); and
NE g = net energy for growth in Mcal/kg (dry matter basis). Using these relationships, the ratio of NE m and NE g to ME or DE can be derived as follows: NE/DE = 1.123 - (4.092 x 10 -3 x DE%) + (1.126 x 10 -5 x (DE%) 2 ) - 25.4/DE% (C.4)
NE g /DE = 1.164 - (5.160 x 10 -3 x DE%) + (1.308 x 10 -5 x (DE%) 2 ) - 37.4/DE% (C.5)
where: NE/DE = the ratio of net energy consumed for maintenance, lactation, work and pregnancy to digestible energy consumed;
NE g /DE = the ratio of net energy consumed for growth to digestible energy consumed; and DE% = digestible energy as percentage of gross energy, expressed in per cent (e.g., 65%).

## A GRICULTURE

4.50 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Graph C-1 shows the relationships in graphical form. As shown in the graph, the ratio of NE to DE is non-linear, with an increasing slope with decreasing DE. These relationships imply that at lower values of DE, cattle are able to recover a decreasing portion of the energy to use for maintenance or growth. For the purpose of estimating methane emissions from cattle, applying these relationships to cattle consuming relatively low-quality feeds (such as cattle in many tropical countries) may be inappropriate because the relationships were developed based on analyses of the higher-quality feeds typically found in the United States temperate agriculture system. Consequently, the experimental basis for extrapolating the non-linear relationships to low levels of DE is not very strong. In examining other energy systems, it is seen that they also indicate that the rate of net energy retention declines at lower values of digestible energy. Unlike the NRC system, however, many imply a linear relationship between NE and DE. The UK energy system (ARC, 1980), which is typical of the energy systems used in Europe, has a slope for the linear NE m :DE relationship that is similar to the slope of the non-linear NRC relationship in the range of 65-70 per cent digestibility. In the same way, the slope of the UK NE g :DE relationship is similar to the slope of the non-linear NRC relationship in the range of 60-65 per cent digestibility. To avoid possible biases in estimating feed-intake requirements in this study, the relationships were extrapolated linearly for DE values below 65 per cent using the average slopes of the NRC relationships between 60 and 70 per cent DE. The derived equations are as follows: NE/DE = 0.298 + 0.00335 x DE%(C.6)
NE g /DE = -0.036 + 0.00535 x DE%(C.7) Graph C-2 shows the extrapolated linear relationships along with the non-linear estimates. As expected, the linear extrapolations fall above the original non-linear estimates. The implication of making this adjustment to the NRC (1984) relationship for the global emissions estimate is relatively minor. Gibbs and Johnson (1993) report that using the non-linear relationship to estimate global emissions from cattle increases the 1990 emissions estimate by 1000 Gg, from 58,100 Gg to 59,100 Gg. Considering the wide range of factors that contribute to uncertainty in the estimates, including characterisation of animal populations, this adjustment has a minor influence on the estimates.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.51 Graph C-1: NRC NE:DE Relationship 44 48 52 56 60 64 68 72 76 

# NE to DE Ratio by DE

Digestible Energy Derived from NRC (1984)
0.54 0.52 0.50 0.48 0.46 0.44 0.42 0.40 0.38 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.20 0.18 NEg NEm

## A GRICULTURE

4.52 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Graph C-2: Linear Extrapolation Of The NRC NE:DE Relationship



### 44 48 52 56 60 64 68 72 76 

# NE to DE Ratio by DE

Digestible Energy (%) 0.54 0.52 0.50 0.48 0.46 0.44 0.42 0.40 0.38 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.20 0.18 NEm

NEg

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.53 

## 4.3 Methane Emissions from Rice Cultivation: Flooded Rice Fields

4.3.1 Overview Anaerobic decomposition of organic material in flooded rice fields produces methane (CH 4 ), which escapes to the atmosphere primarily by diffusive transport through the rice plants during the growing season. Upland rice fields, which are not flooded and therefore do not produce significant quantities of CH 4 , account for approximately 10 per cent of the global rice production and about 15 per cent of the global rice area under cultivation. The remaining area is grown for wetland rice, consisting of irrigated, rainfed, and deepwater rice. The global wetland rice area harvested annually in the early 1980s was about 123.2 million hectares (total harvested area including upland rice is 144 Mha), over 90 per cent of which was in Asia (Neue et al
., 1990). 14 Of the wide variety of sources of atmospheric CH 4 , rice paddy fields are considered one of the most important. The Intergovernmental Panel on Climate Change (IPCC
, 1996) estimated the global emission rate from paddy fields at 60 Tg/yr, with a range of 20 to 100 Tg/yr. This is about 5-20 per cent of the total emission from all anthropogenic sources. This figure is mainly based on field measurements of CH 4 fluxes from paddy fields in the United States, Spain, Italy, China, India, Australia, Japan and Thailand. The measurements at various locations of the world show that there are large temporal variations of CH 4 fluxes and that the flux differs markedly with soil type and texture, application of organic matter and mineral fertiliser (Neue and Sass, 1994). The wide variations in CH 4 fluxes also indicate that the flux is critically dependent upon several factors including climate, characteristics of soils and paddy, and agricultural practices, particularly water regime. The parameters that affect methane emissions vary widely both spatially and temporally. Multiple year data sets near the same location and under similar conditions can lead to substantial differences in seasonal methane emission levels, making it difficult to establish a single number as the methane emission level from a field, let alone at a regional or country level. Thus, at the current level of understanding, a reported range in methane emission levels for a country is more realistic than a single number. Methane production processes The major pathways of CH 4 production in flooded soils are the reduction of CO 2 with H 2 , with fatty acids or alcohols as hydrogen donor, and the transmethylation of acetic acid or methanol by methane-producing bacteria (Takai, 1970; Conrad 1989). In paddy fields, the kinetics of the reduction processes are strongly affected by the composition and texture of soil and its content of inorganic electron acceptors. The period between flooding of the soil and the onset of methanogenesis can apparently be different for the various soils. However, it is unclear if soil type also affects the rates of methanogenesis and CH 4 emission when steady state conditions have been reached (Conrad, 1989).

14 The term "harvested area" has a different meaning from "cultivated area" in that the former accounts for double and triple cropping. For example, if a country has 10 million hectares of land under rice cultivation, all of which are double-cropped (i.e., two crops of rice are grown on each hectare each year), then this country has 20 million hectares of rice area harvested annually.

## A GRICULTURE

4.54 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The redox 15 potential is one important factor for production of CH 4 in soils. The Eh, or electron activity, of the soil gradually decreases after flooding. Patrick (1981) demonstrated that the redox potential of a soil must be below approximately -150 mV in order to have CH 4 production. Yamane and Sato (1964) also showed that the evolution of CH 4 from flooded paddy soils did not commence until the Eh fell below -150 mV. Carbon substrate and nutrient availability are also important factors. Application of rice straw to paddy fields significantly increases the CH 4 emission rate compared with application of compost prepared with rice straw or chemical fertiliser.Soil temperature is known to be an important factor in affecting the activity of soil microorganisms. This is to a certain extent related to the soil moisture content because both the heat capacity and the heat conductivity are lower for a dry soil than for a wet soil. Yamane and Sato (1961) have already found that CH 4 formation reached a maximum at 35 o C in waterlogged alluvial soils. The rate of methane formation was very small below 20 o C.
Because the conversion rate of substrate to CH 4 depends on the temperature, it is generally observed that the momentary local emission of CH 4 from the soil to the atmosphere depends on the temperature. However, the dependence of the seasonally integrated emissions of CH 4 on temperature is much weaker. That emission depends primarily on the total input of organic substrate: although the temperature determines the time it takes to convert the substrate to CH 4 , that time is generally short compared to a season. Thus the methodology proposed here will be based on the seasonally integrated CH 4 emission, whose temperature dependence can be neglected in first approximation. It is generally recognised that CH 4 formation is only efficient in a narrow pH range around neutrality (pH from 6.4 to 7.8). The effect of flooding is to increase the pH in acid soil, while it decreases the pH in alkaline soil. The increase of pH in acid soils is mainly due to the reduction of acidic Fe 3+ to Fe 2+ which simultaneously reduces the Eh. The addition of nitrate as chemical fertiliser to flooded soils may suppress the production of CH 4 , because nitrate acts, as well as Fe 3+ , Mn 4+ , as a terminal electron acceptor in the absence of molecular oxygen during anaerobic respiration, and poises the redox potential of soils at values such that the activity of strict anaerobes is prevented. The addition of sulphate may also inhibit methane production for similar reasons as nitrate. There are three processes of CH 4 release into the atmosphere from rice fields. Diffusion loss of CH 4 across the water surface is the least important process. Methane loss as bubbles (ebullition) from paddy soils is a common and significant mechanism, especially if the soil texture is not clayey. During land preparation and initial growth of rice, ebullition is the major release mechanism. The third process is CH 4 transport through rice plants, which has been reported as the most important phenomenon (Seiler et al., 1984; Schütz et al., 1989b). Many researchers reported that more than 90 per cent of total CH 4 emitted during the cropping season is released by diffusive transport through the aerenchyma system of the rice plants and not by diffusion or ebullition. Emission through rice plant, may be expected to show great seasonal variations as a function of changes in soil conditions and variations in plant growth.

15 Redox (Eh) refers to oxidation-reduction, two processes that take place simultaneously. Oxidation is the loss of an electron by an atom, and reduction is the gain of an electron by an atom.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.55 Methane emission rates are also a function of the partial pressure of CH 4 in the soil. Part of the CH 4 produced in the soil is consumed in the oxidised rhizosphere of rice roots or in the oxidised soil-floodwater interface. It is known that soil methanotrophic bacteria can grow with CH 4 as their sole energy source, and other soil bacteria, such as Nitrosomonas species are also able to consume CH 4 (Conrad, 1993). Methane is also leached to ground water, as a small part dissolves in water. Therefore a reduction in soil methane does not necessarily mean that all this CH 4 has been emitted into the atmosphere.

Global emissions from rice fields The total harvested area of rice has increased from 86 Mha in 1935 to 144 Mha in 1985, which means an annual average increase of 1.05 per cent. The average annual increase was 1.23 per cent between 1959 and 1985. However, in the last few years, the rate of expansion of the total rice acreage has decreased (Minami, 1994). Table 4-9 provides a summary of measured emissions at a number of specific research sites around the world. It should be noted that methane fluxes from paddy rice fields vary substantially from day to day, and during a day (e.g., day and night). The data presented here are based on frequent measurements which capture the diurnal variations, and variations over the growing season. Based on area and production statistics, with average emission values, a number of researchers have estimated global emissions from rice.

## A GRICULTURE

4.56 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-9 R EPRESENTATIVE M ETHANE E MISSIONS F ROM R ICE P ADDY F IELDS I N V ARIOUS L OCATIONS OF THE W ORLD

Country Location Range of CH 4 flux mg/m 2 /hr Season total
g/m 2 Experimental Treatment Reference

Australia Griffith 2.8 10

- NGGIC, 1996
China Beijing 14.6 - 48.9 27 - 91 OM, WM Chen et al., 1993 Beijing 9.4 - 26.8 12 - 39 MF, OM, WM Yao and Chen, 1994a, 1994b Beijing 1.9 - 48.9 5.3 - 100.9 MF, OM, SO, WM Shao, 1993 Hangzhou, Zhejiang 6.9 - 50.6 14 - 82 MF, OM, SE Wassmann et al., 1993a Nanjing, Jiangsu 2.6 - 14.3 6 - 34 MF, OM, WM Chen et al., 1993 Taoyuan, Hunan 6.5 - 56.2 12 - 115 MF, OM, SE Wassmann et al., 1993b
Tuzhu, Sichuan 58.0 167 Khalil et al., 1991 Wuxian, Jiangsu 3.2 - 6.2 10 - 19 CU, MF, OM, SE, WM Cai et al., 1994
India Allahabad, Uttar Pradesh 0.2 0.5 NAV Mitra, 1992 Barrackpore, West Benegal 0.7, 20.2 1.8, 6.3 NAV Mitra, 1992

Cuttack, Orissa 2.7-7.2 7-19 CU Mitra, 1992
Faizabad, Uttar Pradesh 0.8 2 NAV Mitra, 1992 Garagacha, West Benegal 11 29 NAV Mitra, 1992

Jorhat, Assam 18.1 46 NAV Mitra, 1992 Kalyani, West Bengal 4.1 10.8 NAV Mitra, 1992 Koirapur, West Bengal 6.1 19 NAV Mitra, 1992
Madras, Tamil Nadu 5.8 11 NAV Mitra, 1992
New Delhi 0.02-0.21 0.06-0.58 MF Mitra, 1992 Purulia, West Bengal 4.2 11 NAV Mitra, 1992
Trivandrum, Kerala 5.1 9 NAV Mitra, 1992
Indonesia Taman Bogo, Lampung 18.0 - 27.1 31 - 47 MF, OM Nugroho et al., 1994a Taman Bogo, Lampung 17.9 - 31.7 30 - 50 MF, OM Nugroho et al., 1994b Sukamandi, West Java 8.7 - 20.2 19 - 44 WM, CU Husin et al., 1995 Italy Vercelli 5 - 28 18 - 75 MF, OM Schütz et al., 1989a

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.57 T ABLE 4-9 ( CONT .) R EPRESENTATIVE M ETHANE E MISSIONS F ROM R ICE P ADDY F IELDS I N V ARIOUS L OCATIONS OF THE W ORLD

Country Location Range of CH 4 flux mg/m 2 /hr Season total
g/m 2 Experimental Treatment Reference

Japan Kawachi 16.3 45 Yagi and Minami, 1990a; Minami, 1994
Mito 1.2 - 4.1 4 - 13 MF, OM Yagi and Minami, 1990a; Minami, 1994 Ryugasaki 2.8 - 15.4 11 - 28 MF, OM Yagi and Minami, 1990a; Minami, 1994, Ryugasaki 1.9 - 7.9 7 - 12 WM Yagi and Minami, 1990a; Minami, 1994 Taya 7.0 26 Yagi and Minami, 1990a; Minami, 1994
Tsukuba 0.2 - 0.4 <1.1 OM Yagi and Minami, 1990a; Minami, 1994
Korea Suwon 0.66 - 4.55 9 - 60 OM, WM Shin et al., 1995 Philippines Los Banos 0.8 - 18.5 2 - 42 MF, OM Neue et al., 1994
Los Banos 3.3 - 7.9 7 - 19 SE Wassmann et al., 1994 Spain Savilla 4 12 Seiler et al., 1984
Thailand Ayutthaya 3.3 - 7.9 13 - 20 CU, OM, WM Siriratpiraya, 1990 Bang Khen 4.3 - 21.7 16 - 55 SE Minami, 1994; Yagi et al., 1994b Chai Nat 1.6 4 Minami, 1994 Yagi et al., 1994b Chiang Mai 3.7 - 5.5 9 - 13 MF, OM Jermsawatdipong et al., 1994 Chiang Mai 9.0 - 9.5 20 - 21 CU Siriratpiriya et al 1995 Khlong Luang 3.8 8 Minami, 1994 Yagi et al., 1994b Khon Kaen 23.0 76 Minami, 1994; Yagi et al., 1994b

## A GRICULTURE

4.58 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-9 ( CONT .) R EPRESENTATIVE M ETHANE E MISSIONS F ROM R ICE P ADDY F IELDS I N V ARIOUS L OCATIONS OF THE W ORLD

Country Location Range of CH 4 flux mg/m 2 /hr Season total
g/m 2 Experimental Treatment Reference

Thailand (cont.) Nakompathom 9.4-12.0 25-32 SE Tomprayoon et al., 1991

Pathumthani 1.9 - 4.6 5 - 11 MF, OM Jermsawatdipong et al., 1994
Phitsanulok 6.6 - 7.2 17 - 18 SE Katoh et al, 1995 Phrae 16.6 - 22.2 51 - 69 SE Minami, 1994; Yagi et al., 1994b Ratchaburi 3.2 - 42.5 9 - 117 MF, OM Jermsawatdipong et al., 1994 San Pa Tong 10.4 - 16.1 25 - 40 SE Minami, 1994; Yagi et al., 1994b Surin 15.0 - 24.5 41 - 66 MF, OM Jermsawatdipong et al., 1994 Surin 13.3 41 Jermsawatdipong et al., 1994 Suphan Buri 19.5 - 32.2 51 - 75 SE Minami, 1994; Yagi et al., 1994b
USA Beaumont, Texas 2.5 - 23.5 5 - 36 OM, SO Sass et al., 1990, 1991a, 1991b
Beaumont, Texas 0.6 - 6.3 1 -15 WM Sass et al., 1992 Crowley, Louisiana 10.2 - 17.9 21 - 37 MF Lindau et al., 1991 Crowley, Louisiana 12.6 - 85.0 22 - 149 MF, OM, SE Lindau and Bollich, 1993 Crowley, Louisiana 27 - 99 60 - 220 MF Lindau, 1994 Davis, California 3.4 - 10.4 18 Cicerone et al., 1983, 1992 Knights Landing, California 0.5 - 18.8 1 - 58 MF, OM Cicerone et al., 1992

Experimental treatment: CU - cultivars, MF - fertilisers, OM - organic matters, SE - seasons (early and late rices, or dry and rainy seasons), SO - soil types, WM - water management. NAV = not available Source: Modified from K Minami (1995)

Global emissions of CH 4 from rice paddies reported by several researchers are summarised in Table 4-10. Extrapolation of emission rates to a global scale is very difficult, because the effects of variations in agricultural practices, number of crops per year, soil types and other factors discussed above are uncertain. The IPCC (IPCC, 1996) presented a candidate list of CH 4 sources to the atmosphere as annual release rates. The total annual source is constrained by the observed rate of atmospheric increase of concentrations and by the estimated atmospheric lifetime to be 535 Tg CH 4 /yr. Rice paddies are listed as a source of 60 ± 40 Tg CH 4 /yr.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.59 T ABLE 4-10 R EPRESENTATIVE G LOBAL ANNUAL METHANE EMISSIONS FROM RICE FIELDS AS ESTIMATED BY DIFFERENT AUTHORS * Reference Estimate (Tg CH 4 /yr) Koyama (1964) Ehhalt and Schmidt (1978) Cicerone and Shetter (1981) Khalil and Rasmussen (1983) Seiler et al (1984) Blake and Rowland (1988) Crutzen (1985) Holzapfel-Pschorn and Seiler (1986) Cicerone and Oremland (1988) Schütz et al. (1989a) Aselman and Crutzen (1989) Schütz et al. (1990) Wang et al. (1990) Neue et al. (1990) Bouwman (1990) Yagi and Minami (1990b) IPCC (1990) Minami(1994) Sass (1994) Parashar et al (1994) IPCC (1996) 190
280
59
95
35-59
142-190
120-200
70-170
60-170
50-150
60-140
50-150
60-120
25-60
53-114
22-73
25-170
12-113
25-54

20
20-100 Source: Modified from K. Minami (1994)

## A GRICULTURE

4.60 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.3.2 Methods For Estimating Emissions Emissions of methane from rice fields can be represented as follows:

E QUATION 1
F c = EF × A × 10 -12

where:
F c = estimated annual emission of methane from a particular rice water regime and for a given organic amendment, in Tg per year; EF = methane emission factor integrated over integrated cropping season, in g/m 2;
A = annual harvested area cultivated under conditions defined above. It is given by the cultivated area times the number of cropping seasons per year, i.e., in m 2 /yr.

The seasonally integrated emission factor is evaluated from direct field measurements of methane fluxes for a single crop. In practice, it will be necessary to calculate the total annual emissions from a country as a sum of the emissions over a number of conditions. Total rice production can be divided into subcategories based on different biological, chemical and physical factors that control methane emissions from rice fields. In large countries, this may include different geographic regions. To account for the different conditions, F is defined as the sum of Fc (see Equation 1). This approach to emissions estimation can be represented as follows:

E QUATION 2
F = ∑ i ∑ j ∑ k EF ijk x 10 -12

where:

• ijk: are categories under which methane emissions from rice fields may vary. For instance, i may represent water levels in the rice fields such as fields inundated for the duration of the growing season (flooded regime) or fields under water only intermittently. This occurs either under managed irrigation when water is not readily available or when rains do not maintain flooded conditions throughout the growing season (intermittent regime) as given in Table 4-12. j, k, may represent water regimes modified by other factors like organic inputs, soil textures, fertilisation regimes under each of the conditions represented by the index i, and so on. As more factors are identified, more categories need to be included. Inclusion of additional parameters should lead to an improvement of the estimate of the total emissions. The summation should include all cropping seasons. The factors clearly identified by field experiments as being most important are (1) water regime with inorganic fertilisers (except sulphate-containing inorganic fertilisers which inhibit CH 4 production); (2) organic fertiliser applications; (3) soil type, and soil texture; (4) cultivar; and (5) agricultural practices such as direct seeding or transplanting. Data

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.61 show that in continuously flooded fields, some types of organic fertilisers and certain cultivars lead to higher emissions compared to rice grown without organic amendments or intermittent or managed irrigation in which the fields are not continuously inundated and only where chemical fertilisers are used. At present there are insufficient data to incorporate most of these factors. Nonetheless, the estimates can be improved substantially by incorporating the current knowledge on water regimes, organic amendments and soil types etc. For some countries the effects of organic fertiliser can be included.



### 4.3.3 Summary of Recommended Method

Basic Method

Data on rice cultivation under different water management techniques should be available from most of the important rice-producing countries. Therefore, the basic method for estimating emissions from each country includes estimates based on rice ecosystems (Kush,1984; Neue, 1989) relating to water regime (Table 4-12), namely:

• Upland : Fields are never flooded for a significant period of time.

• Lowland : Fields are flooded for a significant period of time.

• Irrigated : Water regime is fully controlled.

• Continuously flooded: Fields have standing water throughout the rice growing season and may only dry for harvest.

• Intermittently flooded : Fields have at least one aeration period of more than 3 days during the cropping season.

• Single aeration: Fields have a single aeration during the cropping season at any growth stage.

• Multiple aeration: Fields have more than one aeration period during the cropping season.

• Rainfed : Water regime depends solely on precipitation.

• Flood prone: The water level may rise up to 50 cm during the cropping season.

• Drought prone : Drought periods occur during every cropping

season.

• Deep water rice : Floodwater rises to more than 50 cm for a significant period of time during the cropping season.

• Fields inundated with water depth from 50-100 cm.

• Fields inundated with water depth > 100 cm. The discussion refers to a single inventory (or base) year, (e.g., 1990) but an average over three years around the base year (e.g., 1989-1991) is recommended for the activity data, if possible.

## A GRICULTURE

4.62 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual For the inventory year, a number of input data are required.

• Area of rice cultivation by water management regime in square metres (m 2 ). As discussed above, that area is multiplied by the number of crops per year. This includes areas counted for each crop.

• Seasonally integrated flux (EF) emission values for areas of different rice ecosystems (water regimes) without organic amendments.

• of enhancement factors for organic amendments.
The result is methane emissions for each category. The total emissions for the country is the sum of the individual results for each category.

Default dataIn many cases, especially at the beginning of the process, there will be important ricegrowing areas for which specific fluxes will not be available. In such cases the regional and country-specific default data provided in Tables 4-12 and 4-13 can be used to carry out first order estimates. These data may also be used by national experts for comparison. Several ongoing activities to improve comparable measurement data have been identified. See Appendix for further information.

Area Statistics Table 4-11 contains information on harvested area of rice according to statistics from the FAO Yearbook (UN, 1992), China Agricultural Yearbook (1990), IRRI RICE Almanac (IRRI, 1994) and World Rice Statistics (IRRI, 1993). Allocation of areas to categories, e.g., irrigated, rainfed (flood prone and lowland rainfed) and upland rice for main riceproducing countries were based on the IRRI Rice Almanac (IRRI, 1994) and for other rice-producing countries these categories were based on IRRI (1990), Huke (1982) and Grist (1986). Actual percentage of the irrigated, rainfed, and flood prone areas which are continuously flooded or have an aeration period greater than 3 days or multiple aerations, are to be obtained from the country specific data.
Seasonally Integrated flux values Tables 4-12 and 4-13 provides default EF values for various categories of water regimes and multiplication factors for organic amendments. Emissions from upland rice are assumed to be 0 and ignored in the emission calculations. For continuously flooded rice, a “model” average seasonally integrated emissions for ricegrowing countries of the world was estimated from existing data (Table 4-13) to be 20 g/m 2 . These flux values are representative of flooded rice fields where organic fertiliser is not used. For intermittently flooded rice, a simple correction is applied. Fluxes are taken to be 50 per cent of the flooded (non-organic) value of 20 g/m 2 for single aeration and 20 per cent for multiple aeration. For other water regimes new default values are given in Table 4-2. For irrigated and continuously flooded, lowland rice ecosystems, the default seasonally integrated methane emission is 20 g/m 2 (see Table 4-13) for soils ‘without organic amendments’. For conversion to methane emissions from soils ‘with organic amendments’, a default correction factor of 2 (Range 2-5) is applied to the corresponding rice ecosystems for the ‘without organic amendment’ category. This is because organic amendments of flooded rice paddies increase methane emission to the atmosphere (Yagi and Minami, 1990a; Sass et al., 1991a, 1991b; Neue et al., 1994). A comprehensive

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.63 review of methane flux measurements over the past decade from a variety of countries and with different organic amendments and inorganic fertiliser treatments, is presented by Minami (1995). The amount of methane that is emitted as a result of organic soil amendments depends greatly on the amount and condition of readily available decomposable carbon contained in the treatment. Schütz et al (1989a) observed increases from a control value of 28.6 g CH 4 m 2 /yr to 68.4 g CH 4 m 2 /yr with added rice straw, (a factor of 2.4). Cicerone et al. (1992) observed increases from a control value of 1.4 g CH 4 m 2 /yr to up to 58.2 g CH 4 m 2 /yr with added straw, a factor of over 40 times higher. In field studies in the Philippines, Denier van der Gon and Neue (1995) found that fields treated with green manure applied at a rate of 22 tonnes/ha emitted over twice as much methane as fields in which the application rate was 11 tonnes/ha. Methane emission rates are highly sensitive to water management. Periodic drainage of irrigated rice paddies results in a significant decrease in methane emissions. Yagi and Minami (1990a) reported a decrease in methane emission rates as a result of a mid-season drainage in Japanese rice fields. Sass et al. (1992) found that a single midseason drain reduced seasonal emission rates by 50 per cent (from 9.27 g/m 2 to 4.86 g/m 2 ). In addition, multiple short periods of drainage (2-3 days) approximately every three weeks during the growing season reduced methane emissions to an insignificant amount (1.15 g/m 2 ) without decreasing rice grain yield. Yagi et al. (1996) compared a continuously flooded plot with constant irrigation with an intermittently drained plot with short-term draining periods several times during the rice growing season. Total seasonal methane emission rates during the cultivation period were 14.8 g/m 2 and 8.6 g/m 2 for 1991 and 9.5 g/m 2 and 5.2 g/m 2 for 1993 in the continuously flooded and intermittently drained plots, respectively. Scaling factors in Table 4-12 have been developed using the data from the literature.
Default values in Tables 4-12 and 4-13 can be used for initial calculation where local measurements are not adequate. However, national experts are encouraged to use locally available data if available. If this is done it is important to ensure that these coefficients are based on a sufficient number of measurements to capture the variability and produce a representative seasonal average value, which is needed for inventory calculations (see Appendix).

Possible Refinements National experts are encouraged to go beyond the basic method, and add as much detail as can be scientifically justified, based on laboratory and field experiments on various amendments and theoretical calculations, to arrive at the estimate of emissions from rice cultivation in their country. These details should be incorporated into subcategories (indices j,k in Equation 2) under each of the main water management categories in Equation 2 so that they can be compared at that level with data from other countries. For example: Where emission data are available for different fertiliser types, this may be incorporated into the calculations. Each category, (e.g., continuously flooded) would be further divided as follows:

F (continuously flooded) = F ( flooded chemical) + F (flooded/organic amendment)

This procedure would then be repeated for as many separate subcategories as have been defined. Each amendment may be incorporated in the same manner.

## A GRICULTURE

4.64 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual In all cases, the emission inventory must be fully documented. The documentation has two aspects. First, method of calculation must be specified as in Equation 2. Matrices of amendments must be delineated. Second, all data and original sources must be referenced, if not included explicitly as part of the inventory report. It is desirable in all cases to rely on published information, whether from the county’s government/scientific institutions an international organisation such as the UN-FAO, or the scientific literature.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.65 T ABLE 4-11
D EFAULT A CTIVITY D ATA - H ARVESTED R ICE Country or Region 1990 Area (1000s ha) Irrigated a (%) Upland Rice (%) Rainfed b (%)
Americas
USA 1114 100 0 0
Belize 2 10 90 0
Costa Rica 53 10 90 0
Cuba 150 100 0 0 Dominican Rep 93 98 2 0
El Salvador 15 10 90 0
Guatemala 15 10 90 0
Haiti 52 40 60 0
Honduras 19 10 90 0 Jamaica 0 40 60 0
Mexico 123 41 59 0 Nicaragua 48 10 90 0
Panama 92 5 95 0
Puerto Rico 0 75 25 0 Trinidad & Tobago 5 45 55 0 Argentina 103 100 0 0
Bolivia 110 25 75 0
Brazil 3945 19 75 6 (0 + 6)
Chile 35 79 21 0
Columbia 435 67 23 10 (0 + 10)
Ecuador 266 40 10 50 Guyana 68 95 5 0 Paraguay 34 50 50 0
Peru 185 84 16 0
Surinam 58 100 0 0 Uruguay 108 100 0 0
Venezuela 119 90 10 0

## A GRICULTURE

4.66 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-11 ( CONT .) D EFAULT A CTIVITY D ATA - H ARVESTED R ICE Country or Region 1990 Area (1000s ha) Irrigated a (%) Upland Rice (%) Rainfed b (%)
Asia
Brunei 1 79 21 0 Hong Kong 0 100 0 0 Syria 0 100 0 0 Turkey 52 100 0 0 India 42321 53 (16 + 37) 15 32 (16 + 16)
Pakistan 2113 100 0 0 Bangladesh 10435 22 8 70 (23 + 47) Myanmar 4760 18 6 76 (24 + 52) Nepal 1445 23 3 74 (8 + 66) Afghanistan 173 100 0 0 Bhutan 25 50 4 46 (42 + 4)
China 3 33265 93 2 5 (0 + 5) Indonesia 10502 72 (22 + 50) 11 17 (10 + 7)
Iran 570 100 0 0 Iraq 78 100 0 0 Japan 2074 99 (2 + 97) 1 0 Malaysia 639 66 12 22 (1 + 21) Philippines 3319 61 2 37 (2 + 35) Sri Lanka 828 37 7 56 (3 + 53)
Taiwan 700 97 3 0 Thailand 9650 7 1 92 (7 + 85) Kampuchea 1800 8 2 90 (42 + 48) Laos 638 2 37 61 (0 + 61) Vietnam 6028 53 8 39 (11 + 28) Democratic Republic of Korea 670 67 13 20

Republic of Korea 1242 100 (9 + 91) 0 0

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.67 T ABLE 4-11 ( CONT .) D EFAULT A CTIVITY D ATA - H ARVESTED R ICE Country or Region 1990 Area (1000s ha) Irrigated a (%) Upland Rice (%) Rainfed b (%) Europe
Albania 2 100 0 0 Bulgaria 11 100 0 0
France 20 100 0 0
Greece 15 100 0 0 Hungary 11 100 0 0 Italy 208 100 0 0 Portugal 33 100 0 0
Romania 37 100 0 0 Spain 81 100 0 0
Former USSR 624 100 0 0 Former Yugoslavia 8 100 0 0
Pacific
Australia 102 100 0 0 Fiji 13 50 50 0
Africa Algeria 1 100 0 0 Angola 18 100 0 0
Benin 7 10 90 0
Burkina Faso 19 89 11 0
Burundi 12 25 75 0
Cameroon 15 25 75 0 C African Rep 10 25 75 0
Chad 39 25 75 0
Comoros 13 100 0 0 Congo 4 25 75 0 Egypt 436 100 0 0
Gabon 0 25 75 0
Gambia 14 90 10 0
Ghana 85 24 76 0
Guinea Bissau 57 25 75 0
Guinea 608 8 47 45

## A GRICULTURE

4.68 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-11 ( CONT .) D EFAULT A CTIVITY D ATA - H ARVESTED R ICE Country or Region 1990 Area (1000s ha) Irrigated a (%) Upland Rice (%) Rainfed b (%) Ivory Coast 583 6 87 7 Kenya 15 25 75 0
Liberia 168 0 94 6 Madagascar 1160 10 14 76 (2 + 74)
Malawi 29 25 75 0
Mali 222 25 75 0
Mauritania 14 100 0 0
Morocco 6 100 0 0 Mozambique 109 25 75 0 Niger 29 35 65 0 Nigeria 1567 16 51 33 (33 + 0)
Rwanda 3 25 75 0 Senegal 73 25 75 0
Sierra Leone 339 1 67 32
Somalia 5 50 50 0
South Africa 1 100 0 0
Sudan 1 50 50 0
Swaziland 0 25 75 0 Tanzania 375 3 22 75 (0 + 75) Togo 21 4 96 0 Uganda 37 25 75 0
Zaire 393 5 90 5
Zambia 11 25 75 0
Zimbabwe 0 25 75 0

a Numbers in brackets indicate continuously flooded and intermittently flooded respectively.
b Numbers in brackets indicate continuously flood-prone and drought-prone respectively

.

c Values are currently being updated. Sources: DeDatta (1975), Huke, (1982), Grist (1986), IRRI (1990), NGGIC (1996). Notes : Areas were taken from FAO Yearbook (UN, 1992), China Agricultural Yearbook (1990), World Rice Statistics (IRRI, 1990) and IRRI Rice Almanac 1993-1995 (IRRI, 1993).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.69 T ABLE 4-12 S CALING F ACTORS F OR M ETHANE E MISSIONS F OR R ICE E COSYSTEMS R ELATIVE T O C ONTINUOUSLY F LOODED F IELDS (W ITHOUT O RGANIC A MENDMENTS ) Category Sub-Category a Scaling Factors (relative to emission factors for continuously flooded fields) Upland None 0 Lowland Irrigated Continuously flooded 1.0 Intermittently

flooded b Single aeration 0.5 (0.2-0.7)

Multiple aeration 0.2 (0.1-0.3)

Rainfed Flood prone 0.8 (0.5-1.0) Drought prone 0.4 (0-0.5) Deep water Water depth 50-100 cm 0.8 (0.6-1.0) Water depth > 100 cm 0.6 (0.5-0.8)

a Other rice ecosystem categories, like swamps and inland, saline or tidal wetlands may be discriminated within each sub-category according to local emisson measurements. b Defined as > 3 days aeration during the vegetative period. Note: For irrigated and continuously flooded, lowland rice ecosystems, the default seasonally integrated methane emission is 20 g/m 2 (see Table 4-13) for soils ‘without organic amendments’. For conversion to methane emissions from soils ‘with organic amendments’, apply a default correction factor of 2 (Range 2-5) to the corresponding rice ecosystem for the ‘without organic amendment’ category.

## A GRICULTURE

4.70 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-13 S EASONALLY I NTEGRATED M ETHANE E MISSION F ACTORS FOR C ONTINUOUSLY F LOODED R ICE WITHOUT O RGANIC F ERTILISER IN V ARIOUS L OCATIONS OF THE W ORLD Country Seasonally Integrated Emission Factor, EF a

(g/m 2 ) Literature/Remarks

Australia 22.5 NGGIC, 1996 China 13 (10-22) Wassman et al., 1993a India 10 (5 - 15) Mitra, 1996 Parashar et al., 1996 Indonesia 18 (5 - 44) Nugroho et al., 1994a,b Italy 36 (17-54) Schütz et al., 1989a Japan 15 Minami, 1995 Republic of Korea 15 Shin et al., 1995 Philippines (25 - 30) Neue et al., 1994; Wassman et al., 1994 Thailand 16 (4 - 40) Towpryaoon et al., 1993 USA (Texas) 25 (15 - 35) Sass and Fisher, 1995
Arithmetic Mean b 20 (12-28)
-

a It is recognised that the emission factors presented in Table 4-13 will need to be periodically updated as better data become available. However, this dataset represents the best available information at the time of compilation. b The arithmetic mean of the seasonally integrated emission factor, EF, is derived from the values shown in Table 4-13. The range of emission factors is defined as the standard deviation about the mean.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.71 

## Appendix Intercomparability of Methane Emission Data from Rice Cultivation

Chamber measurements Each laboratory should provide a standardised emission program of control flux measurements to ensure the intercomparibilty and intercalibration of extended data sets. An emission standardisation programme will consist of a specified experimental plan for seasonal and annual flux measurements along with specific accompanying data on location and climate, soil, water management, plant characteristics, fertiliser treatment and a detailed cropping calendar.

• Methane flux measurements should be recorded at least twice per week over an entire season. Experiments should be continued during fallow and/or alternate cropping times as well as during the entire normal local rice growing season including land preparation. In areas where double or triple cropping is practised, data should be collected for all growing seasons.

• Since emissions are strongly influenced by daily temperature changes, the diel pattern of emission (6-12 flux rates within a 24 hour period) should be determined at least three times during the season.

• A data log of all agricultural events should be kept., e.g., transplant date, panicle initiation, heading, anthesis, harvest, etc. as well as fertilisation, water management schedule, weeding schedule, herbicide and pesticide treatments.

• At the time of each flux measurement, one should also collect the air temperature, flood water temperature, and the soil temperature.

• Fertilisation treatment in the standardisation (continuous irrigation) plots should be according to local practices, but limited to inorganic fertiliser. The application rate as kg N ha -1 and number and timing of applications should be reported.

• Fertilisation treatment in other experimental areas, including organic fertilisers, should reflect local practices. Amounts, type, and timing of applications should be reported for each phase of the cropping sequence at all scales.

• Standardisation chamber plots are to be kept flooded from shortly before transplanting until maturity. During flood, the water should be kept at a 5 cm minimum constant depth. A daily log should be kept of the amount of water added and when. Other water management regimes should be investigated when they are practised locally. A daily log should be kept of times and durations of draining, the amounts of water added and other applicable data. For further information, see ‘Global Measurements Standards of methane emissions for irrigated rice cultivation’ , IGAC (1994).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.73 

## 4.4 Greenhouse Gas Emissions from Agricultural Burning

4.4.1 Introduction Where there is open burning associated with agricultural practices, a number of greenhouse gases (GHGs) are emitted from combustion. All burning of biomass produces substantial CO 2 emissions. However, in agricultural burning, the CO 2 released is not considered to be net emission. The biomass burned is generally replaced by regrowth over the subsequent year. An equivalent amount of carbon is removed from the atmosphere during this regrowth, to offset the total carbon released from combustion. Therefore the long term net emissions of CO 2 are considered to be zero. Agricultural burning releases other gases in addition to CO 2 which are by-products of incomplete combustion: methane, carbon monoxide, nitrous oxide, and oxides of nitrogen, among others. These non-CO 2 trace gas emissions from biomass burning are net transfers from the biosphere to the atmosphere. It is important to estimate these emissions in national inventories. 16 There are two major types of agricultural burning addressed in this section – savanna burning and field burning of crop residues. The approach is essentially the same as that used for non-CO 2 trace gases for all burning of unprocessed biomass, including traditional biomass fuels and open burning of cleared forests. For all these activities, there is a common approach in the proposed methodology, in that crude estimates of non-CO 2 trace gas emissions can be based on ratios to the total carbon released. The carbon trace gas releases (CH 4 and CO) are treated as direct ratios to total carbon released. Non-methane volatile organic compounds (NMVOCs) can be treated in a similar way. However, no default values for NMVOC are provided in this version of the Guidelines

. To handle nitrogen trace gases, nitrogen to carbon ratios are used to derive total nitrogen released and then emissions of N 2 O and NO x are estimated based on ratios of these gases to total nitrogen released. Tables 4-15 and 4-16 provide suggested default values for non-CO 2 trace gas emission ratios. These are presented with ranges, which

16 For biomass combustion, CO 2 emissions are frequently not considered net emissions, and this is the case for agricultural burning. One could argue, in such cases, that this burning could be considered a short term sink of CO 2 . That is, a portion of carbon in biomass is being released as net emissions of CH 4 and CO, while regrowth is removing the full amount of the original carbon from the atmosphere in the next cycle. Each year plants take up a certain amount of carbon from the atmosphere. When they are burned some of that carbon is converted to CO, and CH 4 , so that an amount less than the total CO 2 which was taken up by the plants is re-emitted as CO 2 . See Howden et al. (1996), for a more detailed discussion of this proposal. Treating emissions of CO and CH 4 to the atmosphere, as a sink for atmospheric CO 2 , however, is inconsistent with the proposed IPCC emissions methodology. In particular, the other carbon compounds emitted are converted back into CO 2 in the atmosphere over periods of days up to a decade or so. Thus, over the time horizons of interest for CO 2 , (i.e. more than 100 years) there is no sink of CO 2 .

## A GRICULTURE

4.74 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual emphasise their uncertainty. However, the basic calculation methodology requires that users select a best estimate value. 17 The calculation of immediate trace gas emissions, based on the default emission ratios provided in Tables 4-15 and 4-16, produces relatively crude estimates with substantial uncertainties. 18 Use of specific emission ratios which vary by type of burning, region, etc. may allow for more precise calculations. The calculations described here ignore the contemporary fluxes associated with past burning activities. These delayed releases are known to exist, but are poorly understood at present. This and other possible refinements are discussed at the end of this section.



### 4.4.2 P r e s c r i b e d B u r n i n g o f S a v a n n a s
Background The term savanna refers to tropical and subtropical vegetation formations with a predominantly continuous grass cover, occasionally interrupted by trees and shrubs (Bouliere and Hadley 1970). These formations exist in Africa, Latin America, Asia, and Australia. The growth of vegetation in savannas is controlled by alternating wet and dry seasons: most of the growth occurs during the wet season; man-made and/or natural fires are frequent and generally occur during the dry season. The global area of savannas is uncertain, in part due to lack of data and in part due to differing ecosystem classifications.Estimates of the areal extent of savannas range from 1300-1900 million hectares worldwide, about 60 per cent of which are humid savannas (annual rainfall of 700 mm or more) and 40 per cent are arid savannas (annual rainfall of less than 700 mm) (Bolin et al., 1979;Whittaker and Likens, 1975; Lanly, 1982; Lacey et al., 1982; and Hao et al., 1990). Largescale burning takes place primarily in the humid savannas because the arid savannas lack sufficient grass cover to sustain fire. Humid savannas are burned every one to four years on average with the highest frequency in the humid savannas of Africa (as cited in Hao et al., 1990).

17 Emissions inventory developers are encouraged to provide estimates of uncertainty along with these best estimate values where possible or to provide some expression of the level of confidence associated with various point estimates provided in the inventory. Procedures for reporting this uncertainty or confidence information are discussed in Volume 1: Reporting Instructions

. 18 Emission ratios used in this section and presented in the tables are derived from Crutzen and Andreae (1990), Delmas (1993), Delmas and Ahuja (1993) and Lacaux, et al. (1993). They are based on measurements in a wide variety of fires, including forest and savanna fires in the tropics and laboratory fires using grasses and agricultural wastes as fuel. In many cases these ratios are general averages for all biomass burning. Research will need to be conducted in the future to determine if more specific emission ratios, e.g., specific to the type of biomass and burning conditions, can be obtained. Also, emission ratios vary significantly between the flaming and smouldering phases of a fire. CO 2 , N 2 O, and NO x are mainly emitted in the flaming stage, while CH 4 and CO are mainly emitted during the smouldering stage (Lobert et al., 1990). The relative importance of these two stages will vary between fires in different ecosystems and under different climatic conditions, and so the emission ratios will vary. As inventory methodologies are refined, emission ratios should be chosen to represent as closely as possible the ecosystem type being burned, as well as the characteristics of the fire.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.75 Savannas are intentionally burned during the dry season primarily for agricultural purposes such as ridding the grassland of weeds and pests, promoting nutrient cycling, and encouraging the growth of new grasses for animal grazing. Savanna burning may be distinguished from other biomass burning activities like open forest clearing because there is little net change in the ecosystem biomass in the savanna after the vegetation regrows during the wet season. Consequently, while savanna burning results in instantaneous gross emissions of CO 2 , it is reasonable to assume that the net carbon dioxide released to the atmosphere is essentially zero because the vegetation typically regrows between burning cycles. 19 Savanna burning does release several other important trace gases: methane (CH 4 ), carbon monoxide (CO), nitrous oxide (N 2 O), oxides of nitrogen (NO x , i.e., NO and NO 2 ) and non-methane volatile organic compounds (NMVOCs). Estimates of global emissions of these gases due to savanna burning have been based on estimates of the annual instantaneous gross release of carbon from this activity and on ratios of the other trace gases released from burning to the total carbon released by burning. Estimates of the annual instantaneous gross release of carbon from savanna burning are highly uncertain because of lack of data on:

• the aboveground biomass density of different savannas;

• the savanna area burned annually;

• the fraction of aboveground biomass which actually burns; and

• the fraction which oxidises. The methodology that is proposed in the next section, although conceptually quite simple, takes these factors into account. The approach allows for estimation of non-CO 2 trace gases released by savanna burning, based on default data sets and on assumptions from average literature values for various regions and types of savannas. It also allows for more accurate national estimates if data and assumptions can be developed to reflect national average conditions accurately. Nonetheless, a wide variety of technical details and open scientific issues remain important research topics.

Calculations There are two basic components to the calculation. First, it is necessary to estimate the total amount of carbon released to the atmosphere from savanna burning. These are not considered to be net emissions, but are needed to derive non-CO 2 trace gas emissions, which are net emissions. What is required is the annual area burned for the various types of savannas, where type is based primarily upon above and below ground biomass, and perhaps climatological conditions and nutrient status. It is generally recommended for all emissions from agriculture that three-year averages of activity data (e.g., hectares burned) be used instead of a single year’s data where possible. This is especially important for savanna burning which is highly variable from year to year. This variability should also be taken into account by national experts in planning data collection programmes to provide more accurate inputs to national inventory calculations. If data are not directly available, estimates can be derived based on total savanna area 20 and

19 If grazing pressure coupled with burning too often reduces biomass (i.e., degrades the quality of savannas), then this needs to be considered as a carbon dioxide source. This is not assumed in the basic calculations but could be included as a refinement if considered important.

20 Most countries with significant savanna area should have national statistics on the total area, but FAO publications (e.g. FAO, 1993) also provide country-specific estimates.

## A GRICULTURE

4.76 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual average percentages of savanna burned annually, as shown in Table 4-14. Based on the area and type of savanna burned, the amount of carbon released can be calculated (a reflection of biomass densities, fractions burned, carbon contents and fractions oxidised). The second component of the calculation is the same as for other biomass burning categories – emission ratios are applied to estimate the amount of trace gas released based on the amount of carbon released (Table 4-15 provides default emission ratios).

T ABLE 4-14 R EGIONAL S AVANNA S TATISTICS

Region a Fraction of Total Savanna that is Burned Annually Aboveground Biomass Density (t dm/ha) Fraction of Biomass Actually Burned Fraction of Aboveground Biomass that is Living Tropical America 0.50 6.6 ±1.8 Tropical Asia 0.50 4.9 Tropical Africa
Sahel zone
North Sudan zone
South Sudan zone
Guinea zone 0.75
0.05-0.15 b
0.25-0.50 b
0.25-0.50 b
0.60-0.80 b 6.6 ±1.6
0.5-2.5 b

2-4 b
3-6 b
4-8 b 0.95
0.85
0.85
0.9-1.0 0.20
0.45
0.45
0.55
Australia 0.05-0.70 2.1-6
Sources: Hao et al., 1990, except where noted. These figures are growing season average biomass values, considered most appropriate for general default values

a Note that these are ecological zones that do not correspond directly to areas with political boundaries of the same name. For example, the North and South Sudan zones include countries other than Sudan and run East-West across the African continent. b Menaut et al. (1991) These figures are maximum biomass values. For these arid sub-regions, maximums are considered the most appropriate default values. Note: Biomass density is in tonnes of dry matter (dm) per hectare (ha).

The approach recognises that countries generally possess more than one savanna type, each with different characteristics, such as vegetative cover, that would affect trace gas emissions from burning. Also, the savanna area within a country may not be burned all at once, but rather in stages over the course of the dry season. Since the amount and nature (e.g., moisture content) of the vegetation changes during the year, factors such as biomass exposed to burning and fraction burned will vary among the savanna areasburned at different times. The data requested by this methodology focus upon countryspecific types of savannas and the country-specific rate of burning for each type. 21

21 If the area of savanna is not readily available, then the area of "open, broad-leaved forests," including open, broad-leaved, fallow areas, as defined by the UN Food and Agriculture Organization in FAO (1993) can be used as an estimate. This land area, corresponds to "mixed broad-leaved forest-grassland tree formations with a continuous dense grass layer in which the [woody vegetation covers] more than 10% [of the area]" (Lanly, 1982). FAO (1993) provides 1990 estimates of this area, by country, for tropical America, Asia, and Africa. Hao et al. (1990) provide an estimate of the humid savanna area in Australia, based on work by Lacey et al. (1982).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.77 It is also recognised that national and regional estimates of the percentage of savanna area burned annually are highly uncertain. An example selection of regional estimates is included in Table 4-14. Though regional variability is great, the methodology, by focusing upon a simple classification of savanna type and the burning by type, can be implemented using data that are available to most countries. The methodology is intended to be flexible to allow users to define the savanna types and/or geographic subregions for calculations. It is strongly recommended that national experts consider dividing total savannas into woody savannas and grasslands, if possible. Many countries contain some systems which have significant aboveground woody biomass and others which have very little aboveground biomass other than grasses. These subcategories have significantly different biomass densities and fractions oxidised and should be accounted for separately rather than by averaging, if data are available. National experts are encouraged to carry out the calculations at the finest levels of detail for which credible data can be obtained. Finally, by varying assumptions about the rate and/or type of savannas burned, national experts can easily compare the sensitivity of the calculated emissions to the uncertainties in the data. It should be noted that not all savanna burning occurs from anthropogenic causes. Some natural savanna fires obviously occur, and would occur in the absence of human intervention. As is the case with many human interactions with the biosphere, it is very difficult to establish the net effects of human intervention relative to the natural background, or the conditions which would have occurred naturally in the absence of intervention. In this situation, the recommended conservative default is that all fires are considered anthropogenic, unless they can be documented to be from natural causes. This clearly may overstate the emissions somewhat. National experts may choose to modify this assumption using expert judgement or other sources to allocate the anthropogenic and natural components, provided the rationale is clearly documented.
Step 1: Total Carbon Released From Savanna Burning In order to calculate the carbon released to the atmosphere from savanna burning, these data are required for each category:

• Area of savanna;

• Fraction of savanna area burned annually;

• Average aboveground biomass density (tonnes dry matter/hectare) of savannas;

• Fraction of aboveground biomass which actually burns;

• Fraction of aboveground biomass that is living;

• Fraction of living and of dead aboveground biomass oxidised; and

• Fraction of carbon in living and dead biomass. Not all of these data must be provided by the user. Initially one could pool the living and dead biomass if data are not available. More importantly, Table 4-14 provides much of the basic default data that only need to be refined for country-specific relevance. Given the data, the steps to calculate emissions are not overly difficult. One simply calculates from the area burned the total carbon released based upon the factors listed above. In

## A GRICULTURE

4.78 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual addition to the data in Table 4-14, other recommended default values are included in the step-by-step discussion below. 22 The following equations summarise the calculations to estimate the total carbon released due to the burning of savannas for each category:

E QUATION 1 Area of Savanna Burned Annually (ha)

= Total Area of Savanna (ha) x Fraction Burned Annually

E QUATION 2 Biomass Burned (t dm)

= Area of Savanna Burned Annually (ha) x Aboveground Biomass Density (t dm/ha) x Fraction Actually Burned

E QUATION 3 Carbon Released from Live Biomass (t C)

= Biomass Burned (t dm) x Fraction that is Live x Fraction Oxidised x Carbon Content of Live Biomass (t C/t dm)

E QUATION 4 Carbon Released from Dead Biomass (t C)

= Biomass Burned (t dm) x Fraction that is Dead x Fraction Oxidised x Carbon Content of Dead Biomass (t C/t dm)

22 It is hoped that individual countries have this information since it is needed to execute the proposed methodology. Regional estimates of these statistics are provided by Menaut (1990) and Hao et al. (1990) and reproduced in a table. More country-specific research is clearly needed on this issue before accurate inventories can be developed. This research should include data on savanna area burned annually, savanna biomass densities, live fractions of biomass, burning efficiencies, and carbon contents of savanna biomass. In the meantime, default values can be used.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.79 E QUATION 5 Total Carbon Released (t C)

= C Released from Live Material (t C) + C Released from Dead Material (t C)

In the first equation, the savanna area in the country is multiplied by the percentage of the savanna area that is burned annually, if statistics on area burned annually are not directly available. If national experts have data on the area burned annually they should use this and begin with equation 2. In the second, area burned is multiplied by aboveground dry biomass per hectare (ha) on the savanna at the time of burning and the fraction of biomass which actually burns. Regional estimates of rates of savanna burning and biomass densities are presented in Table 4-14. The fraction actually burned accounts for the fact that when savannas are burned, not all of the biomass on each hectare is actually exposed to flame. If detailed information is not available, a general default value in the range of 0.80-0.85 is recommended (Delmas and Ahuja, 1993). The aboveground biomass density before burning is a function of the type of savanna being burned and the time of year in which burning occurs. 23 The values for West African savannas provided in Table 4-14 correspond to mid-season fires, except for those of the Sahel where burning occurs early. If statistics on maximum biomass density and fraction of maximum biomass density present at the time of burning are not available, countries can use an average biomass density instead. According to this analysis, average savanna biomass densities are lowest in tropical Asia, at about 5 tonnes per hectare (t/ha) (Singh and Misra, 1978), average around 6.6 t/ha in tropical Africa and tropical America (San José and Medina, 1976; González-Jiménez, 1979; Coutinho, 1982; Hopkins, 1965; Haggar, 1970; Menaut and César, 1982; and Huntley and Morris, 1982). The densities range between 2 and 6 t/ha in Australia (Lacey et al., 1982). These estimates have an uncertainty of ± 30 per cent based on field measurements (Hao et al., 1990). As mentioned, these regional average densities are presented in Table 4-14 and can be used as default values if average biomass density for a specific country or savanna type is not known. In the third and fourth equations, the living and the dead portions of aboveground biomass burned are multiplied by their respective fractions oxidised and carbon contents. Estimates of the fraction of aboveground biomass that is living for West African savannas range from 20 to 55 per cent (Table 4-14). Data suggest that for the live portion, the fraction which burns ranges between 65 and 95 per cent and for the dead portion essentially 100 per cent burns (Menaut et al., 1991). If fractions oxidised are not available, 80 per cent and 100 per cent for the living and dead portions, respectively, can be used. If country or ecosystem values are not available, then the values 0.45 t C/t dry biomass and 0.40 t C/t dry biomass can be used as default values for the carbon contents of the living and dead portions, respectively (Menaut et al., 1991). The total carbon released from savanna burning (Equation 5) is estimated by summing the carbon released from the living and the dead biomass fractions, calculated in Equations 3 and 4.

23 Menaut et al. (1991) calculate this number by multiplying the maximum biomass density of the savanna (which generally is reached at the end of the growing season) by a coefficient that declines as the burning occurs later in the dry season.

## A GRICULTURE

4.80 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Step 2: Emissions Once the carbon released from savanna burning has been estimated, the emissions of CH 4 , CO, N 2 O, and NO x can be calculated using emission ratios. (Default values are presented in Table 4-15.) 24 The amount of carbon released due to burning is multiplied by the emission ratios of CH 4 and CO relative to total carbon released to yield emissions of CH 4 and CO (each expressed in units of C). The emissions of CH 4 and CO are multiplied by 16/12 and 28/12, respectively, to convert to full molecular weights. NMVOC could also be calculated in the same way. However, default values are not available in this edition of the Guidelines

. To calculate emissions of N 2 O and NO x , first the carbon released is multiplied by the estimated ratio of nitrogen to carbon (N/C ratio) in savanna biomass by weight (0.006 is a general default value for savanna biomass burning (Crutzen and Andreae, 1990)). This yields the total amount of nitrogen (N) released from the biomass burned. The total N released is then multiplied by the ratios of emissions of N 2 O and NO x relative to the N released to yield emissions of N 2 O and NO x (expressed in units of N). To convert to full molecular weights, the emissions of N 2 O and NO x are multiplied by 44/28 and 46/14, respectively. 25
The non-CO 2 trace gas emissions calculations from burning are summarised as follows:
CH 4 Emissions = (carbon released) x (emission ratio) x 16/12 CO Emissions = (carbon released) x (emission ratio) x 28/12
N 2 O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28
NO x Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 46/14

T ABLE 4-15 E MISSION R ATIOS FOR S AVANNA B URNING C ALCULATIONS

Compound Ratios

CH 4 a

CO b

N 2 O c

NO x c 0.004 (0.002 - 0.006) 0.06 (0.04 - 0.08) 0.007 (0.005 - 0.009) 0.121 (0.094 - 0.148)
Sources:
a Delmas, 1993 b Lacaux, et al., 1993
c Crutzen and Andreae, 1990 Note: Ratios for carbon compounds, i.e., CH 4 and CO, are mass of carbon compound released (in units of C) relative to mass of total carbon released from burning (in units of C); those for the nitrogen compounds are expressed as the ratios of mass of nitrogen compounds released relative to the total mass of nitrogen released from the fuel.

24 This approach is adapted from Crutzen and Andreae, 1990, with some values updated, based on more recent studies by Delmas (1993), Delmas and Ahuja (1993) and Lacaux et al. (1993).

25 The molecular weight ratios given above for the emitted gases are with respect to the weight of nitrogen in the molecule. Thus for N 2 O the ratio is 44/28 and for NO X it is 46/14. NO 2 has been used as the reference molecule for NO X .

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.81 

### 4.4.3 F i e l d B u r n i n g o f A g r i c u l t u r a l R e s i d u e s
Background Large quantities of agricultural wastes are produced, from farming systems world-wide, in the form of crop residue. 26 Burning of crop residues, like the burning of savannas, is not thought to be a net source of carbon dioxide (CO 2 ) because the carbon released to the atmosphere during burning is reabsorbed during the next growing season. However, crop residue burning is a significant net source of CH 4 , CO, NO x , and N 2 O. This section accounts for emissions of these non-CO 2 gases from field burning of agricultural crop residues. Burning of agricultural crop residues as an energy source is covered in the Energy chapter, in the section on fuel Combustion. The amount of agricultural wastes produced varies by country, crop, and management system. For example, cereal crops produce between 0.6 and 2.5 tonnes of straw per tonne of grain (Barnard, 1990; Ponnamperuma, 1984), and wetland rice cultivated under a moderate level of management in the Philippines was found to produce between 0.6 and 0.9 tonnes of straw per tonne of grain (Ponnamperuma, 1984). Approximately 3.1 billion tonnes of crop residue are produced each year, with about 60 per cent originating in the developing world, and 40 per cent in the developed world (Strehler and Stützle, 1987). Burning of agricultural wastes in the fields is a common practice in the developing world. It is used primarily to clear remaining straw and stubble after harvest and to prepare the field for the next cropping cycle. In Southeast Asia, burning is the major disposal method for rice straw (Ponnamperuma, 1984), which accounts for about 31 per cent of the agricultural waste in the developing world. Sugar cane residues, which make up about 11 per cent of the world's agricultural waste, are primarily disposed of by burning (Crutzen and Andreae, 1990). It has been estimated that as much as 40 per cent of the residues produced in developing countries may be burned in fields, while the percentage is lower in developed countries (Barnard and Kristoferson, 1985). Another study suggests that approximately 425 Tg dry matter agricultural wastes (~200 Tg C) are burned in the fields in developing countries and that about one-tenth as much is burned in developed countries (Crutzen and Andreae, 1990).

Calculations The methodology for estimating greenhouse gas emissions from burning of agricultural wastes is based, as in savanna burning, on 1) total carbon released, which is a function of the amount and efficiency of biomass burned and the carbon content of the biomass, and 2) the application of emission ratios of CH 4 and CO to total carbon released, and of N 2 O and NO x to total nitrogen released from biomass fires which are available from the scientific literature on biomass burning. It is generally recommended for all emissions from agriculture and land use change, that three-year averages of activity data (e.g., crop residues burned) be used if available.
Step 1: Total Carbon Released from Burning Agricultural Residues Data required, for each crop type, to calculate the amount of carbon burned in agricultural wastes are listed below:

26 Barnard (1990) outlines several broad categories of crop residue: woody crop residues (coconut shells, jute sticks, etc.), cereal residues (rice and wheat straw, maize stalks, etc.), green crop residues (groundnut straw, soybean tops, etc.), and crop processing residues (bagasse, rice husks, etc.).

## A GRICULTURE

4.82 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Amount of crops produced with residues that are commonly burned;

• Ratio of residue to crop product;

• Fraction of residue burned;

• Dry matter content of residue;

• Fraction oxidised in burning; and

• Carbon content of the residue. There are standard default or literature values available for many of these data. Table 4-17 provides a summary of available default data. The most important data for users to provide are the actual amount of crops produced (by type) with residues that are commonly burned. Annual crop production statistics by country for most of the crops from which residues are burned are given in the FAO Production Yearbooks, FAO (1991)

. Users may also find the United Nations World Trade Yearbooks useful. Crop-specific data for each country on ratios of residue to crop, fraction of residue burned, dry matter content of residue, and carbon content of residue can be incorporated at any time to replace the default values. A potentially valuable data source is the recent BUN/UNCED study by Professor D. Hall (and others) of Kings College, London, Hall et all (1994). In this context, one should also note the book Renewable Energy: Sources for Fuels and Electricity edited by Johansson et al. (1992). From production data one can estimate the actual material (in carbon units) that is burned. One simple procedure is shown below:
Total carbon released (tonnes of carbon) =

all crop types 

# ∑ annual production (tonnes of biomass per year),

x the ratio of residue to crop product (fraction), x the average dry matter fraction of residue (tonnes of dry matter / tonnes of biomass), x the fraction actually burned in the field, x the fraction oxidised, x the carbon fraction (tonnes of carbon / tonnes of dry matter)

It is highly desirable to use country-specific data for these values wherever possible. Example estimates of residue/crop product ratios, average dry matter fraction and carbon fraction for certain crops are presented in Table 4-17. 27 If no other data are available,

27 Dry matter (dm), or dry biomass, refers to biomass in a dehydrated state. According to Elgin (1991), the moisture content of crop residue varies depending on the type of crop residue, climatic conditions (i.e., in a humid environment the residue will retain more moisture than in an arid environment), and the length of time between harvesting and burning of the residue. From a simple perspective, one can use the dry matter content values in Table 4-17 to convert from total crop residue to dry matter. For example, 200 tonnes of crop residue with a moisture content of 10%, would have a dry matter content of 90%, equal to 180 tonnes of dry matter. To convert from dry matter to carbon content, an average value of 0.45 t C/t dm can be used in the cases

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.83 the following assumptions regarding the fraction of crop residue burned in the field can be used as very crude default factors: for developing countries 0.25, and for developed countries a much smaller share possibly, 0.10 or less. 28 A default value of 0.90 for fraction oxidised can be used to account for the approximate 10 per cent of the carbon that remains on the ground as a result of charcoal formation and other aspects of incomplete combustion (Seiler and Crutzen, 1980; and Crutzen and Andreae, 1990).
Step 2: Gas Emissions Once the carbon released from field burning of agricultural residues has been estimated, the emissions of CH 4 , CO, N 2 O, and NO x can be calculated based on emission ratios (default values are provided in Table 4-16). 29 The amount of carbon released due to burning is multiplied by the emission ratios of CH 4 and CO relative to total carbon to yield emissions of CH 4 and CO (each expressed in units of C). The emissions of CH 4 and CO are multiplied by 16/12 and 28/12, respectively, to convert to full molecular weights. NMVOC could also be calculated in the same way. However, default values are not available in this edition of the Guidelines

. To calculate emissions of N 2 O and NO x , first the total carbon released is multiplied by the estimated N-C ratio of the fuel by weight to yield the total amount of nitrogen (N) released. Some crop-specific values are given in Table 4-17 and 0.015 is a general default value for crop residues. 30 The total N released is then multiplied by the ratios of emissions of N 2 O and NO x relative to the N content of the fuel to yield emissions of N 2 O and NO x (expressed in units of N). To convert to full molecular weights, the emissions of N 2 O and NO x are multiplied by 44/28 and 46/14, respectively. 31 The calculation for trace gas emissions from burning is summarised as follows:
CH 4 Emissions = Carbon Released x (emission ratio) x 16/12 CO Emissions = Carbon Released x (emission ratio) x 28/12
N 2 O Emissions = Carbon Released x (N/C ratio) x (emission ratio) x 44/28
NO x Emissions = Carbon Released x (N/C ratio) x (emission ratio) x 46/14

where crop specific data are not available. The terms dry matter and dry biomass are used interchangeably in this text.

28 Crutzen and Andreae, 1990. The estimates are very speculative and should be used with caution. The actual percentage burned varies substantially by country and crop type. This is an area where locally developed, country-specific data are highly desirable. As this issue is studied further, it may be possible to incorporate more accurate, country-and crop-specific percentages into future editions of the Guidelines

. 29 This approach is adapted from Crutzen and Andreae, 1990, with some values updated based on more recent studies by Delmas (1993), Delmas and Ahuja (1993) and Lacaux et al. (1993).

30 Crop specific values are generally in the range of 0.01-0.02, from Crutzen and Andreae, 1990, so that 0.015 can be used as a generally representative value if no other information is available.

31 The molecular weight ratios given above for the emitted gases are with respect to the weight of nitrogen in the molecule. Thus for N 2 O the ratio is 44/28 and for NO X it is 46/14. NO 2 has been used as the reference molecule for NO X .

## A GRICULTURE

4.84 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 4-16 E MISSION R ATIOS FOR A GRICULTURAL R ESIDUE B URNING C ALCULATIONS Compound Ratios

CH 4 a
CO b

N 2 O c
NO x c 0.005 Range 0.003 - 0.007 0.06 Range 0.04 - 0.08 0.007 Range 0.005 - 0.009 0.121 Range 0.094 - 0.148
Sources:

a Delmas, 1993 b Lacaux, et al., 1993

c Crutzen and Andreae, 1990 Note: Ratios for carbon compounds, i.e., CH 4 and CO, are mass of carbon compound released (in units of C) relative to mass of total carbon released from burning (in units of C); those for the nitrogen compounds are expressed as the ratios of mass of nitrogen compounds relative to the total mass of nitrogen released from the fuel.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.85 T ABLE 4-17 S ELECTED C ROP R ESIDUE S TATISTICS Product Residue/Crop Product Dry Matter Fraction Carbon Fraction (% dm) Nitrogen-Carbon (N-C) Ratio
Wheat 1.3 0.78-0.88 0.4853 0.012 Barley 1.2 0.78-0.88 0.4567
Maize 1 0.30-0.50 0.4709 0.02
Oats 1.3 Rye 1.6
Rice 1.4 0.78-0.88 0.4144 0.014
Millet 1.4 0.016 Sorghum 1.4 0.02

Pea 1.5
Bean 2.1 Soya 2.1 0.05
Potatoes 0.4 0.30-0.60 0.4226
Feedbeet 0.3 0.10-0.20 a 0.4072 a Sugarbeet 0.2 0.10-0.20 a 0.4072 a Jerusalem artichoke 0.8

Peanut 1
Sources: Strehler and Stützle, 1987 Sugarbeet data from Ryan and Openshaw, 1991 Nitrogen content from Barnard and Kristoferson, 1985

a These figures are for beet leaves.

Possible refinements of the basic calculations The basic calculations presented above address the immediate release of non-CO 2 trace gases when savannas or crops are burned. This is believed to be the most important effect of biomass burning on GHG emissions and the best characterised at present. However, there are other issues not treated in these calculations. The effect of past burning on current emissions is one such issue. The longer-term release or uptake of these gases following burning is an important research issue and may be included in future refinements of the calculations. In particular, grassland fires (savanna burning) may perturb the soils sufficiently to release additional N 2 O and NO x . Little is known about the magnitude of this flux so these emissions are not included in the first application of the methodology. It is less likely that such delayed releases are significant after field burning of agricultural residues, but this may also require further study. Long term changes in soil carbon are certainly possible as a result of agricultural practices. In the land use change and forestry chapter, there is a general default assumption that soil carbon is gradually lost from agricultural lands over many years after forests are cleared. In fact, depending on the specific agricultural and soil management practices (including burning) which are used, there may be a variety of effects on soil

## A GRICULTURE

4.86 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual carbon. For example, repeated burning of savannas and crop residues in fields may cause an increase in the amount of carbon stored in the soil over time. This is an area which requires further research and may lead to more detailed emissions estimation methods in the future. In addition, agricultural practices such as overgrazing, which degrade the productivity of grasslands or other agricultural lands, reduce the amount of aboveground biomass which regrows. These could be considered sources of gradual emissions of carbon dioxide. This situation is not included in the basic calculations, but could be included in more refined calculations. National experts should determine whether or not this is important for their country, and whether or not they are able to provide input data. A similar long-term effect can be observed from savanna burning. If the savannas are burned too frequently, complete regrowth may not occur. In this situation, grasslands can degrade over time, resulting in long-term losses of both aboveground and soil carbon. If this condition is significant, national experts are encouraged to estimate the annual effect and explain the assumptions and data used. Another possible refinement is to account for carbon that might be sequestered through the use of agricultural residues to make durable products (e.g., bricks, composite boards). The default assumption is that the carbon sequestered in such activities on an annual basis is small, and can be ignored in the calculations, that is, as long as the stocks of such products are not significantly increasing or decreasing over time, their effect on emissions/removals can be ignored. If national experts believe the effects may be significant, they are encouraged to estimate this carbon sink and document the assumptions and data used.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.87 

## 4.5 Greenhouse Gas Emissions from Agricultural Soils

4.5.1 Introduction Agricultural soils may emit or remove nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and/or methane (CH 4 ). This section presents the method for calculating national emissions of N 2 O from agriculture soils. This N 2 O method is a significant revision of the 1995 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 1995). Carbon dioxide emissions from soils are described in the Chapter on Land-use Change and Forestry.

For N 2 O, the 1995 Methodology was evaluated and the present method includes more sources of N 2 O and more explicit information about emission factors. Three sources of N 2 O are distinguished in the methodology: (i) direct emissions from agricultural soils, (ii) direct soil emissions from animal production (including stable emissions to be reported under Manure Management (Section 4.2) ), and (iii) N 2 O emissions indirectly induced by agricultural activities. The methodology is an approach which requires only input data available from FAO databases. To retain consistency with the source categories defined in the IPCC Guidelines (1995), not all N 2 O emissions from these sources are reported here. Emissions from animal waste management systems (i.e., before manure is added to soils), and from manure used for fuel, are reported under Section 4.2 and Energy Chapter, respectively, whereas emissions from human sewage are reported in the Waste Chapter. However, the description of the N cycle which produces these N 2 O sources is included in Section 4.5.4 to provide the reader with a coherent picture of the N cycle as related to agricultural soils. Anthropogenic input into agricultural systems include synthetic fertiliser, nitrogen from animal wastes, nitrogen from increased biological N-fixation, and nitrogen derived from cultivation of mineral and organic soils through enhanced organic matter mineralisation. Nitrous oxide may be produced and emitted directly in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff, nitrogen leaching, consumption by humans and introduction into sewage systems which transport the nitrogen ultimately into surface water. Ammonia and oxides of N (NO x ) are also emitted from agricultural systems and may be transported off-site and serve to fertilise other systems which leads to enhanced production of N 2 O. Agricultural systems are considered as being the same throughout the world and this methodology does not take into account different crops, soils and climates which are known to regulate N 2 O production. These factors are not considered because limited data are available to provide appropriate emission factors. Countries which have data to show that default data are inappropriate for their country should include a full explanation for the values used. The method also uses a linear extrapolation between N 2 O emissions and fertiliser nitrogen application and in the indirect emissions section does not account for the probable lag time between nitrogen input and ultimate production of N 2 O as a result of this nitrogen input into agricultural soils. Using midpoint emission factors this current methodology and the FAO data (FAO, 1990a;b), global N 2 O–N emissions for the year 1989 were estimated. Direct emissions

## A GRICULTURE

4.88 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual from agricultural soils totalled 2.5 Tg N, direct emissions from grazing animals totalled 1.6 Tg N and indirect emissions resulting from agricultural nitrogen input into the atmosphere and aquatic systems totalled 1.9 Tg N 2 O–N. These estimates show that each of the three components of agriculture considered contribute about the same amount of N 2 O to the global atmospheric budget. The N 2 O input to the atmosphere from agricultural production as a whole has apparently been underestimated by the previous IPCC methodology by at least 70 per cent.



### 4.5.2 Direct N 2 

### O Emissions from Agricultural Soils (Including Glasshouse Systems Farming and Excluding Effects of Grazing Animals) Anthropogenic sources of N 2 O can be biogenic (e.g., enhanced N 2 O production by bacteria in fertilised fields) or abiogenic (e.g., formation during burning processes). Several studies indicate that anthropogenic sources are largely biogenic, with agriculture as a major contributor (Bouwman et al., 1995; Mosier et al., 1995a;b).
Biogenic production of N 2 O in the soil results primarily from the nitrification and denitrification processes. Simply defined, nitrification is the aerobic microbial oxidation of ammonium to nitrate and denitrification is the anaerobic microbial reduction of nitrate to dinitrogen gas. Nitrous oxide is a gaseous intermediate in the reaction sequences of both processes which leaks from microbial cells into the soil atmosphere. Major regulators of these processes are temperature, pH and soil moisture content.
In most agricultural soils, biogenic formation of N 2 O is enhanced by an increase in available mineral nitrogen, which in turn increases nitrification and denitrification rates. Addition of fertiliser N, therefore, directly results in extra N 2 O formation. Most studies on N 2 O emissions from agricultural soils investigate the difference in N 2 O production between fertilised and unfertilised fields. Emissions from unfertilised fields are considered background emissions. However, actual background emissions from agricultural soils may be higher than historic natural emissions as a result of enhanced mineralisation of soil organic matter. This is particularly observed in organic soils in both cold and warm climates over the globe (Bouwman and van der Hoek, 1991; Kroeze, 1994). Background emissions may also be lower than historic emissions due to depletion of soil organic matter (Groffman et al., 1993).



### O VERVIEW OF 

### S OURCES

Introduction The following sources and sink of N 2 O can be distinguished.

• Synthetic fertilisers;

• Animal excreta nitrogen used as fertiliser;

• Biological nitrogen fixation;

• Crop residue and sewage sludge application;

• Glasshouse farming;

• Cultivation of high organic content soils;

• Soil sink for N 2 O.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.89 All of these N 2 O sources are included in the methodology, except for sewage sludge application and the soil sink for N 2 O. These sources and sinks are not estimated because emissions are negligible or data are insufficient.

Synthetic fertilisers Synthetic fertilisers are an important source of N 2 O. The amount of synthetic fertiliser nitrogen applied to agricultural fields world-wide is well documented in the FAO database (FAO Annual Fertiliser Yearbook). Studies on fertiliser-induced N 2 O emissions have been revised by Bouwman (1994,1995), Cole et al. (1995), Mosier (1994) and Mosier et al. (1995a;b). Conversion factors used by Cole et al. (1995) and Mosier et al. (1995b) are recommended. This recommendation is based on discussions conducted during the preparation of the Cole et al. (1995) document and from Bouwman (1994) who estimated that 0.0125 ± 0.01 of the applied nitrogen was directly emitted as N 2 O (see Table 4-18). This range encompasses more than 90 per cent of the published field emission values summarised in Bouwman (1994). Note that most of the information in Bouwman's summary is derived from field studies conducted in temperate regions of the world since few annual flux measurements have been made in tropical agricultural systems.

TABLE 4-18 D EFAULT EMISSION FACTORS FOR DIRECT EMISSIONS OF N 2 O

EF 1 (fraction of N-input, kg N 2 O-N/kg N) 0.0125 (0.0025-0.0225) a

EF 2 (kg N 2 O-N/ha/yr) 5 temperate and 10 tropical (2-15) a

a Indicates range
Animal excreta nitrogen used as fertiliser Although the amount of nitrogen used as fertiliser from animal excreta is more uncertain than the amount of synthetic fertiliser used, estimates can be made, based on animal population and agricultural practices, as shown in Section 4.5.3 of this Chapter (Table B-1, Appendix B). To account for the loss of fertiliser from NH 3 volatilisation and emission of nitric oxide (NO) through nitrification after fertiliser is applied to fields, NH 3 volatilisation and NO emission factors are needed. Even though climate, soil, fertiliser placement and type, and other factors influence NH 3 volatilisation and NO x emissions, a default emission factor of 0.1 (kg NH 3 –N + NO x –N emitted/kg N applied) can be used for synthetic fertilisers and 0.2 (kg NH 3 –N + NO x –N emitted/kg N applied) for animal waste fertiliser (Table 4-19) (0.2 is used for animal waste because of the potentially larger NH 3 volatilisation; see Section 4.5.4). The amount of nitrogen from these sources available for conversion to N 2 O is therefore equal to 90 per cent of the synthetic fertiliser nitrogen applied and 80 per cent of the animal waste nitrogen applied (Schepers and Mosier, 1991). Biological nitrogen fixation Although the amount of nitrogen fixed by biological nitrogen fixation in agricultural systems can be estimated, the N 2 O conversion coefficient is even less certain. Biological nitrogen fixation (BNF) supplies globally some 90 to 140 Tg N/yr to agricultural systems (Peoples et al., 1995). Although more verification of these figures is necessary, all indications are that BNF contributes more nitrogen for plant growth than the total amount of synthetic nitrogen fertilisers applied to crops each year (Danso, 1995). The IPCC Guidelines (1995) mention equal rates. On average, BNF supplies 50-60 per cent of

## A GRICULTURE

4.90 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual the nitrogen harvested in grain legumes, 55-60 per cent of the nitrogen in nitrogen fixing trees and 70-80 per cent of the nitrogen accumulated by pasture legumes (Danso, 1995). Cultivation of grain legumes, however, often results in net soil nitrogen depletion. In the tropics and subtropics, the use of Azolla (a genus of aquatic ferns which contains an N 2 -fixing cyanobacterium) is widespread. Azolla fixes 20-25 kg N/ha (Kumarasinghe and Eskew, 1991) which is released upon decomposition. This nitrogen serves to fertilise an associated crop and eventually to stimulate N 2 O formation. Galbally et al. (1992) and Bouwman and Sombroek (1990) indicate that legumes may contribute to N 2 O emission in a number of ways. Atmospheric N 2 fixed by legumes can be nitrified and denitrified in the same way as fertiliser N, thus providing a source of N 2 O. Additionally, symbiotically living Rhizobia in root nodules are able to denitrify and produce N 2 O (O'Hara and Daniel, 1985). Galbally et al. (1992) suggest an emission rate of 4 kg N/ha/yr from improved pastures, and Duxbury et al. (1982) suggest that legumes can increase N 2 O emissions from pastures by a factor of 2 or 3. More recently Carran et al. (1995) found annual N 2 O emissions ranging from 0.5 to 5 kg N 2 O–N depending upon the relative fertility of the sampling location. In old and young rye grass/clover pastures Muller (personal communication) observed N 2 O emissions of 0.7 and 0.3 kg N/ha/yr, respectively. The absolute amount of nitrogen fixed by a crop is also very uncertain (Peoples et al., 1995.). Because of this uncertainty and the paucity of country data on N-fixing crops, it is difficult to assign a conversion factor for N 2 O emissions derived from nitrogen fixation. Total nitrogen input (F BN , Equation 1) is estimated by assuming that total crop biomass is about twice the mass of edible crop (FAO, 1990b), and a certain nitrogen content of nitrogen fixing crop (Frac NCRBF , Table 4-19). A residue/crop ratio of 1 is assumed. For specific crops, ratios can be obtained from Table 4-17. This crop production is defined in FAO crop data bases as pulses and soybeans. The N-fixation contribution does not include N 2 O produced in legume pastures. This N 2 O production is at least partially accounted for in emissions from pastures that are being grazed (Section 4.5.3). Australia and New Zealand, for example, contain large areas of pasture land that in cludes legumes as part of the pastoral system. Little data are available for other parts of the globe (Mosier et al., 1995b). Crop residue and Sewage sludge application There is only limited information concerning re-utilisation of nitrogen from crop residues and nitrogen from sewage sludge applied to agricultural lands. Although the amount of nitrogen that recycles into agricultural fields through these mechanisms may add 25-100 Tg of N/yr of additional nitrogen into agricultural soils (mainly from crop residues) the amount converted to N 2 O is not known. To account for the N 2 O in the inventorybudget the emission factor for fertilisers is used as default and the amount of nitrogen reentering cropped fields through crop residues is calculated from the FAO crop production data. Because no appropriate estimates of sewage sludge nitrogen used as fertiliser were found, this nitrogen input is not discussed further (FAO, 1978-1981). Nitrous oxide emissions associated with crop residue decomposition are calculated here by estimating the amount of nitrogen entering soils as crop residue (F CR ). The amount of nitrogen entering the crop residue pool is calculated from crop production data. Since FAO data that can be used for this purpose only represent the edible portion of the crop, these must be roughly doubled to estimate total crop biomass. We then can assume a nitrogen percentage (Frac NCRBF and Frac NCR0 ; Table 4-19) to convert from kg dry biomass/yr to kg N/yr in crops. Some countries may have sufficient information to define the nitrogen content of crop biomass more precisely. As a default we suggest distinguishing between N-fixing crops (pulses and soybeans) and non-N-fixing crops.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.91 Some of the crop residues is removed from the field as crop (approximately 45 per cent), and some may be burned (approximately 25 per cent of the remaining residue in developing countries), or fed to animals.

Glasshouse farming N-fertiliser application to glasshouse-grown crops are typically high and nitrogen not recovered in the crops is frequently low (Postma et al, 1994). The available data are limited in scope, but three sets of studies indicate that N 2 O emissions from glasshouse crops may be relatively small. Postma et al. (1994) quantified NH 3 and N 2 O emissions from glasshouse cultivation of lettuce on a sandbed and found that NH 3 emissions and N 2 O emitted directly or in drainage water totalled less than 0.01 kg N/kg of nitrogen applied. Daum (personal communication, 1995) measured N 2 O emissions from soil-less culture cucumbers and found that N-loss rates as N 2 O ranged between 0.004 and 0.009 kg N/kg of nitrogen input into the culture system. Pollaris (1994) measured N 2 O emission in a glasshouse cultivation of tomato and lettuce and found respectively 0.007 and 0.014 kg of each kg of applied nitrogen emitted as N 2 O. The importance of another factor, N 2 O emission during steam disinfection of glasshouse soils, is uncertain. Postma (personal communication, 1995) found that 2-25 kg N 2 O-N/ha were lost during 10-hours following soil steaming. The extent of glasshouses to which this practice is applied is not known. Overall, these data suggest that N 2 O emissions from glasshouse agriculture do not need to be included separately in N 2 O emission inventories but should be included only in the total fertiliser nitrogen consumed within each country. Emissions from glasshouse agriculture is, therefore, not discussed further.

Cultivation of high organic content soils Large N 2 O emissions occur as a result of cultivation of organic soils (Histosols) due to enhanced mineralisation of old, N-rich organic matter (Guthrie and Duxbury, 1978; Klemedtsson, personal communication, 1995). The rate of N-mineralisation is determined by the N-quality of the Histosol, management practices and climatic conditions. The range for enhanced emissions of N 2 O due to cultivation is estimated to be 2-15 kg N 2 O-N/ha/yr of cultivated Histosol. Default emission values of 5 and 10 kg N 2 O-N/ha/yr are suggested for temperate and boreal, and tropical regions, respectively (Table 4-18). If better country values are available they should be used.

Soil sink for N 2 O Aerobic soils are typically sources for N 2 O, but small uptake rates have been observed in isolated instances in dry soils (Duxbury and Mosier, 1993) and in wet grass pastures (Ryden, 1981; 1983). In a seasonally burned “cerrado’ in Brazil, Nobre (1994) observed occasional small but inconsistent consumption rates and concluded that this sink was very small in these soils. Anaerobic soils have a large potential for reducing N 2 O to N 2 (Erich et al., 1984), since the major product of denitrification in soils is usually N 2 rather than N 2 O. However, no large, constant N 2 O uptake has been reported, and flooded rice fields (Parashar, 1991), for example, generally show very small emissions, depending upon the time of cropping season (Minami and Fukushi, 1984). Apparently slow rates of dissolution and transport of atmospheric N 2 O in wet or flooded soils prevent this process from being a significant regulator of atmospheric N 2 O. Until additional information is available to indicate that soil uptake, in aerobic or flooded soils, is important, soil uptake of atmospheric N 2 O will not be included in the N 2 O budget for agricultural systems.

## A GRICULTURE

4.92 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### M ETHODOLOGY FOR 

### E STIMATING 

### D IRECT 

### N 2 

### O E MISSIONS FROM 

### A GRICULTURAL 

### F IELDS 

### .
The Revised IPCC 1996 Methodology for assessing direct N 2 O emissions from agricultural fields includes consideration of synthetic fertiliser (F SN ), nitrogen from animal waste (F AW ), enhanced N 2 O production due to biological N-fixation (F BN ), nitrogen from crop residue mineralisation (F CR ) and soil nitrogen mineralisation due to cultivation of Histosols (F OS ). For futher information see: Bouwman (1994, 1995); Mosier (1994); Mosier et al. (1995a;b).

In this estimate, the total direct annual N 2 O emission is:

E QUATION 1 N 2 O DIRECT = [(F SN + F AW + F BN + F CR ) x EF 1 ] + F OS x EF 2 where:

N 2 O DIRECT = direct N 2 O emissions from agricultural soils in country (kg N/yr);

EF 1 = emission factor for direct soil emissions (kg N 2 O-N/kg N input) (see Table 4-18);

EF 2 = emission factor for organic soil mineralisation due to cultivation (kg N 2 O-N ha/yr) (see Table 4-18);

F OS = area of cultivated organic soils within country (ha of histosols in FAO data base); F AW = manure nitrogen used as fertiliser in country, corrected for NH 3 and NO x emissions and excluding manure produced during grazing (kg N/yr); F BN = N fixed by N-fixing crops in country (kg N/yr);

F CR = N in crop residues returned to soils in country (kg N/yr);

F SN = synthetic nitrogen applied in country (kg N/yr);

F SN = N FERT x (1-Frac GASF );

F AW = (Nex x (1-(Frac FUEL + Frac GRAZ + Frac GASM ));

F BN = 2 x Crop BF x Frac NCRBF ;
F CR = 2 x [Crop 0 x Frac NCR0 + Crop BF x Frac NCRBF ] x (1-Frac R ) x (I-Frac BURN ); and
N FERT = synthetic fertiliser use in country (kg N/yr);

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.93 Frac GASF = fraction of synthetic fertiliser nitrogen applied to soils that volatilises as NH 3 and NO x (kg NH 3 -N and NO x -N/kg of N input) (see Table 4-19);

N ex = amount of nitrogen excreted by the livestock within a country (kg N/yr) (see Table 4-20);

Frac FUEL = fraction of livestock nitrogen excretion contained in excrements burned for fuel (kg N/kg N totally excreted)

Frac GRAZ = fraction of livestock nitrogen excreted and deposited onto soil during grazing (kg N/kg N excreted) country estimate;

Frac GASM = fraction of livestock nitrogen excretion that volatilises as NH 3 and NO x (kg NH 3 -N and NO x -N/kg of N excreted) (see Table 4-19);
Crop BF = seed yield of pulses + soybeans in country (kg dry biomass/yr);

Frac NCRBF = fraction of nitrogen in N-fixing crop (kg N/kg of dry biomass) (see Table 4-19);
Crop 0 = production of all other (i.e., non-N fixing) crops in country (kg dry biomass/yr);

Frac NCR0 = fraction of nitrogen in non-N-fixing crop (kg N/kg of dry biomass) (see Table 4-19);

Frac R = fraction of crop residue that is removed from the field as crop (kg N/kg crop-N) (see Table 4-19);

Frac BURN = fraction of crop residue that is burned rather than left on field (see Table 4-19).
The input data needed for this methodology include synthetic fertiliser use (N FERT ), manure-N used as fertiliser (F AW ), edible crop production of N-fixing crops (Crop BF ) and non-N-fixing crops (Crop 0 ), and area of cultivated organic soils (Histosols) in the country. The data for synthetic fertiliser use are available on a country basis in the FAO data base (e.g., FAO, 1990a) and the amount of nitrogen in animal waste applied to agricultural fields (F AW ) is calculated from the number and type of animals within a country (see Section 4.5.3) and an in-country estimate of the percentage of nitrogen excreted by farm animals that is reapplied to the field. Both synthetic fertiliser and manure used as fertiliser need to be corrected for the amount of NH 3 volatilised and NO x emitted (10 and 20 per cent of nitrogen applied, respectively) after the material is placed in or on the soil so that the same nitrogen atom is not counted again in Section 4.5.4. The F AW data also need to be carefully evaluated for each country to be sure that animal waste used to fertilise crops and animal waste deposited on pastures while animals are grazing (accounted for in Section 4.5.3) are not double counted. Crop production data for pulses and soybeans and non-N-fixing crops are listed in the FAO crop data base (FAO, 1990b). Residue remaining on the field may not always total 55 per cent of total crop biomass. If more appropriate biomass and N content numbers are available within a country they should be used. The area of histosol can be obtained from FAO Databases (e.g., FAO, 1991).

## A GRICULTURE

4.94 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual TABLE 4-19 D EFAULT VALUES FOR PARAMETERS

Frac BURN 0.25 in developing and 0.10 or less in developed countries (kg N/kg crop-N);

Frac R 0.45 kg N/kg crop-N;

Frac FUEL 0.0 kg N/kg N excreted a ;
Frac GASF 0.1 kg NH 3 -N + NO x -N/kg of synthetic fertiliser N applied;

Frac GASM 0.2 kg NH 3 -N + NO x -N/kg of N excreted by livestock;

Frac GRAZ Table 4-21, Column Pasture range and Paddock a ;
Frac NCRBF 0.03 kg N/kg of dry biomass;

Frac NCR0 0.015 kg N/kg of dry biomass.

a Countries are recommended to obtain country specific data.


### 4.5.3 Direct soil emissions of N 2 

### O from animal production (including stable emissions to be reported under Manure Management)

O VERVIEW OF 

### S OURCES Recent studies (e.g., Bouwman, 1995; Jarvis and Pain, 1994; Flessa et al., submitted; Mosier et al., 1995a;b) indicate that emissions from animal wastes can be significant. There are three potential sources in animal production, (a) animals themselves, (b) animal wastes during storage and treatment, and (c) dung and urine deposited on the soil by grazing animals. Although N 2 O emissions from animals are described, they are not accounted for here as these are minor sources on a global scale and because such emissions are not a source of N 2 O emissions from soil. The second source includes possible losses during spreading operations. Emissions from manure stored in animal waste management systems (i.e., before it is added to soils), however, must be reported under Manure Management (Section 4.2). The final source, from grazing animals, is included in the agricultural soils because the dung and urine are considered as fertilisers.
A) N 2 O from animals
Animals themselves may be very small sources of N 2 O. Animal fodders contain 10 to 40 g of nitrogen (N)/kg dry matter. The greater part of this nitrogen is organically bound, but as total nitrogen content increases so does the nitrate (NO 3 ) content, generally. Nitrate contents in fodders generally range from 1-10 g/kg dry matter (Spoelstra, 1985). Upon passage through the digestive track of the animal, nitrate is reduced via dissimilatory nitrate reduction to NH 3 /NH 4 + . The nitrate reduction reaction may release small amounts of N 2 O in the gut (Kaspar and Tiedje, 1981), which may escape to the atmosphere during rumination. Though this possible route of N 2 O formation has been known for over 10 years, quantitative data in terms of N 2 O release are still lacking todate. The total amount of N 2 O released by cattle is probably very small, because the gut is highly anoxic and this will favour the formation of NH 3 /NH 4 + (Tiedje, 1988). Direct losses from animals themselves are likely to be very small and are therefore not discussed further.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.95 B) N 2 O emissions from animal waste management systems
The proportion of total nitrogen intake that is excreted and partitioned between urine and faeces is dependent on the type of animal, the intake of dry matter, and the nitrogen concentration of the diet (Whitehead, 1970). The retention of nitrogen in animal products, i.e., milk, meat, wool and eggs, ranges from about 5 to 20 per cent of the total nitrogen intake, generally. The remainder is excreted via dung and urine. For sheep and cattle, faecal excretion is usually about 8g/N/kg dry matter consumed, regardless of the nitrogen content of the feed (Barrow and Lambourne, 1962). The remainder of the nitrogen is excreted in the urine and as the nitrogen content of the diet increases, so does the proportion of nitrogen in the urine. In animal production systems, where animal intake of nitrogen is high, more than half of the nitrogen is excreted as urine. For instance, sheep grazing grass/clover pastures in New Zealand have 70-75 per cent of excreted nitrogen in the urine (Haynes and Williams, 1993), whereas dairy cows in the Netherlands excrete 60-65 per cent of nitrogen in urine (Van Vuuren and Meijs, 1987). There are small amounts of mineral nitrogen in faeces but the bulk of the nitrogen is in organic form. About 20-25 per cent of faecal nitrogen is water soluble, 15-25 per cent is undigested dietary nitrogen and the remaining 50-65 per cent is present in bacterial cells (Haynes and Williams, 1993). The organically bound nitrogen in faeces must be mineralised to NH 3 /NH 4 + , before it can be the substrate of nitrifiers and denitrifiers and hence, a source of N 2 O. Mineralisation of the water soluble organic nitrogen compounds and parts of the organic nitrogen compounds from bacterial cells is rapid, generally, leading to an increase in the amount of NH 3 /NH 4 + in animal wastes during storage. The concentration of nitrogen in urine varies widely because of factors such as nitrogen content in the diet and consumption of water. Typically over 70 per cent of the nitrogen in urine is present as urea and the rest consists of amino acids and peptides. Excretions of poultry contains uric acid as dominant nitrogen compound. The hydrolysis of both urea and uric acid in urine patches to NH 3 /NH 4 + is very rapid, both in the pasture and in animal housings. Fresh urine and dung contain no nitrate; all nitrogen in wastes is in reduced forms.
Production of N 2 O during storage and treatment of animal wastes can occur via combined nitrification-denitrification of ammoniacal nitrogen contained in the wastes. The amount released depends on the system and duration of waste management. As fresh dung and slurry is highly anoxic and well-buffered with near neutral pH, one would expect N 2 O production to increase with increasing aeration. Aeration initiates the nitrification-denitrification reactions, and hence makes release of N 2 O possible. Unfortunately, there is not enough quantitative data to derive a relationship between the degree of aeration and N 2 O emission from slurry during storage and treatment.
Losses of N 2 O from cattle slurry during storing for up to 6 months, with two minutes of gentle mixing twice a week, were below detection limit (10 -4 kg N 2 O N/kg nitrogen in slurry during 6 months (Oenema and Velthof, 1993). N 2 O losses from a natural vented cubicle housing with 60 dairy cows and a concrete floor with frequent removal of wastes with a scarper system were also below the detection limit (2. 10 -4 kg N per kg nitrogen excreted) (Velthof et al., submitted a;b). Heinemeyer (unpublished results) measured N 2 O losses from different housing systems for pigs. He obtained the following preliminary, results from the various housing systems: 6 10

- 4 -11 10 -4 kg N 2 O-N/kg nitrogen excreted for full and half slit floor, and reduced and deep litter; 7.4 10 -3 kg N 2 O-N/kg nitrogen excreted for deep litter combined with compost; and 3.3 10 -3 kg N 2 O-N/kg nitrogen excreted for manure piles. The slightly larger losses from the deep litter/compost and manure pile could be due to the effects of aeration. Groenestein et al. (1993) reported that more than 0.15 kg N/kg nitrogen in pig

## A GRICULTURE

4.96 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual slurry was emitted as N 2 O from deep-litter systems for fattening pigs during a 4-month measuring period. Large N 2 O losses may also occur during aerobic treatment of pig slurry. Burton et al. (1993) found that approximately 0.05 kg N/kg nitrogen in slurry was lost as N 2 O during a four-day treatment period.
Losses of N 2 O from large lagoons with pig slurry in south-eastern United States were negligible (Harper, personal communication). Concentration profiles of N 2 O above the lagoon suggest that absorption of N 2 O from the atmosphere by the pig slurry in the lagoon may occur.
Losses of N 2 O from muck heaps were measured by Sibbesen and Lind (1993). They arrived at a tentative estimate of 8 10 -3 kg/kg nitrogen in the dung heap/yr. Recent results indicate that losses were much larger during warm periods, as in the summer of 1995, than during colder conditions (Lind, personal communication, 1995). In a study on total N 2 O emission from The Netherlands, Kroeze (1994) included N 2 O emissions from stables. She distinguished four classes, kg N 2 O-N/kg nitrogen in the waste: class 1 (<0.002) for anaerobic storage of waste; Class 2 (0.002-0.0125) for none of the types of storage in the Netherlands; Class 3 (0.0125-0.025) for biological treatment of calf veal manure and Class 4 (>0.025) for deep-litter stables, nitric-acid-treated slurry. Jarvis and Pain (1994) and Bakken et al. (1994) made inventories of N 2 O emissions from livestock holdings, but did not include N 2 O emissions from animals and animal waste storage. Other studies (Bouwman et al., in press; Mosier et al., 1995b; Flessa et al., submitted) assign an emission factor to nitrogen from animal slurry. No explicit distinction was made between N 2 O emission from wastes during storage and treatment, and N 2 O emission from wastes after deposition or spreading onto the land. In conclusion, there is very limited information available on N 2 O emissions from animals and from animal waste during storage and treatment. Moreover, there is a wide range in estimated losses, when expressed in N 2 O N/kg nitrogen in the waste. Losses from animal waste during storage range from <10 -4 kg N for slurries to >0.15 kg N/kg nitrogen in the pig waste in deep-litter stables. Although N 2 O production may be affected by waste spreading and waste processing, available data are too scarce to base a new method on.

C) N 2 O from animal grazing
A brief summary of estimates of N 2 O emissions derived from dung and urine deposits of grazing animals is compiled in Appendix A, Table A-1. The N 2 O emission is expressed as gN/kg of the nitrogen in urine and/or dung. Two types of studies may be distinguished. The first type focuses on emissions from a well-defined urine and/or dung patch. A control treatment is generally included, to facilitate the calculation of urine and dung derived emissions. The grazed grassland is the focus in the second type of studies. Grazing derived emissions can be obtained properly when a non-grazing treatment is included. For the purpose of this compilation we consider that grazing derived emissions are similar to 'dung and urine derived' emissions. This may not be completely true, because grazing animals have also other effects than deposition of dung and urine, for example, compaction of the soil by trampling, increased turnover of nitrogen from stubble and roots, etc. The duration of the studies ranged from 1 week up to 2 years. Though the bulk of the N 2 O will be lost shortly after deposition in the field, significant amounts may still be released from the urine and dung even after a couple of weeks after deposition. Hence, short-term studies may underestimate the total N 2 O losses from animal excrements (Van Cleemput et al., 1994; Velthof et al., submitted a;b).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.97 Grazing derived emissions range from 0.002 to 0.098 kg N 2 O–N/kg of nitrogen excreted (Koops et al., 1995; Muller et al., 1995a;b). The lower estimates are from well-drained unfertilised grassland soils in New Zealand. Carran et al. (1995) examined five plots, ranging from well drained high-fertile plots to poorly drained low-fertility plots. They did not provide grazing derived emissions, probably because they did not include non-grazing treatments. However, they provided data on annual dry matter yields. Assuming a mean grazing efficiency in their grazing trials of 80 per cent, for both bulls and sheep, a nitrogen content in the clover/grass mixture of 30 g/kg dry weight, and a low background emission (20 per cent of the grazing trials), the grazing derived N 2 O emissions are likely in the range of 0.002-0.01 kg N 2 O–N/kg nitrogen excreted, which is rather low. Large grazing derived emissions, induced by livestock nitrogen excretion, were obtained on drained peat soils in the Netherlands. These intensively managed grassland on peat soils have also a large background emission and a large fertiliser derived emission (Velthof and Oenema, 1995). Nearly all data pertain to temperate areas, with intensively managed grassland. The nitrogen contents of dung and especially urine are higher from this intensively managed grassland than from less intensively managed (sub)tropical grasslands. The fraction of easily hydrolysable nitrogen, i.e., urea and uric acid, is much smaller in dung and urine from animals fed with a low nitrogen content ration than from animals fed with a high nitrogen content ration. This difference will probably result in a different emissions factor. Unfortunately, data are lacking to sustain this hypothesis. Differences in climate, i.e., rainfall and temperature patterns, may also have a significant effect. Moist and warm environments facilitate the ammonification of organically bound nitrogen in urine and dung, and subsequently, nitrification and denitrification. As a result, the effect of a relatively low ratio of easily hydrolysable nitrogen versus total nitrogen in urine and dung in low-intensity managed tropical pastures may be compensated for by the effects of temperature and moisture, to some extent. However, this is speculative since little data exist to substantiate this proposition. Nitrogen losses as N 2 O are probably lower in arid and semiarid regions and in colder climates such as Sweden. Mosier and Parton (1985) found that during the course of a year per kg of urea–N from simulated urine patches, only 0.006 kg N 2 O–N was emitted as N 2 O. They did find in later studies that N 2 O emissions remained detectably higher 10 years after the urea had been applied to the semi-arid shortgrass prairie (Mosier et al., 1991). An overall reasonable average emission factor for animal waste excreted in pastures is 0.02 kg N 2 O–N/kg of nitrogen excreted. This emission factor is likely applicable for all regions of the world and for all types of animals.



### M ETHODOLOGY FOR 

### E STIMATING 

### N 2 

### O FROM 

### A NIMAL 

### P RODUCTION As already discussed there are three potential sources of N 2 O emissions related to animal production. These are (a) animals themselves, (b) animal wastes during storage and treatment, (c) dung and urine deposited by free-range grazing animals. N 2 O emissions emitted directly from animals are not reported here. Emissions from manure applied to agricultural soils from stables (e.g., daily spreading) and from grazing animals (pasture range and paddock) are considered to be emissions from agricultural soils. N 2 O emissions from other animal waste management systems (AWMS) are not directly

## A GRICULTURE

4.98 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual attributable to soils and are reported under Manure Management (Section 4.2). Emissions from manure used as fuel should be reported in the Energy Chapter. Nonetheless, all sources of N 2 O from animal production and agricultural soils are described here as part of the N-cycle. Caution must be applied in reporting N 2 O emissions under the appropriate source categories defined above.

E QUATION 2
N 2 O ANIMALS = N 2 O( AWMS )= ∑ [ N (T) x Nex (T) x AWMS (T) x EF 3(AWMS) ]

where:

N 2 O ANIMALS = N 2 O emissions from animal production in a country (kg N/yr) N 2 O (AWMS) = N 2 O emissions from Animal Waste Management Systems in the country (kg N/yr); = [N (T=1) x Nex (T=1) x AWMS (T=1) x EF 3(AWMS) ]+ ... + [N (T=TMAX) x Nex (T=TMAX) x AWMS (T=TMAX) x EF 3(AWMS) ] ;

N (T) = number of animals of type T in the country;

Nex (T) = N excretion of animals of type T in the country (kg N/animal /yr); (see Table 4-20);

AWMS (T) = fraction of N EX(T) that is managed in one of the different distinguished animal waste management systems for animals of type T in the country; (see Table 4-21);

EF 3(AWMS) = N 2 O emission factor for an AWMS (kg N 2 O-N/kg of Nex in AWMS); (see Table 4-22);
T = type of animal category;

Nitrogen excretion General statistics about animal numbers are provided by FAO and detailed information is available for many countries. Default values are provided in Table 4-20, which was compiled on the basis of data provided by Ecetoc (1994), and references therein, Vetter et al. (1989), Steffens and Vetter (1990). There are still uncertainties in the values listed in Table 4-20. Estimates for cattle and swine may be too high. Hence, these estimates (default values) need further attention. The excretion data are in reasonable agreement with Bouwman (in press), although some of the excretion factors as given by Bouwman (in press) are lower than the factors in Table 4-20. Once available, countries may chose to use nitrogen excretion data from the Ammonia Expert Panel of the UN-ECE task force on emission inventories. For some countries it may be desirable to distinguish other animal types than indicated in Table 4-20. If such country values are available they should be used.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.99 TABLE 4-20 T ENTATIVE DEFAULT VALUES FOR NITROGEN EXCRETION PER HEAD OF ANIMAL PER REGION ( KG / ANIMAL / YR ) A Region Type of Animal

Nondairy cattle Dairy cattle Poultry Sheep Swine Other animals

North America 70 100 0.6 16 20 25 Western Europe 70 100 0.6 20 20 25 Eastern Europe 50 70 0.6 16 20 25
Oceania 60 80 0.6 20 16 25
Latin America 40 70 0.6 12 16 40
Africa 40 60 0.6 12 16 40

Near East & Mediterranean 50 70 0.6 12 16 40

Asia & Far East 40 60 0.6 12 16 40

a Source: Ecetoc (1994), Vetter et al. (1988), Steffens and Vetter (1990).

Animals as direct source of N 2 O Current available information suggests that some N 2 O may be released directly from animals. However, the rate of release is probably low. A value less than 0.1 g N 2 O–N/kg nitrogen excreted would result in a global N 2 O emission of less than 0.1 Tg, which suggests that animals are a minor source. This source is therefore not included in the methodology.

Animal Waste Management Systems The types of Animal Waste Management System (AWMS) distinguished by Safley et al. (1992) and their compilations for a large number of countries are proposed for this methodology. Descriptions of these management systems can be found Table 4-8. Tables 4-21 and 4-6 can be used to estimate nitrogen excretion per AWMS. The AWMS is an important regulating factor in N 2 O emission from animal wastes during storage and treatment. The data provided per country in Safley et al. (1992) could be used for estimating N 2 O emissions from animal wastes. Significant differences in emission factors are expected between some of the AWMS.

There are several AWMS considered here:

• Anaerobic lagoons;

• Liquid systems;

• Daily spread;

• Solid storage and drylot;

• Pasture range and paddock;

## A GRICULTURE

4.100 R evised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • Used for fuel;

• Other systems.
N 2 O emissions from all AWMS are reported under Manure Management (Section 4.2), with three exceptions:

• stable manure that is applied to agricultural soils ( e.g., daily spread);

• dung and urine deposited by grazing animals on fields (pasture range and paddock);

• manure used for fuel. The first of these sources is captured in the methodology for estimating direct emissions from agricultural soils (Section 4.5.2). The second source is reported under direct soil emissions of N 2 O from animal production (Section 4.5.3). The third source, manure used as fuel, is reported in the Energy Chapter.
The class "used for fuel" is not included here as a source of N 2 O, because this possible source of N 2 O is considered an energy-related emission. Nevertheless, countries should estimate the amount of manure nitrogen that is used as fuel, because that amount is not applied to soils. A problem exists for the class 'Used for fuel', as it includes 'anaerobic digesters'. Moreover, it is the dung that is used for fuel and not the urine. These two factors may lead to a possible overestimation of the amount of N 2 O emitted from wastes in the class 'Used for fuel', if not properly corrected. While significant N 2 O losses may occur during burning, no N 2 O losses are expected from anaerobic digesters. Anaerobic digesters are used especially in Asia. Data of Erda Lin (personal communication, 1995) suggest, however, that only 0.5 per cent of the total amount of animal wastes in China are used in anaerobic digesters.4AGRICULTURERevised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.101TABLE4-21DEFAULTVALUES FORPERCENTAGE OFMANUREN PRODUCED INDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS(FROMSAFLEY ET AL., 1992)Region Type of Animal % of Manure Production per Animal Waste Management SystemsAnaerobicLagoonLiquidSystemDailySpreadSolid Storageand DrylotPasture Rangeand PaddockUsed Fuel OtherSystemNorth America Non-dairy Cattle (D) 0 1014 84 0 1Dairy Cattle 10 233723 0 0 7Poultry (E) 5 400 1 0 90Sheep 0 002 88 0 10Swine 25 50018 0 0 6Other animals (F) 0 000 92 0 8Western Europe Non-dairy Cattle (D) 0 5502 33 0 9Dairy Cattle 0 462421 8 0 1Poultry (E) 0 1301 2 0 84Sheep 0 002 87 0 11Swine 0 77023 0 0 0Other animals (F) 0 000 96 0 4Eastern Europe Non-dairy Cattle (D) 8 39052 0 0 1Dairy Cattle 0 18167 13 0 0Poultry (E) 0 2800 1 0 71Sheep 0 000 73 0 27Swine 0 2900 27 0 45Other animals (F) 0 000 92 0 8AGRICULTURE4.102Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLE4-21 (CONTINUED)DEFAULTVALUES FORPERCENTAGE OFMANUREN PRODUCED INDIFFERENTANIMAWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS(FROMSAFLEY ET AL., 1992)Region Type of Animal % of Manure Production per Animal Waste Management SystemsAnaerobicLagoonLiquidSystemDailySpreadSolid Storageand DrylotPasture Rangeand PaddockUsedFuelOther SystemOceania Non-dairy Cattle (D) 0 0 0 01000 0Dairy Cattle 0 0 0 01000 0Poultry (E) 0 0 0 030 98Sheep 0 0 0 01000 0Swine 55 0 0 1700 28Other animals (F) 0 0 0 01000 0Latin America Non-dairy Cattle (D) 0 0 0 0990 1Dairy Cattle 0 1 62 1360 0Poultry (E) 0 9 0 0420 49Sheep 0 0 0 01000 0Swine 0 8 2 5100 40Other animals (F) 0 0 0 0990 1Africa Non-dairy Cattle (D) 0 0 1 3960 0Dairy Cattle 0 0 12 0830 5Poultry (E) 0 0 0 0810 19Sheep 0 0 0 1990 1Swine 0 7 0 9300 0Other animals (F) 1 0 0 0990 14AGRICULTURERevised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.103TABLE4-21 (CONTINUED)DEFAULTVALUES FORPERCENTAGE OFMANUREN PRODUCED INDIFFERENTANIMAWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS(FROMSAFLEY ET AL., 1992)Region Type of Animal % of Manure Production per Animal Waste Management SystemsAnaerobicLagoonLiquidSystemDailySpreadSolidStorage andDrylotPastureRange andPaddockUsed Fuel OtherSystemNear East andMediterraneanNon-dairy Cattle (D)0 0 2 0 77 18 2Dairy Cattle0 0 3 3 77 18 0Poultry (E)0 1 0 0 71 0 28Sheep0 0 0 0 100 0 0Swine 0 32 0 68 0 0 0Other animals (F)0 0 0 0 100 0 0Asia and Far East Non-dairy Cattle (D) 0 0 16 14 29 40 0Dairy Cattle 6 4 21 0 24 46 0Poultry (E)1 2 0 0 44 1 52Sheep0 0 0 0 83 0 17Swine 1 38 1 53 0 7 0Other animals (F)0 0 0 0 95 0 5(D) Includes buffalo(E) Includes chickens, turkeys and ducks(F) Includes goats, horses, mules, donkeys and camels

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.104 Tentative (default) emission factors (EF 3 ) for the different AWMS are shown in Table 4- 22. These factors were derived on the basis of a very limited amount of information. Uniform factors for all over the world are proposed. This may be incorrect, as temperature and moisture may have positive effects on the size of the processes and, hence, on losses. However, as animal production systems are found in warmer regions, and low-intensity systems have less easily hydrolysable nitrogen in the excretions discussed above, a uniform factor for all regions would seem appropriate.

TABLE 4-22 T ENTATIVE DEFAULT VALUES FOR N 2 O EMISSION FACTORS FROM ANIMAL WASTE PER A NIMAL W ASTE M ANAGEMENT S YSTEM , KG N 2 O–N/ KG NITROGEN EXCRETED Animal Waste Management System a Emission Factor EF 3 Anaerobic lagoons b 0.001 (<0.002) Liquid systems b 0.001 (<0.001) Daily spread c 0.0 (no range) Solid storage and drylot c 0.02 (0.005-0.03) Pasture range and paddock (grazing) d 0.02 (0.005-0.03)
Used as fuel e Not included in this Chapter Other systems b 0.005

a The fraction of manure nitrogen produced in different Animal Waste Management Systems for cattle, swine and buffalo can be estimated as proposed in Table 4-21, or as given by Safley et al. (1992). b To be reported under “Manure Management”.

c To be reported under “Agricultural Soils” (Workbook, Section 4-6) under direct soil emissions from agricultural fields after spreading. (Emissions are assumed not to occur before spreading). d To be reported under “Agricultural Soils” (Workbook, Section 4-6) under direct soil emissions from animal production.

e To be reported in the Energy Chapter.


### 4.5.4 Indirect N 2 

### O Emissions from Nitrogen Used in Agriculture.

O VERVIEW OF SOURCES The pathways for synthetic fertiliser and manure input that give rise to indirect emissions are considered to be:
A. Volatilisation and subsequent atmospheric deposition of NH 3 and NO x (originating from the application of fertilisers); B. Nitrogen leaching and runoff; C. Human consumption of crops followed by municipal sewage treatment; D. Formation of N 2 O in the atmosphere from NH 3; E. Food processing.
Of these pathways, methodologies for estimating N 2 O emissions from A-C are proposed. Nitrous oxide emissions from human waste are described below. However, these N 2 O emissions are allocated to the Waste Chapter (see Section 6.4, Reference Manual and Workbook). At present, information is insufficient to estimate emissions from D and E.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.105 In order to estimate the associated N 2 O fluxes, the following data are needed:

• Synthetic nitrogen fertiliser consumption (N FERT ). This is available by country from FAO yearbooks and is probably the most reliable piece of input data.

• Livestock nitrogen excretion (N ex ) can be estimated reasonably well from FAO livestock populations and measured kg N/animal/yr excretion factors as given in Table 4-20.

• Crop production (Crop) is available from FAO production yearbooks in kg dry biomass/yr.

• Sewage nitrogen production can be estimated from FAO per capita protein consumption data (PROTEIN) and human population counts (Nr PEOPLE ). Protein consumption may vary by a factor of 2 between countries, e.g., Americans and Indians consume 110 and 55 g protein/person/day, respectively.
Emissions of NH 3 and NO x (kg N/yr) are estimated from fertiliser use and livestock nitrogen excretion.

These N 2 O–N emissions are to be calculated from a country's NO x and NH 3 emissions and nitrogen transported in leaching and runoff, so that all N 2 O formed as a result of NO x and NH 3 emissions and leaching and runoff in country Z are assigned to country Z, even if the actual N 2 O formation takes place in another country. This implies that NO x and NH 3 and nitrogen from leaching and runoff imported into a country is not included in the calculations.
A. Atmospheric deposition of NO x and NH 3 Atmospheric deposition of nitrogen compounds such as nitrogen oxides (NO x ) and ammonium (from NH 3 ) fertilise soils and surface waters and as such enhance biogenic N 2 O formation. However, it is recognised that other sources of atmospheric inputs of N compounds to agricultural soils are important. These sources include fuel combustion, for example. Atmospheric deposition of these sources is not accounted here because only those N emissions originating from the application of fertilisers are presently considered. Indeed, Brumme and Beese (1992) showed that after two decades of atmospheric deposition of acidifying compounds (ammonium and sulphuric acids), N 2 O emissions from German forest soils were enhanced by up to a factor of 5. Reported rates of N 2 O emissions are between 0.002 and 0.016 kg N 2 O–N/kg of the amount of nitrogen deposited onto soils (Bowden et al., 1991; Brumme and Beese, 1992; Kasimir, personal communication). This is within the range of emission factors suggested in Section 4.5.2 for synthetic fertilisers. We therefore propose to calculate N 2 O-N emissions as 0.01 kg N 2 O-N /kg of NO x -N and NH 3 -N emitted annually within a country (EF 4 , Table 4-23).

T ABLE 4-23 D EFAULT EMISSION FACTORS FOR INDIRECT EMISSIONS

EF 4 (N deposition) = 0.01 (0.002-0.02) kg N 2 O-N/kg NH 3 -N and NO X –N emitted
EF 5 (leaching/runoff) = 0.025 (0.002-0.12) kg N 2 O-N/kg N leaching/runoff
EF 6 (sewage) = 0.01 (0.002-0.02) kg N 2 O-N/kg sewage-N produced
Agricultural ammonia emissions can be derived from NH 3 volatilisation studies. Animal manure (dung + urine) is one of the most important sources of NH 3 . According to Van der Hoek (1994), up to 50 per cent of the mineral nitrogen in animal manure (i.e., about

## A GRICULTURE

4.106 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 25 per cent of total N) may be lost shortly as NH 3 after application to soil. He also shows that this percentage depends considerably on the application technique used. Schimel et al. (1986) assumed that, as a minimum estimate, 20 per cent of manure nitrogen applied to soils is volatilised as NH 3 soon after application. The amount of NH 3 volatilised may be lower in acid and near neutral pH soils. According to Bouwman (in preparation), about 25 per cent of livestock nitrogen excretion is emitted as NH 3 worldwide. For synthetic fertilisers Van der Hoek (1994) uses a much lower percentage of only 2 per cent of the nitrogen used in the Netherlands that is lost as NH 3 . Bouwman (in preparation), however, estimated that almost 10 per cent of synthetic fertiliser-N is emitted as ammonia world-wide. Although climate and fertiliser type (e.g., urea or ammonium sulphate) may influence ammonia volatilisation, we use default values for NH 3 and NO x volatilisation: 0.1 kg nitrogen/kg synthetic fertiliser nitrogen applied to soils and 0.2 kg nitrogen/kg of nitrogen excreted by livestock are proposed (Frac GASF and Frac GASM , Table 4-19). B. Leaching and Runoff A considerable amount of fertiliser nitrogen is lost from agricultural soils through leaching and runoff. The leached/runoff nitrogen enters groundwater, riparian areas and wetlands, rivers and eventually the coastal ocean. In many world areas, it is one of the most important inputs of nitrogen to those systems. A WHO/UNEP report (1989) showed that over 10 per cent of European rivers had a nitrate content ranging from 9 to 25 mg nitrate-N/L. Other sources include sewage, industries and atmospheric deposition. Fertiliser nitrogen in ground water and surface waters enhances biogenic production of N 2 O as the nitrogen undergoes nitrification and denitrification. The fraction of the fertiliser and manure nitrogen lost to leaching and surface runoff (Frac LEACH ) may range from range 0.1-0.8 (Seitzinger and Kroeze, in preparation). A value of 0.3 is proposed as default here (Table 4-24). For this purpose total nitrogen excretion is used (Nex) in order to include manure produced during grazing:

E QUATION 3 N LEACH = [N FERT + N EX ] x Frac LEACH

The sum of the emission of N 2 O due to N LEACH in: 1) groundwater and surface drainage (EF 5 -g), 2) rivers (EF 5 -r), and 3) coastal marine areas (EF 5 -e) is calculated to obtain the N 2 O emission factor (EF 5 ) for N LEACH . Although not specified, the total amount of nitrogen eventually denitrified remains the same but some is denitrified in riparian area and wetlands before the nitrogen reaches the ocean. In future assessment methodologies, a separate emission factor should be used in the workbook for each of these three environments.

T ABLE 4-24 D EFAULT VALUES OF PARAMETERS FOR INDIRECT EMISSIONS Frac NPR 0.16 kg N/kg of protein Frac LEACH 0.3 (0.1-0.8) kg N/kg of fertiliser or manure N
Groundwater and surface drainage Supersaturated concentrations of nitrous oxide in groundwater and in surface water draining agricultural lands may occur due to leaching of N 2 O from the soil towards drainage and groundwater, or production during nitrification and/or denitrification of fertiliser nitrogen in the groundwater or drainage ditches. Many factors can affect the amount of N 2 O in these waters including the amount of nitrogen leaching into the

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.107 groundwater, different land use practices, soil types and climate. Fertiliser nitrogen in groundwater or drainage water is primarily in the form of NO 3 -N. A review of the literature indicates that while the range of N 2 O concentrations reported is large, there is some relationship between the concentration of N 2 O-N and NO 3 -N in groundwater and agricultural drainage water. The ratio of N 2 O-N to NO 3 -N concentration in groundwater and agricultural drainage water at over 25 locations in urban, agricultural and woodland areas in Japan, Israel and the United States ranged from 0.0001 to 0.06 (Dowdell et al., 1979; Minami and Fukuski, 1984; Ronen et al., 1988; Minami and Oshawa, 1990; Ueda et al., 1991; Ueda et al., 1993). The ratio of N 2 O-N to NO 3 -N in agricultural drainage ditches and groundwater under agricultural fields ranged from approximately 0.0003 to 0.06. The ratios of N 2 O-N to NO 3 -N in agricultural drainage ditches were generally lower (0.003 or less) than ratios in agricultural groundwater. Rapid loss of N 2 O to the atmosphere may account for the generally lower ratios in drainage ditch water. The ratio of N 2 O-N to NO 3 -N in agricultural groundwater was generally between 0.003 and 0.06, with values between 0.007 and 0.02 common. Assuming that all N LEACH is in the form of NO 3, we recommend a default emission factor of 0.015 (EF 5 -g) for N 2 O from N LEACH in groundwater and drainage ditches, with a range of 0.003 to 0.06. The amount of N 2 O emitted from groundwater (by upward diffusion or following entry of groundwater into surface water through rivers, irrigation, and drinking water) and agricultural drainage water is then estimated as:

E QUATION 4 N 2 O emissions from groundwater and agricultural drainage water

= N LEACH x EF 5 -g

where EF 5 –g = 0.015 kg N 2 O-N/kg N LEACH , assuming that all N 2 O produced in a particular year is emitted during that year.

Rivers Once N LEACH from groundwater and surface water enters rivers, additional N 2 O is produced associated with nitrification and denitrification of N LEACH (Seitzinger and Kroeze, in preparation). It is assumed that minimal denitrification occurs in groundwater and therefore that all N LEACH enters rivers.
Nitrification : N 2 O can be produced during nitrification of N LEACH in rivers. While much of the N LEACH may enter rivers as nitrate, algae and aquatic plants can assimilate the nitrate into organic matter, which is released as ammonia, following decomposition of that organic matter. Ammonia in rivers is rapidly nitrified (Lipschultz et al., 1986). The N LEACH entering rivers nitrifies on average 0.5-3 times during river transport. We assume for our default methodology that all N LEACH entering rivers is nitrified once during river transport. The N 2 O yield (moles N 2 O-N/mol of NO 3 -N) during nitrification is generally between 0.002 and 0.003 at atmospheric oxygen levels (0.2 atm partial pressure); Goreau et al., 1980), although enhanced yields of N 2 O are found at reduced O 2 concentrations (Goreau et al., 1980). While reduced oxygen levels occur in some rivers, especially those with high nutrient inputs, we suggest an N 2 O yield of 0.003 for nitrification.
Denitrification : During river transport a considerable amount of nitrogen is lost via denitrification in riverine sediments. A wide range of denitrification rates has been measured in rivers or streams; rates are generally lowest in unpolluted streams (Duff et al., 1984) with highest rates in polluted rivers/streams (Robinson et al., 1979; Cooper and

## A GRICULTURE

4.108 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Cooke, 1984; Seitzinger, 1988, 1990; Christensen and Soerensen, 1988; Christensen et al., 1989). Estimates of the magnitude of N-removal via denitrification range from 1 to 75 per cent of the external nitrogen inputs based on mass balance models and/or from measurements of denitrification (Seitzinger, 1990). Factors likely to affect the fraction of nitrogen removed by denitrification include length and depth of the river, flow rate, water residence time, oxygen content, organic content of sediments, and season. In a number of rivers denitrification removed 50 per cent of the nitrogen inputs, even over short sections (Kaushik and Robinson, 1976; Hill, 1979, 1981, 1983; van Kessel, 1977; Swank and Caskey, 1982). For the assessment we assume that denitrification removes 50 per cent of N LEACH inputs to rivers. N 2 O associated with denitrification (Jorgensen et al., 1984) is released from river sediments. The ratio of N 2 O:N 2 emitted from river sediments is generally within the range 0.001-0.005, although in heavily polluted sediments yields up to 6 per cent have been observed (Seitzinger, 1988). A constant ratio of 0.005 for N 2 O-N emission to denitrification (N 2 –N production) in rivers is suggested.
In summary, the emission factor for N LEACH in rivers due to nitrification and denitrification [EF 5 -r] is thus equal to 0.005 x N LEACH [for nitrification] plus 0.005 x (N LEACH /2) [for denitrification], or 0.0075 x N LEACH . Therefore, N 2 O-N produced from N LEACH during river transport = N LEACH x (EF 5 -r), where EF 5 -r = 0.0075.

Estuaries Rivers are the major conduit for nitrogen transport to the coastal ocean (via estuaries). As discussed above, half of N LEACH is assumed to be removed by denitrification in rivers in the form of N 2 and N 2 O. The remaining 50 per cent of N LEACH is discharged by rivers to estuaries. Nitrogen inputs to estuaries can undergo nitrification and denitrification, with associated N 2 O production.
Nitrification : Pelagic nitrification rates in estuaries generally range from 0-22 umol/l/d (Berounsky and Nixon, 1993). Estuarine nitrification rates are affected by a number of factors such as ammonia concentrations, temperature (Berounsky and Nixon, 1985 and 1993), oxygen (Helder and DeVries, 1983), suspended particulate matter (Helder and DeVries, 1983; Owens, 1986), and light (Horrigan and Springer, 1990). However, no predictive factor has been developed to estimate pelagic nitrification rates across a range of estuaries. In Narragansett Bay (USA), approximately half of the river inputs of inorganic nitrogen to the Bay were nitrified in the bay (Berounsky and Nixon, 1993; Seitzinger and Kroeze, in preparation). For the assessment methodology, we assume that half of the rivers inputs of N LEACH are nitrified again in estuaries, and that the ratio of N 2 O-N to NO 3 –N produced is 0.005, as discussed above for rivers.
Denitrification : Some of the most extensive studies of denitrification are in estuaries (Kemp et al., 1990; Jenkins and Kemp, 1984; Jensen et al., 1984 and 1988; Smith et al., 1985). A relatively good relationship has been found between denitrification and inorganic nitrogen inputs to estuaries from rivers. The amount of nitrogen removed by denitrification is equivalent to a relatively constant percentage (50 per cent) of inorganic nitrogen inputs to a variety of estuaries (Seitzinger, 1988). Those estuaries vary in a number of characteristics including nitrogen loading rates (25 to 516 x 10 -6 mol N m -2 /h), extent of inter-tidal area (<1 per cent to 50 per cent), and latitude (subtropical to subarctic). For the assessment methodology, 50 per cent of the N LEACH that is carried to estuaries by rivers is denitrified, and the ratio of N 2 O-N to denitrification (N 2 -N) emitted is 0.005, as discussed above for rivers. N LEACH that enters estuaries but is not denitrified, is either buried in the sediments as organic nitrogen or exported to the continental shelf region where additional N 2 O can be produced. Nitrous oxide production associated with this fraction of N LEACH is not accounted for in this methodology.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.109 In summary, the Phase II methodology assumes the following: 1) half of the N LEACH is transported to estuaries by rivers, 2) half of the N LEACH in estuaries is nitrified again in the estuary with a ratio of N 2 O-N to NO 3 -N of 0.005, and 3) half of the N LEACH in estuaries is denitrified in the estuary with a N 2 O-N to denitrification (N2 -N) ratio of 0.005. Therefore, N 2 O-N produced from N LEACH in estuaries = N LEACH x (EF 5 -e) where EF 5 -e = 0.0025.
The combined emission factor [EF 5 ] for N 2 O due to N LEACH in: 1) groundwater and surface drainage (EF 5 -g = 0.015 kg N 2 O-N/kg N LEACH ), 2) rivers (EF 5 -r = 0.0075 kg N 2 O-N/kg N LEACH ), and 3) coastal marine areas (EF 5 -e = 0.0025 kg N 2 O-N/kg N LEACH ) is 0.025 (EF 5 ). Therefore:

E QUATION 5 N LEACH = [N FERT + Nex] x Frac LEACH and N 2 O (L) = N LEACH x EF 5

where the default values are Frac LEACH = 0.3 kg N/kg N input to soils and EF 5 = 0.025 kg N 2 O-N/kg N LEACH (see Tables 4-23 and 4-24).
C. Human consumption followed by municipal sewage treatment Nitrous oxide emissions from human waste are described below. However, these N 2 O emissions are allocated to the Waste Chapter (see Section 6.4, Reference Manual and Workbook).
Consumption of foodstuffs by humans results in the production of sewage. Sewage can be disposed of directly on land (night-soil or spray irrigation) or discharged into a water source (e.g., rivers and estuaries). Before disposal on land or into water, it also can be processed in septic systems or wastewater treatment facilities. During all of these stages, nitrous oxide can be produced during nitrification and denitrification of sewage nitrogen.
Sewage nitrogen (N SEWAGE ) production can be estimated from FAO per capita protein consumption data (Protein) and human population counts (Nr PEOPLE ), assuming that nitrogen constitutes about 16 per cent by weight of protein (Frac NPR , Table 4-23).

E QUATION 6 N SEWAGE = Protein x Frac NPR x Nr PEOPLE

Nitrous oxide emissions resulting from sewage nitrogen are estimated following: land disposal or wastewater treatment of sewage, and input of sewage nitrogen to rivers and estuaries.
Disposal or wastewater treatment of sewage No studies were found quantifying nitrous oxide emissions from land disposal of sewage, although supersaturated concentrations of N 2 O in groundwater under cultivated land irrigated with sewage effluent have been reported (Ronen et al., 1988). A few studies have documented N 2 O emission associated with wastewater treatment operations (e.g., Hemond and Duran, 1989; Hanaki et al., 1992; Hong et al., 1993; Debruyn et al., 1994; Czepiel et al., 1995).

## A GRICULTURE

4.110 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Three studies have directly measured N 2 O emissions from operating wastewater treatment facilities (Hemond and Duran, 1989; Czepiel et al., 1995; Velthof and Oenema, 1993). All studies reported low rates of N 2 O emission. For example, nitrous oxide emissions from a secondary treatment wastewater facility in New Hampshire (USA) were approximately 0.0006 kg N 2 O-N/kg sewage N, assuming 3.2 kg sewage nitrogen are produced/person/yr (Czepiel et al., 1995). Velthof and Oenema (1993) found N 2 O losses of 0.022 kg/day per day in a vented closed waste water treatment facility that had a daily input of 900 kg N

, suggesting that N 2 O losses were 0.00005 kg/kg nitrogen entering the system. Additional N 2 O released to the atmosphere following discharge of supersaturated effluent to the environment is also low (0.0007 kg N 2 O-N/kg sewage N) (Hemond and Duran, 1989). Laboratory studies simulating wastewater treatments processes demonstrate that conditions in the treatment facility can affect the amount of N 2 O produced, including the ratio of nitrate to oxidisable carbon and nitrogen loading rate (Nogita et al., 1981; Hanaki et al., 1992). It is difficult to relate these laboratory results to emissions from sewage treatment facilities. For example, in the laboratory study of Nogita et al. (1981), 100 times more N 2 O-N was formed per unit of sewage nitrogen than in the field study of Czepiel et al. (1995).
For the Phase II methodology N 2 O associated with sewage treatment and land disposal is assumed to be negligible. This is based on the low emission rates of N 2 O reported for operating wastewater treatment facilities (Hemond and Duran, 1989; Czepiel et al., 1995; Velthof et al., submitted a;b), and the lack of information on N 2 O production from land disposal of human sewage. This assumption should be reviewed in the future, as new data become available.

Rivers and estuaries N 2 O is produced in rivers and estuaries following nitrification and denitrification of sewage nitrogen inputs (Seitzinger and Kroeze, in preparation). The sewage nitrogen can be discharged directly to aquatic environments (e.g., rivers, estuaries) or enter aquatic environments following leaching from terrestrially disposed sewage. Here it is assumed that minimal removal of sewage nitrogen occurs during land disposal or sewage treatment, and that all sewage nitrogen enters rivers and/or estuaries. This latter assumption should be reviewed in the future, as more data become available.

Nitrous oxide emissions in rivers and estuaries due to nitrification and denitrification of sewage nitrogen are estimated using the same assumptions used for fertiliser nitrogen leached to rivers and estuaries (see B). These assumptions result in emission coefficients of EF 6 –r = 0.0075 kg N 2 O–N/kg N SEWAGE (rivers) and EF 6 –e = 0.0025 kg N 2 O–N/kg N SEWAGE (estuaries). The sum of N 2 O emissions in rivers (0.0075 x N SEWAGE ) and estuaries (0.0025 x N SEWAGE ) associated with nitrification and denitrification of N SEWAGE is calculated as:

E QUATION 7 N 2 O (S) = N SEWAGE x EF 6

where:

EF 6 = 0.1 kg N 2 O–N/kg N SEWAGE (Table 4-23)

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.111 D. Formation of N 2 O in the atmosphere from NH 3 Dentener and Crutzen (1994) proposed that oxidation of NH 3 and subsequent reaction of the intermediate NH 2 radical with NO 2 could lead to a production of 0.9 (+0.9+–0.4) Tg N 2 O (0.6 Tg N/yr).
The most important reactions for N 2 O production are given by:

NH 3 + OH → NH 2 + H 2 O R 1 NH 2 + NO 2 → N 2 O + H 2 O R 2 NH 2 + O 3 → NH 2 O + O 2 (and other products) R 3 The homogeneous reaction of NH 3 with OH radical (R 1 ) is rather slow, and is only of importance in regions with high OH and low sulphate aerosol concentrations. More than 95 per cent of the global amount of NH 3 oxidised by OH occurs between 30 o N and 30 o S. The chemistry of the amine radical NH 2 is not known, reactions R 2 and R 3 having uncertainties of a factor of 2 (DeMore et al.,1994). In addition, emissions and concentrations of NH 3 and NO 2 in tropical regions are poorly quantified.
Dentener and Crutzen (1994) parameterized natural NH 3 emissions from vegetation using a highly uncertain NH 3 canopy compensation point (the atmospheric concentration above which plants assimilate and below which they emit NH 3 ). Without considering this compensation point, N 2 O production was reduced by 55 per cent. Other sources of NH 3 in the tropics include animal waste decomposition (both from wild and domestic animals), fertiliser application and biomass burning emissions. Considering the relative strengths of these sources, about half of the atmospheric N 2 O production may be associated with agricultural nitrogen, amounting to about 0.4 Tg N 2 O/yr. Due to the high uncertainty of this estimate (ca. 100 per cent), we have not included this potentially important source in our agricultural N 2 O emissions inventory. More measurements on the co-occurrence of high NH 3 , NO 2 and OH concentrations in the tropics are needed to provide more insight in the photochemical production of N 2 O. Furthermore laboratory experiments on the reaction rates, especially of reactions R 2 and R 3 , would be extremely valuable.
E. Food processing operations Some food processing operations are sources of N 2 O. A fraction of the edible crop harvest is not consumed by people and enters the waste stream, for instance when it is landfilled, composted, burned or fed to animals. At this point, there are no data to calculate the magnitude of this N 2 O source and therefore, there is no methodology at the present time (For future purposes, this source would be reported under Industrial Processes).

## A GRICULTURE

4.112 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### M ETHODOLOGY FOR 

### E STIMATING 

### I NDIRECT 

### N 2 

### O
Based on the above, we propose the following methodology for calculating a country's indirect N 2 O emissions (kg N/yr):

E QUATION 8 N 2 O indirect = N 2 O (G) + N 2 O (L) + N 2 O (S)

where:

N 2 O (G) = N 2 O produced from atmospheric deposition of NO x and NH 3 (kg N/yr);

N 2 O (L) = N 2 O produced from nitrogen leaching and runoff (kg N/yr);

N 2 O (S) = N 2 O produced from human sewage (kg N/yr) to be reported in the Waste Chapter.

A. Atmospheric deposition of NO x and NH 3 Methodology:

E QUATION 9 N 2 O (G) = (N FERT x Frac GASF + N EX x Frac GASM ) x EF 4

where :

EF 4 = emission factor for atmospheric deposition (kg N 2 O-N/kg NH 3 -N and NO x –N emitted) (see Table 4-23);

Frac GASF = fraction of synthetic fertiliser nitrogen applied to soils that volatilises as NH 3 and NO x (kg NH 3 -N and NO x –N/kg of N input) (see Table 4-19);

Frac GASM = fraction of livestock nitrogen excretion that volatilises as NH 3 and NO x (kg NH 3 -N and NO x –N/kg of N excreted) (see Table 4-19).

Input:

N FERT = fertiliser nitrogen use in country (kg N/yr). Recommended source: FAO data; Nex = livestock nitrogen excretion in country (kg N/yr) (see Table 4-20).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.113 B. Leaching and runoff
Methodology:

N LEACH = (N FERT + N ex ) x Frac LEACH

N 2 O (L) = N LEACH x EF 5

where :

Frac LEACH = fraction of nitrogen input to soils that is lost through leaching and runoff (kg N/kg of nitrogen applied) (see Table 4-24);

EF 5 = emission factor for leaching/runoff (kg N 2 O-N/kg N leaching/runoff) (see Table 4-23);

N LEACH = N leaching in country (kg N/yr).

Input:

N FERT = see A.

Nex = see A.

C. Sewage treatment (see Waste Chapter, Section 6.4)
Methodology:

E QUATION 10 N SEWAGE = PROTEIN x Nr PEOPLE x Frac NPR N 2 O (S) = N SEWAGE x EF 6

where:

EF 6 = emission factor for sewage treatment (kg N 2 O-N/kg sewage-N produced) (see Table 4-23);

Frac NPR = fraction of nitrogen in protein (kg N/kg of protein) (see Table 4- 24);

Input:
PROTEIN = annual per capita protein consumption in country (kg protein/person/yr). Recommended source: FAO;

Nr PEOPLE = number of people in country. Recommended source: FAO.

## A GRICULTURE

4.114 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## Future Work The revised methodology for N 2 O described above is a generalised approach which treats all agricultural systems as being the same under all climates, in all soils, in all crops and in all management systems. This clearly provides uncertainties in inventory calculations. However, the ranges of conversion factors provided should cover the potential N 2 O emissions from each country, whatever climate, soils and set of crops is involved. To make significant improvement in inventory methodologies for N 2 O, the next step is to utilise process-based models to produce country inventories. These would include models of direct emissions from agricultural soils, appropriate animal management models for N 2 O from animal production, simulation models which represent nitrogen transformations in aquatic systems, including riparian areas, wetlands, rivers estuaries, continental shelves and the deep ocean.
Since soil carbon and nitrogen cycles are tightly integrated, both carbon and nitrogen should be considered together so that various aspects of the carbon and nitrogen cycle and CO 2 and N 2 O production can be more accurately defined. For example, the amount of nitrogen leached from agricultural fields represents a very large component of the global N 2 O production according to this revised methodology. The accuracy of the nitrogen leaching fraction prediction is closely tied to carbon turnover in the soil as it controls nitrogen mineralisation and immobilisation. The turnover and retention of nitrogen in all soils is intimately linked with the carbon cycle. Conversely, carbon retention in soils is directly tied to mineral nitrogen availability.
There are additional issues that include: (1) development of methodologies that represent the effect of cropping system, soil, and climate on CO 2 and N 2 O budgets; (2) including soil methane oxidation in national budgets (without the soil sink component, atmospheric methane concentrations would be increasing about two times faster than the increase rate observed in the 1980's); (3) including the impact of NO x emissions from agricultural soils on local and regional atmospheric oxidants and ozone concentration; (4) determining the impact of carbon and nitrogen losses and retention on system sustainability; (5) considering mitigation methodologies to decrease CO 2 and N 2 O emissions from agriculture and to improve the soil sink capacity for CH 4 ; and (6) investigating errors that may arise as a result of aggregating field scale data to the national level.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.115 

## Appendix A Estimates of Nitrous Oxide Emissions from Dung and Urine Deposits of Grazing Animal. This appendix presents a brief summary of estimates of nitrous oxide emissions derived from dung and urine deposits of grazing animals.

T ABLE A-1 E MISSION OF N 2 O FROM ANIMAL DUNG AND URINE DEPOSITED IN GRASSLAND : T HE AMOUNT OF N 2 O EMITTED IS EXPRESSED IN % OF THE AMOUNT OF N EXCRETED BY THE GRAZING ANIMAL . Country Soil Type Treatment Period N 2 O Emission Reference

United Kingdom clay loam urine 4wks 1-5 Monaghan and Barraclough (1993) New Zealand silt loam urine 6 wks <0.5 Sherlock and Goh (1983) Germany loess urine 11 wks 3.8 Flessa et al. (submitted) Germany loess dung 11 wks 0.5 Flessa et al. (submitted) The Netherlands clay urine 4 wks 0.5 Velthof and Oenema (1994) The Netherlands peat urine 3 wks 38 Koops et al. (unpublished) The Netherlands sand urine 2 wks 8-16 De Klein and Logtestijn (1994) United Kingdom clay loam grazing 1 wk 1 8 Velthof et al. (submitted a;b) The Netherlands sand grazing 32 wks 1.0 Velthof and Oenema (1995) The Netherlands clay grazing 32 wks 2.1 Velthof and Oenema (1995) The Netherlands peat grazing 32 wks 1.5 Velthof and Oenema 1995) The Netherlands peat grazing 32 wks 7.7 Velthof and Oenema (1995) Germany - urine/dung 1 yr 0.4-1.3 Poggemann et al. (1995) The Netherlands sand grazing 2 yrs 1.5 Velthof et al. (submitted a;b) The Netherlands clay grazing 2 yrs 3.3 Velthof et al. (submitted a;b) The Netherlands peat grazing 2 yr 2.3 Velthof et al. (submitted a;b) The Netherlands peat grazing 2 yrs 9.8 Velthof et al. (submitted a;b) New Zealand silt loam grazing 1 yr 0.2-1.0 Carran et al. (1995)

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.117 

## Appendix B Data Underlying Nitrous Oxide Emissions from Agricultural Soils This appendix presents the data used to calculate the manure-N excretion and N 2 O emission factors in Table B-1. N 2 O emissions from different Animal Waste Management Systems in different regions of the world are in Table B-2.4AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.119TABLEB-1CALCULATION OFMANURE-N EXCRETION ANDN2O EMISSION FACTORS FORDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS. THESE ARE TO BEREPORTED UNDERMANUREMANAGEMENT,EXCEPT FOR DAILY SPREAD AND PASTURE RANGE OF PADDOCK(EMISSIONS FROM AGRICULTURAL SOILS)AND EMISSIONS AFTER USE AS A FUEL(ENERGY)Region Type of Animal Emission Factor for AWMSs EF3(% of Manure N Excreted that is lost as N2O)Number ofanimals(x106)Nitrogenexcretionkg(N/animal/yr)AnaerobicLagoon(EF3)LiquidSystems(EF3)DailySpread(EF3)SolidStorage &Drylot(EF3)PasturerangePaddock(EF3)UsedFuel(EF3)Other System(EF3)Total NExcreted(Tg N)North America Non-dairy Cattle 99.199 70 0.1 0.1 0.02.02.0 0.0 0.5 6.9Dairy Cattle 16.521 100 0.1 0.1 0.02.02.0 0.0 0.5 1.7Poultry (E) 1486.266 0.6 0.1 0.1 0.02.02.0 0.0 0.5 0.9Sheep 11.336 16 0.1 0.1 0.02.02.0 0.0 0.5 0.2Swine 66.146 20 0.1 0.1 0.02.02.0 0.0 0.5 1.3Other animals (F) 6.067 25 0.1 0.1 0.02.02.0 0.0 0.5 0.2Western Europe Non-dairy Cattle 56.618 70 0.1 0.1 0.02.02.0 0.0 0.5 4.0Dairy Cattle 31.099 100 0.1 0.1 0.02.02.0 0.0 0.5 3.1Poultry (E) 880.000 0.6 0.1 0.1 0.02.02.0 0.0 0.5 0.5Sheep 93.856 20 0.1 0.1 0.02.02.0 0.0 0.5 1.9Swine 114.959 20 0.1 0.1 0.02.02.0 0.0 0.5 2.3Other animals (F) 31.578 25 0.1 0.1 0.02.02.0 0.0 0.5 0.8Eastern Europe Non-dairy Cattle 101.447 50 0.1 0.1 0.02.02.0 0.0 0.5 5.1Dairy Cattle 56.800 70 0.1 0.1 0.02.02.0 0.0 0.5 4.0Poultry (E) 1667.000 0.6 0.1 0.1 0.02.02.0 0.0 0.5 1.0Sheep 188.159 16 0.1 0.1 0.02.02.0 0.0 0.5 3.0Swine 152.757 20 0.1 0.1 0.02.02.0 0.0 0.5 3.1Other animals (F) 21.558 25 0.1 0.1 0.02.02.0 0.0 0.5 0.5AGRICULTURE4.120Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-1 (CONTINUED)CALCULATION OFMANURE-N EXCRETION ANDN2O EMISSION FACTORS FORDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS. THESE ARE TO BEREPORTED UNDERMANUREMANAGEMENT,EXCEPT FOR DAILY SPREAD AND PASTURE RANGE OF PADDOCK(EMISSIONS FROM AGRICULTURAL SOILS)AND EMISSIONS AFTER USE AS A FUEL(ENERGY)Region Type of Animal Emission Factor for AWMSs EF3(% of Manure N Excreted that is lost as N2O)Number ofanimals(x 106)Nitrogenexcretionkg(N/animal/yr)AnaerobicLagoon(EF3)LiquidSystems(EF3)DailySpread(EF3)SolidStorage &Drylot(EF3)PasturerangePaddock(EF3)Used Fuel(EF3)OtherSystem(EF3)Total NExcreted.(Tg N)Oceania Non-dairy Cattle 27.610 60 0.1 0.1 0.02.02.0 0.00.51.7Dairy Cattle 4.441 80 0.1 0.1 0.02.02.0 0.00.50.4Poultry (E) 71.000 0.6 0.1 0.1 0.02.02.0 0.00.50.0Sheep 228.982 20 0.1 0.1 0.02.02.0 0.00.54.6Swine 5.003 16 0.1 0.1 0.02.02.0 0.00.50.1Other animals (F) 2.579 25 0.1 0.1 0.02.02.0 0.00.50.1Latin America Non-dairy Cattle 272.871 40 0.1 0.1 0.02.02.0 0.00.510.9Dairy Cattle 37.560 70 0.1 0.1 0.02.02.0 0.00.52.6Poultry (E) 1259.000 0.6 0.1 0.1 0.02.02.0 0.00.50.8Sheep 117.312 12 0.1 0.1 0.02.02.0 0.00.51.4Swine 78.150 16 0.1 0.1 0.02.02.0 0.00.51.3Other animals (F) 71.699 40 0.1 0.1 0.02.02.0 0.00.52.9Africa Non-dairy Cattle 133.198 40 0.1 0.1 0.02.02.0 0.00.55.3Dairy Cattle 18.734 60 0.1 0.1 0.02.02.0 0.00.51.1Poultry (E) 646.000 0.6 0.1 0.1 0.02.02.0 0.00.50.4Sheep 179.171 12 0.1 0.1 0.02.02.0 0.00.52.2Swine 12.445 16 0.1 0.1 0.02.02.0 0.00.50.2Other animals (F) 162.194 40 0.1 0.1 0.02.02.0 0.00.56.54AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.121TABLEB-1 (CONTINUED)CALCULATION OFMANURE-N EXCRETION ANDN2O EMISSION FACTORS FORDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONS. THESE ARE TO BE REPORTEDUNDERMANUREMANAGEMENT,EXCEPT FOR DAILY SPREAD AND PASTURE RANGE OF PADDOCK(EMISSIONS FROM AGRICULTURAL SOILS)AND EMISSIONS AFTER USE AS A FUEL(ENERGY)Region Type of Animal Emission Factor for AWMSs EF3(% of Manure N Excreted that is lost as N2O)Number ofanimals(x 106)NitrogenexcretionkgN/animal/yrAnaerobicLagoon(EF3)LiquidSystems(EF3)Daily Spread(EF3)Solid Storage& Drylot(EF3)Pasture rangePaddock(EF3)Used Fuel(EF3)OtherSystem(EF3)Total NExcreted(Tg N)Near East andMediterraneanNon-dairy Cattle 44.562 50 0.1 0.1 0.02.02.0 0.0 0.52.2Dairy Cattle 17.174 70 0.1 0.1 0.02.02.0 0.0 0.51.2Poultry (E) 656.000 0.6 0.1 0.1 0.02.02.0 0.0 0.50.4Sheep 187.502 12 0.1 0.1 0.02.02.0 0.0 0.52.3Swine 0.174 16 0.1 0.1 0.02.02.0 0.0 0.50.0Other animals (F) 81.962 40 0.1 0.1 0.02.02.0 0.0 0.53.3Asia and Far East Non-dairy Cattle 440.398 40 0.1 0.1 0.02.02.0 0.0 0.517.6Dairy Cattle 45.240 60 0.1 0.1 0.02.02.0 0.0 0.52.7Poultry (E) 3949.000 0.6 0.1 0.1 0.02.02.0 0.0 0.52.4Sheep 202.442 12 0.1 0.1 0.02.02.0 0.0 0.52.4Swine 403.231 16 0.1 0.1 0.02.02.0 0.0 0.56.5Other animals (F) 293.700 40 0.1 0.1 0.02.02.0 0.0 0.511.7World Total135.3(D) Includes buffalo(E) Includes chickens, turkeys and ducks(F) Includes goats, horses, mules, donkeys and camelsAGRICULTURE4.122Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-2N2O EMISSIONS FROMDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONSRegion Type of AnimalN2O Emission from Waste Management Systems (GgN)LiquidSystemDailySpreadSolid Storageand DrylotPasture Rangeand PaddockUsed Fuel Other System Total AWMSTotal N2OEmission (Gg N)North AmericaNon-dairy Cattle 0 0 19 117 0 0 137137Dairy Cattle 00000199Poultry (E) 00000444Sheep 00030033Swine 00500066Other animals (F) 00030033Western EuropeNon-dairy Cattle 0 0 2 26 0 2 3232Dairy Cattle 0 0 13 5 0 0 2020Poultry (E) 00000233Sheep 0 0 1 33 0 1 3434Swine 0 0 11 0 0 0 1212Other animals (F) 0 0 0 15 0 0 1515Eastern EuropeNon-dairy Cattle 0 0 53 0 0 0 5555Dairy Cattle 0 0 53 10 0 0 6464Poultry (E) 00000444Sheep 0 0 0 44 0 4 4848Swine 0 0 0 16 0 7 2424Other animals (F) 0 0 0 10 0 0 10104AGRICULTURERevised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual4.123TABLEB-2 (CONTINUED)N2O EMISSIONS FROMDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONSRegion Type of AnimalN2O Emission from Waste Management Systems (GgN)LiquidSystemDailySpreadSolid Storageand DrylotPasture Rangeand PaddockUsed FuelOther System Total AWMSTotal N2OEmission(GgN)Oceania Non-dairy Cattle 0 0 0 3300 3333Dairy Cattle 0 0 0 700 77Poultry (E) 0 0 0 000 00Sheep 0 0 0 9200 9292Swine 0 0 0 000 00Other animals (F) 0 0 0 100 11Latin America Non-dairy Cattle 0 0 0 21601 217217Dairy Cattle 0 0 1 1900 1919Poultry (E) 0 0 0 602 88Sheep 0 0 0 2800 2828Swine 0 0 13 003 1515Other animals (F) 0 0 0 5700 5757Africa Non-dairy Cattle 0 0 3 10200 105105Dairy Cattle 0 0 0 1900 1919Poultry (E) 0 0 0 600 77Sheep 0 0 0 4300 4343Swine 0 0 4 000 44Other animals (F) 0 0 0 12800 129129AGRICULTURE4.124Revised 1996IPCC Guidelines for National Greenhouse Gas Inventories: Reference ManualTABLEB-2 (CONTINUED)N2O EMISSIONS FROMDIFFERENTANIMALWASTEMANAGEMENTSYSTEMS INDIFFERENTWORLDREGIONSRegion Type of Animal N2O Emission from Waste Management Systems (Gg N)AnaerobicLagoonLiquidSystemDailySpreadSolid Storageand DrylotPasture Rangeand PaddockUsed Fuel OtherSystemTotal AWMSTotal N2OEmission (Gg N)Near East andMediterraneanNon-dairy Cattle 0 0 0 0 34 0 03535Dairy Cattle 0 0 0 1 19 0 01919Poultry (E) 0 0 0 0 6 0 166Sheep 0 0 0 0 45 0 04545Swine 0 0 0 0 0 0 000Other animals (F) 0 0 0 0 66 0 06666Asia and FarEastNon-dairy Cattle 0 0 0 49 102 0 0151151Dairy Cattle 0 0 0 0 13 0 01313Poultry (E) 0 0 0 0 21 0 62727Sheep 0 0 0 0 40 0 24242Swine 0 0 0 68 0 0 07171Other animals (F) 0 0 0 0 223 0 3226226World Total1609 1971(D) Includes buffalo(E) Includes chickens, turkeys and ducks(F) Includes goats, horses, mules, donkeys and camels

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.125 

## 4.6 References

Methane and Nitrous oxide Emissions from Domestic Livestock Enteric Fermentation and Manure Management AAC (Australian Agricultural Council) (1990), Feed Standards for Australian Livestock. Ruminants , Commonwealth Scientific and Industrial Research Organisation (CSIRO) Publications, East Melbourne, Victoria, Australia. ARC (1980), The Nutrient Requirements of Ruminant Livestock , Commonwealth Agricultural Bureau, the Lavenham Press Ltd., UK. Bamualim, A. and Kartiarso (1985), "Nutrition of draught animals with special reference to Indonesia." In: Draught Animal Power for Production J.W. Copland (ed.), Australian Centre for International Agricultural Research (ACIAR), Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia. Bhattacharya, S.C., H.L. Pham, R.M. Shrestha and Q.V. Vu, (1993) “CO 2 emission due to fossil/traditional fuels, residues and wastes in Asia.” AIT (Asian Institute of Technology) Workshop on Global Warming Issues in Asia. Bangkok, Thailand. Blaxter, K.L. and J.L. Clapperton (1965), "Prediction of the amount of methane produced by ruminants," British Journal of Nutrition 19:511-522. Crutzen, P.J., I. Aselmann and W. Seiler (1986), "Methane Production by Domestic Animals, Wild Ruminants, Other Herbivorous Fauna, and Humans," Tellus 38B:271-284 FAO (1990), Yearbook - Production Vol. 44 , FAO, United Nations, Rome, Italy. Gibbs, M.J. and D.E. Johnson (1993), "Livestock Emissions." In: International Methane Emissions , US Environmental Protection Agency, Climate Change Division, Washington, D.C., U.S.A. Graham, N.M. (1985), "Relevance of the British metabolisable energy system to the feeding of draught animals." In: Draught Animal Power for Production , J.W. Copland (ed.), ACIAR (Australian Centre for International Agricultural Research) Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia. Hashimoto, A. and J. Steed (1993), Methane Emissions from Typical U.S. Livestock Manure Management Systems. Draft report prepared for ICF Incorporated under contract to the Global Change Division of the Office of Air and Radiation, US Environmental Protection Agency, Washington, D.C., U.S.A. IAEA (1992), Manual on measurement of methane and nitrous oxide emissions from agriculture . International Atomic Energy Agency Publication IAEA-TECDOC-674, Vienna, Austria. Ibrahim, M.N.M. (1985), "Nutritional status of draught animals in Sri Lanka." In: Draught Animal Power for Production , J.W. Copland (ed.), ACIAR (Australian Centre for International Agricultural Research) Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia. Johnson, K.A., H. Westberg, M. Hyler and B. Lamb (1993), Cattle Methane Measurement Techniques Workshop , August 9-12, 1993, Washington State University, Pullman, WA, sponsored by the Global Change Division, Office of Air and Radiation, US Environmental Protection Agency, Washington, D.C., U.S.A.

## A GRICULTURE

4.126 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Jossy, M. T. (1994), Estimation of Greenhouse Gases Emission from Agricultural Wastes in Asia, M.Eng Thesis, Asian Institute of Technology, Bangkok, Thailand (to be submitted). Jurgens, M.H. (1988), Animal Feeding and Nutrition , Sixth Edition, Kendall/Hunt Publishing Company, Dubuque, Iowa, U.S.A. Lawrence, P.R. (1985), "A review of nutrient requirements of draught oxen." In: Draught Animal Power for Production , J.W. Copland (ed.), ACIAR (Australian Centre for International Agricultural Research) Proceedings Series No. 10. ACIAR, Canberra, A.C.T., Australia. Lichtman, R. J. (1983), Biogas Systems in India , Volunteers In Technical Assistance (VITA), Arlington, Virginia, U.S.A. NRC (1984), Nutrient Requirements of Beef Cattle , National Academy Press, Washington, D.C., U.S.A. NRC (1989), Nutrient Requirements of Dairy Cattle , National Academy Press, Washington, D.C., U.S.A. OECD (1991), Estimation of Greenhouse Gas Emissions and Sinks: Final Report from the OECD Experts Meeting, 18-21 February 1991 , OECD, Paris, France. Robbins, C.T. and D.L. Robbins (1979), "Foetal and neonatal growth patterns and maternal reproductive effort in ungulates and sub-ungulates," Amer. Naturalist 114:101. Safley, L.M. Jr. and P.W. Westerman, (1992), "Performance of a low temperature lagoon digester," Bioresource Technology 41:167-175. Safley, L.M., M.E. Casada, J.W. Woodbury, and K.F. Roos (1992), Global Methane Emissions from Livestock and Poultry Manure. US Environmental Protection Agency, Global Change Division, Washington, D.C., February 1992, EPA/400/1091/048. Stuckey, D.C. (1984), "Biogas: a global perspective." In: Biogas Technology, Transfer and Diffusion , M.M. El-Halwagi (ed.), Elsevier, New York, U.S.A., pp. 18-44. US EPA (1993), Anthropogenic Methane Emissions in the United States , Global Change Division, Office of Air and Radiation, Washington, D.C. Winrock (1978), The Role of Ruminants in Support of Man , Winrock International, Morrilton, Arkansas, U.S.A. Woodbury, J.W. and A. Hashimoto (1993), "Methane Emissions from Livestock Manure." In International Methane Emissions , US Environmental Protection Agency, Climate Change Division, Washington, D.C., U.S.A. Yancun, C., H. Cong and Liang Pusen (1985), "Development of a new energy village - Xinbu, China." In: Integrated Rural Energy Planning , Y. El Mahgary and A.K. Biswas (eds.), Butterworths Publishing, Guildford, England, pp. 99-108.

Methane Emissions from Flooded Rice Fields Aselmann, I. and P.J. Crutzen (1989), “The global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emission.” J. Atm. Chem . 8, 307-358. Blake, D.R. and F.S. Rowland (1988), “Continuing world-wide increase in tropospheric methane, 1978 to 1987”. Science 239, 1129-1131.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.127 Bouwman, A.F. (1990), “Exchange of GHGs between terrestrial ecosystems and the atmosphere.” Ed. A.F. Bouwman, in Soil and the Greenhouse Effect, John Wiley and Sons, U.K., pp. 62-127. Chen, Z., D. Li, K. Shao and B. Wang (1993), “Features of CH 4 emission from rice paddy fields in Beijing and Nanjing.” Chemosphere 26, 239-245 Cai, Z.C., H. Zu, H.H. Zhang and J.S. Jin (1994), “Estimate of methane emission from rice paddy fields in Taihu region, China.” Pedosphere 4, 297-306 China Agricultural Yearbook (1990), Agribookstore, Hampton, VA, U.S.A. Cicerone, R.J., and J.D. Shetter (1981), “Sources of atmospheric methane; measurements in rice paddies and a discussion.” J Geophys Res 86: 7203-7209. Cicerone, R.J., J.D. Shetter and C.C. Delwiche (1983), “Seasonal variation of methane flux from a California rice paddy.” J. Geophys. Res . 88, 7203-7209. Cicerone, R.J. and R.S. Oremland (1988). “Biogeochemical aspects of atmospheric methane.” Global Biogeochem. Cycles 2, 299-327. Cicerone, R.J., C.C. Delwiche, S C. Tyler and P.R. Zimmerman (1992, “Methane emissions from California rice paddies with varied treatments

. ” Global Biogeochem. Cycles 6 233-248. Conrad, R. (1989), “Control of methane production in terrestrial ecosystems”. In: Exchange of Trace Gases between Terrestrial Ecosystems and the Atmosphere , M.O. Andreae and D.S. Schimel(eds.), 39-58. Conrad, R. (1993), “Mechanisms controlling methane emission from wetland rice fields”. In: The Biogeochemistry of Global Change: Radiative Trace Gases , R.S. Oremland, (ed.) Chapman & Hall, New York, pp. 317-335. Crutzen, P.J. (1985), “The role of the tropics in atmospheric chemistry.” In: R Dickinson (ed.) The Geophysiology of Amazonia , Wiley, Chichester, pp. 107-132. DeDatta, S.K. (1975), “Upland rice around the world.” In: Major Research in Upland Rice, International Rice Research Institute, Los Baños, Philippines. Denier van der Gon, H.A.C. and H.U. Neue (1994), “Impact of gypsum application on methane emission from a wetland rice field.” Global Biogeoche m, Cycles, 8, 127-134 Ehhalt, D.H. and U. Schmidt (1978), “Sources and sinks of atmospheric methane.” Pure Appl. Geophys ., 116, 452-464. Grist, D.H. (1986), Rice . Longman, Inc., New York, U.S.A., 6th edition. Holzapfel-Pschorn, A., and W. Seiler (1986), “Methane emission during a cultivation period from an Italian rice paddy.” J. Geophys. Res ., 91, 11803-11814.. Husin, Y. A., D. Murdiyarso, M. A. K. Khalil, R. A. Rasmussen, M. J. Shearer, S. Sabiham, A. Sunar, A. Adijuwana, ( 1995 ), “Methane flux from Indonesian wetland rice : The effect of water management and rice variety”, Chemosphere , 31(4), pp 3153-3180. Huke, R.F. (1982), Rice Area by Type of Culture; South, South-east and East Asia

. International Rice Research Inst., IRRI, Los Banos, Laguna, Philippines. IPCC (1990), Climate Change, the IPCC Scientific Assessment , J.T. Houghton, G J Jenkins and J J Ephraums, (eds.) Cambridge University Press, UK, pp. 1-40.

## A GRICULTURE

4.128 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual IPCC (1996), Climate Change 1995: the Science of Climate Change, WGI contribution to the IPCC Second Assessment Report , J.T. Houghton, L G Meira Filho, B A Callander, N Harris, A Kattenberg and K Maskell. (eds.) Cambridge University Press, 1996. Jermsawatdipong, P., J. Murase, P. Prabuddham, Y. Hasathon, N. Khomthong, K. Naklang, A. Watanabe, H. Haraguchi and M. Kimura (1994), “Methane emission from plots with differences in fertilizer application in Thai paddy fields.” Soil Sci. Plant Nutr., 40, 63-71. IGAC (1994), Global Measurement Standardisation of Methane Emissions from Irrigated Rice Cultivation, A Report of the Rice Cultivation and Trace Gas Exchange Activity (RICE) of the International Global Atmospheric Chemistry (IGAC) Project (Convenors, R. Sass and H.U. Neue), IGAC Core Office, Cambridge, MA. IRRI (1990), World Rice Statistics, 1989, International Rice Research Institute, Los Banos, Philippines. IRRI (1993), 1993-1995 IRRI Rice Almanac, International Rice Research Institute, Manila, Philippines. IRRI (1994), IRRI Rice Almanac, International Rice Research Institute, Manila, Philippines. Katoh, K., P. Chairoj, W. Choltikul, H. Tsuruta and K. Yagi (1995). Mechanism of methane formation and development of methods to decrease methane emission in humid tropical paddy fields. Japan International Research Center for Agricultural Sciences. Khalil, M.A.K. and R.A. Rasmussen (1983), “Sources, sinks, and seasonal cycles of atmospheric methane.” J Geophys Res 88: 5131-5144. Khalil, M.A.K., R.A. Rasmussen, M.X. Wang and L. Ren (1991), “Methane emission from rice fields in China.” Environ. Sci. Tech., 25:979-981. Koyama, T. (1964), “Biogeochemical studies on lake sediments and paddy soils and the production of atmospheric methane and hydrogen.” In: Recent Researches in the Fields of Hydrosphere, Atmosphere and Nuclear Geochemistry, Y. Miyake and T. Koyama, (eds.), Muruzen, Tokyo, Japan, pp. 143-177. Kush, G. S., (1984), Terminology for rice growing environments , International Rice Research Institute, P.O Box 933, Manila, Philippines, pp 5-10. Lindau, C.W., P.K. Bollich, R.D. DeLaune, W.H. Patrick Jr., and V.J. Law (1991), “Effect of urea fertilizer and environmental factors on CH 4 emissions from a Louisiana, USA rice field.” Plant Soil, 136, 195-203 Lindau, C.W. and P.K. Bollich (1993), “Methane emissions from Louisiana first and ratoon rice crop.” Soil Science , 156:42-48. Lindau, C.W. (1994), “Methane emissions from Louisiana rice fields amended with nitrogen with fertilizers.” Soil Biol. Biochem., 26, 353-359 Minami, K. (1994), “Methane from rice production.” Fert. Res. 37 , pp. 169-179. Minami, K., (1995 ), “The effect of nitrogen fertilizer use and other practices on methane emission from flooded rice.” Fert. Res ., 40, pp. 71-84. Mitra, A.P. (1992), Greenhouse gas emission in India, 1991 methane campaign Council of Scientific and Industrial Research, and Ministry of Environment and Forest. Scientific Report No. 20. NPL, India. Mitra A. P. (1996);(ed.) Greenhouse gas inventory for India : 1995 Update , Global Change Series, 1996 (in press).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.129 Neue, H. U., (1989), Rice growing soils: constraints, utilization and research needs , FFTC Book Series No. 39, Food and Fertilizer Technology Center for the Asia Pacific Region, Taipei, Taiwan. Neue, H.U., P. Becker-Heidmann and H.W. Scharpenseel (1990), “Organic matter dynamics, soil properties and cultural practices in rice lands and their relationship to methane production.” In: Soils and the Greenhouse Effect A.F. Bouwman (ed.), John Wiley and Sons, UK, pp. 457-466. Neue, H.U. and R. Sass (1994), “Trace gas emissions from rice fields.” In: Global Atmospheric-Biospheric Chemistry , R.G. Prinn (ed.) Plenum Press, New York. Neue, H. U., R. S. Lantin, R. Wassmann, J. B. Aduna, M. C. R. Alberto, and M. J. F. Andales (1994), “Methane emission from rice soils of the Philippines.” In: CH 4 and N 2 O Global Emissions and Controls from Rice Fields and Other Agricultural and Industrial Sources, K. Minami, A. Mosier and R. L. Sass (eds.), NIAES, Series 2, Yokendo Publ., Tokyo, Japan, pp. 55-64. NGGIC (1996), Australian Methodology for the Estimation of Greenhouse Gas Emissions and Sinks, Agriculture, Workbook for Non-Carbon Dioxide Gases from the Biosphere, Workbook 5.1, National Greenhouse Gas Inventory Committee 1996, Canberra, Australia. Nugroho, S.G., J. Lumbanraja, H. Suprapto, Sunyoto, W.S. Ardjasa, H. Haraguchi and M. Kimura (1994a), “Methane emission from an Indonesian paddy field subjected to several fertilizer treatments.” Soil Sci. Plant Nutr., 40, 275-281 Nugroho, S.G., J. Lumbanraja, H. Suprapto, Sunyoto, W.S. Ardjasa, H. Haraguchi and M. Kimura (1994b), “Effect of intermittent irrigation on methane emission from an Indonesian paddy field” Soil Sci. Plant Nutr. 40, 609-615. Parashar, D. C. et al., (1994), “Methane budget from paddy fields in India .” Current Science 66, Report No. 12, pp 938-940. Parashar, D. C, Gupta K. Prabhat and S. Bhataachaya (1996), “Methane emissions from paddy fields in India-An update,” J. Radio and Space Physics (in press). Patrick, W.H. Jr. (1981), “The role of inorganic redox systems in controlling reduction in paddy soils”. In: Proc. Symp. Paddy Soil, 107-117, Science Press, Beijing, China, Springer-Verlag. Sass, R.L., F.M. Fisher, P.A. Harcombe and F.T. Turner (1990), “Methane production and emission in a Texas rice field.” Global Biogeochemical Cycles 4:47-68. Sass, R.L., F.M. Fisher, P.A. Harcombe and F.T. Turner (1991a), “Mitigation of methane emissions from rice fields: Possible adverse effects of incorporated rice straw.” Global Biogeochemical Cycles 5: 275-287. Sass, R.L., F.M. Fisher, F.T. Turner and M.F. Jund (1991b), “Methane emission from rice fields as influenced by solar radiation, temperature and straw incorporation”. Global Biogeochemical Cycles 5: 335-350. Sass, R.L., F.M. Fisher, Y.B. Yang, F.T. Turner and M.F. Jund (1992), “Methane emissions from rice fields: the effect of flood water management”. Global Biogeochemical Cycles 6(3): 249-262. Sass, R L (1994), Short summary chapter for methane. In: CH 4 and N 2 O: global emissions and controls from rice field and other agricultural and industrial sources, K. Minami, A. Mosier and R. L. Sass (eds.) NIAES, Series 2, Yokendo Publishers, Tokyo, pp 1-7.

## A GRICULTURE

4.130 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Sass, R.L. and F.M. Fisher (1995), “Methane emissions from Texas rice fields: a five-year study.” In: Climate Change and Rice . S. Peng, K.T. Ingram, H.U. Neue, L.H. Ziska (eds.) Springer, Berlin, pp.46-59. Schütz, H., A. Holzapfel-Pschorn, R. Conrad, H. Rennenberg and W. Seiler (1989a), “A 3- year continuous record on the influence of daytime, season and fertilizer treatment on methane emission rates from an Italian rice paddy .” J. Geophys. Res

. 94, 16,405-16,416. Schütz H., W. Seiler, and R. Conrad (1989b), “Processes involved in formation and emission of methane from rice paddies.” Biogeochem 7: 33-53 Schütz, H., W. Seiler, and H. Rennenberg (1990), “Soil and land use related sources and sinks of methane in the context of the global methane budget.” In: Soils and the Greenhouse Effect, A.F. Bouwman (ed), Wiley, Chichester, pp. 269-285. Seiler, W., A. Holzapfel-Pschorn, R. Conrad and D. Scharffe (1984), “Methane emissions from rice paddies”. J. Atmos. Chem . 1, 241-268. Shao, (1993), Agro-Ecological Environment, Supplement Issue, 19-22 (in Chinese) Shin, Y-K, S-H. Yun, M-E. Park (1995), “Estimation of methane emission by water management and rice straw application in paddy soil in Korea.” J. Korean Soc. of Soil Sci. and Fert . 28 (3), 261-265. Takai, Y. (1970), “The mechanism of methane fermentation in flooded paddy soil.” Soil Sci. Plant Nutr. 16, 238-244. United Nations (1992), FAO Production Yearbook, vol. 46 . Food and Agriculture Organization of the United Nations, Rome, Italy. Wang, M.X., A. Dai, R. Shen, H. Schütz, W. Seiler, H. Rennenberg and H. Wu (1990), “CH 4 emissions from a Chinese rice paddy field.” Acta Meteoroloogica Sinica. Scienta Atmospherica Sinica 4, 265-274. Wassman, R., H. Schütz, H. Papen, H. Rennenberg, W. Seiler, A. Dai, R. Shen, X. Shangguan and M. Wang (1993a), Quantification of methane emissions from Chinese rice fields (Zhejiang Province) as influenced by fertiliser treatment.” Biogeochemistry 20:83-101. Wassman, R., M.X. Wang, X.J. Shangguan, X.L. Xie, R. X. Shen, Y.S. Wang, H. Papen, H. Rennenberg and W. Seiler (1993b), First records of a field experiment on fertilizer effects on methane emission from rice fields in Hunan Province (PR China) Geophys. Res. Letters 20, 2071-2074. Wassmann, R., H.U. Neue, R.S. Lantin, J.B. Aduna, M.C.R. Alberto, M.J. Andales, M.J. Tan, H.A.C. Denier van der Gon, H. Hoffmann, H. Papen, H. Rennenberg and W. Seiler (1994), “Temporal patterns of methane emissions from wetland rice fields treated by different modes of N application.” J. Geophys. Res. 99 , 16457-16462 Yagi, K. and K. Minami (1990a), Effect of organic matter applications on methane emissions from Japanese paddy fields. Soil Sci. Plant Nutr . 36, 599-610. Yagi, K. and K. Minami (1990b), Estimation of global methane emission from paddy fields. Res. Rep. Div. Environ. Planning, NIAES , 6, 131-142 (in Japanese).

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.131 Yagi, K.H. Tsuruta, K. Minami, P. Chairoj and W. Cholitkul (1994a), “Methane emissions from Japanese and Thai paddy fields.” In: CH 4 and N 2 O Global Emissions and Controls from Rice Fields and Other Agricultural and Industrial Sources , K. Minami, A. Mosier and R.L. Sass (eds.), NIAES , Series 2, Yokendo Publ., Tokyo, Japan, pp 41 -53. Yagi K, P.Chairoj, H. Tsuruta, W. Cholitkul, and K. Minami (1994b), “Methane emission from rice paddy fields in the central plain of Thailand.” Soil Sci. Plant Nutr. 40: 29- 37. Yagi, K., H. Tsuruta and K. Minami (1996), “Effect of water management on methane emissions from a Japanese rice paddy field: Automated methane monitoring.” Global Biogeochem. Cycles 10, 255-267. Yamane, I. and K. Sato (1961), “Effect of temperature on the formation of gases and ammonium nitrogen in the water-logged soils.” Sci. Rep. Res. Inst. Tohoku Univ

. D (Agr.) 12, 31-46. Yamane, I. and K. Sato (1964), “Decomposition of glucose and gas formation in flooded soil.” Soil Sci. Plant Nutr 10, 127-133. Yao, H., and Z. L. Chen (1994a), “Effects of chemical fertilizer on methane emission from rice paddies.” J. Geophys. Res. 99, 16463-16470 Yao, H., and Z. L. Chen (1994b), “Seasonal variation of methane flux from a Chinese rice paddy in a semi-arid, temperate region.” J. Geophys. Res. 99, 16471-16477
Agricultural Burning Andreae, M.O. (1990), “Biomass burning in the tropics: Impact on environmental quality and global climate.” Paper presented at the Chapman Conference on Global Biomass Burning: Atmospheric, Climatic, and Biospheric Implications , 19-23 March 1990, Williamsburg, Virginia, U.S.A. Barnard, G.W. (1990), Use of agricultural residues as fuel. In: Bioenergy and the Environment . J. Pasztor and L.A. Kristoferson (eds.), Westview Press, Boulder, Colorado, U.S.A, pp. 85-112. Barnard, G.W. and L.A. Kristoferson (1985), Agricultural Residues as Fuel in the Third World . Technical Report No. 5. Earthscan, London, UK. Bolin, B., E.T. Degens, P. Duvigneaud and S. Kempe (1979), The global biogeochemical carbon cycle. In: the Global Carbon Cycle, . B. Bolin, E.T. Degens, P. Duvigneaud, and S. Kempe (eds.). SCOPE 13, Wiley, Chichester, UK. pp. 1-56. Bouliere, F. and M. Hadley (1970), The ecology of tropical savannas. Annual Review of Ecology Systems 1:125-152. Bucher, E.H. (1982), Chaco and Caatinga-South American arid savannas, woodlands and thickets. In: Ecology of Tropical Savannas B.J. Huntley, and B.H. Walker, (eds.) (Ecological Studies 42). Springer-Verlag, Berlin, Germany, pp. 48-79. Coutinho, L.M. (1982), Ecological effects of fire in Brazilian cerrado. In: Ecology of Tropical Savannas . B.J. Huntley, and B.H. Walker (eds.)(Ecological Studies 42). SpringerVerlag, Berlin, Germany, pp. 273-291. Crutzen, P.J. and M.O. Andreae (1990), “Biomass burning in the Tropics: Impact on atmospheric chemistry and biogeochemical cycles.” Science 250:1669-1678.

## A GRICULTURE

4.132 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Crutzen, P.J. (1983), “Atmospheric interactions – Homogenous gas reactions of C, N, and S containing compounds.” In The Major Biogeochemical Cycles and Their Interactions, B. Bolin, and R.B. Cook (eds.),. SCOPE 21, John Wiley and Sons Inc., New York, U.S.A, pp. 67-114. Delmas, R. (1993), “An Overview of Present Knowledge on Methane Emission from Biomass Burning.” In: Proceedings of an International IPCC Workshop: Methane and 

### Nitrous Oxides, Methods in National Emissions Inventories and Options for Control, 3-

5 February 1993, Amersfoort, NL. A.R, van Amstel (ed.). RIVM Report No. 481507003, Bilthoven, The Netherlands, July. Delmas, R.A. and D. Ahuja (1993), “Estimating national methane emissions from anthropogenic biomass burning. Working group report: Methane emissions from biomass burning. In Proceedings of an International IPCC Workshop: Methane and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control, 3- 5 February 1993, Amersfoort, NL., A.R. van Amstel (ed.), RIVM Report No. 481507003, Bilthoven, The Netherlands, July. Elgin, J. (1991), National Programme Leader for Forages and Pastures, US Department of Agriculture, personal communication. FAO/UNEP (1981), Tropical Forest Resources Assessment Project . FAO (Food and Agriculture Organization of the United Nations/United Nations Environment Programme), Rome, Italy. FAO (1991), Production Yearbook Volume 44. FAO Statistics Series 94, FAO (Food and Agriculture Organization of the United Nations), Rome, Italy. FAO (1993), Forest Resources Assessment 1990 - Tropical Countries. FAO Forestry Paper No. 112, FAO, Rome, Italy. Galbally, I.E. (1985), The emission of nitrogen to the remote atmosphere : Background paper. In: The Biogeochemical Cycling of Sulfur and Nitrogen in the Remote Atmosphere, J.N. Galloway, R.J. Charlson, M.O. Andreae, and H. Rodhe (eds.). D. Reidel, Dordrecht, The Netherlands, pp. 27-53. González-Jiménez, E. (1979), “Primary and secondary productivity in flooded savannas.” In UNESCO/UNEP/FAO (ed.). “Tropical grazing land ecosystems of Venezuela.” Nat. Resour. Res. 16:620-625. Haggar, R.J. (1970), “Seasonal production of Andropogon gayanus , 1. Seasonal changes in field components and chemical composition.” Journal of Agricultural Science, 74:487-494. Hall, D., F. Rosillot-Calle, R.H. William and J Wood (1994), Network Newsletter , Biomass users Network/UNCED. King’s College, London, Campden Hill Road, London W8 7AH, UK. Hao, W.M., M.H. Liu and P.J. Crutzen (1990), “Estimates of annual and regional releases of CO 2 and other trace gases to the atmosphere from fires in the tropics, based on the FAO statistics for the period 1975-1980.” In: Fire in the Tropical Biota, Ecosystem Processes and Global Challenges, J.G. Goldammer, (ed.). Springer-Verlag, Berlin, Germany, pp. 440-462. Harris, D.R. (1980), “Tropical savanna environments: Definition, distribution, diversity, and development.” In: Human ecology in savanna environments, Harris, D.R. (ed.). Academic Press, New York, US, pp. 3-27.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.133 Hopkins, B. (1965), “Observations on savanna burning in the Olokemeji Forest Reserve, Nigeria.” Journal of Applied Ecology 2:367-381. Howden, S.M., G.M. McKeon, J.C. Scanlan, J.O. Carter and D.H. White (1996), “Methods for exploring options to reduce greenhouse gas emissions from tropical grazing systems.” Climatic Change . (In press.) Huntley, B.J. (1982), “South African savannas.” In: Ecology of Tropical Savannas, B.J. Huntley and B.H. Walker (eds.),.(Ecological Studies 42). Springer-Verlag, Berlin, Germany, pp. 101-119. Huntley, B.J. and J.W. Morris (1982), “Structure of Nylsvley savanna.” In: Ecology of Tropical Savannas, B.J. Huntley and B.H. Walker (eds.), (Ecological Studies 42). Springer-Verlag, Berlin, Germany, pp. 433-455. Johansson, T.B., H. Kelly, A.K.N. Reddy and R.H. Williams (1992), Renewable Energy: Sources for Fuels and Electricity . Island Press, Washington, DC, U.SA. Lacaux, J.P., H. Cachier and R. Delmas (1993), “Biomass Burning in Africa: An Overview of Its Impact on Atmospheric Chemistry.” In: Fire in the Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires P.J. Crutzen and J.G. Goldammer (eds.). J. Wiley & Sons Ltd, UK. Lacey, C.J., J. Walker and I.R. Nolde (1982), Fire in Australian tropical savannas. In : Ecology of Tropical Savannas, B.J. Huntley, and B.H. Walker (eds.).. (Ecological Studies 42). Springer-Verlag, Berlin, U.S,A. pp. 246-272. Lanly, J.P. (1982), Tropical Forest Resources . Food and Agriculture Organization of the United Nations (FAO) Paper 30, FAO, Rome, Italy. Lashof, D.A. and D.A. Tirpak (eds.) (1990), Policy Options for Stabilizing Global Climate

. Report to Congress, US Environmental Protection Agency, Washington, D.C., U.S.A. Levine, J.S. (ed.) (1990), Global Biomass Burning: Atmospheric, Climatic and Biospheric Implications . The MIT Press, Cambridge, MA, U.S.A. Lieth, H. (1978), Patterns of Primary Productivity in the Biosphere . Hutchinson Ross, Stroudsberg, PA, U.S.A.. Lobert, J.M., D.H. Scharffe, W.M. Hao and P.J. Crutzen (1990), “Importance of biomass burning in the atmospheric budgets of nitrogen-containing gases.” Nature 346:552-554. Menaut, J.C., L. Abbadie, F. Lavenu, Ph. Loudjani and A. Podaire (1991), “Biomass burning in West African savannas.” In: Global Biomass Burning , J. Levine (ed.), MIT Press, Cambridge, MA, U.S.A. Menaut, J.C., and J. César (1982), “The structure and dynamics of a West African savanna.” In: Ecology of Tropical Savannas, B.J. Huntley and B.H. Walker (eds.).(Ecological Studies 42). Springer-Verlag, Berlin, Germany, pp. 8-100. Menaut, J.C. (1990), Biomass burning in West African savannas . Presentation given at the Chapman Conference on Global Biomass Burning. Williamsburg, Virginia, March 19-23. Proceedings forthcoming : MIT Press, Cambridge, MA, U.S.A. Ponnamperuma, F.N. (1984), “Straw as a source of nutrients for wetland rice.” In: Organic Matter and Rice . International Rice Research Institute, Los Baños, Philippines. pp. 117-135.

## A GRICULTURE

4.134 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual San José, J.J. and E. Medina (1976), “Organic matter production in the Trachypogon savannas in Venezuela.” Tropical Ecology 17:113-124. Seiler, W. and P.J. Crutzen (1980), “Estimates of gross and net fluxes of carbon between the biosphere and the atmosphere from biomass burning.” Climatic Change 2:207-247. Singh, K.P. and R. Misra (1978), Structure and Functioning of Natural, Modified and Silvicultural Ecosystems of Eastern Uttar Pradesh . Technical Report MAB Research Project, Banaras Hindu University, Varanasi. Strehler, A. and W. Stützle (1987), “Biomass residues.” In: Biomass: Regenerable Energy, D.O. Hall, and R.P. Overend (eds.). John Wiley, Chichester, U.K., pp. 75-102. US HEW (1970), Air Quality Criteria for Carbon Monoxide . US HEW, Washington, D.C., U.S.A. Whittaker, R.H. and G.E. Likens (1975), “The biosphere and man.” In: (1975), Primary Productivity of the Biosphere, H. Lieth and R.H. Whittaker (eds.). Ecological Studies No. 14. Springer-Verlag, New York-Heidelberg-Berlin.
Nitrous Oxide Emissions from Agricultural Soils Bakken, L., K. Refsgaard, S. Christensen and A. Vatn (1994), “Energy use and emissions of greenhouse gases from grassland agricultural systems.” In: Grassland and Society, L. 't Mannetje and J. Frame (eds.), Wageningen Pers, Wageningen, The Netherlands, pp. 361-376. Barrow, N.J. and L.J. Lambourne (1962), Australian Journal of Agricultural Research 13:461- 471. Berounsky, V.M. and S.W. Nixon (1985), “Eutrophication and the rate of net nitrification in a coastal marine ecosystem.” Estuarine Coastal and Shelf Science 20:773-781. Berounsky, V.M. and S.W. Nixon (1993), “Rates of nitrification along an estuarine gradient in Narragansett Bay.” Estuaries 16(4):718-730. Bouwman, A.F. (1994), Method to estimate direct nitrous oxide emissions from agricultural soils . Report 773004004. National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands, p. 28. Bouwman, A.F. (1995), “Compilation of a global inventory of emissions of nitrous oxide.” Thesis Landbouwuniversiteti Wageningen. ISBN 90-5485-364-6, p. 143. Bouwman, A.F. (1996), Long-term scenarios of livestock-crop-land use interactions for the assessment of environmental indicators in developing countries. FAO Report. (In press). Bouwman, A.F., and W.G. Sombroek (1990), “Inputs to climatic change by soils and agriculture related activities: Present status and possible future trends.” In: Soils on a warmer Earth , H.W. Scharpenseel, M. Schomaker & A. Ayoub (eds.). Developments in Soil Science 20

. Elsevier, Amsterdam, pp. 15-30. Bouwman, A.F. and K.W. Van Der Hoek (1991), Analysis of soil and water borne emissions of nitrous oxide and methane in the Netherlands . RIVM Report No. 736301010. National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands. Bouwman, A.F., K.W. van der Hoek and J.G.J. Olivier (1995), “Uncertainties in the global source distribution of nitrous oxide.” J. Geophys. Res ., 100:2785-2800.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.135 Bowden, R.D., J.M. Melillo and P.A. Steudler (1991), “Effects of nitrogen additions on annual nitrous oxide fluxes from temperate forests soils in the northeastern United States.” J. Geophys. Res . 96:9321-9328. Brumme, R. and F. Beese (1992), “Effects of liming and nitrogen fertilization on emission of CO 2 and N 2 O from a temperate forest” J. Geophys. Res. 97:12851-12858. Burton, C.H., R.W. Sneath and J.W. Farrent (1993), “Emissions of nitrogen oxide gases during aerobic treatment of animal slurries.” Bioresource Technology 5:233-235. Carran, R.A., Theobald, P.W. and Evans, J.P. (1995), “Emission of nitrous oxide from some grazed pasture soils in New Zealand.” Australian Journal of Soil Research 33:341-352. Christensen, P.B. and J. Soerensen (1988), “Denitrification in sediment of lowland streams: regional and seasonal variation in Gelbaek and Rabis Beak, Denmark.” FEMS Microbiol. Ecol. 53:335-344. Christensen, P.B., L.P. Nielsen, N.P. Revsbech and J. Sorensen (1989), “Microzonation of denitrification activity in stream sediments as studies with a combined oxygen and nitrous oxide microsensor.” Appl. Environ. Microbiol. 55:1234-1241. Cole, V. et al., (1995), ‘Agricultural Options for Mitigation of Greenhouse Gas Emissions’. In: Climate Change 1995 - Impacts, Adaptations and Mitigations of Climate Change:Scientific - Technical analyses: The Second Assessment Report of the Intergovernmental Panel on Climate Change , R. T. Watson, M. C. Zinyowera and R. M. Moss (eds.), Cambridge University Press, New York, U.S.A. Cooper A.B. and J.G. Cooke (1984), “Nitrate loss and transformation in 2 vegetated headwater streams.” N. Z. J. Mar. Freshwater Res

. 18:441-450. Czepiel, P., P. Crill and R. Harriss (1995), “Nitrous oxide emissions from municipal wastewater treatment.” Environ. Sci. Technol. 29(9):2352-2356. Danso, S.K.A. (1995), Sustainable agriculture. “The role of biological nitrogen fixing plants.” In IAEA (ed.) Nuclear Techniques in Soil-Plant Studies for Sustainable Agriculture and Environmental Preservation , IAEA, Vienna, pp. 205-224. Debruyn, W., G. Lissens, J. Van Rensbergen and M. Wevers (1994), “Nitrous oxide emissions from waste water.” In: J. Van Ham et al. (eds.) 1994:159-165. De Klein, C.A.M. and R.S.P. Van Logtestijn ( 1994), “Denitrification and N 2 O emission from urine-affected grassland soil.” Plant and Soil 163:235-242. DeMore, W.B., S.P. Sander, D.M. Golden, R.F. Hampson, M.J. Kurylo, C.J. Howard, A.R. Ravishankara, C.E. Kolb and M.J. Molina (1994), Chemical kinetics and photochemical data for use in stratospheric modeling , JPL-NASA, Evaluation No. 11. Dentener, F.J. and P.J. Crutzen. (1994), “A three-dimensional model of the global ammonia cycle.” J. Atmos. Chem. 19:331-369. Dowdell, R.J., J.R. Burford and R. Crees (1979), “Losses of nitrous oxide dissolved in drainage water from agricultural land.” Nature 278:342-343. Duff, J.H., F.J. Triska and R.S. Oremland (1984), “Denitrification associated with stream periphyton: Chamber estimates from undisrupted communities.” J. Environ. Qual. 13(4):514-518.

## A GRICULTURE

4.136 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Duxbury, J.M. and A.R. Mosier (1993) “Status and issues concerning agricultural emissions of greenhouse gases.” In: Agricultural Dimensions of Global Climate Change H.M. Kaiser and T.E. Drennen (eds.). St. Lucie Press, Delray Beach, Florida, U.S.A, pp. 229-258. Duxbury, J.M, D.R. Bouldin, R.E. Terry and R.L. Tate III (1982), “Emissions of nitrous oxide from soils.” Nature 298:462-464. Ecetoc (1994), Ammonia emissions to air in Western Europe . Technical Report No 62. Brussels, p. 196. Erich, M.S., A. Bererie, and J.M. Duxbury (1984), “Activities of denitrifying enzymes in freshly sampled soils.” Soil Sci . 38:25-32. FAO (1978-1981), Report of the Agro-Ecological Zones Project . World Soils Resources, Project Volume 3, No. 48 South and Central America, FAO (Food and Agriculture Organization of the United Nations), Rome. FAO (1990a), Fertilizer Yearbook . Volume 39. FAO statistics series No. 95. FAO, Rome. FAO (1990b), Fertilizer Yearbook . Volume 43. FAO statistics series No. 94. FAO, Rome. FAO (1991), Agrostat PC, Land-use, FAO, Rome. Flessa, H., P. Doersch, F. Beese, H. Koenig and A.F. Bouwman, “Influence of cattle excrements on nitrous oxide and methane fluxes in pasture land” (submitted). Galbally, I.E. et al., (1992), Proceedings of IGBP Workshop No. 14. Canberra, Oct. 3-5, 1990. Goreau, T.J., W.A. Kaplan, S.C. Wofsy, M.B. McElroy, F.W. Valois and S.W. Watson. (1980), “Production of NO 2 - and N 2 O by nitrifying bacteria at reduced concentrations of oxygen.” Appl. Environ. Microbiol . 30:526-532. Groenestein, C.M., J. Oosthoek and H.G. van Faassen (1993), “Microbial processes in deep-litter systems for fattening pigs and emissions of ammonia, nitrous oxide and nitric oxide.” In: Nitrogen flow in pig production and environmental consequences M.W.A. Verstegen, et al. (eds.) . Proc. First Int. Symp. on Nitrogen Flow in Pig Production and Environmental Consequences , Pudoc Scientific Publ., Wageningen. pp. 307-312. Groffman P.M., C.W. Rice and J.M. Tiedje (1993), “Denitrification in a Tallgrass Prairie Landscape”. Ecology 74:855-862. Guthrie, T.F. and J.M. Duxbury (1978), “Nitrogen mineralization and denitrification in organic soils.” Soil Sci. Soc. Am. J . 42:908-912. Hanaki, K., Z. Hong and T. Matsuo (1992), “Production of nitrous oxide gas during denitrification of wastewater.” Wat. Sci. Tech. 26(5-6):1027-1036. Haynes, R.J. and P.H. Williams (1993), “Nutrient cycling and soil fertility in the grazed pasture ecosystem.” Advances in Agronomy 49:119-199. Helder, W. and R.T.P. De Vries. (1983) “Estuarine nitrite maxima and nitrifying bacteria (ems-Dollard Estuary).” Neth. J. Sea Res . 17:1-18. Hemond, H.F. and A.P. Duran (1989), “Fluxes of N 2 O at the sediment-water and wateratmosphere boundaries of a nitrogen-rich river.” Water Resources Research 25:839-846. Hill, A.R. (1979), “Denitrification in the nitrogen budget of a river ecosystem.” Nature 281:291-292.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.137 Hill, A.R. (1981), “Nitrate-nitrogen flux and utilization in a stream ecosystem during los summer flows.” Can. Geogr . 25(3):225-239. Hill, A.R. (1983), “Nitrate-nitrogen mass balances for two Ontario rivers.” In: Dynamics of Lotic Ecosystems, T.D. Fontaine and S.M. Bartell (eds.). Ann Arbor Science, Michigan. Hong Z., K. Hanaki and T. Matsuo (1993), “Greenhouse gas-N 2 O production during denitrification in wastewater treatment.” Water Sci.Technol . 7:203-207. Horrigan S.G. and A.L. Springer (1990), “Oceanic and estuarine ammonium oxidation: Effects of light.” Limnology and Oceanography 4:316-328. IPCC (1995), IPCC Guidelines for National Greenhouse Gas Inventories . OECD/OCDE, Paris. Jarvis, S.C. and B.F. Pain (1994), “Greenhouse gas emissions from intensive livestock systems: their estimation and technologies for reduction.” Climate Change 27: 27-38. Jenkins, M.C. and W.M. Kemp (1984), “The coupling of nitrification and denitrifiation in two estuarine sediments.” Limnol. Oceanogr. 29:609-619. Jensen H.B., K.S. Jorgensen and J. Soerensen (1984), “Diurnal variation of nitrogen cycling in coastal marine sediments II. Nitrous oxide emissions.” Mar. Biol. 83:177-183. Jensen M.H., T.K. Andersen and J. Soerensen (1988), “Denitrification in coastal bay sediment: regional and seasonal variation in Aarhus Bight, Denmark.” Mar. Ecol. Prog. Ser. 48:155-162. Jorgensen, K.S., H.B. Jensen and J. Sorensen (1984), “Nitrous oxide production from nitrification and denitrification in marine sediments at low oxygen concentrations.” Can. J. Microbiol . 30:1073-1078. Kaspar, H.F. and J.M. Tiedje (1981), “Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene .” Appl. Environm. Microbiol . 41:705-709. Kaushik N.K. and J.B. Robinson (1976), “Preliminary observations on nitrogen transport during summer in a small spring-fed Ontario stream.” Hydrobiol . 49(1):59-63. Kemp, W.M., P. Sampou, J. Caffrey and M. Mayer (1990), “Ammonium recycling versus denitrification in Chesapeake Bay sediments.” Limnol. Oceanogr . 35:1545-1563. Koops, J.G., O. Oenema and van Beusichem (1995) , Stikstofverliezen door denitrificatie in grasland op veengronden, NWI-LUW, Wageningen, p. 32. Kroeze, C. (1994), Nitrous Oxide; Emission inventory and options for control in the Netherlands . Report No. 773001004. National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands, p. 163. Kumarasinghe, K.S. and D.L. Eskew (1991), “Applications of N-15 isotope techniques in Azolla-rice studies.” In: Stable isotopes in plant nutrition, soil fertility and environmental studies IAEA (ed.)

. IAEA, Vienna. pp.169-178. Lipschultz, F., S.C. Wofsy and L.E. Fox (1986), “Nitrogen metabolism of the eutropic Delaware River ecosystem.” Limnology and Oceanography 29:84-98. Minami, K. and S. Fukushi (1984), “Methods for measuring N 2 O flux from water surface and N 2 O dissolved in water from agricultural land.” Soil Sci. Plant Nutr . 30:495- 502.

## A GRICULTURE

4.138 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Minami, K. and A. Ohsawa (1990), “Emission of nitrous oxide dissolved in drainage water from agricultural land.” In: Soils and the greenhouse effect , A.F. Bouwman (ed.) John Wiley & Sons, New York, pp. 503-509. Monaghan, R.M. and B. Barraclough (1993), “Nitrous oxide and dinitrogen emissions from urine-affected soil under controlled conditions.” Plant and Soil 151:127-138. Mosier, A.R. (1994), “Nitrous oxide emissions from agricultural soils.” Fertilizer Research 37:191-200. Mosier, A.R. and W.J. Parton (1985), “Denitrification in a shortgrass prairie: A modeling approach.” In: Planetary Ecology D.E. Caldwell, J.A. Brierley, C.L. Brierley (eds.) Van Nostrand Reinhold Co., NY, pp. 441-452. Mosier, A.R., D.S. Schimel, D. Valentine, K.F. Bronson and W.J. Parton (1991), “Methane and nitrous oxide fluxes in native, fertilized, and cultivated grasslands.” Nature 350:330-332. Mosier, A.R., J.M. Duxbury, J.R. Freney, O. Heinemeyer and K. Minami. (1995a), “Nitrous oxide emissions from agricultural fields: Assessment, measurement and mitigation.” Plant and Soil. (In press.). Mosier, A.R., J.M. Duxbury, J.R. Freney, O. Heinemeyer and K. Minami (1995b) “Mitigating agricultural emissions of nitrous oxide.” (Submitted to Climatic Change ). Muller, C., R.R. Sherlock and P.H. Williams (1995a), “In-field method to determine N 2 O and N 2 emissions from denitrification and N 2 O emissions from nitrification from urine-affected intensive pasture soil.” (Submitted to Soil Biology and Biochemistry. ) Muller, C., R.R. Sherlock, and P.H. Williams (1995b), “Factors influencing N 2 O emission from pasture soil affected by animal urine or ploughing.” (Submitted to European Journal of Soil Science. ) Nobre, A.D. (1994), “Nitrous oxide emissions from tropical soils.” Thesis. Univ. New Hampshire, Durham, NH., p. 141. Nogita S., Y. Saito, and T. Kuge (1981), “A new indicator of the activated sludge process - nitrous oxide.” Water Sci.Technol . 13:199-204. Oenema, O. and G.L. Velthof (1993), “Denitrification in nitric-acid-treated cattle slurry during storage.” Netherlands Journal of Agricultural Science 41:63-80. O'Hara, G.W. and R.M. Daniel (1985), “Rhizobial denitrification: a review .” Soil Biol. Biochem . 17:1-9. Owens, N.J.P. (1986), “Estuarine nitrification: a naturally occurring fluidized bed reaction?” Estuarine Coastal and Shelf Science 33:31-44. Parashar, D.C. (1991), “Measurement of greenhouse gas emissions in India.” In: Impact of Global Climate Change on Photosynthesis and Plant Productivity , Oxford & IBH Publishing Co., New Delhi. Peoples, M.B., D.F. Herridge and J.K. Ladha (1995), “Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural production?” Plant and Soil 174:3-28. Poggemann, S., F. Weissbach, and U. Kuenzel (1995), N 2 O-Freisetzung von Exkrementflecken auf dem Weideland. Abstract. VDLUFA, Garmisch-Partenkirchen, p. 275.

## 4 A GRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 4.139 Pollaris, L. (1994), “Emission of nitrous oxide from horticultural substrates.” (In Dutch) M.Sc. Thesis. Faculty of Agricultural and Applied Biological Sciences. University of Gent, p. 102. Postma, R., O. Oenema, D.W. Bussink, M. Heinen and J. Van Mollenbroek (1994), “Gasvormige stikstofverliezen bij de teelt van sla op een zandbed onder glas.” Meststoffen pp. 28-34. Robinson, J.B., H.R. Whiteley, W. Stammers, N.K. Kaushik and P. Sain (1979), “The fate of nitrate in small streams and its management implications,” pp. 247-259. In Proc. 10th Annu. Agric. Waste Manage. Conf ., Cornell Univ. Ronen, D., M. Margaritz and E. Alman (1988), “Contaminated aquifers are a forgotten component of the global N 2 O budget.” Nature 335:57-59. Ryden, J.C. (1981), “N 2 O exchange between a grassland soil and the atmosphere.” Nature 292:235-365. Ryden, J.C. (1983), “Denitrification loss from a grassland soil in the field receiving different rates of nitrogen as ammonium nitrate.” J. Soil Sci. 34:355-365. Safley, L.M., M.E. Casada, J.W. Woodbury and K.F. Roos (1992 ), Global methane emissions from livestock and poultry manure , USEPA Report No. 400/1-91/048. Office of Air and Radiation, Washington, D.C., USA, pp. 68, 145 and annexes. Schepers, J.S. and A.R. Mosier (1991), “Accounting for nitrogen in nonequilibrium soilcrop systems.” In: Managing Nitrogen for Groundwater Quality and Farm Profitability R.F. Follett, D.R. Keeney and R.M. Cruse (eds.). Soil Science Society of America, Inc. Madison, Wisconsin, pp. 125-138. Schimel, D.S., W.J. Parton, F.J. Adamsen, R.G. Woodmansee, R.L Senft and M.A. Stillwell, (1986), “The Role of Cattle in the Volatile Loss of Nitrogen from a Shortgrass Steppe.” Biogeochemistry 2:39-52. Seitzinger, S.P. (1988), “Denitrification in freshwater and coastal marine ecosystems : ecological and geochemical implications.” Limnol.Oceanogr . 33:702-724. Seitzinger, S.P. (1990), “Denitrification in aquatic sediments.” In: Denitrification in soil and sediment N.P. Revsbedch and J. Sorensens (eds.), Plenum Press, New York, U.S.A, pp. 301-312. Seitzinger S.P. and C. Kroeze (1996). “Estimates of the spatial distribution of N inputs, nitrous oxide production and denitrification in freshwater and coastal marine ecosystems.” (In preparation). Sherlock, R.R. and K.M. Goh (1983), “Initial emission of nitrous oxide from sheep urine applied to pasture soil.” Soil Biology and Biochemistry 15:615-617. Sibbesen, E. and A.M. Lind (1993), “Loss of nitrous oxide from animal manure dungheaps,” Acta Agriculture Scandianavia Section B: Soil and Plant Science , 43:16- 20. Smith C.J., R.D. DeLaune and W.H. Patrick, Jr. (1985), “Fate of riverine nitrate entering an estuary: I. Denitrification and nitrogen burial.” Estuaries 8:15-21. Spoelstra, S.F. (1985), “Nitrate in silage.” Grass and Forage Science 40:1-11. Steffens, G. and H. Vetter (1990 ), Neue Faustzahlen ueber Nachrstoffgehalte und Naehrstoffanfall . Landwirtsschaftsblatt Weser-Ems. Vol. 3. Swank, W.T. and Caskey, W.H. (1982), “Nitrate depletion in a second-order mountain stream.” J. Environ. Qual . 11:581-584.

## A GRICULTURE

4.140 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Tiedje, J.M. (1988), “Ecology of denitrification and dissimilatory nitrate reduction to ammonia.” In: Biology of Anaerobic Microorganisms, A.J.B. Zehnder (ed.), Wiley, New York, USA, pp. 179-243. Ueda, S., N. Ogura and E. Wada (1991), “Nitrogen stable isotope ratio of groundwater N 2 O.” Geophysical Research Letters 18(8):1449-1452. Ueda, S., N. Ogura and T. Yoshinari (1993), “Accumulation of nitrous oxide in aerobic groundwaters.” Wat. Res . 27(12):1787-1792. Van Cleemput, O., A. Vermoesen, C.J. De Groot, and K. Van Ryckeghem (1994), “Nitrous oxide emission out of grassland.” Environ. Monitor. Assessm. 31:145-152. Van der Hoek, K.W. (1994 ), Berekeningsmethodiek ammoniamemissie in Nederland voor de jaren 1990, 1991 en 1992 . RIVM Report No. 773004003. Van Kessel, J.P. (1977), “Removal of nitrate from effluent following discharge on surface water.” Water Research 11:533-537. Van Vuuren, A.M. and J.A.C. Meijs (1987), In: Animal Manure on grassland and fodder crops: fertiliser or waste? H.G.Van der Meer, R.J. Unwin, T.A. van Dijk and G.C. Ennik (eds.)
, Nijhoff, Dortrecht, The Netherlands, pp. 27-45. Velthof, G.L. and O. Oenema (1993), “Orienterende lachgasemissiemetingen in RWZI’s.” In Capele, A.D. and E.N. Alblasserdam (eds.) NMI-Report 93.263 . Wageningen, p. 6. Velthof, G.L. and O. Oenema (1994), “Effect of nitrogen fertilizer type and urine on nitrous oxide flux from grassland in early spring.” In Grassland and Society, Proceedings of the 15th General Meeting of the European Grassland Federation . L. 't Mannetje and J. Frame (eds.) pp. 458-462. Velthof, G.L. and O. Oenema (1995), “Nitrous oxide fluxes from grassland in the Netherlands: II. Effects of soil type, nitrogen fertilizer application and grazing.” (Accepted for publication in European Journal of Soil Science .) Velthof, G.L., A.B. Brader, and O. Oenema (1996a), “Seasonal variations in nitrous oxide losses from managed grasslands in the Netherlands.” (Submitted to Soil Biology and Biochemistry ). Velthof, G.L., S.C Jarvis, A. Stein, A.G. Allen, and O. Oenema (1996b), “Spatial variability of nitrous oxide fluxes in mown and grazed grasslands on a poorly drained clay soil.” (Submitted to Soil Biology and Biochemistry ). Vetter, H., A. Klasink and G. Steffens (1989), “Mist und Guelleduengung nach Mass.” VDLUFA-Schriftenreihe 19:41-66. Whitehead, D.C. (1970), The role of nitrogen in grassland productivity . Bulletin 48 of Commonwealth Agricultural Bureau, Hurley, UK. WHO/UNEP (World Health Organisation/United Nations Environmental Programme) (1989), Global Pollution and Health. Results of health related environmental monitoring, World Health Organization . Geneva and United Nations Environment Programme, Nairobi, Yale Press, London.Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 5 

# L AND 

# - U SE 

# C HANGE 

# & F ORESTRY

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.1 

# 5. L AND 

# -U SE 

# C HANGE 

# & F ORESTRY



## 5.1 Overview This chapter summarises methods for calculating greenhouse gas (GHG) emissions from human activities which: 1. change the way land is used (e.g., clearing of forests for agricultural use, including open burning of cleared biomass), or 2. affect the amount of biomass in existing biomass stocks (e.g., forests, village trees, woody savannas, etc.). The biosphere is a strong determinant of the chemical composition of the atmosphere. This has been true since the existence of the biosphere, and hence well before the presence of humans. A rich variety of carbon, nitrogen, and sulphur gases are emitted and absorbed by the biosphere. There is, however, strong evidence that the expanding human use and alteration of the biosphere for food, fuel and fibre is contributing to increasing atmospheric concentrations of GHGs. The dominant gas of concern in this source category is carbon dioxide (CO 2 ), and much of the methodology discussion in this chapter is specific to CO 2 . Other important direct GHGs, including methane (CH 4 ) and nitrous oxide (N 2 O), and indirect GHGs, 1 including carbon monoxide (CO), oxides of nitrogen (NO x , i.e., NO and NO 2 ), and non-methane volatile organic compounds (NMVOCs) are also produced from land-use change and forest management activities, particularly where burning is involved. Non-methane volatile organic compounds are emitted in significant quantities from biomass burning. These emissions could be estimated using the same approach provided for other non-CO 2 gases. However, the detailed methods and default information have not yet been developed and are not included in this version of the Guidelines. This is an area to be considered in future improvements to the Guidelines

. Estimates of CO 2 emissions due to land-use change vary considerably because humans interact with the land in a myriad of ways. Estimates vary due to uncertainties in annual forest clearing rates, the fate of the land that is cleared, the amounts of biomass (and hence carbon) contained in different ecosystems, the modes by which CO 2 is released (e.g., burning or decay) and the carbon released when soils are disturbed. The 1995 IPCC Scientific Assessment (IPCC, 1996) estimated the average annual flux due to tropical deforestation for the decade 1980-1989 to be 1.6±1.0 Pg C as CO 2 (CO 2 -C). Carbon sequestration by tropical tree plantations was not explicitly included in these estimates but is thought to be relatively small: in 1980 these plantations were estimated to absorb only 0.03-0.11 Pg CO 2 -C (Brown et al. 1986). Recent analyses have suggested that growth of existing forests in temperate and boreal regions may be a significant carbon sink, potentially as much as 0.7 Pg C annually. Analysts have suggested a number of complementary factors which could be causing these sinks, including regrowth of historically cleared forests, CO 2 fertilisation, and nitrogen fertilisation due to atmospheric deposition (e.g., IPCC, 1995; Kokorin and Nazarov, 1995a; Tans et al., 1990; Kauppi et al., 1992; and Dixon et al., 1994). Based upon the latest estimates of CO 2 sources, sinks and

1 "Indirect" greenhouse gases here refers to gases which, although not important GHGs in their own right, can influence the concentration of some GHGs, tropospheric ozone in particular.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual atmospheric storage, the IPCC estimates a remaining terrestrial sink of 0.9 ± 0.5 Pg C/year to 1.4 ± 1.5 Pg C/year (Schimel et al., 1995; and Brown et al., 1996). This apparent imbalance in the carbon budget, which was previously referred to as a “missing sink,” is believed to be due to CO 2 fertilisation, N fertilisation, climate change (e.g., temperature increase), more extensive regrowth or tree planting programmes in the tropics, and possibly other factors. 2 The precise mix and relative contribution of these processes to the remaining terrestrial sink is still a subject of research and debate; and this terrestrial sink will not necessarily remain the same size or even the same sign under conditions of climate change.
Emissions of non-CO 2 trace gases (CH 4 , CO, N 2 O, and NO x ) due to biomass burning are generally produced immediately and are considered as net emissions. NMVOC are not treated here. Gross emissions of CO 2 due to reductions in forest area may or may not be balanced by uptake of CO 2 and may occur over immediate or delayed time frames. 3 Similarly, increases in forest area or in the biomass density of existing forests will result in CO 2 uptake at varying rates and over delayed time frames. Only about 50- 60 per cent of the carbon estimated to have been released in 1980 from forest conversion was a result of the conversion and subsequent biomass burning in that year. The remainder was a release due to oxidation (i.e., inherited emissions) of biomass harvested in previous years (Houghton, 1991). Other land-use changes, such as land flooding, result in continuous GHG emissions possibly for as long as the land remains in its altered state.



### 5.1.1 Background - Biomass Stocks and Carbon Fluxes Vegetation withdraws CO 2 from the atmosphere through the process of photosynthesis. Carbon dioxide is returned to the atmosphere by the respiration of the vegetation (autotrophic) and the decay of organic matter in soils and litter (heterotrophic respiration). The gross fluxes are large; roughly a seventh of the total atmospheric CO 2 passes into vegetation each year (in the order of 100 Pg CO 2 -C per year), and in the absence of significant human disturbance, this large flux of CO 2 from the atmosphere to the terrestrial biosphere is thought to be balanced by the return respiration fluxes. Land-use change and the use of forests directly alters these fluxes, and their balance, and consequently the amount of carbon stored in living vegetation, litter, and soils. For example, forest clearing for agriculture by burning greatly increases the return flux of CO 2 and decreases for a while the photosynthetic flux. Burning is, after all, simply a rapid form of oxidation or decay. Subsequently, the CO 2 flux of the cleared area will reach a new steady state: the photosynthesis associated with agricultural production being balanced by the respiration of vegetation, the decay of on-site organic material, and the

2 For recent analyses of the effects of changing CO 2 concentrations and climate variables on terrestrial sinks, see, Cramer and Solomon, 1993; Smith and Shugart, 1993; Kokorin and Nazarov, 1995b; Mellilo et al., 1993; and Alcamo et al., 1994. For analysis of the possible effects of N fertilisation from atmospheric deposition, see Gifford, 1994, Rastetter et al., 1992 and Comins and McMurtrie, 1993. It is also possible that atmospheric deposition of air pollutants can damage forests, as discussed in Denniston, 1993, which would reduce the amount of carbon stored in forests. However, it is uncertain whether or not this is a significant effect at global or national scales.

3 Delayed releases of non-CO 2 trace gases are an important research issue. These releases may be important , but are currently too uncertain to be included in calculations.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.3 oxidation of the agricultural product when it is consumed, perhaps off site. However, the total amount of carbon stored in the terrestrial system will have been reduced because a forest contains more carbon than does a field of annual crops or pasture, and the removed carbon (i.e., the forest) was not put into long term storage pools. Consequently there is a net flux of CO 2 from the land (vegetation and soil) to the atmosphere. A natural first order assumption is that the net reduction in carbon stocks is equal to the net CO 2 flux from the cleared area. Forest harvest does not necessarily result in a net flux to the atmosphere. It can produce a complex pattern of net fluxes that change direction over time. For instance, suppose that a forest is harvested, producing wood products and leaving some slash and debris. Initially, the CO 2 flux from the wood products that decay rapidly, plus the increased respiration flux of CO 2 associated with the oxidation of the slash, could exceed the flux from the atmosphere due to photosynthesis and the resulting carbon storage in the regrowing forest. Consequently, there is a net flux of CO 2 from the forest, forest floor and soil to the atmosphere. This would also be reflected in the carbon accounting: the amount of carbon in the original living vegetation, the litter, and the soils would be greater than the amount of carbon in the young regrowing forests, litter, soils and forest products pool. However, if some of the forest products are very long-lived, and if the forest regrows to its original level, then the integrated net flux must have been from the atmosphere to the terrestrial biosphere since the resulting total terrestrial carbon stocks (vegetation, litter, soils, and wood products) would be greater than before the forest harvest. This characteristic, that changes in landuse today affect both present and future CO 2 fluxes associated with that specific landuse, is one feature of CO 2 emissions analysis that distinguishes landuse from fossil fuel consumption. Consequently, when one considers the issue of CO 2 flux associated with landuse today or in any base year, one must consider past land-use activities and their effects upon current fluxes of CO 2 . Box 1 provides some illustrative numerical examples of carbon fluxes associated with land-use change over a series of years.



### 5.1.2 The Proposed Approach
The fundamental basis for the methodology rests upon two linked themes: i) the flux of CO 2 to or from the atmosphere is assumed to be equal to changes in carbon stocks in existing biomass and soils, and ii) changes in carbon stocks can be estimated by first establishing rates of change in land use and the practice used to bring about the change (e.g., burning, clear-cutting, selective cut, etc.). Simple assumptions are then applied about their impact on carbon stocks and the biological response to a given landuse. As noted above, there are large uncertainties in all current methods for estimating fluxes of CO 2 from forestry and land-use change. Direct measurements of changes in carbon stocks are extremely difficult since one must confront the difficulty of determining small differences in large numbers as well as the inherent heterogeneity of terrestrial systems. A more practical first order approach in many countries is to make simple assumptions about the effects of land-use change on carbon stocks and the subsequent biological response to the land-use change, and to use these assumptions to calculate carbon stock changes and hence the CO 2 flux. This observation is at the heart of the proposed approach. Rates of change of land use are difficult to establish, although there are a variety of data on which to base land-use change estimates. The Technical Appendix to this chapter reviews sources of data on rates of tropical deforestation, the land-use change which currently makes the largest contribution to CO 2 flux. Finally, the assumptions regarding the response of vegetation and soils to different land uses and land-use change can be

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual expressed in simple terms which can be altered for specific conditions in different countries or regions. The methodology is designed to be comprehensive, i.e., to cover all of the main land-use change and forestry activities; and to be feasible to implement by all participating countries. It can be implemented at several different levels of complexity and geographic scales, depending on the needs and capabilities of national experts in different countries. 1. A simple, first order approach can be based on very aggregate default data and assumptions, derived from the technical literature, and provided throughout the text. Methods are presented in the context of national level aggregate calculations for a limited set of subcategories which can be supported by these default values. It is important to note that many of the default data provided in the land-use change and forestry chapter are highly uncertain. Many of the important values needed for the calculations are not well established or are highly variable from region to region, or within very small subregions within a given country. In many cases in which values are particularly uncertain (e.g., the fraction of cleared biomass burned on site), these weaknesses are discussed in the text. Where global average values are highly uncertain, they can be used for first order calculations or for comparison, but probably do not provide a basis for a credible final inventory. National experts in forestry and related fields should be consulted to determine the most appropriate values for use in national inventories. 2. A more accurate level can be achieved simply by substituting country-specific values for general defaults provided in the methodology. If appropriate and possible, locally available data can be used to carry out calculations at a more detailed geographic scale and/or subcategory level. Alternative levels of detail are discussed more fully in the next section. National experts are strongly encouraged to substitute more appropriate (i.e., country- or region-specific) and more detailed input data wherever they are available. 3. Forest inventory data can also be used with this methodology. It is important to note that some countries with highly developed forestry industries do in fact keep track of existing commercial forests through periodic detailed inventories. In these countries it is generally the ongoing management of existing forests rather than land-use changes which has the greatest impact on the exchange of GHG between the land and atmosphere. National experts who have very detailed, inventory based data, can re-format and analyse these data to derive equivalent average responses (e.g., annual biomass growth rates by ecosystem type) which can be aggregated up to categories matching the simple approach outlined here. This procedure is discussed in more detail in the changes in forest and other woody biomass stocks section below. The intent is to provide a calculation and reporting framework which can accommodate users with vastly different levels of available data, yet allow them all to present the results on a comparable basis.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.5 B OX 1 I LLUSTRATIVE C ALCULATIONS OF C ARBON F LUXES Consider the example of forest clearing for agriculture which results in a net flux to the atmosphere. For descriptive purposes we consider the following assumptions: 1) a 20 year time frame (e.g., 1970 to 1990); 2) one hectare is cleared each year (so that over the 20 year period, 20 hectares are cleared); 3) cleared land is used as pasture, which is established the year following the clearing; 4) after three years, cleared land is abandoned and it regrows linearly at 10tC/ha per year to 75 per cent its original biomass only in 15 years; 5) all of the vegetation is completely burned at the time of clearing and there are essentially no changes in soil or litter pools; and 6) there are 200 tonnes of carbon per hectare in the forest biomass and 5 tonnes carbon per hectare in the pasture. In the first year, there is a 200 tonne net flux of carbon as CO 2 to the atmosphere. In the second there is a 195 tonne net flux; the clearing of the second hectare is partially balanced by the establishment of the first pasture. In the third, there is a net flux again of 195; the clearing of the third hectare is again partially balanced by the establishment of the second pasture; however, the first pasture is now again in a steady state (as a pasture). The fourth year the pattern is again the same, but in the fifth year the net annual flux drops to 185 as the first pasture is now abandoned and begins to recover to a secondary forest. In the sixth year, the flux drops to 175 as two hectares are recovering to a secondary forest. In this example, in 1989 one hectare would be converted to pasture (200 tonne flux of carbon to the atmosphere), one hectare would have become a pasture (5 tonne flux to the terrestrial biosphere), two hectares would be in steady state as pasture, and 15 hectares would be recovering to secondary forest with one hectare in its final year of recovery (150 tonne flux to the terrestrial biosphere). The gross flux of carbon from land clearing in 1989 would still be 200 tonnes to the atmosphere, but the net flux to the atmosphere in 1989 associated with land clearing would be 45 tonnes of carbon as CO 2 . The 1990 flux would be the same since now the original one hectare of pasture would have reached a new steady state as a secondary forest. Many variations on this example can be devised: e.g., conversion of some vegetation to charcoal, varying deforestation and regrowth rates. For instance, if the land clearing rates declined over the time period, the 1990 net flux could easily be from the atmosphere to the biosphere even though the net integrated flux over the time period was to the atmosphere. There are other complexities such as the variety of land-use practices, different assumptions about biomass densities, recovery rates, the dynamics of the associated litter and soil pools, and so forth. However, the net flux to or from a particular site will always be reflected in the change of carbon stocks on site and/or in the products pools associated with the site. Thus, a methodology that determines carbon stock changes also provides estimates of the net fluxes of CO 2 .

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.1.3 Priority Categories In estimating the effects of landuse and land-use changes on the emissions of GHGs, it is reasonable to stage the calculation methods so that the most important components canbe addressed first. Complexities and subtleties of the relationship of forestry and landuse change to fluxes of CO 2 and other gases can be incorporated in a consistent manner into subsequent calculations as knowledge advances and data improve. The methodology presented in this chapter focuses initially on a simple, practical and fair procedure for determining the biomass-derived CO 2 flux directly attributed to forest management and land-use change activities. This procedure must also account for the influence of inherited “emissions” or past land-use changes upon the contemporary CO 2 flux, 4 as wellas trace gas emissions from biomass burning where this occurs in conjunction with landuse change. 5 The general forest and grassland ecosystem categories are listed in Box 2. Detailed description of tropical forest types and regional forest formations are presented in Table 5-1. On a global scale, the most important land-use changes that result in CO 2 emissions and removals are:

• changes in forest and other woody biomass stocks - the most important effects of human interactions with existing forests are considered in a single broad category, which includes commercial management, harvest of industrial roundwood (logs) and fuelwood, production and use of wood commodities, and establishment and operation of forest plantations as well as planting of trees in urban, village and other non-forest locations; 6

• forest and grassland conversion - the conversion of forests and grasslands to pasture, cropland, or other managed uses can significantly change carbon stored in vegetation and soil; 7

• abandonment of croplands, pastures, plantation forests, or other managed lands which regrow into their prior natural grassland or forest conditions.

• changes in soil carbon.
The method also addresses the immediate release of non-CO 2 trace gases (CH 4 , CO, N 2 O and NO x ) from the open burning of biomass from forest clearing.

4 Similarly, current land-use changes will affect future fluxes of CO 2 . 5 Burning of biomass residues can occur in other situations which are not land-use change, e.g., in the use of forests or other biomass stocks as a part of the ongoing management of these stocks without changing the land use. This should be treated in the same way as burning of cleared forests for calculation of non-CO 2 GHG from burning.

6 Changes in forest and other woody biomass stocks are accounted for in each Inventory Year.

7 Conversion of forests is also referred to as "deforestation" and it is frequently accompanied by burning.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.7 B OX 2 F OREST AND G RASSLAND C ATEGORIES Ecosystem categories have been established based on conventions common in the literature. For the tropics, the categories are based mainly on the FAO system (FAO 1993a) to be consistent with the tables of default values provided, and used in the simple calculations presented in the Workbook. National experts are free, indeed encouraged, to use more detailed characterisations of ecosystems in their countries if the data are available and differences are important for carbon calculations. If more detailed categories are used, however, it is necessary to aggregate these up to match the broad specified categories in order to ensure consistency and comparability with national data across all participating countries. The categories are presented as follows: Ecosystem Types Tropical Ecosystems

Forests Wet Moist with short dry season Moist with long dry season Dry Montane moist Montane dry Grasslands/Shrublands Mainly herbaceous and shrub savannas/ grasslands Temperate Ecosystems

Forests Broadleaf Coniferous
Grasslands Boreal Ecosystems

Forests Coniferous Mixed broadleaf-coniferous Forest-tundra
Grasslands/Tundra Within each ecosystem category, subdivisions are recommended where data are available. For example, tropical forests are defined as ecosystems with a minimum of 10% crown cover of trees and/or bamboos, generally associated with wild flora, fauna and natural soil conditions, and not subject to agriculture practices. They can be divided into:

Closed forests - Characterised by crown cover higher than 40% Open forest - Characterised by crown cover between 10 and 40%. Degraded forests or grasslands - Forests or grasslands that are have been overused or poorly managed and are likely to have reduced biomass densities.

Protected forests or grasslands - Forests or grasslands that are designated as national parks or in other ways are legally protected.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-1 T YPES OF T ROPICAL F ORESTS AND R EGIONAL F OREST F ORMATIONS Types of tropical forests a

Wet Moist with short dry season Moist with long dry season Dry Montane Moist Montane Dry

R ≥ 2000 2000>R>1000 R<1000 R>1000 R<1000

Forest Mainly evergreen Mainly moist deciduous Mainly dry deciduous Very dry deciduous Mainly evergreen Mainly dry deciduous

Typical regional forest formations:
Africa Lowland rain forests Lowland evergreento semiever-green forests Dry deciduous forests and miombo woodlands Deciduous forests and woodlands. Very dry savanna and steppe Montane evergreen forests Scrub forests and evergreento semievergreen thickets

Asia Tropical lowland evergreen rain forests Dense semideciduous

or deciduous forests Dry deciduous forests Low deciduous forests. Thorn forests Tropical and wet and moist forests Dry evergreen forests orpseudosteppic vegetation
America Ombrophilous forests Evergreen seasonal forests. Tropical and subtropical forests Cerrados or pantanal Open deciduous forests Tropical evergreen and/or seasonal forests Dry deciduous forests or shrub

savanna. Arid subdesertic matorrales Open formations of the different climatic zones: Open Forest Mainly evergreen degraded Mainly moist deciduous Mainly woodlands and tree

savanna Dry woodlands and tree

savanna Mainly degraded evergreen and seasonal Mainly dry

savannas

Note: R= annual rainfall in mm/yr
a The ecological conditions which characterise these main vegetation cover classes are: Wet - Evergreen dense forests which receive more than 2000 mm per year rainfall evenly throughout the year. Moist with short dry season - Deciduous forests, characterised by a short dry season (<4-5 months), and rainfall 1000-2000 mm per year. Moist with long dry season - Woodlands and open forests, characterised by a long dry period (>5 months), and rainfall 1000- 2000 mm per year. Dry - Woodlands and tree savannas which receive less than 1000 mm per year of rainfall, very seasonally distributed. Montane moist and dry- Main features of this zone are altitude above 1000 metres and rainfall above and below 1000 mm per year respectively.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.9 

### 5.1.4 Relationships among Categories It is possible that some areas of land can fit the definitions of two categories - e.g., abandoned lands regrowing and changes in woody biomass stocks - simultaneously. In this situation, the most recent, significant human interaction should be used to allocate land into categories. Even though an area may have been abandoned and allowed to regrow, if it subsequently begins to be “managed” (e.g., as a significant source of fuelwood) it should be reclassified in the changes in forest and other woody biomass stocks category. It is important to recognise some key linkages and interactions both among components of the land-use change and forestry methods and with other calculations discussed in other chapters. Figure 5-1 illustrates a number of complicated relationships among these categories and also with biomass fuel combustion which is covered in the energy source category. Key linkages which should be understood are:
1. To estimate CO 2 emissions from burning of cleared forests , it is only necessary to know the total amount of biomass which is burned in the Inventory Year. 2. However, it is necessary to divide this burning into on-site and off-site (fuelwood) portions for two reasons: First, the type of burning affects the emissions of non-CO 2 trace gases such as CH 4 so that different emission factors may be applied to open burning on-site and to fuelwood use off-site. Secondly, the amount of fuelwood removed from cleared forests must be deducted from the total biomass cleared to prevent double counting in the fuelwood consumption calculations. This is only an issue for those countries which must infer some or all of forest harvest from wood consumption surveys. 3. Fuelwood Consumption Information. Countries which have accurate and complete statistics on direct harvesting of all types of wood from biomass stocks, and all uses of biomass for fuel, should use locally available data. Many countries, however, have significant amounts of wood removed from forests, primarily for domestic fuel use, which are not accounted for in commercial harvest statistics. For these countries, a Fuelwood Consumption Accounting approach is provided which uses data from the FAO Yearbook of Forest Products. Fuelwood consumption information is used in two ways:

− for estimating non-CO 2 trace gas emissions from biomass fuel combustion (in the Energy Section of the methodology); and

− total wood consumption, corrected to deduct any wood which has come from forest clearing, is also a key input to the calculations of net CO 2 emissions or removals from changes in forest and other woody biomass stocks

.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5 . 1 . 5 C h a p t e r O r g a n i s a t i o n The remainder of this chapter presents methods for calculating GHGs from land-use change and forestry in two stages. The next section, Basic Calculations , presents initial simple calculations for each of three broad categories of forestry and changes in land use identified above. These categories also correspond directly to the subsections of the Land-use Change and Forestry Module of the Workbook

. The second stage, Refinements in Calculations , discusses a range of complexities and refinements which ideally could be included in such calculations, as data and understanding permit, in order to improve accuracy and completeness. These possible refinements include more detailed treatment of some aspects of the basic categories of land uses and land-use changes, as well as additional categories, which can affect carbon stocks and are potentially important for other GHGs. Issues discussed include the delayed release (or uptake) of non-CO 2 trace gases after burning of forests (either as a prescribed forest management tool or as a means of land-clearing), forest degradation, traditional shifting cultivation, and conversion of wetlands to other land uses or the reverse. These activities and other refinements can be incorporated in more detailed versions of the calculations. FIGURE 5-1 : RELATIONSHIPS AMONG CATEGORIES

Forest and Grassland Conversion

Immediate Release from Burning

Delayed Release from Decay (10 yrs) Total On site Burning

C Off-site Burning Non-CO 2 Trace Gases from Open Burning CH 4 , CO, N 2 O and NO

X Emissions

CO 2 Emissions

Abandonment of Managed Lands

CO 2 Emissions and
Removals CO 2 Removals

Changes in Forest and Other

Land-Use Change and Management CO 2 Emissions and Uptake by Soils from Woody Biomass Stocks

Emissions and Removals from Soils (20 yrs)

Annual Growth Increment

Non-CO 2 Gases from Biomass Fuel
Combustion Annual harvest from Stocks = total fuelwood demand - quantity of fuelwood from cleared forests + commercial and other non-fuel harvests Annual Growth Increment minus Harvest from Stocks Net CO 2 Emissions and Removals

CH 4 , CO, N 2 O
and NO X Emissions Quantity of Biomass Fuel L A N D

U S E

C H A N G E

&

F O R E S T R Y

E N E R G Y

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.11 A Technical Appendix , as mentioned, is also provided, which deals with sources of information on rates of land-use change, a critical activity data input for calculating GHG emissions.



## 5 . 2 Ba s i c C a l c u l a t i on s

5.2.1 Introduction The basic calculations focus primarily on the land-use changes (causing changes in land cover) and land-use activities (forestry) that result in the largest, potential flux of CO 2 to the atmosphere or have the largest potential for sequestering carbon. Two categories of land-use change are considered:

• forest and grassland conversion to agricultural lands

• abandonment of managed lands In contrast to most GHG emission methodologies, estimating sources and sinks of CO 2 from land-use change requires the consideration of events over a long period of time. When forests are cleared or agricultural lands abandoned, the biological responses result in "commitments" of fluxes of carbon to or from the atmosphere for many years after the land-use change. This methodology is designed to produce an emissions estimate that is comparable to other elements of the inventory, fossil fuel emissions, for example. That is, it attempts to quantify the flux to or from the atmosphere in the Inventory Year . To do this, it is necessary to obtain estimates of land-use change activities for many years prior to the Inventory Year, and estimate the effects of these activities on the current year fluxes. The two selected categories are considered to be the most important land-use changes affecting CO 2 fluxes, but are not a comprehensive set. Many relevant land-use changes are excluded from the basic calculations. These are discussed in the last section of this chapter. Relevant forestry (on-going land use) activity is combined in one very broad category, changes in forest and other woody biomass stocks , which is defined to include a wide variety of practices. Key examples are establishing and harvesting plantations, commercial forest management and harvesting, fuelwood gathering, and use of harvested wood. Conceptually, this category is intended to account for all significant human interactions with forests and other woody biomass stocks which affect CO 2 fluxes to and from the atmosphere, but which do not result in a land-use change. It is intended to account, at least on a crude level, for all existing forests, but two comments are important here. 1. Natural, unmanaged (for wood products) forests are not considered to be either an anthropogenic source or sink, and are excluded from the calculations. However, in most countries of the world, a few undisturbed (by humans) forests exist, and they could still be sequestrating carbon as they regrow to a mature forest. The lack of consideration of these “undisturbed” forests in the tropics, for example, could lead to an underestimation of carbon sinks in this region. Tropical countries need to establish a permanent forest inventory monitoring network to determine if the “undisturbed” forests are sinks or not. Current research in the Amazon countries suggest some undisturbed forests are carbon sinks (Lugo and Brown, 1992; and Grace et al., 1995).

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2. Forests regrowing naturally on abandoned lands are a net carbon sink attributable to past human activities and are accounted for separately. "Abandoned" lands are by definition assumed not to be subject to ongoing human intervention (of significance to carbon stocks) after abandonment. 8 NOTE: Forests classified as natural, or abandoned/regrowing, can be excluded from the woody biomass stocks accounting only if there is no significant current human interaction with these forests. If they are being used as a source of fuelwood, or are being affected in other ways by ongoing human activities, they should be accounted for on an annual basis as part of changes in forest and other woody biomass stocks . In many countries, lands which are classified as natural or abandoned are in fact harvested informally. Thus, in some countries or regions with fuelwood shortages, little forest will actually fall into the natural or abandoned categories. Several simplifying assumptions are made in the basic calculation methodology. A number of refinements are possible to improve on these basic calculations. One important option is to implement the basic calculations at a more detailed level of subcategories or geographic detail. National experts are strongly encouraged to do so if data are available. Box 3 discusses possibilities for adapting the methodology to various levels of detail, depending on the capabilities and data available to the user, and the relative importance of various components to the individual country. Other possibilities for improving the accuracy and completeness of the basic calculations are possible. For example, the fate and amount of belowground biomass (roots, etc.) is currently ignored in the calculation. The section entitled Refinements to Calculations , later in this chapter, reviews a number of possible additions and refinements.

8 Abandoned lands which are regrowing naturally may be cleared again. In this case, they should shift again to cleared lands, probably with a lower value for preclearing biomass density than when they were first cleared.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.13 B OX 3 A LTERNATIVE L EVELS OF D ETAIL For simplicity and clarity, this chapter discusses calculation of emissions at a national level and for a relatively small number of subcategories within each category of land-use change and forestry. The level of detail in the subcategories is designed to match the available sources of default input data, carbon contents and other assumptions. It is important, however, for users of these emissions methodology guidelines to understand that they are not only permitted but encouraged to carry out the GHG emissions inventory calculations at a finer level of detail, if possible. Many countries have more detailed information available about land-use change, forests and agriculture, than was used in constructing default values here. It may be important in such countries to carry out emissions calculations at finer levels in two ways: 1. Geographic detail at a regional, rather than a national, level If data are available, experts may find that GHG estimation for various regions within a country are necessary to capture important geographic variations in ecosystem types, biomass densities, fractions of cleared biomass which are burned, etc. 2. Finer detail by subcategory If data are available, experts may subdivide the recommended activity categories and subcategories to reflect important differences in ecology or species, land use or agricultural practices, bioenergy consumption patterns, etc. In all cases, working at finer levels of disaggregation does not change the basic nature of the calculations, although additional data and assumptions will generally be required beyond the defaults provided in the chapter. Once GHG emissions have been calculated at whatever is determined by the national experts to be the most appropriate level of detail, results should also be aggregated up to the national level and the standard categories requested in the IPCC proposed methodology. This will allow for comparability of results among all participating countries. Generally, the data and assumptions used for finer levels of detail should also be reported to the IPCC to ensure transparency and replicability of methods. Volume 1: Reporting Instructions discusses these issues in more detail.



### 5 . 2 . 2 C h a n g e s i n F o r e s t a n d O t h e r W o o d y Biomass Stocks The category changes in forest and other woody biomass stocks as used in these basic calculations is very broad, potentially including a wide variety of land-use practices. This discussion focuses heavily on changes in forests, which globally account for the largest component of annual changes in biomass stocks. However, other types of biomass such as non-forest trees (e.g., in villages, cities, etc.) and woody shrubs in grasslands should be included when they are a significant component of total changes in biomass stocks, as is likely to be the case for some specific countries. A basic organising concept in this chapter is that all existing forests can be allocated into one of three categories.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.14 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1. Natural, undisturbed forests, where they still exist and are in equilibrium, should not be considered either an anthropogenic source or sink. They can therefore be excluded from national inventory calculations. NOTE: Many countries may have little or no forests or woody biomass stocks which are not affected significantly by humans. In areas with severe fuelwood shortages, for example, significant biomass - and hence carbon - may be removed for fuel annually even from “natural forests” and abandoned lands. 9 2. Forests regrowing naturally on abandoned lands are a net carbon sink attributable to past human activities and are accounted for as discussed in a later section. While the current regrowth is considered a response to past anthropogenic activity, "abandoned" lands are by definition assumed not to be subject to ongoing human intervention (of significance to carbon stocks) after abandonment. 3. All other types of forest are included in the changes in forest and other woodybiomass stocks category. That is, any forest which experiences periodic or ongoing human interventions that affect carbon stocks should be included here. In the basic calculations, the chapter focuses primarily on a few types of human interactions with forests which are believed to result in the most significant fluxes of carbon. National experts are encouraged, however, to estimate emissions for any activity related to existing forests which is considered to result in significant carbon emissions or removals, and for which necessary data are available. Any such activities falling within our broad definition of changes in forests and other woody biomass stocks should be included in this category and reported to the IPCC as discussed in Volume 1: Reporting Instructions

. Some of the activities in the changes in forest and other woody biomass stocks category which can potentially produce significant carbon fluxes are:

• management of commercial forests - including logging, restocking, selective thinning, etc., as practised by commercial forest products industries

• establishment and management of commercial plantations 10

• other afforestation, and reforestation programmes

• informal fuelwood gathering This category also includes trees which may not traditionally be considered part of "forests". It can include village and farm trees if these are important for biomass and biofuel accounting in some developing countries. It can also include urban trees, trees

9 Also, as discussed in the chapter introduction, there are likely to be widespread human induced effects, e.g., CO 2 fertilisation and nitrogen deposition, which cause changes in virtually all terrestrial biological systems. In this sense, there may be no natural forests which are not subject to human induced GHG emissions or removals. However, at present, the understanding of these broad effects is so uncertain, and quantitative estimation so difficult, that they are not included in the basic calculations recommended for all national inventories.

10 Plantations are forest stands that have been established artificially, to produce a forest product "crop". They are either on lands that previously have not supported forests for more than 50 years (afforestation), or on lands that have supported forests within the last 50 years and where the original crop has been replaced with a different one (reforestation) (Brown et al., 1986).

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.15 planted along highways, aircraft runways, etc., if these are considered significant for a particular country's biomass calculations. These dispersed trees do not contribute greatly to carbon fluxes to or from the atmosphere on a global scale. However, in some countries, they may be important in accounting for the total amount of wood used for fuel. Also, they may be of interest to some countries because of their potential use in response strategies. For these reasons, they are included in the basic calculation methods. National experts who feel they are important, and have the necessary locally available data, can include them. In addition to trees in non-forest locations, in some countries, woody biomass from shrubs or other plants, in grasslands or other locations, may play a significant role in total fuelwood supply. If this is the case, the annual supply of biomass from these “non-trees” must be included in the overall fuelwood accounting. Otherwise the loss of biomass stocks in forests may be overstated. As illustrated in the above list, the changes in forest and other woody biomass stocks category includes some tree planting activities which, strictly speaking, are land-use changes . Plantation establishment and other afforestation/reforestation programmes are examples. It is recognised that this is conceptually inconsistent as the category is intended to account for ongoing interactions with existing forests. However, from a pragmatic perspective, including these activities within the category can simplify the calculations. These subcategories are land-use changes which create new forest stocks. As soon as the land-use change occurs (i.e., the tree planting), the new land use becomes part of the changes in forest and other woody biomass stocks category which is accounted for on an annual incremental basis. Although it would be possible, it is not necessary to estimate the lagged effects of this change as is done with other land-use changes. 11 While including such a range of tree-related activities in one category may introduce some confusion, the calculation procedure is basically the same for all subcategories, and this allows the simplest possible set of emissions calculations. As discussed above, if lands previously considered abandoned and regrowing, or natural forests, are being affected by human activity in the inventory year, they should be reclassified into the changes in forest and other woody biomass stocks category. As discussed in the Overview , the methodology is designed to accommodate users at several levels of detail. This is especially important in the managed forests category. Possible levels include: 1. A simple first order approach, covering the main subcategories, with calculations based on simple default assumptions and default data provided. NOTE: An inventory of land-use change and forestry emissions developed on default values only is unlikely to be considered credible for any country which has significant emissions or activities in these areas. 2. Calculations at the same level of detail but substituting more appropriate data and assumptions from local sources.

11 There is one omission in this accounting which may be important for some countries. If plantations are established on previously unforested lands, there may be a long term accumulation of carbon in the soil as a result of the land-use change. This would not normally be picked up in the simple changes in forest and other woody biomass stocks calculations. It could be added if national experts have detailed data on the preplantation land uses, the soil carbon contents and rates of accumulation, etc.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.16 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 3. Calculations following the same structure, but broken down to finer levels of detail to improve accuracy and utility of estimates, where locally available data can support this. 4. Estimates derived from much more detailed and precise inventory-based forest accounting methods. These results can be reformatted and presented in the form of calculations comparable to those used by the other national experts operating with less detailed data. It is highly desirable that the methodology be relevant for countries which have access to much more detailed data on changes in forest stocks. Some countries with highly developed forestry industries do in fact keep track of existing commercial forests through periodic detailed surveys For such countries, it is possible to derive from survey results aggregate values comparable to the data and assumptions used in the simple approach, and present them in this common format. This will assist all interested parties in evaluating various national estimates on a comparable basis, and will thus be necessary to comply with requirements of Volume 1: Reporting Instructions . Box 4 provides some further discussion of these procedures.

B OX 4 A DAPTING D ETAILED F OREST I NVENTORY D ATA TO THE IPCC F ORMAT A number of countries with highly developed commercial forestry industries routinely collect forest biomass data at a detailed inventory level which allows for relatively precise and direct assessment of the changes in biomass stocks, and equivalent carbon fluxes. National experts working with data of this kind should be able to derive from it values equivalent to those used in calculating emissions with the IPCC methodology. Regardless of how detailed the data base used may be, the results ultimately must be presented in units (e.g. Gg) of carbon and CO 2 emitted or removed in a given average response category (e.g., annual biomass growth rates by ecosystem type). Similarly, the number of hectares of forest in various types can be aggregated up to categories matching the simple approach outlined here. The amount of biomass removed as commercial harvest or for other reasons, should also be relatively well established in such inventories. With these data, it should be possible to, in effect, work backwards to derive the necessary input assumptions and aggregate values. For example, national experts might start with a change in total biomass for specified forest types (and/or regions) over a specified time period. Then they could add the amounts of biomass removed through commercial harvest or for other reasons (e.g., thinning), to get the total growth of biomass over the period. This could then be divided by the number of kilohectares in the category (and the number of years, if a multi-year period) to get average annual growth rates by category. This would then provide all the values needed to reconstruct the calculations in a comparable form to those from countries with minimal data. The national emission/removal estimates presented in this form would then be easily understood and compared by all other parties involved in the international climate change discussions. The intent is to provide a calculation and reporting framework which can accommodate users with vastly different levels of data available, yet allow them to present the results on a comparable basis.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.17 Changes in forest and other woody biomass stocks may be either a source or a sink for carbon dioxide for a given year and country or region. The simplest way to determine which, is by comparing the annual biomass growth versus annual harvest, including the decay of forest products and slash left during harvest. Decay of biomass damaged or killed during logging results in short-term release of CO 2 . For the purposes of the basic calculations, the recommended default assumption is that all carbon removed in wood and other biomass from forests is oxidised in the year of removal. This is clearly not strictly accurate in the case of some forest products, but is considered a legitimate, conservative assumption for initial calculations. Box 5 provides some further discussion of this issue.

B OX 5 T HE F ATE OF H ARVESTED W OOD Harvested wood releases its carbon at rates dependent upon its method of processing and its end-use: waste wood is usually burned immediately or within a couple of years, paper usually decays in up to 5 years (although landfilling of paper can result in longer-term storage of the carbon and eventual release as methane or CO), and lumber decays in up to 100 or more years. Because of this latter fact, forest harvest (with other forms of forest management) could result in a net uptake of carbon if the wood that is harvested is used for long-term products such as building lumber, and the regrowth is relatively rapid. This may in fact become a response strategy.
For the initial calculations of CO 2 emissions from changes in forest and other woody biomass stocks, however, the recommended default assumption is that all carbon in biomass harvested is oxidised in the removal year. This is based on the perception that stocks of forest products in most countries are not increasing significantly on an annual basis. It is the net change in stocks of forest products which should be the best indicator of a net removal of carbon from the atmosphere, rather than the gross amount of forest products produced in a given year. New products with long lifetimes from current harvests frequently replace existing product stocks, which are in turn discarded and oxidised. The proposed method recommends that storage of carbon in forest products be included in a national inventory only in the case where a country can document that existing stocks of long term forest products are in fact increasing. If data permit, one could add a pool to Equation 1 (1) in the changes in forest and other woody biomass stocks calculation to account for increases in the pool of forest products. This information would, of course, require careful documentation, including accounting for imports and exports of forest products during the inventory period.

The net growth of biomass stocks (and accumulation of carbon) depends on the type of biomass stock and the intensity of harvesting. Well managed commercial forests, replacing natural forests, would over the long term be expected to have net emissions close to zero. In many cases, where historically cleared areas are regrowing under commercial management, with limited logging, the forest areas are currently a net sink. If

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.18 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual forests (or parts of forests) are logged or harvested at a rate which exceeds regrowth, then there is a net loss of carbon. 12 Establishment of plantations and other tree planting activities result in absorption of CO 2 from the atmosphere and storage of this carbon until the vegetation is burned or decays. Restocking of managed forests, planting of urban, village and farm trees, and establishing plantations on unforested lands, therefore, result in an uptake of carbon from the atmosphere, at least until the biomass is harvested and enters a decay pool, or the system reaches maturity. The effect of plantation establishment can be to create a net sink for carbon even if the plantation is harvested for products that are rapidly oxidised (e.g., fuelwood). If the plantations are harvested so that there is no net loss of biomass over time (i.e., harvested in a sustainable fashion), then the rate of carbon accumulation on land is positive (or at least non-negative) and tied directly to changes in the area of plantations and their average biomass. The conversion of natural forests to plantations may result in an initial loss of biomass carbon due to an initial reduction in standing biomass. If plantations are established by first clearing existing forests, the initial loss should appear under forest and grassland conversion below. Reaccumulation of biomass in these plantations in subsequent years would be accounted for here under changes in forest and other woody biomass stocks. The approach accounts for all plantations in operation in the inventory year, including both previously planted and newly established plantations. The method for calculating the net changes in biomass stocks is shown in Equation 1. For non-forest trees such as village and farm trees, accounting would be done on the basis of numbers of trees (e.g., in thousands) rather than for hectares of land. The calculations would be the same, except that average annual growth would be expressed in tonnes dm per thousand trees rather than per hectare. The recommended unit of calculation is tonnes of dry biomass, and it is necessary to convert to carbon for emissions estimation. A general default value of 0.50 tonnesC/tonne dry biomass is recommended for all biomass calculations. If more accurate conversion values are available for the particular system, these should of course be used.

12 In addition, logging provides access to previously inaccessible forests, thereby facilitating degradation of forests by activities such as fuelwood collection, habitation, and agricultural activity.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.19 E QUATION 1 (1) hectares of land in a particular category (e.g., plantations)

x average annual growth per hectare in biomass

= gross annual growth increment. total biomass increment is the sum of all relevant categories

. (2) total harvest by category (including fuelwood gathering)

x expansion ratio to treat slash

= gross annual biomass loss. total harvest and other biomass loss is the sum of all relevant categories of harvest. (3) total annual growth increment - total annual biomass loss

= annual biomass change (positive or negative).

Growth Increments Estimates of average annual accumulation of dry matter as biomass per hectare are presented for forests naturally regrowing by broad category in Table 5-2. These values can be used as default values for growth rates in similar managed forest categories if no other information is available. For forests which are more intensely managed (e.g., with periodic thinning, restocking, etc.) annual growth increments could be quite different. Values for some typical plantation species are presented in Table 5-3 and can be used as default values. As discussed in notes in these tables, average growth rates represent a great deal of variability within regions and even from site to site. It is always strongly recommended that locally available data be used or developed if possible in national inventory calculations.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-2 A NNUAL A VERAGE A BOVEGROUND B IOMASS U PTAKE BY N ATURAL R EGENERATION ( tonnes dm/ha) Tropical Regions Forest Types
Moist Forests Seasonal Forests Dry Forests
0-20 Years 20-100 Years 0-20 Years 20-100 Years 0-20 Years 20-100 Years
America 8.0 0.9 5.0 0.5 4.0 0.25
Africa 11 1.0 7.0 0.7 4.0 0.25
Asia 11 1.0 7.0 0.7 4.0 0.25 Note: Growth rates are derived by assuming that tropical forests regrow to 70% of undisturbed forest biomass in the first twenty years. All forests are assumed to regrow to 100% of undisturbed forest biomass in 100 years. Assumptions on the rates of growth in different time periods are derived from Brown and Lugo (1990). 0-20 Years 20-100 Years Temperate Forests Evergreen 3.0 3.0
Deciduous 2.0 2.0
Boreal Forests 1.0 1.0 Note: Temperate and boreal forests actually require considerably longer than 100 years to reach the biomass density of a fully mature system. Harmon et al. (1990), for example, report carefully designed simulations indicating that a 100-year old stand of Douglas fir would contain only a little over half the biomass of a 450-year old growth stand of the same species. There is also evidence that growth rates in temperate and boreal systems are more nearly linear over different age periods than is the case in tropical systems. Nabuurs and Mohren (1993) suggest that growth rates for several different species in temperate and boreal zones rise slowly to peak at ages of 30-55 years and decline slowly thereafter. This suggests that using the same default values for 0-20 year and 20-100 years may be a reasonable first approximation. Nabuurs and Mohren (1990) also illustrate that growth rates may vary as much as a factor of ten for stands of the same species and age, depending on sitespecific conditions. The table values are very general representative global values from Houghton et al. (1983 and 1987). ALL OF THESE REGIONAL AVERAGE GROWTH RATES SHOULD BE CONSIDERED INDICATIVE ONLY. IF FORESTS ARE A SIGNIFICANT PART OF A COUNTRY’S TOTAL GHG INVENTORY, LOCALLY AVAILABLE DATA OR EXPERT JUDGEMENT SHOULD BE SOUGHT TO DEVELOP VALUES REFLECTING CONDITIONS AND PRACTICES.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.21 T ABLE 5-3 A VERAGE A NNUAL A CCUMULATION OF D RY M ATTER AS B IOMASS IN P LANTATIONS Forest Type Annual Increment in Biomass (tonnes dm/hectare/year) Tropical Acacia spp. 15.0 Eucalyptus spp. 14.5 Tectona grandis 8.0
Pinus spp. 11.5
Pinus caribaea 10.0
Mixed Hardwoods 6.8 Mixed Fast-Growing Hardwoods 12.5

Mixed Softwoods 14.5 Temperate Douglas fir 6.0 Loblolly pine 4.0 Sources: Derived from Brown et al., 1986. Farnum et al., 1983. Note: These are average accumulation rates over expected plantation lifetimes; actual rates will vary depending on the age of the plantation. The data for the temperate species are based on measurements in the United States. Data on other species, and from other regions, should be supplied by individual countries (as available). Additional temperate estimates by species and by country can be derived from data in ECE/FAO (1992), assuming that country averages of net annual increment for managed and unmanaged stands are reasonable approximations for plantations.

Biomass Loss Two approaches can be used to estimate biomass harvest and other losses from managed forests. Depending on the data collection and typical forestry practices in a given country, it may be appropriate to use either approach alone, or use both if the two approaches complement each other. This judgement must be made by national experts in each country.
**Commercial Harvest Statistics.** The first, and obvious, approach is to use statistics on amounts of biomass actually removed from forests. In countries where commercial harvests of various kinds make up a large majority of total biomass losses, and statistics are well maintained, this may be the only approach needed. Country-specific estimates of commercial harvest statistics are provided in annual FAO Forest Products Yearbooks (1993b), and periodic Assessments (e.g., FAO, 1993a), and are also generally available from national governments. In using commercial harvest statistics, users must pay careful attention to the units involved. Commercial harvest statistics are often provided for the commercial portion of biomass only, in cubic metres (m 3 ) of roundwood. If this is the case, values will need to be converted to tons of dry biomass, and total biomass removed including slash. Some general default values for converting volume data to tons are 0.65 t dm/m 3 for deciduous trees and 0.45 t dm/m 3 for conifers. See Box 6 for more detailed information. To account for the biomass lost beyond the commercial wood portion, expansion ratios can be applied. Some general default values from the literature are 1.75 for undisturbed

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual forests and 1.90 for logged forests. 13 There is considerable variability in these conversion values and expansion ratios, so it is highly desirable to use more specific locally available data. Also, some commercial harvest data may be reported as equivalent total biomass (i.e., expansion ratios already applied). It is important to check carefully the information in the original harvest data to ensure that expansion ratios are used only where appropriate. 14

B OX 6 V

ARIABILITY IN D ENSITIES OF T REE S PECIES There is considerable variation in average densities for different tree species. While the broad average default values given in the text can be used for initial calculations, it is much better to use actual measured average values if available, or literature values specific to the dominant species in a particular forest. Dixon et al. (1991), for example, give densities for over 150 individual species, which range from 0.31 to 0.86 g/cm 3 . Other sources of wood densities include USDA Forest Service (1987), Cannell (1984), Schroeder (1992), Dewar and Cannell (1992), UN ECE/FAO (1992), Nabuurs and Mohren (1993) and Hamilton (1985).

**Fuelwood Consumption Accounting.** In many countries, however, commercial harvest statistics will only partly account for wood removals. Significant quantities may be removed from forests on an informal basis (i.e., they are never accounted for in commercial statistics). In these cases FAO statistics of fuelwood consumption can be used to supplement the commercial harvest data. Any wood which was extracted from cleared forests and used for fuel will already have been accounted for in the forest and grassland conversion calculations above. This amount should be subtracted from total wood consumed directly for fuel and for traditional charcoal making, to determine the amount which must have come from remaining managed forests. The result of this calculation can then be combined with any commercial harvest amounts to produce a total amount of biomass lost from managed forests. There is an implicit assumption that slash is not accumulating. The instantaneous release of CO 2 from the current year's slash that is explicit in Equation 1 (2) is a simple mathematical device to treat slash oxidation from previous years under the assumption that the slash pool is not changing. The expansion ratio for slash in Equation 1 (2) could be modified to address the destruction of belowground biomass left after harvest. Treatment of carbon released from belowground biomass (e.g., roots) is discussed in the “Refinements in Calculations” section of this chapter.

13 Volume to mass conversions and expansion factors are taken from Brown et al., 1989 which reports on tropical forests. However, the values are in the range of those reported by ECE/FAO (1992) for temperate forests.

14 If significant amounts of non-commercial biomass (slash) are burned on site during harvest, then emissions from this burning should be treated as described for burning associated with forest or grassland conversion in the next section. A portion of the burned carbon would be stored as unburned charcoal, and non-CO 2 gases should also be calculated.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.23 The amount of biomass removed from forests and other woody biomass stocks in the inventory year should be subtracted from the annual growth in these stocks for the same year to arrive at the annual change in biomass stocks, positive or negative [Equation 1 (3)]. This result should be converted to a change in C (using the general default value of 0.50 t C/t dm, if necessary), and to CO 2 (using the ratio 44/12). A positive value for CO 2 in stocks is a CO 2 removal from the atmosphere while a negative value is an emission. For reporting purposes, the sign should be changed to conform to the convention that emissions are positive and removals are negative (i.e., negative emissions).



### 5.2.3 Forest and Grassland Conversion

CO 2 release This category includes conversion of existing forests and natural grasslands to other land uses, such as agriculture. The calculation of carbon fluxes due to forest and grassland conversion is in many ways the most complex of the emissions inventory components. Responses of biological systems vary over different time-scales e.g., biomass burning occurs at less than one year scale, decomposition of wood at the decade scale, and loss of soil carbon at several decades scale. Thus, it is necessary to consider forest clearing activity over three different time-scales and to sum the results to estimate the total flux in the current year. Also, as with all categories of forest management and land-use change activity, it is necessary to determine net CO 2 flux. Forests can be cleared to convert land to a wide variety of other uses, including agriculture, highways, urban development, etc. 15 In all cases there is a net carbon release to the atmosphere which should be accounted for in this calculation. The predominant current cause of forest clearing is conversion to pasture and cropland in the tropics. This is accomplished by an initial cutting of undergrowth and felling of trees. The biomass may then be combusted in a series of on-site burns or taken off site to be burned as fuel, or perhaps used for forest products. A portion of the biomass remaining on site as slash is not completely combusted and remains on the ground where it decomposes slowly. 16 Some of the decay of remaining carbon left on the ground is probably accomplished by termites, which produce both CO 2 and CH 4 . 17 However, the CH 4 release from cleared, unburned biomass is very difficult to quantify and is ignored for purposes of the basic calculation, where all of the carbon in biomass which decays is assumed to be released as CO 2 . Of the portion burned on site, a small fraction of the carbon remains as charcoal, which resists decay for well over 100 years or more. There is a great deal of uncertainty

15 Conversion of tropical forests to pasture and cropland accounts for the largest share of global forest clearing and resulting CO 2 emissions. The discussion and default information focus on this case, as it is most important that national inventories account for the largest contributions to emissions first. Forest clearing for other purposes (e.g., urban development) should also be accounted for to the extent possible. As less default information is provided for these cases, this will require national experts to provide input data.

16 Decomposition rates of woody slash generally depend on several factors including humidity, temperature, and chemical composition (e.g., nutrient content and secondary chemicals).

17 This issue is discussed in the section on possible refinements to the methodology.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual about the fraction of carbon which remains unburned in charcoal under these conditions and also about the ultimate fate of this charcoal. 18 The remainder is released instantaneously to the atmosphere. For biomass removed for fuelwood, the fate is very similar. A small fraction of the carbon remains in unburned charcoal which effectively provides long term storage, while the majority of the carbon is released to the atmosphere. For conversion of grasslands to crop or pasture lands, the default assumption is that there is no change in aboveground biomass between the pre-conversion natural grassland and the post-conversion crops or pasture. This assumption can be varied if there are locally available data that show a net change (see Box 7). Forest and grassland conversion also results in CO 2 emissions through soil disturbance, particularly when the conversion is to cultivated or tilled lands. When forests are converted to croplands, a fraction of the soil carbon may be released as CO 2 , primarily through oxidation of organic matter. This can be a long term process which continues for many years after the change in land use occurs. The calculations in Section 5.3 allow for estimation of loss in soil carbon due to land conversions.
Calculations
Emissions of CO 2 due to forest and grassland conversions are calculated through a sequence of steps treating:

• the net change in aboveground biomass carbon

• the portion of this change that is burned in the first year (either on- or off-site) versus the amount left to decay over a longer time period

• for the burned portion, loss to the atmosphere versus long-term storage in charcoal

• current emissions from decay of biomass cleared over the previous decade

• current releases of carbon from soils due to conversions (decomposition of soil organic matter).

18 The portion of burned carbon that remains on the ground as charcoal is highly uncertain. Measurements following burning of a forest for conversion to pasture indicate that 2.6 per cent of the pre-burn aboveground carbon, or 8.5 per cent of the burned carbon, is converted to charcoal (Fearnside et al., 1990a). According to Fearnside et al. (1990b), pastures are typically burned two to three times over about a 10-year period. Under such a scenario, the latter burns probably result in combustion of some of the charcoal formed during the first burn and formation of additional charcoal. Fearnside et al. (1990b) estimate that about 4.6 percent of the pre-burn aboveground carbon, or 10.1 percent of the burned carbon, is converted to charcoal under this scenario. Based on results of observations in the Brazilian Amazon (Fearnside et al., 1990a) and in a Florida pine forest (Comery, 1981), Crutzen and Andreae (1990) adopt charcoal values of 5 percent of the pre-burn aboveground carbon and 10 percent of the burned carbon for clearing in the tropics. Recent estimates of charcoal produced suggest that these values may be too high and will be re-assessed in future revisions to the Guidelines.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.25 B OX 7 A BOVEGROUND B IOMASS IN G RASSLANDS Conversion of a grassland to cultivated land may result in net CO 2 emissions to the atmosphere due to soil disturbance and resultant oxidation of soil carbon. In the simple default calculations, it is assumed that there is no net reduction in standing biomass because aboveground biomass densities of grasslands are approximately the same as that of croplands andpasture. Therefore any changes in this aboveground pool due to the landuse change are likely to be generally small in comparison with other changes in carbon stocks in terrestrial systems. Consequently, changes in aboveground biomass are ignored in the basic calculation. As with all default assumptions, users are encouraged to vary this one if they believe it is inaccurate for their conditions. Some grasslands can contain significantly more or less standing biomass than the default estimate of 10 tonnes dry matter/hectare for grasslands. If national experts have data locally available and differences are significant, these values should be used. In this case, the assumption of no net change in aboveground biomass would not be valid. The net change in aboveground biomass in this situation would be determined with exactly the same procedure as used in the forest clearing

case.

Net change in aboveground biomass First, the amount of aboveground biomass that is cleared in the emissions Inventory Year 19 is calculated by multiplying the annual forest area (or savannas, grasslands, etc., if appropriate) converted to pasture or cropland or other land uses by the net change in aboveground biomass. This calculation is carried out for each relevant forest/grassland type and, if appropriate, by region within a country. 20 The net change is the difference between the density (t dm/ha) of aboveground biomass on that forest/grassland prior to conversion, and the density of aboveground living biomass (t dm/ha) remaining as living vegetation, after clearing. The after clearing value includes the biomass that regrows on the land in the year after conversion and any original biomass which was not completely cleared. Tables 5-4 to 5-6 provide a range of values for aboveground biomass in forests prior to clearing, which can be used as default data if more appropriate and accurate data are not

19 For simplicity of explanation, the discussion refers to the Inventory Year as though data for a single year were the desired input. However, as noted in the overview, for land use and forestry emissions estimates, it is recommended that data averaged over several years be used in place of annual data. E.g., forest inventories are often done at five or ten year periods - this would then be the period over which data would be averaged to obtain the annual flux.

20 Defining regions will require balancing data availability, biological and land-use heterogeneity, and practical considerations such as the available time and effort. Furthermore, developing adequate land use and land-use change data is a central issue. In the case of land clearing, these data would likely be obtained from a combination of departments of land management, agriculture, and forestry. These data will come at a variety of scales in time and space, and producing consistent records will be a challenging task to all countries. In time, new internationally-based remote sensing programmes could greatly facilitate this task; this is discussed in the technical appendix.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual available in a given country. 21 For aboveground biomass after clearing, it is necessary to account for any vegetation (i.e., crops, pasture, or forest) that replaces the vegetation that was cleared. A reasonable figure for crops or pasture is 10 tonnes of dry biomass per hectare (Houghton et al., 1987; see also Box 7). Higher estimates of biomass of replacement crops is expected when perennials plants such as coffee, tea, cocoa, coconut, etc., are established. Where replacement by perennials is common (e.g., in many Asian countries), every effort should be made to obtain representative values. The recommended default assumption is that all of the original aboveground biomass is destroyed during clearing. If locally available data indicate that some fraction of the original biomass is left living after clearing, this should be added to the after clearing value.

T ABLE 5-4 A VERAGE A BOVEGROUND B IOMASS E STIMATES

FOR T ROPICAL F ORESTS BY C LIMATIC Z ONE ( TONNES D M /H A ) Tropical forests

Wet Moist with short dry season Moist with long dry

season Dry Montane Moist Montane Dry

R > 2000 2000>R>1000 R<1000 R>1000 R<1000
Africa 300 140 60-90 a 20-55 a 105 40
Asia :
Continental
Insular 225
275 185
175 100
no data 75
little to no forest exists 190
255 no data
no forest exists

America 295 no data 90 105 150 50 R= annual rainfall in mm/yr Sources: Estimates were derived from a model in a geographic information system and calibrated with reliable forest inventory data (Iverson et al., 1994) or from direct measurements ( a P. Frost, pers. comm., 1996). Multi-date inventories were brought to a common year of about 1980. The estimates do not distinguish between primary or secondary forests but represent values averaged over the whole forested area in a given climatic zone in a given tropical region. These average values can include forests in all successional states, from mature or undisturbed to young secondary. Additional country-specific biomass estimates are presented in Table 5-5. Data are from Brown et. al. (1993) for Asia; Brown and Gaston (1995) for Africa; and S. Brown (pers. comm., 1995) for America. REGIONAL DEFAULT ESTIMATES FOR BIOMASS DENSITY MAY BE USED AS AN INITIAL STARTING POINT OR FOR COMPARISON PURPOSES. HOWEVER, IN ANY COUNTRY FOR WHICH FOREST CONVERSION OR REGROWTH IS A SIGNIFICANT SOURCE OR SINK, LOCAL EXPERTS AND MEASUREMENTS SHOULD BE CONSULTED TO DEVELOP MORE ACCURATE VALUES REFLECTING LOCAL CONDITIONS.

21 As in the case of land-use data, developing appropriate biomass data is a challenging task. In theory, it can be obtained directly by destructive sampling but this is unrealistic for adequate coverage for even small countries. An alternative approach is to use inventory data where one exploits volumetric data on merchantable timber and uses a sequence of expansion factors to convert this to total stemwood, total above ground biomass, and total biomass. See the references to Tables 5-3 and 5-4.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.27 T ABLE 5-5 A BOVEGROUND B IOMASS E STIMATES FOR V ARIOUS T ROPICAL F OREST T YPES BY C OUNTRY ( TONNES DM / HA ) Country Forest Type Climatic Zone Aboveground Biomass
Africa
Benin Closed forest Tree savanna Dry Dry 175 96

Botswana a Mixed tree savanna Dry-long dry season 19

Burkina Faso (National) Degraded tree

savanna Dry- long dry season 20

Cameroon Primary Very moist 310
Gambia (National) Gallery forest Closed woodland Open woodland Tree savanna Moist- dry season Dry Dry Dry 140 97 50 28 Ghana Closed forest Moist-short dry season 395
Guinea (National) Mixed; closed Open, secondary Moist-long & short dry 135

Mozambique Dense forest Dense forest Dense forest Moist- long dry Moist- long dry Dry- long dry season 120 130 70

Zambia a Woodland-miombo Woodland-miombo Moist-long dry season Dry-long dry season 91 81

Zimbabwe a Woodland-miombo Dry-long dry season 29
Asia Bangladesh Closed -large crowns Closed -small crowns Disturbed closed Disturbed open Very moist Very moist Very moist Very moist 206-210 150 190 85
Cambodia Dense Semi-dense Secondary Open Open Well to poorly stocked Evergreen Deciduous Moist-short dry Moist-short dry Moist-short dry Moist-short dry Moist-long dry Moist-long dry
Moist-long dry 295 370 190 160 70 100-155

120

India High to low volume Closed Forest fallow Dry
Dry 44-81

16

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.28 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-5 ( CONT .) A BOVEGROUND B IOMASS E STIMATES FOR V ARIOUS T ROPICAL F OREST T YPES BY C OUNTRY ( TONNES DM / HA ) Country Forest Type Climatic Zone Aboveground Biomass
Asia - (cont) Malaysia-Peninsular (National) Superior/moderate hill Poor hill Upper hill Disturbed hill Logged hill Forest fallow Freshwater swamp Disturbed freshwater swamp Logged freshwater swamp Very moist Very moist Very moist Very moist Very moist Very moist Very moist Very moist Very moist 245-310 180 275 200 180 140 220 285 185 Malaysia- Sarawak Mixed dipterocarps-dense stocking, flat to undulating terrain Mixed dipterocarps-dense stocking, mountainous Mixed dipterocarps- medium stocking, flat to mountainous Very moist

Very moist
Very moist 325-385

330-405

280-330

Myanmar Evergreen Mixed deciduous Indaing forest Moist-short dry Moist-short dry Moist-short dry 60-200 45-135

10-65 Philippines Old-growth dipterocarp Logged dipterocarp Very moist Very moist 370-520 300-370 Sri Lanka Evergreen-high yield Evergreen-medium yield Evergreen-low yield Evergreen-logged Secondary Very moist Very moist Very moist Very moist Very moist 435-530 365-470 190-400

255 280 Thailand Degraded dry evergreen Moist-long dry 85
America - All forests are located in the wet/very moist climatic zone except where indicated.
Bolivia Closed forest 230
Brazil Closed forest 315
Ecuador Closed forest 182 French Guyana Closed forest Riparian forest Savanna forest 309 275 205
Guatemala Closed forest 242

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.29 T ABLE 5-5 ( CONT .) A BOVEGROUND B IOMASS E STIMATES FOR V ARIOUS T ROPICAL F OREST T YPES BY C OUNTRY ( TONNES DM / HA ) Country Forest Type Climatic Zone Aboveground Biomass

America - (cont.) All forests are located in the wet/very moist climatic zone except where indicated.

Guyana Closed forest Logged forest Wallaba forest-seasonal Mixed forest Low mixed forest Liana forest Wallaba forest Wallaba forest on white sands 254 190 145 275 192 125 148 405 Nicaragua Orifino forest Lowland mixed Mature forest Secondary 240 235 240 183 Panama High density-mixed Low density-mixed Campnosperma forest -high density Campnosperma forest -low density High density-mixed Low density-mixed 239-366 169-245

860 470 186-252 118-143 Peru Primary Lightly logged Heavily logged Late secondary Young secondary Flooded secondary Low forest 210 192 125 140 20 195 155 Surinam Upland forest Small crown-upland Savanna forest Riparian forest Liana forest Wallaba forest 255 136 195 217 120 250 Venezuela Semi-deciduous-dry Closed forest 78 230
Source : All biomass estimates were derived from either reliable forest inventory data for subnational to national forest areas (sources of inventories and details of methods used to convert to biomass are given in Brown, (1996) or from direct measurements, ( a P. Frost, pers. comm., 1996).

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.30 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-6 D RY M ATTER IN A BOVEGROUND B IOMASS IN T EMPERATE AND B OREAL F ORESTS ( TONNES DM / HA ) Temperate Forests Coniferous 220 - 295
Broadleaf 175 - 250
Boreal Forests Mixed broadleaf/coniferous 40 - 87
Coniferous 22 - 113

Forest-tundra 8 - 20
Source: Temperate forest estimates from Whittaker and Likens (1973) and Houghton et al. (1983). Total biomass estimates were converted to aboveground biomass by multiplying by 0.83 (Leith and Whittaker, 1975). Boreal forests biomass estimates are from Bazilevich, (1993); Finnish Forest Research Institute, (1995); Kokorin and Nazarov, (1995a); and Isaev et al. (1993). Alternative estimates of aboveground biomass per hectare, by country, for coniferous species and non-coniferous species, can be derived using statistics provided in ECE/FAO (1992). Most temperate and boreal countries have their own national estimates of biomass densities for forests which should be used. These default values are very rough estimates and are provided for comparison only.

Immediate emissions from burning
The biomass that is cleared has one of three immediate fates: 1. a portion may be burned on site; 2. a portion may be removed from the conversion site and used as fuelwood or for products; 3. a portion is converted to slash, and decays on site to CO 2 over a decade or so. Some estimates in the literature suggest that a global average of about 50 per cent of the cleared biomass is burned in the first year with the remaining 50 per cent left to decay (e.g., Houghton, 1991; and Crutzen and Andreae, 1990). This value could be used as a default for first order calculations if the user does not have access to more appropriate local information. It is important to recognise that this average is dominated by practices in tropical America which has the largest current rate of deforestation. There are certainly wide variations in burning practices between and within regions. It is highly recommended that, for final inventories, users provide their own values reflecting practices and burning conditions in the regions of interest, rather than using the global default value. To calculate the gross amount of carbon released in the current year to the atmosphere it is necessary to consider the burned portions and the decaying portion over different time horizons. When a forest is cleared for pasture or agriculture use not all trees are cut; some of them are left standing live. The carbon in these remaining trees needs to be considered in emission calculations.
To estimate the CO 2 released by the burning of cleared aboveground vegetation, estimate (a) the fraction of the affected biomass that is subjected to burning (the remaining, disturbed biomass is slash) and (b) the fraction of the burned biomass that is oxidised. The fraction of burned biomass which does not oxidise remains as charcoal. The amount of biomass oxidised is converted to carbon units to estimate the carbon flux

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.31 from burning. 22 A reasonable average for converting from dry biomass to carbon content is to multiply dry biomass by 0.50. 23 Of the portion of cleared biomass which is burned, some of this may be burned in the field to facilitate clearing, and some may be removed and used as fuel. The portion which is burned in the field is used subsequently for calculating the non-CO 2 trace gas emissions from open burning of cleared biomass, in the next section. The amount removed for fuel is important for calculations of fuel wood extracted from forest and other woody biomass stocks as described earlier in these basic calculations. Emissions from decay The aboveground biomass which remained on site but was not burned is estimated to oxidise in roughly a decade, and this historical release associated with land clearing must be considered. The 10-year period is a recommended default value, as a reasonable historical horizon in light of the twin realities of data availability and biological dynamics (see Houghton, 1991; and Crutzen and Andreae, 1990). This can be varied if the user has data or a strong rationale to suggest that a longer or shorter average decay time is more representative of local conditions. The "committed" flux calculation simply accounts for the current oxidising of material left unburned during the specified historical decay period. The decay phenomenon can be simply characterised for emissions estimation purposes. Each year, some portion of the cleared aboveground biomass is left as slash, and we assume that 10 per cent of this decomposes each year, based on the default 10 year period. Therefore, the total carbon being released to the atmosphere in the Inventory Year is a function of the land clearing rate for each of the past 10 years, and the portion of the aboveground carbon remaining on site but not combusted each year. The current year emissions from decay of biomass cleared in a historical year would be 10 per cent of the total decay. The total current emissions from decay of historically cleared biomass would then be the sum of the current estimated emissions from biomass cleared in each of the ten historical years. To simplify the calculations, the methodology uses decade average values for the land clearing and portion left to decay. Working with average values, one would divide the total emissions from decay by 10 to get the contribution of one "average" historical year's clearing to current emissions, then multiply by 10 to account for ten historical years' clearing which could be expected to affect current emissions. Obviously the division by 10 and multiplication by 10 cancel each other and can be ignored. Therefore, the flux in the Inventory Year from aboveground vegetation decay due to current and historical land clearing is simply expressed in Equation 2.

22 As discussed elsewhere in these Guidelines this method counts the carbon actually emitted as CO and CH 4 as though it were carbon dioxide. Later in this chapter, these emissions of CO and CH 4 will also be estimated separately.

23 The range most cited is 0.43-0.58; hence it is suggested that 0.5 is the appropriate default assumption.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual E QUATION 2 average annual land clearing over the period (default of 10 years)

x the average quantity of aboveground dry biomass per hectare remaining on site as slash but not burned (either oxidised or converted to charcoal)

x carbon content of dry biomass

= flux in the Inventory Year from historical land clearing of the aboveground vegetation

Soil carbon release For calculating the annual CO 2 flux associated with the loss of soil organic carbon following forest clearing or grassland conversion, the methodology is described in Section 5.3 for all types of transitions, and will not be described further here. Burning of Forests: Non-CO 2 Trace gases Where there is open burning associated with forest clearing (or other land-use change), it is important to estimate the emissions of methane (CH 4 ), carbon monoxide (CO), nitrous oxide (N 2 O), and oxides of nitrogen (NO x , i.e., NO and NO 2 ). The approach is essentially the same as that used for non-CO 2 trace gases for all burning of unprocessed biomass, including savanna burning and field burning of crop residues. For these activities there is a common approach in the proposed methodology in that crude estimates of trace gas emissions can be based on ratios to the total carbon released by burning. The carbon trace gas releases (CH 4 and CO) are treated as direct ratios to total carbon released. To handle nitrogen trace gases, ratios of nitrogen to carbon in biomass are used to derive total nitrogen released from burning, and then emissions of N 2 O and NO x are based on ratios to total nitrogen release. Table 5-7 provides suggested default values for trace gas emission ratios. 24 These are presented with ranges which emphasise their uncertainty. However, the basic calculation methodology requires that users select a best estimate value. 25

24 The emission ratios used in this section are derived from Crutzen and Andreae, (1990), Delmas, (1993) and Lacaux et al., (1993). They are based on measurements in a wide variety of fires, including forest and savanna fires in the tropics and laboratory fires using grasses and agricultural wastes as fuel. Research will need to be conducted in the future to determine if more specific emission ratios, e.g., specific to forest fires, can be obtained. Also, emission ratios vary significantly between the flaming and smouldering phases of a fire. CO 2 , N 2 O, and NO x are mainly emitted in the flaming stage, while CH 4 and CO are mainly emitted during the smouldering stage (Lobert et al., 1990). The relative importance of these two stages will vary between fires in different ecosystems and under different climatic conditions, and so the emission ratios will vary. As inventory methodologies are refined, emission ratios should be chosen to represent as closely as possible the ecosystem type being burned, as well as the characteristics of the fire.

25 Emissions inventory developers are encouraged to provide estimates of uncertainty along with these best estimate values where possible, or to provide some expression of

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.33 All of the crude biomass burning calculations have two steps: 1) estimating total carbon released, and 2) applying emission ratios to estimate emissions of the non-CO 2 trace gases. In the case of burning of cleared forests (and other land conversion if appropriate), step 1 has been carried out in the previous section which included the estimation of carbon emissions from the portion of biomass from conversions which is burned on site in the Inventory Year. The total carbon release from this on site burning (not including any carbon released from decay or soils) provides the basis for the Inventory Year release of non-CO 2 trace gases. To complete the calculations, it is necessary only to add step 2 of the calculation – the release of non-CO 2 trace gases from current burning.

T ABLE 5-7 E MISSION R ATIOS FOR O PEN B URNING OF C LEARED F ORESTS Compound Ratios
CH 4 CO
N 2 O
NO x 0.012 (0.009 - 0.015) a 0.06 (0.04 - 0.08) b
0.007 (0.005 - 0.009) c 0.121 (0.094 - 0.148) c

Sources: a Delmas, 1993 b Lacaux et al., 1993
c Crutzen and Andreae, 1990 Note: Ratios for carbon compounds, i.e., CH 4 and CO, are mass of carbon compound released (in units of C) relative to mass of total carbon released from burning. Those for the nitrogen compounds are expressed as the ratios of emission (in units of N) relative to total nitrogen released from the fuel.
Once the total carbon released from on site burning of cleared biomass has been estimated, the emissions of CH 4 , CO, N 2 O, and NO x can be calculated (Crutzen and Andreae, 1990). The total carbon released due to burning is multiplied by the emission ratios of CH 4 and CO relative to emissions of total carbon to yield total emissions of CH 4 and CO (each expressed in units of C). The emissions of CH 4 and CO are multiplied by 16/12 and 28/12, respectively, to convert to full molecular weights.
To calculate emissions of N 2 O and NO x , first the total carbon released is multiplied by the estimated N/C ratio of the fuel by weight (0.01 is a general default value for this category of fuel (Crutzen and Andreae, 1990)) to yield the total amount of nitrogen (N) released. The total N released is then multiplied by the ratios of emissions of N 2 O and NO x relative to the total N released from the fuel to yield emissions of N 2 O and NO x (expressed in units of N). To convert to full molecular weights, the emissions of N 2 O and NO x are multiplied by 44/28 and 46/14, respectively. 26 The trace gas emissions from burning calculation are summarised as follows:

• CH 4 Emissions = (carbon released) x (emission ratio) x 16/12

the level of confidence associated with various point estimates provided in the inventory. Procedures for reporting this uncertainty or confidence information are discussed in the Reporting Instructions

. 26 The molecular weight ratios given above for the emitted gases are with respect to the weight of nitrogen in the molecule. Thus for N 2 O the ratio is 44/28 and for NO x it is 46/14. NO 2 has been used as the reference molecule for NO x .

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.34 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • CO Emissions = (carbon released) x (emission ratio) x 28/12

• N 2 O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28

• NO x Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 46/14



### 5.2.4 Abandonment of Managed Lands If managed lands, e.g., croplands and pastures, are abandoned, carbon may re-accumulate on the land and in the soil. In this section, only the carbon accumulation in biomass is considered; accumulation in the soil, as organic carbon, is dealt with in Section 5.3. The response of these converted systems to abandonment depends upon a complex suite of issues including soil type, length of time in pasture or cultivation, and the type of original ecosystem. It may be that some of the abandoned agricultural lands are too infertile, saline, or eroded for regrowth to occur. In this case, either the land remains in its current state or it may further degrade and lose additional organic material (i.e., carbon in the biomass and the soils). Therefore, to calculate changes in carbon flux from this activity, the area abandoned should first be split into parts: lands that re-accumulate carbon naturally, and those that do not or perhaps even continue to degrade. In the basic calculation, only those that begin to return to an approximation of their previous natural state are considered. Those that remain constant with respect to carbon flux can be ignored. Likewise, the CO 2 flux to the atmosphere for those lands that continue to degrade is likely to be small on a global basis and hence is ignored in the initial application of basic calculations. In some countries, abandoned lands which degrade may be a significant problem and could be an important source of CO 2 emissions. Where lands continue to degrade, both aboveground biomass and soil carbon may decline rapidly, e.g., due to erosion. However, carbon in eroded soil could be re-deposited in rivers, lakes, or other lands downstream. For countries which have significant areas of such lands this issue should be considered in a more refined calculation. Abandoned lands must be evaluated in the context of the various natural ecosystems originally occupying them. In addition, the effect of previous patterns of abandonment should be considered while recognising the desire for simplicity and practicality. The process of recovery of aboveground biomass generally is slower than the human-induced oxidation of biomass. With this in mind and in consideration of possible data sources it is recommended that abandoned lands be evaluated in two time horizons. A twenty year historical time horizon is suggested to capture the more rapid growth expected after abandonment. A second time period – from 20 years after abandonment up to roughly 100 years – may be considered if data are available. 27 The calculation, by original ecosystem is straightforward. To estimate gains in biomass carbon stocks the total area abandoned (total over the previous 20 years including the Inventory Year) is multiplied by the average annual uptake of carbon in the aboveground biomass. If landuse data are available to support calculations over a longer time horizon, national experts may want to consider adding a pool of forests and grasslands that are

27 It is clear that most forest systems will take longer than 100 years to return to the level of biomass contained in an undisturbed state. If data are available, it is possible to calculate carbon sinks from regrowth on lands abandoned more than 100 years prior to the Inventory Year. As a practical matter, however, it is unlikely that such data will be available in most countries, or that the magnitude of annual carbon accumulation would be large. Therefore, it is not generally recommended to carry these calculations back more than the specified period of 100 years.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.35 regrowing from abandonment that occurred more than 20 years ago. The growth rates of aboveground biomass in these forests would be slower than those of forests regrowing from abandonment that occurred less than 20 years ago. The same calculations can be repeated for lands abandoned for more than 20 years and up to about 100 years prior to the Inventory Year. Table 5-2 presents estimates of average annual aboveground biomass accumulation in vegetation in various regrowing forest ecosystems following abandonment of cultivated land or pasture 28 . These general growth rates, averaged over large regions and many specific ecosystem types, should be considered only approximations as applied to the particular lands regrowing in a given region or country. If more accurate data on these growth rates are locally available, they should be used. If lands are regenerating to grassland, then the default assumption is that no significant changes in aboveground biomass occur. This can be varied based on locally available data. Accumulation of aboveground dry biomass can be converted to carbon using a general default conversion value for biomass of 0.5 t C/t dm.



## 5.3 CO 2 

## Emissions and Uptake by Soils from Land-Use Change and Management

5.3.1 Overview The principal sources/sinks of CO 2 in soils are associated with changes in the amount of organic carbon stored in soils. Release of CO 2 also occurs from inorganic sources, either from naturally occurring carbonate minerals or from applied lime. CO 2 flux from weathering of native carbonate minerals is not a significant source in most agricultural soils, with the possible exception of irrigated arid and semi-arid soils (Schlesinger, 1986). This section focuses on a methodology to estimate net fluxes of CO 2 due to changes in soil organic carbon stocks. CO 2 releases from liming applications are also dealt with. Fundamentally, changes in organic carbon content are a function of the balance between inputs to soil of photosynthetically-fixed carbon and losses of soil carbon via decomposition. Soil erosion can also result in the loss (or gain) of carbon locally, but the net effect of erosion on carbon losses as CO 2 for large areas on a national scale is unclear and demands separate consideration. For soils, both the quantity and quality of organic matter inputs and the rate of decomposition of soil organic carbon will be determined by the interaction of climate, soil and landuse/management (including land-use history). In native ecosystems, climate and soil conditions are the primary determinants of the carbon balance, because they control both production and decomposition rates. In agricultural systems, landuse and management act to modify both the input of organic matter via residue production, crop selection, fertilisation, harvest procedures, residue management and the rate of decomposition (by modifying microclimate and soil conditions through crop selection, soil tillage, mulching, fertilisation, irrigation and liming).

28 Values given in Table 5-2 assume linear regrowth of aboveground biomass in each of the two time periods (0-20 years and 21-100 years). In reality, as shown in Brown and Lugo (1990), the regrowth in tropical forests is closer to a logistic function. The calculation could be improved by breaking the 20 year period into finer segments, assuming availability of data, to determine a weighted average.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.36 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Estimates of CO 2 fluxes can be made in two ways: (1) by direct measurement of CO 2 flux, and (2) indirectly, through balance estimates of the net change in carbon stocks of the soil.
Direct estimates of CO 2 influx, through photosynthesis, and CO 2 efflux, through decomposition and respiration, are difficult to obtain for several reasons: both exhibit large diurnal, short-term and seasonal variations requiring near continuous measurements to derive annual estimates; different components of the overall fluxes operate on very different time scales (e.g., plant respiration vs. mineralisation of recalcitrant organic matter); and the magnitudes of influxes and effluxes of CO 2 are large relative to their difference. The most practical means of directly measuring net CO 2 fluxes for wholeecosystems is by using micrometeorological techniques, which are costly and timeconsuming. Such measurements for agricultural ecosystems are scarce.
Balance estimates of CO 2 emissions from soils due to land use are based primarily on field studies of changes in soil carbon occurring over several years, from repeated measures of soil carbon in experimental plots or in sites representing a chronosequence, e.g., sites that had experienced a change in land use or management at different times prior to sampling. Such information, coupled with laboratory experiments, has been used to develop statistical and simulation models of soil carbon change as a function of climate, soil and land-use and management factors. At the present time, we deem a carbon balance-based approach as the most feasible alternative.



### 5 . 3 . 2 D e s c r i p t i o n o f a C a r b o n B a l a n c e Methodology The most rigorous approach to estimating net changes in soil carbon would be to calculate inputs and outputs of carbon for a particular ecosystem and from the difference calculate the annual net change in carbon storage. To integrate the various factors determining the quantity and quality of carbon entering the soil as well as the decomposition rates of soil organic carbon, a simulation model can be used. This kind of an approach has recently been used at large spatial scales (i.e., regional and country-level) to estimate changes in carbon stocks in agricultural soils in the United States (Donigian et al., 1994, Lee et al., 1993, Paustian et al., submitted) and Canada (Smith et al., in press, Dumanski et al., submitted). Similar applications have been made at regional and global scales to evaluate potential responses of soil carbon to global climate change (Jenkinson et al., 1991, King et al., 1996, Potter et al., 1993, VEMAP, 1996). However, these applications have used relatively complex research models, requiring large numbers of simulation runs and sophisticated computer resources such as geographic information systems to manage large amounts of input data. Moreover, the models have not been extensively tested for many agricultural systems, particularly in the tropics. Thus, it is our opinion that a "model-based" approach would not be feasible at the present time. However, we feel this kind of an approach is a priority for further development and could be incorporated in future inventory methodologies. The current method employs an accounting approach based on estimating soil carbon stocks and areas for major categories of agricultural land-use/management systems. A similar approach has been used in an assessment of the carbon balance for the agricultural sector in the former Soviet Union (Kolchugina and Vinson, 1996). The fundamental principle in this approach is that after many years under a particular form of land use, soil carbon levels tend towards an equilibrium state where carbon inputs from plant residues and losses of carbon through decomposition roughly balance. A new steady state balance is more rapidly reached in hot humid climates but the time to equilibrium can be much slower in cool and/or dry climates. Hence net fluxes of CO 2 can be associated with

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.37 changes in soil carbon stocks as a unit area of land transitions from one form of land use and management to another. Since climate and soil type are major determinants of the kinds of management systems employed, as well as the potential stocks of soil carbon and their responses to management, the inventory approach is based on a classification according to eight major climate regions and six major soil types.



### 5 . 3 . 3 C l i m a t e C a t e g o r i e s Eight broad climatic regions are defined for inventory purposes. Climate will have an overriding effect on land use, management and cropping practices and a significant effect on soil carbon levels. Major soil taxonomic groups will to some degree co-vary with climate regions. The eight climate regions chosen are: 1) cold temperate, dry, 2) cold temperate, moist, 3) warm temperate, dry, 4) warm temperate, moist, 5) tropical, dry 6) tropical moist (with long, dry season), 7) tropical moist (with short, dry season), and 8) tropical, wet. These regions were chosen largely on the basis of major constraints on crops and cropping practices. The cold thermal regime in the temperate zone represents areas with short growing seasons dominated by spring-sown cereals (e.g., wheat, barley, rye), root crops and perennial forages. The warm temperate zone is characterised by warmer summers and milder winters, which are favourable for over-wintering cereals (e.g., winter wheat) and for heat-demanding crops such as maize and soybeans. In the tropical zone, low temperatures are not generally a constraint on crop growth. The moisture regimes are intended to coincide with major differences in management as a function of moisture availability. In the dry temperate zone, moisture limits the potential for continuous cropping, thus summer fallowing is widespread and drought-tolerant crops are required. Irrigation, where available, is an important management practice. In the temperate, moist zone, precipitation is sufficient for cropping every year, summer fallowing is not generally practised and irrigation is mainly used for speciality crops. Moisture regimes in the tropics can be roughly classified by amounts of precipitation and length of the dry season. The dry tropics receive less than 1000 mm of precipitation, with a highly seasonal distribution and prolonged dry seasons. Agricultural systems are mainly extensive and subsistence-based, with grazing being an important component. Diverse and highly productive systems exist where irrigation is possible. The moist tropics are divided into two classes, both having annual precipitation in the range of 1000-2000 mm, but with classes having a prolonged dry season (> 5 months) versus short dry seasons (<5 months). Management systems become increasingly intensive as precipitation increases and is more evenly distributed. The wet tropics are classified as areas receiving >2000 mm per year. In this zone, production systems are mainly limited by fertility factors due to the preponderance of highly weathered soils.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.38 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5 . 3 . 4 S o i l C a t e g o r i e s A stratification of up to six major soil groups is proposed, based on major differences in their inherent carbon stocks and their response to management. The soil groups chosen

are:

T ABLE 5-8 S OIL T YPE C LASSIFICATIONS Soil Type Examples for major FAO soil taxonomic groups Examples for major USDA soil taxonomic groups High clay activity mineral soils Vertisols, Chernozems, Phaeozems, Luvisols Vertisols, Mollisols, high-base status Alfisols Low clay activity mineral soils Acrisols, Nitosols, Ferralsols Ultisols, Oxisols, acidic Alfisols Sandy soils Arenosols, sandy Regosols Psamments
Volcanic soils Andosols Andisols Aquic soils (wet soils) Gleysols Aquic suborders Organic soils Histosols Histosols
The strong effect of texture and clay mineralogy on organic matter contents has been well demonstrated in both temperate and tropical regions. Thus we distinguish four major soil groups according to these criteria. Soils with high clay activity are defined as having appreciable contents of high activity clays (e.g., 2:1 expandable clays such as montmorillonite) which are implicated in the long-term stabilisation of soil organic matter, particularly in many carbon-rich temperate soils (Martel and Paul, 1974). Soils with low clay activity are defined as soils with low activity clays (e.g., 1:1 non-expandable clays such as kaolinite and gibbsite and hydrous oxide clays of iron and aluminium) which have a much lower ability to stabilise organic matter (Trumbore, 1993) and faster responses to changes in the soil's carbon balance (Tiessen et al., 1994). Among these are included highly-weathered acid soils of subtropical and tropical regions. Sandy soils are defined as soils having less than 8 per cent clay and greater than 70 per cent sand, which generally have poor structural stability and a low capacity to stabilise carbon. These coarse-textured soils can occur in many of the major taxonomic soil classes. The Andosol soil group includes soils derived from volcanic materials, with allophane as the primary colloidal mineral. These soils are generally rich in carbon and highly fertile. The other two soil groups are distinguished on the basis of drainage and soil water status. Aquic soils are defined as mineral soils which have developed in poorly-drained, wet environments resulting in reduced decomposition rates and high organic matter contents. If artificially drained for agriculture they are subject to large losses of carbon. Histosols or peat soils are organic soils which form under water-saturated conditions where decomposition is greatly reduced. They can lose massive amounts of carbon over a sustained period upon drainage and cultivation.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.39

### 5.3.5 Soil Carbon Responses to AgriculturallyRelated Practices Land-use practices affect soil carbon stocks by modifying carbon inputs to soil as well as the decomposition rate of soil organic matter. The most important kinds of management practices, from the standpoint of their effects on carbon levels, are briefly described. 

### Land clearing from native vegetation The clearing of native vegetation (e.g., forests, savanna, grassland, wetlands) to agriculture almost invariably leads to a reduction in soil carbon as a result of decreased carbon inputs and enhanced decomposition from the disturbed soil. This has been well documented for temperate (Haas et al., 1957; Kononova, 1966; Dalal and Mayer, 1986; Paul and van Veen, 1978) as well as tropical (Nye and Greenland, 1960; Detwiler, 1986; Brown and Lugo, 1990) environments. Generally, the majority of the losses occur within the first few (< 10) years, particularly in the tropics (Detwiler, 1986), although slower declines in soil carbon can continue for many decades in organic matter rich soils, particularly in temperate regions (Tiessen et al., 1982; Rasmussen and Rohde, 1988). Erosion (by wind and water) can be a significant factor in carbon losses (and redistribution) locally, but the present inventory methodology does not account for effects of erosion on net CO 2 fluxes. Currently conversion of native vegetation to agricultural uses is occurring almost exclusively in the tropics. The magnitude of soil carbon decline can vary according to native vegetation, climate, soil type, land clearing method, and subsequent management. Several reviews of the literature (Schlesinger, 1986; Mann 1986; Detwiler 1986) show losses of 20-40 per cent or more of the original soil carbon stock following cultivation. Mann (1985) reported an average of 40 per cent lower carbon contents in cultivated vs. uncultivated soils (0-15 cm), from a sample of more than 300 temperate forest- and grassland-derived soils. Davidson and Ackerman (1993) analysed soil carbon inventories, from paired comparisons including both concentration and bulk density changes. They reported average reductions in soil carbon stocks of about 40 per cent for the surface (A) horizon and about 30 per cent for the top 30 cm. Clearing of native vegetation and conversion directly to pasture can result in lower carbon losses compared to clearing for cultivation. After initial decreases following forestclearance, soil carbon may even increase under pasture to levels comparable to preclearance levels within 10 years (Cerri et al., 1991; Eden et al., 1991; Lugo and Brown, 1993). With improved management (fertiliser and moderate grazing), high soil carbon levels may be sustainable over longer periods. However, unmanaged and overgrazed pastures are likely to decline in productivity and be subject to erosion and soil degradation, and subsequent decreases in soil carbon (Eden et al., 1991). 

### Conversion of cultivated land to perennial vegetation and shifting cultivation In most cases, land that has been cultivated for many years is depleted in organic matter relative to its original state. If converted to perennial vegetation, either through land abandonment and natural succession or as an active management decision (e.g., conversion to pasture, land set-asides for conservation practices), soil carbon levels generally increase. An exception is where the land has been degraded to the extent that productivity is permanently impaired in which case soil carbon levels may decline further. In the temperate zone, considerable areas of formerly cultivated lands have been abandoned or converted to grassland and forest, particularly in North America and

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.40 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Europe. Agricultural set-aside programmes have also been implemented in North America and Europe during recent years. The rate of increase and the level at which soil carbon is eventually stabilised on these lands will depend on productivity levels and soil conditions. Low rates of carbon accrual, 0.05-0.15 tonnes C/ha/yr over 25-50 year periods, have been reported for abandoned fields in semi-arid regions of the United States and Canada (Dormaar and Smoliak, 1985; Burke et al., 1995). For land set aside planted to perennial grasses and then left unmanaged, Paustian et al. (submitted) estimated rates of carbon increase ranging from 0.05-0.30 tonnes C/ha/yr, for semi-arid to sub-humid regions in the central United States. Higher rates of 0.25-0.50 tonnes C/ha/yr, averaged over an 80 year period, have been reported for abandoned fields under more mesic conditions, in the UK (Jenkinson , 1971a). For managed conversions to improved pastures, much higher rates of 0.75-1.0 tonnes C/ha/yr, for 15-20 years, have been achieved (Tyson et al., 1990; Haynes et al., 1991). Improved management of subtropical and tropical grasslands, with the incorporation of legumes, fertilisation and control of burning have been shown to increase soil carbon levels (Greenland, 1995). Recent data also suggest the potential for substantial C sequestration in tropical grasslands with the use of deep-rooting exotic grasses (Fisher et al., 1994). In the tropics, abandonment of land occurs as an integral phase of shifting cultivation. Shifting cultivation systems are characterised by a cycle of forest or bush clearing, followed by a few years of cropping and then abandonment to natural revegetation (fallow). Soil carbon is rapidly lost during the cropping phase and re-accumulates during fallow. In a study of six slash-and-burn chronosequences in Southern Cameroon, Woomer et al. (submitted) report the loss of 8 tonnes C/ha from soils (0-40 cm) within two years of forest conversion. Soil organic matter losses continued into the early fallow but the initial levels of 77 tonnes C/ha were re-established within the secondary forest after approximately 18 years. The mean soil carbon stocks maintained under shifting cultivation depend on the carbon lost during the cropping phase, the rate of accumulation under fallow and the length of fallow (Nye and Greenland, 1960). The length of the fallow period varies depending on climate, soil, vegetation type, land scarcity, and human population pressure. Recovery of soil carbon during the fallow phase can be rapid (Greenland and Nye, 1959). In North-east Brazil, Tiessen et al. (1992) reported recoveries to native soil carbon levels after about 10 years of bush fallow (following a 5-6 year cultivation cycle), by which time vegetation had not nearly attained native size or composition. Global estimates of carbon fluxes assume that 75 per cent (Houghton et al., 1987) to 90 per cent (Palm et al., 1986) of the original carbon stocks from deforested soils are recovered with forest succession. Abandonment which leads to the establishment of degraded or unimproved grasslands, such as the extensive areas of Imperata in South-east Asia, has been assumed to result in incomplete recovery (50 per cent) of original carbon stocks (Palm et al., 1986). However, other data suggest little difference between soil carbon inventories under Imperata vs. secondary forest (van Noordwijk et al., submitted). The discrepancies in data on the carbon content of Imperata grasslands may be partly due to differences in fire frequency. Imperata grasslands without fire build up reasonable stocks of soil carbon, but frequent burning may lead to serious soil degradation. The rapid invasion of Imperata into crop fields after forest conversion in the humid parts of Asia probably slows down further carbon losses, as compared to other areas where cultivation is continued. Lugo et al. (1986) found carbon stocks for pastures derived from abandoned cultivated lands in Puerto Rico to have similar or higher levels than in secondary forests. Differences in soil fertility are also important in that infertile soils are less prone to a build up of soil C upon abandonment. Large spatial variability in soils, varying sample depths, patchiness of vegetation regrowth and whether or not litter mats are included in soil C inventories make it difficult to compare field studies.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.41 Tillage Intensive soil tillage is recognised as a significant factor causing soil organic matter declines in cultivated soils. Intensive tillage, particularly with soil inversion (e.g., moldboard ploughing), enhances decomposition by releasing organic matter protected within soil aggregates and by increasing soil temperature. Reduced tillage, and particularly no-till practices, have been shown to promote higher levels of organic matter in many systems, where productivity and organic matter inputs are not adversely affected. Ananalysis of 28 paired comparisons from no-till versus full tillage treatments in 19 longterm experiments in Canada, Europe and the United States showed mean increases under no-till of 0-30 % C, with an average of about 10 per cent (Paustian et al., 1997). The duration of the experiments ranged from 5 to 20 years. These data were normalised to compare equivalent soil mass (to below the depth of ploughing ca. 20-30 cm), in order to eliminate effects of changes in bulk density and differences in organic matter distribution with depth. Experiments in the tropics have also demonstrated the potential for no-till systems to maintain higher soil carbon levels compared to conventional cultivation (Lal, 1986a). Reduced soil erosion and lower soil temperatures with surface mulches under no-till are particularly important attributes of no-till systems in the tropics (Lal, 1986a; Fernandes et al., submitted). Higher levels of carbon in no-till compared to cultivated treatments have been reported in a number of studies (Agboola, 1981; Jou and Lal, 1979; Aina, 1979). Jou and Lal (1979) reported nearly two times higher carbon contents in no-till vs. ploughed treatments in the top 10 cm (and no significant differences below 10 cm) under maize. Residue inputs, mulching, cover crops Maintenance of soil carbon depends on an adequate return of organic substrates which serve as the raw material for organic matter formation. In most agricultural systems, the primary sources of new carbon are crop residues, including roots, root exudates, and unharvested above-ground plant parts (e.g., straw or stover). The amount of carbon returned in the form of residues depends on the total biomass yield (including roots and related materials) and the proportion of that biomass which is exported from the field. Of the carbon applied to soil in the form of crop residues, about one third typically remains after one year and about one fifth remains after five years under temperate conditions (Jenkinson, 1971b). The remainder is returned to the atmosphere as CO 2 via biological decomposition. The rate of decomposition, and the proportion of carbon retained by soil, is influenced by climate, soil conditions, placement (surface versus buried), and the composition of the residue (Andrén et al., 1989). Some agricultural soils also receive significant inputs in the form of vegetation grown, at least in part, to provide additional carbon and other nutrients to the soil. For example, legumes are sometimes included in cropping systems as a 'green manure'. Similar benefits are derived from vegetative additions in 'alley-cropping' systems. A third source of carbon is various by-products which are applied as soil amendments. The most noteworthy of these are animal manure, but some soils also derive appreciable carbon inputs from sewage sludge and various industrial by-products. Although such additions can significantly increase soil carbon, gains in the soil must, from an atmospheric balance perspective, be compared with alternative uses of the resources. For example, if sewage sludge decomposes more rapidly in soil than in storage, the net effect will be an additional flux of carbon to the atmosphere. Management practices which promote greater rates of return of crop residues or other organic amendments will result in increased soil carbon stocks. According to current theories of soil organic matter dynamics, there should be a linear relationship between changes in carbon inputs and soil carbon levels (Greenland, 1995; Paustian et al., 1995);

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.42 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual this relationship is supported by a number of long-term field studies (Paustian et al., 1997). In temperate zone cropping systems, carbon inputs can be increased through residue retention, cover crops, reduced summer (bare) fallow, rotations with perennial forage crops, and all practices that increase crop production and residue yields. In the tropics, these practices and others, including improved fallows, mulching and agroforestry, can increase carbon additions to soil (Lal, 1986b).



### 5.3.6 Management Categories
The estimate of CO 2 fluxes is based on inventorying the areas and C stocks for land-use systems predominating within a particular climatic region. As described above, the most significant practices that differentiate land-use and management systems are:

• clearing of native vegetation with conversion to cultivated crops or pasture;

• land abandonment;

• shifting cultivation;

• differing residue addition levels;

• differing tillage systems; and

• agricultural use of organic soils.
Criteria for defining management systems are that the distribution of land areas between the selected systems have changed over the past 20 years and that the systems differ significantly in their soil carbon stocks. The recommended procedure is that country experts define and document an appropriate classification of systems for use in their inventory. A classification of land-use systems is included which can serve as an example for development of country-specific classifications. (See Module 5 for detailed description of land-use systems.) These classes are intended to be sufficiently general that they may be applicable in most countries and include systems that are likely to have significantly different C stocks, based on soil C responses to agricultural practices. Non-agricultural systems (e.g., forest, grassland) should be subdivided into categories on the basis of differences in soil carbon stocks (as well as soil and climate regimes). Organic soils that have been converted to agricultural use are considered separately (see Section 5.3.9).

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.43 T ABLE 5-9 E XAMPLES O F M AJOR L AND -U SE /L AND M ANAGEMENT S YSTEMS W ITHIN T HE M AJOR C LIMATE D IVISIONS Climate Division Land-use System Cold temperate, dry Rangeland (unimproved) Small grain with summer-fallow Small grain with continuous cropping - conventional tillage Small grain with continuous cropping - no till Small grain/forage rotations Hay/improved pasture Successional grasslands Irrigated croplands Cold temperate, moist Forest Small grain monocultures Grain/root crop/perennial forage rotations Permanent pasture Forest/grassland set-aside Warm temperate, dry Rangeland (unimproved) Small grain with summer fallow Small grain/legume rotations with summer fallow Small grain with continuous cropping - conventional tillage Small grain with continuous cropping - no till Small grain/forage rotations Successional grassland Irrigated cropland Warm temperate, moist Forest Pasture/hay Intensive grain production systems, stratified according to: - residue return rate (production level, frequency of perennial forages in rotation, cover crops) - tillage intensity (full inversion, reduced, no tillage) Speciality crops with low residue return Forest/grassland set-aside and reverted lands Tropical, dry Savanna Subsistence farming with drought-resistant grain crops Irrigated cropland Tropical, moist (includes systems for both short and long dry season categories) Forest/woodland Unimproved/degraded pasture Improved pasture Shifting cultivation/fallow rotation Mixed continuous cropping Mechanised continuous cropping Plantations Irrigated cropland (including rice) Tropical, wet Forest/Woodland Agroforestry/perennial multi-strata systems Upland food crop production Perennial monoculture plantations Shifting cultivation/fallow rotation Improved pasture Degraded pasture Wetland (paddy) rice

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.44 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5 . 3 . 7 S u g g e s t e d M e t h o d o l o g y f o r C O 2 

### Flux from Agricultural Soils Three potential sources of CO 2 emissions from agricultural soils are included in the inventory. These are 1) net changes in organic carbon stocks of mineral soil associated with changes in land use and management, 2) emissions of CO 2 from cultivated organic soils (i.e., Histosols) and 3) emissions of CO 2 from liming of agricultural soils.



### 5.3.8 Changes in Mineral Soil Carbon Stocks
Inventory calculation periodNet carbon fluxes are calculated on the basis of changes in carbon stocks over a twentyyear period. For example, to calculate the inventory for 1990, land areas under each climate/soil/land-use class (Table 5-9) in 1970 and in 1990 are determined. Soil carbon values are then assigned to each class, and the summed differences in the total carbon stocks provide an estimate of the current net soil CO 2 flux. For mineral soils, only the top 30 cm are considered, which typically has the highest concentration of carbon and the greatest response to changes in management and landuse. In most soils, management effects on soil carbon at depth are minimal compared to changes that occur in the topsoil (Sombroek et al., 1993) and consequently most information on soil carbon responses to different management practices are limited to the upper soil horizons (0-30 cm depth). The choice of a twenty-year period represents a compromise. The response time of a system to a change in management will differ according to a number of factors. Soil carbon approaches a new equilibrium more rapidly in the tropics compared to temperate soils. The rate of response to different practices also varies. For example, most of the loss of soil carbon following land clearing occurs within <10 yrs (Davidson and Ackerman, 1993). A build up of soil carbon, for example following land abandonment (Jenkinson, 1971a) or with increases in residue inputs, tends to occur more slowly, i.e., the approach to a new equilibrium value is more rapid for degrading systems than for aggrading systems. Thus, the longer the inventory period the closer systems will approach new equilibrium carbon levels. In general, however, the most rapid changes in soil carbon occur during the first 10-20 yrs following a significant change in management practices or land use. Furthermore, a long inventory period has two disadvantages. One is that past land-use information is likely to be less accurate and less available for further in the past. The second is that the balance approach carries an implicit assumption that the rate of land-use and management change over the period is constant. If rates of change are not linear with respect to time, there will be a bias in the estimates that increases with increasing the length of the assessment period. Twenty years was selected as an appropriate time period to include most of the change in carbon stocks resulting from land conversions to agriculture and most other management-induced changes in the tropics. To account for longer response times, such as for land abandonment in the temperate zone, it is recommended that one or more 'successional' system, having different soil carbon stocks, be defined (e.g., abandoned land for <20yrs and abandoned land >20yrs). 

### Soil carbon stock estimates Carbon stock estimates should include the total organic carbon content to a depth of 30 cm as well as the carbon content of the surface litter mat, if present (e.g., in forests, grasslands, and pastures). Woody litter resulting from forest clearance should not be double counted as it is included in the inventory procedures in Forest and Grassland conversion (Section 5.2.2). Fresh crop residue in cultivated systems should not be

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.45 counted. In no-till cropping systems, the minimum (over the year) surface residue loading should be included in the organic carbon stock. The recommended option for assigning carbon stocks according to land management classes (within one or more of the six soil types) is that these be determined by experts in the participating countries. Where available, information from country soil surveys, field studies and long term agricultural experiments, as interpreted by knowledgeable soil scientists and agronomists, will provide the best estimates for these values. However, we have also provided a default methodology for estimating carbon stocks within predefined land-use/management categories (see Management Categories above), using estimates for carbon stocks under native vegetation derived from the FAO/USDA global soil carbon inventory (Eswaran et al., 1993). 

### Calculation procedures for mineral soils
The calculations for net CO 2 -C emissions from mineral soils are straightforward and examples of their application are given in Table 5-10. Negative numbers represent a net decline in soil carbon stocks, hence a net emission or source of carbon to the atmosphere; positive numbers represent a net sequestration or sink of carbon in soil, over the 20-yr inventory period. To derive current net annual emissions the final total should be divided by 20. For the example shown, there is a net increase of carbon storage of 11.9 Tg over the 20-yr inventory period, thus annual net CO 2 -C emissions for this example would be -0.595 Tg/yr, or a carbon sink. Note: It is critical that the total area included in the inventory at time (t) and time (t-20) be identical. The area should represent at least all the land area of the country which has been subject to any significant changes in land-use and/or management practices over the past 20 years. An additional check should be made that the total area within each soil type is constant over the inventory period.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.46 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-10 E XAMPLE OF C ALCULATIONS FOR N ET C HANGE IN C ARBON S TORAGE IN M INERAL S OILS FOR A C OLD T EMPERATE D RY R EGION C OUNTRY - F OR S IMPLICITY O NLY F OUR M ANAGEMENT S YSTEMS A RE I NCLUDED
Landuse Soil type Soil Carbon (t C /ha) Land Area (t-20) (Mha) Land Area

(t) (Mha) C Stock (t-20) (Tg) C Stock (t) (Tg) Net change in Soil Carbon (Tg per 20 yr)

[A] [B] [C] [A X B] [A X C] [A X C] - [A X B]
Grassland High activity 50 3.5 3.6 175 180 5
(unimproved) Sandy 10 2.0 2.0 20 20 0
Aquic 70 0.5 0.4 35 28 -7 Grain/summer-fallow High activity 33 4.0 2.8 132 92.5 -39.6
with conventional Sandy 7 0.5 0.5 3.5 3.5 0
tillage Aquic 35 0 0 0 0 0
Grain/continuous High activity 40 2.4 3.0 96 120 24
with conventional Sandy - 0 00 0 0
tillage Aquic 45 0 0.1 0 4.5 4.5
Hay/improved pasture High activity 50 1.5 2.0 75 100 25
Sandy - 0 00 0 0
Aquic - 0 00 0 0

Total 14.4 14.4 536.5 548.4 11.9



### Default calculation procedures If soil carbon stock estimates according to land-use and soil type are not available we have provided a procedure for estimating these. Estimates are based on global soils information (Table 5-11) compiled by the World Soils Resources division of the Natural Resources Conservation Service of the US Department of Agriculture (USDA), based on FAO and USDA soils information (Eswaran et al., 1993). These values serve as a firstapproximation and should not be considered as a preferable substitute for actual countrylevel data. Approximate organic carbon stocks are for the top 30 cm, in tonnes C/ha, under native vegetation. Histosols (peat soils) are considered in a separate calculation.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.47 T ABLE 5-11 A PPROXIMATE Q UANTITIES O F S OIL O RGANIC CARBON U NDER N ATIVE V EGETATION ( TONNES C / HA TO 0-30 CM DEPTH ) Region High activity

soils Low activity

soils Sandy soils Volcanic soils (Andisols) Wetland soils (Aquic)

Cold temperate, dry 50 40 10 20 70

Cold temperate, moist 80 80 20 70 180

Warm temperate, dry 70 60 15 70 120

Warm temperate, moist 110 70 25 130 230

Tropical, dry 60 40 4 50 60 Tropical moist (long, dry season) 100 50 5 70 100

Tropical moist (short, dry season) 140 60 7 100 140

Tropical, wet 180 70 8 130 180

To estimate soil carbon stocks by different agricultural land-use and management practices, we have compiled a set of coefficients to scale the carbon contents according to major management factors (Table 5-12). Estimates for the scaling factors were based on information from field studies, where available, and expert opinion. The database for these estimates is scanty, particularly from the tropics, and we emphasise that this default procedure is only intended as a first approximation and not as a substitute for countrylevel data where available. Carbon stock estimates are derived according to the formula:

Soil Carbon managed = Soil Carbon native x Base factor x Tillage factor x Input factors

The base factor represents changes in soil organic matter associated with conversion of the native vegetation to agricultural use. Tillage and input factors account for effects of various management practices of lands in agricultural use. Thus these later two factors can be used to capture changes in management trends that have occurred over the inventory period. For example, a long-term cultivated high clay activity soil, under intensive (full) tillage and with low carbon inputs (e.g., straw removal) would be estimated to have 63 per cent (0.7 x 1 x 0.9) of the carbon content in a comparable uncultivated (native) soil. The same soil under no-till with high residue inputs (e.g., cover crops) would be estimated to have a carbon level equivalent to 85 per cent (0.7 x 1.1 x 1.1) of the native soil. Portions of the table where tillage and input factors are not given denote instances where these factors are not applicable to a particular management system or where information was deemed insufficient to go beyond estimating a base factor.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.48 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 5-12 a C OEFFICIENTS U SED IN D EFAULT C ALCULATION P ROCEDURES FOR E STIMATING C ARBON S TOCKS IN M INERAL S OILS System SG b BF c Tillage Factor d Input Factors e

Notillage Reduced tillage Full tillage Low input Medium input High input Mature fallow Shortened fallow Temperate Long-term cultivated A,B,C,D 0.7 1.1 1.05 1.0 0.9 1.0 1.1/1.2 Long-term cultivated E 0.6 1.1 1.05 1.0 0.9 1.0 1.1/1.2 Improved pasture All soils 1.1 ND ND ND Set aside (<20 years) All soils 0.8 ND ND ND Set aside (>20 years) All soils 0.9 ND ND ND Tropical Long-term cultivated A,B,C,D 0.6 1.1 1.0 0.9 0.9 1.0 1.1/1.2 Long-term cultivated E 0.5 1.1 1.0 0.8 0.9 1.0 1.1/1.2 Wetland (Paddy) rice All soils 1.1 ND ND ND ND ND ND Shifting cultivation (including fallow) All soils 0.8 ND ND ND ND ND ND 1.0 0.8

Abandoned/ Degraded land All soils 0.5

Unimproved pasture All soils 0.7 ND ND ND Improved pasture All soils 1.1 ND ND ND

a Filled portions of the table, where tillage and input factors are not given, denote instances where these factors are not applicable to a management system. Where tillage or input factors were not determined (ND), information was deemed insufficient to go beyond estimating a base factor. SG = Soil Group, BF = Base Factor b Soil groups A = High activity, B = Low activity, C = Sandy, D = Volcanic, E = Aquic
c For temperate cultivated soils, the average loss of 30% (0.7) is based on paired profile comparisons by Mann (1985, 1986) and Davidson and Ackerman (1993). Greater losses for cultivation of wet (aquic) soils, relative to other mineral soils, are assumed due to artificial drainage and enhanced decomposition when cultivated (van Noordwijk et al., submitted). Conversion to paddy rice is assumed to slightly increase carbon contents (Greenland, 1985). Carbon levels in improved pastures can exceed native levels with fertilisation and species selection (Fisher et al., 1994, Cerri et al., 1994, Grace et al., 1994). Carbon under shifting cultivation (including the fallow phase) and abandoned degraded lands are based on estimates from Palm et al. (1986), Tiessen et al. (1992) and Woomer et al. (submitted). d Use of no-till is assumed to increase soil carbon by 10% over full tillage (full soil inversion) in temperate systems, based on analysis of long-term experiments in Australia, Canada, Europe and the United States (Paustian et al., 1997); greater effects, over full tillage, are assumed for tropical systems (Aina, 1979, Juo and Lal, 1979, Agboola, 1981). Reduced tillage (i.e., significant soil disturbance but without inversion) is assumed to yield small increases over full tillage (Paustian et al., 1997).
e Input factors apply to residue levels and residue management, use of cover crops, mulching, agroforestry, bare fallow frequency in semi-arid temperate systems. Low input applies to where crop residues are removed or burned, or use of bare fallow; medium input to where crop residues are retained; high input applies to where residue additions are significantly enhanced with addition of mulches, green manure, or enhanced crop residue production (1.1) or regular addition of high rates of animal manure (1.2), relative to the nominal (medium) case. Based on temperate zone studies analysed by Grace et al. (1994) and Paustian et al. (1997), and tropical studies by Jones (1971), Wilson et al. (1982), Sidhu and Sur (1993), Lal et al. (1979, 1980), Mazzarino et al. (1993), Kang and Juo (1986), Inoue (1991), van Holm (1993) and reviews by van Noordwijk et al. (submitted) and Fernandes et al. (submitted).

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.49 

### 5.3.9 Calculation of CO 2 

### Fluxes from Organic Soils Conversion of organic soils to agriculture is normally accompanied by artificial drainage, cultivation and liming, resulting in rapid oxidation of organic matter and soil subsidence. The rate of carbon release will depend on climate, the composition (decomposability) of the organic matter, the degree of drainage and other practices such as fertilisation and liming. Unlike the situation with mineral soils, where carbon levels approach some new equilibrium following changes in land use/management, carbon losses from organic soils can be sustained over long periods of time, in principle, until the organic soil layer has been completely lost. As decomposition proceeds, the more recalcitrant organic matter fractions, having slower decomposition rates, will accumulate. This would tend to reduce CO 2 emissions over time. However, a compensating factor is that with tillage, less decomposed organic matter from below will be continually incorporated into the surface layer as it decomposes and the soil subsides. This process will tend to maintain high rates of CO 2 loss until much of the organic horizon is exhausted. Because of the variability in depth of organic soils, which in many cases is poorly known (Eswaran et al., 1993), a calculation procedure which incorporates the dynamic changes in the depth and the quality of organic matter in these soils was deemed unfeasible at present. Existing data on CO 2 emission rates from organic soils are typically given as rates per unit land area and this approach is used in the current methodology. Use of organic soils for upland crops (e.g., grain, vegetables) gives greater carbon losses than for conversion to pasture or forests, due to deeper drainage and more intensive management practices (e.g., liming, cultivation) (Armentano and Verhoeven, 1990). Armentano and Menges (1986) estimated annual loss rates under crops to be 2.2 tonne/ha/yr in boreal regions (Finland, Russia), 7.9-11.3 tonne/ha/yr in temperate climates (USA and Western, Central and Eastern Europe, China, Japan) and 21.9 tonnes C/ha/yr in Florida and coastal California. Other data from Russian sources (references V.D. Skalaban, personal communication) suggest somewhat lower losses from cultivated organic soils in the boreal zone, on the order of 0.4-1.2 tonnes C/ha/yr. Estimates for annual losses under introduced pastures/forests ranged from 15-70 per cent, with most around 25 per cent, of the rate under crops. The rates recommended for inventory purposes are derived from these values. For tropical systems, there are fewer data although it is expected that rates should be generally higher compared to temperate zone soils due to sustained higher temperatures. The rate used for cropland (20 tonnes C/ha/yr) is twice that for the warm temperate zone, which is similar to the rates reported for subtropical Florida (21.9 tonnes C/ha/yr). We assume that loss rates from conversions to pasture are 25 per cent of those under cropland within each climate region. For the inventory, values are calculated on an annual basis.



### 5.3.10 CO 2 

### Emissions from Liming Agricultural Soils Liming is commonly used to ameliorate soil acidification. Among the compounds used are carbonate containing minerals such as limestone CaCO 3 and dolomite CaMg(CO 3 ) 2 . When added to acid soil these compounds release CO 2 in the bicarbonate equilibrium reaction. The rate of release will vary according to soil conditions and the compound applied. However, in most instances where liming is practised, repeated applications are made every few years. Therefore, for purposes of the inventory, we assume that the addition rate of lime is in near equilibrium to the consumption of lime applied in previous

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.50 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual years. Emissions associated with use of carbonate limes can thus be calculated from the amount and composition of the lime applied annually within a country.



### 5 . 3 . 1 1 T o t a l C O 2 

### Emissions from Agricultural Soils
Total annual emissions of CO 2 , are calculated from i) net changes in carbon storage in mineral soil, ii) CO 2 -C emissions from organic soils and iii) CO 2 -C emissions from liming.



## 5.4 Refinements In Calculations

5.4.1 Introduction There are a number of areas in which the basic calculations could be improved at least theoretically. Simplifying assumptions have been made in many places in order to produce methods consistent with data likely to be available in many countries. The basic calculations focus only on the most important categories for emissions of CO 2 within a much larger set of land-use and forest management activities having some impact on GHG emission fluxes. Some activities are known to result in GHG fluxes, but cannot be quantified based on the available scientific research results. Many of these issues are summarised below to assist users in considering which, if any, of these possible refinements could be included in national inventories, either currently, or in the future as scientific understanding improves. The first section deals with the subcategories already discussed in the basic calculations, but highlights a number of ways in which these calculations could be augmented. The second section discusses additional categories of land-use change or forest management which could be added to the categories in the basic calculations.



### 5.4.2 Possible Refinements or Additions to Basic Categories

C HANGES IN F OREST AND O THER W OODY B IOMASS S TOCKS Prescribed Burning of Forests: Non-CO 2 Trace Gases The issue of prescribed forest burning is complex for two reasons. First, there is the question of the rate of change that humans have induced and second, there is the question of releases of trace gas several years after the burning. Prescribed burning is a method of forest management by which forests are intentionally set on fire in order to reduce the accumulation of combustible plant debris and thereby prevent forest fires, which could possibly be even more destructive. This activity is primarily limited to NorthAmerica and Australia (Seiler and Crutzen, 1980). Because carbon is allowed to reaccumulate on the land after burning, no net CO 2 emissions occur over time, although emissions of CH 4 , CO, N 2 O, and NO x result from the biomass combustion. Some of the issues associated with prescribed forest burning, particularly in the temperate and boreal world, remain important research topics. Some have suggested that prescribed forest burning may be increasing carbon stocks in forests and hence serving as a CO 2 sink, but at the same time adding other radiatively important non-CO 2

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.51 trace gases to the atmosphere. An important issue is the change in burning rate because of human activity. Is prescribed burning, and its consequent emissions, just a man-made replacement for what would have occurred naturally? What is the rate change? If we assume that this question, the rate of change, can be answered, then the issue of trace gas release for prescribed burning is similar to trace gas emissions following forest clearing. This process is under evaluation in the development of the Guidelines. The second complicating issue which should be considered is the release of non-CO 2 trace gases in years after burning. This is also discussed under forest and grassland conversion below. The same uncertainties apply here, although this may be a less important area for prescribed burning, because the forests will be regrowing quickly, and possibly overcoming the conditions which could cause longer term trace gas emissions. Carbon Stock in Dead Organic Matter (excluding soil) of Forests The quantity of carbon in litter, woody debris, belowground remains, and dry standing stems is a significant carbon reservoir in many of the world’s forests. The present methodology does not account for any of these components, which could represent important carbon sink in regrowing forests after abandonment or logging or additional carbon sources when burned during forest clearing or fires. The role of dead organic matter in forest carbon budgets should be considered in future work on inventory methods.
Forest and Grassland Conversion Forest clearing is a very complex and diverse set of activities which can have many interactions with biospheric fluxes of greenhouse gases over long periods of time. The components of this set of interactions which are included in the previous section are those on which there is general agreement among experts of their importance and simple estimation procedures. A number of other possible elements have been discussed in the scientific literature, but are controversial or difficult to calculate at present. Emissions from Burning of Forests A number of aspects of emissions due to burning could be treated in more detail. a. Subsequent burns in years after clearing. In some cases, where forests are cleared for agricultural purposes, the land may be partially burned in the year of clearing, but may also be burned again in later years. Fearnside (1990b) indicates that pastures in the Brazilian Amazon are typically burned two or three times over about a 10 year period. This would cause a larger fraction of carbon in cleared biomass to be released to the atmosphere sooner than the approach now included in the basic calculations, and would certainly increase emissions of non-CO 2 trace gases from biomass burning.

b. Non-CO 2 trace gases released after burning . Basic calculations address the main issues in trace gas production by burning, however, they do not treat all issues. For instance, the effect of past burning, particularly of forests, on trace gas exchanges must eventually be considered. Specifically, the instantaneous release of non-CO 2 trace gases when forests are burned is included in Land Clearing calculations. However, the longer-term release or uptake of these gases following forest burning is an important research issue and should eventually be included in refinements of calculations. The issue of the contemporary release of non-CO 2 trace gases associated with past burning is complex. For example, clearing by burning may stimulate soil nutrient loss. Measurements in temperate ecosystems (e.g., Anderson et al., 1988; and Levine et al., 1988) indicate that surface biomass burning enhances emissions of N 2 O and NO x from the soils for up to 6 months

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.52 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual following the burn; however, in other studies measurements of N 2 O emissions at a cleared and burned tropical forest site in Brazil, begun five months after the burn and continuing for a year, were not significantly different from those taken from a nearby intact forest site (Luizão et al., 1989). The "historical" issue is obviously complex and further research is needed before an adequate methodology for emissions calculations can be proposed. Delayed Release of Non-CO 2 Trace Gases after Land Disturbance. Even when no burning is involved there may still be a release of trace gases. An experiment in a temperate forest in the north eastern United States found that clearcutting resulted in enhanced N 2 O flux to the atmosphere via dissolution of N 2 O in the soil water, transport to surface waters, and degassing from solution (Bowden and Bormann, 1986). An experiment in Brazil found that N 2 O emissions from newly clearcut tropical forests were about three times greater than those from adjacent undisturbed forests (Keller et al., 1986). Conversion of tropical forests to pasture also has been found to result in elevated N 2 O emissions relative to the intact forest soils (Luizão et al., 1989; and Matson et al., 1990). Another example involves the loss of a sink for CH 4 which, in effect, adds to the atmospheric burden of CH 4 . Specifically, the loss of forest area (tropical or temperate) may also result in increased net CH 4 emissions to the atmosphere. Soils are a natural sink of CH 4 (i.e., soils absorb atmospheric CH 4 ), and various experiments indicate that conversion of forests to agricultural lands diminishes this absorptive capacity of soils (Keller et al., 1990; and Scharffe et al., 1990). Conversion of natural grasslands to managed grasslands and to cultivated lands may affect not only the net emission of CO 2 but CH 4 , N 2 O, and CO emissions as well. For instance, the conversion of natural grasslands to cultivated lands has been found in the semi-arid temperate zone to also decrease CH 4 uptake by the soils (Mosier et al., 1991). It is not clear what the effect on N 2 O would be, unless of course nitrogen fertilisation occurs. The effect of conversion of natural grasslands to managed grasslands on trace gas emissions has not been evaluated in the field, except for the effect of associated nitrogen fertilisation on N 2 O emissions. Nitrogen fertilisation on managed fields may increase carbon accumulation on land, relative to the unfertilised system, and grazing by domestic animals may also affect trace gas fluxes. CO fluxes may be affected due to changes in soil temperature and moisture. These effects on trace gas fluxes, however, are highly speculative and remain a research issue. Methane from Termites Attributable to Biomass Left to Decay When forests are cleared, a portion of the cleared biomass may be left to decay on the ground. Frequently some of the biomass decay is accomplished by termites which emit both CH 4 and CO 2 during this process. Fearnside (1990b) estimates that 75 per cent of the unburned carbon is decomposed by termites, and of this 75 per cent, 99.8 per cent is released as CO 2 and 0.2 per cent is released as CH 4 . Fearnside suggests that forest clearing results in increased termite populations and thereby enhances natural termite CH 4 emissions. However, as discussed by Collins and Wood (1984), data from Malaysia, Nigeria, and Japan indicate that clearing and cultivation in some forests reduces termite populations. The only incidence of termite abundance increase following clearing cited by Collins and Wood was entirely due to a fungus-growing termite, a type of termite which is unlikely to produce CH 4 . Because of the uncertainty of the effect of clearing on termite populations and associated CH 4 release, no guidance on calculation of this component is included in the methodology.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.53 Fate of Roots in Cleared Forests The basic calculation ignores the fate of living belowground woody biomass (roots) after forest clearing. The amount of belowground biomass affected, and its fate, need to be considered as work continues beyond the basic calculations. This belowground biomass could be treated as slash but with perhaps a longer (for coarse roots) or shorter (for fine roots) decay times. Alternatively, it might be more reasonable to deal with the belowground biomass in conjunction with soil carbon calculations. This is an area for further development by the relevant expert groups, and also by national experts in individual countries who are encouraged to carry out experimental calculations. See Box 8 for further information on the estimation of the amounts of belowground biomass. Aboveground biomass after conversion In the basic calculation, a single default value (10 tonnes dm/ha) is recommended for aboveground biomass which regrows after forests are cleared for conversion to crops or pastures. This may be somewhat variable depending on the type of crop or other vegetation which regrows. National experts carrying out more detailed assessments may wish to account more precisely for this variability, especially when perennial tree crop are planted.
Abandoned Lands The basic calculations account only for the portion of abandoned lands which regrow toward a natural state. There may be additional releases of carbon from abandoned lands which continue to degrade, e.g., because of erosion. Where data are available, analysts doing detailed assessments may wish to account for this phenomenon.



### 5.4.3 Other Possible Categories of Activity
Several other land-use activities affect the flux of CO 2 and other trace gases between the terrestrial biosphere and the atmosphere. Shifting cultivation may now be reducing the storage of carbon in forests, because of shorter fallow periods, and thereby becoming a net source of CO 2 to the atmosphere. Furthermore, lands under shifting cultivation may be converted to permanent agriculture which, of course, affects the biomass assigned to the land being converted. The changing areas and distribution of wetlands may be adding to or reducing the CH 4 burden of the atmosphere. These issues are complex; often the sign of the flux is not even known, and simple models may not give reasonable results. In this section, some of the issues and possible methodological approaches are recorded; however, an agreed-upon methodology is not yet at hand.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual B OX 8 B ELOWGROUND B IOMASS For forest clearing, carbon in belowground (root) biomass is ignored in the basic calculations, but should be considered. There are large uncertainties concerning the time horizon over which this biomass would oxidise. As noted in the text, it could be considered with decay of slash leftaboveground from forest conversion. There is no recommended step-bystep methodology for calculating the carbon released from this source in the current guidelines. However, interested national experts are encouraged to carry out such calculations and report them to the IPCC using their own methods. The following information about multipliers (root-to-shoot ratios - R/S, average and range of R/S) can be applied to total aboveground biomass to estimate the belowground biomass. Tropical forests moist forest growing on spodosols 1.5 (0.7 - 2.3) lowland very moist forests 0.13 (0.06 - 0.33 montane moist forest 0.22 (0.11 - 0.33) deciduous forests 0.47 (0.23 - 0.85) (e.g., tropical dry and seasonal moist forests) Temperate forests
coniferous 0.20
broadleaf 0.25 Boreal forests coniferous 0.25 (0.20 - 0.30) broadleaf 0.20 (0.15 - 0.25) forest-tundra 0.35 (0.30 - 0.50) Sources: Brown, (1996) for tropical forests; Cooper, (1983) for temperate forests; and Bazilevich, (1993) and Isaev et al., (1993) for boreal forests:
Estimation of CO 2 emissions from belowground biomass after clearing has been identified as an area of future work.

Shifting Cultivation Shifting cultivation, or slash-and-burn agriculture, is a common agricultural practice in the tropics in which short periods of cultivation (usually about 1 - 3 years) alternate with longer periods of fallow (about 10 to 30 years). Clearing occurs by initial cutting and felling, followed by a series of burns. When practised in the traditional manner, shifting cultivation produces some net CO 2 emissions because the forest is allowed to return part-way to its original biomass density during the fallow period. 29 However, increasing

29 Following the first clearing (i.e., clearing of primary forests), the forest biomass may not recover fully to its original density during the fallow period, but instead reaches a reduced level, referred to as a secondary forest.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.55 population pressure has reduced the lengths of fallow periods so that currently much of the fallow land recovers very little and higher net CO 2 emissions are believed to result (Myers, 1989; and Houghton, 1991). Loss of soil carbon also may occur during shifting cultivation, although the loss is certainly far less than for permanent cultivation. Calculation of net emissions due to shifting cultivation requires calculation of average annual emissions due to clearing of forests for cultivation, and calculation of average annual uptake due to abandonment of cultivated lands in the fallow period of the shifting cultivation cycle. This involves monitoring a large number of small parcels of land over time and probably requires a model to do the book keeping. The basic concepts are not difficult. The carbon calculations would proceed almost exactly like the conversion and abandonment terms in the basic methodology; however, the difficulty is that the abandonment period may be shorter, and this may only be apparent by using a cohort-based model and a finite stock of forest. In other words the increasing rate of shifting cultivation (the likely data) will force a shorter fallow period and hence less regrowth, and this dynamic may only become apparent when one models the shifting cultivation cycle within a specific area of available forest. One intermediate simple approach is to split the calculation into the two logical components. The initial conversion component would be treated similarly to the basic calculations; namely, convert the above ground dry biomass 30 to carbon (multiply by 0.50) and assume 90 per cent of this material is released as CO 2 less the amount taken upon by the replacing crops (default value of 10 tonnes dm per hectare). To calculate the uptake of carbon by the regrowing forest during the fallow cycle, simply estimate the amount of land in abandonment (but not yet in steady-state) and the average rate of carbon accumulation per unit area in these fallow lands. The difference would be the net flux of CO 2 associated with shifting cultivation. For the biomass burned in shifting cultivation, non-CO 2 gases (N 2 O, CH 4 , NO x , CO) should be calculated as described in the Forest and Grassland Conversion section above. Flooding and Wetland Drainage Land Flooding Flooding of lands due to construction of hydroelectric dams, or other activities, results in emissions of CH 4 due to anaerobic decomposition of the vegetation and soil carbon that was present when the land was flooded, as well as of organic material that grows in the floodwater, dies, and accumulates on the bottom. The CH 4 emissions from this source are highly variable and are dependent on the ecosystem "type", and the status of the ecosystem, that is flooded (i.e., above- and below-ground carbon, plant types, whether any pre-flooding clearing occurred, etc.) and on the depth and length of flooding (some regions may only be flooded for part of a year) 31 . Rates of CH 4 emissions from freshwater wetlands are also strongly dependent on temperature, and therefore vary

30 Generally, shifting cultivation is practised in secondary forests, since the least dense and most accessible forest areas are most susceptible to this form of clearing. Aboveground biomass density estimates for secondary forests are highly uncertain, and vary significantly both within and among countries because of varying ecosystem types as well as varying intervals between clearings.

31 A detailed analysis of CO 2 and CH 4 emissions from hydroelectric reservoirs in the Amazon has been made and is a significant issue in this and other regions because of the vast areas of forest submerged for the construction of the reservoirs (Rosa and Schaeffer, 1994, 1995).

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.56 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual seasonally, as well as daily. Net emissions of N 2 O and CO also may be affected by this activity, although these fluxes are not well determined. A straightforward CH 4 flux calculation can be based on the area of land flooded, due to hydroelectric production or other human-made causes, an average daily CH 4 emission coefficient, and the number of days in the year that the area is flooded. Since measurements of CH 4 emissions from freshwater wetlands are so variable, both spatially and temporally, the area should be divided into groups based on characteristics such as length of flooding, vegetation type, and latitude. Then appropriate emission coefficients can be chosen for each group, rather than choosing one emission coefficient for the entire area of flooding. Table 5-13 presents average daily CH 4 emission rates for natural wetlands, derived from measured emission rates in field experiments, and average CH 4 production periods based on data on monthly mean temperatures and inundation lengths. These rates and production periods can be used if countries do not have more appropriate estimates.

T ABLE 5-13 A VERAGE M ETHANE E MISSIONS AND P RODUCTION P ERIODS OF N ATURAL W ETLANDS

Wetland Categories

(mg CH 4 /m 2 .day) Emission Rate (mg CH 4 -C/m 2 .day) Production Period or Length of Time Flooded (days) Bogs 11 (1-38) 178

Fens 60 (21-162) 169

Swamps 63 (43-84) 274

Marshes 189 (103-299) 249

Floodplains 75 (37-150) 122

Lakes 32 (13-67) 365

Source : A.selmann and Crutzen, 1989. Note: Average daily emission rates are derived from measured emission rates in field experiments (the range in measured emission rates is in parentheses after the average), and average production periods are based on monthly mean temperature data and lengths of inundation.

Wetland Drainage
Freshwater wetlands are a natural source of CH 4 , estimated to release 100-200 Tg CH 4 /yr due to anaerobic decomposition of organic material in the wetland soils (Cicerone and Oremland, 1988). Destruction of freshwater wetlands, through drainage or filling, would result in a reduction of CH 4 emissions, and an increase in CO 2 emissions due to increased oxidation of soil organic material (Moore and Knowles, 1989). The magnitude of these effects is largely a function of soil temperature and the extent of drainage (i.e., the water content of the soil). Also, since dryland soils are a sink of CH 4 , drainage and drying of a wetland could eventually result in the wetland area changing from a source to a sink of CH 4 (e.g., Harriss et al., 1982).

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.57 Loss of wetland area could also affect net N 2 O and CO fluxes, although both the direction and magnitude of the effect is highly uncertain. Natural dryland soils are a source of N 2 O, believed to emit 9-28 Tg N 2 O/yr (3-9 Tg N 2 O-N) as a result of nitrification and denitrification processes (Seiler and Conrad, 1987). This emission estimate is highly uncertain, however, as emission measurements vary both temporally and spatially by up to an order of magnitude. Moreover, the measurements are not consistently correlated with what are believed to be controlling variables such as soil temperature, moisture, and composition, and vegetation type. Dryland soils both produce and consume CO. Carbon monoxide production, estimated at 2-32 Tg CO/yr (1-14 Tg CO-C), is an abiotic process due to chemical oxidation of humus material (Seiler and Conrad, 1987). It is strongly dependent on soil temperature, moisture, and pH. Destruction of CO is a biological process believed to be due to micro-organisms present in the soil. Carbon monoxide destruction (250-530 Tg CO/yr, or 107-227 Tg CO-C/yr) increases with increasing temperature, although it is independent of soil surface temperature and requires a minimum soil moisture (Seiler and Conrad, 1987). Desert soils have always been found to be a net source of CO, as have savanna soils, at least during the hottest parts of the day. CO destruction outweighs production in humid temperate soils; humid tropical soils are believed to also be a net sink of CO because of their higher soil moisture and lower soil temperature than deserts and savannas.
To calculate the reduction of CH 4 emissions due to wetland drainage, the area drained is multiplied by the difference in the average daily CH 4 emission rate before and after draining, and is multiplied by the number of days in a year that the wetland was emitting CH 4 prior to drainage. The number of days of CH 4 emissions prior to drainage can be approximated by using the number of days in the year that the wetland was flooded. In summary, the difference in CH 4 emissions before and after drainage will vary depending on factors such as soil temperature, extent of drainage, and wetland type. The direction and magnitude of the effects on these gases are highly uncertain and significant advances in our understanding of the biological processes as well as determination of the area extent of the activities will be required before these calculations can be adequately accomplished. It may be possible to include CH 4 calculations associated with land flooding in early refinements of the calculations, but the N 2 O and CO calculations are more difficult and as yet of uncertain importance. Surface Waters Some national experts have pointed out that changes in surface waters due to human activities can result in sequestration of carbon, and presumably other emissions or removals. An example is pollution of lakes due to run off, which can cause eutrophication, increasing the carbon content of waters. Pollution of coastal waters could also have similar effects. No data have been obtained thus far to indicate whether the carbon sequestration effects of such changes are large enough to be significant. However, it is possible that some countries may want to carry out preliminary calculations and report these as part of the ongoing methods development effort.These changes in surface waters are generally a result of combined effects including landuse changes, agricultural practices, wastewater treatment, etc. in the surrounding area. Thus, they do not fit neatly into any of the broad economic sectors which form the fundamental structure of these Guidelines . If national experts consider the changes in surface waters to be primarily a function of land-use changes, the results of preliminary calculations could be reported in the ”Other” subcategory within the Land-Use Change and Forestry category. Alternatively, they could be reported under Waste, Agriculture, or the newly created general “Other” category.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.59 

## T5 Technical Appendix: Deforestation Data

Data on rates of deforestation 32 are essential for calculating the fluxes of CO 2 and other trace gases between terrestrial systems and the atmosphere. When arranged on a country-by-country basis, these data provide the forcing function for computation of country-specific emissions from forest clearing. Recognising that such data sets are not yet available for many countries with the accuracy needed for these computations, this technical appendix provides suggestions for utilising the available global and national sources of data, while bringing new or better sources of information into the calculations when and where they are available.



## T5.1 Food and Agriculture Organization (FAO) Published Data Currently, the most comprehensive international source of data on rates of deforestation broken down to the country level is maintained by the FAO in the following forms: 1. Source data, preferably in the form of a time series, collected in co-operation with member countries, including data on: forest cover, ecofloristic zone and sub-national boundaries, biomass, plantations and conservation, collected and compiled in the form of a geographic information system. 2. Standardised estimates of forest cover, rate of deforestation, afforestation, and biomass/ha at the country level. Standardisation is done by FAO because of variations from country to country in:

• the definitions of "forest", "deforestation" and "afforestation"

• the reference years for forest cover and deforestation measurements The standardisation is intended to bring country data to common definitions of forest cover and reference data, and to make the country information useful for regional and global studies. The basis for standardisation is adjustment functions by ecological zones based on time-series data on forest cover of countries. 3. Data from a global sample survey of forest cover state and change during 1980 and 1990 based on a limited sample of high resolution satellite images using common definitions and measurement techniques. The main aim of this survey is to calibrate regional and global estimates and provide comprehensive information on various types of on-going forest cover changes, in the form of change matrices (1980 and 1990). It should be noted that the sample survey is not intended to check or replace country estimates, but only to provide reliable estimates (i.e., with standard error) of forest cover and rate of change at regional/global levels. This is being done taking into account the inherent limitations of aggregating heterogeneous country data at regional/global levels.

32 This appendix is limited to discussion of current and future international sources of data on rates of deforestation at the national level. It is understood, however, that other types of input data are also key sources of uncertainty in calculations and are also the subject of a great deal of ongoing activity. These include other types of land-use change and land cover data as well as more detailed information on growth rates and biomass densities for different types of forests and other ecosystems.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.60 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual The survey is based on a sampling design covering all tropical countries. The World Reference System 2 (WRS2) for the LANDSAT satellites is used as the sampling frame. LANDSAT scenes covering approximately 3.4 million ha serve as sampling units. In view of cost-benefit considerations, the sampling units were selected from all LANDSAT scenes with a minimum land area of 1 million ha and a forest cover of 10% or more, estimated on the basis of existing vegetation maps. This has restricted the area surveyed to some 62% of the total tropical land area but containing some 87% of the total tropical forest. This first survey round is based on a 10% sample consisting of 117 sampling units randomly selected. The distribution of the selected sampling units by region is 47 in Africa, 30 in Asia and 40 in America. This sample size was chosen to estimate forest cover at global level with standard error less than ± 5%. At each simple location, satellite images of the best quality and appropriate season, separated by an approximate ten-years interval, were selected for observation. The image close to 1990 provides assessment of the current state; whereas the area in common between “1990” and “1980” images provides the assessment to be made of the changes over time. The interpretation was implemented at selected regional and national forestry and/or remote sensing institutions, which have a good knowledge of the sample locations and are traditionally involved in forest resources assessment activities. With the two-fold objective of improving national capacities for forest monitoring and the quality of image interpretation, the FAO Project organised three regional workshops and eight training sessions with national institutions, benefiting 27 countries and 81 participants. The result and quality of the interpretation undertaken by local institutions were centrally reviewed and evaluated. The first result of the survey is its set of transition matrices, one for each Sampling Unit, that describe in detail the class-to-class changes for the land cover classes (see Box below).

L AND C OVER C LASSES Closed Forest Open Forest Long Fallow (forest affecting by shifting cultivation) Fragmented Forest (mosaic of forest/ non-forest)
Shrubs
Short-Fallow (agricultural areas with short fallow period)
Other Land Cover
Water
Plantations (agricultural and forestry plantations)

The matrices associated with the sampling units can be aggregated at various levels following the standard statistical procedure. Mean transition matrices can be produced and subsequent change analysis has been carried out for the three regional and by three ecological zones (Wet and Very Moist, Moist, Dry).

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.61 The FAO Forest Assessment produced in the early 1980s (FAO/UNEP 1981, Lanly 1982) provides a first-order estimate of deforestation rates world-wide. These data produced on a country basis can be used as a baseline land-use rate. A 1990 assessment has been recently published (FAO 1993a), which provides estimates of deforestation rates by country for the period 1981-1990. Thus, some estimates of current and historical rates of deforestation on a country basis can be obtained from these published reports. More detailed information, at the sub-national level, can be obtained by contacting the FAO directly. Deforestation by climatic zone for each tropical country is included in the Workbook. It should be noted, however, that there have been controversies and disagreements regarding FAO estimates of national deforestation rates at times. In some cases where national experts have developed substantially more detailed approaches for their own countries, results have been found to be different from the published FAO estimates. Any internationally provided data should be reviewed carefully by national experts if they are used as a basis for emissions inventory estimates. Some countries have well-developed estimates of deforestation, based on very good measurements, which provide more detail than is available from the FAO assessments (e.g., Arbhabhirama et al., 1987; INPE, 1992). Where detailed national studies exist for the early 1990s they should be the preferred data source for experts preparing national inventories. FAO data may nonetheless be useful for comparative purposes. The choice of input data is always ultimately a decision of the national experts.
Lack of consistent time-series data at national level is considered by FAO staff to be the most critical problem in estimating the deforestation rate. Variation in definitions and measurement techniques from country to country is another problem in making regional and global estimates. FAO has initiated a comprehensive programme for capacity-building in forest resources assessment by mobilising technical and economic co-operation among member countries and among concerned regional and global agencies as follow-up to recommendations of UNCED Agenda 21: Programme Area D.



## T5.2 Ongoing Data Efforts The lack of a comprehensive data set on deforestation rates is a critical problem. The development of such data sets remains one of the priorities for the IPCC process in the coming years (IPCC, 1992). Methods using high resolution remote sensing in conjunction with geographic information systems appear most promising. The International Geosphere-Biosphere Programme's Data Information System (IGBP-DIS) is serving as a central focal point to collect and disseminate information about the various ongoing activities and data sets dealing with land use and changes in land cover. The IGBP-DIS is located in Paris, France (Tel: 33-1-4427-6168, Fax: 33-1-4427-6171). Experts from around the world have begun to build the scientific, technical, and procedural underpinnings of such a system. The World Forest Watch Meeting held in Sao Jose dos Campos, Brazil (June 1992) provided a high-level international forum for the assessment of current approaches to satellite-based forest monitoring. This meeting also served as a basis for forwarding recommendations from the technical and scientific communities to the policy makers and government leaders at UNCED. A variety of international participants were represented at the World Forest Watch Conference. The conference concluded that significant technical and methodological advancements have been made in recent years, and they are now sufficient for proceeding with an observation system which could satisfy both scientific and national-level forest management requirements. A priority action now is to establish a fully functional,

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.62 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual permanent monitoring system. The system would support national forest management, global change science, and international policy information needs, such as those of the IPCC. The current research and development being carried out in laboratories and research centres around the world has shown that it is now feasible to acquire repetitive satellite data sets over very large areas, and that the information derived from such data sets can form the core of a global forest monitoring programme. The International Space Year/World Forest Watch Conference has recently provided illustrations that space observation technology and the community of users are ready for regional and global applications. Progress made on two forest monitoring projects is worth noting in this respect. 1 The National Institute for Space Research (INPE) of the Secretariat of Science and Technology of the Presidency of the Republic of Brazil has made surveys of the entire Legal Amazon (about 5 million square kilometres) using LANDSAT images. This survey was first conducted in 1978 (with 1977 and 1979 being used to cover areas covered by clouds in the 1978 imagery). The studies were repeated in 1988, 1989, 1990 and 1991. These space-based surveys mapped the extent of gross deforestation (i.e., without accounting for forest regeneration or the establishment of plantations) in the portion of the Legal Amazon covered by forest. The ecosystems ranged from dense tropical forest to thick savannas (cerradao) with a total surface area between 3.9 and 4 million square kilometres. The 1978 survey used 232 Land Sat MSS black and white images based on channels 5 and 7 at a scale of 1:250,000. The more recent studies used 229 LANDSAT TM images annually in a colour composite of channels 3,4 and 5 at a scale of 1:250,000. 2 In 1990 NASA, in conjunction with the United States Environmental Protection Agency and the US Geological Survey, began a prototype procedure for using large amounts of high resolution satellite imagery to map the rate of tropical deforestation. This activity, the LANDSAT Pathfinder Project, builds on experience gained during a proof-of-concept exercise as part of NASA's contribution to the International Space Year/World Forest Watch Project. It focused initially on the Brazilian Amazon, and has now been expanded as part of NASA's Earth Observing System activities to cover other regions of the humid tropical forests. This project has succeeded in demonstrating how to develop wall-to-wall maps of forest conversion and regrowth. The project is now in the process of extending its initial proof-of-concept to a large-area experiment across Central Africa, Southeast Asia and the entire Amazon Basin. The project is acquiring several thousand LANDSAT scenes at three points in time - mid 1970s, mid 1980s, and mid 1990s - to compile a comprehensive inventory of deforestation and secondary growth (regrowth of forests on land cleared and subsequently abandoned) to support global carbon cycle models. Methodology and procedures have been identified. Although this exercise is being implemented for most of the tropics, it is not an operational global programme. In principle it will provide an initial large-scale prototype of an operation programme. The use of geographic information system technology is crucial to the project, as it provides the overall framework upon which the raw satellite data can be synthesised with other cartographic, numerical and geographical data for scientific research and national forestry management. As its name implies, this project is exploratory, but it could readily be expanded to form the nucleus of a global scale operational programme.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.63 These two projects demonstrate the feasibility of developing a global tropical forest information system to support an operational tropical forest monitoring programme. High resolution satellite data from LANDSAT or Spot satellites are being used to provide digital maps of deforestation. High resolution data from the LANDSAT series of earth observation satellites can be employed to make regular measurements of deforestation. Large amounts of these data exist in national and foreign archives, dating back approximately 20 years. This satellite data system has been perfected over years of development (5 satellites have been launched) and it is expected to be an operational system into the next century (LANDSAT 7 and 8 are being designed 33 ). This system is complemented by the French SPOT satellites. Thus, a continuous and consistent source of data is available upon which a high resolution, fine-scale (1:250,000 scale mapping) information system could be developed. An operational forest monitoring using high resolution data such as that provided by LANDSAT and SPOT could provide wall-to-wall mapping for the entire humid tropical zone. The approach would be as follows:

• An initial mapping effort would define where and how much deforestation exists in the tropical forests (a baseline assessment). The stratification of forest types and critical regions could be enhanced by the use of coarse resolution information from AVHRR.

• Acquisition of LANDSAT and/or SPOT imagery can be co-ordinated regularly every 3-5 years to obtain cloud-free coverage systematically throughout the tropics. The best way to achieve this is to rely heavily on the foreign ground stations. For example, from the LANDSAT routine and complete coverage for the Amazon Basin and Southeast Asia is possible from several foreign ground receiving stations in these regions. As a rule these stations regularly collect data from every orbital pass within the line-of-sight radius of their antenna. For regions, such as central Africa where no ground station exits, programmed acquisitions from the satellite are possible.

• The imagery is analysed for deforestation using a methodology analogous to that developed by the LANDSAT Pathfinder Project, where a simple delineation of the boundary between intact forest and cleared areas is recorded into a geographic information system. Areas of secondary growth would also be delineated. Subsequent years are compared to the baseline and the increment of new deforestation and secondary growth is recorded. The resulting data set provides a 1:250,000 to 1:500,000 scale map of deforestation at a regular repeat interval, and from this a rate of deforestation is derived.

• These geographically-referenced measurements can directly support the implementation of the IPCC national inventory methodology, which requires a time series of historical forest clearing data, and would require updating at periodic intervals. The proposed accurate and precise deforestation data set would be an important asset to national experts working to implement the IPCC methodology for national emissions and removals from land-use change.

• An accuracy assessment effort will need to be put into place to define and track the measurement variance and error (e.g., ground truthing) This component will need to determine accuracy with respect to: (a) variance due to positional accuracy (i.e., the mapping precision) and (b) the variance associated with image interpretation.

33 Landsat 6 crashed, soon after it was launched.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.64 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual • An effort focused on establishing in-country co-operation will be necessary. Such co-operation fulfils several ancillary but vital objectives: (a) it builds a process of national acceptance of the methods and results through active involvement, (b) it provides a mechanism for technology transfer and training for eventual implementation of national inventories based on remote sensing, (c) it facilitates logistical co-ordination of the field component, (d) it provides direct co-operation at various foreign ground stations, and (e) it enables co-operation with national and regional experts in the interpretation of imagery.



## T5.3 Summary Tropical deforestation and carbon emissions are important components of both science and policy. Yet, in spite of the growing need for precise estimates of deforestation to support both international policy and basic research, an operational programme of measurement, monitoring and mapping has yet to be developed. Comprehensive and systematic information on the extent of forest and forest loss is not available on a global basis. IPCC (1990), for example, considers the rate of tropical deforestation to be one of the key unknowns in global climate change assessment. Any lasting and effective implementation of a global system of national emission inventories to support the IPCC and other international processes will require a new, concerted effort to measure and map tropical deforestation, and develop the data base necessary for other important components of the calculations. These measurements of deforestation from high resolution satellite remote sensing can also support the UN/FAO Forest Assessment by providing quantitative and spatially comprehensive measures of changes in forest cover for the tropics. This Technical Appendix summarises the most comprehensive current data sources for tropical deforestation information, and discusses ongoing efforts to improve on this data via analysis of remote sensing images. Ideally, each country would like to have data on their land-use changes and associated trace gas emissions and uptake over the past 40 to 50 years so that their estimates of current annual net emissions would include delayed and continuous emissions and uptake due to activities that occurred in prior years. Since this is not the case for many countries, the methodology described has made simplifying assumptions in order to treat the effects of past land-use activities on current emissions. This appendix provides some perspective on the available international sources for dealing with one key data gap – data on rates of forest clearing over time.
In future editions of the Guidelines , it may be possible to include more information on data available to assist national experts as a result of some of the ongoing efforts described in this version. It may also be possible and desirable to provide similar discussion of a range of other international data collection efforts which may assist national experts in refining other key data driven uncertainties in the national estimates of emissions and removals from land-use change and forestry. In the meantime, it is recommended that countries continue efforts to collect historical records of land-use change and develop systems of tracking land use through time so that as the methodology is further refined, the land-use change time series needed to account better for emissions and uptake of CO 2 and other trace gases are available.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.65 

## 5.5 References

Agboola, A.A. (1981), “The effects of different soil tillage and management practices on the physical and chemical properties of soils and maize yield in a rainforest zone of western Nigeria.” Agronomy J. 73:247-251. Aina, P.O. (1979), “Soil changes resulting from long-term management practices in western Nigeria.” Soil Sci. Soc. Am. J. 43:173-177. Alcamo, J., G.J.J. Kreileman, M. Krol and G. Zuidema (1994), “Modelling the global society-biosphere-climate system, part 2: computed scenarios.” Water, Air and Soil Pollution (in press). Anderson, I.C., J.S. Levine, M.A. Poth and P.J. Riggan (1988), “Enhanced biogenic emissions of nitric oxide and nitrous oxide following surface biomass burning.” Journal of Geophysical Research 93:3893-3898. Andrén, O., T. Lindberg, U. Boström, M. Clarholm, A-C. Hansson, G. Johansson, J. Lagerlöf, K. Paustian, J. Persson, R. Petterson, J. Schnürer, B. Sohlenius and M. Wivstad, (1989). Chapter 5 - Organic carbon and nitrogen flows. In: Ecology of Arable Land - Organisms, Carbon and Nitrogen Cycling, Ecol. Bull. O. Andrén, T. Lindberg, K. Paustian and T. Rosswall, (eds .) (Copenhagen) 40:85-126. Arbhabhirama, A., D. Phantumvanit, J. Elkington and P. Ingkasuwan (1987), Thailand Natural Resources Profile, Bangkok Thailand Development Research Institute. Armentano, T.V. and E.S. Menges (1986), “Patterns of change in the carbon balance of organic soil-wetlands of the temperate zone.” J. of Ecology 74:755-774. Armentano, T.V. and J.T.A. Verhoeven, (1990), Chapter 10, “Biogeochemical cycles: global.” In: Wetlands and Shallow Continental Water Bodies , B.C. Patten et al., (eds.). SPB Academic Publishing, The Hague, Netherlands, Vol. 1, pp. 281-311. Aselmann, I., and P.J. Crutzen (1989), “Global distribution of natural freshwater wetlands and rice paddies, their primary productivity, seasonality and possible methane emissions.” Journal of Atmospheric Chemistry 8:307-358. Bazilevich, N.I. (1993), Biological productivity of the northern Eurasian ecosystems (in Russian). Nauka, Moscow, Russia. Bowden, W.B. and F.H. Bormann (1986), “Transport and loss of nitrous oxide in soil water after forest clear-cutting.” Science 233:867-869. Brown, S. (1995), Personal communication, based on modelling and inventory data from ongoing research in Tropical America. Brown, S (1996), “A primer for estimating biomass and biomass change of tropical forests.” FAO Forestry Paper , Rome, Italy, in press. Brown, S. and A. E. Lugo. (1990), “Effects of forest clearing and succession on the carbon and nitrogen content of soils in Puerto Rico and U.S. Virgin Islands.” Plant and Soil 124:53-64. Brown S. and A. E. Lugo (1992), “Tropical secondary forests.” Journal of Tropical Ecology. 6:1-32. Brown, S and G. Gaston (1995), “Use of forest inventories and geographic information systems to estimate biomass density of tropical forests: application to tropical Africa.” Environmental Monitoring and Assessment 38:157-168.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.66 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Brown, S., L.R. Iverson, A. Prasad and D. Liu (1993), “Geographical Distribution of Carbon in Biomass and Soils of Tropical Asian Forests.” Geocarto International , 4:45-59. Brown, S., A.E Lugo and J. Chapman (1986), “Biomass of tropical tree plantations and its implications for the global carbon budget.” Canadian Journal of Forest Research 16:390-394. Brown, S. and A.J.R. Gillespie and A.E. Lugo (1989), “Biomass estimation methods for tropical forests with applications to forest inventory data.” Forest Science 35:881-902. Brown, S, J. Sathaye, M. Cannell and P. Kauppi (1996), “Management of forests for mitigation of greenhouse gas emission.” In: Climate Change 1995, Impacts, Adaptations and Mitigations of Climate Change: Scientific-Technical Analyses: The Second Assessment Report of the Inter-Governmental Panel on climate Change , R. T. Watson, N.C. Zinyowera and R.H. Moss (eds.) Cambridge Universtiy Press
, New York, USA

.. Burke, I.C., W.K. Lauenroth and D.P. Coffin (1995), “Recovery of soil organic matter and N mineralisation in semiarid grasslands: Implications for the Conservation Reserve Program.” Ecol. Appl . 5:793-801. Cannell, M.G.R. (1984), “Woody biomass of forest stands.” Forest Ecology and Management , 8:299-312. Cerri, C.C., B. Volkoff and F. Andreaux (1991), “Nature and behaviour of organic matter in soils under natural forest, and after deforestation, burning and cultivation, near Manaus.” Forest Ecology and Management 38:247-257. Cerri, C.C., M. Bernoux and G.J. Blair (1994 ), Carbon pools and fluxes in Brazilian natural and agricultural systems and the implications for the global CO 2 balance. Proceedings of Int. Soil Soc., Acapulco, Mexico. Cicerone, R.J. and R.S. Oremland (1988), “Biogeochemical aspects of atmospheric methane.” Global Biogeochemical Cycles 2:299-327. Collins, N.M. and T.G. Wood (1984), “Termites and atmospheric gas production.” Science 224:84-86. Comery, J.A. (1981), Thesis. Department of Forestry, University of Washington, Seattle, USA. Comins, N.H. and R.E. McMurtrie (1993), “Long term response of nutrient limited forests to CO 2 enrichment: equilibrium behavior of plant-soil models” Ecological Applications , 3:666-681. Cooper, C.F. (1983), “Carbon storage in managed forests.” Canadian Journal of Forest Research , Vol. 13. Cramer, W.P. and A.M. Solomon (1993), “Climate Classification and future global redistribution of agricultural land.” Climate Research 3:97-110. Crutzen, P.J. and M.O. Andreae (1990), “Biomass burning in the Tropics: Impact on atmospheric chemistry and biogeochemical cycles.” Science 250:1669-1678. Dalal, R.C. and R.J. Mayer (1986), “Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. II. Total organic carbon and its rate of loss from the soil profile.” Australian Journal of Soil Research 24:281.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.67 Davidson, E.A. and I.L. Ackerman (1993), “Changes in soil carbon inventories following cultivation of previously untilled soils.” Biogeochemistry 20:161-164. Delmas, R. (1993), “An overview of present knowledge on methane emission from biomass burning.” In: Proceedings of an International IPCC Workshop: Methane and Nitrous Oxides, Methods in National Emissions Inventories and Options for Control, 3- 5 February 1993, Amersfoort, NL. A.R, van Amstel (ed.). RIVM Report No. 481507003, Bilthoven, The Netherlands, July. Detwiler, R.P. (1986), “Land use change and the global carbon cycle: the role of tropical soils.” Biogeochemistry 2:67-93. Denniston, D. (1993), “Air pollution damaging forests.” In: Vital Signs , L.R. Brown, H. Kane and E. Ayres (eds.), W.W. Norton, New York, USA. Dixon, R.K., P.E. Schroeder and J.K. Winjum (1991), Assessment of Promising Forest Management Practices and Technologies for Enhancing the Conservation and Sequestration of Atmospheric Carbon and their Costs at the Site Level . USA Environmental Protection Agency, Office of Research and Development, Washington D.C., USA, EPA/600/3-9/067. Dixon, R.K., S. Brown, R.A. Houghton, A.M. Solomon, M.C. Trexler and J. Wisniewski (1994), “Carbon pools and flux of global forest ecosystems.” Science 263:185- 190. Donigian, A.S., T.O. Barnwell, Jr., R.B. Jackson, IV, A.S. Patwardhan, K.B. Weinrich, A.L. Rowel, R.V. Chinnaswamy and C.V. Cole (1994), Assessment of Alternative Management Practices and Policies Affecting Soil Carbon in Agroecosystems of the Central United States . U.S. EPA Report EPA/6004-94/067. Dormaar, J.F. and S. Smoliak, (1985), “Recovery of vegetative cover and soil organic matter during revegetation of abandoned farmland in a semiarid climate.” Journal of Range Management 38:487, 1985. Dumanski, J., R.L. Desjardins, C. Tarnocai, C. Monreal, E.G. Gregorich, C.A. Campbell and V. Kirkwood, “Possibilities for future carbon sequestration in Canadian agriculture in relation to land use changes.” (Submitted to Climatic Change ). Eden, M.J., P.A. Furley, D.F.M. McGregor, W. Milliken and J.A. Ratter (1991), “Effect of forest clearance and burning on soil properties in northern Roraima, Brazil.” Forest Ecol. Manag. 38:283-290. ECE/FAO (United Nations Economic Commission for Europe/Food and Agriculture Organization of the United Nations) (1992), The Forest Resources of the Temperate Zones . The United Nations, Geneva, Switzerland. Eswaran, H., E. Van Den Berg and P. Reich (1993), “Organic carbon in soils of the world.” Soil Sci. Soc. Am. J. 57:192-194. Farnum, P., R. Timmis and J. Kulp (1983), “Biotechnology of forest yield.” Science 219:694-702. FAO/UNEP (Food and Agriculture Organization of the United Nations/United Nations Environment Programme) (1981), Tropical Forest Resources Assessment Project

. FAO, Rome, Italy. FAO (1988), An Interim Report on the State of the Forest Resources in the Developing Countries . FAO, Rome, Italy. FAO (1993), 1990 Yearbook of Forest Products 1974-1990 . FAO, Rome, Italy.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.68 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual FAO (1990), Interim Report on Forest Resources Assessment 1990 Project . Committee on Forestry, Tenth Session, FAO, Rome, Italy. FAO (1992), The Forest Resources of the Tropical Zone by Main Ecological Regions. Forest Resources Assessment 1990 Project, Food and Agriculture Organization, United Nations. FAO (1993a), Forest Resources Assessment 1990 - Tropical Countries . FAO Forestry Paper No. 112, FAO, Rome, Italy. FAO (1993b), Yearbook of Forest Products (Annual). FAO, Rome, Italy. Fearnside, P.M., M.M. Keller, N.L. Filho and F.M. Fernandes (1990 a ), Rainforest Burning And The Global Carbon Budget: Biomass, Combustion Efficiency And Charcoal Formation In The Brazilian Amazon . National Institute for Research in the Amazon, Brazil. Fearnside, P.M., A.T. Tardin and L.G.Meira Filho (1990 b ), Deforestation Rate in Brazilian Amazon . National Secretariat of Science and Technology, Brazil. Fernandes, E.C.M., M.P. Motavalli, C. Castilla and L. Mukurumbira, “Management control of soil organic matter dynamics in tropical land-use systems.” (Submitted to Geoderma ). Finnish Forest Research Institute (1995), Yearbook of forest statistic. SVT Agriculture and Forestry 5, Helsinki, Finland. Fisher, M.J., I.M. Rao, M.A. Ayarza, C.E. Lascano, J.I. Sanz, R.J. Thomas and R.R. Vera (1994), “Carbon storage by introduced deep rooted grasses in the South American savannas.” Nature 371:236-238. Gifford, R.M. (1994), “Implications of CO 2 effects on vegetation for the global carbon budget.” In: The Global Carbon Cycle , M. Heimann (ed.). Proceedings of the NATO Advance Study Institute, Il Ciocco, Italy, September 8-20, 1991. Grace, P.R., J.N. Ladd and J.O. Skjemstad (1994), “The effect of management practices on soil organic matter.” In: C.E. Pankhurst et al. (eds.), Soil Biota: Management in Sustainable Farming Systems , CSIRO, Melbourne, Australia, pp. 162-171. Grace, J., J. Lloyd, J. McIntyre, A. C. Miranda, P. Meir, H. S. Miranda, C. Nobre, J. Moncrieff, J. Massheder, Y. Malhi, I. Wright and J. Gash (1995), “Carbon dioxide uptake by an undisturbed tropical rain forest in southwest Amazonia, 1992 to 1993.” Science 270:778-780. Greenland, D.J. (1985), “Nitrogen and food production in the tropics: Contributions from fertiliser nitrogen and biological nitrogen fixation.” In: Nitrogen Management in Farming Systems in Humid and Sub-humid Tropics . B.T. Kang and J. van der Heide (eds.), pp. 9-38. Proceedings of International Institute of Tropical Agriculture Symposium, Ibadan, Nigeria, Oct. 23-26, 1984. Greenland, D.J. (1995), “Land-use and soil carbon in different agroecological zones.” In: Soil Management and Greenhouse Effect: Advances in Soil Science . R. Lal, J. Kimble, E. Levine, and B.A. Stewart (eds.), CRC, Lewis Publishers, Boca Raton, USA, Chapter 2, pp. 9-4. Greenland, D.J. and P.H. Nye (1959), “Increases in the carbon and nitrogen contents of tropical soils under natural fallow.” J. Soil Sci. 10:284-298. Haas, H.J., C.E. Evans and E.F. Miles, (1957), Nitrogen and carbon changes in Great Plains soils as influenced by cropping and soil treatments . Technical Bulletin No. 1164 USDA, State Agricultural Experiment Stations.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.69 Hamilton, G.J. (1985), Forest Mensuration Handbook . Forestry Commission Booklet No. 39, London, UK. Harmon, M.E., W.K. Ferrel and J.F. Franklin (1990), “Effects on carbon storage of conversion of old-growth forests to young forests.” Science 247:699-702. Harriss, R.C., D.I. Sebacher and F.P. Day Jr. (1982), “Methane flux in the Great Dismal Swamp.” Nature 297:673-674. Haynes, R.J., R.S. Swift and R.C. Stephen (1991), “Influence of mixed cropping rotations (pasture-arable) on organic matter content, water stable aggregation and clod porosity in a group of soils.” Soil Tillage Research 19:77-81 Houghton, R.A., J.E. Hobbie, J.M. Melillo, B. Moore, B.J. Peterson, G.R. Shaver and G.M. Woodwell (1983), “Changes in the carbon content of terrestrial biota and soils between 1860 and 1980: a net release of CO 2 to the atmosphere.” Ecological Monographs 53(3):235-262. Houghton, R.A., R.D. Boone, J.R. Fruci, J.E. Hobbie, J.M. Melillo, C.A. Palm, B.J. Peterson, G.R. Shaver and G.M. Woodwell (1987), “The flux of carbon from terrestrial ecosystems to the atmosphere in 1980 due to changes in land use: geographic distribution of global flux.” Tellus 39B:122-1 2 9. Houghton, R.A. (1991), “Tropical deforestation and atmospheric carbon dioxide.” Climatic Change

. Inoue, T. (1991), “Soil improvement in corn cropping by long-term application of organic matter in utisols of Thailand,” pp. 174-185. In: Soil Constraints on Sustainable Plant Production in the Tropics . Proceedings of the 24th International Symposium on Tropical Agriculture Research. Tropical Agriculture Research Series 24, Kyoto, Japan, August 14-16, 1990. INPE (1992), Deforestation in Brazilian Amazonia . Instituto Nacional de Pesquisas Espaciais. IPCC (1990), Climate Change: the IPCC Scientific Assessment . J.T. Houghton, G.J. Jenkins and J.J. Ephraums (eds.) Intergovernmental Panel on Climate Change, Cambridge, UK: Cambridge University Press. IPCC (1992), Climate Change 1992: the Supplementary Report to the IPCC Scientific Assessment . J.T. Houghton, B.A. Callander and S.K. Varney (eds.). Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK. IPCC (1995), Climate change 1994. Radiative Forcing of Climate Change and An Evaluation of the IPCC IS92 Emission Scenarios . J.T. Houghton, L.G. Meira Filho, J. Bruce, Hoesung Lee, B.A. Callander, E. Haites, N. Harris and K. Maskell(eds.).. Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK. IPCC (1996), Climate Change 1995 - The Science of Climate Change. The Second Assessment Report of the Inter-Governmental Panel on Climate Change , J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattemberg and K. Maskell (eds.) Cambridge University Press, Cambridge, UK. Isaev, A.S., G.N. Korovin, A.I. Utkin, A.A. Prjazhnikov and D.G. Zamolodchikov (1993), “The estimation of the carbon content and annual deposition in phytomass of Russian forest ecosystems.” (in Russian) Lesovedenie 5:3-10.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.70 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Iverson, L.R, S. Brown, A. Prasad, H. Mitasova, A.J.R. Gillespie and A.E. Lugo (1994), “Use of GIS for estimating potential and actual biomass for continental South and Southeast Asia.” In: Effects of Land Use Change on Atmospheric CO 2 Concentrations: Southeast Asia as a Case Study, (ed. V. Dale), pp. 67-116. Springer Verlag, New York, USA. Jenkinson, D.S. (1971a), The accumulation of organic matter in land left uncultivated. Rothamsted Exp. Sta. Ann. Rep for 1970, part 2, pp. 113-137. Jenkinson, D.S. (1971b), “Studies on the decomposition of C14 labeled organic matter in soil.” Soil Science 111:64-70. Jenkinson, D.S., D.E. Adams and A. Wild (1991), “Model estimates of CO 2 emissions from soil in response to global warming.” Nature 351:304-306. Jones, M.J. (1971), “The maintenance of soil organic matter under continuous cultivation at Samaru, Nigeria.” J. Agric. Sci. 77:473-482. Juo, A.S.R. and R. Lal (1979), “Nutrient profile in a tropical alfisol under conventional and no-till systems.” Soil Science 127:168-173. Kang, B.T. and A.S.R. Juo (1986), “Effect of forest clearing on soil chemical properties and crop performance.” In: Land Clearing and Development in the Tropics , R. Lal, P.A. Sanchez and R.W. Cummings, Jr. (eds.), A.A. Balkema, Rotterdam/Boston, pp. 383-394. Kauppi, P.E., K. Mielikainen and K. Kuusela (1992), “Biomass and carbon budget of European forests, 1971 to 1990.” Science 256:70-74. Keller, M., M.E. Mitre and R.F. Stallard (1990), “Consumption of atmospheric methane in soils of Central Panama: effects of agricultural development.” Global Biogeochemical Cycles , 4:21-27. King, A. W., W. M. Post and S. D. Wullschleger (1996), “The potential response of terrestrial carbon storage to changes in climate and atmospheric CO 2 .” Climatic Change (In press). Kononova, M.M. (1966), Soil organic matter. Its nature, its role in soil formation and in soil fertility . Pergamon Press, Oxford, United Kingdom. Kokorin, A.O. and I.M. Nazarov (1995a), “Specific requirements to methodology for estimating of CO 2 fluxes in boreal and temperate forests.” Quarterly J. Hungarian Meteorological Service Idojoras 99:3-4, 227-234. Kokorin, A.O. and I.M. Nazarov (1995b), “The analysis of growth parameters of Russian boreal forests in warming, and its use in carbon budget model.” Ecological Modelling 82:139-150. Kolchugina, T.P. and T.S. Vinson (1993), “Comparison of two methods to assess the carbon budget of forest biomass in the former Soviet Union.” Water, Air and Soil Pollution 70:207-221. Kolchugina, T.P. and T.S. Vinson (1996), “Management options to conserve and sequester carbon in the agricultural sector of the former Soviet Union.” Mitigation and Adaptation Strategies 1:1-22. Lacaux, J.P., H. Cachier and R. Delmas (1993), “Biomass burning in Africa: an overview of its impact on atmospheric chemistry.” In: Fire in the Environment: The Ecological, Atmospheric and Climatic Importance of Vegetation Fires . P.J. Crutzen and J.G. Goldammer (eds.), J. Wiley & Sons Ltd.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.71 Lal, R., G.F. Wilson and B.N. Okigbo (1979), “Changes in properties of an alfisol produced by various crop covers.” Soil Science 127:377-380. Lal, R., D. De Vleeschauwer and R.M. Nganje (1980), “Changes in properties of a newly cleared tropical Alfisol as affected by mulching.” Soil Sci. Soc. Am. J. 44:827-833. Lal, R. (1986a), No-tillage and surface-tillage systems to alleviate soil-related constraints in the tropics. In: No-tillage and Surface-tillage Agriculture: The Tillage Revolution, M.A. Spraque and G. B. Triplett (eds .), Wiley, N.Y., pp. 261-317. Lal, R. (1986b), “Soil surface management in the tropics for intensive landuse and high and sustained production.” Adv. Soil Sci . 5:1-105. Lanly, J.P. (1982), Tropical Forest Resources . Food and Agriculture Organization of the United Nations (FAO) Paper 30, FAO, Rome, Italy. Lee, J.J., D.L. Phillips and R. Liu (1993), “The effect of trends in tillage practices on erosion and carbon content of soils in the U.S. corn belt.” Water, Air and Soil Pollution 70:389-401. Leith, H. and R.H. Whittaker (eds.) (1975), Primary Productivity of the Biosphere . Ecological Studies No. 14. Springer-Verlag, New York-Heidelberg-Berlin. Levine, J.S., W.R. Cofer III, D.I. Sebacher, E.L. Winstead, S. Sebacher and P.J. Boston (1988), “The effects of fire on biogenic soil emissions of nitric oxide and nitrous oxide.” Global Biogeochemical Cycles 2:445-449. Lobert, J.M., D.H. Scharffe, W.M. Hao and P.J. Crutzen (1990), “Importance of biomass burning in the atmospheric budgets of nitrogen-containing gases.” Science 346- 552-554. Lugo, A.E. and S. Brown (1992), “Tropical forests as sinks for atmospheric carbon.” Forest Ecology and Management 54: 239-256. Lugo, A.E. and S. Brown (1993), “Management of tropical soils as sinks or sources of atmospheric carbon.” Plant and Soil 149:27-41. Lugo, A.E., M.J. Sanchez and S. Brown (1986), “Land-use and organic carbon content of some subtropical soils.” Plant and Soil 96:185-196. Luizão, F., P. Matson, G. Livingston, R. Luizão and P. Vitousek (1989), “Nitrous oxide flux following tropical land clearing.” Global Biogeochemical Cycles 3:281-285. Mann, L.K. (1985), “A regional comparison of carbon in cultivated and uncultivated alfisols and mollisols in the central United States.” Geoderma 36:241. Mann, L.K. (1986), “Changes in soil carbon storage after cultivation.” Soil Sci . 142:279- 288. Martel, Y.A. and E.A. Paul (1974), “Effects of cultivation on the organic matter of grassland soils as determined by fractionation and radiocarbon dating.” Can J. Soil Sci. 54:419-26. Martin, R.J., P.R. Grace, C.A. Anderson and J.C. Fegent (eds.), 1995, “Long-term agronomic experiments for productive and sustainable farming systems.” Aust. J. Prod. Agric. (Special Issue) 35:825-1062. Matson, P.A., P.M. Vitousek, G.P. Livingston and N.A. Swanberg (1990), “Sources of variation in nitrous oxide flux from Amazonian ecosystems.” Journal of Geophysical Research 95:16789-16798.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.72 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Mazzarino, M.J., L. Szott and M. Jimenez (1993), “Dynamics of soil total C and N, microbial biomass, and water-soluble carbon in tropical agroecosystems.” Soil Biology and Biochemistry 25:205-214. Melillo, J.M., A.D. McGuire, D.W. Kicklighter, B. Moore III, C.J. Vorosmarty and A.L. Schloss (1993), “Global climate change and terrestrial net primary production.” Nature 363:234-240. Moore, T.R. and R. Knowles (1989), “The influence of water table levels on methane and carbon dioxide emissions from peatland soils.” Canadian Journal of Soil Science 69:33-38. Mosier, A., D. Schimel, D. Valentine, K. Bronson and W. Parton (1991), “Methane and nitrous oxide fluxes in native, fertilised and cultivated grasslands.” Nature 350:330-332. Myers, N. (1989), Deforestation Rates in Tropical Forests and their Climatic Implications . A Friends of the Earth Report, London, UK. Nabuurs, G.J. and G.M.J. Mohren (1993), Carbon Fixation Through Forestation Activities , IBN Research Report 93/4, Institute Forestry and Nature Research, Wageningen, The Netherlands. Nye, P.H. and D.J. Greenland (1960), “The Soil under Shifting Cultivation.” Commonwealth Agricultural Bureau, UK. Palm, C.A., R.A. Houghton and J.M. Melillo (1986), “Atmospheric carbon dioxide from deforestation in Southeast Asia.” Biotropica 18:177-188. Paul, E.A. and J.A. van Veen (1978), “The use of tracers to determine the dynamic nature of organic matter.” In: Trans. 11th Internat. Cong Soil Sci. 1978, Edmonton, Vol. 3 pp. 61-102. Paul, E.A., K. Paustian, E.T. Elliott and C.V. Cole (eds.), 1997, Soil organic matter in temperate agro/ecosystems: Long-term Experiments in North America. CRC Press, Boca Raton, Florida, U.S.A. Paustian, K., G.P. Robertson and E.T. Elliott (1995), “Management impacts on carbon storage and gas fluxes (CO 2 , CH 4 ) in mid-latitude cropland and grassland ecosystems.” In: Soil Management and Greenhouse Effect. Advances in Soil Science R. Lal, J. Kimble, E. Levine and B.A. Stewart (eds.), pp. 69-84, CRC Press, Boca Raton, USA. Paustian, K., H.P. Collins and E.A. Paul (1997), “Management controls on soil carbon.” In: Soil organic matter in temperate agroecosystems: Long-term Experiments in North America , E.A. Paul, K. Paustian, E.T. Elliott and C.V. Cole (eds.), CRC Press, pp. 15-49. Paustian, K., J. Cipra, C.V. Cole, E.T. Elliott, K. Killian and G. Bluhm, “Contributions of Grassland CRP lands to carbon sequestration and CO 2 mitigation.” (submitted
to J Prod. Agric .) Potter, C.S., J.T. Randerson, C.B. Field, P.A. Matson, P.M. Vitousek, H.A. Mooney and S.A. Klooster (1993), “Terrestrial Ecosystem Production: A process model based on global satellite and surface data.” Global Biogeochemical Cycles 7:811-842. Powlson, D.S., P. Smith and J.U. Smith (eds.), 1996, “Evaluation of soil organic matter models using existing, long-term datasets.” NATO ASI Series, Global Environmental Change , Vol. 38, Springer Verlag, Berlin.

## 5 L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 5.73 Powlson, D.S., P. Smith, K. Coleman, J.U. Smith, M.J. Glendining, M. Korshens and W. Franko, “A European network of long-term sites for studies on soil organic matter.” Soil Tillage Research (submitted). Rasmussen, P.E. and C.R. Rohde (1988), “Long-term tillage and nitrogen fertilisation effects on organic nitrogen and carbon in a semiarid soil.” Soil Science Society of America Journal 52:1114-1117. Rastetter, E.B., R.B. McKane, G.R. Shaver, J.M. Melillo et al. (1992), “Changes in C storage by terrestrial ecosystems: how C-N interactions restrict responses to CO 2 and temperature.” Water, Air and Soil Pollution 64:327-344. Rosa, L.P., and R. Schaeffer (1994), “Greenhouse gas emission from hydroelectric reservoir.” Ambio 23 (2):164-165. Rosa, L.P., and R. Schaeffer (1995), “Global warming potential - the case of emission from dams.” Energy Policy 23: Scharffe, D., W.M. Hao, L. Donoso, P.J. Crutzen and E. Sanhueza (1990), “Soil fluxes and atmospheric concentration of CO and CH 4 in the northern part of the Guyana Shield, Venezuela.” Journal of Geophy. Res. 95:22,475-22,480. Schimel, D., I. G. Enting, M. Heimann, T. M. L. Wigley, D. Raynaud, D. Alves and U. Seigenthaler (1995), “CO 2 and the carbon cycle.” In: Climate change 1994 radiative forcing of climate change and an evaluation of the IPCC IS92 emission scenarios , J. T. Houghton, L. G. Meira Filho, J. Bruce, H. Lee, B. A. Callander, E. Haites, N. Harris and K. Maskell (eds.). Published for the IPCC, Cambridge University Press, Cambridge, U.K., pp. 35-71. Schlesinger, W.H. (1986), Changes in soil carbon storage and associated properties with disturbance and recovery. In: J.R. Trabalka and D. E. Reichle (eds.), The Changing Carbon Cycle: A Global Analysis, Springer-Verlag, N.Y., pp. 194-220. Schroeder, P. (1992), “Carbon storage potential of short rotation tropical tree plantations.” Forest Ecology and Management , 50:31-41. Seiler, W. and P.J. Crutzen (1980), “Estimates of gross and net fluxes of carbon between the biosphere and the atmosphere from biomass burning.” Climatic Change 2:207-247. Seiler, W. and R. Conrad (1987), “Contribution of tropical ecosystems to the global budgets of trace gases, especially CH 4 , H 2 , CO, and N 2 O.” In: The Geophysiology of Amazonia, . Dickinson, R.E. (ed.), John Wiley, New York, USA, pp. 133-160. Sidhu, A.S. and H.S. Sur (1993), “Effect of incorporation of legume straw on soil properties and crop yield in a maize-wheat sequence.” Trop. Agric. (Trinidad) 70:226-229. Smith, T.M. and H.H. Shuggart (1993), “The transient response of terrestrial carbon storage to a perturbed climate.” Nature , 361:523-526. Smith, W.N., P. Rochette, C. Monreal, R.L. Desjardins, E. Pattey and A. Jaques, “The rate of carbon change in agricultural soils in Canada at the landscape level.” Canadian Journal of Soil Science (in press). Smith, P., J.U. Smith and D.S. Powlson (eds.), A directory of metadata on soil organic matter models and long-term datasets . IGBP/GCTE Report series (submitted). Sombroek, W.G., F.O. Nachtergaele and A. Hebel (1993), “Amounts, dynamics and sequestering of carbon in tropical and subtropical soils.” Ambio 22:417-426.

## L AND 

## -U SE 

## C HANGE 

## & F ORESTRY

5.74 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Steiner, R.A. and R.W. Herdt, 1993, A global directory of long-term agronomic experiments. Vol. 1: Non-European experiments . The Rockefeller Foundation, New York, N.Y. Tans P.P., I.Y. Fung and P.H. Daum (1990), “Observational constraints on the global atmosphere carbon dioxide budget.” Science 247:1431-1438. Tiessen, H., J.W.B. Stewart and J.R. Bettany (1982), “Cultivation effects on the amounts and concentration of carbon, nitrogen and phosphorus in grassland soils.” Agronomy Journal . 74:831-835 Tiessen, H., I.H. Salcedo and E.V.S.B. Sampaio (1992), “Nutrient and soil organic matter dynamics under shifting cultivation in semi-arid north-eastern Brazil.” Agric. Ecosys. Environ . 38:139-151. Tiessen, J. E. Cuevas and P. Chacon (1994), “The role of soil organic matter stability in soil fertility and agricultural potential.” Nature 371:783-785. Trumbore, S.E. (1993), “Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements

. ” Global Biogeochem. Cycles 7:275-290. Tyson, K.C., D.H. Roberts, C.R. Clement and E.A. Garwood (1990), “Comparison of crop yields and soil conditions during 30 years under annual tillage or grazed pasture.” J. Agric. Sci . 115:29-40. USDA Forest Service (1987), Wood Handbook: Wood as an Engineering Material

. Agricultural Handbook No. 72. USDA, Washington, D.C., USA. Van Holm, L.H.J. (1993), “Soil organic matter dynamics in a Sri Lankan soil.” In: Soil Organic Matter Dynamics and Sustainability of Tropical Agriculture , K. Mulongoy and R. Merckx (eds.), Wiley-Sayce Co. Publication, pp. 121-133. Van Noordwijk, M., C. Cerri, P.L. Woomer, K. Nugroho and M. Bernoux . Soil carbon dynamics in the humid tropical forest. Paper for GCTE/TSBF Workshop on Management of Carbon in Tropical Soils under Global Change, Nairobi, Feb. 7- 11, 1994 Geoderma (submitted ). VEMAP members (1996 ), Vegetation/ecosystem modeling and analysis project: Comparing biogeography and biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO 2 doubling. Global Biogeochemical Cycles 9: 407-437. Vompersky, S.E. and A.I. Utkin (1988), The analysis of forest productivity structure (in Russian). Nauka, Moscow, Russia. Whittaker, R.H. and G.E. Likens (1973), “Carbon in the biota.” In: Carbon and the Biosphere , G.M. Woodwell, and E.V. Pecan (eds.), US Atomic Energy Commission, Symposium Series 30. National Technical Information Service, Springfield, VA, USA, pp. 281-302. Whittaker, R.H. and G.E. Likens (1975), “The biosphere and Man.” In: Primary Productivity of the Biosphere, H. Lieth and R.H. Whittaker (eds.), Springer-Verlag, New York, USA, pp. 305-328. Wilson, G.F., R. Lal and B.N. Okigbo (1982), “Effects of cover crops on soil structure and on yield of subsequent arable crops grown under strip tillage on an eroded Alfisol.” Soil & Tillage Research 2:233-250. Woomer, P.L., C.A. Palm, N. Karanja, J.N. Qureshi and J. Kotto-Same, “Carbon sequestration and organic resource management in African smallholder agriculture.” Advances in Soil Science (submitted)Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## C HAPTER 

# 6 

# W ASTE

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.1 

# 6. W ASTE



## 6.1 Overview Disposal and treatment of industrial and municipal wastes can produce emissions of most of the important greenhouse gases (GHG). Solid wastes can be disposed of through landfilling, recycling, incineration or waste-to-energy. This chapter will deal with emissions resulting from landfilling of solid waste, treatment of liquid wastes and waste incineration. Greenhouse gas emissions from waste-to-energy, where waste material is used directly as fuel or converted into a fuel, should be calculated and reported under the Energy Chapter. The most important gas produced in this source category is methane (CH 4 ). Approximately 5-20 per cent (IPCC, 1992) of annual global anthropogenic CH 4 produced and released into the atmosphere is a by-product of the anaerobic decomposition of waste. Two major sources of this type of CH 4 production are solid waste disposal to land and wastewater treatment. In each case, methanogenic bacteria break down organic matter in the waste to produce CH 4 . In previous editions of the IPCC Guidelines (1995), solid waste disposal sites were characterised as “open dumps” or “sanitary landfills,” both of which can produce CH 4 if the waste deposited in them contains organic matter (IPCC, 1995). Open dumps were defined as shallow, open piles, generally only loosely compacted, and with no provision for control of any pollutants generated, where scavenging by animals and humans can remove much of the biodegradable wastes. Sanitary landfills, in contrast, were defined as sites specifically designed to receive wastes, which may manage these waste with practices such as compacting, use of liners, daily cover, and a final cap. Recognising that the distinction between landfills and open dumps is not always clear, the Revised 1996 IPCC Guidelines (this chapter) instead characterises all sites at which solid waste is deposited to land as “solid waste disposal sites” (SWDSs).
In addition to CH 4 , solid waste disposal sites can also produce substantial amounts of CO 2 and non-methane volatile organic compounds (NMVOCs). Decomposition of organic material derived from biomass sources (e.g., crops, forests) which are regrown on an annual basis is the primary source of CO 2 released from waste. Hence, these CO 2 emissions are not treated as net emissions from waste in the IPCC Methodology. If biomass raw materials are not being sustainably produced, the net CO 2 release should be calculated and reported under the Agriculture and Land-Use Change and Forestry Chapters. The process of wastewater treatment produces NMVOCs as well as CH 4 (CORINAIR, 1994). These emissions are not currently addressed in the Revised Guidelines

. Wastewater treatment is also a source of N 2 O, and a methodology for estimating N 2 O emissions is included in this Chapter for human sewage. (Chapter 4 of these Revised Guidelines addresses N 2 O emissions from agriculture, using a life-cycle emissions approach.) Waste incineration, like all combustion, can produce CO 2 , CH 4 , CO, NO x , N 2 O and NMVOCs. No detailed methodologies are provided here for this source category. Instead, the section on waste incineration later in this chapter provides references to methods available for some of the gases. For CH 4 and N 2 O it is only possible to report preliminary estimates and research results at this time. Further studies are needed to

## W ASTE

6.2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual give more information about GHG emissions from this source category. For additional information, refer to the discussion of emissions from combustion in Chapter 1. The sections in this chapter dealing with land disposal of solid waste and wastewater treatment give background information on the source, describe a methodology to estimate CH 4 and N 2 O emissions, and discuss uncertainties associated with estimating emissions. This is consistent with the priorities under the IPCC Methodology programme. National experts are encouraged to report any other relevant emissions for which data are available, along with documentation of methods used. This will greatly assist in the development of more complete methods for future editions of IPCC Guidelines . For information on estimation procedures and emissions factors for other GHGs which are currently not provided in this chapter, experts should consult extensive existing literature developed by other emissions inventory programmes. Some key examples are:

• Default Emissions Factor Handbook (CORINAIR, 1994);

• Joint Atmospheric Emission Inventory Guidebook (1st edition) (EMEP/CORINAIR, 1996);

• US EPA's Compilation of Air Pollutant Emissions Factors (AP-42) (US EPA, 1995);

• Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory (Stockton and Stelling, 1987);

• Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines (US EPA, 1991; Doorn and Barlaz, 1995);

• Greenhouse Gases from Wastewater Treatment: Collection and Review of Country Specific Data and Preliminary Emission Models (Doorn and Eklund, 1995).



## 6 . 2 Met h a n e E m i s s i on s f r om S ol i d W a s t e Disposal Sites

6.2.1 Introduction The gases produced in solid waste disposal sites, particularly CH 4 , can be a local environmental hazard if precautions are not taken to prevent uncontrolled emissions or migration into surrounding land. Landfill gas is known to be produced both in managed “landfill” and “open dump” sites. Both are considered here as solid waste disposal sites (SWDSs). Gas can migrate from SWDSs either laterally or by venting to atmosphere, causing vegetation damage and unpleasant odours at low concentrations, while at concentrations of 5-15 per cent in air, the gas may form explosive mixtures. More recently, increasing attention has focused on the role of CH 4 in global atmospheric change. Methane from SWDSs contributes a significant proportion of annual global CH 4 emissions, although the estimation is subject to a great deal of uncertainty. Estimates of global CH 4 emissions from SWDSs range from less than 20 to 70 Tg/yr (Bingemer and Crutzen, 1987, US EPA, 1994), or about 5 per cent to 20 per cent of the total estimated emissions of 375 Tg/yr (IPCC, 1996) from anthropogenic sources globally. This section will describe the processes that result in gas generation from SWDSs and the factors which affect the amount of CH 4 produced. It will then describe two methodologies for estimating CH 4 emissions from SWDSs. One of these methods is a default base method which all countries can use to estimate CH 4 emissions from different

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.3 types of SWDSs. It is recommended that countries which have adequate data also estimate their emissions using the second method presented. Finally, this section discusses sources of uncertainty associated with any estimates of CH 4 emissions from SWDSs, in particular the availability and quality of data required.



### 6.2.2 Gas Generation from Solid Waste Disposal Sites Organic waste in SWDSs is broken down by bacterial action in a series of stages that result in the formation of CH 4 and CO 2 (termed biogas or landfill gas) and further bacterial biomass. In the initial phase of degradation, organic matter is broken down to small soluble molecules including a variety of sugars. These are broken down further to hydrogen, CO 2 , and a range of carboxylic acids. These acids are then converted to acetic acid which, together with hydrogen and CO 2 , forms the major substrate for growth of methanogenic bacteria. Landfill gas consists of approximately 50 per cent CO 2 and 50 per cent CH 4 by volume. However, the percentage of CO 2 in landfill gas may be smaller because of decomposition of substrates with a high hydrogen/oxygen ratio (e.g., fats, hemicellulose) and because some of the CO 2 dissolves in water within the site. SWDSs are by nature heterogeneous. Microbiological investigations into site characteristics have shown that there are considerable differences between different SWDSs and even different regions within the same SWDS (Westlake, 1990). This makes it very difficult to extrapolate from observations on single SWDSs to predictions of global CH 4 emissions. Nevertheless, a better understanding of the factors thought to most significantly influence the generation of CH 4 from land disposal of solid waste can reduce the uncertainty associated with emissions estimates.



### 6.2.3 Factors Influencing Methane Generation in Solid Waste Disposal Sites This section will provide a brief summary of the most significant factors affecting CH 4 generation. Waste disposal practices Waste disposal practices of concern for CH 4 emissions vary in the degree of control of the placement of waste and management of the site. In general, waste disposal on land will result in CH 4 production if the waste contains organic matter. Managed disposal (controlled placement of waste), in particular, tends to encourage development and maintenance of anaerobic activity. Waste composition The composition of waste is one of the main factors influencing both the amount and the extent of CH 4 production within SWDSs. Municipal solid waste (MSW) typically contains significant quantities of degradable organic matter. Different countries and regions are known to have MSW with widely differing compositions. Physical factors Moisture content is an important physical factor influencing landfill gas production. Moisture is essential for bacterial growth and metabolism, as well as for transport of nutrients and bacteria within the SWDS. The moisture content of a SWDS depends on

## W ASTE

6.4 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual the initial moisture content of the waste, the extent of infiltration from surface and groundwater sources, and the amount of water produced during the decomposition processes. Temperature, pH, and nutrient availability will affect the growth rate of the bacteria. Under anaerobic conditions, landfill temperatures are generally between 25-40 o C. These temperatures can be maintained within the SWDS regardless of the ambient surface temperatures. Outside of these temperatures, CH 4 production is reduced. Optimal pH for CH 4 production is around neutral (pH 7.0). Important nutrients for efficient bacterial growth include sulphur, phosphorus, sodium and calcium. The significance of these physical factors to CH 4 generation can be demonstrated within controlled laboratory conditions.



### 6 . 2 . 4 M e t h o d o l o g i e s t o E s t i m a t e M e t h a n e Emissions from Solid Waste Disposal Sites
A number of methods have been used to estimate CH 4 emissions from solid waste disposal sites. These methods vary widely, not only in the assumptions that they make, but also in their complexity, and in the amount of data they require. This chapter will deal only with those methods that can be applied to whole regions or countries. There are some very complex models that are concerned with movement of CH 4 and other gases through individual disposal sites; however these models cannot be applied to site populations and therefore will not be considered further here. The methods described below include the theoretical gas yield methodology, of which the default methodology is one variation, and a first order kinetics methodology. Theoretical gas yield methodology This is the simplest method for calculating CH 4 emissions from SWDSs. It is based on a mass balance approach, and does not incorporate any time factors into the methodology. Rather, this methodology assumes that all potential CH 4 is released from waste in the year that the waste is disposed of. Although this is not what actually occurs, it gives a reasonable estimate of the current year’s emissions if the amount and composition of the waste disposed of has been relatively constant over the previous several years. If, however, there have been significant changes in the rate of waste disposal, this simple method will likely not provide a good estimate of current emissions. Default methodology The default methodology is a mass balance approach that involves estimating the degradable organic carbon (DOC) content of the solid waste, i.e., the organic carbon that is accessible to biochemical decomposition, and using this estimate to calculate the amount of CH 4 that can be generated by the waste. This is the approach taken by Bingemer and Crutzen (1987), who divided the world into four economic regions (the United States, Canada and Australia; other OECD countries; the Former USSR and Eastern and Central Europe; developing countries), and applied different DOC values tothe waste generated within each of these regions. It is the most widely accessible, easyto-apply methodology for calculating country-specific emissions of CH 4 from SWDSs. It requires the least amount of data to perform the calculations, and it can be modified and refined as the amount of data available for each country increases. This approach was provided as the default methodology in the IPCC Guidelines (IPCC, 1995). The revised default methodology provided here modifies the IPCC Guidelines (IPCC, 1995) in three important ways:

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.5 • Rather than distinguishing between “landfills” and “open dumps,” the methodology uses a continuum of solid waste disposal sites, characterised by the degree of waste management and depth.

• Default DOC values are provided for different waste streams so that countries can calculate the DOC content of their waste rather than relying on single default values.

• Emphasising the fact that this methodology estimates CH 4 generation rather than emission, and that oxidation often occurs in the upper layers of the waste mass and in site cover material, a CH 4 oxidation factor (OX) is included in the equation (currently equal to 0, pending the availability of further data).
The determination of annual CH 4 emissions for each country or region can be calculated from Equation 1:

E QUATION 1 Methane emissions (Gg/yr)

= (MSW T x MSW F x MCF x DOC x DOC F x F x 16/12 - R) x (1-OX)

where:

MSW T = total MSW generated (Gg/yr)
MSW F = fraction of MSW disposed to solid waste disposal sites MCF = methane correction factor (fraction) DOC = degradable organic carbon (fraction)
DOC F = fraction DOC dissimilated
F = fraction of CH 4 in landfill gas (default is 0.5)
R = recovered CH 4 (Gg/yr) OX = oxidation factor (fraction - default is 0)

Total MSW (MSW T ) can be calculated from Population (thousand persons) x Annual MSW generation rate (Gg/thousand persons/yr). Per capita MSW generation rates are provided for many countries and regions in Table 6-1. The components of MSW may vary from country to country. These differences can play an important role in the resulting emissions estimate, as each waste stream may have a different DOC content and hence a different CH 4 generation potential. In general, countries should include the following waste streams in their estimate of total MSW generated: 1. household waste; 2. yard/garden waste; and
3. commercial/market waste. In some countries, significant quantities of organic industrial solid waste are generated. The default values in Table 6-1 should not include industrial waste or construction and demolition material. If a significant quantity of organic industrial solid waste is generated

## W ASTE

6.6 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual and disposed of in solid waste disposal sites, this waste should be included in the MSW generation rates and reflected in the corresponding DOC value chosen (see below under Degradable Organic Carbon). In countries where no organised waste collection or disposal takes place in rural areas, the population considered should include only the urban population. The default values in Table 6-1 for developing countries and countries with economies-in-transition do not include rural area information.

T ABLE 6-1 C OUNTRY W ASTE G ENERATION , C OMPOSITION , AND D ISPOSAL D ATA Region/Country MSW Generation Rate (kg/cap/day) Fraction of MSW disposed to SWDS Fraction of DOC of

MSW MSW disposal Rate (kg/cap/day)
North America 0.18-0.21
USA a 2.0 0.62 1.24
Canada b 1.81 0.75 1.35
Oceania
Australia c 1.26 1.00 0.15 1.26
New Zealand l 1.33 1.0 0.19 1.33
UK/Western Europe/Scandinavia 0.08-0.19

UK m 1.9 0.9 0.10 1.7
Ireland b 0.85 1.00 0.85
Austria d 0.92 0.40 0.36 Belgium b 1.10 0.43 0.47
Denmark b 1.26 0.20 0.25
Finland b 1.70 0.77 1.3
France b 1.29 0.46 0.60 Germany b 0.99 0.66 0.65
Greece b 0.85 0.93 0.79 Italy e 0.94 0.88 0.83 Luxembourg b 1.34 0.35 0.47
Netherlands f 1.58 0.67 0.14 1.06 Norway b 1.40 0.75 1.05 Portugal b 0.90 0.86 0.78 Spain b 0.99 0.85 0.83
Sweden b 1.01 0.44 0.44
Switzerland b 1.10 0.23 0.25 Eastern Europe
Poland g 0.15 0.54
Russia h 0.93 0.94 0.17 0.87

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.7 T ABLE 6-1 ( CONTINUED ) C OUNTRY W ASTE G ENERATION , C OMPOSITION , AND D ISPOSAL D ATA Region/Country MSW Generation Rate (kg/cap/day) Fraction of MSW disposed to SWDS Fraction of DOC of MSW MSW disposal Rate (kg/cap/day)
Asia Japan b 1.12 0.38 0.43
India i 0.33 0.6 0.18 0.2
China j 0.09 0.84
Indonesia j 0.17 0.51
Central America
Guatemala j 0.13 0.46
South America
Brazil j 0.12 1.47
Peru j 0.15 0.98
Chile j 0.18 0.59
Africa Egypt j 0.21 0.40 Nigeria j 0.11 0.40 South Africa k 1.00 Note: The values in Table 6-1 represent the best data available to the Expert Group. Note that all values may not reflect identical assumptions regarding MSW composition (and hence corresponding DOC values). Where updated national data are available corresponding to the definitions used here, they should be used for comparison instead of the values given in Table 6- 1.

a US EPA, 1995 b OECD, 1995

c Tom Beer, CSIRO, 1996
d Carolin Ziegler, University of Vienna, 1996

e Domenico Gaudioso, ENEA Italy, 1995 f Hans Oonk, TNO Environment & Energy Research, The Netherlands, 1995
g Piotr Manczarski, Warsaw University, Poland, 1995
h Alexander Lifshits, Geopolis Consulting, Moscow, 1995

i A.D. Bhide, NEERI, India, 1995 j Cal Recovery Inc., California, USA - based on experience in country.
k Les Venter, Solid Waste Dept., Johannesburg, South Africa, 1995
l E. Gray, New Zealand Ministry of Environment, 1996

m UK DoE, 1995

The Fraction MSW Disposed to Solid Waste Disposal Sites (MSW F ) and Methane Correction Factor (MCF) reflect the way in which MSW is managed and the effect of management practices on CH 4 generation. The methodology requires countries to provide data or estimates of the quantity of waste that is disposed of to each of three categories of solid waste disposal sites (Table 6-2).

## W ASTE

6.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 6-2 SWDS C LASSIFICATION AND M ETHANE C ORRECTION F ACTORS Type of site Methane correction factor (MCF) default values Managed 1.0 Unmanaged - deep ( ≥ 5m waste) 0.8 Unmanaged - shallow (<5m waste) 0.4 Default value - uncategorised SWDSs 0.6

1. Managed solid waste disposal sites. These must have controlled placement of waste (i.e., waste directed to specific deposition areas and a degree of control of scavenging and a degree of control of fires) and will include at least one of the following:

• cover material;

• mechanical compacting; or

• levelling of the waste.
2. Unmanaged-deep solid waste disposal sites. All SWDSs not meeting the criteria of managed SWDSs and which have depths of greater than or equal to 5 metres.
3. Unmanaged-shallow solid waste disposal sites. All SWDSs not meeting the criteria of managed SWDSs and which have depths of less than 5 metres. A methane correction factor (MCF) is assigned to each of these categories, as shown in Table 6-2. The MCF reflects the lower methane-generating potential of unmanaged sites. The classification recognises that some developing countries or countries with economies-in-transition may have a small number of well-managed waste disposal sites, with the majority of sites less well-managed or unmanaged, often shallow and with lower methane-generating potential. A default value is provided for countries where the quantity of waste disposed to each SWDS is not known. A country’s classification of its waste sites into managed or unmanaged may change over a number of years as national waste management policies are implemented. Degradable Organic Carbon (DOC) content is based on the composition of waste, and can be calculated from a weighted average of the carbon content of various components of the waste stream. Country/region default data for DOC, where available, are presented in Table 6-1 (in general, these values are for wet waste). It is highly recommended, however, for countries where the composition of the fractions in the waste stream are known, that these be combined with a knowledge of the carbon content of these various fractions to produce a country-specific value for DOC. It is critical that the DOC value corresponds to the waste generation/disposal rate on which the CH 4 estimate is based. For example, a country that includes industrial waste in its MSW estimate should ensure that the DOC value used reflects this component of the
waste stream. To assist countries to calculate the DOC of waste streams, a set of default DOC values for different waste types is given in Table 6-3. Note that these values are for wet (or fresh) waste.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.9 T ABLE 6-3 D EFAULT DOC V ALUES FOR M AJOR W ASTE S TREAMS Waste Stream Per cent DOC (by weight) A. Paper and textiles 40 B. Garden and park waste, and other (non-food) organic putrescibles 17

C. Food waste 15

D. Wood and straw waste a 30

a excluding lignin C Source: Bingemer and Crutzen, 1987.

Using the values in Table 6-3, the DOC content of a country’s waste could be calculated as shown in Equation 2.

E QUATION 2 Per cent DOC (by weight) = 0.4 (A) + 0.17 (B) + 0.15 (C) + 0.30 (D)

where: A = per cent MSW that is paper and textiles B = per cent MSW that is garden waste, park waste or other non-food organic putrescibles C = per cent MSW that is food waste D = per cent MSW that is wood or straw

Fraction dissimilated DOC (DOC F ) is the portion of DOC that is converted to landfill gas. To date, estimates of how much carbon may be dissimilated have relied on a theoretical model that varies only with the temperature in the anaerobic zone of a landfill: 0.014T + 0.28, where T = temperature (Tabasaran, 1981). If one assumes that the temperature in the anaerobic zone of a SWDS remains constant at about 35 o C, regardless of ambient temperature (Bingemer and Crutzen, 1987), this method yields a figure of 0.77 dissimilated DOC. This value is currently under review.
Recovered CH 4 (R) is the amount of CH 4 that is captured for flaring or use. No default values are provided for the quantity of CH 4 recovered, as this value is country-specific. See Section 6.2.6 below for more information.
Oxidation Factor (OX) accounts for the CH 4 that is oxidised in the upper layers of the waste mass and in cover material, where oxygen is present. Because the default methodology relies on an estimate of CH 4 generation, it is important to recognise the oxidation may reduce the quantity of CH 4 generated that is ultimately emitted. A number of researchers are investigating and quantifying the effects of CH 4 oxidation in waste disposal sites. However, as yet there is no internationally accepted factor that can be applied to account for CH 4 oxidation. The CH 4 oxidation factor in the equation has therefore been set equal to 0, pending the availability of new data. A better

## W ASTE

6.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual understanding of the factors influencing CH 4 oxidation, and more accurate quantification of it, may allow for a revised oxidation factor (or default values) in future editions of the IPCC Guidelines . It is important that the oxidation factor be applied after subtraction of CH 4 recovered, as this CH 4 is generally pulled from well below the surface of the SWDS, before oxidation can occur. It is proposed that the default methodology, based on the theoretical gas yield methodology developed by Bingemer and Crutzen (1987), remain as the methodology that can be used by all countries to calculate CH 4 emissions from their SWDSs. The Workbook provides a detailed step-by-step version of this methodology. Theoretical first order kinetics methodologies More complex methods for estimating CH 4 emissions from SWDSs acknowledge the fact that CH 4 is emitted over a long period of time rather than instantaneously. A kinetic approach therefore needs to take into account the various factors which influence the rate and extent of CH 4 generation and release from SWDSs. A number of countries have applied this or similar modelling approaches to their own situation (Aitchison et al., 1996; UK, DOE, 1993; Van Amstel et al., 1993; Environment Canada, 1992). First Order Decay Model A first order decay model (Equation 3) can be used to model the rate of CH 4 generation over time. This approach has been used extensively to model landfill gas generation rate curves for individual landfills. It can also be used to model gas generation for a set of SWDSs to develop country emissions estimates or can be applied in a more general way to entire regions.

E QUATION 3 Q = L O R (e -kc - e -kt )

where: Q = methane generated in current year (m 3 /yr)
L 0 = methane generation potential (m 3 /Mg of refuse) R = average annual waste acceptance rate during active life (Mg/yr) k = methane generation rate constant (1/yr) c = time since SWDS closure (yr) t = time since SWDS opened (yr)

Methane generation potential (L o ). The methane generation potential depends upon the composition of the waste. Values for L o can vary widely, and are difficult to estimate accurately for a particular SWDS or set of SWDSs. L o values may range from less than 100 to over 200 m 3 /Mg. Quantity of waste landfilled (R). This is the average annual waste acceptance rate during the SWDS’s active life. Methane generation rate constant (k). This value is based on the environment in which the SWDS is located. Higher k values are associated with greater moisture in the

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.11 SWDSs and other factors discussed in Section 6.2.3 above. Values for k may range from less than 0.005 per year to 0.4 per year (LANDTEC, 1994; US EPA 1991). Time since SWDS closure (c). This is the length of time in years, not including the year of closure, since the SWDS stopped accepting waste. Time since initial refuse replacement (t). This is the length of time in years since the SWDS began to accept waste. Countries with sufficient data on annual waste disposal to SWDSs are encouraged to apply the derivative of the first order decay model (Equation 4), to provide a comparison to the default methodology as well as to test the feasibility of including this approach in future inventories guidelines. To allow for variances in annual acceptance rates, the derivative of Equation 3 with respect to t can be used to estimate CH 4 generation from waste landfilled in a single year (R

x ). In this equation, the variable t is replaced with T-x, which represents the number of years the waste has been in the SWDS. The resulting equation thus becomes:

E QUATION 4 Q T,x = k R x L O e -k(T-x)

where: Q T,x = the amount of methane generated in the current year (T) by the waste R x x = the year of waste input
R

x = the amount of waste disposed in year x (Mg) T = current year

In order to estimate the current emissions from waste placed in all years, Equation 4 can be solved for all values of R x and the results summed (see Equation 5).

E QUATION 5 Q T = Σ Q T,x for x = initial year to T



### 6.2.5 Sources of Uncertainty There are two areas of uncertainty in the estimate of CH 4 emissions from solid waste disposal sites: (1) the uncertainty attributable to the method; and (2) data uncertainty. Uncertainty attributable to the method. As discussed previously, the default methodology assumes that waste disposal into solid waste disposal sites is relatively constant and that the CH 4 generated by the waste is released in the same year the waste is deposited. However, if waste disposal into solid waste disposal sites is increasing over time, then the

## W ASTE

6.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual default method will overestimate CH 4 emissions. For example, it can be shown that if waste disposal into solid waste disposal sites is increasing at about 2 per cent per year over a 20- to 30-year period, then the default method will overestimate emissions by about 20-25 per cent. This is the principal type of uncertainty attributable to the default methodology itself. The amount of waste disposed of is therefore a sensitive parameter in this default methodology. Data uncertainty. This source of uncertainty is simply the uncertainty attributable to each of the data inputs. In the case of the default methodology, this includes the uncertainty in the estimates for each of the factors used in Equation 1 (e.g., total MSW generated, fraction of MSW disposed to solid waste disposal sites). Although the uncertainty in any single one of these factors may be relatively large, if the sources of uncertainty for one factor are not related to the uncertainty for the other factors, then the uncertainty of the overall CH 4 emissions estimate can remain relatively low. For example, if the values for each of the factors used in Equation 1 are assumed to have an uncertainty of ± 10 per cent, then the overall uncertainty in the CH 4 emissions estimate will be about ± 20 per cent. If the uncertainty for each factor increases by ± 20 per cent, then the overall uncertainty in the CH 4 emissions estimate increases to ± 40-50 per cent. The following key uncertainties related to the data are discussed further below:

• The quantity and composition of landfilled waste;

• The quantity of CH 4 that is actually generated from the waste in the SWDS;

• The quantity of CH 4 that is actually emitted to the atmosphere. Waste quantity and composition: The quality of CH 4 emissions estimates is directly related to the quality and availability of the waste management data used to derive these estimates. However, an accurate knowledge of the quantity and composition of wastes already in place may not be available. For most countries, limitations on funds availablewill prevent extensive investigations of old and smaller sites. It is therefore more costeffective to concentrate efforts on improving the quality of data being collected onexisting landfilling operations, including total waste quantity as well as more detailed sitespecific data. Quantity of methane generated: The degradable organic carbon (DOC) content of waste is an essential component in all calculations of CH 4 generated, and small variations in the assumed values for DOC can result in large variations in the overall estimate of CH 4 emissions. Different countries have widely differing MSW compositions and therefore DOC content. Both the rate and the extent of degradation of the various waste fractions need to be taken into account where data are available. Waste management practices also have significant effects on CH 4 generation, for example the method of landfilling and the water management practices. Future changes in waste management practices may change the composition of waste to SWDSs considerably, resulting in different CH 4 emissions levels. Quantity of methane generated that is emitted to the atmosphere: The main uncertainty influencing the quantity of CH 4 emitted is the degree of oxidation that occurs as the gas diffuses through the landfill cover material. The presence, thickness, and other characteristics of SWDS cover materials can play a large role in determining the quantity of CH 4 ultimately emitted from a site.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.13 

### 6.2.6 Flaring and Gas Recovery Schemes Flaring and gas recovery schemes successfully reduce CH 4 emissions from SWDSs. Any national inventory of CH 4 emissions from SWDSs must therefore take into account the reductions achieved by these practices. For sites recovering CH 4 for energy use, the quantity of gas utilised is generally well documented. Estimates of the extent of flaring are more difficult to achieve with accuracy, and generally have to be estimated from a knowledge of the state of SWDS management within the country. If data on gas flaring are not readily available for a country, the following steps might be useful in development of this information: 1. Creation of an inventory of gas flares purchased in the country for use with landfill gas, including year purchased, estimated useful life, and flow rates. 2. Use of this inventory to estimate quantity of landfill gas flared each year.



### 6.2.7 Conclusion A default methodology is presented here that allows simple calculation of CH 4 emissions from SWDSs by all countries. Countries are encouraged to use more sophisticated methods that incorporate country-specific data, if available. In particular, countries with sufficient data are encouraged to apply the first order decay model presented in Section 6.2.4 above, and compare the results to the basic default approach. If such data are not available, countries are encouraged to collect data for future application of a first order methodology. The additional information required includes: i) the CH 4 generation potential of the waste; ii) the rate at which CH 4 is generated from the waste each year; iii) the year of waste input; and iv) the amount of waste disposed of to SWDSs each year.



## 6 . 3 Met h a n e E m i s s i on s f r om W a s t e wa t e r Handling

6.3.1 Introduction Methane production from wastewater handling (WWH) under anaerobic conditions is estimated to range from 30 to 40 teragrams per year (Tg/yr). This represents 8 to 11 per cent of total global anthropogenic CH 4 emissions estimated at 375 Tg/yr. Industrial WWH sources are estimated to be the major contributor to WWH emissions, accounting for 26 to 40 Tg/yr. Domestic and commercial WWH is estimated to emit approximately 2 Tg/yr (IPCC, 1995; US EPA 1994). Wastewater can produce CH 4 if it is handled anaerobically. Anaerobic methods are used to handle wastewater from municipal sewage and from food processing and other industrial facilities, particularly in developing countries. In contrast, developed countries typically use aerobic processes for municipal wastewater treatment or anaerobic processes in enclosed systems where CH 4 is recovered and utilised. This section provides the default methodology for estimating CH 4 emissions from WWH.

## W ASTE

6.14 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.3.2 Background Handling of wastewater and its residual solids by-product (sludge) under anaerobic conditions results in CH 4 production. The extent of CH 4 production depends primarily on the following factors: A) Wastewater Characteristics The principal factor in determining the CH 4 generation potential of wastewater is the amount of degradable organic material in the wastewater. Common parameters used to measure the organic component of the wastewater are the BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand). Under the same conditions, wastewater with higher COD (or BOD) concentrations will generally yield more CH 4 than wastewater with lower COD (or BOD) concentrations. B) Handling Systems Handling systems vary in the environment that they provide for CH 4 production. Systems that provide anaerobic environments will generally produce CH 4 whereas systems that provide aerobic environments will normally produce little or no methane. For example, the depth of a lagoon treatment system is a critical factor in CH 4 production. Shallow lagoons, less than 1 metre in depth, generally provide aerobic conditions and little CH 4 is likely to be produced. Lagoons deeper than about 2-3 metres will generally provide anaerobic environments and significant methane production is expected. C) Temperature With increases in temperature, the rate of CH 4 production increases. This is especially important in uncontrolled systems and in warm climates. CH 4 production typically requires a temperature higher than 15°C. Fermentation and thus CH 4 production is negligible at temperatures below 15°C, at which point the lagoon serves principally as a sedimentation tank (Gloyna, 1971). Below 15°C significant amounts of CH 4 will be produced only in instances where sedimentation and extended sludge retention occur.
Other factors that influence CH 4 generation in wastewater are retention time, degree of wastewater treatment, and other site specific characteristics. D) BOD vs. COD
The BOD (Biochemical Oxygen Demand) concentration indicates only the amount of carbon that is aerobically biodegradable. The standard measurement for BOD is a 5-day
test 1 , denoted as BOD 5 . The time period used in the BOD indicates whether only easily biodegradable materials or more resistant compounds are taken into account. COD (Chemical Oxygen Demand) measures the total material available for oxidation (both biodegradable and non-biodegradable). Since the BOD is an aerobic parameter, it may be less appropriate for determining the organic components in anaerobic environments. Also, both the type of wastewater and the type of bacteria present in the wastewater influence the BOD concentration of the wastewater. Although BOD is the more

1 A seven day test, denoted as BOD 7 , is used in some countries instead of BOD 5 . The conversion between BOD 5 and BOD 7 is dependent on the characteristics of the wastewater. Experts within individual countries should be consulted to obtain appropriate conversion coefficients.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.15 frequently reported parameter, reported COD/BOD ratios can be used to determine the COD if the BOD is known. 2



### 6.3.3 Methodology for Wastewater Handling Wastewater handling systems involve processes that transfer wastewater from its source to a disposal site. In most developed countries, wastewater treatment systems are used to chemically or biologically stabilise the wastewater before disposal. In many developing countries however, wastewater receives little or no formal treatment and is simply handled by transporting untreated wastewater to a disposal site. Formal wastewater treatment methods can be classified as primary, secondary, and tertiary treatment. In primary treatment, physical barriers remove larger solids from the wastewater. Remaining particulates are then allowed to settle. Secondary treatmentconsists of a combination of biological processes that promote biodegradation by microorganisms. These may include aerobic and anaerobic stabilisation ponds, trickling filters, and activated sludge processes. Tertiary treatment processes are used to further purify the wastewater of contaminants and pathogens. This is achieved using one or a combination of processes, including maturation/polishing ponds, advanced filtration, carbon adsorption, ion exchange, and disinfection. Sludge is produced in both the primary and secondary stages of treatment. Sludge that is produced in primary treatment consists of solids that are removed from the wastewater. Sludge produced in secondary treatment is a result of biological growth in the biomass, as well as the collection of small particles (Lexmond and Zeeman, 1995). This sludge must be treated further before it can be safely disposed of. Methods of sludge treatment include aerobic and anaerobic stabilisation (digestion), conditioning, centrifugation, composting, and drying. Anaerobic stabilisation will produce CH 4 .


### 6 . 3 . 4 W a s t e w a t e r H a n d l i n g M e t h o d s i n Developed and Developing Countries Wastewater handling methods differ between developed and developing countries. The most common methods of wastewater handling in developed countries are aerobic wastewater treatment plants and lagoons (Lexmond and Zeeman, 1995). To avoid high discharge fees, many large industrial facilities pretreat their wastewater before releasing it into the sewage system. There is also an increasing trend towards anaerobic treatment systems, which can be cheaper and produce less sludge than aerobic systems. The degree of wastewater treatment is variable in most developing countries. Most industrial wastewater is discharged directly into local bodies of water, and only a few major industries have comprehensive in-plant treatment facilities. Less than half of municipal wastewater produced is collected in a sewage system. Collected wastewater is usually discharged into unmanaged lagoons or waterways; in coastal cities it is discharged directly into the ocean. In many cases, the domestic wastewater handling facilities are pit

2 Lexmond and Zeeman estimated a minimum value of the wastewater COD/BOD ratio to be 1.70 (Lexmond and Zeeman 1995). The COD/BOD ratio may vary significantly depending upon the characteristics of the wastewater. This is especially true for industrial wastewater which may include inorganic oxidisable materials. Some countries report BOD 7 (or other) values rather than BOD 5 values. In this case, domestic wastewater experts should be consulted to convert the available BOD data into the BOD 5 form.

## W ASTE

6.16 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual latrines. Table 6-4 presents the main wastewater handling methods in developed and developing countries.
Wastewater streams Wastewater originates from a variety of domestic and industrial sources. Domestic wastewater streams include wastewater from toilets, bathrooms, kitchens, and in some cases, urban run-off. Industry classifies sources of wastewater into different industrial sectors (Lexmond and Zeeman, 1995), for example:

• Food and Beverages

• Paper and Pulp

• Textile

• Petrochemical

• Fertiliser

• Iron and Steel

• Non-Ferrous Metals

• Miscellaneous
Assessment of CH 4 production potential from industrial wastewater streams is based on the concentration of degradable organic matter in the wastewater, the volume of wastewater, and the propensity of the industry to treat their wastewater in anaerobic lagoons. Using these criteria, Doorn and Eklund (1995) prioritised industrial wastewater sources with high CH 4 gas production potential. These are characterised as follows:

• Paper and Pulp manufacture

• Slaughterhouses

• Alcohol, Beer, Starch

• Organic Chemicals

• Others (vegetable oil production, textiles, rubber, petroleum refineries, fruits and vegetables) Both the paper and pulp industry and the meat and poultry processing industries produce large volumes of wastewater that contain high levels of degradable organics. Additionally, both industries utilise large facilities that often have their own wastewater handling systems. The meat and poultry processing facilities commonly employ anaerobic lagoons to treat their wastewater, while the paper and pulp industry is known to use lagoons. The non-animal food and beverage industries collectively produce considerable amounts of waste water with significant BOD levels.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.17 T ABLE 6-4 M ETHODS OF W ASTEWATER H ANDLING Handling Method Exceptions to Expected CH 4 Production Mostly aerobic disposal and handling methods (little or no CH 4 production) Developing countries • Open Pits/Latrines

• Aerobic shallow ponds

• River Discharge • Pits/latrines may produce methane when temperature and retention time are favourable • Aerobic shallow ponds over 3 metres deep may produce methane • Stagnant, oxygen-deficient rivers may allow for anaerobic decomposition Developed countries • Sewer systems with aerobic treatment • Poorly designed or managed aerobic treatment systems produce methane Mostly anaerobic disposal and handling methods (high CH 4 production) Developing countries • Anaerobic deep ponds • Sewer systems with anaerobic treatment

Developed and developing countries • Septic Tanks • Poorly designed or managed anaerobic systems may allow for aeration and reduced methane production

• Frequent solids removal reduces methane production Anaerobic Methods with Methane Recovery (mainly for sludge handling) Primarily developed countries



### 6.3.5 Methodology for Estimating Emissions from Wastewater Handling Methane emissions from wastewater handling should be calculated for two different wastewater and resulting sludge types:

1 Domestic Wastewater.
2 Industrial Wastewater. 3 Domestic Sludge. 4 Industrial Sludge. For each category, the method for estimating CH 4 emissions from wastewater handling requires three basic steps:

## W ASTE

6.18 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Step 1 - Determine the total amount of organic material in the wastewater produced for each wastewater handling system. The principal factor in determining the CH 4 generation potential of wastewater is the amount of degradable organic material of the wastewater. The most common parameters used to measure the degradable organic component (DC) of the wastewater are the BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand). Data permitting, COD is the recommended parameter for estimating the DC of wastewater. The DC indicator, usually indicated in units of mass DC per unit volume (e.g., kg COD per m 3 wastewater) is multiplied by the volume of the source of wastewater (e.g., industry or domestic) to estimate the total amount of organic wastewater produced. Step 2 - Estimate emissions factors for each wastewater handling system in kg CH 4 per kg DC. The emissions factors depend on the fraction of wastewater managed by each wastewater handling method, maximum CH 4 producing capacity of the wastewater, and the characteristics of the wastewater handling process (principally, the degree to which it is anaerobic). Step 3 - Multiply the emissions factors for each wastewater handling system by the total amount of organic material in the wastewater produced for each system , and sum across the wastewater systems to estimate total CH 4 emissions. Approach for Estimating Methane Emissions from Wastewater and Wastewater Sludge Handling This approach is adapted from Doorn and Ecklund (1995) and Lexmond and Zeeman (1995). Step 1 -Total Organic Wastewater and Sludge The greenhouse gas (GHG) generation potential of the wastewater is driven by the organic content of the wastewater stream and the volume of wastewater. For the categories of wastewater types defined (domestic and industrial), the following is the method for estimating the total organic wastewater (TOW):
Domestic
Data needed are: 1. Degradable organic component (DC) indicator in kg DC per 1000 persons per year. For domestic wastewater and sludge, BOD is the recommended DC indicator. Although COD is considered a more appropriate indicator for the organic component of the waste, BOD is the more frequently reported indicator for domestic wastewater. Consequently, the use of BOD estimates will result in more precise calculations than when COD is used. (Default BOD values are provided for different regions in Table 6-5). 2. Country population in thousands (developing countries may choose to estimate wastewater and sludge handling emissions based only on the urban population of the country if wastes produced in rural areas decompose in an aerobic environment - see Table 6-4 for a list of anaerobic and aerobic handling methods). 3. Fraction of BOD removed as sludge. Equation 6 presents the total domestic organic wastewater (TOW dom ) calculation.

E QUATION 6 TOW dom = P x D dom x (1 - DS dom )

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.19 Equation 7 presents the total domestic organic sludge (TOS dom ) calculation.

E QUATION 7 TOS dom = P x D dom x DS dom

where:
TOW dom = total domestic/commercial organic wastewater in kg BOD/yr
TOS dom = total domestic/commercial organic sludge in kg BOD/yr P = population in 1000 persons
D dom = domestic/commercial degradable organic component in kg BOD/1000 persons/yr
DS dom = fraction of domestic/commercial degradable organic component removed as sludge

Industrial
Data needed are: 1. Degradable organic component (DC) indicator in kg DC per m 3 of industrial wastewater/sludge produced per unit product. For industrial wastewater and sludge
streams COD is the appropriate DC indicator. Data on COD values should be available in most countries. It is recommended that country-specific information, if available, be used. Default COD values are provided for different industries by region in Table 6-6. (Although the default values in Table 6-6 are provided by region, in most cases the default values are based on estimates for a single country within each region.) 2. Wastewater produced per unit product by industry in m 3 /tonne of product. Default values are provided in Table 6-6. (Although the default values in Table 6-6 are provided by region, in most cases the default values are based on estimates for a single country within each region.) 3. Total industrial output in tonnes per year. 4. Fraction of COD removed as sludge. Equation 8 presents the total organic wastewater (TOW ind ) calculation for a particular industry.

E QUATION 8 TOW ind (kg COD/yr) = W x O x D ind x (1 - DS ind )

## W ASTE

6.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Equation 9 presents the total organic sludge (TOS ind ) calculation for a particular industry.

E QUATION 9 TOS ind (kg COD/yr) = W x O x D ind x DS ind

where:
TOW ind = total industrial organic wastewater in kg COD/yr
TOS ind = total industrial organic sludge in kg COD/yr
W = wastewater consumed in m 3 /tonne of product O = total output by selected industry in tonnes/yr
D ind = industrial degradable organic component in kg COD/m 3
wastewater DS ind = fraction of industrial degradable organic component removed as sludge

Step 2 - Emissions Factors To calculate emissions factors for each wastewater and sludge type, a weighted average of methane conversion factors (MCF) is calculated using estimates of wastewater managed by each wastewater handling method. The average MCF is then multiplied by the maximum methane producing capacity (B o ) of the wastewater type.

• Maximum methane producing capacity (B o ) : The methane producing potential, B o , is the maximum amount of CH 4 that can be produced from a given quantity of wastewater or sludge. The CH 4 producing potential varies by the composition of the wastewater/sludge and its degradability. The default (theoretical) value for B o is 0.25 kg CH 4 /kg BOD for wastewater and for sludge (Lexmond et al., 1995). 3

• Fraction of wastewater treated by certain handling systems (WS% ): These are the fractions of wastewater treated by a specific handling system, i.e., aerobic or anaerobic. Country specific estimates for WS should be used where available. Default estimates of WS per cent for different countries are provided in Table 6-7 to 6-9

.

• Fraction of sludge treated by certain handling systems (SS% ): These are the fractions ofsludge treated by a specific handling system, i.e., aerobic or anaerobic. Countryspecific estimates for SS should be used where available.

• Methane conversion factor: The amount of methane that is actually emitted depends on the CH 4 conversion factor. The MCF defines the portion of CH 4 producing potential (B o ) that is achieved. The MCF varies between 0.0 for a completely aerobic system to 1.0 for a completely anaerobic system. Countries should contact wastewater experts to

3 B o is expressed in units of kg CH 4 /kg DC, where DC is the indicator of degradable component of the waste (either COD or BOD). By definition, BOD is less than or equal to COD; the maximum BOD possible is, in fact, the COD. Therefore, when estimating the maximum CH 4 producing potential from BOD or COD, the maximum potential CH 4 produced per unit of BOD is equivalent to the maximum potential CH 4 produced per unit of COD. This value is 0.25 kg CH 4 /kg COD.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.21 determine MCFs. If no data are available, as a default, use 0 for aerobic systems, and 1.0 for anaerobic

. 4 Since aerobic and anaerobic handling are the only handling systems considered, the CH 4 conversion rate can be used to characterise a broad range of systems falling between aerobic and anaerobic handling systems. Equation 10 presents the emission factor calculation for wastewater:

E QUATION 10
EF i = B oi x ∑ (WS ix x MCF x )

where:
EF i = emission factor (kg CH 4 /kg DC) for wastewater type (e.g., fertiliser industry, domestic, etc.)
B oi = maximum methane producing capacity (kg CH 4 /kg DC) for wastewater type i
WS ix = fraction of wastewater type i treated using wastewater handling system x MCF x = methane conversion factors of each wastewater system x

Equation 11 presents the emission factor calculation for sludge:

E QUATION 11
EF j = B oj x ∑ (SS jyx MCF y )

where:
EF j = emission factor (kg CH 4 /kg DC) for sludge type j (e.g., fertiliser industry wastewater, domestic wastewater, etc.)
B oj = maximum methane producing capacity (kg CH 4 /kg DC) for sludge type j
SS jy = fraction of sludge type j treated using sludge handling system y
MCF y = methane conversion factors of each sludge handling system y (See footnote 4)

4 If sludge is disposed of in landfills then the resulting emissions are already accounted for in the IPCC/OECD SWDS emission methodology (Section 6.2.4). If sludge is incinerated or burned as part of an energy recovery system, then the resulting emissions should be reported for in the Energy Chapter, classified as an industrial waste fuel. In these cases, to ensure that emissions are not counted twice an “MCF” of zero should be used in this methodology for sludge disposed in SWDSs or incinerated, or burned as part of an energy recovery system. In all other cases, an appropriate MCF value should be selected based on the specific characteristics of the system used to dispose of the sludge.

## W ASTE

6.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Step 3 - Wastewater Emissions To estimate total emissions from wastewater, the selected emissions factors are multiplied by the associated organic wastewater production and summed. Subtract the amount of CH 4 , if any, that is recovered and thus not emitted into the atmosphere for each handling method. If no data are readily available, the default assumption is that this amount is zero. Sum the results for each handling method to determine total CH 4 emissions from wastewater. In equation form, the estimate of total CH 4 emissions from wastewater handling is as follows:

E QUATION 12
WM = Σ i (TOW i x EF i - MR i )

where: WM = total methane emissions from wastewater in kg CH 4 TOW i = total organic waste for wastewater type i in kg DC/yr. For domestic streams, the DC is BOD; for industrial streams it is the COD (Step 1)
EF i = emission factor for wastewater type i in kg CH 4 /kg DC (Step 2)
MR i = total amount of methane recovered or flared from wastewater type i in kg CH 4 . If no data are available, use the default value of zero

Step 4 - Sludge Emissions To estimate total emissions from sludge, the selected emissions factors are multiplied by the associated organic sludge production and summed. Subtract the amount of CH 4 , if any, that is recovered and thus not emitted into the atmosphere for each handling method. If no data are readily available, the default assumption is that this amount is zero. Sum the results for each handling method to determine total CH 4 emissions from wastewater. In equation form, the estimate of total CH 4 emissions from sludge handling is as follows:

E QUATION 13 SM = ∑ j (TOS j x EF j - MR j )

where: SM = total methane emissions from sludge in kg CH 4 TOS j = total organic waste for sludge type j in kg DC/yr. For domestic streams, the DC is BOD; for industrial streams it is COD (Step 1)
EF j = emission factor for sludge type j in kg CH 4 /kg DC (Step 2)
MR j = total amount of methane recovered or flared from sludge type j in kg CH 4 . If no data are available, the default is zero

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.23 Step 5 - Total Emissions Total emissions from wastewater and sludge can be determined by summing the results of Steps 3 and 4. This is expressed as follows in Equation 14:

E QUATION 14 TM = WM + SM

where: TM = total methane from wastewater and sludge handling in kg CH 4 WM = total methane emissions from wastewater in kg CH 4 SM = total methane emissions from sludge in kg CH 4



### 6.3.6 Uncertainties The quality of CH 4 emissions estimates for wastewater handling is directly related to the quality and availability of the waste management data used to derive these estimates. Country specific data on wastewater quantities, characteristics, and wastewater management methods are very limited. The principal sources of uncertainty are described below. Organic Wastewater Quantity and Composition Often the amount of degradable organic wastewater that is produced and the volumes handled in the various systems is not well known. Consequently, limitations exist for quantifying the fraction of wastewater subject to specific systems. Physical and Chemical Data Country-specific data on wastewater characteristics are very limited. For example, reported organic component values in industrial source categories are averages from several processes. Accurate and detailed data on the chemical characteristics and volumes of process wastewater streams could improve the emissions estimates. Wastewater Handling Facility Efficiency and Output Aerobically treated wastewater by handling plants may be subject to anaerobic conditions due to poorly managed and functioning facilities. This contributes to an underestimate of emissions. Additionally, current estimates from wastewater handling lagoons are relatively uncertain due to the limited available data. Work is on-going to develop better emission factors from these sources.

T ABLE 6-5 E STIMATED BOD 5 V ALUES IN D OMESTIC W ASTEWATER BY R EGION Region BOD 5 Value (kg/cap/day) BOD 5 Value (kg/1000 persons/yr) Africa 0.037 13,505 Asia, Middle East, Latin America 0.04 14,600 N. America, Europe, Former USSR, Oceania 0.05 18,250 Source: IPCC (1994)

## W ASTE

6.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 6-6 I NDUSTRIAL W ASTEWATER D ATA BY R EGION Industry Type and Region Wastewater Produced (m 3 /tonnes of

product) COD Value (kg COD/m 3 wastewater) Country

Beverage - Distilled & Industry Generic - ethanol 13 m 3 / m 3 ethanol 40 Generic - ethanol NAV 5,000 kg/ m 3 ethanol South America NAV 22 Brazil Western Europe NAV 4.0 - 5.0 Netherlands Beverage - Malt & Beer Generic 5 m 3 / m 3 beer 17 Generic 5-9 m 3 / m 3 beer 2.0 - 7.0 Western Europe NAV 1.0 - 1.5 Netherlands Food - Meat & Poultry Generic 1.4 m 3 /animal NAV Western Europe NAV 2.9 Netherlands North America NAV 15.0 USA Food - Fish North America NAV 2.5 USA Food - Coffee North America NAV 3.0 - 14.0 USA Food - Dairy Products Generic 2.8 NAV Western Europe NAV 1.5 Netherlands Food - Fruits & Vegetables Generic (cannery) 26 NAV Generic Tomato processing 26 NAV North America, potatoes NAV 3.0 USA Western Europe, bean blanching NAV 5.2 Netherlands Western Europe, sauerkraut NAV 10.0 - 20.0 Netherlands Food - Oils Generic - Vegetable oil 1.6 0.3 Middle East NAV 42 Turkey Asia NAV 25 Malaysia Food - Sugar Central America (cane) NAV 98 Mexico Iron And Steel South America 0.1 NAV Brazil Organic Chemicals Western Europe NAV 20- 40 Netherlands Pharmaceuticals Middle East NAV 1.3 Egypt

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.25 T ABLE 6-6 (C ONTINUED ) I NDUSTRIAL W ASTEWATER D ATA BY R EGION Industry Type and Region Wastewater Produced (m 3 /tonnes of

product) COD Value (kg COD/m 3 wastewater) Country

Starch Generic, potato starch NAV 4.0 - 16 Generic, wheat starch NAV 2.0 - 42 Generic, corn starch NAV 10 Petroleum Production North America NAV 0.3 -0.4 USA North America NAV 1.8 Canada Pulp & Paper Generic (pulp) 58 2.0 - 15 North America pulp mill 140 NAV USA Generic (paper) NAV 2.0 - 8.0 North America (virgin paper) 97 1.6 USA North America (recycled paper) 44 3.0 USA Western Europe (paper) NAV 1.0 - 3.0 Netherlands Textiles Rayon 501 NAV Greece NAV 0.09 North America, textile mills NAV 1.0 USA Leather Tanning North America, generic NAV 5.8 USA Source: Doorn and Eklund (1995). For a detailed list of references for each wastewater category, see Doorn and Eklund (1995). Wastewater production of COD values are not available (NAV) for every country and region. Research is ongoing to develop wastewater production and COD values for these countries and regions. Note that these data are currently undergoing revision and updating.

T ABLE 6-7 D OMESTIC W ASTEWATER T REATMENT E MISSIONS F ACTOR D ERIVATION D ATA Region Type of Treatment Fraction of Wastewater Treated

(%) MCF (%)

Africa Kenya Lagoons 50 NAV Tunisia Lagoons 20 NAV Zimbabwe Activated Sludge 50 NAV Other Africa Lagoons 5 80 Asia Indonesia not specified 1 NAV Singapore not specified 1 NAV South Korea not specified 1 NAV Taiwan not specified 1 NAV Other Asia not specified 5 75 Latin America And Caribbean not specified 10 80 Australia And New Zealand not specified 80 70 Source: Doorn and Eklund (1995). For a detailed list of references for each region, see Doorn and Eklund (1995). Methane correction factor (MCF) data are not available (NAV) for some countries and regions. Research is ongoing to provide MCF estimates for these countries and regions. Note that these data are currently undergoing revision and updating.

## W ASTE

6.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual T ABLE 6-8 I NDUSTRIAL W ASTEWATER T REATMENT E MISSIONS F ACTOR D ERIVATION Region Type of Industry Type of Treatment Fraction of Wastewater Treated

(%) MCF (%)

Africa Kenya textiles Lagoons 60 NAV Kenya coffee production Lagoons 5 NAV

Other Africa All Lagoons 10 90
Asia Indonesia All not specified 10 NAV Malaysia palm oil not specified 90 NAV Singapore All not specified 10 NAV South Korea All not specified 10 NAV Taiwan All not specified 10 NAV Thailand breweries activated sludge 50 NAV Other Asia All not specified 20 90
North America Canada All not specified 90 70 USA All not specified 90 70
Latin America & Caribbean All not specified 20 90
Australia & New Zealand All not specified 95 70 Source: Doorn and Eklund (1995). For a detailed list of references for each region, see Doorn and Eklund (1995). Methane correction factor (MCF) data are not available (NAV) for some countries and regions. Research is ongoing to provide MCF estimates for these countries and regions. Note that these data are currently undergoing revision and updating.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.27 T ABLE 6-9 U NSPECIFIED W ASTEWATER T YPE E MISSIONS F ACTOR D ERIVATION D ATA Region Type of Treatment Fraction of Wastewater

Treated

(%) MCF (%)

Africa South Africa not specified 10 NAV Asia Afghanistan not specified 1 NAV Latin America And Caribbean Colombia Lagoons 3 NAV Argentina Lagoons 3 NAV Europe Albania not specified 1-92 NAV Austria not specified 65 NAV Belgium not specified 85 NAV Bulgaria not specified 10-100 NAV Belarus not specified 10-80 NAV Croatia not specified 57 NAV Czech Rep not specified 10-5 NAV Denmark not specified 90 NAV Estonia not specified 10-80 NAV Finland not specified 68 NAV France not specified 50-85 NAV Germany not specified 90 NAV Hungary not specified 44 NAV Ireland not specified 66 NAV Italy not specified 92 NAV Latvia not specified 10-80 NAV Lithuania not specified 10-80 NAV Moldavia not specified 10-80 NAV Netherlands not specified 90 NAV Norway not specified 94 NAV Poland not specified 10-50 NAV Portugal not specified 42 NAV Romania not specified 10-46 NAV Russia not specified 10-80 NAV Serbia not specified 57 NAV Slovenia not specified 87 NAV Spain not specified 67 NAV Sweden not specified 98 NAV Switzerland not specified 88 NAV Turkey not specified 38 NAV Ukraine not specified 10-80 NAV United Kingdom not specified 90 NAV Slovakia not specified 10-65 NAV Source: Doorn and Eklund (1995). Methane correction factor (MCF) data are not available (NAV). Research is ongoing to provide MCF estimates for these and other wastewater treatment systems. Note that these data are currently undergoing revision and updating.

## W ASTE

6.28 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 6.4 Nitrous Oxide from Human Sewage

Since N 2 O emissions from human sewage are closely linked to the agricultural N cycle, the method is further discussed in the Agriculture Chapter. For a detailed description of the proposed methodology, the reader is referred to Section 4.5.4 (on indirect N 2 O emissions from nitrogen used in agriculture).
The emissions of N 2 O from human sewage are calculated as follows:

EQUATION 15 N 2 O (S) = Protein x Frac NPR x NR PEOPLE x EF 6

where:
N 2 O (s) = N 2 O emissions from human sewage (kg N 2 O-N/yr) Protein = annual per capita protein intake (kg/person/yr)
NR PEOPLE = number of people in country
EF 6 = emissions factor (default 0.01 (0.002-0.12) kg N 2 O-N/kg sewageN produced) (See Table 4-18 in Agriculture Chapter)
Frac NPR = fraction of nitrogen in protein (default = 0.16 kg N/kg protein) (See Table 4-19 in Agriculture Chapter)



## 6.5 Emissions from Waste Incineration

6.5.1 Introduction Waste incineration like other types of combustion, is a source of GHG emissions. Few data have been compiled on the global emissions from waste incineration. Preliminary indicators are that this source represents a small percentage of the total GHG output from the waste source category.



### 6.5.2 Emissions Certainly waste incineration produces CO 2 , but it is difficult to identify the portion which should be considered net emissions. A large fraction of the carbon in waste combusted (e.g., paper, food waste) is derived from biomass raw materials which are replaced by regrowth on an annual basis. These emissions should not be considered net anthropogenic CO 2 emissions in the IPCC Methodology. If the agricultural or forestry sources are not being sustainably managed, net CO 2 emissions (equivalent to reductions in biomass stocks) should be accounted for in those source categories. On the other hand, some carbon in waste is in the form of plastics or other products based on fossil fuel. Combustion of these materials, like fossil fuel combustion, releases net CO 2 emissions. In estimating emissions from waste incineration, the desired approach is to separate carbon in the incinerated waste into biomass and fossil fuel based fractions. Only the fossil based portion should be considered net carbon emissions. Any such detailed analysis should ensure that carbon emissions are not double counted in the treatment of stored carbon under energy emissions. See Overview to the IPCC Guidelines

.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.29 A recent Belgian analysis (Debruyn and Van Rensbergen, 1994) offers an example of a very detailed approach. Other relevant gases released from combustion are net GHG emissions. Methane emissions from waste incineration are highly uncertain. An expert working group recognised waste incineration as a source of methane production, but was not able to give global estimates or default emissions factors. Although this source is considered to be relatively small compared to the other CH 4 sources in waste, it was recognised as an area for further research in the future (Berdowski et al., 1993).
Recent studies have also shown that N 2 O may be an important GHG produced from incineration. Table 6-10 provides data from studies of several incineration plants and the N 2 O produced from the waste incineration (de Soete, 1993). Studies in Belgium (IPCC, 1993), Japan (Tanaka et al., 1992) and Norway (Rosland, 1993) have estimated N 2 O production from their waste incineration processes. It has also been found that the emission level depends on the nature of the waste burned. Research in Japan has noted that while all types of incineration produce N 2 O, sludge incinerators produce the highest emissions rates (Tanaka et al., 1992). Traditional air pollutants from combustion - NO x , CO, NMVOC - are characterised in existing emissions inventory systems. The IPCC does not provide a new methodology for these gases, but recommends that national experts use existing published methods. Some key examples of the current literature providing methods are: Default Emission Factor Handbook (CORINAIR, 1994), as well as the US EPA's Compilation of Air Pollutant Emissions Factors (AP-42) (US EPA, 1985) and Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory (Stockton and Stelling, 1987).

T ABLE 6-10 N ITROUS O XIDE E MISSIONS FROM W ASTE I NCINERATION

N 2 O Emission
Nature of Waste (reference) Facility T o C ppmv a min. ppmv a average ppmv a

max. O 2 (%) g N 2 O /
tonne waste Municipal refuse 10 furnaces (65-300 tonnes/day) 1.2 8 18 Municipal refuse Stepgrate Stepgrate Fluid. bed 780-880 780-980 830-850 0.8 4 6.7 4.9 24 10.5 10 8-14 13-15 11-43 40-220 14-123 Municipal solid waste 5 stokers (20-400 tonnes/day) 3 7 12 26-270 3 Fluid. bed 5.6 9.8 17.1 97-293 rot. koln (120 tonnes/day) 10.2 11.1 12.1 35-165 Sewage-sludge 4 incin. (150-300 tonnes/day) 57 87 125 Sludge Rotary grate Fluid. bed Fluid. bed Fluid. bed Fluid. bed 750 770-812 838-854 834-844 853-887 270 135 100 45 50.7 600 292 320 145 227 580-1528 684-1508 275-886 101-307
Source: de Soete, 1993.
a ppmv = parts per million by volume

## W ASTE

6.30 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

## 6.6 References Aitchison, E.M, M.P. Meadows, M.J. Wenborn, I.T. Marlowe, M. Mikkelson, M. Milton, C. Harries and R. Pocock (1996) ‘’ A Methodology for Updating Routinely the Annual Estimate of Methane Emissions from Landfill Sites in the UK. ‘’ ETSU, AEA Technology, Report RYWA/18678001/R4. Berdowski, J.J.M., L. Beck, S. Piccot, J.G.J. Oliver and C. Veldt (1993), “Working Group Report: Methane emissions from fuel combustion and industrial processes.” In: Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control . A.R. van Amstel (ed.), RIVM Report No. 481507003, Bilthoven, The Netherlands, pp. 231-237. Bingemer, H.G. and P.J. Crutzen (1987), “The production of methane from solid wastes.” Journal of Geophysical Research, 92 (D2): 2181-2187. CORINAIR, 1994. Technical Annexes Volume 2 - Default emission factors handbook EUR Report 12586, Office for Official Publications of the European Communities, Luxembourg. (Originally published in 1992 by EEATF.) Debruyn W. and J. Van Rensbergen (1994), Greenhouse Gas Emissions from Municipal and Industrial Wastes, ENE.RA9410, VITO, Energy Division, Belgium. de Soete, G. (1993), “Nitrous oxide from combustion and industry: chemistry, emissions, and control”, pp. 324-325. Working Group Report: Methane Emissions from Biomass Burning. In : Proceedings of an International IPCC Workshop on Methane and Nitrous Oxide: Methods in National Emissions Inventories and Options for Control

. A.R. van Amstel (ed.), RIVM Report No. 481507003, Bilthoven, The Netherlands. Doorn, M. and M.A. Barlaz (1995), Estimate of Global Methane Emissions from Landfills and Open Dumps. Prepared for US EPA Office of Research and Development, February 1995, EPA-600/R-95-019. Doorn, M. and B. Eklund (1995), Greenhouse Gases from Wastewater Treatment: Collection and Review of Country-Specific Data and Preliminary Emission Models . Prepared for US EPA Office of Research and Development, EMEP/CORINAIR (1996), Joint Atmospheric Emission Inventory Guidebook (1st edition). Environment Canada (1992), Canada's Greenhouse Gas Emissions: Estimates for 1990

. Report EPS 5/AP/4. Gloyna, E.F. (1971), Waste Stabilization Ponds. World Health Organization, Geneva, Switzerland. IPCC (1992), Climate Change 1992. The Supplementary Report to the IPCC Scientific Assessment . (J.T. Houghton, G.J. Jenkins and J.J. Ephraums (eds)). Published for The Intergovernmental Panel on Climate Change (IPCC), World Meteorological Organization/United Nations Environment Programme, Cambridge University Press, UK. IPCC (1993), Parts I & II: National GHG Inventories: Transparency in Estimation and Reporting . Part III: Preliminary IPCC National GHG Inventories: In-Depth Review. Prepared by The Intergovernmental Panel on Climate Change (IPCC) and Organisation for Economic Co-operation and Development, World Meteorological Organization/United Nations Environment Programme. IPCC (1994), “ IPCC Guidelines for National Greenhouse Gas Inventories, 3 Volumes: Volume 1, Reporting Instructions; Volume 2, Workbook; Volume 3, Draft Reference Manual.” Intergovernmental Panel of Climate Change.

## 6 W ASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 

### 6.31 IPCC (1995), “ IPCC Guidelines for National Greenhouse Gas Inventories, 3 Volumes: Volume 1, Reporting Instructions; Volume 2, Workbook; Volume 3, Reference Manual.” Intergovernmental Panel of Climate Change. IPCC (1996), Climate Change 1995 . The Science of Climate Change. (J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg and K. Maskell (eds)). Published for The Intergovernmental Panel on Climate Change (IPCC), World Meteorological Organization/United Nations Environment Programme, Cambridge University Press, UK. LANDTEC (1994), “Coursewares” material provided at Landfill Gas System Engineering Design Seminars. Lexmond M.J. and G. Zeeman (1995), Potential of Uncontrolled Anaerobic Wastewater Treatment in Order to Reduce Global Emissions of the Greenhouse Gases Methane and Carbon Dioxide , Department of Environmental Technology, Agricultural University of Wageningen, Wageningen, The Netherlands. Report No. 95-1. OECD (1995), OECD Environmental Data Compendium 1995 . Organisation for Economic Co-operation and Development. Rosland, A. (1993 ), Greenhouse Gas Emissions in Norway: Inventories and Estimation Methods , pp.14. Prepared for the Norwegian Ministry of the Environment, Oslo, Norway. Stockton, M.B. and J.H.E. Stelling (1987), Criteria Pollutant Emission Factors for the 1985 NAPAP Emissions Inventory. US EPA Washington, Ouverage, EPA-600/7-87-015 XV-211. Tabasaran, O. (1981), “Gas production from landfill”. In Household Waste Management in Europe, Economics and Techniques , A.V. Bridgewater and Lidgren K. (eds.), Van Nostrand Reinhold Co., New York, USA, pp. 159-175. Tanaka, M., M. Miyazaki and I. Watanabe (1992), “CH 4 and N 2 O Emission from Waste Disposal Facilities in Japan”, pp. 18-19. Presented at the CH 4 and N 2 O Workshop held by the National Institute of Agro-Environmental Sciences (NIAES), Tsukuba, Japan, March 25-26,1992. UK department of the Environment (1993), An Assessment of Methane Emissions from UK landfills. UK DoE report CWM 063/93. US Environmental Protection Agency, Office of Air Quality Planning and Standards (1985), Compilation of Air Pollutant Emission Factors (Fourth Edition), Volume I: “Stationary Point and Area Sources.” EPA-AP-42 (GPO 055-000-00251-7), Research Triangle Park, North Carolina, USA. US Environmental Protection Agency (1991), Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines . EPA450/3-90-011a, US EPA, Research Triangle Park, North Carolina, USA. US Environmental Protection Agency (1994), International Anthropogenic Methane Emissions Report to Congress . EPA Office of Policy, Planning and Evaluation, EPA 230-R-93- 010. US Environmental Protection Agency (1995), Section 2.4, Landfills, in Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point and Area Sources , Fifth Edition, AP-42. US EPA Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, USA.

## W ASTE

6.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual Van Amstel, A.R., R.J. Swart, M.S. Krol, J.P. Beck, A.F. Bouwman and K.W. Van der Hoek (1993 ), Methane, the Other Greenhouse Gas.. Research and policy in the Netherlands. RIVM Report No. 481507001. Westlake, K. (1990), “Landfill microbiology”. In Proceedings of the International Conference: Landfill Gas: Energy and Environment '90 . Bournemouth, UK.