Revised 1996 IPCC Guidelines 

Volume 3
Revised 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
CONTENTS

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 CO2 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
CONTENTS

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 CO2 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....................................................................................................................................6-30
Revised 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
ACKNOWLEDGEMENTS

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-CO2 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).
ACKNOWLEDGEMENTS

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).
ACKNOWLEDGEMENTS

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 CO2 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).
ACKNOWLEDGEMENTS

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 PREFACE .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;
PREFACE

PREFACE .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 (SF6), ozone and aerosol precursors, and direct GHG (CO2,

CH4, N2O) 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 are

anticipated 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 OVERVIEW.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:

• THE GREENHOUSE GAS INVENTORY REPORTING INSTRUCTIONS

• THE GREENHOUSE GAS INVENTORY WORKBOOK

• THE GREENHOUSE GAS INVENTORY REFERENCE MANUAL

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 (CO2) methane (CH4), nitrous oxide (N2O),

halocarbons (HFCs, PFCs), sulphur hexafluoride (SF6), 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.
OVERVIEW

OVERVIEW.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
OVERVIEW

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

No Yes

No
OVERVIEW

OVERVIEW.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.

AVAILABILITY/USE OF COMPUTER

SOFTWARE

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
OVERVIEW

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual OVERVIEW.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 CO2 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 CO2 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
OVERVIEW

OVERVIEW.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 CO2 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".
OVERVIEW

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual OVERVIEW.7

The Reference Approach provides an upper bound to CO2 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 bound1 because

some of the carbon will be emitted in forms other than CO2, in part

because fuel combustion is not always complete but also because fuels may

leak or evaporate. Consequently the CO2 emissions figure obtained from

the Reference Approach will include carbon emitted as CH4, 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 CO2. 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 CO2 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.

• CO2 emissions from biomass used as fuels are excluded from the total

CO2 emissions figure. The restriction of the Reference Approach to

fossil fuels results from the sustainable nature of biofuels. The CO2

emissions are, however, reported for information purposes. Note

that non-CO2 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 CO2 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

CO2 equivalent of other fossil carbon based emissions from the source

 

 1 In practice, because of inaccuracies in the supply statistics and/or

emission factors, CO2 estimates from the Reference Approach may be less

than those obtained by summing all CO2 emissions from the combustion of

fuel.
OVERVIEW

OVERVIEW.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

category. In this manner, the resulting total CO2 emissions can be

compared with the result of the CO2 Reference Approach as part of the

inventory verification stage. If, however, CO2 emission factors, derived

from the carbon content of the fuel, are used then no addition of the CO2

equivalent of carbon gases is required.
Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual I NTRODUCTION .1

I NTRODUCTION TO THE

REFERENCE 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.
INTRODUCTION

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

C HAPTER 1

E NERGY

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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.1

1. ENERGY

1.1 Overview

This chapter discusses inventory methods for emissions of SO2 and direct and indirect

greenhouse gases from energy sources, comprising CO2, CH4, N2O, NOx, 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

CO2 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. CO2

emissions are primarily dependent on the carbon content of the fuel. The IPCC

Reference Approach for CO2 emissions is a simple, accurate and internationally

transparent approach which takes advantage of this fact.

CO2 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 CO2 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 CO2, national inventories of CH4, N2O, NOx, 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. CO2 emissions may also be calculated at the more

detailed level required for other gases. Indeed, when calculating non-CO2 emissions

national experts are encouraged to calculate CO2 emissions at the same time, as

reconciliation of total CO2 emissions estimated in this manner with those obtained from

the Reference Approach provides a valuable verification process. Procedures for

estimating CO2 and non-CO2 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
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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 CO2 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-CO2 GHG and SO2

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.
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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 (CO2 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 CO2 is presented together with new methods for the

estimation of CO2 and non-CO2 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.
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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. CO2 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 SO2 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, 1996c).

• 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.5

energy unit of activity (e.g. kg N2O/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 SOx, NOx and NMVOC. A few sources have also recently

emerged on various other GHGs. The more detailed factors (for gases other than CO2)

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 or

international data sets, it is likely that they are underestimated due to poor recordkeeping and lack of statistical information for non-commercial fuels.
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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.
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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 SO2.

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 CO2, CH4, N2O, NOx, CO and

NMVOC using energy statistics, and of SO2 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-ROM6.

1.4 Simple Methods (Tier 1) for Fuel

Combustion

The Tier 1 method for CO2 is fairly well established and is explained in Section 1.4.1. For

non-CO2 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-CO2 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 database7, the CORINAIR 1990 database and

scientific reports from different countries. SO2 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 1o x 1o grid

(Olivier et al., 1995).
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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 NOx, CO and NMVOC of the global inventories compiled by NASA,

ECAC/ANCAT, WSL and NLR [Wuebbles et al. (1993); Olivier (1995); Brok (1995)].

BOX 1

MAIN FUEL GROUPS

In the Tier 1 method for non-CO2 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 CO2 emissions from energy is discussed.

Carbon dioxide (CO2) 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 CO2 emissions is from the

oxidation of carbon when fossil fuels are burned, which accounts for 70-90 per cent of

total anthropogenic CO2 emissions. When fuels are burned, most carbon is emitted as

CO2 immediately during the combustion process. Some carbon is released as CO, CH4,

or non-methane hydrocarbons, which oxidise to CO2 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 CO2 emissions. The other carbon-containing gases

are also estimated and reported separately (see following sections for methodologies for

estimating CH4, 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-CO2 gases as a subset of CO2 emissions

and ensures that the CO2 emission estimates reported by each country represent the

entire amount of carbon that would eventually be present in the atmosphere as CO2. The
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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 CO2 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 intermediate

transformations 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 CO2 emissions but the total emissions must be compared with

those obtained from the Reference Approach. A “bottom-up” method for CO2 is briefly

discussed later in this section.

When estimating CO2 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 CO2. 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 CO2. 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 CO2 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.
ENERGY

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 CO2

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 CO2 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 CO2 Emissions

The estimation process can be divided into six steps that lead to figures for CO2

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 CO2 .

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 ENERGY

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.
ENERGY

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

TABLE 1-1

IPCC REFERENCE APPROACH

ENTRIES AND CALCULATIONS FOR STEPS (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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.13

TABLE 1-1 (CONTINUED)

IPCC REFERENCE APPROACH

ENTRIES AND CALCULATIONS FOR STEPS (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 CO2

Emissions

(Gg CO2)

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
ENERGY

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

TABLE 1-1 (CONTINUED)

IPCC REFERENCE APPROACH

EMISSIONS FROM INTERNATIONAL BUNKERS

(INTERNATIONAL MARINE AND AIR TRANSPORT)(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

TABLE 1-1 (CONTINUED)

IPCC REFERENCE APPROACH

EMISSIONS FROM INTERNATIONAL BUNKERS

(INTERNATIONAL MARINE AND AIR TRANSPORT)

(21) (22) (23) (24) (25)

Fuel

Fraction of

Carbon

Stored

Carbon

Stored

(Gg C)

Net Carbon

Emissions

Actual Carbon

Emissions

(Gg C)

Actual CO2

Emissions

(Gg CO2)

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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.15

TABLE 1-1 (CONTINUED)

EXPLANATORY NOTES

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 103

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 103

 tonnes. To convert tonnes to

terajoules, net calorific values (NCV) must be applied. The values to convert from 103

 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 103

 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).
ENERGY

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

TABLE 1-2

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR SELECTED NON-OECD COUNTRIES

(Terajoule per kilotonne)

Albania Algeria Angola

Cabinda

Argentina Armenia AzerbaijanBahrain BangladeshBelarussiaBenin Bolivia

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 CameroonChile 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.17

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR SELECTED NON-OECD COUNTRIES

(Terajoule per kilotonne)

Ecuador Egypt Estonia Ethiopia Gabon Georgia Ghana GuatemalaHong

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 KazakhstanKenya 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.
ENERGY

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

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR SELECTED NON-OECD COUNTRIES

(Terajoule per kilotonne)

Latvia LebanonLibya LithuaniaMalaysia Malta Mexico Moldova MoroccoMozambiqueMyanmar

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 PakistanPanama ParaguayPeru 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.19

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR SELECTED NON-OECD COUNTRIES

(Terajoule per kilotonne)

Poland Qatar Romania Russia Saudi

Arabia

Senegal SingaporeSouth

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

TajikistanTanzaniaThailandTrinidad /

Tobago

Tunisia Turkmenistan

Ukraine Utd

Arab

Emirates

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.
ENERGY

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

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR SELECTED NON-OECD COUNTRIES

(Terajoule per kilotonne)

Uruguay UzbekistanVenezuelaViet

Nam

Yemen Former

Yugoslavia

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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.21

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR OECD COUNTRIES

(Terajoule per kilotonne)

Australia Austria Belgium Canada DenmarkFinland France Germany 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.
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1.22 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-2 (CONTINUED)

1990 COUNTRY-SPECIFIC NET CALORIFIC VALUES FOR OECD COUNTRIES

(Terajoule per kilotonne)

Japan LuxembourgNetherlandsNZ 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.23

TABLE 1-3

NET CALORIFIC VALUES FOR OTHER FUELS

(TJ/103 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.
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1.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-4

CARBON EMISSION FACTORS FOR FUELS FROM DIFFERENT STUDIES

(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 Gasoline Kerosene 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, CO2 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:

Cg = 13.708 + (0.0828 x 10-3) x (Hv - 37 234)

where Cg is the carbon emission factor of the gas in t C/terajoule (TJ) and Hv 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 32.5o

 + 2o, 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 ENERGY

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:

Cc = 32.15 - (0.234 x Hv)

where Cc is the carbon emission factor in t C/TJ and Hv 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.
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1.26 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

BOX 2

APPROACHES FOR ESTIMATING CARBON STORED IN PRODUCTS

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 SO2 scrubbing (in which CO2 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 CO2 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 (103 t)

x Conversion Factor (TJ/103 t)

x Emission Factor (t C/TJ)

x Fraction Carbon Stored

x 10-3
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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.
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1.28 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-5

ESTIMATION OF CARBON STORED IN PRODUCTS

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 103.

(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:
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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 AFBC10 Up to 4.0%

PFBC/CFBC10 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.

TABLE 1-6

FRACTION OF CARBON OXIDISED

(RECOMMENDED DEFAULT ASSUMPTIONS)

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

Convert carbon emissions to full molecular weight CO2

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 (CO2), total carbon

oxidised should be multiplied by the molecular weight ratio of CO2 to C, (44/12).

1.4.1.2 E MISSIONS B Y S OURCE C ATEGORIES

A sectoral breakdown of national CO2 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 CO2 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-CO2 GHG emissions by sector (Section

1.4.2) has been extended to CO2 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 CO2 emissions from biofuels mean that the calculations for CO2

differ in a number of respects from those used for the non-CO2 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 CO2 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.
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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.
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1.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

BOX 3

AUTOPRODUCERS

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

CO2 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 uses

the 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 ENERGY

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

CO2 emissions from the combustion of biomass fuels are not to be included in the total

national CO2 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 CO2 emissions from them with

the emissions of the non-CO2 gases. Whatever methods are used for estimating the

quantities of fuels used by these two types when calculating the non-CO2 emissions from

this sector should be used for CO2. 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 CH4 from

biomass combustion. Fuel wood, charcoal, agricultural residues, agricultural waste and

municipal waste combustion is by far the major contributor to CH4 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
ENERGY

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

from Energy. Consequently, CH4 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 CH4 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 CH4.

The general method for estimating CH4 can be described as:

Emissions = ∑ (EFab x Activityab)

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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.35

TABLE 1-7

CH4 DEFAULT (UNCONTROLLED) EMISSION FACTORS (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-CO2 Emission Factors for Charcoal

Production.

(c) Includes dung and agricultural, municipal and industrial wastes.

(d) In the cruise mode CH4 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 N2O 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 N2O emissions with a maximum of N2O production occurring around 1000 K.

For combustion temperatures below 800 K or over 1200 K the emissions of N2O 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 N2O chemistry see de Soete (1993). The

mechanisms of N2O chemistry seem to be relatively well understood, but experimental

data are limited.

N2O 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.
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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 N2O can be described as:

Emissions = ∑ (EFab x Activityab)

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.

TABLE 1-8

N2O DEFAULT (UNCONTROLLED) EMISSION FACTORS (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 N2O than bituminous coals; some measurements have shown that N2O emissions by hard coal combustion in power plants may be

negligible. N2O 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-CO2 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. Emission factors for 2-

stroke engines may be three times higher than those for 4-stroke engines.
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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 oxides11 are indirect greenhouse gases. They have been the target of

environmental policies for their role in forming ozone (O3), as well for their direct

acidification effects.

Fuel combustion activities are the most significant anthropogenic source of NOx. 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 NOx emitted from coal (80-90 per cent) is formed from fuel nitrogen.

Thermal NOx 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 NOx and these conditions are dependent on boiler type and operation of

technology. For oil, the share of fuel NOx may be less than 50 per cent. From gaseous

fuels, only “thermal NO” is formed.

The NOx 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 NOx 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 NOx can be described as:

Emissions = ∑ (EFab x Activityab)

where:

EF = Emission Factor (kg/TJ);

Activity = Energy Input (TJ);

a = Fuel type; and

b = Sector-activity.

If abatement technologies for NOx emissions reduction are used, the estimated emission

factors of NOx 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 NOx (NO+NO2) emissions from fossil fuel

combustion are expressed on a full molecular basis assuming that all NOx emissions are

emitted as NO2.
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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 NOx emissions.

TABLE 1-9

NOX DEFAULT (UNCONTROLLED) EMISSION FACTORS (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) NOx 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-CO2 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.
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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 = ∑ (EFab x Activityab)

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

TABLE 1-10

CO DEFAULT (UNCONTROLLED) EMISSION FACTORS (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-CO2 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 Compounds12 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 ENERGY

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 = ∑ (EFab x Activityab)

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

TABLE 1-11

NMVOC DEFAULT (UNCONTROLLED) EMISSION FACTORS (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-CO2 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. SO2 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 SO2 is not a direct greenhouse gas, it is an aerosol precursor and as

such, has a cooling effect on climate.

Anthropogenic SO2 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 SO2 arises

from fuel combustion, with three-quarters of this arising from coal (Vernon, 1990). At

present an estimated 10 Mt/y of coal-related SO2 emissions are removed by flue-gas

desulphurisation technology world-wide (Ando, 1992).
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.43

The general method for estimating SO2 can be described as:

Emissions = ∑ ( EFab x Activityab )

where:

EF = Emission Factor (kg/TJ);

Activity = Energy Input (TJ);

a = Fuel type; and

b = Sector-activity.

The emissions of sulphur oxides (SOx) 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 SO2

13 emission factors can be estimated as:

EFSO2 [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 = SO2/S [kg/kg];

s = Sulphur content in fuel [%];

r = Retention of sulphur in ash [%];

Q = Net calorific value [TJ/kt];

106 = (Unit) conversion factor; and

n = Efficiency of abatement technology and/or reduction efficiency [%].

Sulphur appears in coal as pyritic sulphur (FeS2), 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 SOx formation. The sulphur is released when the

coal is burnt, mainly oxidised to SO2. Usually less than 1-2 per cent of the total sulphur is

released as SO3.

 

 13 Sulphur dioxide (SO2 + SO3 expressed as SO2 mass equivalent).
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1.44 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-12

SAMPLE AND DEFAULT VALUES OF SULPHUR CONTENT ( S ) IN FUEL

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 SOx emissions reduction are used, the estimated emission

factors for SO2 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 ENERGY

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.

TABLE 1-13

ENERGY CONTENT OF BIOMASS FUELS: DEFAULT NET CALORIFIC VALUES

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
ENERGY

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

TABLE I-14

DEFAULT NON-CO2 EMISSION FACTORS FOR CHARCOAL PRODUCTION

(IN KG/TJ)

Compound Default Emission Factor

(kg/TJ of Wood Input)(a)

Default Emission Factor

(kg/TJ of Charcoal Produced)

CH4 300 1000

N2O NAV NAV

NOx 5 10

CO 2000 7000

NMVOC 600 1700

SO2 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 ENERGY

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 CO2

It follows from the arguments given above for the construction of detailed emission

estimates that a country will also benefit from the estimation of CO2 emissions in parallel

with the calculation of non-CO2 inventories despite the existence of Tier 1 methods for

CO2 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 CO2. In cases where CO2 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 CO2 emission factors are given in this Chapter they include all carbon based

molecule emissions from the process. This ensures that CO2 totals constructed by

summing the results of the detailed estimation of emissions (the “bottom-up” approach)
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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 CO2 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-CO2 GHGs (particularly the

indirect gases) and SO2 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 ENERGY

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 NOx, N2O, CO, CH4, SO2 and NMVOCs from

stationary combustion plant. Estimation of CO2 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-CO2 emissions from combustion of biomass are estimated in exactly the

same manner as fossil fuel combustion emissions.14.

Emissions of non-CO2 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 NOx emissions 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

N2O and CH4. 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 CO2 emissions from biomass combustion.
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1.50 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

A section on SO2 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 = ∑ (EFabc x Activityabc)

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-CO2 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 ENERGY

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-CO2 gases can be

provided.

Emission Factor Data

Emission factors for all non-CO2 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 NOx,

17 CO, CH4, N2O 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 NOx emissions from fossil fuel combustion

are expressed on a full molecular basis assuming that all NOx emissions are emitted as

NO2.
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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 SO2 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.53

TABLE 1-15

UTILITY BOILER SOURCE PERFORMANCE

Emission Factors (kg/TJ energy input)

Basic Technology Configuration CO CH4 NOx N2O 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.
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1.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-16

INDUSTRIAL BOILER PERFORMANCE

Emission Factors (kg/TJ energy input)

Basic Technology Configuration CO CH4 NOx N2O 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.55

TABLE 1-17

KILNS, OVENS, AND DRYERS SOURCE PERFORMANCE

Emission Factors (kg/TJ energy input)(a)

Industry Source CO CH4 NOx N2O 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).
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1.56 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-18

RESIDENTIAL SOURCE PERFORMANCE

Emission Factors (kg/TJ energy input)

Basic Technology Configuration CO CH4 NOx N2O 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.57

TABLE 1-19

COMMERCIAL SOURCE PERFORMANCE

Emission Factors (kg/TJ energy input)

Basic Technology Configuration CO CH4 NOx N2O 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.
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1.58 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-20

UTILITY EMISSION CONTROLS PERFORMANCE

Technology

Efficiency

Loss(a)

(%)

CO

Reduction

(%)

CH4

Reduction

(%)

NOx

Reduction

(%)

N2O

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 NOx 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.59

TABLE 1-21

INDUSTRIAL BOILER EMISSION CONTROLS PERFORMANCE

Technology

Efficiency

Loss(a)

(%)

CO

Reduction

(%)

CH4

Reduction

(%)

NOx

Reduction

(%)

N2O

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

TABLE 1-22

KILN, OVENS, AND DRYERS EMISSION CONTROLS PERFORMANCE

Technology

Efficiency

Loss(a)

(%)

CO

Reduction

(%)

CH4

Reduction

(%)

NOx

Reduction

(%)

N2O

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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.61

TABLE 1-23

RESIDENTIAL AND COMMERCIAL EMISSION CONTROLS PERFORMANCE

Technology

Efficiency

Loss(a)

(%)

CO

Reduction

(%)

CH4

Reduction

(%)

NOx

Reduction

(%)

N2O

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

TABLE 1-24

NET CALORIFIC VALUES FOR PRECEDING TABLES(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 (CO2),

carbon monoxide (CO), nitrogen oxides (NOx), methane (CH4), nitrous oxide (N2O)

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
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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 CO2 emissions and emission

factors for CO2 emissions are provided in the following tables to permit the estimation of

CO2 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 = ∑ (EFabc x Activityabc)

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
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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.

CO2 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 CO2, CO, NOx, N2O, CH4 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 NOx.

All emission factor data are stated on the basis of full molecular weight of the respective

pollutant; NOx factors are stated as NO2.

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 NOx 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.
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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 NOx, CO, CH4 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).
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1.66 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-25

EMISSION CONTROL TECHNOLOGY TYPES AND US VEHICLE MODEL

YEARS USED TO REPRESENT THEM

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

TABLE 1-26

ASSUMED AMBIENT TEMPERATURE, DIURNAL RANGE AND REID VAPOUR PRESSURE FOR

DIFFERENT SEASONS

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.
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BOX 4

LIMITATIONS OF MOBILE5A RESULTS

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 NOx, 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.

N2O 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 N2O 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 N2O emissions from gasoline passenger cars. For light-duty gasoline trucks

and motorcycles, fuel specific N2O emissions were assumed to be the same as for the

corresponding passenger car technology. N2O emissions per kilometre were then
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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, N2O 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. N2O 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

N2O emissions from light-duty diesel vehicles in the absence of information on this class.

BOX 5

RECENT INFORMATION ON N2O MEASUREMENTS

Since the initial illustrative emission factors were estimated in 1991, a number of

measurement studies have been carried out to improve understanding of vehicle N2O

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

TABLE 1-27

ESTIMATED EMISSION FACTORS FOR US GASOLINE PASSENGER CARS

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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 N2O 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.71

TABLE 1-28

ESTIMATED EMISSION FACTORS FOR US LIGHT-DUTY GASOLINE TRUCKS.

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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 N2O 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.
ENERGY

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

TABLE 1-29

ESTIMATED EMISSION FACTORS FOR US HEAVY-DUTY GASOLINE VEHICLES

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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 N2O 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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.73

TABLE 1-30

ESTIMATED EMISSION FACTORS FOR US DIESEL PASSENGER CARS

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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
ENERGY

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

TABLE 1-31

ESTIMATED EMISSION FACTORS FOR US LIGHT-DUTY DIESEL TRUCKS

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.75

TABLE 1-32

ESTIMATED EMISSION FACTORS FOR US HEAVY DUTY DIESEL VEHICLES

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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

TABLE 1-33

ESTIMATED EMISSION FACTORS FOR US MOTORCYCLES

EMISSIONS

Season NOx CH4 NMVOC CO N2O CO2

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
ENERGY

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

European Emission Estimates

The European emission estimates for NOx, CH4, NMVOC (total VOC minus CH4), CO,

N2O and CO2 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, CO2 emissions are calculated to

include the carbon emitted as CO and as VOC.
1 ENERGY

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:
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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, NOx

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, NOX 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 ENERGY

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.

TABLE 1-34

SUMMARY OF PRECISION INDICATORS OF THE EMISSION ESTIMATES AND OF CALCULATION

METHODS APPLIED FOR THE DIFFERENT VEHICLE CATEGORIES AND POLLUTANTS

(A, B, C, D: Method Indicators - 1, 2, 3, 4: Precision Indicators)

Vehicle Category NOx CO NMVOC CH4 N2O CO2 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
ENERGY

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.

TABLE 1-35

EUROPEAN EMISSION CONTROL TECHNOLOGY TYPES

AND CORRESPONDING EU LEGISLATION AND MODEL YEARS

TECHNOLOGY LEGISLATION (MODEL YEAR)

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 ENERGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.81

TABLE 1-36

ESTIMATED EMISSION FACTORS FOR

EUROPEAN GASOLINE PASSENGER CARS

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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
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TABLE 1-37

ESTIMATED EMISSION FACTORS FOR

EUROPEAN DIESEL PASSENGER CARS

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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

TABLE 1-38

ESTIMATED EMISSION FACTORS FOR

EUROPEAN DIESEL LIGHT-DUTY VEHICLES

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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

TABLE 1-39

ESTIMATED EMISSION FACTORS FOR

EUROPEAN DIESEL HEAVY-DUTY VEHICLES

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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
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TABLE 1-40

ESTIMATED EMISSION FACTORS FOR

EUROPEAN GASOLINE LIGHT-DUTY VEHICLES

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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

TABLE 1-41

ESTIMATED EMISSION FACTORS FOR

EUROPEAN GASOLINE HEAVY-DUTY VEHICLES

EMISSIONS

NOx CH4 VOC CO N2O CO2

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

TABLE 1-42

ESTIMATED EMISSION FACTORS FOR

EUROPEAN MOTORCYCLES

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

MOTORCYCLES < 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

MOTORCYCLES > 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

MOTORCYCLES > 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
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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. CO2 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. NOx emissions from uncontrolled NGVs may be higher

or lower than comparable gasoline vehicles, depending on the engine technology. NOx

emissions from NGVs are more difficult to control using three-way catalysts. N2O

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 NOx 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 CO2 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.
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octane level allows some increase in efficiency, although less than for natural gas. NOx

emissions from LPG vehicles tend to be higher than for gasoline, but can also be

controlled using three-way catalysts. N2O 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 emissions

estimates for heavy-duty vehicles equipped with methanol or ethanol engines.
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1.86 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 1-43

ESTIMATED EMISSION FACTORS FOR US LIGHT- AND HEAVY-DUTY NATURAL GAS VEHICLES

NOx CH4 NMVOC CO N2O CO2

Passenger Cars

Advanced Control; Assumed Fuel Economy: 14.9 km/m3

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/m3

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/m3

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/m3

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/m3

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/m3

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
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TABLE 1-44

ESTIMATED EMISSION FACTORS FOR US LIGHT- AND HEAVY-DUTY LPG VEHICLES.

NOx CH4 NMVOC CO N2O CO2

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 CH4 emission factor of 0.013 g/MJ for this vehicle/technology class.

TABLE 1-45

ESTIMATED EMISSION FACTORS FOR

EUROPEAN LPG PASSENGER CARS

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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

TABLE 1-46

ESTIMATED EMISSION FACTORS FOR US LIGHT- AND HEAVY-DUTY METHANOL VEHICLES

EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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). N2O 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 NOx and CO are from Hadler (1990)22. N2O 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).
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TABLE 1-47

ESTIMATED EMISSION FACTORS FOR US NON-ROAD MOBILE SOURCES

UNCONTROLLED EMISSIONS

NOx CH4 NMVOC CO N2O CO2

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-CO2 gases.

For slow to medium speed diesel engines, considered to be representative of large oceangoing cargo ships, Lloyd’s Register (1995) reported NOx 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 NOx emission factor of 72
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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 CH4 and NMVOC for ocean-going

ships were not reported by IPCC (1995). In this study, CH4 and NMVOC emission rates

are estimated from hydrocarbon (HC) data reported by Lloyd’s Register according to

CH4 = 0.12 x HC and NMVOC = HC - CH4.

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.

TABLE 1-48

DEFAULT MARINE EMISSION FACTORS

CH4 N2O NOx 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.
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TABLE 1-49

ESTIMATED EMISSION FACTORS FOR

EUROPEAN NON-ROAD MOBILE SOURCES AND MACHINERY

PART 1: DIESEL ENGINES

EMISSIONS

NOx CH4

(a) NMVOC(a) CO N2O CO2

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

PART 2: GASOLINE ENGINES

EMISSIONS

NOx CH4

(a) NMVOC(a) CO N2O CO2

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

NOx, 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:
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BOX 6

OVERVIEW OF THE ACTIVITIES INCLUDED CORINAIR94

IN THE PRESENT METHODOLOGY 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 flights24.

 

 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 ENERGY

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 a

country. 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 stage25. 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
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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 NOx and

80-90 per cent of SO2 and CO2 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 NOx 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 cent26. 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 SO2 should be divided by 5 to show the corresponding factor.
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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.
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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

TABLE 1-50

EXAMPLES OF AIRCRAFT TYPES AND EMISSION FACTORS FOR LTO CYCLES

AS WELL AS FUEL CONSUMPTION PER AIRCRAFT TYPE

Emission factors

(kg/LTO)

Fuel

consumption

(kg/LTO)

Aircraft type(a) CO2 CH4 (b) N2O(c) NOX CO NMVOC(b) SO2

(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.
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TABLE 1-51

EMISSION FACTORS OF NOx FOR VARIOUS AIRCRAFT AT CRUISE LEVELS

Aircraft Emission Factor for NOx (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).
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TABLE 1-52

DEFAULT EMISSION FACTORS AND FUEL CONSUMPTION FOR AIRCRAFT

(LTO EMISSION FACTORS ARE GIVEN ON A PER AIRCRAFT BASIS)

Domestic

Fuel Emission Factors

Consumption CO2 CH4 (a) N2O(b) NOx CO NMVOC(a) SO2

(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 CO2 CH4 (a) N2O(b) NOx CO NMVOC(a) SO2

(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 CH4 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.
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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 (CH4) 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 CO2, and SO2 scrubbing, which is also a source of CO2. 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,

1993a; CIAB, 1992; Airuni and Zeidenvarg, 1992).

The amount of CH4 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
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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 CH4 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 CH4 is generated during coal formation. If two coal seams have the same rank, the

deeper seam will hold larger amounts of CH4 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 CH4

emissions from surface mines (Kirchgessner et al., 1993; USGS, 1993).

A portion of the CH4 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 CH4 to desorb from the coal.

Transportation of the coal contributes to CH4 emissions, because CH4 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 CH4 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;
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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
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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.
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TABLE 1-53

SUMMARY OF EMISSIONS ESTIMATES FROM SELECTED STUDIES

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.
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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 m3 CH4/tonne of coal produced. The structure of the estimation is

simply

Emissions (Gg CH4) = Emission Factor (m3 CH4 / tonne)

x tonnes of coal produced

x Conversion Factor (Gg/106m3)

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 CH4 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.
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EQUATION 1

TIER 1: GLOBAL AVERAGE METHOD – UNDERGROUND MINES

CH4 Emissions (Gg) = CH4 Emission Factor (m3 CH4/tonne of coal mined)

x Underground Coal Production (Mt)

x Conversion Factor (Gg/106 m3)

Where:

 the Emission Factor should be chosen from the following range

Low CH4 Emission Factor = 10 m3/tonne

High CH4 Emission Factor = 25 m3/tonne

 Conversion Factor converts the volume of CH4 to a weight measure and

is the density of methane at 20°C and 1 atmosphere, namely:

0.67 Gg / 106 m3

The IPCC recommends revised global average emission factors of 10 to 25 m3/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.

TABLE 1-54

ESTIMATED UNDERGROUND EMISSION FACTORS FOR SELECTED COUNTRIES

Country Emission Factors

 (m3/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 m3

/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
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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.
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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 m3

 of methane in 1989, of which 201 million

m3

 was used and the remaining 85 million m3 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 m3

 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).

TABLE 1-55

KEY ISSUES FOR CONSIDERATION WHEN USING TIER 3 – MINE SPECIFIC METHOD

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.
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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.

EQUATION 2

TIER 1: GLOBAL AVERAGE METHOD – SURFACE MINES

CH4 Emissions (Gg) = CH4 Emission Factor (m3 CH4/tonne of coal mined)

x Surface Coal Production (Mt)

x Conversion Factor (Gg/106 m3)

Where:

• the Emission Factor should be chosen from the following range:

Low CH4 Emission Factor = 0.3 m3/tonne

High CH4 Emission Factor = 2.0 m3/tonne

• Conversion Factor converts the volume of CH4 to a weight measure,

and is the density of methane at 20°C and 1 atmosphere, namely:

0.67 Gg/ 106 m3

In the original IPCC methodology, an average emission factor of 2.5 m3/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 m3

/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.
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Depending on the degree of detail desired, emissions can be estimated for specific coal

basins or countries, using the equation below.

EQUATION 3

TIER 2: COUNTRY OR BASIN SPECIFIC METHOD – SURFACE MINES

CH4 Emissions (Gg) = [In-Situ Gas Content (m3 CH4/tonne)

x Surface Coal Production (Mt)

x Conversion Factor (Gg/106 m3)]

+ [Assumed Emission Factor for Surrounding Strata

(m3 CH4/tonne)

x Surface Coal Production (Mt)

x Conversion Factor (Gg/106 m3)]

Where:

• In-Situ Gas Content and Assumed Emission Factor for Surrounding

Strata are described in the text.

• Conversion Factor converts the volume of CH4 to a weight measure

and is the density of methane at 20°C and 1 atmosphere, namely:

0.67 Gg /106 m3

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 assumed

that 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.
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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.

EQUATION 4

TIER 1: GLOBAL AVERAGE METHOD – POST-MINING ACTIVITIES

Underground CH4 Emissions (Gg) = CH4 Emission Factor (m3 CH4/tonne

of coal mined)

x Underground Coal Production (Mt)

x Conversion Factor (Gg/106 m3)

Surface CH4 Emissions (Gg) = CH4 Emission Factor (m3 CH4/tonne

of coal mined)

x Surface Coal Production (Mt)

x Conversion Factor (Gg/106 m3)

Where:

• Underground CH4 Emission Factors are in the range of:

0.9 to 4.0 m3/tonne

• Surface CH4 Emission Factors are in the range of:

0 to 0.2 m3/tonne

• Conversion Factor converts the volume of CH4 to a weight measure

and is the density of methane at 20°C and 1 atmosphere, namely:

0.67 Gg/106 m3

Underground-Mined Coals: The IPCC recommends emission factors of 0.9 to

4.0 m3/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 m3

/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.
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EQUATION 5

TIER 2: COUNTRY OR BASIN SPECIFIC METHOD – POST-MINING ACTIVITIES

a) Underground CH4 Emissions (Gg) = In-Situ Gas Content (m3 CH4/tonne)

x Underground Coal Production (Mt)

x Fraction of Gas Released During

Post-Mining Activities (%)

x Conversion Factor (Gg/106 m3)

When Necessary:

b) Surface CH4 Emissions (Gg) = In-Situ Gas Content (m3 CH4/tonne)

x Surface Coal Production (Mt)

x Fraction of Gas Released During

Post-Mining Activities (%)

x Conversion Factor (Gg/106 m3)

Where:

• In-Situ Gas Content and Fraction of Gas Released During Mining are

described in the text

• Conversion Factor converts the volume of CH4 to a weight measure and

is the density of methane at 20°C and 1 atmosphere, namely:

0.67 Gg/106 m3

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

CH4 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 CH4

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
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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 CH4, 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
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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:

EQUATION 6

Emissions from Coal Burning (Gg C) = Quantity of Coal Burned (103 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 N2O, CO, NOx, etc. are also emitted from combustion of

coal wastes.

1.7.3.2 SO 2 S CRUBBING

When SO2 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 CO2 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 CO2 emissions from SO2 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 SO2 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:

EQUATION 7

Emissions from SO2 Scrubbing (Gg C) = Total Coal Consumption (103 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 CO2 emissions (in Gg), it is

necessary to multiply by 44/12, the molecular weight ratio of CO2 to C.
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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 CH4 emissions from oil and natural gas. Because the

data are so limited at present, global and regional estimates of CH4 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 SO2.

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
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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.
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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
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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.

TABLE 1-56

METHANE EMISSIONS FROM OIL AND NATURAL GAS ACTIVITIES

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
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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.
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TABLE 1-57

SUMMARY OF METHANE EMISSION FACTORS

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
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TABLE 1-57 (CONTINUED)

SUMMARY OF METHANE EMISSION FACTORS

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
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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.

TABLE 1-58

REVISED REGIONAL EMISSION FACTORS FOR METHANE FROM OIL AND GAS ACTIVITIES (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).
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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 CH4 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:
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• 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

CO2 emissions estimates (described in the Tier 1 method for CO2) are consistent with

those used in this section.
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Tier 2 - Mass Balance Approach

The Mass Balance Approach is only recommended for oil system releases of CH4, 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 Approach

employs 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 CH4 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

EOil-P = methane emissions from oil production (Tg/year)

QOil-P = oil produced (m3/year)

GOR = gas to oil ratio; defines the amount of gas produced (in volume) per unit of

oil produced (in volume). (m3/m3, or dimensionless).

YCH4 = methane Fraction; the volume of gas dissolved in the oil that is methane,

on a volume basis, for example, 0.1 m3 of methane per 1.0 m3 of gas.

(may be considered dimensionless)

KOil-P = emission factor for oil production, see below (dimensionless)

DGOR = density of methane at the temperature and pressure at which the GOR is

estimated, (g/m3). 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/m3, and

at 20°C, and a pressure of 1 atmosphere, the density of methane is

666.6 g/m3.

The first two terms (QOil-P and GOR) estimate the total amount of gas that is withdrawn

from the ground while the oil is produced. The term YCH4

 converts the total gas quantity

into the quantity of methane (still on a volume basis). The emission factor (KOil-P) is the

fraction of the total gas withdrawn that is emitted. At most, KOil-P = 1. To put the

emissions estimate on a mass basis, DGOR is used to estimate grams, and the conversion

to teragrams follows.

EOil-P = × ×× × × − −

− Q GOR Y K D Oil P CH Oil P GOR 4 10 12
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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,

KOil-Pmin

= minimum emission factor for oil production (dimensionless)

QOil-P = oil produced (m3/year)

GOR = gas to oil ratio (dimensionless)

QGas-fuel = quantity of gas used as fuel (m3/year)

QGas-flared = quantity of gas flared (m3/year)

QGas-inj = quantity of gas injected back into ground (m3/year)

QGas-other = quantity of gas accounted for in some other manner and that is not

emitted (m3/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

− −− −

−

= × + ×+ × + ×

×

KOil-Pleak= emission factor for leaks in the systems used to handle gas during oil

production

QOil-P = oil produced (m3/year)

GOR = gas to oil ratio; defines the amount of gas produced (in volume) per unit

of oil produced (in volume) (dimensionless)

QGas-fuel = quantity of gas used as fuel (m3/year)

QGas-flared = quantity of gas flared (m3/year)

Qgas-inj = quantity of gas injected back into ground (m3/year)

QGas-other = quantity of gas accounted for in some other manner (m3/year)

Lx = 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
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If none of the gas is controlled or utilised (i.e., Lx = 1 for all x), then the emission factor

(KOil-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 CH4 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 CH4 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 CH4 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 CH4 .

Accordingly, the basic mass balance relation for oil transportation and refining activities

may be expressed as follows:

E Oil-T = QOil-T x F x YF-CH4

 x KOil-T x DF x 10-12

where,

EOil-T = methane emissions from crude oil transportation and refining (Tg/year)

QOil-T = oil transported and refined (m3/year)

F = factor defining the amount of gas in solution with the crude oil (per unit

of oil by volume) (Dimensionless)

YF CH − 4

= methane fraction; the fraction of the gas in solution in the oil that is

methane, on a volume basis, for example, 0.1m3 of methane per 1.0 m3 of

gas. (Dimensionless)

KOil-T = emission factor for oil transportation and refining, see below.

(Dimensionless).

DF = density of methane at the temperature and pressure at which F is

estimated (g/m3). 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/m3, and at

20°C and 1 atmosphere, the density of methane is 666.6 g/m3.

The first two terms (QOil-T and F) estimate the total amount of gas that is in solution with

the crude oil. The term YF-CH4

 converts the total gas quantity into the quantity of

methane (still on a volume basis). The emission factor (KOil-T) is the fraction of the total

gas in solution that is emitted (at most, KOil-T = 1). To put the emissions estimate on a

mass basis, DF 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.
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TABLE 1-59

SOLUTION GAS FACTORS AND CORRESPONDING CH4 MOLE FRACTIONS FOR

DIFFERENT TYPES OF CRUDE OIL PRODUCTION AT ONSHORE AND OFFSHORE

FACILITIES

Type of Crude Oil Onshore and Offshore Facilities

F

SOLUTION GAS FACTOR

YF-CH4

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

QCollected CH4 = 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 CH4 collected, the value of system

adjustment factor should be set to a default value of one.

Exploration and Drilling Losses

Total CH4 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:

ED = Nwells . FD

where,

ED = total CH4 emissions (Tg) from drilling and testing of oil and gas wells,

Nwells = number of wells drilled and tested, and

FD = average amount of CH4 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),
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• 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 CH4 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.
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TABLE 1-60

USA AND CANADA - EMISSION FACTORS

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)

..

..

..

TABLE 1-61

EASTERN EUROPE AND FORMER USSR - EMISSION FACTORS

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)

..

..

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

TABLE 1-62

WESTERN EUROPE - EMISSION FACTORS

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)

..

..

TABLE 1-63

OTHER OIL EXPORTING COUNTRIES - EMISSION FACTORS

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)

..

..

..
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.131

TABLE 1-64

REST OF THE WORLD - METHANE EMISSION FACTORS

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 SO2.

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);
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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 SO2, NOx, 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 SO2 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 1.133

TABLE I-65

NON-COMBUSTION EMISSION FACTORS FOR PETROLEUM REFINING. SIMPLE METHODOLOGY

(KG/M3 REFINERY FEEDSTOCK E.G., CRUDE OIL)

POLLUTANT EMISSION FACTOR SOURCES

SO2

(a) 0.8 Vacuum tower, catalytic cracker, fluid coking, sulphur plant, SWS,

incinerator, caustic regeneration, vents, off gases, others

NOx

(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/m3 input.

Estimates range from 0.085 kg/m3 from the best West European refinery to 10 kg/m3 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.

TABLE I-66

NON-COMBUSTION EMISSION FACTORS FOR REFINERIES

(FLUID CATALYTIC CRACKING KG/M3 OIL TREATED IN THE FLUID CATALYTIC CRACKER)

POLLUTANT EMISSION FACTOR

(VALUE)

EMISSION FACTOR

(RANGE)

SO2 1.4 0.286-1.505

NOx 0.2 0.107-0.416

CO 39.2 NA

NMVOC 0.6 NA

Source: US EPA (1985a, 1995).
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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.

TABLE I-67

NON-COMBUSTION EMISSION FACTORS FOR

REFINERIES AND SULPHUR RECOVERY PLANTS.

(KG/TONNE SULPHUR)

POLLUTANT EMISSION FACTOR

SO2 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.

TABLE I-68

NON-COMBUSTION EMISSION FACTORS FOR REFINERIES

(STORAGE AND HANDLING. G/KG OIL THROUGHPUT)

CONDITION EMISSION FACTOR

• 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.
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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

• N2O (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 (CH4), oil & gas industry (CH4

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, CH4 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 nonCO2 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.
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1.136 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

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

C HAPTER 2

I NDUSTRIAL P ROCESSES

2 INDUSTRIAL PROCESSES

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 CO2, CH4, N2O, and PFCs, can be released.

Cement production is a notable example of an industrial process that releases a significant

amount of CO2. Different halocarbons (and SF6) 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 (NOx, NMVOCs, CO and SO2).

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.

CO2 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 N2O emissions are recognised as

important anthropogenic contributors to global N2O emissions. It is estimated that this

source category represents 10 to 50 per cent of anthropogenic N2O emissions and 3 to

20 per cent of all global emissions of N2O (IPCC, 1992). The main sources of industrial

anthropogenic N2O emissions are adipic acid and nitric acid production.
INDUSTRIAL PROCESSES

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

Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6) 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 SF6, is expected to grow

substantially in the next decades due to their importance as substitutes for ozone

depleting substances.

HFCs, PFCs and SF6 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 CO2, CH4 and N2O 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 INDUSTRIAL PROCESSES

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.3

TABLE 2-1

POTENTIAL EMISSIONS FROM INDUSTRIAL PROCESSES.

Process Greenhouse Gases Ozone and Aerosol Precursors

CO2 CH4 N2O PFC SF6 HFC NOx NMVOC CO SO2

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 SF6 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.
INDUSTRIAL PROCESSES

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:

TOTALij = Aj x EFij

where:

TOTALij = process emission (tonnes) of gas i from

industrial sector j

Aj = amount of activity or production of process

material in industrial sector j (tonnes/yr)

EFij = 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 CO2 equivalent in the national CO2 inventory. Whether an explicit

addition to the CO2 inventory is required depends on how the national CO2 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 INDUSTRIAL PROCESSES

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

CO2 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 (CaCO3)

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:

CaCO3 + Heat → CaO + CO2

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" cement1.

It should be noted that when poured concrete is curing, some CO2 is reabsorbed by the

concrete from the atmosphere. This CO2 reabsorption is, however, believed to be only

a small fraction of the CO2 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 CO2.

Because CO2 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.
INDUSTRIAL PROCESSES

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

2.3.2 Emission Estimation Methodology for CO 2

Estimation of CO2 emissions from cement production is accomplished by applying an

emission factor, in tonnes of CO2 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 CO2 released per unit lime.

EFclinker = Fraction CaO x (44.01 g/mole CO2 / 56.08 g/mole CaO)

or

EFclinker = 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 CO2/CaO (0.785) gives a

clinker emission factor of 0.5071 tonnes of CO2/tonne of clinker produced.

EFclinker = 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 CO2 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 CO2/cement (0.136 tonne CO2 as C/tonne cement).

EFcement = 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 CO2 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 INDUSTRIAL PROCESSES

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 CO2 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 CO2 from

 masonry cement additives

The recommended method for estimating CO2 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 CO2/tonne clinker. Alternatively, cement production can be

multiplied by an emission factor of 0.4985 tonne CO2/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.

SO2 emissions will originate from sulphur in the fuel and in the clay raw material. Most

(about 70-95 per cent) of the SO2 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 SO2 from the clay should be counted as non-combustion emissions.

A non-combustion emission factor of 0.3 kg SO2/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 SO2/tonne cement is suggested.
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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:

CaCO3 (limestone) + heat → CaO (quicklime) + CO2

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 CO2) in accordance with the following reaction:

CaCO3

.Mg CO3 (dolomite) + heat → CaO.MgO (dolomitic lime) + 2CO2

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 CO2 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 CO2 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, CO2 emissions are estimated according to:

EF = 44.01 g/mole CO2 /56.08 g/mole CaO

 = 785 kg CO2 /tonne high calcium lime
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.9

For dolomitic lime, CO2 emissions are estimated according to:

 EF = 2 x 44 .01 g/mole CO2 /96.39 g/mole CaO • MgO

 = 913 kg CO2 /tonne dolomitic lime

The coefficient 2 relates to the stoichiometric ratio of CO2 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.

TABLE 2-2

SUMMARY OF EMISSION FACTORS

Process Component Emission Factor Reference

Lime Kiln-Calcite Feed CO2 0.79 tonnes CO2/tonnes

quicklime produced

ORTECH, 1991

Lime Kiln-Dolomite

Feed

CO2 0.91 tonnes CO2/tonnes

dolomitic lime

ORTECH, 1991

The consumption of lime may in cases result in the removal of CO2 from the

atmosphere. The use of hydrated lime (for water softening) for example, results in CO2

reacting with lime to form calcium carbonate. Lime is also used as a CO2 absorbent for

atmospheric control in the storage of fruit. At this time, data is not available to reliably

estimate the extent of atmospheric CO2 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. SO2 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, SO2 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 (CaCO3) and dolomite (CaCO3

.

MgCO3) 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, CO2 is generated.
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2.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

CO2 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 CO2 emissions.

2.5.2 Emissions Estimation Methodology for CO 2

The mass of CO2 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, EFls, for limestone use:

EFls = f x [44.01 g/mole CO2] / [(100.09 g/mole CaCO3)]

 = (440 x f ) kg CO2 / tonne limestone

where:

f is the fractional purity of limestone in CaCO3 per tonne of total raw material

weight (if unknown, the default factor for f is equal to 1).

Emission factor, EFls, for dolomite use:

Efd = f x [2 x 44.01 g/mole CO2] / [(184.41 g/mole CaCO3MgCO3)]

 = (477 x f) kg CO2 / tonne dolomite

The total CO2 emission from limestone and dolomite use in Gg/yr calculated as:

TotalId = {(Als x EFls) + (Ad x EFd) }/106

 = {(440 x f x Als) + (477 x f x Ad)}/106

where:

Totalld is the process emission of CO2 from limestone and dolomite use (Gg/yr)

Als 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 CO2 is not generated.

Ad 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 CO2 is not generated.
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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, Na2CO3) 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 CO2 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:

Na2CO3 x NaHCO3 x 2H2O→ 3Na2CO3 + 5H2O + CO2

 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 CO2 / 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:

CaCO3 + heat → CaO + CO2

CaO + H2O → Ca(OH)2

NaCl + H2O + NH3 + CO2 → NaHCO3 + NH4Cl

2NaHCO3 + heat → Na2CO3 + CO2 + H2O

Ca(OH)2 + 2NH4Cl → CaCl2 + 2NH3 + 2H2O
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The net overall reaction may be summarised as:

CaCO3 + 2NaCl → Na2CO3 + CaCl2

From the series of reactions presented above, CO2 is generated in two pyrolysis

processes. The CO2 generated is captured, compressed and directed to Solvay

precipitating towers for consumption in a mixture of brine (aqueous NaCl) and ammonia.

Although CO2 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

CO2 equals uptake.

In practice, however, CO2 is emitted to the atmosphere during the production of soda

ash because more CO2 is produced than is stoichiometrically required. The excess CO2

is produced by calcining limestone with metallurgical grade coke (approximately 7 per

cent of limestone weight). In order to avoid double counting, CO2 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

CO2 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 CO2 associated

with the Solvay process is zero. The excess CO2 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 CO2 / 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 CO2. Available experimental data from Australia indicate that

approximately 0.23 tonnes of CO2 is sequestered from the ocean for each tonne of soda

ash produced (Workbook, Australia, 1995).
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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 CO2 is emitted, so that the mass of CO2

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 CO2 /105.99 g/moleNa2CO3

= 415 kg CO2/tonne Na2CO3

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.

TABLE 2-3

EMISSION FACTORS FOR ASPHALT ROOFING PRODUCTION (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.
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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.

TABLE 2-4

EMISSION FACTORS FOR ROAD PAVING WITH ASPHALT ( KG/TONNE ASPHALT)

SO2 NOx 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/m2 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, SO2 emissions will originate from the fuel use and sulphur in clay. About 45

per cent of the SO2 generated in the process will be sequestered in the product. An

emission factor of about 0.5kg SO2/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 CH4) or other fossil fuels. As can be seen in the following reactions with

methane as a feedstock, carbon dioxide is produced.

C + H2O → CO + H2

CH4 + H2O → CO + 3H2

N2 + 3H2 → 2NH3
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.15

In general, the processes that affect CO2 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 CO2 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 CO2 from the synthesis process) (CFI, 1992). The production of ammonia represents

a significant non-energy industrial source of CO2 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 CO2 at plants using the natural gas catalytic steam reforming

process occurs during regeneration of the CO2 scrubbing solution with lesser emissions

resulting from condensate stripping.

Carbon Dioxide Regenerator

After absorption of CO2 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 CO2 from the bicarbonates according to the following reactions:

Heat 2KHCO3 → K2CO3 + H2O + CO2

Heat (C2H5ONH2) 2 + H2CO3 → 2C2H5ONH2 + H2O + CO2

The stripping gas, containing CO2 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 CO2 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 CO2 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.
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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 CO2 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 CO2 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.

TABLE 2-5

AMMONIA PRODUCTION EMISSION FACTORS

Country Emission Factor a,b

Tonne CO2/tonne NH3 produced

Reference

Canadac 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 m3 gas/tonnes NH3 and 0.525 kg carbon/m3 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).

SO2, NOx, CO and NMVOC may be emitted in addition to CO2. Default emission

factors for uncontrolled emissions in Table 2-6 are taken from U.S. EPA 1995.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.17

TABLE 2-6

EMISSION FACTORS FOR AMMONIA PRODUCTION(KG/TONNE PRODUCT)

SO2 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 (HNO3) generates nitrous oxide (N2O) as a by-product of

the high temperature catalytic oxidation of ammonia (NH3).

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:

4NH3 + 5O2 → 4NO + 6H2O

2NO + O2 → 2NO2

3NO2 + H2O → 2HNO3 + 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 N2O. Nitric oxide (NO), an intermediate in the production of nitric acid, is

also documented to readily decompose to N2O and nitrogen dioxide (NO2) at high

pressures for a temperature range of 30 to 50°C (Cotton and Wilkinson, 1988).

2.9.2 Emission Data of N 2O

Table 2-7 gives examples of emissions factors from nitric acid production plants, based on

measurements. Emission rates depend upon technology and operating conditions.
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TABLE 2-7

EMISSION FACTORS FOR N2O FROM NITRIC ACID PRODUCTION

Emission Factor

kg N2O/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 N2O/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 2O

There are usually only very few plants in each country producing nitric acid, so measured

data on N2O 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.

N2O-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 NOx.

Emissions are estimated from the amount of nitric acid produced. Factors range from

0. 1- 1.0 NOx/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 NOx/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.
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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. N2O is generated as a by-product of the nitric

acid oxidation stage:

(CH2)5CO + (CH2)5CHOH + wHNO3

 (Cyclohexanone) (Cyclohexanol)

→ 

HOOC(CH2)4COOH (Adipic Acid) + xN2O + yH2O

Adipic acid production also results in the emissions of NMVOC, CO and NOx. 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 2O

Adipic acid production unavoidably produces N2O as a by-product with an associated

emission factor (for unabated emissions) of 300g N2O/kg adipic acid produced (Thiemens

and Trogler, 1991). Japanese emissions (measured at 264 g N2O/kg adipic acid) are

consistent with this value (Japan Environment Agency, 1995).

N2O emissions (kg) = Adipic Acid Production(tonnes)

x 300 kg N2O/ tonne Adipic Acid

Often, the abatement of N2O results from the treatment of the off-gases4 in a reductive

furnace. A number of adipic acid producers treat the off-gases with the aim of reducing

NOx emissions, but the treatment also destroys N2O (Reimer et al., 1992).

There is a range of abatement efficiencies attainable with currently available technologies.

Any reduction in N2O 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.
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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 CO2, NO and

NO2 in addition to N2O, but does not propose emission factors at present.

Furthermore, European reported emission data indicate that pollutants other than N2O

are not significant (CORINAIR-90). U.S. EPA emission factors are given in Table 2-8

(U.S. EPA 1995).

TABLE 2-8

EMISSION FACTORS FOR ADIPIC ACID PRODUCTION ( KG/TONNE PRODUCT)

NOX 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, CO2 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.

O2

SiO2 + 3C → SiC + 2CO → 2CO2

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:

CO2 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
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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 CO2/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 CO2. 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 CO2 to form

CaCO3. Hence, the CO2 emitted from the limestone may be said to be recycled.

Production of CaC2:

CaCO3 → CaO + CO2

CaO + 3C → CaC2 + CO (→ CO2)

Use of carbide:

CaC2 + 2H2O → Ca(OH) 2 + C2H2 → 2CO2

The CO gas will in most plants be utilised as energy. 1.8 tonnes CO2/tonne calcium

carbide will be released in the production process. In addition, 1.1 tonnes CO2/tonne

calcium carbide will be released when the carbide is used. The CO2 emissions may be

lowered by utilising the gas when producing dicyanodiamide from carbide (Olsen 1991).

Limestone contains about 98 per cent CaCO3. 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.
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The emission factors in Table 2-9 are suggested in the latter case:

TABLE 2-9

EMISSION FACTORS (KG CO2/TONNE CARBIDE)

Limestone 760

Reduction 1090

Use of product 1100

The theoretical emission factor calculated from a stoichiometric reaction is 1.37 tonne

CO2/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.

SO2 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 SO2 potentially emitted will be sequestered

in the product (Rypdal 1995, Rosland 1987). An emission factor of 1.5 kg SO2/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 2O 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 N2O. 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
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adipic acid and nitric acid production, the N2O 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 N2O (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 N2O 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 CH4/KG PRODUCTION)

Emission factor

(g CH4/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.
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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.
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TABLE 2-11

EMISSION FACTORS FOR MISCELLANEOUS PRODUCTION PROCESSES IN CHEMICAL INDUSTRIES.

(KG/TONNE PRODUCT)

Source SNAP SO2 NOx 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 chloridea 40504

1,2, dichloroethane 40505 - - 2.2 -

Source: EMEP/CORINAIR guidebook, except the CASPER project (CASPER 1995).

aThe 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.
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2.13 CO2 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, CO2 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

CO2 emissions are not counted in Chapter 2 as net emissions. These net emissions of

CO2 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 CO2)

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.

TABLE 2-12

CO2 EMISSION FACTORS FOR METAL PRODUCTION GENERALLY

(TONNE CO2/TONNE REDUCING AGENT)

Reducing Agent Emission Factora

Coalb 2.5

Coke from coalb 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, CO2 will be emitted from baking (prebaked anodes). In the aluminium

industry about 5 per cent of the non-combustion CO2 emissions using the prebaking

technology will be from baking. No data is available for other metal industries using

prebaked anodes.
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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 SO2, CO, NOx and NMVOC.

Emissions of SO2 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.

NOx is produced primarily by the high temperate oxidisation of nitrogen in air. In metal

production, most NOx 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 NOx emissions are in

principle included in this section, but are often impossible to distinguish from the fuel

NOx.

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 (CaCO3) 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.
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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, CO2 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, CO2 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.

TABLE 2-13

CO2 EMISSION FACTOR FOR IRON AND STEEL PRODUCTION

(TONNES CO2/TONNE IRON OR STEEL PRODUCT)

Country Description Emission Factor Reference

Canadaa Integrated facilityb (coke plus iron

and/or steel production).

1.6 Environment Canada

(1996)

a Includes CO2 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 CO2 emissions.

b Environment Canada has reported an emission factor of approximately 1.5 tonnes CO2/tonne iron or steel

for a non-integrated facility. This is, however, a rather uncertain value.

Note: Figures exclude CO2 from flux (CaCO3) 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).
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Preliminary research from Environment Canada suggests that sulphur dioxide emissions

from the blast furnace may be 1000-3000 g SO2/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: SO2: 30 g/tonne

product, NOx: 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 SO2, NO2 and CO emission factors are

only given for process smelter gas (as sometimes used for rolling pretreatment).

TABLE 2-14

EMISSION FACTORS FOR ROLLING MILLS (G/TONNE STEEL PRODUCED)

Pollutant Emission Factor (default) Emission Factor (Range)

SO2 a 45 30-60

NOx

 a 40 20-50

CO a 1 0.3-1

NMVOC 30 20-30

a from process smelter gas
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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):

Fe2O3 + 2 SiO2 + 7C → 2FeSi + 7CO

Primary emissions in covered arc furnaces consist almost entirely of CO as opposed to

CO2, due to the strong reducing environment (ORTECH, 1994). All CO is assumed,

however, to be converted to CO2 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 CO2 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).
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TABLE 2.15

CO2 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 metala 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 bioCO2/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

SO2, CO, NOx 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.

NOx 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.
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TABLE 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 (Al2O3), is dissolved in a

fluoride bath consisting primarily of cryolite, Na3AlF6. 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 CO2:

Al2O3 + 3/2C → 2Al + 3/2 CO2

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

CO2 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
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CO2 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 CO2 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.

TABLE 2-17

CO2 EMISSION FACTORS FOR PRIMARY ALUMINIUM PRODUCTION

(TONNES/TONNE PRODUCT)

Pollutant Soderberg Process Prebaked Anode Process

CO2 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.

TABLE 2-18

EMISSION FACTORS FOR ALUMINIUM PRODUCTION

(KG/TONNE PRIMARY ALUMINIUM PRODUCED)

Pollutant Process Emission Factor (Default) Emission Factor (Range)

SO2 Electrolysis 14.2 10-17.5

Anode baking 0.9 0.8-1.0

NOx 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.
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2.13.6 PFCs from Aluminium Production

2.13.6.1 Overview

Two PFCs, carbon tetrafluoride (CF4) and carbon hexafluoride (C2F6), 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 (Al2O3) is dissolved in a fluoride melt

consisting primarily of cryolite, Na3AlF6. 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 CF4 and C2F6. 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, CF4 and C2F6 in addition to CO2. It is believed that the carbon anode

becomes completely covered by gas during the AE. The two reactions of interest at this

point are:

Na3AlF6 + 3/4C = Al + 3NaF + 3/4CF4

Na3AlF6 + C = Al + 3NaF + 1/2C2F6

The overall anode gas composition below the anode during an anode effect may be

approximately 15 % wt CF4, 20 wt % CO2, 65 wt % CO and 1 wt % C2F6 (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 CF4/tonne Al) and Søderberg lines (0.15 to

0.9 kg CF4/tonne Al).
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TABLE 2-19

MEASURED EMISSIONS OF PFCS FROM PRIMARY ALUMINIUM PRODUCTION

Norway

(Norsk Hydro, 1996)

Canada

(Schiff ,1994)

CF4 C2F6 CF4 C2F6

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 CF4/tonne Al, and 0.05 kg

C2F6/tonne Al (Workbook, Australia, 1995).

A study of Canadian aluminium plants found CF4 emission factors to be between 0.045

and 1.2 kg. per tonne of aluminium produced (Unisearch, 1994). The emission factor for

C2F6 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 CF4 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

CF4. The studies made projections based on the assumption that all atmospheric CF4

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

CF4/per tonne Al, and 0.2 kg C2F6/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 CF4 emissions.
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TABLE 2-20

ESTIMATED GLOBAL CF4 EMISSIONS FROM SMELTERS WITH

VARIOUS CELL TECHNOLOGIES

Type of Cell Technology Per Cent of World

Production

kg CF4 /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 CF4 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 CF4 is formed for every kiloampere-minute (kA min) duration of the

anode effect. For example, CF4 emissions for an aluminium smelter having an average

percentage (p) of 16 per cent CF4 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 CF4 / tonne Al = (kg CF4/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 CF4 and C2F6 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.
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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 CF4 emissions for anode effects

longer than 2 minutes are calculated as follows:

kg CF4/tonne Al = 1.698 x (p / CE) x AEF x AED

p = average fraction of CF4

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 C2F6 emissions be 1/10 that of CF4.

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

CF4 emissions from a smelter with a given cell technology.

CF4 emission (kg) = EF(tech) (kg CF4/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, CO2 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.
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TABLE 2-21

PRODUCTION PROCESSES FOR SOME METALS

Metal Main Ore(s) Carbon

Reduction

Electrolysis

(without carbon)

Other

 (non-CO2)

Chromiuma FeCr2O4, PbCrO4 x

Copper Cu2S, CuFeS2, Cu2O, x x (SO2)

Gold Element x x

Lead PbS x x (SO2)

Magnesium Carbonate x x

Mercury HgS x (SO2)

Molybdenium MoS2 x (SO2)

Nickel NiS, NiO x x x (SO2)

Platinum Element, PtS x

Siliconb SiO2, Si-O-alkali x

Silver Ag2S, element x

Tin SnO2 x

Titanium TiO2, FeTiO3 xc

Tungsten WO3 x

Uranium UxOy x

Zinc ZnS, ZnCO3 x x x (SO2) a See also ferroalloy production

b See also ferroalloy production and carbide production

c Two step reduction process, involving first C + Cl2, then Mg

Note: The appearance of (SO2) in the final column indicates that the production process is a major world-wide source of

SO2 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, SF6 is used as a cover gas in foundries to prevent oxidation of

molten magnesium. The Norwegian producer of magnesium has assessed whether SF6

used as a cover gas reacts with other components in the furnaces. The results so far

indicate that SF6 is quite inert. For the time being it is therefore assumed that all SF6

used as cover gas is emitted to the atmosphere. The consumption figures are therefore

used as emission estimates.
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In the aluminium industry SF6 is used as a cover gas only for special foundry products. As

SF6 is assumed to be inert, SF6 emissions should equal consumption:

Emission of SF6 = Consumption of SF6 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 SO2 may be lower in new mills than the

older ones (U.S. EPA 1995).
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TABLE 2-22

NON-COMBUSTION EMISSION FACTORS FOR PAPER AND PULP PRODUCTION -

KRAFT PULPING

(KG/TONNE DRIED PULP)

Pollutant Emission Factor (Default) Emission Factor (Range)

SO2 7 0.005-10

NOx 1.5 0.017-1.5

VOCa 3.7 0.1-4.9

COb 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. SO2 is considered to be

the major pollutant. There are at least four types of processes: ammonium based (NH3),

calcium based (Ca), magnesium based (MgO) and sodium based (Na) (U.S. EPA, 1995).

Emissions factors from U.S. EPA, 1995 are given in Table 2-23.

TABLE 2-23

NON COMBUSTION EMISSIONS FROM PAPER AND PULP PRODUCTION -

ACID SULPHITE PULPING

(KG/TONNE DRIED PULP)

Pollutant Type of Process Emission Factor

(Default)

Emission Factor

(Range)

SO2 NH3, 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 SO2 and NOx. 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.
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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.

TABLE 2-24

EMISSION 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.
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TABLE 2-25

EMISSION 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 SF6)

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 fijCij
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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 fijCij

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 SF6)

2.17.1 Overview

Partially fluorinated hydrocarbons (HFCs), perfluorinated hydrocarbons (PFCs), and

sulphur hexafluoride (SF6) 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):
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- refrigeration and air conditioning

- fire suppression and explosion protection

- aerosols

- solvent cleaning

- foam blowing

- other applications5

Primary uses of SF6 include:

- gas insulated switch gear and circuit breakers

- fire suppression and explosion protection

- other applications6

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), the

only 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-227

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).

SF6 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, SF6) 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 CO2 (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 SF6 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 SF6,

but the emissions associated with these industries are covered in Section 2.13.8

 7 HCFCs - hydrochlorofluorocarbons.
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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.

NF3 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.

TABLE 2-26

POTENTIAL APPLICATION AREAS AND GLOBAL WARMING POTENTIALS (GWPS) FOR HFCS, PFCS, AND SF6

Chemical GWPa Refrigeration

and Air

Conditioning

Fire

Suppression

and

Explosion

Protection

Aerosols Solvent

Cleaning

Foam

Blowing

Other

Applicationsb

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 PFCsc x

SF6 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.
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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 destroyed8, 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 release9 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 SF6 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.
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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
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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:

TABLE 2-27

CALCULATION SCHEME FOR POTENTIAL EMISSIONS ACCORDING TO TIER 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 SF6.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 2.49

TABLE 2-28

ADDITIONAL CALCULATIONS FOR ESTIMATING

POTENTIAL EMISSIONS ACCORDING TO TIER 1B

Refrigeration

GHFC-xxx = G(Unit i) x n (Unit i) x FHFC-xxx(Unit i) + - - - - - + 

G(Unit m) x n (Unit m) x FHFC-xxx(Unit m)

where:

GHFC-xxx = total import (export) of HFC-xxx in precharged refrigeration

units10

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)

FHFC-xxx = fraction of component HFC-xxx11 in the refrigerant (mixture) of

a unit of type "i"

Foam products12

GHFC-xxx = V(Foam i) x JHFC-xxx(Foam i) + - - - - - - - + 

V(Foam m) x JHFC-xxx(Foam m)

where:

GHFC-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)

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

Fire extinguishers

GHFC-xxx = G (Unit i) x n (Unit i) x FHFC-xxx(Unit i) + - - - - + 

G (Unit m) x n (Unit m) x FHFC-xxx(Unit m)

where:

GHFC-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)

FHFC-xxx = fraction of component HFC-xxx13 in the fire extinguishing

agent of a unit of type "i"

Solvents

GHFC-xxx = G (Solvent i) x FHFC-xxx(Solvent i) + - - - - - - - + 

G (Solvent m) x FHFC-xxx(Solvent m)

where:

GHFC-xxx = total import (export) of HFC-xxx in solvents

G(Solvent i) = quantity of solvent of type "i" imported (exported)

(i = i → m)

FHFC-xxx = fraction of component HFC-xxx14 in solvent of type "i"

Aerosols

GHFC-xxx = G(Can i) x n (Can i) + - - - - - - - + 

G(Can m) x n (Can m)

where:

GHFC-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.
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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.

TABLE 2-29

EXAMPLE 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

Kingdoma

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.
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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 in

refrigeration 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. In

addition, 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/assembly15 ;

• 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.
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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:

EQUATION 1

E assembly, t = E charged, t • (k/100)

where:

Eassembly,t = emissions during system manufacture/assembly in year t

Echarged,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 (Echarged,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:

EQUATION 2

E operation, t = E stock, t • (x/100)

where:

Eoperation,t = amount of HFC/PFC emitted during system operation in year t

Estock,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” (Estock,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:
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2.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

EQUATION 3

E disposal, t = Ei charge (t - n) • (y/100) • (100 - z )/100

or

E disposal, t = Ei charge (t - n) • Q

where:

Edisposal,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 (Ei

 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:

EQUATION 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
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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.

TABLE 2-30

DISTRIBUTION OF INDIVIDUAL HFCS/PFCS IN REFRIGERATION, IN NORWAY AND SWEDEN, IN 1994

HFC-23 HFC-32 HFC-125 HFC-134A HFC-143A HFC-152A 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
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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
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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).
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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
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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.
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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.
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Emission of sulphur hexafluoride from fire extinguishing equipment

Some of the new substitutes for halon in fire extinguishing equipment contain sulphur

hexafluoride, SF6, probably in blends with HFC. If the products contain SF6, 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

SF6, since they have to be adjusted for the proportion of the SF6 in the original blend.

Emissions of SF6 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:
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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 SF6

Primary uses of SF6 include the following:

Gas-Insulated Switchgear and Circuit Breakers

SF6 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, SF6. These applications

are described in Section 2.17.4.4.

Globally, it is estimated that about 80 per cent of SF6 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).
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Other applications

SF6 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 SF6 in production of aluminium and magnesium is covered under

Section 2.13.8.

Recommended methodology for estimating SF6 emissions

Total emissions of SF6 used in GIS application and circuit breakers can be assumed to be

approximately 1 per cent of the total quantity of SF6 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 SF6 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 SF6 in year t

=

1% of the total charge of SF6 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 SF6 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

C HAPTER 3

S OLVENT AND O THER

P RODUCT U S E

13 SOLVENT AND OTHER PRODUCT USE

RGY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 3.1

3 SOLVENT AND OTHER PRODUCT USE

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, N2O 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.
SOLVENT AND OTHER PRODUCT USE

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 SOLVENT AND OTHER PRODUCT USE

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 - CO2, CH4, and

N2O, 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).

TABLE 3-1

POTENTIALLY IMPORTANT SUBCATEGORIES INCLUDED UNDER SOLVENT AND OTHER PRODUCT USE

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.
SOLVENT AND OTHER PRODUCT USE

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 SOx, NOx, NMVOCs, CO, TSP, NH3, CH4, CO2,

N2O 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 AGRICULTURE

IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

C HAPTER 4

A GRICULTURE

4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.1

4. AGRICULTURE

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:

• CH4 and N2O emissions from domestic livestock (enteric fermentation

and manure management)

− CH4 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 CH4, although ruminants are the largest source since they are able to

digest cellulose, a type of carbohydrate, due to the presence of specific microorganisms in their digestive tracts. The amount of CH4 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.

− CH4 emissions from manure management

CH4 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.

− N2O emissions from manure management

During storage of manure, some manure nitrogen is converted to N2O.

Emissions of N2O related to manure handling before the manure is added to

soils are included in this source category. (Manure-related N2O emissions

from soils are considered agricultural soil emissions).

• CH4 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 CH4 flux depends upon

the input of organic carbon, water regimes, time and duration of drainage, soil

type etc.

• CH4, CO, N2O, and NOX emissions from agricultural burning (savanna

and agricultural burning)

– CH4, CO, N2O, and NOX 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
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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 CO2 emissions are therefore assumed to be

zero. However, savanna burning also releases gases other than CO2, including

methane, carbon monoxide, nitrous oxide and oxides of nitrogen. Unlike CO2

emissions, these are net emissions.

– CH4, CO, N2O, and NOX 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-CO2

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.

• CH4, CO2, and N2O emissions from agricultural soils

Emissions of N2O 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 N2O 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 N2O 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, N2O emissions. Direct soil emissions of

N2O from animal production include those induced by grazing animals.

Emissions from other animal waste management systems are reported under

“Manure Management’’. Indirect N2O emissions take place after nitrogen is

lost from the field as NOx, NH3 or after leaching or runoff. Agricultural soils

may also emit or remove CO2 and/or CH4. For example, peat compost used

as a soil amendment in agriculture and gardening may result in CO2 emissions

or removals. Carbon emissions from organic, mineral and limed soils are

discussed in Chapter 5.
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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 method2.

 

 1 All GHG emissions from the burning of animal waste are estimated in Section 1.4;

Greenhouse Gas Emissions from Burning Traditional Biomass Fuels. CO2 from the

burning of animal waste is part of a closed cycle and is not counted as net CO2.

 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
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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

N2O released depends on the system and duration of waste management. Emissions of

N2O taking place during storage or handling of manure (i.e., before the manure is added

to soils) are reported under “ Manure Management”. Manure-induced N2O 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.5

BOX 1

HUMAN WASTE USED AS FERTILISER

Human waste is sometimes used as fertiliser, and can result in emissions or

removals of CH4, N2O or CO2. At present, no methodology can be

recommended for estimating CH4 and CO2 emissions. N2O 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. CH4 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:
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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.

TABLE 4-1

DOMESTIC LIVESTOCK INCLUDED IN THE METHODS

Livestock Recommended Emissions Inventory Methods

Enteric Fermentation Manure Management

Dairy Cattle Tier 2a Tier 2a

Non-dairy Cattle Tier 2a Tier 2a

Buffalo Tier 1 Tier 2a

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 2a

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

TABLE 4-2

ANIMAL POPULATION DATA COLLECTED IN TIER 1 STEP 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.
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− 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 Bo) 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 (Bo) 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.
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TABLE 4-3

ENTERIC FERMENTATION EMISSION FACTORS

(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 the

Indian 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 population3.

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.
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TABLE 4-4

ENTERIC FERMENTATION EMISSION FACTORS FOR CATTLE

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
AGRICULTURE

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

TABLE 4-5

MANURE MANAGEMENT EMISSION FACTORS

(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

Poultryb 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 Bo 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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.13

TABLE 4-6

MANURE MANAGEMENT EMISSION FACTORS FOR CATTLE, SWINE AND BUFFALO

Regional Characteristics Livestock Type

Emission Factor by Climate Regiona

(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
AGRICULTURE

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) / (106 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 AGRICULTURE

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.

TABLE 4-7

RECOMMENDED REPRESENTATIVE CATTLE TYPES

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
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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 type4:

• 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 and

rangelands; 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 AGRICULTURE

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 and

production 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 (NEm) has been estimated to

be a function of the weight of the animal raised to the 0.75 power (NRC, 1984):

EQUATION 1

NEm (MJ/day) = 0.322 x (weight in kg)0.75

NRC (1989) recommends that lactating dairy cows be allowed a slightly

higher maintenance allowance:

 NEm (MJ/day) = 0.335 x (weight in kg)0.75 dairy cows}
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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

EQUATION 2

NEfeed =

Confined animals (pens and stalls): no additional NEm;

Animals grazing good quality pasture: 17 % of NEm; and

Animals grazing over very large areas: 37 % of NEm.

• Growth

The energy requirements for growth can be estimated as a function of the weight of

the 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:

EQUATION 3

NEg (MJ/day) = 4.18 x {(0.035 W0.75 x WG1.119) + WG}

where:

W = animal weight in kilograms (kg); and

WG = weight gain in kg per day.

The relationships for NEg 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):

EQUATION 4

NEl (MJ/day) = kg of milk/day x (1.47 + 0.40 x Fat %)

At 4.0 per cent fat, the NEl 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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.19

NEm requirements are required per hour of typical work for draft animals. This

value is used as follows:

EQUATION 5

NEdraft (MJ/day) = 0.10 x NEm 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:

EQUATION 6

NEpregnancy (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

EQUATION 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 NEm for the range of cow sizes

considered in this analysis. Therefore, a factor of 7.5 per cent of NEm 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.
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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):

EQUATION 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:

EQUATION 9

NE/DE = 1.123 - (4.092 x 10-3 x DE%) + (1.126 x 10-5 x (DE%)2)

- 25.4/DE%

EQUATION 10

NEg/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;

NEg/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 AGRICULTURE

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):

EQUATION 11

NE/DE = 0.298 + (0.00335 x DE%)

EQUATION 12

NEg/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:

EQUATION 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;

{NEg/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.
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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:

EQUATION 14

Emissions (kg/yr) = [Intake (MJ/day) x Ym x (365 days/yr)] / [55.65 MJ/kg of

methane]

where Ym 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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.23

• methane-producing potential (Bo) of the manure (cubic metres (m3) 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

EQUATION 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 (Bo) varies by species and diet.

Country-specific data should be used where feasible. A range of representative Bo 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.
AGRICULTURE

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 m3

/kg VS

− Developing Countries: 0.13 m3

/kg VS

• Non-dairy Cattle

− Developed Countries: 0.17 m3

/kg VS

− Developing Countries: 0.10 m3

/kg VS

• Buffalo in all regions: 0.10 m3

/kg VS

• Swine

− Developed Countries: 0.45 m3

/kg VS

− Developing Countries: 0.29 m3

/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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.25

TABLE 4-8

MANURE MANAGEMENT SYSTEMS AND METHANE CONVERSION FACTORS (MCFS)

System MCF by Climatea 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.
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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 (Bo) 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 Bo for the animal type. In equation form, the estimate is as

follows:

EQUATION 16

EFi = VSi x 365 days/yr x Boi x 0.67 kg/m3 x

 jK

∑ MCFjK x MS% ijK

where:

EFi = annual emission factor (kg) for animal type i (e.g., dairy cows);

VSi = daily VS excreted (kg) for animal type i;

Boi = maximum methane producing capacity (m3/kg of VS) for manure

produced by animal type i;

MCFjk = 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 AGRICULTURE

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 (Bo) 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 N2O 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 N2O 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.

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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.

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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.31

TABLE A-1

DATA FOR ESTIMATING ENTERIC FERMENTATION EMISSION FACTORS FOR DAIRY CATTLE

Regions Weight

kg

Weight Gain

kg/day

Feeding Situation Milk

kg/day

Work

hrs/day

% Pregnant Digestibility of

Feed %

CH4 Conversion

%

North Americaa 600 0 Stall Fed 18.4 0 90% 65% 6%Western Europe 550 0 Stall Fed 11.5 0 90% 60% 6%Eastern Europeb 550 0 Stall Fed 7.0 0 80% 60% 6%Oceaniac 500 0 Stall Fed 4.7 0 80% 60% 6%Latin Americad 400 0 Pasture/Range 2.2 0 80% 60% 6%Asiae 350 0 Stall Fed 4.5 0 80% 60% 6%Africa & Middle East 275 0 Stall Fed 1.3 0 67% 60% 6%Indian Subcontinentf 275 0 Stall Fed 2.5 0 50% 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).
AGRICULTURE

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

TABLE A-2

DATA FOR ESTIMATING ENTERIC FERMENTATION EMISSION FACTORS FOR NON-DAIRY CATTLE

Type Weight

kg

Weight Gain

kg/day

Feeding Situation Milk

kg/day

Work

hrs/day

Pregnant

%

Digestibility of Feed

%

CH4 Conversion % Day Weighted Population

Mix %

Emission Factors

kg/head/yr

North Americaa

Mature 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% NA 0.0% 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% 37

Western Europe

Mature 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% 33

Eastern Europeb

Mature 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% 40

Oceaniac

Mature 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% 39

a Based on estimates for the United States.b Based on estimates for the former USSR.c Based on estimates for Australia.
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.33

TABLE A-2 (CONTINUED)

DATA FOR ESTIMATING ENTERIC FERMENTATION EMISSION FACTORS FOR NON-DAIRY CATTLE

Type Weight

kg

Weight Gain

kg/day

Feeding Situation Milk

kg/day

Work

hrs/day

Pregnant

 %

Digestibility of

Feed %

CH4

Conversion

 %

Day Weighted

Population Mix %

Emission Factors

kg/head/yr

Latin Americad

 Mature Females 400 0.0 Large Areas 1.1 0.0 67% 60% 6.0% 37% 58 Mature Males 450 0.0 Large Areas 0.0 0.0 0% 60% 6.0% 6% 57 Young 230 0.3 Large Areas 0.0 0.0 0% 60% 6.0% 58% 42

Asiae

 Mature Females-Farming 325 0.0 Stall Fed 1.1 0.55 33% 55% 6.5% 27% 48 Mature Females-Grazing 300 0.0 Pasture/Range 1.1 0.00 50% 60% 6.0% 9% 41 Mature Males-Farming 450 0.0 Stall Fed 0.0 1.37 0% 55% 6.5% 24% 58 Mature Males-Grazing 400 0.0 Pasture/Range 0.0 0.00 0% 60% 6.0% 8% 44 Young 200 0.2 Pasture/Range 0.0 0.00 0% 60% 6.0% 32% 31

Africa

 Mature Females 200 0.0 Stall Fed 0.3 0.55 33% 55% 6.5% 13% 31 Draft Bullocks 275 0.0 Stall Fed 0.0 1.37 0% 55% 6.5% 13% 40 Mature Females-Grazing 200 0.0 Large Areas 0.3 0.00 33% 55% 7.5% 6% 46 Bulls - Grazing 275 0.0 Large Areas 0.0 0.00 0% 55% 7.5% 25% 55 Young 75 0.1 Pasture/Range 0.0 0.00 0% 60% 6.0% 44% 14

Indian Subcontinentf

 Mature Females 125 0.0 Stall Fed 0.6 0.00 33% 50% 7.5% 40% 31 Mature Males 200 0.0 Stall Fed 0.0 2.74 0% 50% 7.5% 10% 41 Young 80 0.1 Stall Fed 0.0 0.00 0% 50% 6.0% 50% 17

d Based on estimates for the Brazil.e Based on estimates for the China.f Based on estimates for India.Source: Gibbs and Johnson (1993)
AGRICULTURE

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

TABLE A-3

DATA FOR ESTIMATING ENTERIC FERMENTATION EMISSION FACTORS FOR BUFFALO

Type Weight

kg

Weight Gain

kg/day

Feeding Situation Milk

kg/day

Work

hrs/day

Pregnant

 %

Digestibility

of Feed %

CH4

Conversion

%

Day

Weighed

Population

Mix

%

Emissions

Factors

kg/head/yr

Indian Subcontinenta

Adult Males 350 - 550 0.00 Stall Fed 0.00 1.37 0% 55% 7.5 14% 55 - 77Adult Females 250 - 450 0.00 Stall Fed 2.70 0.55 33% 55% 7.5 40% 57 - 80Young 100 - 300 0.15 Stall Fed 0.00 0.00 0% 55% 7.5 46% 23 - 50

Other Countriesb

Adult Males 350 - 550 0.00 Stall Fed 0.00 1.37 0% 55% 7.5 45% 55 - 77Adult Females 250 - 450 0.00 Stall Fed 0.00 0.55 25% 55% 7.5 45% 45 - 67Young 100 - 300 0.15 Stall Fed 0.15 0.00 0% 55% 7.5 10% 23 - 50a Based on estimates for India.b Based on estimates for China.Source: Gibbs and Johnson (1993).
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.35

TABLE A-4

DATA FOR ESTIMATING ENTERIC FERMENTATION EMISSION FACTORS FOR OTHER ANIMALS

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 AGRICULTURE

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 Bo 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.

4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.39

TABLE B-1

FEED INTAKE AND MANURE PRODUCTION FOR CATTLE

Region Livestock Category Sub-Population Mass

(kg)

Feed

Digest

 (%)

Energy

Intake

(MJ/day)

Feed

Intake

(kg/day)

Category

Population

%

Manure

(kg/h/d dm)

VS

 (kg/h/d)

Bo

(m3 CH4/kg

VS)

North America Dairy Cattle Average 600 65% 299.5 16.2 100% 5.68 5.23 0.24

Non-dairy Cattle Mature Females 500 60% 174.0 9.4 36% 3.77 3.47 0.17

Mature 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 0.17

Western Europe Dairy Cattle Average 550 60% 254.7 13.8 100% 5.52 5.08 0.24

Non-dairy Cattle Mature Males 600 60% 152.5 8.3 22% 3.31 3.04 0.17

Young 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 0.17
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4.40 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE B-1 (CONTINUED)

FEED INTAKE AND MANURE PRODUCTION FOR CATTLE

Region Livestock

Category

Sub-Population Mass

(kg)

Feed

Digestibility

 (%)

Energy

Intake

(MJ/day)

Feed Intake

(kg/day)

Category

Population

%

Manure

(kg/h/d dm)

VS

(kg/h/d)

Bo

 (m3 CH4/kg

VS)

Eastern Europe Dairy Cattle Average 550 60% 207.2 11.2 100% 4.49 4.13 0.24

Non-dairy Cattle Mature Females 500 60% 172.9 9.4 30% 3.75 3.45 0.17

Mature Males 600 60% 152.5 8.3 21% 3.31 3.04 0.17Young 230 60% 102.2 5.5 49% 2.22 2.04 0.17Avg. Non-dairy Cattle 391 60% 134.4 7.3 100% 2.91 2.68 0.17

Oceania Dairy Cattle Average 500 60% 174.1 9.4 100% 3.77 3.47 0.24

Non-dairy Cattle Mature Females 400 55% 160.5 8.7 52% 3.91 3.60 0.17

Mature Males 450 55% 138.8 7.5 10% 3.38 3.11 0.17Young 200 55% 98.6 5.3 38% 2.41 2.21 0.17Avg. Non-dairy Cattle 330 55% 134.9 7.3 100% 3.29 3.03 0.17

Latin America Dairy Cattle Average 400 60% 145.9 7.9 100% 3.16 2.91 0.13

Non-dairy Cattle Mature Females 400 60% 148.0 8.0 37% 3.21 2.95 0.10

Mature Males 450 60% 144.0 7.8 5% 3.12 2.87 0.10Young 230 60% 107.5 5.8 58% 2.33 2.14 0.10Avg. Non-dairy Cattle 305 60% 124.4 6.7 100% 2.70 2.48 0.10
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.41

TABLE B-1 (CONTINUED)

FEED INTAKE AND MANURE PRODUCTION FOR CATTLE

Region Livestock

Category

Sub-Population Mass

(kg)

Feed

Digestibility

(%)

Energy

Intake

(MJ/day)

Feed Intake

(kg/day)

Category

Population

%

Manure

(kg/h/d dm)

VS

(kg/h/d)

Bo

 (m3 CH4/kg

VS)

Africa & Middle East Dairy Cattle Average 275 60% 92.8 5.0 100% 2.01 1.85 0.13

Non-dairy Cattle Mature Females 200 55% 73.2 4.0 13% 1.79 1.64 0.10

Mature Males Draft 275 55% 93.2 5.1 13% 2.27 2.09 0.10Mature FemalesGrazing

200 55% 93.6 5.1 5% 2.28 2.10 0.10

Mature Males Grazing 275 55% 112.3 6.1 25% 2.74 2.52 0.10Young 75 60% 36.2 2.0 44% 0.78 0.72 0.10Avg. Non-dairy Cattle 173 57% 70.6 3.8 100% 1.68 1.54 0.10

Asia Dairy Cattle Average 350 60% 141.6 7.7 100% 3.07 2.82 0.13

Non-dairy Cattle Mature Females

Farming

325 55% 113.2 6.1 27% 2.76 2.54 0.10

Mature FemalesGrazing

300 60% 105.0 5.7 9% 2.28 2.09 0.10

Mature Males Farming 450 55% 134.9 7.3 24% 3.29 3.03 0.10Mature Males Grazing 400 60% 112.5 6.1 8% 2.44 2.24 0.10Young 200 60% 79.3 4.3 32% 1.72 1.58 0.10Avg. Non-dairy Cattle 319 57% 106.8 5.8 100% 2.49 2.29 0.10

Indian Dairy Cattle Average Dairy Cow 275 55% 117.7 6.4 100% 2.87 2.64 0.13Subcontinent Non-dairy Cattle Mature Females 125 50% 63.8 3.5 40% 1.73 1.59 0.10

Mature Males 200 50% 83.7 4.5 10% 2.27 2.09 0.10Young 80 50% 43.2 2.3 50% 1.17 1.08 0.10Avg. Non-dairy Cattle 110 50% 55.5 3.0 100% 1.50 1.38 0.10

Ash content estimated at 8%. Cattle characteristics from Gibbs and Johnson (1993).
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4.42 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE B-2

FEED INTAKE AND MANURE PRODUCTION FOR SWINE AND BUFFALO

Region Livestock

Category

Sub-Population Mass

(kg)

Feed

Digestibility

 (%)

Energy

Intake

(MJ/day)

Feed Intake

(kg/day)

Category

Population

%

Manure

(kg/h/d

dm)

VS

(kg/h/d)

Bo

(m3CH4/kg VS)

Developing Countries Swine Average 28 50% 13.0 0.7 100% 0.35 0.34 0.29Developed Countries Swine Average 82 75% 38.0 2.1 100% 0.51 0.50 0.45Indian Subcontinenta Buffalo Adult Males 450 55% 134.5 7.3 14% 3.28 3.02 0.10

Adult Females 350 55% 139.0 7.5 40% 3.39 3.12 0.10Young 200 55% 74.0 4.0 46% 1.80 1.66 0.10Average 295 55% 108.0 5.9 100% 2.65 2.43 0.10

Rest of Worldb Buffalo Adult Males 450 55% 134.5 7.3 45% 3.28 3.02 0.10

Adult Females 350 55% 114.0 6.2 45% 2.78 2.56 0.10Young 200 55% 74.0 4.1 10% 1.80 1.66 0.10Average 380 55% 119.0 6.5 100% 2.91 2.68 0.10

a 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).
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.43

TABLE B-3

MANURE MANAGEMENT EMISSION FACTOR DERIVATION FOR DAIRY CATTLE

Climate Manure Management System MCFs

Lagoon Liquid/

Slurry

Solid

Storage

Drylot Pasture/

Range

Daily

Spread

Digester Burned

for Fuel

Other

Cool 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%) EMISSION FACTORS

kg CH4 / hd / yr

Massa

(kg)

Bo

(m3CH4/kg Vs)

VSb

(kg/hd/day)

Cool Temperate Warm

North 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% MCF k o j j=1

all manure systems

jk ×× × × ∑
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4.44 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE B-4

MANURE MANAGEMENT EMISSION FACTOR DERIVATION FOR NON-DAIRY CATTLE

Climate Manure Management System MCFs

Lagoon Liquid /

Slurry

Solid

Storage

Drylot Pasture /

Range

Daily

Spread

Digester Burned

for Fuel

Other

Cool 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 Cattle

Characteristics

Manure Management System Usage (MS%) EMISSION FACTORS

kg CH4 / hd / yr

Massa

(kg)

Bo

(m3CH4

/kg VS)

VSb

(kg/hd/day) Cool Temperate Warm

North America 357 0.17 2.4 0% 1% 0% 14% 84% 0% 0% 0% 1% 1 2 3Western Europe 405 0.17 2.7 0% 50% 0% 2% 38% 0% 0% 2% 8% 6 20 38Eastern Europe 391 0.17 2.7 0% 28% 0% 0% 26% 0% 0% 0% 46% 4 13 23Oceania 330 0.17 3.0 3% 0% 0% 6% 91% 0% 0% 0% 0% 5 6 7Latin America 305 0.10 2.5 0% 0% 0% 0% 99% 0% 0% 0% 1% 1 1 1Africa 173 0.10 1.5 0% 0% 0% 1% 95% 1% 0% 3% 0% 0 1 1Middle East 173 0.10 1.5 0% 0% 0% 1% 79% 2% 0% 17% 2% 1 1 1Asia 319 0.10 2.3 0% 0% 0% 46% 50% 2% 0% 2% 0% 1 1 2Indian Subcontinent 110 0.10 1.4 0% 1% 0% 4% 22% 20% 1% 53% 0% 2 2 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% MCF ko j

j=1

all manure systems

jk ×× × × ∑
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.45

TABLE B-5

MANURE MANAGEMENT EMISSION FACTOR DERIVATION FOR BUFFALO

Climate Manure Management System MCFs

Liquid/

Slurry

Drylot Pasture/

Range

Daily Spread Digester Burned for

Fuel

Other

Cool 10.0% 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%

Warm 65.0% 5.0% 2.0% 1.0% 10.0% 10.0% 1.0%

Region Buffalo Characteristics Manure Management System Usage (MS%) EMISSION FACTORS

kg CH4 / hd / yr

Massa

kg

Bo

m3CH4

/kg VS

VSb

kg/hd/day Cool Temperate Warm

North 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 3IndianSubcontinent

295 0.10 3.1 0% 4% 19% 21% 1% 55% 0% 4 5 5

a 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% MCF ko j

j=1

all manure systems

jk ×× × × ∑
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4.46 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE B-6

MANURE MANAGEMENT EMISSION FACTOR DERIVATION FOR SWINE

Climate Manure Management Systems MCFs

Lagoon Liquid/

Slurry

Solid

Storage

Drylot Pit

 <1 month

Pit

>1 month

Daily

Spread

Digester Other

Cool 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%) EMISSION FACTORS

kg CH4 / hd / yr

Massa

kg

Bo

m3CH4

/kg VS

VSb

kg/hd/day Cool Temperate Warm

North America 82 0.45 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 82 0.45 0.5 54% 0% 3% 15% 0% 0% 0% 0% 28% 20 20 20Latin America 28 0.29 0.3 0% 8% 10% 41% 0% 0% 2% 0% 40% 0 1 2Africa 28 0.29 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 28 0.29 0.3 0% 40% 0% 54% 0% 0% 0% 7% 0% 1 4 7IndianSubcontinent

28 0.29 0.3 9% 22% 16% 30% 3% 0% 9% 8% 3% 3 4 6

a 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% MCF ko j

j=1

all manure systems

jk ×× × × ∑
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.47

TABLE B-7

MANURE MANAGEMENT EMISSION FACTOR DERIVATION FOR OTHER LIVESTOCK

Animal Animal Characteristics Manure Management System

MCFsa

Emission Factorsa

kg CH4 / hd / yr

Mass

 (kg)

Digest

(%)

Intake/d

(kg Feed)

% Ash

(Dry Basis)

VS/day

(kg VS)

Bo

(m3/kg VS)

MCF

Cool

MCF

Temperate

MCF

Warm

Cool Temperate Warm

Sheep Developed Countries 43 60% 1.08 8.0 0.40 0.19 1% 1.5% 2% 0.19 0.28 0.37

Developing Countries 28 50% 0.70 8.0 0.32 0.13 1% 1.5% 2% 0.10 0.16 0.21

Goats Developed Countries 30 60% 0.76 8.0 0.28 0.17 1% 1.5% 2% 0.12 0.18 0.23

Developing Countries 30 50% 0.76 8.0 0.35 0.13 1% 1.5% 2% 0.11 0.17 0.22

Camels Developed Countries 217 50% 5.42 8.0 2.49 0.26 1% 1.5% 2% 1.59 2.38 3.17

Developing Countries 217 50% 5.42 8.0 2.49 0.21 1% 1.5% 2% 1.28 1.92 2.56

Horses Developed Countries 238 70% 5.96 4.0 1.72 0.33 1% 1.5% 2% 1.39 2.08 2.77

Developing Countries 238 70% 5.96 4.0 1.72 0.26 1% 1.5% 2% 1.09 1.64 2.18

Mule/Asses Developed Countries 130 70% 3.25 4.0 0.94 0.33 1% 1.5% 2% 0.76 1.14 1.51

Developing Countries 130 70% 3.25 4.0 0.94 0.26 1% 1.5% 2% 0.60 0.90 1.19

Poultryb Developed Countries 1.1 NRc NR NR 0.10 0.32 1% 1.5% 2% 0.078 0.117 0.157

Developing Countries NR NR NR NR 0.02 0.24 1% 1.5% 2% 0.012 0.018 0.023

a 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 and

25°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 Bo

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 Woodburyand Hashimoto (1993). Emission factors for poultry are based on Safley et al. (1992) and Woodbury and Hashimoto (1993).

4 AGRICULTURE

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)

NEm = (1.37 x ME) - (0.138 x ME2

) + (0.0105 x ME3) - 1.12 (C.2)

NEg = (1.42 x ME) - (0.174 x ME2

) + (0.0122 x ME3) - 1.65 (C.3)

where:

DE = digestible energy in Mcal/kg (dry matter basis);

ME = metabolisable energy in Mcal/kg (dry matter basis);

NEm = net energy for maintenance in Mcal/kg (dry matter basis); and

NEg = net energy for growth in Mcal/kg (dry matter basis).

Using these relationships, the ratio of NEm and NEg 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)

NEg/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;

NEg/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%).
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4.50 Revised 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 NEm: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 NEg: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)

NEg/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 AGRICULTURE

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

(CH4), 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 CH4, 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 CH4, 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 CH4 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 CH4 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 CH4 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 CH4 production in flooded soils are the reduction of CO2 with

H2, 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 CH4 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.
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4.54 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

The redox15 potential is one important factor for production of CH4 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 CH4 production. Yamane and Sato (1964) also showed that the evolution

of CH4 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 CH4 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 CH4 formation reached a maximum at

35o

C in waterlogged alluvial soils. The rate of methane formation was very small below

20o

C.

Because the conversion rate of substrate to CH4 depends on the temperature, it is

generally observed that the momentary local emission of CH4 from the soil to the

atmosphere depends on the temperature. However, the dependence of the seasonally

integrated emissions of CH4 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 CH4, that time is generally short compared

to a season. Thus the methodology proposed here will be based on the seasonally

integrated CH4 emission, whose temperature dependence can be neglected in first

approximation.

It is generally recognised that CH4 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 Fe3+ to Fe2+ which simultaneously reduces the Eh.

The addition of nitrate as chemical fertiliser to flooded soils may suppress the production

of CH4, because nitrate acts, as well as Fe3+, Mn4+, 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 CH4 release into the atmosphere from rice fields. Diffusion

loss of CH4 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 CH4 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 CH4 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 AGRICULTURE

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 CH4 in the soil. Part

of the CH4 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 CH4 as their sole energy source, and other soil bacteria, such as

Nitrosomonas species are also able to consume CH4 (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 CH4 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.
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4.56 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 4-9

REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE WORLD

 Country Location Range of CH4

flux

mg/m2/hr

Season total

g/m2

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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.57

TABLE 4-9 (CONT.)

REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE WORLD

 Country Location Range of CH4

flux

mg/m2/hr

Season total

g/m2

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

TABLE 4-9 (CONT.)

REPRESENTATIVE METHANE EMISSIONS FROM RICE PADDY FIELDS IN VARIOUS LOCATIONS OF THE WORLD

 Country Location Range of CH4

flux

mg/m2/hr

Season total

g/m2

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 CH4 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 CH4 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 CH4/yr. Rice paddies are listed as a source of 60 ± 40 Tg CH4/yr.
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.59

TABLE 4-10

REPRESENTATIVE GLOBAL ANNUAL METHANE EMISSIONS

FROM RICE FIELDS AS ESTIMATED BY DIFFERENT AUTHORS*

Reference Estimate (Tg CH4/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)
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4.60 Revised 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:

EQUATION 1

Fc = EF × A × 10-12

where:

Fc = 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/m2;

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 m2/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:

EQUATION 2

F = ∑i ∑j ∑k EFijk 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 CH4 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 AGRICULTURE

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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.
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4.62 Revised 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 (m2). 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 data

In 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/m2. 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/m2 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/m2 (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 AGRICULTURE

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 CH4 m2/yr to 68.4 g CH4 m2/yr with added rice

straw, (a factor of 2.4). Cicerone et al. (1992) observed increases from a control value of

1.4 g CH4 m2/yr to up to 58.2 g CH4 m2/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/m2 to

4.86 g/m2). 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/m2) 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/m2 and 8.6 g/m2 for

1991 and 9.5 g/m2 and 5.2 g/m2 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.
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4.64 Revised 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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.65

TABLE 4-11

DEFAULT ACTIVITY DATA - HARVESTED RICE

Country or Region 1990 Area

(1000s ha)

Irrigateda

(%)

Upland Rice

(%)

Rainfedb

(%)

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

TABLE 4-11 (CONT.)

DEFAULT ACTIVITY DATA - HARVESTED RICE

Country or Region 1990 Area

(1000s ha)

Irrigateda

(%)

Upland Rice

(%)

Rainfedb

(%)

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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.67

TABLE 4-11 (CONT.)

DEFAULT ACTIVITY DATA - HARVESTED RICE

Country or Region 1990 Area

(1000s ha)

Irrigateda

(%)

Upland Rice

(%)

Rainfedb

 (%)

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

TABLE 4-11 (CONT.)

DEFAULT ACTIVITY DATA - HARVESTED RICE

Country or Region 1990 Area

(1000s ha)

Irrigateda

(%)

Upland Rice

(%)

Rainfedb

(%)

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 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.69

TABLE 4-12

SCALING FACTORS FOR METHANE EMISSIONS FOR RICE ECOSYSTEMS RELATIVE TO CONTINUOUSLY FLOODED FIELDS

(WITHOUT ORGANIC AMENDMENTS)

Category Sub-Categorya Scaling Factors (relative to emission

factors for continuously flooded fields)

Upland None 0

Lowland Irrigated Continuously flooded 1.0

Intermittently

floodedb

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/m2 (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.
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4.70 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 4-13

SEASONALLY INTEGRATED METHANE EMISSION FACTORS FOR CONTINUOUSLY FLOODED RICE WITHOUT ORGANIC FERTILISER

IN VARIOUS LOCATIONS OF THE WORLD

Country Seasonally Integrated Emission

Factor, EFa

(g/m2)

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 AGRICULTURE

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).

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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 CO2 emissions. However, in agricultural burning, the CO2 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 CO2 are considered to be zero.

Agricultural burning releases other gases in addition to CO2 which are by-products of

incomplete combustion: methane, carbon monoxide, nitrous oxide, and oxides of

nitrogen, among others. These non-CO2 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-CO2 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-CO2

trace gas emissions can be based on ratios to the total carbon released. The carbon

trace gas releases (CH4 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 N2O and NOx are estimated based on ratios of

these gases to total nitrogen released. Tables 4-15 and 4-16 provide suggested default

values for non-CO2 trace gas emission ratios. These are presented with ranges, which

 

 16 For biomass combustion, CO2 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 CO2. That is, a portion of

carbon in biomass is being released as net emissions of CH4 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 CH4, so that an amount less

than the total CO2 which was taken up by the plants is re-emitted as CO2. See Howden

et al. (1996), for a more detailed discussion of this proposal. Treating emissions of CO

and CH4 to the atmosphere, as a sink for atmospheric CO2, however, is inconsistent with

the proposed IPCC emissions methodology. In particular, the other carbon compounds

emitted are converted back into CO2 in the atmosphere over periods of days up to a

decade or so. Thus, over the time horizons of interest for CO2, (i.e. more than 100

years) there is no sink of CO2.
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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. CO2, N2O,

and NOx are mainly emitted in the flaming stage, while CH4 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.
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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 CO2, 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 (CH4), carbon monoxide (CO), nitrous oxide (N2O), oxides of nitrogen (NOx,

i.e., NO and NO2) 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-CO2 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-CO2 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 area20 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.
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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).

TABLE 4-14

REGIONAL SAVANNA STATISTICS

Regiona

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

0.05-0.15b

0.25-0.50b

0.25-0.50b

0.60-0.80b

6.6 ±1.6

0.5-2.5b

2-4b

3-6b

4-8b

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 areas

burned 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).
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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
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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:

EQUATION 1

Area of Savanna Burned Annually (ha)

=

Total Area of Savanna (ha) x Fraction Burned Annually

EQUATION 2

Biomass Burned (t dm)

=

Area of Savanna Burned Annually (ha)

x Aboveground Biomass Density (t dm/ha) x Fraction Actually Burned

EQUATION 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)

EQUATION 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.
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EQUATION 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.
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Step 2: Emissions

Once the carbon released from savanna burning has been estimated, the emissions of

CH4, CO, N2O, and NOx 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 CH4 and CO relative to total carbon released to yield emissions of

CH4 and CO (each expressed in units of C). The emissions of CH4 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 N2O and NOx, 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 N2O and NOx relative to the N

released to yield emissions of N2O and NOx (expressed in units of N). To convert to full

molecular weights, the emissions of N2O and NOx are multiplied by 44/28 and 46/14,

respectively.25

The non-CO2 trace gas emissions calculations from burning are summarised as follows:

CH4 Emissions = (carbon released) x (emission ratio) x 16/12

CO Emissions = (carbon released) x (emission ratio) x 28/12

N2O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28

NOx Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 46/14

TABLE 4-15

EMISSION RATIOS FOR SAVANNA BURNING CALCULATIONS

Compound Ratios

CH4 a

CO b

N2O c

NOx 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., CH4 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 N2O the ratio is 44/28 and for NOX it

is 46/14. NO2 has been used as the reference molecule for NOX.
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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 (CO2) 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 CH4, CO, NOx, and N2O. This section

accounts for emissions of these non-CO2 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 CH4 and CO to total carbon released, and of N2O

and NOx 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.).
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• 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
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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 CH4, CO, N2O, and NOx 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 CH4 and CO relative to total carbon to

yield emissions of CH4 and CO (each expressed in units of C). The emissions of CH4

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 N2O and NOx, 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 N2O and NOx relative to the N content of the fuel to yield emissions of

N2O and NOx (expressed in units of N). To convert to full molecular weights, the

emissions of N2O and NOx are multiplied by 44/28 and 46/14, respectively.31

The calculation for trace gas emissions from burning is summarised as follows:

CH4 Emissions = Carbon Released x (emission ratio) x 16/12

CO Emissions = Carbon Released x (emission ratio) x 28/12

N2O Emissions = Carbon Released x (N/C ratio) x (emission ratio) x 44/28

NOx 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 N2O the ratio is 44/28 and for NOX it

is 46/14. NO2 has been used as the reference molecule for NOX.
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TABLE 4-16

EMISSION RATIOS FOR AGRICULTURAL RESIDUE BURNING

CALCULATIONS

Compound Ratios

CH4 a

CO b

N2O c

NOx 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., CH4 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.
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TABLE 4-17

SELECTED CROP RESIDUE STATISTICS

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 0.4072a

Sugarbeet 0.2 0.10-0.20 a 0.4072a

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-CO2 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 N2O and NOx. 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
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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.
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4.5 Greenhouse Gas Emissions from

Agricultural Soils

4.5.1 Introduction

Agricultural soils may emit or remove nitrous oxide (N2O), carbon dioxide (CO2), and/or

methane (CH4).

This section presents the method for calculating national emissions of N2O from

agriculture soils. This N2O 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 N2O, the 1995 Methodology was evaluated and the present method includes more

sources of N2O and more explicit information about emission factors. Three sources of

N2O 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) N2O 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 N2O 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 N2O 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 (NOx) are also emitted from agricultural

systems and may be transported off-site and serve to fertilise other systems which leads

to enhanced production of N2O.

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 N2O 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

N2O 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 N2O 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 N2O–N emissions for the year 1989 were estimated. Direct emissions
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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 N2O–N. These estimates show that each

of the three components of agriculture considered contribute about the same amount of

N2O to the global atmospheric budget. The N2O 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 N2O can be biogenic (e.g., enhanced N2O 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 N2O 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 N2O 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 N2O formation. Most studies

on N2O emissions from agricultural soils investigate the difference in N2O 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 N2O 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 N2O.
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All of these N2O sources are included in the methodology, except for sewage sludge

application and the soil sink for N2O. These sources and sinks are not estimated because

emissions are negligible or data are insufficient.

Synthetic fertilisers

Synthetic fertilisers are an important source of N2O. 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 N2O 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 N2O (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

DEFAULT EMISSION FACTORS FOR DIRECT EMISSIONS OF N2O

EF1 (fraction of N-input, kg N2O-N/kg N) 0.0125 (0.0025-0.0225)a

EF2 (kg N2O-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 NH3 volatilisation and emission of

nitric oxide (NO) through nitrification after fertiliser is applied to fields, NH3

volatilisation and NO emission factors are needed. Even though climate, soil, fertiliser

placement and type, and other factors influence NH3 volatilisation and NOx emissions, a

default emission factor of 0.1 (kg NH3–N + NOx–N emitted/kg N applied) can be used

for synthetic fertilisers and 0.2 (kg NH3–N + NOx–N emitted/kg N applied) for animal

waste fertiliser (Table 4-19) (0.2 is used for animal waste because of the potentially larger

NH3 volatilisation; see Section 4.5.4). The amount of nitrogen from these sources

available for conversion to N2O 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 N2O 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
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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 N2-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 N2O formation.

Galbally et al. (1992) and Bouwman and Sombroek (1990) indicate that legumes may

contribute to N2O emission in a number of ways. Atmospheric N2 fixed by legumes can

be nitrified and denitrified in the same way as fertiliser N, thus providing a source of

N2O. Additionally, symbiotically living Rhizobia in root nodules are able to denitrify and

produce N2O (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 N2O emissions from pastures by a factor of 2 or 3. More recently Carran

et al. (1995) found annual N2O emissions ranging from 0.5 to 5 kg N2O–N depending

upon the relative fertility of the sampling location. In old and young rye grass/clover

pastures Muller (personal communication) observed N2O 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 N2O emissions derived from nitrogen fixation.

Total nitrogen input (FBN, 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 (FracNCRBF, 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 N2O produced in legume pastures. This N2O 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 includes 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 N2O is not known. To account for the N2O in the inventory

budget 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 (FCR). 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 (FracNCRBF and FracNCR0; 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.
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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 N2O emissions from glasshouse

crops may be relatively small. Postma et al. (1994) quantified NH3 and N2O emissions

from glasshouse cultivation of lettuce on a sandbed and found that NH3 emissions and

N2O emitted directly or in drainage water totalled less than 0.01 kg N/kg of nitrogen

applied. Daum (personal communication, 1995) measured N2O emissions from soil-less

culture cucumbers and found that N-loss rates as N2O ranged between 0.004 and 0.009

kg N/kg of nitrogen input into the culture system. Pollaris (1994) measured N2O

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 N2O. The importance of another

factor, N2O emission during steam disinfection of glasshouse soils, is uncertain. Postma

(personal communication, 1995) found that 2-25 kg N2O-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 N2O emissions from glasshouse agriculture do

not need to be included separately in N2O 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 N2O 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 N2O due to cultivation is estimated to

be 2-15 kg N2O-N/ha/yr of cultivated Histosol. Default emission values of 5 and 10 kg

N2O-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 N2O

Aerobic soils are typically sources for N2O, 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 N2O to N2

(Erich et al., 1984), since the major product of denitrification in soils is usually N2 rather

than N2O. However, no large, constant N2O 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 N2O in wet or flooded soils prevent this

process from being a significant regulator of atmospheric N2O. Until additional

information is available to indicate that soil uptake, in aerobic or flooded soils, is

important, soil uptake of atmospheric N2O will not be included in the N2O budget for

agricultural systems.
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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 N2O emissions from agricultural

fields includes consideration of synthetic fertiliser (FSN), nitrogen from animal waste

(FAW), enhanced N2O production due to biological N-fixation (FBN), nitrogen from crop

residue mineralisation (FCR) and soil nitrogen mineralisation due to cultivation of

Histosols (FOS). For futher information see: Bouwman (1994, 1995); Mosier (1994);

Mosier et al. (1995a;b).

In this estimate, the total direct annual N2O emission is:

EQUATION 1

N2ODIRECT = [(FSN + FAW + FBN + FCR) x EF1] + FOS x EF2

where:

N2ODIRECT = direct N2O emissions from agricultural soils in country

(kg N/yr);

EF1 = emission factor for direct soil emissions

(kg N2O-N/kg N input) (see Table 4-18);

EF2 = emission factor for organic soil mineralisation due to

cultivation (kg N2O-N ha/yr) (see Table 4-18);

FOS = area of cultivated organic soils within country

(ha of histosols in FAO data base);

FAW = manure nitrogen used as fertiliser in country, corrected for NH3

and NOx emissions and excluding manure produced during grazing

(kg N/yr);

FBN = N fixed by N-fixing crops in country (kg N/yr);

FCR = N in crop residues returned to soils in country (kg N/yr);

FSN = synthetic nitrogen applied in country (kg N/yr);

FSN = NFERT x (1-FracGASF);

FAW = (Nex x (1-(FracFUEL + FracGRAZ + FracGASM));

FBN = 2 x CropBF x FracNCRBF;

FCR = 2 x [Crop0 x FracNCR0 + CropBF x FracNCRBF] x (1-FracR) x

(I-FracBURN);

and

NFERT = synthetic fertiliser use in country (kg N/yr);
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FracGASF = fraction of synthetic fertiliser nitrogen applied to soils that

volatilises as NH3 and NOx (kg NH3-N and NOx-N/kg of N

input) (see Table 4-19);

Nex = amount of nitrogen excreted by the livestock within a country (kg

N/yr) (see Table 4-20);

FracFUEL = fraction of livestock nitrogen excretion contained in excrements

burned for fuel (kg N/kg N totally excreted)

FracGRAZ = fraction of livestock nitrogen excreted and deposited onto soil

during grazing (kg N/kg N excreted) country estimate;

FracGASM = fraction of livestock nitrogen excretion that volatilises as NH3 and

NOx (kg NH3-N and NOx-N/kg of N excreted) (see Table 4-19);

CropBF = seed yield of pulses + soybeans in country (kg dry biomass/yr);

FracNCRBF = fraction of nitrogen in N-fixing crop (kg N/kg of dry biomass) (see

Table 4-19);

Crop0 = production of all other (i.e., non-N fixing) crops in country (kg

dry biomass/yr);

FracNCR0 = fraction of nitrogen in non-N-fixing crop (kg N/kg of dry biomass)

(see Table 4-19);

FracR = fraction of crop residue that is removed from the field as crop (kg

N/kg crop-N) (see Table 4-19);

FracBURN = 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 (NFERT),

manure-N used as fertiliser (FAW), edible crop production of N-fixing crops (CropBF) and

non-N-fixing crops (Crop0), 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 (FAW) 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 NH3 volatilised and NOx 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 FAW 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).
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TABLE 4-19

DEFAULT VALUES FOR PARAMETERS

FracBURN 0.25 in developing and 0.10 or less in developed countries

(kg N/kg crop-N);

FracR 0.45 kg N/kg crop-N;

FracFUEL 0.0 kg N/kg N excreteda;

FracGASF 0.1 kg NH3-N + NOx-N/kg of synthetic fertiliser N applied;

FracGASM 0.2 kg NH3-N + NOx-N/kg of N excreted by livestock;

FracGRAZ Table 4-21, Column Pasture range and Paddock a;

FracNCRBF 0.03 kg N/kg of dry biomass;

FracNCR0 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 N2O 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 N2O 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) N2O from animals

Animals themselves may be very small sources of N2O. 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 (NO3) 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 NH3/NH4

+

. The nitrate reduction reaction may release

small amounts of N2O in the gut (Kaspar and Tiedje, 1981), which may escape to the

atmosphere during rumination. Though this possible route of N2O formation has been

known for over 10 years, quantitative data in terms of N2O release are still lacking todate. The total amount of N2O released by cattle is probably very small, because the gut

is highly anoxic and this will favour the formation of NH3/NH4

+

 (Tiedje, 1988). Direct

losses from animals themselves are likely to be very small and are therefore not discussed

further.
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B) N2O 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 NH3/NH4

+

, before it can be the substrate of nitrifiers and denitrifiers and

hence, a source of N2O. 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 NH3/NH4

+

 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 NH3/NH4

+

 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 N2O 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 N2O production to increase with increasing aeration. Aeration initiates the

nitrification-denitrification reactions, and hence makes release of N2O possible.

Unfortunately, there is not enough quantitative data to derive a relationship between the

degree of aeration and N2O emission from slurry during storage and treatment.

Losses of N2O 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 N2O N/kg nitrogen in

slurry during 6 months (Oenema and Velthof, 1993). N2O 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 N2O 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 N2O-N/kg nitrogen excreted for full and half slit floor, and reduced and

deep litter; 7.4 10-3 kg N2O-N/kg nitrogen excreted for deep litter combined with

compost; and 3.3 10-3 kg N2O-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
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slurry was emitted as N2O from deep-litter systems for fattening pigs during a 4-month

measuring period. Large N2O 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 N2O during a four-day treatment period.

Losses of N2O from large lagoons with pig slurry in south-eastern United States were

negligible (Harper, personal communication). Concentration profiles of N2O above the

lagoon suggest that absorption of N2O from the atmosphere by the pig slurry in the

lagoon may occur.

Losses of N2O 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 N2O emission from The Netherlands, Kroeze (1994) included N2O

emissions from stables. She distinguished four classes, kg N2O-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 N2O emissions from

livestock holdings, but did not include N2O 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 N2O emission from wastes during storage and treatment,

and N2O emission from wastes after deposition or spreading onto the land.

In conclusion, there is very limited information available on N2O emissions from animals

and from animal waste during storage and treatment. Moreover, there is a wide range in

estimated losses, when expressed in N2O 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 N2O production may be affected by

waste spreading and waste processing, available data are too scarce to base a new

method on.

C) N2O from animal grazing

A brief summary of estimates of N2O emissions derived from dung and urine deposits of

grazing animals is compiled in Appendix A, Table A-1. The N2O 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

N2O 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 N2O losses from animal excrements (Van

Cleemput et al., 1994; Velthof et al., submitted a;b).
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Grazing derived emissions range from 0.002 to 0.098 kg N2O–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 N2O emissions are likely in the

range of 0.002-0.01 kg N2O–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 N2O 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 N2O–N was emitted

as N2O. They did find in later studies that N2O 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 N2O–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 N2O 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. N2O

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. N2O

emissions from other animal waste management systems (AWMS) are not directly
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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 N2O from animal production and agricultural soils are

described here as part of the N-cycle. Caution must be applied in reporting N2O

emissions under the appropriate source categories defined above.

EQUATION 2

N2OANIMALS = N2O(AWMS)=∑[ N(T) x Nex(T) x AWMS(T) x EF3(AWMS)]

where:

N2OANIMALS = N2O emissions from animal production in a country (kg N/yr)

N2O(AWMS) = N2O emissions from Animal Waste Management Systems in

the country (kg N/yr);

= [N(T=1) x Nex(T=1) x AWMS(T=1) x EF3(AWMS)]+ ...

+ [N(T=TMAX) x Nex(T=TMAX) x AWMS(T=TMAX) x EF3(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 NEX(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);

EF3(AWMS) = N2O emission factor for an AWMS (kg N2O-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.
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TABLE 4-20

TENTATIVE 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 N2O

Current available information suggests that some N2O may be released directly from

animals. However, the rate of release is probably low. A value less than 0.1 g N2O–N/kg

nitrogen excreted would result in a global N2O 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 N2O emission from animal wastes during storage and

treatment. The data provided per country in Safley et al. (1992) could be used for

estimating N2O 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;
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• Used for fuel;

• Other systems.

N2O 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 N2O 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 N2O, because this possible

source of N2O 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 N2O emitted from wastes

in the class 'Used for fuel', if not properly corrected. While significant N2O losses may

occur during burning, no N2O 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.
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TABLE 4-21

DEFAULT VALUES FOR PERCENTAGE OF MANURE N PRODUCED IN DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS

(FROM SAFLEY ET AL., 1992)

Region Type of Animal % of Manure Production per Animal Waste Management Systems

AnaerobicLagoon

LiquidSystem

Daily Spread

Solid Storageand Drylot

Pasture Rangeand Paddock

Used Fuel Other

System

North America Non-dairy Cattle (D) 0 1 0 14 84 0 1

Dairy Cattle 10 23 37 23 0 0 7Poultry (E) 5 4 0 0 1 0 90Sheep 0 0 0 2 88 0 10Swine 25 50 0 18 0 0 6Other animals (F) 0 0 0 0 92 0 8

Western Europe Non-dairy Cattle (D) 0 55 0 2 33 0 9

Dairy Cattle 0 46 24 21 8 0 1Poultry (E) 0 13 0 1 2 0 84Sheep 0 0 0 2 87 0 11Swine 0 77 0 23 0 0 0Other animals (F) 0 0 0 0 96 0 4

Eastern Europe Non-dairy Cattle (D) 8 39 0 52 0 0 1

Dairy Cattle 0 18 1 67 13 0 0Poultry (E) 0 28 0 0 1 0 71Sheep 0 0 0 0 73 0 27Swine 0 29 0 0 27 0 45Other animals (F) 0 0 0 0 92 0 8
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TABLE 4-21 (CONTINUED)

DEFAULT VALUES FOR PERCENTAGE OF MANURE N PRODUCED IN DIFFERENT ANIMA WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS

(FROM SAFLEY ET AL., 1992)

Region Type of Animal % of Manure Production per Animal Waste Management Systems

AnaerobicLagoon

LiquidSystem

Daily Spread

Solid Storageand Drylot

Pasture Rangeand Paddock

UsedFuel

Other System

Oceania Non-dairy Cattle (D) 0 0 0 0 100 0 0

Dairy Cattle 0 0 0 0 100 0 0Poultry (E) 0 0 0 0 3 0 98Sheep 0 0 0 0 100 0 0Swine 55 0 0 17 0 0 28Other animals (F) 0 0 0 0 100 0 0

Latin America Non-dairy Cattle (D) 0 0 0 0 99 0 1

Dairy Cattle 0 1 62 1 36 0 0Poultry (E) 0 9 0 0 42 0 49Sheep 0 0 0 0 100 0 0Swine 0 8 2 51 0 0 40Other animals (F) 0 0 0 0 99 0 1

Africa Non-dairy Cattle (D) 0 0 1 3 96 0 0

Dairy Cattle 0 0 12 0 83 0 5Poultry (E) 0 0 0 0 81 0 19Sheep 0 0 0 1 99 0 1Swine 0 7 0 93 0 0 0Other animals (F) 1 0 0 0 99 0 1
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TABLE 4-21 (CONTINUED)

DEFAULT VALUES FOR PERCENTAGE OF MANURE N PRODUCED IN DIFFERENT ANIMA WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD

REGIONS (FROM SAFLEY ET AL., 1992)

Region Type of Animal % of Manure Production per Animal Waste Management Systems

Anaerobic

Lagoon

Liquid

System

Daily

 Spread

Solid

Storage and

Drylot

Pasture

Range and

Paddock

Used Fuel Other

System

Near East andMediterranean

Non-dairy Cattle (D) 0 0 2 0 77 18 2

Dairy Cattle 0 0 3 3 77 18 0Poultry (E) 0 1 0 0 71 0 28Sheep 0 0 0 0 100 0 0Swine 0 32 0 68 0 0 0Other animals (F) 0 0 0 0 100 0 0

Asia and Far East Non-dairy Cattle (D) 0 0 16 14 29 40 0

Dairy Cattle 6 4 21 0 24 46 0Poultry (E) 1 2 0 0 44 1 52Sheep 0 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
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Tentative (default) emission factors (EF3) 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

TENTATIVE DEFAULT VALUES FOR N2O EMISSION FACTORS FROM ANIMAL WASTE PER ANIMAL

WASTE MANAGEMENT SYSTEM,

KG N2O–N/KG NITROGEN EXCRETED

Animal Waste Management Systema Emission Factor EF3

Anaerobic lagoonsb 0.001 (<0.002)

Liquid systemsb 0.001 (<0.001)

Daily spreadc 0.0 (no range)

Solid storage and drylotc 0.02 (0.005-0.03)

Pasture range and paddock (grazing)d 0.02 (0.005-0.03)

Used as fuele Not included in this Chapter

Other systemsb 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 NH3 and NOx (originating

from the application of fertilisers);

B. Nitrogen leaching and runoff;

C. Human consumption of crops followed by municipal sewage treatment;

D. Formation of N2O in the atmosphere from NH3;

E. Food processing.

Of these pathways, methodologies for estimating N2O emissions from A-C are proposed.

Nitrous oxide emissions from human waste are described below. However, these N2O

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.
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In order to estimate the associated N2O fluxes, the following data are needed:

• Synthetic nitrogen fertiliser consumption (NFERT). This is available by country from

FAO yearbooks and is probably the most reliable piece of input data.

• Livestock nitrogen excretion (Nex) 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 (NrPEOPLE). 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 NH3 and NOx (kg N/yr) are estimated from fertiliser use and livestock

nitrogen excretion.

These N2O–N emissions are to be calculated from a country's NOx and NH3 emissions

and nitrogen transported in leaching and runoff, so that all N2O formed as a result of

NOx and NH3 emissions and leaching and runoff in country Z are assigned to country Z,

even if the actual N2O formation takes place in another country. This implies that NOx

and NH3 and nitrogen from leaching and runoff imported into a country is not included in

the calculations.

A. Atmospheric deposition of NOx and NH3

Atmospheric deposition of nitrogen compounds such as nitrogen oxides (NOx) and

ammonium (from NH3) fertilise soils and surface waters and as such enhance biogenic

N2O 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), N2O

emissions from German forest soils were enhanced by up to a factor of 5. Reported

rates of N2O emissions are between 0.002 and 0.016 kg N2O–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 N2O-N

emissions as 0.01 kg N2O-N /kg of NOx-N and NH3-N emitted annually within a country

(EF4, Table 4-23).

TABLE 4-23

DEFAULT EMISSION FACTORS FOR INDIRECT EMISSIONS

EF4 (N deposition) = 0.01 (0.002-0.02) kg N2O-N/kg NH3-N and NOX–N emitted

EF5 (leaching/runoff) = 0.025 (0.002-0.12) kg N2O-N/kg N leaching/runoff

EF6 (sewage) = 0.01 (0.002-0.02) kg N2O-N/kg sewage-N produced

Agricultural ammonia emissions can be derived from NH3 volatilisation studies. Animal

manure (dung + urine) is one of the most important sources of NH3. According to Van

der Hoek (1994), up to 50 per cent of the mineral nitrogen in animal manure (i.e., about
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25 per cent of total N) may be lost shortly as NH3 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 NH3 soon after application. The amount of NH3

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 NH3 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 NH3. 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 NH3

and NOx 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 (FracGASF and FracGASM,

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

N2O as the nitrogen undergoes nitrification and denitrification.

The fraction of the fertiliser and manure nitrogen lost to leaching and surface runoff

(FracLEACH) 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:

EQUATION 3

NLEACH = [NFERT + NEX] x FracLEACH

The sum of the emission of N2O due to NLEACH in: 1) groundwater and surface drainage

(EF5-g), 2) rivers (EF5-r), and 3) coastal marine areas (EF5-e) is calculated to obtain the

N2O emission factor (EF5) for NLEACH. 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.

TABLE 4-24

DEFAULT VALUES OF PARAMETERS FOR INDIRECT EMISSIONS

FracNPR 0.16 kg N/kg of protein

FracLEACH 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 N2O 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 N2O in these waters including the amount of nitrogen leaching into the
4 AGRICULTURE

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 NO3-N. A review of the

literature indicates that while the range of N2O concentrations reported is large, there is

some relationship between the concentration of N2O-N and NO3-N in groundwater and

agricultural drainage water. The ratio of N2O-N to NO3-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 N2O-N to NO3-N in agricultural

drainage ditches and groundwater under agricultural fields ranged from approximately

0.0003 to 0.06. The ratios of N2O-N to NO3-N in agricultural drainage ditches were

generally lower (0.003 or less) than ratios in agricultural groundwater. Rapid loss of N2O

to the atmosphere may account for the generally lower ratios in drainage ditch water.

The ratio of N2O-N to NO3-N in agricultural groundwater was generally between 0.003

and 0.06, with values between 0.007 and 0.02 common. Assuming that all NLEACH is in the

form of NO3, we recommend a default emission factor of 0.015 (EF5-g) for N2O from

NLEACH in groundwater and drainage ditches, with a range of 0.003 to 0.06. The amount

of N2O 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:

EQUATION 4

N2O emissions from groundwater and agricultural drainage water

=

NLEACH x EF5-g

where EF5–g = 0.015 kg N2O-N/kg NLEACH, assuming that all N2O produced in a

particular year is emitted during that year.

Rivers

Once NLEACH from groundwater and surface water enters rivers, additional N2O is

produced associated with nitrification and denitrification of NLEACH (Seitzinger and

Kroeze, in preparation). It is assumed that minimal denitrification occurs in groundwater

and therefore that all NLEACH enters rivers.

Nitrification: N2O can be produced during nitrification of NLEACH in rivers. While much of

the NLEACH 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

NLEACH entering rivers nitrifies on average 0.5-3 times during river transport. We

assume for our default methodology that all NLEACH entering rivers is nitrified once during

river transport. The N2O yield (moles N2O-N/mol of NO3-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 N2O are found at reduced

O2 concentrations (Goreau et al., 1980). While reduced oxygen levels occur in some

rivers, especially those with high nutrient inputs, we suggest an N2O 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
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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 NLEACH inputs to rivers. N2O associated with denitrification (Jorgensen et al.,

1984) is released from river sediments. The ratio of N2O:N2 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 N2O-N emission to denitrification (N2–N production) in rivers is suggested.

In summary, the emission factor for NLEACH in rivers due to nitrification and

denitrification [EF5-r] is thus equal to 0.005 x NLEACH [for nitrification] plus 0.005 x

(NLEACH/2) [for denitrification], or 0.0075 x NLEACH. Therefore, N2O-N produced from

NLEACH during river transport = NLEACH x (EF5-r), where EF5-r = 0.0075.

Estuaries

Rivers are the major conduit for nitrogen transport to the coastal ocean (via estuaries).

As discussed above, half of NLEACH is assumed to be removed by denitrification in rivers in

the form of N2 and N2O. The remaining 50 per cent of NLEACH is discharged by rivers to

estuaries. Nitrogen inputs to estuaries can undergo nitrification and denitrification, with

associated N2O 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 NLEACH are nitrified again in estuaries, and that the ratio of

N2O-N to NO3–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 NLEACH that is carried to

estuaries by rivers is denitrified, and the ratio of N2O-N to denitrification (N2-N) emitted

is 0.005, as discussed above for rivers. NLEACH 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 N2O can be produced. Nitrous oxide production associated

with this fraction of NLEACH is not accounted for in this methodology.
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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 NLEACH is

transported to estuaries by rivers, 2) half of the NLEACH in estuaries is nitrified again in

the estuary with a ratio of N2O-N to NO3-N of 0.005, and 3) half of the NLEACH in

estuaries is denitrified in the estuary with a N2O-N to denitrification (N2-N) ratio of

0.005. Therefore, N2O-N produced from NLEACH in estuaries = NLEACH x (EF5-e) where

EF5-e = 0.0025.

The combined emission factor [EF5] for N2O due to NLEACH in: 1) groundwater and

surface drainage (EF5-g = 0.015 kg N2O-N/kg NLEACH), 2) rivers (EF5-r = 0.0075 kg

N2O-N/kg NLEACH), and 3) coastal marine areas (EF5-e = 0.0025 kg N2O-N/kg NLEACH) is

0.025 (EF5). Therefore:

EQUATION 5

NLEACH = [NFERT + Nex] x FracLEACH and N2O(L) = NLEACH x EF5

where the default values are FracLEACH = 0.3 kg N/kg N input to soils and EF5 = 0.025 kg

N2O-N/kg NLEACH (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 N2O

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 (NSEWAGE) production can be estimated from FAO per capita protein

consumption data (Protein) and human population counts (NrPEOPLE), assuming that

nitrogen constitutes about 16 per cent by weight of protein (FracNPR, Table 4-23).

EQUATION 6

NSEWAGE = Protein x FracNPR x NrPEOPLE

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 N2O in groundwater under cultivated land

irrigated with sewage effluent have been reported (Ronen et al., 1988). A few studies

have documented N2O 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).
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Three studies have directly measured N2O emissions from operating wastewater

treatment facilities (Hemond and Duran, 1989; Czepiel et al., 1995; Velthof and Oenema,

1993). All studies reported low rates of N2O emission. For example, nitrous oxide

emissions from a secondary treatment wastewater facility in New Hampshire (USA) were

approximately 0.0006 kg N2O-N/kg sewage N, assuming 3.2 kg sewage nitrogen are

produced/person/yr (Czepiel et al., 1995). Velthof and Oenema (1993) found N2O 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 N2O losses were 0.00005 kg/kg nitrogen entering the

system. Additional N2O released to the atmosphere following discharge of

supersaturated effluent to the environment is also low (0.0007 kg N2O-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

N2O 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 N2O-N was formed per unit of sewage

nitrogen than in the field study of Czepiel et al. (1995).

For the Phase II methodology N2O associated with sewage treatment and land disposal is

assumed to be negligible. This is based on the low emission rates of N2O 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 N2O production from land

disposal of human sewage. This assumption should be reviewed in the future, as new data

become available.

Rivers and estuaries

N2O 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 EF6–r = 0.0075 kg N2O–N/kg NSEWAGE (rivers) and EF6–e = 0.0025 kg N2O–N/kg

NSEWAGE (estuaries). The sum of N2O emissions in rivers (0.0075 x NSEWAGE) and

estuaries (0.0025 x NSEWAGE) associated with nitrification and denitrification of NSEWAGE is

calculated as:

EQUATION 7

N2O(S) = NSEWAGE x EF6

where:

EF6 = 0.1 kg N2O–N/kg NSEWAGE (Table 4-23)
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.111

D. Formation of N2O in the atmosphere from NH3

Dentener and Crutzen (1994) proposed that oxidation of NH3 and subsequent reaction

of the intermediate NH2 radical with NO2 could lead to a production of 0.9 (+0.9+–0.4)

Tg N2O (0.6 Tg N/yr).

The most important reactions for N2O production are given by:

NH3 + OH → NH2 + H2O R1

NH2 + NO2 → N2O + H2O R2

NH2 + O3 → NH2O + O2 (and other products) R3

The homogeneous reaction of NH3 with OH radical (R1) 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 NH3 oxidised by OH occurs between 30o

 N and 30o

S. The chemistry of the amine radical NH2 is not known, reactions R2 and R3 having

uncertainties of a factor of 2 (DeMore et al.,1994). In addition, emissions and

concentrations of NH3 and NO2 in tropical regions are poorly quantified.

Dentener and Crutzen (1994) parameterized natural NH3 emissions from vegetation

using a highly uncertain NH3 canopy compensation point (the atmospheric concentration

above which plants assimilate and below which they emit NH3). Without considering this

compensation point, N2O production was reduced by 55 per cent. Other sources of

NH3 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 N2O production may be

associated with agricultural nitrogen, amounting to about 0.4 Tg N2O/yr. Due to the high

uncertainty of this estimate (ca. 100 per cent), we have not included this potentially

important source in our agricultural N2O emissions inventory. More measurements on

the co-occurrence of high NH3, NO2 and OH concentrations in the tropics are needed

to provide more insight in the photochemical production of N2O. Furthermore

laboratory experiments on the reaction rates, especially of reactions R2 and R3, would be

extremely valuable.

E. Food processing operations

Some food processing operations are sources of N2O. 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 N2O source and therefore, there is no methodology at

the present time (For future purposes, this source would be reported under Industrial

Processes).
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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 N2O emissions (kg N/yr):

EQUATION 8

N2Oindirect = N2O(G) + N2O(L) + N2O(S)

where:

N2O(G) = N2O produced from atmospheric deposition of NOx and NH3

(kg N/yr);

N2O(L) = N2O produced from nitrogen leaching and runoff (kg N/yr);

N2O(S) = N2O produced from human sewage (kg N/yr) to be reported in

the Waste Chapter.

A. Atmospheric deposition of NOx and NH3

Methodology:

EQUATION 9

N2O(G) = (NFERT x FracGASF + NEX x FracGASM) x EF4

where :

EF4 = emission factor for atmospheric deposition (kg N2O-N/kg NH3-N

and NOx–N emitted) (see Table 4-23);

FracGASF = fraction of synthetic fertiliser nitrogen applied to soils that

volatilises as NH3 and NOx (kg NH3-N and NOx–N/kg of N input)

(see Table 4-19);

FracGASM = fraction of livestock nitrogen excretion that volatilises as NH3 and

NOx (kg NH3-N and NOx–N/kg of N excreted) (see Table 4-19).

Input:

NFERT = 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).
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.113

B. Leaching and runoff

Methodology:

NLEACH = (NFERT + Nex) x FracLEACH

N2O(L) = NLEACH x EF5

where :

FracLEACH = fraction of nitrogen input to soils that is lost through leaching and

runoff (kg N/kg of nitrogen applied) (see Table 4-24);

EF5 = emission factor for leaching/runoff (kg N2O-N/kg N leaching/runoff)

(see Table 4-23);

NLEACH = N leaching in country (kg N/yr).

Input:

NFERT = see A.

Nex = see A.

C. Sewage treatment (see Waste Chapter, Section 6.4)

Methodology:

EQUATION 10

NSEWAGE = PROTEIN x NrPEOPLE x FracNPR

N2O(S) = NSEWAGE x EF6

where:

EF6 = emission factor for sewage treatment (kg N2O-N/kg sewage-N

produced) (see Table 4-23);

FracNPR = 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;

NrPEOPLE = number of people in country. Recommended source: FAO.
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4.114 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

Future Work

The revised methodology for N2O 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 N2O emissions from each country, whatever climate, soils and set of crops is

involved. To make significant improvement in inventory methodologies for N2O, 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 N2O 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 CO2 and N2O production can be more accurately defined. For example, the amount

of nitrogen leached from agricultural fields represents a very large component of the

global N2O 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 CO2 and N2O 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 NOx 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 CO2 and N2O emissions from

agriculture and to improve the soil sink capacity for CH4; and (6) investigating errors that

may arise as a result of aggregating field scale data to the national level.
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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.

TABLE A-1

EMISSION OF N2O FROM ANIMAL DUNG AND URINE DEPOSITED IN GRASSLAND :

THE AMOUNT OF N2O EMITTED IS EXPRESSED IN % OF THE AMOUNT OF N EXCRETED BY THE GRAZING ANIMAL.

Country Soil Type Treatment Period N2O

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)

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Appendix B

Data Underlying Nitrous Oxide Emissions from

Agricultural Soils

This appendix presents the data used to calculate the manure-N excretion and N2O

emission factors in Table B-1. N2O emissions from different Animal Waste Management

Systems in different regions of the world are in Table B-2.

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TABLE B-1

CALCULATION OF MANURE-N EXCRETION AND N O E 2 MISSION FACTORS FOR DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS. THESE ARE TO BE

REPORTED UNDER MANURE MANAGEMENT, 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 N O) 2

Number of

animals (x106)

Nitrogen

excretion

kg

(N/animal/yr)

Anaerobic

Lagoon

(EF3)

Liquid

Systems

(EF3)

Daily

Spread

(EF3)

Solid

Storage &

Drylot

(EF3)

Pasture

range

Paddock

(EF3)

Used

Fuel

 (EF3)

Other System

 (EF3)

Total N

Excreted

(Tg N)

North America Non-dairy Cattle 99.199 70 0.1 0.1 0.0 2.0 2.0 0.0 0.5 6.9

Dairy Cattle 16.521 100 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.7Poultry (E) 1486.266 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.9Sheep 11.336 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.2Swine 66.146 20 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.3Other animals (F) 6.067 25 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.2

Western Europe Non-dairy Cattle 56.618 70 0.1 0.1 0.0 2.0 2.0 0.0 0.5 4.0

Dairy Cattle 31.099 100 0.1 0.1 0.0 2.0 2.0 0.0 0.5 3.1Poultry (E) 880.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.5Sheep 93.856 20 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.9Swine 114.959 20 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.3Other animals (F) 31.578 25 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.8

Eastern Europe Non-dairy Cattle 101.447 50 0.1 0.1 0.0 2.0 2.0 0.0 0.5 5.1

Dairy Cattle 56.800 70 0.1 0.1 0.0 2.0 2.0 0.0 0.5 4.0Poultry (E) 1667.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.0Sheep 188.159 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 3.0Swine 152.757 20 0.1 0.1 0.0 2.0 2.0 0.0 0.5 3.1Other animals (F) 21.558 25 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.5
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TABLE B-1 (CONTINUED)

CALCULATION OF MANURE-N EXCRETION AND N2O EMISSION FACTORS FOR DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS. THESE ARE TO BE

REPORTED UNDER MANURE MANAGEMENT, 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 N O) 2

Number of

animals(x 106)

Nitrogen

excretion

kg

(N/animal/yr)

Anaerobic

Lagoon

(EF3)

Liquid

Systems

(EF3)

Daily

Spread

(EF3)

Solid

Storage &

Drylot

(EF3)

Pasture

range

Paddock

(EF3)

Used Fuel

(EF3)

Other

System

 (EF3)

Total N

Excreted.

(Tg N)

Oceania Non-dairy Cattle 27.610 60 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.7

Dairy Cattle 4.441 80 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.4Poultry (E) 71.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.0Sheep 228.982 20 0.1 0.1 0.0 2.0 2.0 0.0 0.5 4.6Swine 5.003 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.1Other animals (F) 2.579 25 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.1

Latin America Non-dairy Cattle 272.871 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 10.9

Dairy Cattle 37.560 70 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.6Poultry (E) 1259.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.8Sheep 117.312 12 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.4Swine 78.150 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.3Other animals (F) 71.699 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.9

Africa Non-dairy Cattle 133.198 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 5.3

Dairy Cattle 18.734 60 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.1Poultry (E) 646.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.4Sheep 179.171 12 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.2Swine 12.445 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.2Other animals (F) 162.194 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 6.5
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manua l 4. 121

TABLE B-1 (CONTINUED)

CALCULATION OF MANURE-N EXCRETION AND N2O EMISSION FACTORS FOR DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS. THESE ARE TO BE REPORTED

UNDER MANURE MANAGEMENT, 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 N O) 2

Number of

animals

 (x 106)

Nitrogen

excretion

kg

N/animal/yr

Anaerobic

Lagoon

(EF3)

Liquid

Systems

(EF3)

Daily Spread

(EF3)

Solid Storage

& Drylot

(EF3)

Pasture range

Paddock

(EF3)

Used Fuel

(EF3)

Other

System

(EF3)

Total N

Excreted

(Tg N)

Near East andMediterranean

Non-dairy Cattle 44.562 50 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.2

Dairy Cattle 17.174 70 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.2Poultry (E) 656.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.4Sheep 187.502 12 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.3Swine 0.174 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.0Other animals (F) 81.962 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 3.3

Asia and Far East Non-dairy Cattle 440.398 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 17.6

Dairy Cattle 45.240 60 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.7Poultry (E) 3949.000 0.6 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.4Sheep 202.442 12 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.4Swine 403.231 16 0.1 0.1 0.0 2.0 2.0 0.0 0.5 6.5Other animals (F) 293.700 40 0.1 0.1 0.0 2.0 2.0 0.0 0.5 11.7

World Total 135.3(D) Includes buffalo(E) Includes chickens, turkeys and ducks(F) Includes goats, horses, mules, donkeys and camels
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TABLE B-2

N O E 2 MISSIONS FROM DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS

Region Type of Animal N2O Emission from Waste Management Systems (GgN)

Liquid

System

Daily

 Spread

Solid Storage

and Drylot

Pasture Range

and Paddock

Used Fuel Other System Total AWMS Total N O2

Emission (Gg N)

North America Non-dairy Cattle 0 0 19 117 0 0 137 137

Dairy Cattle 0 000019 9Poultry (E) 0 000044 4Sheep 0 003003 3Swine 0 050006 6Other animals (F) 0 003003 3

Western Europe Non-dairy Cattle 0 0 2 26 0 2 32 32

Dairy Cattle 0 0 13 5 0 0 20 20Poultry (E) 0 000023 3Sheep 0 0 1 33 0 1 34 34Swine 0 0 11 0 0 0 12 12Other animals (F) 0 0 0 15 0 0 15 15

Eastern Europe Non-dairy Cattle 0 0 53 0 0 0 55 55

Dairy Cattle 0 0 53 10 0 0 64 64Poultry (E) 0 000044 4Sheep 0 0 0 44 0 4 48 48Swine 0 0 0 16 0 7 24 24Other animals (F) 0 0 0 10 0 0 10 10
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manua l 4. 123

TABLE B-2 (CONTINUED)

N O E 2 MISSIONS FROM DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS

Region Type of Animal N2O Emission from Waste Management Systems (GgN)

Liquid

System

Daily

 Spread

Solid Storage

and Drylot

Pasture Range

and Paddock

Used Fuel Other System Total AWMS Total N O2

Emission (GgN)

Oceania Non-dairy Cattle 0 0 0 33 0 0 33 33

Dairy Cattle 0 0 0 7 0 0 7 7Poultry (E) 0 0 0 0 0 0 0 0Sheep 0 0 0 92 0 0 92 92Swine 0 0 0 0 0 0 0 0Other animals (F) 0 0 0 1 0 0 1 1

Latin America Non-dairy Cattle 0 0 0 216 0 1 217 217

Dairy Cattle 0 0 1 19 0 0 19 19Poultry (E) 0 0 0 6 0 2 8 8Sheep 0 0 0 28 0 0 28 28Swine 0 0 13 0 0 3 15 15Other animals (F) 0 0 0 57 0 0 57 57

Africa Non-dairy Cattle 0 0 3 102 0 0 105 105

Dairy Cattle 0 0 0 19 0 0 19 19Poultry (E) 0 0 0 6 0 0 7 7Sheep 0 0 0 43 0 0 43 43Swine 0 0 4 0 0 0 4 4Other animals (F) 0 0 0 128 0 0 129 129
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4.124 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE B-2 (CONTINUED)

N O E 2 MISSIONS FROM DIFFERENT ANIMAL WASTE MANAGEMENT SYSTEMS IN DIFFERENT WORLD REGIONS

Region Type of Animal N O Emission from Waste Management Systems (Gg N) 2

Anaerobi

c

Lagoon

Liquid

System

Daily

 Spread

Solid Storage

and Drylot

Pasture Range

and Paddock

Used Fuel Other

System

Total AWMS Total N O2

Emission (Gg N)

Near East and

Mediterranean

Non-dairy Cattle 0 0 0 0 34 0 0 35 35

Dairy Cattle 0 0 0 1 19 0 0 19 19Poultry (E) 0 0 0 0 6 0 1 6 6Sheep 0 0 0 0 45 0 0 45 45Swine 0 0 0 0 0 0 0 0 0Other animals (F) 0 0 0 0 66 0 0 66 66

Asia and FarEast

Non-dairy Cattle 0 0 0 49 102 0 0 151 151Dairy Cattle 0 0 0 0 13 0 0 13 13Poultry (E) 0 0 0 0 21 0 6 27 27Sheep 0 0 0 0 40 0 2 42 42Swine 0 0 0 68 0 0 0 71 71Other animals (F) 0 0 0 0 223 0 3 226 226

World Total 1609 1971(D) Includes buffalo(E) Includes chickens, turkeys and ducks(F) Includes goats, horses, mules, donkeys and camels
4 AGRICULTURE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 4.125

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Mosier, A.R., D.S. Schimel, D. Valentine, K.F. Bronson and W.J. Parton (1991), “Methane

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Mosier, A.R., J.M. Duxbury, J.R. Freney, O. Heinemeyer and K. Minami. (1995a), “Nitrous

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M.Sc. Thesis. Faculty of Agricultural and Applied Biological Sciences. University

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Mannetje and J. Frame (eds.) pp. 458-462.

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

C HAPTER 5

L AND - U SE C HANGE &

F ORESTRY

5 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.1

5. LAND-USE CHANGE & FORESTRY

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 (CO2), and much of the methodology discussion in this

chapter is specific to CO2. Other important direct GHGs, including methane (CH4) and

nitrous oxide (N2O), and indirect GHGs,1 including carbon monoxide (CO), oxides of

nitrogen (NOx, i.e., NO and NO2), 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-CO2 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 CO2 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 CO2 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 CO2 (CO2-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 CO2-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, CO2 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 CO2 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.
LAND-USE CHANGE & FORESTRY

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 CO2 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-CO2 trace gases (CH4, CO, N2O, and NOx) due to biomass burning

are generally produced immediately and are considered as net emissions. NMVOC are

not treated here. Gross emissions of CO2 due to reductions in forest area may or may

not be balanced by uptake of CO2 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 CO2 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 CO2 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 CO2

passes into vegetation each year (in the order of 100 Pg CO2-C per year), and in the

absence of significant human disturbance, this large flux of CO2 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

CO2 and decreases for a while the photosynthetic flux. Burning is, after all, simply a rapid

form of oxidation or decay. Subsequently, the CO2 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 CO2 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-CO2 trace gases are an important research issue. These

releases may be important , but are currently too uncertain to be included in calculations.
5 LAND-USE CHANGE & FORESTRY

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 CO2 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 CO2 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 CO2 flux from the wood products that decay rapidly, plus the increased

respiration flux of CO2 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 CO2 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 CO2

fluxes associated with that specific landuse, is one feature of CO2 emissions analysis that

distinguishes landuse from fossil fuel consumption. Consequently, when one considers

the issue of CO2 flux associated with landuse today or in any base year, one must

consider past land-use activities and their effects upon current fluxes of CO2. 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

CO2 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 CO2

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 CO2 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 CO2 flux. Finally, the assumptions regarding

the response of vegetation and soils to different land uses and land-use change can be
LAND-USE CHANGE & FORESTRY

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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.5

BOX 1

ILLUSTRATIVE CALCULATIONS OF CARBON FLUXES

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 CO2 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 CO2. 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 CO2.
LAND-USE CHANGE & FORESTRY

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 can

be addressed first. Complexities and subtleties of the relationship of forestry and landuse change to fluxes of CO2 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 CO2 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 CO2 flux,4 as well

as 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 CO2 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-CO2 trace gases (CH4, CO,

N2O and NOx) from the open burning of biomass from forest clearing.

 

 4 Similarly, current land-use changes will affect future fluxes of CO2.

 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-CO2 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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.7

BOX 2

FOREST AND GRASSLAND CATEGORIES

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

TABLE 5-1

TYPES OF TROPICAL FORESTS AND REGIONAL FOREST FORMATIONS

Types of tropical forestsa

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

evergreen

to semiever-green

forests

Dry

deciduous

forests and

miombo

woodlands

Deciduous

forests and

woodlands.

Very dry

savanna and

steppe

Montane

evergreen

forests

Scrub forests

and evergreen

to 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 or

pseudosteppic

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 LAND-USE CHANGE & FORESTRY

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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 CO2 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-CO2 trace gases such as CH4

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-CO2 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 CO2 emissions or

removals from changes in forest and other woody biomass stocks.
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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-CO2 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-CO2 Trace

Gases from

Open Burning

CH4, CO, N2O and

NOX Emissions

CO2 Emissions

Abandonment of Managed Lands

 CO2 Emissions and

Removals

 CO2 Removals

Changes in Forest and Other

Land-Use Change and Management

CO2 Emissions and Uptake by Soils from

Woody Biomass Stocks

Emissions and Removals from Soils (20 yrs)

Annual Growth Increment

Non-CO2 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 CO2

Emissions and

Removals

 CH4, CO, N2O

and NOX

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 LAND-USE CHANGE & FORESTRY

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 CO2 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 CO2

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 CO2 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 CO2 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).
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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 LAND-USE CHANGE & FORESTRY

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BOX 3

ALTERNATIVE LEVELS OF DETAIL

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.
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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 woody

biomass 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 plantations10

• 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., CO2 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 LAND-USE CHANGE & FORESTRY

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.
LAND-USE CHANGE & FORESTRY

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.

BOX 4

ADAPTING DETAILED FOREST INVENTORY DATA TO THE IPCC FORMAT

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 CO2 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 LAND-USE CHANGE & FORESTRY

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 CO2. 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.

BOX 5

THE FATE OF HARVESTED WOOD

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 CO2 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
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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 CO2

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

TABLE 5-2

ANNUAL AVERAGE ABOVEGROUND BIOMASS UPTAKE BY NATURAL REGENERATION

(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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.21

TABLE 5-3

AVERAGE ANNUAL ACCUMULATION OF DRY MATTER AS BIOMASS IN

PLANTATIONS

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 (m3) 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/m3 for deciduous

trees and 0.45 t dm/m3 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
LAND-USE CHANGE & FORESTRY

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

BOX 6

VARIABILITY IN DENSITIES OF TREE SPECIES

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/cm3. 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 CO2 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-CO2 gases should also be

calculated.
5 LAND-USE CHANGE & FORESTRY

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 CO2 (using the ratio 44/12). A

positive value for CO2 in stocks is a CO2 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

CO2 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 CO2 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 CO2 and CH4.

17 However, the CH4 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

CO2. 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 CO2 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.
LAND-USE CHANGE & FORESTRY

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 CO2 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 CO2, 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 CO2 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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.25

BOX 7

ABOVEGROUND BIOMASS IN GRASSLANDS

Conversion of a grassland to cultivated land may result in net CO2

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 and

pasture. 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

Year19 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.
LAND-USE CHANGE & FORESTRY

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.

TABLE 5-4

AVERAGE ABOVEGROUND BIOMASS ESTIMATES

FOR TROPICAL FORESTS BY CLIMATIC ZONE

(TONNES DM/HA)

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 60-90a 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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.27

TABLE 5-5

ABOVEGROUND BIOMASS ESTIMATES FOR VARIOUS

TROPICAL FOREST TYPES BY COUNTRY

(TONNES DM/HA)

Country Forest Type Climatic Zone Aboveground

Biomass

Africa

Benin Closed forest

Tree savanna

Dry

Dry

175

96

Botswanaa 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

Zambiaa Woodland-miombo

Woodland-miombo

Moist-long dry season

Dry-long dry season

91

81

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

TABLE 5-5 (CONT.)

ABOVEGROUND BIOMASS ESTIMATES FOR VARIOUS

TROPICAL FOREST TYPES BY COUNTRY

(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 LAND-USE CHANGE & FORESTRY

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 5.29

TABLE 5-5 (CONT.)

ABOVEGROUND BIOMASS ESTIMATES FOR VARIOUS

TROPICAL FOREST TYPES BY COUNTRY

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

TABLE 5-6

DRY MATTER IN ABOVEGROUND BIOMASS IN TEMPERATE AND BOREAL FORESTS

(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 CO2 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 CO2 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 LAND-USE CHANGE & FORESTRY

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-CO2 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 CH4 as though it were carbon dioxide. Later in this chapter, these

emissions of CO and CH4 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.
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5.32 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

EQUATION 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 CO2 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-CO2 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 (CH4), carbon monoxide (CO),

nitrous oxide (N2O), and oxides of nitrogen (NOx, i.e., NO and NO2). The approach is

essentially the same as that used for non-CO2 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 (CH4 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 N2O and NOx

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. CO2, N2O, and NOx are mainly emitted in the flaming stage, while CH4

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 LAND-USE CHANGE & FORESTRY

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-CO2 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-CO2 trace gases. To complete the calculations, it is

necessary only to add step 2 of the calculation – the release of non-CO2 trace gases from

current burning.

TABLE 5-7

EMISSION RATIOS FOR OPEN BURNING OF CLEARED FORESTS

Compound Ratios

CH4

CO

N2O

NOx

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., CH4 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 CH4, CO, N2O, and NOx can be calculated (Crutzen and

Andreae, 1990). The total carbon released due to burning is multiplied by the emission

ratios of CH4 and CO relative to emissions of total carbon to yield total emissions of

CH4 and CO (each expressed in units of C). The emissions of CH4 and CO are

multiplied by 16/12 and 28/12, respectively, to convert to full molecular weights.

To calculate emissions of N2O and NOx, 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 N2O and

NOx relative to the total N released from the fuel to yield emissions of N2O and NOx

(expressed in units of N). To convert to full molecular weights, the emissions of N2O

and NOx are multiplied by 44/28 and 46/14, respectively.26

The trace gas emissions from burning calculation are summarised as follows:

• CH4 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 N2O the ratio is 44/28 and for NOx it is

46/14. NO2 has been used as the reference molecule for NOx.
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5.34 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

• CO Emissions = (carbon released) x (emission ratio) x 28/12

• N2O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28

• NOx 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 CO2 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 CO2 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.
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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 pasture28. 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 CO2 Emissions and Uptake by Soils from

Land-Use Change and Management

5.3.1 Overview

The principal sources/sinks of CO2 in soils are associated with changes in the amount of

organic carbon stored in soils. Release of CO2 also occurs from inorganic sources, either

from naturally occurring carbonate minerals or from applied lime. CO2 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 CO2 due to changes in

soil organic carbon stocks. CO2 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 CO2 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.
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5.36 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

Estimates of CO2 fluxes can be made in two ways: (1) by direct measurement of CO2

flux, and (2) indirectly, through balance estimates of the net change in carbon stocks of

the soil.

Direct estimates of CO2 influx, through photosynthesis, and CO2 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 CO2 are large relative to their

difference. The most practical means of directly measuring net CO2 fluxes for whole

ecosystems is by using micrometeorological techniques, which are costly and timeconsuming. Such measurements for agricultural ecosystems are scarce.

Balance estimates of CO2 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 CO2 can be associated with
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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.
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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:

TABLE 5-8

SOIL TYPE CLASSIFICATIONS

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.
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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 CO2

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 forest

clearance, 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
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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.
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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. An

analysis 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 CO2 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);
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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 CO2 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).
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TABLE 5-9

EXAMPLES OF MAJOR LAND-USE/LAND MANAGEMENT SYSTEMS WITHIN

THE MAJOR CLIMATE DIVISIONS

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
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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 CO2 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 CO2 from cultivated organic

soils (i.e., Histosols) and 3) emissions of CO2 from liming of agricultural soils.

5.3.8 Changes in Mineral Soil Carbon Stocks

Inventory calculation period

Net 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 CO2 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 LAND-USE CHANGE & FORESTRY

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 CO2-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 CO2-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.
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5.46 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 5-10

EXAMPLE OF CALCULATIONS FOR NET CHANGE IN CARBON STORAGE IN MINERAL SOILS FOR A

COLD TEMPERATE DRY REGION COUNTRY -

FOR SIMPLICITY ONLY FOUR MANAGEMENT SYSTEMS ARE INCLUDED

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 first

approximation 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.
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TABLE 5-11

APPROXIMATE QUANTITIES OF SOIL ORGANIC CARBON

UNDER NATIVE VEGETATION

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

TABLE 5-12a

COEFFICIENTS USED IN DEFAULT CALCULATION PROCEDURES FOR ESTIMATING CARBON STOCKS IN MINERAL SOILS

System SGb BFc Tillage Factord Input Factorse

NotillageReduced

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).
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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

CO2 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 CO2 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

CO2 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 CaCO3 and dolomite CaMg(CO3)2.

When added to acid soil these compounds release CO2 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
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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 CO2, are calculated from i) net changes in carbon storage in

mineral soil, ii) CO2-C emissions from organic soils and iii) CO2-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 CO2 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

CHANGES IN FOREST AND OTHER WOODY BIOMASS STOCKS

Prescribed Burning of Forests: Non-CO2 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 North

America and Australia (Seiler and Crutzen, 1980). Because carbon is allowed to reaccumulate on the land after burning, no net CO2 emissions occur over time, although

emissions of CH4, CO, N2O, and NOx 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 CO2 sink, but at the same time adding other radiatively important non-CO2
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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-CO2

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-CO2 trace

gases from biomass burning.

b. Non-CO2 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-CO2 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-CO2

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 N2O and NOx from the soils for up to 6 months
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following the burn; however, in other studies measurements of N2O 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-CO2 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 N2O flux to the atmosphere via dissolution of N2O in

the soil water, transport to surface waters, and degassing from solution (Bowden and

Bormann, 1986). An experiment in Brazil found that N2O 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 N2O 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 CH4

which, in effect, adds to the atmospheric burden of CH4. Specifically, the loss of forest

area (tropical or temperate) may also result in increased net CH4 emissions to the

atmosphere. Soils are a natural sink of CH4 (i.e., soils absorb atmospheric CH4), 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 CO2 but CH4, N2O, 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 CH4 uptake by the soils (Mosier et al., 1991).

It is not clear what the effect on N2O 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 N2O 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 CH4 and CO2 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 CO2 and 0.2 per cent is released as CH4. Fearnside suggests that forest

clearing results in increased termite populations and thereby enhances natural termite

CH4 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 CH4. Because of the uncertainty of the effect of clearing on

termite populations and associated CH4 release, no guidance on calculation of this

component is included in the methodology.
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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 CO2 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 CO2 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 CH4 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.
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BOX 8

BELOWGROUND BIOMASS

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 left

aboveground 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 CO2 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 CO2 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.
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population pressure has reduced the lengths of fallow periods so that currently much of

the fallow land recovers very little and higher net CO2 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 biomass30 to carbon (multiply by 0.50)

and assume 90 per cent of this material is released as CO2 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

CO2 associated with shifting cultivation. For the biomass burned in shifting cultivation,

non-CO2 gases (N2O, CH4, NOx, 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 CH4 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 CH4 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 CH4 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 CO2 and CH4 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).
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seasonally, as well as daily. Net emissions of N2O and CO also may be affected by this

activity, although these fluxes are not well determined.

A straightforward CH4 flux calculation can be based on the area of land flooded, due to

hydroelectric production or other human-made causes, an average daily CH4 emission

coefficient, and the number of days in the year that the area is flooded. Since

measurements of CH4 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 CH4 emission rates for natural

wetlands, derived from measured emission rates in field experiments, and average CH4

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.

TABLE 5-13

AVERAGE METHANE EMISSIONS AND PRODUCTION PERIODS OF NATURAL WETLANDS

Wetland Categories

(mg CH4/m2.day)

Emission Rate

(mg CH4-C/m2.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 CH4, estimated to release 100-200 Tg

CH4/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 CH4 emissions, and an increase in CO2 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 CH4,

drainage and drying of a wetland could eventually result in the wetland area changing from

a source to a sink of CH4 (e.g., Harriss et al., 1982).
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Loss of wetland area could also affect net N2O and CO fluxes, although both the

direction and magnitude of the effect is highly uncertain. Natural dryland soils are a

source of N2O, believed to emit 9-28 Tg N2O/yr (3-9 Tg N2O-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 CH4 emissions due to wetland drainage, the area drained is

multiplied by the difference in the average daily CH4 emission rate before and after

draining, and is multiplied by the number of days in a year that the wetland was emitting

CH4 prior to drainage. The number of days of CH4 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 CH4 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 CH4

calculations associated with land flooding in early refinements of the calculations, but the

N2O 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.

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T5 Technical Appendix: Deforestation

Data

Data on rates of deforestation32 are essential for calculating the fluxes of CO2 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.
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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).

LAND COVER CLASSES

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).
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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,
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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.
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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 designed33). 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.
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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 CO2 and other trace gases are available.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

C HAPTER 6

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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 6.1

6. WASTE

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 (CH4).

Approximately 5-20 per cent (IPCC, 1992) of annual global anthropogenic CH4 produced

and released into the atmosphere is a by-product of the anaerobic decomposition of

waste. Two major sources of this type of CH4 production are solid waste disposal to

land and wastewater treatment. In each case, methanogenic bacteria break down organic

matter in the waste to produce CH4.

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 CH4 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 CH4, solid waste disposal sites can also produce substantial amounts of

CO2 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 CO2 released from waste. Hence, these CO2

emissions are not treated as net emissions from waste in the IPCC Methodology. If

biomass raw materials are not being sustainably produced, the net CO2 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 CH4 (CORINAIR,

1994). These emissions are not currently addressed in the Revised Guidelines.

Wastewater treatment is also a source of N2O, and a methodology for estimating N2O

emissions is included in this Chapter for human sewage. (Chapter 4 of these Revised

Guidelines addresses N2O emissions from agriculture, using a life-cycle emissions

approach.)

Waste incineration, like all combustion, can produce CO2, CH4, CO, NOx, N2O 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 CH4 and N2O it is only possible to report

preliminary estimates and research results at this time. Further studies are needed to
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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 CH4 and N2O 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 CH4, 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 CH4 in global atmospheric

change. Methane from SWDSs contributes a significant proportion of annual global CH4

emissions, although the estimation is subject to a great deal of uncertainty. Estimates of

global CH4 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 CH4 produced. It will then describe two

methodologies for estimating CH4 emissions from SWDSs. One of these methods is a

default base method which all countries can use to estimate CH4 emissions from different
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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 CH4 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 CH4 and CO2 (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, CO2, and a range of carboxylic acids. These acids are then converted to acetic

acid which, together with hydrogen and CO2, forms the major substrate for growth of

methanogenic bacteria.

Landfill gas consists of approximately 50 per cent CO2 and 50 per cent CH4 by volume.

However, the percentage of CO2 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 CO2 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

CH4 emissions. Nevertheless, a better understanding of the factors thought to most

significantly influence the generation of CH4 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 CH4

generation.

Waste disposal practices

Waste disposal practices of concern for CH4 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 CH4 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 CH4 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
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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 25-40o

C. These

temperatures can be maintained within the SWDS regardless of the ambient surface

temperatures. Outside of these temperatures, CH4 production is reduced. Optimal pH

for CH4 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 CH4 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 CH4 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 CH4 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 CH4 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 CH4 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 CH4 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 to

the waste generated within each of these regions. It is the most widely accessible, easyto-apply methodology for calculating country-specific emissions of CH4 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:
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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 CH4 generation rather than

emission, and that oxidation often occurs in the upper layers of the waste mass and in

site cover material, a CH4 oxidation factor (OX) is included in the equation (currently

equal to 0, pending the availability of further data).

The determination of annual CH4 emissions for each country or region can be calculated

from Equation 1:

EQUATION 1

Methane emissions (Gg/yr)

=

(MSWT x MSWF x MCF x DOC x DOCF x F x 16/12 - R) x (1-OX)

where:

MSWT = total MSW generated (Gg/yr)

MSWF = fraction of MSW disposed to solid waste disposal sites

MCF = methane correction factor (fraction)

DOC = degradable organic carbon (fraction)

DOCF = fraction DOC dissimilated

F = fraction of CH4 in landfill gas (default is 0.5)

R = recovered CH4 (Gg/yr)

OX = oxidation factor (fraction - default is 0)

Total MSW (MSWT) 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 CH4 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
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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.

TABLE 6-1

COUNTRY WASTE GENERATION, COMPOSITION, AND DISPOSAL DATA

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

USAa 2.0 0.62 1.24

Canadab 1.81 0.75 1.35

Oceania

Australiac 1.26 1.00 0.15 1.26

New Zealandl 1.33 1.0 0.19 1.33

UK/Western

Europe/Scandinavia

0.08-0.19

UKm 1.9 0.9 0.10 1.7

Irelandb 0.85 1.00 0.85

Austriad 0.92 0.40 0.36

Belgiumb 1.10 0.43 0.47

Denmarkb 1.26 0.20 0.25

Finlandb 1.70 0.77 1.3

Franceb 1.29 0.46 0.60

Germanyb 0.99 0.66 0.65

Greeceb 0.85 0.93 0.79

Italye 0.94 0.88 0.83

Luxembourgb 1.34 0.35 0.47

Netherlandsf 1.58 0.67 0.14 1.06

Norwayb 1.40 0.75 1.05

Portugalb 0.90 0.86 0.78

Spainb 0.99 0.85 0.83

Swedenb 1.01 0.44 0.44

Switzerlandb 1.10 0.23 0.25

Eastern Europe

Polandg 0.15 0.54

Russiah 0.93 0.94 0.17 0.87
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 6.7

TABLE 6-1 (CONTINUED)

COUNTRY WASTE GENERATION, COMPOSITION, AND DISPOSAL DATA

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

Japanb 1.12 0.38 0.43

Indiai 0.33 0.6 0.18 0.2

Chinaj 0.09 0.84

Indonesiaj 0.17 0.51

Central America

Guatemalaj 0.13 0.46

South America

Brazilj 0.12 1.47

Peruj 0.15 0.98

Chilej 0.18 0.59

Africa

Egyptj 0.21 0.40

Nigeriaj 0.11 0.40

South Africak 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 (MSWF) and Methane

Correction Factor (MCF) reflect the way in which MSW is managed and the effect of

management practices on CH4 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).
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6.8 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 6-2

SWDS CLASSIFICATION AND METHANE CORRECTION FACTORS

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 CH4 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.
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 6.9

TABLE 6-3

DEFAULT DOC VALUES FOR MAJOR WASTE STREAMS

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 wastea 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.

EQUATION 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 (DOCF) 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 35o

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 CH4 (R) is the amount of CH4 that is captured for flaring or use. No default

values are provided for the quantity of CH4 recovered, as this value is country-specific.

See Section 6.2.6 below for more information.

Oxidation Factor (OX) accounts for the CH4 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 CH4 generation, it is important to recognise the

oxidation may reduce the quantity of CH4 generated that is ultimately emitted. A number

of researchers are investigating and quantifying the effects of CH4 oxidation in waste

disposal sites. However, as yet there is no internationally accepted factor that can be

applied to account for CH4 oxidation. The CH4 oxidation factor in the equation has

therefore been set equal to 0, pending the availability of new data. A better
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6.10 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

understanding of the factors influencing CH4 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

CH4 recovered, as this CH4 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 CH4 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 CH4 emissions from SWDSs acknowledge the fact

that CH4 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 CH4 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 CH4 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.

EQUATION 3

Q = LO R (e-kc - e -kt)

where:

Q = methane generated in current year (m3/yr)

L0 = methane generation potential (m3/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 (Lo). The methane generation potential depends upon the

composition of the waste. Values for Lo can vary widely, and are difficult to estimate

accurately for a particular SWDS or set of SWDSs. Lo values may range from less than

100 to over 200 m3/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
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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 CH4 generation from waste landfilled in a single year

(Rx). 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:

EQUATION 4

QT,x = k Rx LO e-k(T-x)

where:

QT,x = the amount of methane generated in the current year (T) by the

waste Rx

x = the year of waste input

Rx = 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 Rx and the results summed (see Equation 5).

EQUATION 5

QT = ΣQT,x

 for x = initial year to T

6.2.5 Sources of Uncertainty

There are two areas of uncertainty in the estimate of CH4 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 CH4 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
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6.12 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

default method will overestimate CH4 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 CH4 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 CH4 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 CH4 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 CH4 that is actually generated from the waste in the SWDS;

• The quantity of CH4 that is actually emitted to the atmosphere.

Waste quantity and composition: The quality of CH4 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 available

will prevent extensive investigations of old and smaller sites. It is therefore more costeffective to concentrate efforts on improving the quality of data being collected on

existing 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 CH4 generated, and small variations in the

assumed values for DOC can result in large variations in the overall estimate of CH4

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 CH4 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 CH4 emissions levels.

Quantity of methane generated that is emitted to the atmosphere: The main uncertainty

influencing the quantity of CH4 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 CH4 ultimately emitted from a site.
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6.2.6 Flaring and Gas Recovery Schemes

Flaring and gas recovery schemes successfully reduce CH4 emissions from SWDSs. Any

national inventory of CH4 emissions from SWDSs must therefore take into account the

reductions achieved by these practices.

For sites recovering CH4 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 CH4 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 CH4 generation

potential of the waste; ii) the rate at which CH4 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 CH4 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 CH4 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 CH4 is recovered and utilised.

This section provides the default methodology for estimating CH4 emissions from WWH.
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6.3.2 Background

Handling of wastewater and its residual solids by-product (sludge) under anaerobic

conditions results in CH4 production. The extent of CH4 production depends primarily

on the following factors:

A) Wastewater Characteristics

The principal factor in determining the CH4 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 CH4

than wastewater with lower COD (or BOD) concentrations.

B) Handling Systems

Handling systems vary in the environment that they provide for CH4 production. Systems

that provide anaerobic environments will generally produce CH4 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 CH4

production. Shallow lagoons, less than 1 metre in depth, generally provide aerobic

conditions and little CH4 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 CH4 production increases. This is especially

important in uncontrolled systems and in warm climates. CH4 production typically

requires a temperature higher than 15°C. Fermentation and thus CH4 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 CH4 will be

produced only in instances where sedimentation and extended sludge retention occur.

Other factors that influence CH4 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

test1, denoted as BOD5. 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 BOD7, is used in some countries instead of BOD5.

The conversion between BOD5 and BOD7 is dependent on the characteristics of the

wastewater. Experts within individual countries should be consulted to obtain

appropriate conversion coefficients.
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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 treatment

consists 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 CH4.

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 BOD7 (or other) values rather than BOD5 values. In this case, domestic

wastewater experts should be consulted to convert the available BOD data into the

BOD5 form.
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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 CH4 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 CH4 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.
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TABLE 6-4

METHODS OF WASTEWATER HANDLING

Handling Method Exceptions to Expected CH4 Production

Mostly aerobic disposal and handling

methods (little or no CH4 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 CH4 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 CH4 emissions from wastewater handling

requires three basic steps:
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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 CH4 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 m3 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

CH4 per kg DC. The emissions factors depend on the fraction of wastewater managed

by each wastewater handling method, maximum CH4 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 CH4 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 (TOWdom) calculation.

EQUATION 6

TOWdom = P x Ddom x (1 - DSdom)
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Equation 7 presents the total domestic organic sludge (TOSdom) calculation.

EQUATION 7

TOSdom = P x Ddom x DSdom

where:

TOWdom = total domestic/commercial organic wastewater in kg BOD/yr

TOSdom = total domestic/commercial organic sludge in kg BOD/yr

P = population in 1000 persons

Ddom = domestic/commercial degradable organic component in

kg BOD/1000 persons/yr

DSdom = fraction of domestic/commercial degradable organic component

removed as sludge

Industrial

Data needed are:

1. Degradable organic component (DC) indicator in kg DC per m3 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 m3/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 (TOWind) calculation for a particular

industry.

EQUATION 8

TOWind (kg COD/yr) = W x O x Dind x (1 - DSind)
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6.20 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

Equation 9 presents the total organic sludge (TOSind) calculation for a particular industry.

EQUATION 9

TOSind (kg COD/yr) = W x O x Dind x DSind

where:

TOWind = total industrial organic wastewater in kg COD/yr

TOSind = total industrial organic sludge in kg COD/yr

W = wastewater consumed in m3/tonne of product

O = total output by selected industry in tonnes/yr

Dind = industrial degradable organic component in kg COD/m3

wastewater

DSind = 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 (Bo) of the wastewater type.

• Maximum methane producing capacity (Bo): The methane producing potential, Bo, is the

maximum amount of CH4 that can be produced from a given quantity of wastewater

or sludge. The CH4 producing potential varies by the composition of the

wastewater/sludge and its degradability. The default (theoretical) value for Bo is 0.25

kg CH4/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 of

sludge 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

CH4 conversion factor. The MCF defines the portion of CH4 producing potential (Bo)

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 Bo is expressed in units of kg CH4/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 CH4 producing potential from BOD or COD, the maximum potential CH4

produced per unit of BOD is equivalent to the maximum potential CH4 produced per

unit of COD. This value is 0.25 kg CH4/kg COD.
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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 CH4

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:

EQUATION 10

EFi = Boi x ∑ (WSix x MCFx )

where:

EFi = emission factor (kg CH4 /kg DC) for wastewater type (e.g., fertiliser

industry, domestic, etc.)

Boi = maximum methane producing capacity (kg CH4/kg DC) for

wastewater type i

WSix = fraction of wastewater type i treated using wastewater handling

system x

MCFx = methane conversion factors of each wastewater system x

Equation 11 presents the emission factor calculation for sludge:

EQUATION 11

EFj = Boj x ∑(SSjy x MCFy)

where:

EFj = emission factor (kg CH4 /kg DC) for sludge type j (e.g., fertiliser

industry wastewater, domestic wastewater, etc.)

Boj = maximum methane producing capacity (kg CH4/kg DC) for sludge type 

j

SSjy = fraction of sludge type j treated using sludge handling system y

MCFy = 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.
WASTE

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

CH4, 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 CH4 emissions from

wastewater. In equation form, the estimate of total CH4 emissions from wastewater

handling is as follows:

EQUATION 12

WM = Σi (TOWi x EFi - MRi)

where:

WM = total methane emissions from wastewater in kg CH4

TOWi = 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)

EFi = emission factor for wastewater type i in kg CH4/kg DC (Step 2)

MRi = total amount of methane recovered or flared from wastewater type i

in kg CH4. 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 CH4, 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 CH4 emissions from

wastewater. In equation form, the estimate of total CH4 emissions from sludge handling is

as follows:

EQUATION 13

SM = ∑j (TOSj x EFj - MRj)

where:

SM = total methane emissions from sludge in kg CH4

TOSj = 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)

EFj = emission factor for sludge type j in kg CH4/kg DC (Step 2)

MRj = total amount of methane recovered or flared from sludge type j in kg

CH4. If no data are available, the default is zero
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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:

EQUATION 14

TM = WM + SM

where:

TM = total methane from wastewater and sludge handling in kg CH4

WM = total methane emissions from wastewater in kg CH4

SM = total methane emissions from sludge in kg CH4

6.3.6 Uncertainties

The quality of CH4 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.

TABLE 6-5

ESTIMATED BOD5 VALUES IN DOMESTIC WASTEWATER BY REGION

Region BOD5 Value

 (kg/cap/day)

BOD5 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)
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6.24 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual

TABLE 6-6

INDUSTRIAL WASTEWATER DATA BY REGION

Industry Type and Region Wastewater

Produced

(m3/tonnes of

product)

COD Value

(kg COD/m3

wastewater)

Country

Beverage - Distilled & Industry

Generic - ethanol 13 m3/ m3 ethanol 40

Generic - ethanol NAV 5,000 kg/ m3 ethanol

South America NAV 22 Brazil

Western Europe NAV 4.0 - 5.0 Netherlands

Beverage - Malt & Beer

Generic 5 m3/ m3 beer 17

Generic 5-9 m3/ m3 beer 2.0 - 7.0

Western Europe NAV 1.0 - 1.5 Netherlands

Food - Meat & Poultry

Generic 1.4 m3/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
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Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 6.25

TABLE 6-6 (CONTINUED)

INDUSTRIAL WASTEWATER DATA BY REGION

Industry Type and Region Wastewater Produced

(m3/tonnes of

product)

COD Value

(kg COD/m3

 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.

TABLE 6-7

DOMESTIC WASTEWATER TREATMENT EMISSIONS FACTOR DERIVATION DATA

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

TABLE 6-8

INDUSTRIAL WASTEWATER TREATMENT EMISSIONS FACTOR DERIVATION

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 WASTE

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual 6.27

TABLE 6-9

UNSPECIFIED WASTEWATER TYPE EMISSIONS FACTOR DERIVATION DATA

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

6.4 Nitrous Oxide from Human Sewage

Since N2O 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 N2O

emissions from nitrogen used in agriculture).

The emissions of N2O from human sewage are calculated as follows:

EQUATION 15

N2O(S) = Protein x FracNPR x NRPEOPLE x EF6

where:

N2O(s) = N2O emissions from human sewage (kg N2O-N/yr)

Protein = annual per capita protein intake (kg/person/yr)

NRPEOPLE = number of people in country

EF6 = emissions factor (default 0.01 (0.002-0.12) kg N2O-N/kg sewageN produced) (See Table 4-18 in Agriculture Chapter)

FracNPR = 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 CO2, 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 CO2 emissions in the IPCC Methodology. If the agricultural or forestry

sources are not being sustainably managed, net CO2 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 CO2

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 WASTE

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 CH4 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 N2O may be an important GHG produced from

incineration. Table 6-10 provides data from studies of several incineration plants and the

N2O produced from the waste incineration (de Soete, 1993). Studies in Belgium (IPCC,

1993), Japan (Tanaka et al., 1992) and Norway (Rosland, 1993) have estimated N2O

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 N2O, sludge incinerators produce the highest

emissions rates (Tanaka et al., 1992).

Traditional air pollutants from combustion - NOx, 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).

TABLE 6-10

NITROUS OXIDE EMISSIONS FROM WASTE INCINERATION

N2O Emission

Nature of Waste

(reference)

Facility ToC ppmva

min.

ppmva

average

ppmva

max.

O2

(%)

g N2O /

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

6.6 References

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