Chapter 2

Energy2

ENERGY

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.1

Energy

Chapter 2

CO-CHAIRS, EDITORS AND EXPERTS
Co-chairs of the Expert Meeting on Emissions f rom Energy
Taka Hiraishi (Japan) and Buruhani Nyenzi (Tanzania)

R E VI E W E D I T O R
Marc Gillet (France)

AUTHORS OF GENERAL BACKGROUND PAPER
Jeroen Meijer (IEA) and Tinus Pullus (Netherlands)

Expert Group: CO 2 Emissions from Stationary Combustion
CO-CHAIRS
Tim Simmons (UK) and Milos Tichy (Czech Republic)

AUTHOR OF BACKGROUND PAPER
Tim Simmons (UK)CONTRIBUTORSAgus Cahyono Adi (Indonesia), Monika Chandra (USA), Sal Emmanuel (Australia), Jean-Pierre Fontelle(France), Pavel Fott (Czech Republic), Kari Gronfors (Finland), Dietmar Koch (Germany), Wilfred Kipondya(Tanzania), Sergio Lamotta (Italy), Elliott Lieberman (USA), Katarina Mareckova (IPCC/OECD), Roberto
Acosta (UNFCCC secretariat), Newton Paciornik (Brazil), Tinus Pulles (Netherlands), Erik Rassmussen(Denmark), Sara Ribacke (Sweden), Bojan Rode (Slovenia), Arthur Rypinski (USA), Karen Treanton (IEA), andStephane Willems (OECD)

Expert Group: Non-CO 2 Emissions from Stationary Combustion
CO-CHAIRS
Samir Amous (Tunisia) and Astrid Olsson (Sweden)

AUTHOR OF BACKGROUND PAPER
Samir Amous (Tunisia)

CONTRIBUTORSIjaz Hossain (Bangladesh), Dario Gomez (Argentina), Markvart Miroslav (Czech Republic), Jeroen Meijer(IEA), Michiro Oi (Japan), Uma Rajarathnam (India), Sami Tuhkanen (Finland), and Jim Zhang (USA)Expert Group: Mobile Combustion: Road Transport
CO-CHAIRS
Michael Walsh (USA) and Samir Mowafy (Egypt)

AUTHOR OF BACKGROUND PAPER
Simon Eggleston (UK)CONTRIBUTORS
Javier Hanna (Bolivia), Frank Neitzert (Canada), Anke Herold (Germany), Taka Hiraishi (Japan), Buruhani
Nyenzi (Tanzania), Nejib Osman (Tunisia), Simon Eggleston (UK), David Greene (UK), Cindy Jacobs (USA),and Jean Brennan (USA)

2.2

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Chapter 2

EnergyExpert Group: Mobile Combustion: Water-borne Navigation
CHAIR

Wiley Barbour (USA)

AUTHORS OF BACKGROUND PAPER
Wiley Barbour, Michael Gillenwater, Paul Jun

CONTRIBUTORS
Leonnie Dobbie (Switzerland), Robert Falk (UK), Michael Gillenwater (USA), Robert Hoppaus (IPCC/OECD),
Roberto Acosta (UNFCCC secretariat), Gilian Reynolds (UK), and Kristin Rypdal (Norway)

Expert Group: Mobile Combustion: Aviation
CHAIR

Kristin Rypdal (Norway)

AUTHOR OF BACKGROUND PAPER
Kristin Rypdal (Norway)

CONTRIBUTORS
Wiley Barbour (USA), Leonie Dobbie (IATA), Robert Falk (UK), Michael Gillenwater (USA), and Robert
Hoppaus (IPCC/OECD)

Expert Group: Fugitive Emissions from Coal Mining and Handling
CO-CHAIRSDavid Williams (Australia) and Oleg Tailakov (Russia)

AUTHORS OF BACKGROUND PAPER
William Irving (USA) and Oleg Tailakov (Russia)

CONTRIBUTORS
William Irving (USA) and Huang Shenchu (China)

Expert Group: Fugitive Emissions from Oil and Natural Gas Activities
CO-CHAIRSDavid Picard (Canada) and Jose Domingos Miguez (Brazil)

AUTHOR OF BACKGROUND PAPER
David Picard (Canada)

CONTRIBUTORSMarc Darras (France), Eilev Gjerald (Norway), Dina Kruger (USA), Robert Lott (USA), Katarina Mareckova(IPCC/OECD), Marc Phillips (USA), and Jan Spakman (Netherlands)

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

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Energy

Chapter 2

Contents
2 ENERGY
2.1 CO2 EMISSIONS FROM STATIONARY COMBUSTION ................................................................2.8
2.1.1

Methodological issues ...............................................................................................................2.8

2.1.2

Reporting and documentation ..................................................................................................2.15

2.1.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.16

Appendix 2.1A.1

Reporting of emissions of fossil carbon-based molecules
according to the Revised 1996 IPCC Guidelines source categories ....................2.18

Appendix 2.1A.2

Method to estimate carbon content based on API gravity and sulfur content ......2.19

Appendix 2.1A.3

1990 country-specific net calorific values ...........................................................2.25

2.2 NON-CO2 EMISSIONS FROM STATIONARY COMBUSTION.....................................................2.37
2.2.1

Methodological issues .............................................................................................................2.37

2.2.2

Reporting and documentation ..................................................................................................2.42

2.2.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.42

2.3 MOBILE COMBUSTION: ROAD VEHICLES .................................................................................2.44
2.3.1

Methodological issues .............................................................................................................2.44

2.3.2

Reporting and documentation ..................................................................................................2.49

2.3.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.49

2.4 MOBILE COMBUSTION: WATER-BORNE NAVIGATION .........................................................2.51
2.4.1

Methodological issues .............................................................................................................2.51

2.4.2

Reporting and documentation ..................................................................................................2.55

2.4.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.56

2.5 MOBILE COMBUSTION: AIRCRAFT .............................................................................................2.57
2.5.1

Methodological issues .............................................................................................................2.57

2.5.2

Reporting and documentation ..................................................................................................2.63

2.5.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.64

Appendix 2.5A.1

Fuel use and average sector distance for representative types of aircraft.............2.65

Appendix 2.5A.2

Correspondence between representative aircraft and other aircraft types ............2.67

Appendix 2.5A.3

Fuel consumption factors for military aircraft......................................................2.69

2.6 FUGITIVE EMISSIONS FROM COAL MINING AND HANDLING..............................................2.70
2.6.1

Methodological issues .............................................................................................................2.70

2.6.2

Reporting and documentation ..................................................................................................2.77

2.6.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.78

2.7 FUGITIVE EMISSIONS FROM OIL AND GAS OPERATIONS.....................................................2.79

2.4

2.7.1

Methodological issues .............................................................................................................2.79

2.7.2

Reporting and documentation ..................................................................................................2.92

2.7.3

Inventory quality assurance/quality control (QA/QC) .............................................................2.93

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyREFERENCES ............................................................................................................................................2.94

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.5

Energy

Chapter 2

Figures

2.6

Figure 2.1

Decision Tree for Selecting the Method for Estimation of CO2
Emissions from Stationary Combustion.........................................................................2.10

Figure 2.2

Decision Tree for Selecting Calorific Values and Carbon Emission Factors.................2.12

Figure 2.3

Decision Tree for Non-CO2 Emissions from Stationary Combustion ............................2.38

Figure 2.4

Decision Tree for CO2 Emissions from Road Vehicles .................................................2.44

Figure 2.5

Decision Tree for CH4 and N2O Emissions from Road Vehicles...................................2.45

Figure 2.6

Decision Tree for Emissions from Water-borne Navigation..........................................2.52

Figure 2.7

Methodology Decision Tree for Aircraft .......................................................................2.58

Figure 2.8

Activity Data Decision Tree for Aircraft .......................................................................2.59

Figure 2.9

Decision Tree for Surface Coal Mining and Handling...................................................2.71

Figure 2.10

Decision Tree for Underground Coal Mining and Handling..........................................2.72

Figure 2.11

Decision Tree for Post-mining.......................................................................................2.73

Figure 2.12

Decision Tree for Natural Gas Systems .........................................................................2.80

Figure 2.13

Decision Tree for Crude Oil Production and Transport.................................................2.81

Figure 2.14

Decision Tree for Crude Oil Refining and Upgrading ...................................................2.82

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTablesTable 2.1

Reporting of Emissions of Fossil Carbon-Containing Molecules
according to the Revised 1996 IPCC Guidelines Source Categories .............................2.18

Table 2.2

Typical API Gravity and Sulfur Content for various Crude Oil Streams .......................2.20

Table 2.3

Average API Gravity and Sulfur Content of Imported Crude Oilfor Selected Countries listed in Annex II of the UN Framework
Convention on Climate Change .....................................................................................2.24

Table 2.4

1990 Country-Specific Net Calorific Values . ...............................................................2.25

Table 2.5

Default Uncertainty Estimates for Stationary Combustion Emission Factors ................2.41

Table 2.6

Level of Uncertainty Associated With Stationary Combustion Activity Data ...............2.41

Table 2.7

Updated Emission Factors for USA Gasoline Vehicles. ................................................2.47

Table 2.8

Criteria for Defining International or Domestic Marine Transport................................2.53

Table 2.9

Distinction between Domestic and International Flights................................................2.61

Table 2.10

Fuel Use and Average Sector Distance for Representative Types of Aircraft. ..............2.65

Table 2.11

Correspondence between Representative Aircraft and Other Aircraft Types ................2.67

Table 2.12

Fuel Consumption Factors for Military Aircraft ............................................................2.69

Table 2.13

Annual Average Fuel Consumption per Flight Hour for United States
Military Aircraft engaged in Peacetime Training Operations ........................................2.69

Table 2.14

Likely Uncertainties of Coal Mine Methane Emission Factors......................................2.77

Table 2.15

Major Categories and Subcategories in the Oil and Gas Industry..................................2.83

Table 2.16

Refined Tier 1 Emission Factors for Fugitive Emissions from Oil and
Gas Operations based on North American Data. ...........................................................2.86

Table 2.17

Typical Activity Data Requirements for each Assessment Approach for Fugitive
Emissions from Oil and Gas Operations by Type of Primary Source Category.............2.89

Table 2.18

Classification of Gas Losses as Low, Medium or High at Selected
Types of Natural Gas Facilities......................................................................................2.91

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

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Energy

Chapter 2

2 EN E R G Y
2.1

CO2 EMISSIONS FROM STATIONARYCOMBUSTION

2.1.1

Methodological issues

Carbon dioxide (CO2) emissions from stationary combustion result from the release of the carbon in fuel during
combustion. CO2 emissions depend on the carbon content of the fuel. During the combustion process, mostcarbon is emitted as CO2 immediately. However, some carbon is released as carbon monoxide (CO), methane(CH4) or non-methane volatile organic compounds (NMVOCs), all of which oxidise to CO2 in the atmosphere
within a period of a few days to about 12 years. The Revised 1996 IPCC Guidelines for National Greenhouse
Gas Inventories (IPCC Guidelines) account for all the released carbon as CO2 emissions. The other carboncontaining gases are also estimated and reported separately. The reasons for this intentional double counting are
explained in the Overview of the IPCC Guidelines. Unoxidised carbon, in the form of particulate matter, soot orash, is excluded from greenhouse gas emissions totals.

2.1.1.1

C HOICE OF METHOD

There are three methods provided in the IPCC Guidelines, Chapter 1, Energy: two Tier 1 approaches (the‘Reference Approach’ and the ‘Sectoral Approach’) and the Tier 2/Tier 3 approach (a detailed technology-based
method, also called ‘bottom-up’ approach).
The Reference Approach estimates CO2 emissions from fuel combustion in several steps:•

Estimation of fossil fuel flow into the country (apparent consumption);•

Conversion to carbon units;•

Subtraction of the amount of carbon contained in long-lived materials manufactured from fuel carbon;•

Multiplication by an oxidation factor to discount the small amount of carbon that is not oxidised;•

Conversion to CO2 and summation across all fuels.

For the Tier 1 Sectoral Approach, total CO2 is summed across all fuels (excluding biomass) and all sectors. For
Tiers 2 and 3, the Detailed Technology-Based Approach, total CO2 is summed across all fuels and sectors, plus
combustion technologies (e.g. stationary and mobile sources). Both approaches provide more disaggregatedemission estimates, but also require more data.
The choice of method is country-specific and is determined by the level of detail of the activity data available as
illustrated in Figure 2.1, Decision Tree for Selecting the Method for Estimation of CO2 Emissions from
Stationary Combustion. The ‘bottom-up’ approach is generally the most accurate for those countries whoseenergy consumption data are reasonably complete.1 Consequently, inventory agencies should make every effort
to use this method if data are available.
Although continuous monitoring is generally recommended because of its high accuracy, it cannot be justified forCO2 alone because of its comparatively high costs and because it does not improve accuracy for CO2. It could,
however, be undertaken when monitors are installed for measurements of other pollutants such as SO2 or NOx
where CO2 is monitored as the diluent gas in the monitoring system.2
The Reference Approach provides only aggregate estimates of emissions by fuel type distinguishing between
primary and secondary fuels, whereas the Sectoral Approach allocates these emissions by source category. The
1 If the gap between apparent consumption and reported consumption is small, then energy consumption data are probably

reasonably complete.
2 If continuous emissions monitoring were used for certain industrial sources it would be difficult to differentiate emissions

related to fuel combustion from emissions related to processing (e.g. cement kilns).

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IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

Energyaggregate nature of the Reference Approach estimates means that stationary combustion emissions cannot be
distinguished from mobile combustion emissions. Likewise, the Sectoral Approach is not always able todifferentiate between different emission source categories within an economic activity (e.g. between use of gas
or oil for heating or for off-road and other mobile machinery in the construction industry).
Estimates of emissions based on the Reference Approach will not be exactly the same as estimates based on the
Sectoral Approach. The two approaches measure emissions at differing points and use slightly different
definitions. However, the differences between the two approaches should not be significant.
For some countries, however, there may be large and systematic differences between estimates developed using
the two approaches. This will normally indicate a systematic under or overcounting of energy consumption by
one method or the other. If this occurs, it is good practice to consult with national statistical authorities and seek
their advice on which method is the most complete and accurate indication of total consumption for each fuel,and use it.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.9

Energy

Chapter 2

Figure 2.1

Decision Tree for Selecting the Method for Estimationof CO2 Emissions from Stationary Combustion

Are
fuel supply
statistics
available?

Obtain fueldata for
Reference
ApproachNo

Yes
Estimate emissions using
the Reference Approach,correcting for bunkers,
stock changes, stored
carbon, and oxidation

Are
data available
for fuel combusted byplant or source
category or
both?

Report both estimation
methods (Reference
Approach and results fromBox 2,3 or 4).
Compare results.

Box 4
Estimate emissions using
the ‘bottom-up’ Tier 2 orTier 3 method

Yes

No
Are
fuel delivery
statistics available
by source
category?

Box 1
No

Is thisa key source
category?
(Note 1)

No

ReportReference
Approach

Yes

Yes

Box 2
Are
estimates available
for fuel combusted inlarge sources?

No

Estimate emissions using
data from sectors,
correcting for oxidationand stored carbon(Tier 1 Sectoral Approach)

Yes
Box 3
Estimate emissions using
data from sectors andplants, correcting foroxidation and stored carbon(Tier 1 and 2,
Sectoral Approach)

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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Chapter 2

2.1.1.2

EnergyC HOICE OF EMISSION FACTORS AND CALORIFIC VALUES

CO2 emission factors (EF) for fossil fuel combustion depend upon the carbon content of the fuel. The carbon
content of a fuel is an inherent chemical property (i.e. fraction or mass of carbon atoms relative to total number ofatoms or mass) and does not depend upon the combustion process or conditions. The energy content (i.e.
calorific value or heating value) of fuels is also an inherent chemical property. However, calorific values vary
more widely between and within fuel types, as they are dependent upon the composition of chemical bonds in thefuel. Net calorific values (NCVs) measure the quantity of heat liberated by the complete combustion of a unit
volume or mass of a fuel, assuming that the water resulting from combustion remains as a vapour, and the heat ofthe vapour is not recovered. Gross calorific values, in contrast, are estimated assuming that this water vapour iscompletely condensed and the heat is recovered. Default data in the IPCC Guidelines are based on NCVs.
Emission factors for CO2 from fossil fuel combustion are expressed on a per unit energy basis because the carbon
content of fuels is generally less variable when expressed on a per unit energy basis than when expressed on a perunit mass basis. Therefore, NCVs are used to convert fuel consumption data on a per unit mass or volume basis
to data on a per unit energy basis.
Carbon content values can be thought of as potential emissions, or the maximum amount of carbon that could
potentially be released to the atmosphere if all carbon in the fuels were converted to CO2. As combustion
processes are not 100% efficient, though, some of the carbon contained in fuels is not emitted to the atmosphere.
Rather, it remains behind as soot, particulate matter and ash. Therefore, an oxidation factor is used to account for
the fraction of the potential carbon emissions remaining after combustion.
For traded fuels in common circulation, it is good practice to obtain the carbon content of the fuel and net
calorific values from fuel suppliers, and use local values wherever possible. If these data are not available,
default values can be used. Figure 2.2, Decision Tree for Selecting Calorific Values and Carbon Emission
Factors illustrates the choice of emission factors.
It may be more difficult to obtain the carbon content and NCV for non-traded fuels, such as municipal solid
waste (MSW) and for fuels that are not sold by heat content, such as crude oil. If necessary, default values areavailable. Values for MSW may be obtained by contacting operators of waste combustion plants for heat raising.
The suggested default values for the NCV of municipal solid waste range from 9.5 to 10.5 GJ/t (based on
information from Sweden and Denmark). The default carbon content of waste is given in Chapter 6, Waste of the
IPCC Guidelines. For crude oil, information is available relating the carbon content to the density and the sulfur
content of the crude oil (see Table 2.2, Typical API Gravities and Sulfur Contents for Various Crude Oil Streams
and Table 2.3, Average API Gravity and Sulfur Content of Imported Crude Oil for Selected Countries Listed in
Annex II of the UN Framework Convention on Climate Change). Information on NCVs for coal types in nonOECD countries is listed in Table 2.4, 1990 country-specific net calorific values. Default net calorific values formost other fuels are available in the Reference Manual of the IPCC Guidelines (Table 1-3, Net Calorific Values
for Other Fuels).
Generally, default oxidation factors for gases and oils are known accurately. For coal, oxidation factors are
dependent on the combustion conditions and can vary by several percent. It is good practice to discuss the factors
with local users of coal and coal products. However, default factors are also provided in the IPCC Guidelines.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.11

Energy

Chapter 2

Figure 2.2

Decision Tree for Selecting Calorific Values andCarbon Emission Factors

Ask fuel supplier (FS),suppliers’ association orplant operator for C
content (emission factor)of fuels and calorificvalue

Compare with default
values in Revised 1996
IPCC Guidelines

No

Is therea significant difference(approx. more than 2%)
between obtained anddefault value?

Yes
Check the obtained
values, ask fuelresearch laboratory toprovide references

Box 1
Is good
explanation for thedifference
available?

No

Consider using
default emission
factorsYes
Box 2
Use obtained (FS) or
estimated value

2.12

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Chapter 2

2.1.1.3

EnergyC HOICE OF ACTIVITY DATA

Activity data for all tiers are the amount and type of fuel combusted. These data will often be available fromnational energy statistics agencies which collect them directly from the enterprises that consume the fuels or fromindividuals responsible for the combustion equipment. These data are also available from suppliers of fuels whorecord the quantities delivered and the identity of their customers usually as an economic activity code, or from a
combination of these sources. Direct collection of fuel consumption data may occur through periodic surveys of asample of enterprises, or, in the case of large combustion plants, through enterprise reports made to the nationalenergy statistics agency or under emission control regulations. Fuel deliveries are well identified for gas, where
metering is in place, and also for solid and liquid fuels, both of which are distributed to the household and thesmall commercial consumers market.
It is good practice to use fuel combustion statistics rather than delivery statistics where they are available.3
Agencies collecting emission data from companies under an environmental reporting regulation could request
fuel combustion data in this context. Fuel combustion data, however, are very seldom complete, since it is notpracticable to measure the fuel consumption or emissions of every residential or commercial source. Hence,national inventories using this approach will generally contain a mixture of combustion data for larger sourcesand delivery data for other sources. The inventory agency must take care to avoid both double counting andomission of emissions when combining data from multiple sources.
Where confidentiality is an issue, direct discussion with the company affected often allows the data to be used. In
cases where such permission is not given, aggregation of the fuel consumption or emissions with those from othercompanies is usually sufficient to conceal the identity of the company without understating emissions.
It is necessary to estimate the amount of carbon stored in products for the Reference Approach, and if no detailed
calculation in the Industrial Processes sector is performed. It is good practice to obtain stored carbon factors bycontacting the petrochemical industry that uses the feedstock. A list of fuels/products that accounts for the
majority of carbon stored is given in the IPCC Guidelines together with default stored carbon factors. It should
be used unless more detailed country-specific information is available. Where data are available for other fuels/
products, the estimation of stored carbon is strongly encouraged.4 The default factor for stored carbon in
lubricants may be overestimated because waste lubricants are often burned for energy. It is good practice tocontact those responsible for recovering used oils in order to discover the extent to which used oils are burned in
the country.
When using the Reference Approach, fuel supply statistics5 should be used and there may be a choice of source
for import and export data. Official customs figures or industry figures may be used. The compilers of nationalenergy data will have made this choice based on their assessment of data quality when preparing national fuelbalances. The choice may differ from fuel to fuel. Thus, it is good practice to consult with the national energy
statistics agency when choosing between energy supply and delivery statistics in order to establish whether thecriteria the agency has used in selecting the basis for import and export statistics of each fuel are appropriate forinventory use.
When activity data are not quantities of fuel combusted but instead deliveries to enterprises or main subcategories, there is a risk of double counting emissions from the Industrial Processes, Solvents or Waste Sectors.
Identifying double counting is not always easy. Fuels delivered and used in certain processes may give rise to byproducts used as fuels elsewhere in the plant or sold for fuel use to third parties (e.g. blast furnace gas, derived
from coke and other carbon inputs to blast furnaces). It is good practice to coordinate estimates between thestationary CO2 source category and relevant industrial categories to avoid double counting or omissions.
Appendix 2.1A.1 lists the categories and subcategories where fossil fuel carbon is reported, and between which
double counting of fossil fuel carbon could, in principle, occur.

3 Quantities of solid and liquid fuels delivered to enterprises will, in general, differ from quantities combusted by theamounts put into or taken from stocks held by the enterprise. Stock figures shown in national fuel balances may not include
stocks held by final consumers, or may include only stocks held by a particular source category (for example electricity
producers). Delivery figures may also include quantities used for mobile sources or as feedstock.
4 The Frauenhofer Institute in Germany is currently undertaking an examination of carbon flows through petrochemicalindustries in a number of countries. It is hoped that this work will result in better estimates of the fraction of petrochemical
feedstock stored within the products manufactured. The study will be completed by mid-2000.
5 These are national production of primary fuels, and imports, exports and stock changes of all fuels. Oils used forinternational bunkers are treated like exports and excluded from supply.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.13

Energy

Chapter 2

For some source categories (e.g. combustion in the Agriculture Sector), there may be some difficulty inseparating fuel used in stationary equipment from fuel used in mobile machinery. Given the different emission
factors for non-CO2 gases of these two sources, good practice is to derive energy use of each of these sources byusing indirect data (e.g. number of pumps, average consumption, needs for water pumping). Expert judgement
and information available from other countries may also be relevant.

2.1.1.4

C OMPLETENESS

A complete estimate of emissions from fuel combustion must include emissions from all fuels and all source
categories identified within the IPCC Guidelines. A reliable and accurate bottom-up CO2 emissions estimate isimportant because it increases confidence in the underlying activity data. These, in turn, are importantunderpinnings for the calculation of CH4 and N2O emissions from stationary sources.
All fuels delivered by fuel producers must be accounted for, so that sampling errors do not arise. Misclassification of enterprises and the use of distributors to supply small commercial customers and households
increase the chance of systematic errors in the allocation of fuel delivery statistics. Where sample survey data thatprovide figures for fuel consumption by specific economic sectors exist, the figures may be compared with thecorresponding delivery data. Any systematic difference should be identified and the adjustment to the allocationof delivery data may then be made accordingly.
Systematic under-reporting of solid and liquid fuels may also occur if final consumers import fuels directly.
Direct imports will be included in customs data and therefore in fuel supply statistics, but not in the statistics offuel deliveries provided by national suppliers. If direct importing by consumers is significant, then the statisticaldifference between supplies and deliveries will reveal the magnitude. Once again, a comparison with
consumption survey results will reveal which main source categories are involved with direct importing.
Experience has shown that the following activities may be poorly covered in existing inventories and theirpresence should be specifically checked:•

Change in producer stocks of fossil fuels;•

Combustion of waste for energy purposes. Waste incineration should be reported in the Waste source
category, combustion of waste for energy purposes should be reported in the Energy source category;•

Energy industries’ own fuel combustion;•

Conversion of petrochemical feedstocks into petrochemical products (carbon storage);•

Fuel combustion for international aviation and marine transport (needed for the Reference Approach).
Sections 2.4.1.3 and 2.5.1.3 of this chapter provide more guidance on this subject.

The reporting of emissions from coke use in blast furnaces requires attention. Crude (or pig) iron is typically
produced by the reduction of iron oxides ores in a blast furnace, using the carbon in coke (sometimes otherreducing agents) as both the fuel and reducing agent. Since the primary purpose of coke oxidation is to produce
pig iron, the emissions should be considered as coming from an industrial process if a detailed calculation ofindustrial emissions is being undertaken. It is important not to double-count the carbon from the consumption ofcoke or other fuels. So, if these emissions have been included in the Industrial Processes sector, they should not
be included in the Energy sector. However, there are countries where industrial emissions are not addressed indetail. In these instances, the emissions should be included in the Energy sector. In any case, the amount ofcarbon that is stored in the final product should be subtracted from the effective emissions.

2.1.1.5

D EVELOPING A CONSISTENT TIME SERIESIt is good practice to prepare inventories using the method selected in Figure 2.1, Decision Tree for Selecting the
Method for Estimation of CO2 Emissions from Stationary Combustion for all years in the time series. Where thisis difficult due to a change of methods or data over time, estimates for missing data in the time series should be
prepared based on backward extrapolation of present data. When changing from a Reference Approach to ahigher tier approach, inventory agencies should establish a clear relationship between the approaches and apply
this to previous years if data are lacking. Chapter 7, Methodological Choice and Recalculation, Section 7.3.2.2,
Alternative Recalculation Techniques, provides guidance on various approaches that can be used in this case.

2.14

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Chapter 2

2.1.1.6

EnergyU NCERTAINTY ASSESSMENT

ACTIVITY DATA
The information in this section can be used in conjunction with the methods outlined in Chapter 6, Quantifying
Uncertainties in Practice, to assess overall uncertainties in the national inventory. Chapter 6 explains how to use
empirical data and expert judgement to obtain country-specific uncertainty.
The accuracy in determining emission estimates using the Sectoral Approach is almost entirely determined by theavailability of the delivery or combustion statistics for the main source categories. The main uncertainty arises
from:•The adequacy of the statistical coverage of all source categories;•

The adequacy of the coverage of all fuels (both traded and non-traded).

Statistics of fuel combusted at large sources obtained from direct measurement or obligatory reporting are likely
to be within 3% of the central estimate.6 For the energy intensive industries, combustion data are likely to be
more accurate. It is good practice to estimate the uncertainties in fuel consumption for the main sub-categories in
consultation with the sample survey designers because the uncertainties depend on the quality of the survey
design and size of sample used.
In addition to any systematic bias in the activity data as a result of incomplete coverage of consumption of fuels,
the activity data will be subject to random errors in the data collection that will vary from year to year. Countries
with good data collection systems, including data quality control, may be expected to keep the random error in
total recorded energy use to about 2-3% of the annual figure. This range reflects the implicit confidence limits on
total energy demand seen in models using historical energy data and relating energy demand to economic factors.
Percentage errors for individual energy use activities can be much larger.
Overall uncertainty in activity data is a combination of both systematic and random errors. Most developed
countries prepare balances of fuel supply and deliveries and this provides a check on systematic errors. In thesecircumstances, overall systematic errors are likely to be small. Experts believe that uncertainty resulting from thetwo errors is probably in the range of ±5%. For countries with less well-developed energy data systems, this
could be considerably larger, probably about ±10%. Informal activities may increase the uncertainty up to as
much as 50% in some sectors for some countries. See Table 2.6, Level of Uncertainty Associated with Stationary
Combustion Activity Data, for more detailed uncertainty estimates.

EMISSION FACTORSThe uncertainty associated with EFs and NCVs results from two main elements, viz. the accuracy with which thevalues are measured, and the variability in the source of supply of the fuel and quality of the sampling ofavailable supplies. There are few mechanisms for systematic errors in the measurement of these properties.
Consequently, the errors can be considered mainly random. For traded fuels, the uncertainty is likely to be lessthan 5%. For non-traded fuels, the uncertainty will be higher and will result mostly from variability in the fuelcomposition.
Default uncertainty ranges are not available for stored carbon factors or coal oxidation factors. It is evident,
however, that consultation with consumers using the fuels as raw materials or for their non-fuel characteristics isessential for accurate estimations of stored carbon. Similarly, large coal users can provide information on thecompleteness of combustion in the types of equipment they are using.

2.1.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
6 The percentages cited in this section represent an informal polling of assembled experts aiming to approximate the 95%

confidence interval around the central estimate.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.15

Energy

Chapter 2

Some examples of specific documentation and reporting which are relevant to this source category are provided
below:•The sources of the energy data used and observations on the completeness of the data set;•

The sources of the calorific values and the date they were last revised;•

The sources of emission factors and oxidation factors, the date of the last revision and any verification of theaccuracy. If a carbon storage correction has been made, documentation should include the sources of thefactor and how the figures for fuel deliveries have been obtained.

2.1.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Comparison of emission estima tes using different approaches
The inventory agency should compare estimates of CO2 emissions from fuel combustion prepared using theSectoral Tier 1 and Tier 2 Approach with the Reference Approach, and account for any significant differences. In
this comparative analysis, emissions from fuels other than by combustion, that are accounted for in other sectionsof a GHG inventory, should be subtracted from the Reference Approach (See Appendix 2.1A.1).
Activity da ta check•

The inventory agency should construct national energy balances expressed in mass units, and mass balancesof fuel conversion industries. The time series of statistical differences should be checked for systematiceffects (indicated by the differences persistently having the same sign) and these effects eliminated where
possible. This task should be done by, or in cooperation with, the national agency in charge of energy
statistics.

•

The inventory agency should also construct national energy balances expressed in energy units and energybalances of fuel conversion industries. The time series of statistical differences should be checked, and thecalorific values cross-checked with IEA values (see Figure 2.2, Decision Tree for Selecting Calorific Values
and Carbon Emission Factors). This step will only be of value where different calorific values for aparticular fuel (for example, coal) are applied to different headings in the balance (such as production,
imports, coke ovens and households). Statistical differences that change in magnitude or sign significantly
from the corresponding mass values provide evidence of incorrect calorific values.

•

The inventory agency should confirm that gross carbon supply in the Reference Approach has been adjusted
for fossil fuel carbon from imported or exported non-fuel materials in countries where this is expected to besignificant.

•Energy statistics should be compared with those provided to international organisations to identify
inconsistencies.

•

There may be routine collections of emissions and fuel combustion statistics at large combustion plants forpollution legislation purposes. If possible, the inventory agency can use these plant-level data to cross-checknational energy statistics for representativeness.

Emission factors check•

2.16

The inventory agency should construct national energy balances expressed in carbon units and carbon
balances of fuel conversion industries. The time series of statistical differences should be checked. Statisticaldifferences that change in magnitude or sign significantly from the corresponding mass values provide
evidence of incorrect carbon content.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2•

EnergyMonitoring systems at large combustion plants may be used to check the emission and oxidation factors in
use at the plant.

Evaluation of direct measurements•

The inventory agency should evaluate the quality control associated with facility-level fuel measurementsthat have been used to calculate site-specific emission and oxidation factors. If it is established that there isinsufficient quality control associated with the measurements and analysis used to derive the factor,
continued use of the factor may be questioned.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.17

Energy

Chapter 2

Appendix 2.1A.1 Reporting of emissions of fossil
carbon-based molecules according to the Revised
1996 IPCC Guidelines source categories
The following table shows where fossil carbon is accounted for and may be used to help identify and eliminate
double counting as discussed in Section 2.1.1.3. It may also help explain any difference between the Reference
Approach and Sectoral Approach calculations.
TABLE 2.1
REPORTING OF EMISSIONS OF FOSSIL CARBON-CONTAINING MOLECULES ACCORDING TO THE REVISED 1996 IPCC
GUIDELINES SOURCE CATEGORIES7
From fossil fuel carbon

From other fossil carbon

1A Fuel combustion
All fossil carbon for combustion purposes
1B Fugitive emissions
Escapes and releases from fossil carbon flows fromextraction point through to final oxidation
2 Industrial Processes

2 Industrial Processes

Ammonia

CementSilicon carbide

Lime production

Calcium carbide

Limestone use

Soda ash production, Solvay process(emissions from calcining)

Soda ash production (natural process)Iron/steel and ferroalloys

Soda ash use

Aluminium
Other metals (see IPCC Guidelines Reference Manual,
Table 2-21, Production Processes for Some Metals)
Production and use of halocarbons
Organic chemical manufacture
Asphalt manufacture and use
Adipic acid
3 Solvents
6 WasteShort-life wastes comprising used oils, used solvents andplastics
Long-life wastes comprising plastics entering heat raisingand incineration and degradation in landfills (products
manufactured before the inventory year)

7 Numbers before source categories correspond to the numbering system of the Revised 1996 IPCC Guidelines, Reporting
Instructions, Common Reporting Framework.

2.18

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyAppendix 2.1A.2 Method to estimate carbon
content based on API8 gravity and sulfur content
The following formula is based on the analyses of 182 crude oil samples and may be used to estimate the carbon
content of crude oil. (Source: USDOE/EIA. URL: http://www.eia.doe.gov/oiaf/1605/gg98rpt/appendixb.html)
EQUATION 2.1
Carbon Content = 76.99 + (10.19 • SG) – (0.76 • Sulfur Content)
Where:
SG denotes the specific gravity of the oil
Carbon and Sulfur content are measured in percent by weight

Specific Gravity may be calculated from the API gravity figure using:
EQUATION 2.2
SG = 141.5 / (API + 131.5)

Inferred carbon content is calculated based on the specific gravities and the API values in the first 2 columns of
the following table using the above formula. Note that inferred values may differ from measured values.

8 API: Arbitrary scale designating an oil's specific gravity, or the ratio of the weights of equal volumes of oil and pure water;

it is the standard specific gravity scale of the petroleum industry. As volume is dependent on temperature and pressure, thesemust be specified. In the United States they are generally 60 degrees F (16 degrees C) and one atmosphere (101.3 kPa)pressure. The API gravity scale, whose units are degrees API, does not vary linearly with the specific gravity or its related
properties (e.g. viscosity), high specific gravity values give low API gravity values using the relationshipdegrees API = (141.5 / specific gravity at 60 degrees F) – 131.5
Water with a specific gravity of 1 has an API gravity of 10 degrees. The API scale has the advantage of allowinghydrometers, which measure specific gravity, to be calibrated linearly. The Baumé scale, originally developed by Antoine
Baumé for this purpose, was found to be in error and the API scale replaced it in 1921. The Baumé scale, still used in parts ofEurope, is given by the relationshipdegrees Baumé = (140 / specific gravity at 60 degrees F) – 130.
Source: adapted from Encyclopaedia Britannica.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.19

Energy

Chapter 2

TABLE 2.2
TYPICAL API GRAVITY AND SULFUR CONTENT FOR VARIOUS CRUDE OIL STREAMS
Crude Category

Typical API
Gravitymean or
lower
value

upper
value

Typical Sulfur
Content (% wt)
mean or
lower
value

upper
value

Inferred Carbon Content(% wt)
mean orlower value

upper value

Middle East
Abu Dhabi

Murban

39.8

0.8

84.8

Umm Shaif

37.5

1.4

84.5

Upper Zakum

34

1.8

84.3

Lower Zakum

40

1.1

84.6

Other Abu Dhabi

46.7

0.8

84.5

Dubai

31

1.9

84.4

62.5

0.1

84.3

Iranian Light

34

1.4

84.6

Iranian Heavy

31

1.6

84.6

Other Iran

32.6

2.1

84.2

Basrah Light

34

2.1

84.1

Kirkuk

36

2

84.1

Other Iraq

36.1

2

84.1

KuwaitKuwait Blend

30

31

2.5

84.0

84.0

Neutral Zone

Offshore (Khafji/Hout)

28

33

1.9

2.9

83.6

84.6

Onshore

23

25

3.3

3.9

83.2

83.8

Oman

Oman

34

0.8

85.1

Qatar

Qatar Marine

36

1.5

84.5

Qatar Land

41

1.2

84.4

Arab Light

33

34

1.7

84.4

84.5

Arab Medium

30

31.5

2.3

84.1

84.2

Arab Heavy

27

28

2.8

83.9

84.0

Berri (Extra Light)

37

38

1.1

84.6

84.7

Other Saudi Arabia

52.3

0.7

84.3

Syria Light

36

0.6

85.1

Souedie

24

3.9

83.3

Marib Light

40

0.1

85.3

Masila Blend

30

0.6

85.4

Other Yemen

41

0.4

85.0

Dubai
Sharjah
Iran

Iraq

Saudi Arabia

Syria

Yemen

2.20

32

31

1.2

84.4

85.5

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.2 (CONTINUED)TYPICAL API GRAVITY AND SULFUR CONTENT FOR VARIOUS CRUDE OIL STREAMS
Crude Category

Typical API
Gravitymean or
lower
value

Other Middle East

upper
value

Typical Sulfur
Content (% wt)
mean or
lower
value

upper
value

Inferred Carbon Content(% wt)
mean orlower value

31.7

2.1

84.2

Saharan Blend

44

0.1

85.1

Other Algeria

45.1

0.1

85.1

32

0.15

85.7

37.4

0.1

85.5

Medium/Light (30-40 )

31.1

1.9

84.4

Heavy (<30o API)

27.9

2.1

84.4

Rabi/Rabi Kounga

34

0.1

85.6

Other Gabon

32.1

0.6

85.3

Light (>40 API)

41.7

0.2

85.2

Medium (30-40o API)

37.2

0.3

85.3

o

26.2

1.7

84.8

29.6

0.2

85.8

Light (33-45 API)

36.3

0.2

85.4

Condensate (>45o API)

46.1

0.1

85.0

Tunisia

36.1

0.6

85.1

Zaire

31

0.2

85.7

Other Africa

29.7

0.2

85.8

Seria Light

36

0.1

85.5

Champion

25

0.1

86.1

Daqing (Taching)

33

0.1

85.7

Shengli

24

1

85.5

Other China

32

0.2

85.7

Minas

34

0.1

85.6

Cinta

33

0.1

85.7

Handil

33

0.1

85.7

Duri

20

0.2

86.4

Arun Condensate

54

0.02

84.7

Other Indonesia

38

0.1

85.4

Tapis

44

0.1

85.1

Labuan

33

0.1

85.7

Other Malaysia

38.9

0.1

85.4

upper value

AfricaAlgeria

Cameroon
Congo
Egypt

Gabon

Libya

o

o

Heavy (<30 API)
NigeriaoMedium (<33 API)oAsia
Brunei

China

Indonesia

Malaysia

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.21

Energy

Chapter 2

TABLE 2.2 (CONTINUED)TYPICAL API GRAVITY AND SULFUR CONTENT FOR VARIOUS CRUDE OIL STREAMS
Crude Category

Typical API
Gravitymean or
lower
value

Other Asia
Australia

mean or
lower
value

upper
value

Inferred Carbon Content(% wt)
mean orlower value

52.6

0.04

84.8

Gippsland

45

0.1

85.1

Other Australia

41.1

0.1

85.3

44.3

0.04

85.2

Papua New
GuineaRussia

upper
value

Typical Sulfur
Content (% wt)

Urals

31

32.5

1.2

1.4

84.7

Other Russia

33.3

1.2

84.8

Azerbaijan

47.7

0.01

85.0

Kazakhstan

46.5

0.5

84.7

Ukraine

40.1

0.9

84.7

Other FSU

44.6

0.2

85.0

upper value

85.0

EuropeDenmark
NorwayUnitedKingdom

33

34.5

0.3

85.4

85.5

Statfjord

37.5

38

0.28

85.3

85.3

Gullfaks

29.3

29.8

0.44

85.6

85.6

Oseberg

34

0.3

85.5

Ekofisk

43.4

0.14

85.1

Other Norway

32.3

0.3

85.6

Brent Blend

37

38

0.4

85.2

85.2

Forties

39

40

0.34

85.1

85.2

Flotta

34.7

1

84.9

Other UK

31.8

0.5

85.4

35.9

1.3

84.6

Light Sweet (>30o API)

36.6

0.2

85.4

Heavy (<30o API)

23.4

Alaska

30.2

1.1

85.1

Other United States

39.5

0.2

85.3

Other Europe
North America
CanadaUnited States

2.22

not available

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.2 (CONTINUED)TYPICAL API GRAVITY AND SULFUR CONTENT FOR VARIOUS CRUDE OIL STREAMS
Crude Category

Typical API
Gravitymean or
lower
value

upper
value

Typical Sulfur
Content (% wt)
mean or
lower
value

upper
value

Inferred Carbon Content(% wt)
mean orlower value

upper value

Latin America
BrazilColombia

Ecuador

20.7

0.5

86.1

Cano Limon

30

0.5

85.5

Other Colombia

35.8

not available

Oriente28

Other Ecuador
Mexico

0.9

1.0

85.2

not available

not available

Maya

22.2

3.3

83.9

Isthmus

34.8

1.5

84.5

Olmeca

39.8

0.8

84.8

20.2

1.3

85.5

Light (>30 API)

32.6

1.1

84.9

Medium (22-30o API)

27.7

1.6

84.8

19.5

2.5

84.6

14.5

2.8

84.7

Peru
Venezuela

29

o

o

Heavy (17-22 API)
Extra Heavy (<17
API)

o

85.3

Source for API gravity and sulfur content: International Energy Agency.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.23

Energy

Chapter 2

TABLE 2.3
AVERAGE API GRAVITY AND SULFUR CONTENT OF IMPORTED CRUDE OIL FOR SELECTED COUNTRIES LISTED IN
ANNEX II OF THE UN FRAMEWORK CONVENTION ON CLIMATE CHANGE
Average API Gravity

Average Sulfur(% weight)

Inferred Carbon Content(% weight)

Australia

39.9

0.34

85.1

Austria

37.4

0.84

84.9

Belgium

32.8

1.25

84.8

Canada

32.4

0.90

85.1

Denmark

40.9

0.22

85.2

Finland

35.8

0.54

85.2

France

35.8

1.01

84.8

Germany

36.5

0.76

85.0

Greece

33.9

1.65

84.5

Ireland

36.9

0.25

85.4

Italy

34.1

1.15

84.8

Japan

34.8

1.51

84.5

Netherlands

33.3

1.45

84.6

New Zealand

34.4

1.01

84.9

Norway

33.3

0.39

85.4

Portugal

33.2

1.39

84.7

Spain

31.5

1.36

84.8

Sweden

34.5

0.76

85.1

Switzerland

39.4

0.46

85.1

Turkey

34.2

1.48

84.6

UnitedKingdom

35.9

0.64

85.1

United States

30.3

not available

Average API gravity and sulfur content has been calculated from imports into the above countries in 1998. Values will change over time
due to changes in crude streams that are imported. Any domestic crude oil consumed in the country would also need to be taken into
account.
Source for API gravity and sulfur content: International Energy Agency.

2.24

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyAppendix 2.1A.3
1990a country-specific net calorific values
The following table is an update from the table supplied in the Revised 1996 IPCC Guidelines. It contains moredisaggregated information on coal. Some values have been revised by the International Energy Agency.

TABLE 2.4
a1990 COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Albania

Algeria

Angola Argentina Armenia Australia
CabindaAustria

Azerbaijan

Bahrain

41.45

43.29

42.75

42.29

-

43.21

NGL

-

43.29

-

42.50

-

Refinery Feedst.

-

-

-

-

-

Production

-

25.75

-

-

Imports

27.21

25.75

-

Exports--

Bangla- Belarus
desh

42.75

42.08

42.71

42.16

45.22

45.22

41.91

42.71

42.71

-

42.50

42.50

-

-

-

-

-

28.34

-

-

-

-

-

30.14

-

-

28.00

-

-

-

-

-

-

-

28.21

-

-

-

-

-

-

24.70

-

24.39

-

-

-

-

-

OIL
Crude Oil

42.08

COAL
Coking Coal

Other Bituminous Coal and Anthracite-c

Production-

Imports

27.21

-

-

-

18.58

-

28.00

18.58

-

20.93

25.54

Exports

-

-

-

24.70

-

25.65

-

-

-

-

25.54

Production

-

-

-

-

-

17.87

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

9.84

-

-

-

-

9.31

10.90

-

-

-

-

Imports

-

-

-

-

-

-

10.90

-

-

-

-

Exports

9.84

-

-

-

-

-

10.90

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Sub-Bituminous Coal

LigniteCoal Products
Patent Fuel
BKB
Coke Oven Coke
Gas Coke

-

-

-

-

-

21.00

19.30

-

-

-

8.37

27.21

27.21

-

28.46

-

25.65

28.20

-

-

-

25.12

-

-

-

-

-

-

-

-

-

-

-

a

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.25

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Belgium

Benin

Bolivia

BosniaHerzegovina

42.75

42.58

43.33

-

-

-

43.33

-

42.50

-

-

-

Production

-

-

-

Imports

29.31-

Exports--

BrazilBrunei

Bulgaria

Cameroon Canada

Chile

China

45.64

42.75

42.62

42.45

42.79

42.91

42.62

45.22

42.75

-

-

45.22

42.87

-

-

41.87

-

-

-

-

-

-

26.42

-

-

-

28.78

-

20.52

-

-

30.69

-

24.70

-

27.55

28.43

20.52

-

-

-

-

-

-

28.78

-

20.52

OIL
Crude Oil
NGL
Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

25.00

-

-

-

15.99

-

24.70

-

28.78

28.43

20.52

Imports

25.00

-

-

-

-

-

24.70

-

27.55

28.43

20.52

Exports

25.00

-

-

-

-

-

-

-

28.78

-

20.52

Sub-Bituminous Coal
Production

18.10

-

-

-

-

-

-

-

17.38

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

18.20

-

-

-

-

-

-

-

-

-

-

Production

-

-

-

8.89

-

-

7.03

-

14.25

17.17

-

Imports

21.56

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

14.25

-

-

Patent Fuel

29.31

-

-

-

-

-

-

-

-

-

-

BKB

20.10

-

-

-

-

-

20.10

-

-

-

-

Coke Oven Coke

29.31

-

-

-

30.56

-

27.21

-

27.39

28.43

28.47

-

-

-

-

-

-

-

-

-

-

-

LigniteCoal Products

Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.26

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Colombia

Congo

Costa Rica Croatia

Cuba

CyprusCzech
Democratic Denmark Dominican
Republic Republic ofRepublic
Congo

OIL
Crude Oil

42.24

42.91

42.16

42.75

41.16

42.48

41.78

42.16

42.71

42.16

NGL

41.87

-

-

45.22

-

-

-

-

-

-

-

-

-

-

-

-

-

-

42.50

-

Production

27.21

-

-

-

-

-

24.40

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

Exports

27.21

-

-

-

-

-

27.46

-

-

-

Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

27.21

-

-

25.12

-

-

18.19

25.23

-

-

Imports

-

-

25.75

29.31

25.75

25.75

18.19

25.23

26.09

25.75

Exports

27.21

-

-

-

-

-

18.19

-

26.09

-

Sub-Bituminous Coal
Production

-

-

-

-

-

-

12.29

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

21.28

-

-

-

Production

-

-

-

-

-

-

12.29

-

-

-

Imports

-

-

-

14.60

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

29.31

-

-

LigniteCoal Products
Patent Fuel
BKB
Coke Oven Coke
Gas Coke

-

-

-

-

-

-

21.28

-

18.27

-

20.10

-

27.21

29.31

27.21

-

27.01

27.21

31.84

-

-

-

-

-

-

-

-

-

-

-

a

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.27

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

DPR of Ecuador
Korea

Egypt

El
Estonia Ethiopia Federal
Finland FYR of
FormerFranceSalvador
Republic ofMacedonia Yugoslavia
Yugoslavia

OIL
Crude Oil

42.16

41.87

42.54

42.16

-

42.62

42.75

44.03

42.75

42.75

42.75

NGL

-

42.45

42.54

-

-

-

-

-

-

-

45.22

Refinery Feedst.

-

-

-

-

-

-

-

42.50

-

-

42.50

Production

25.75

-

-

-

-

-

-

-

-

-

28.91

Imports

25.75

-

25.75

-

-

-

-

26.38

30.69

30.69

30.50

Exports

-

-

-

-

-

-

-

-

30.13

-

-

COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

25.75

-

-

-

-

-

23.55

-

-

23.55

26.71

Imports

-

-

25.75

-

18.58

-

30.69

26.38

30.69

-

25.52

Exports

25.75

-

-

-

18.58

-

-

-

-

-

26.43

Sub-Bituminous Coal
Production

17.58

-

-

-

-

-

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

-

-

-

-

9.44

-

8.89

-

8.89

8.89

17.94

Imports

-

-

-

-

9.44

-

-

-

16.91

16.91

17.94

Exports

-

-

-

-

9.44

-

-

-

16.90

16.90

-

Patent Fuel

-

-

-

-

-

-

-

-

-

-

30.07

BKB

-

-

-

-

8.37

-

-

-

-

20.10

20.10

27.21

-

27.21

-

25.12

-

-

28.89

-

26.90

28.71

-

-

-

-

-

-

-

-

-

-

-

LigniteCoal Products

Coke Oven Coke
Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.28

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Gabon

Georgia

Germany Ghana

GreeceGuatemalaHaiti

Honduras Hong
Kong,
China

Hungary Iceland

OIL
Crude Oil

42.62

42.08

42.75

42.62

42.75

42.45

-

42.16

-

41.00

-

NGL

-

-

-

-

45.22

-

-

-

-

45.18

-

Refinery Feedst.

-

-

42.50

-

42.50

-

-

-

-

42.08

-

Production

-

-

28.96

-

-

-

-

-

-

29.61

-

Imports

-

-

28.96

-

-

-

-

-

-

30.76

29.01

Exports

-

-

28.96

-

-

-

-

-

-

-

-

COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

-

18.58

24.96

-

-

-

-

-

-

13.15

-

Imports

-

18.58

26.52

25.75

27.21

-

25.75

-

25.75

21.50

29.01

Exports

-

18.58

31.71

-

-

-

-

-

-

20.15

-

Production

-

-

-

-

-

-

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

-

-

8.41

-

5.74

-

-

-

-

9.17

-

Imports

-

-

14.88

-

-

-

-

-

-

15.46

-

Exports

-

-

8.40

-

-

-

-

-

-

-

-

Patent Fuel

-

-

31.40

-

-

-

-

-

-

16.80

-

BKB

-

-

20.58

-

15.28

-

-

-

-

21.23

-

Coke Oven Coke

-

-

28.65

-

29.30

-

-

27.21

27.21

27.13

26.65

Gas Coke

-

-

-

-

-

-

-

-

-

-

-

Sub-Bituminous Coal

LigniteCoal Productsa

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.29

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

India

Indonesia

Iran

Iraq

IrelandIsrael

Italy

Ivory
Coast

JamaicaJapan

JordanOIL
Crude Oil

42.79

42.66

42.66

42.83

42.83

42.54

42.75

42.62

42.16

42.62

42.58

NGL

43.00

42.77

42.54

42.83

-

-

45.22

-

-

46.05

-

-

-

-

-

42.50

-

42.50

-

-

42.50

-

Production

19.98

-

25.75

-

-

-

-

-

-

30.63

-

Imports

25.75

-

25.75

-

29.10

-

30.97

-

-

30.23

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

19.98

25.75

25.75

-

26.13

-

26.16

-

-

23.07

-

Imports

25.75

25.75

-

-

29.98

26.63

26.16

-

25.75

24.66

-

Exports

19.98

25.75

-

-

26.13

-

-

-

-

-

-

Sub-Bituminous Coal
Production

-

-

-

-

-

-

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

9.80

-

-

-

-

4.19

10.47

-

-

-

-

Imports

-

-

-

-

19.82

-

10.47

-

-

-

-

Exports

-

-

-

-

19.82

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

27.05

-

BKB

20.10

-

-

-

20.98

-

-

-

-

-

-

Coke Oven Coke

27.21

27.21

27.21

-

32.66

-

29.30

-

-

28.64

-

-

-

-

-

-

-

-

-

-

28.64

-

LigniteCoal Products
Patent Fuel

Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.30

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Kazakhstan Kenya

Korea

KuwaitKyrgyzstan Latvia

Lebanon Libya

Lithuania Luxem- Malaysia
bourg

OIL
Crude Oil

42.08

42.08

42.71

42.54

42.08

-

42.16

43.00

42.08

-

42.71

NGL

41.91

-

-

42.62

-

-

-

43.00

-

-

43.12

-

-

-

-

-

-

-

-

44.80

-

42.54

Production

18.58

-

-

-

-

-

-

-

-

-

-

Imports

18.58

-

27.21

-

-

-

-

-

-

-

-

Exports

18.58

-

-

-

-

-

-

-

-

-

-

Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

18.58

-

19.26

-

18.58

-

-

-

-

-

25.75

Imports

18.58

25.75

27.21

-

18.58

18.58

-

-

18.59

29.30

25.75

Exports

18.58

-

-

-

18.58

25.12

-

-

18.59

-

25.75

Sub-Bituminous Coal
Production

-

-

-

-

-

-

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

14.65

-

-

-

14.65

-

-

-

-

-

-

Imports

18.58

-

-

-

14.65

-

-

-

-

20.03

-

Exports

18.58

-

-

-

-

-

-

-

-

-

-

Patent Fuel

-

-

-

-

-

-

-

-

-

-

-

BKB

-

-

-

-

-

8.37

-

-

8.37

20.10

-

25.12

-

27.21

-

-

25.12

-

-

-

28.50

27.21

-

-

-

-

-

-

-

-

-

-

-

LigniteCoal Products

Coke Oven Coke
Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal - the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.31

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Malta

MexicoMoldova Morocco Mozam- Myanmar Nepal
bique

Netherlands

Netherlands
AntillesNew
Zealand

Nicaragua

OIL
Crude Oil

-

42.35

-

38.94

-

42.24

-

42.71

42.16

45.93

42.16

NGL

-

46.81

-

-

-

42.71

-

45.22

-

49.75

-

Refinery Feedst.

-

-

-

-

-

-

-

-

-

47.22

-

Production

-

24.72

-

-

-

-

-

-

-

28.00

-

Imports

-

30.18

-

-

-

-

-

28.70

-

28.00

-

Exports

-

22.41

-

-

-

-

-

-

-

28.00

-

COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

-

-

-

23.45

25.75

25.75

-

-

-

26.00

-

Imports

25.75

-

18.58

27.63

25.75

25.75

25.12

26.60

-

-

-

Exports

-

-

-

-

-

-

-

26.60

-

-

-

Production

-

18.20

-

-

-

-

-

-

-

21.30

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

-

-

-

-

-

8.37

-

-

-

14.10

-

Imports

-

-

-

-

-

-

-

20.00

-

-

-

Exports

-

-

-

-

-

-

-

20.00

-

-

-

Patent Fuel

-

-

-

-

-

-

-

29.30

-

-

-

BKB

-

-

-

-

-

-

-

20.00

-

-

-

Coke Oven Coke

-

27.96

25.12

27.21

-

27.21

-

28.50

-

-

-

Gas Coke

-

-

-

-

-

-

-

-

-

-

-

Sub-Bituminous Coal

LigniteCoal Productsa

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.32

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Nigeria

NorwayOman

Pakistan

PanamaParaguay Peru

Philippines

PolandPortugal

Qatar

OIL
Crude Oil

42.75

42.96

42.71

42.87

42.16

42.54

42.75

42.58

41.27

42.71

42.87

NGL

42.75

45.22

42.71

42.87

-

-

42.75

-

-

-

43.00

-

42.50

-

-

-

-

-

-

44.80

42.50

-

Production

-

-

-

-

-

-

-

-

-

-

-

Imports

-

-

-

27.54

-

-

29.31

-

-

29.30

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

25.75

28.10

-

18.73

-

-

29.31

20.10

22.95

-

-

Imports

-

28.10

-

-

25.75

-

-

20.52

29.41

26.59

-

Exports

25.75

28.10

-

-

-

-

-

-

25.09

-

-

Sub-Bituminous Coal
Production

-

-

-

-

-

-

-

-

-

17.16

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

-

-

-

-

-

-

-

8.37

8.36

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

9.00

-

-

Patent Fuel

-

-

-

-

-

-

-

-

22.99

-

-

BKB

-

-

-

-

-

-

-

-

17.84

-

-

27.21

28.50

-

27.21

-

-

27.21

27.21

27.85

28.05

-

-

-

-

-

-

-

-

-

-

-

-

LigniteCoal Products

Coke Oven Coke
Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.33

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

Romania Russia

Saudi
ArabiaSenegalSingapore

SlovakSlovenia
Republic

South
AfricaSpain

Sri Lanka Sudan

OIL
Crude Oil

40.65

42.08

42.54

42.62

42.71

41.78

42.75

38.27

42.66

42.16

42.62

NGL

-

-

42.62

-

-

45.18

-

-

45.22

-

-

Refinery Feedst.

-

-

-

-

-

-

42.50

-

42.50

-

-

Production

16.33

18.58

-

-

-

-

-

30.99

29.16

-

-

Imports

25.12

25.12

-

-

-

23.92

30.69

-

30.14

-

-

Exports

-

18.58

-

-

-

-

-

30.99

-

-

-

COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

16.33

18.58

-

-

-

-

-

23.60

21.07

-

-

Imports

25.12

18.58

-

-

-

23.92

30.69

-

25.54

25.75

-

Exports

-

18.58

-

-

-

-

-

27.99

23.00

-

-

Production

-

-

-

-

-

-

8.89

-

11.35

-

-

Imports

-

-

-

-

-

-

16.91

-

11.35

-

-

Exports

-

-

-

-

-

-

16.90

-

-

-

-

Production

7.24

14.65

-

-

-

12.26

8.89

-

7.84

-

-

Imports

7.24

-

-

-

9.67

12.20

16.91

-

-

-

-

Exports

-

14.65

-

-

-

15.26

16.90

-

-

-

-

Patent Fuel

14.65

-

-

-

-

-

-

-

29.30

-

-

BKB

14.65

20.10

-

-

-

21.28

-

-

20.22

-

-

Coke Oven Coke

20.81

25.12

-

-

27.21

27.01

26.90

27.88

30.14

-

-

-

-

-

-

-

-

-

-

-

-

-

Sub-Bituminous Coal

LigniteCoal Products

Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.34

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyTABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

SwedenSwitzerland Syria

Tajikistan Tanzania Thailand Trinidad Tunisia
andTobagoTurkeyTurkUkraine
menistan

OIL
Crude Oil

42.75

43.22

42.04

42.08

42.62

42.62

42.24

43.12

42.79

42.08

42.08

-

-

-

41.91

-

46.85

-

43.12

-

41.91

-

42.50

43.70

-

-

-

-

-

-

42.50

-

-

Production

-

-

-

-

25.75

-

-

-

32.56

-

21.59

Imports

30.00

-

-

-

-

-

-

-

33.54

-

-

Exports

-

-

-

-

-

-

-

-

-

-

21.59

NGL
Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

14.24

-

-

-

25.75

-

-

-

30.04

-

21.59

Imports

26.98

28.05

-

18.58

-

26.38

-

25.75

27.89

18.58

25.54

Exports

26.98

28.05

-

-

-

-

-

-

-

-

21.59

Sub-Bituminous Coal
Production

-

-

-

14.65

-

-

-

-

18.00

-

-

Imports

-

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

-

Production

-

-

-

-

-

12.14

-

-

9.63

-

14.65

Imports

8.37

-

-

-

-

-

-

-

12.56

-

14.65

Exports

-

-

-

-

-

-

-

-

-

-

14.65

-

28.05

-

-

-

-

-

-

-

-

29.31

BKB

20.10

20.10

-

-

-

-

-

-

20.93

-

-

Coke Oven Coke

28.05

28.05

-

-

27.21

27.21

-

27.21

29.31

-

25.12

-

-

-

-

-

-

-

-

27.21

-

-

LigniteCoal Products
Patent Fuel

Gas Cokea

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.35

Energy

Chapter 2

TABLE 2.4 (CONTINUED)
1990a COUNTRY-SPECIFIC NET CALORIFIC VALUESb(Terajoule per
kilotonne)

UnitedArab
Emirates

UnitedKingdom

UnitedStatesUruguay Uzbekistan

Venezuela Vietnam

Yemen

ZambiaZimbabwe

OIL
Crude Oil

42.62

43.40

43.12

42.71

42.08

42.06

42.61

43.00

42.16

-

NGL

42.62

46.89

47.69

-

41.91

41.99

-

-

-

-

-

42.50

43.36

-

44.80

-

-

-

-

-

Production

-

29.27

29.68

-

-

-

-

-

24.71

25.75

Imports

-

30.07

-

-

-

-

-

-

-

-

Exports

-

29.27

29.68

-

-

-

-

-

-

-

Refinery Feedst.
COAL
Coking Coal

Other Bituminous Coal and Anthracitec

Production

-

24.11

26.66

-

18.58

25.75

20.91

-

24.71

25.75

Imports

-

26.31

27.69

-

18.58

-

-

-

-

25.75

Exports

-

27.53

28.09

-

-

25.75

20.91

-

24.71

25.75

Production

-

-

19.43

-

-

-

-

-

-

-

Imports

-

-

-

-

-

-

-

-

-

-

Exports

-

-

-

-

-

-

-

-

-

-

Production

-

-

14.19

-

14.65

-

-

-

-

-

Imports

-

-

-

-

14.65

-

-

-

-

-

Exports

-

-

14.19

-

14.65

-

-

-

-

-

Patent Fuel

-

26.26

-

-

29.31

-

-

-

-

-

BKB

-

-

-

-

-

-

-

-

-

-

Coke Oven Coke

-

26.54

27.47

27.21

-

-

27.21

-

27.21

27.21

Gas Coke

-

-

-

-

-

-

-

-

-

-

Sub-Bituminous Coal

LigniteCoal Productsa

For the former Soviet and Yugoslav Republics, 1996 numbers have been used.

b

The NCVs are those used by the IEA in the construction of energy balances.

c

In IEA statistics, Anthracite is combined with Other Bituminous Coal – the NCVs given above reflect this combination.

Source: Energy Balances of OECD Countries, and Energy Statistics and Balances of Non-OECD Countries.
OECD/IEA, Paris, 1998.

2.36

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

Energy2.2

NON-CO2 EMISSIONS FROM STATIONARYCOMBUSTION

2.2.1

Methodological issues

For stationary sources, some non-CO2 emissions such as methane (CH4), carbon monoxide (CO) and nonmethane volatile organic compounds (NMVOC) result from the incomplete combustion of fuels. The IPCC
Guidelines cover emissions of stationary combustion-related non-CO2 greenhouse gases from five sectors(Energy and Manufacturing Industries, the Commercial/Institutional Sector, the Residential Sector andAgriculture/Forestry/Fishing sources). This section addresses only emissions of the direct greenhouse gases CH4
and N2O.
Fuel characteristics (including the calorific value), the type of technology (including the combustion, operating
and maintenance regime, the size and the vintage of the equipment), and emission controls, are major factors
determining rates of emissions of CH4 and N2O gases from stationary sources. Moisture content, carbon fraction,and combustion efficiencies are also important factors to consider.

2.2.1.1

C HOICE OF METHODThe IPCC Guidelines describe the following general approach to estimate emissions from fuel combustion foreach greenhouse gas and sub-source category:
EQUATION 2.3
Emissions =∑ (Emission Factorabc • Fuel Consumptionabc)

Where:
a = fuel typeb = sector activity
c = technology type

Given the dependence of emissions on unique combustion conditions and other characteristics, good practice isto disaggregate fuel consumption into smaller, more homogeneous categories, if data and specific emission
factors are available. The IPCC Guidelines generally refer to such disaggregated estimation methods using
country-specific emission factors as Tier 2, and more aggregated estimates as Tier 1 calculations. Good practiceis to use the level of disaggregation that reflects the greatest level of detail in the energy statistics available in the
country.
Figure 2.3, Decision Tree for Non-CO2 Emissions from Stationary Combustion summarises good practice inmethodological choice. It should be applied separately to each of the sub-source categories for each gas forwhich emissions exist in a country, because the availability of activity data and emission factors (and hence theoutcome in terms of methodological choice) may differ significantly between sub-source categories.
Although continuous measurement of emissions is also consistent with good practice, continuous measurementsof CH4 and N2O alone are not justified because of their comparatively high cost and because practical continuous
monitoring systems are not easily available. Sufficiently accurate results may be obtained by using periodic
measurements for CH4 and N2O. These measurements would help to improve emission factors. If monitors are
already installed to measure other pollutants, they may deliver some useful parameters such as fluxes.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.37

Energy

Chapter 2

Figure 2.3

Decision Tree for Non-CO2 Emissions from Stationary
Combustion

Box 5
Are
direct emissions
measurements
available?

Yes

Estimate emissions
using measured data

No
Are
fuel consumption
data available fortechnology
types?

Is thisa key source
category?
(Note 1)

No

Yes

No

Collect or estimate
energy statistics on an
aggregated fuel andsource sector level

Yes
Box 1
Obtain activity data
and disaggregate bytechnology typeCalculate emissions
using IPCC default
Tier 1 emission factors

Box 2
Are
country-specificemission factors
available?

No

Are
regional emission
factors
available?

Yes
Box 4

No

Calculate emissions
using IPCC default
Tier 2 emission factors

Yes
Box 3

Calculate emissions
using Tier 2 nationalemission factors

Calculate emissions
using Tier 2 regionalemission factors

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)
Note 2: The decision tree and key source category determination should be applied to methane and nitrous oxide emissions separately.

2.38

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyProper use of the decision tree requires an inventory agency to undertake, beforehand, a thorough survey ofavailable national activity data and national or regional emission factor data, by relevant source category. For
some sub-source categories, activity and emissions data may be sparse. In this case, it is good practice toimprove data quality if an initial calculation with a default method indicates a significant contribution to total
national emissions or the presence of a high level of uncertainty.
Where direct measurements are available, reporting of implied emission factors cross referenced by technology
type would be helpful, since this information could help others to estimate national emissions.

2.2.1.2

C HOICE OF EMISSION FACTORSGood practice is to use the most disaggregated technology-specific and country-specific emission factors
available, particularly those derived from direct measurements at the different stationary combustion sources.
Using the Tier 2 approach, there are three possible types of emission factors:•

National emission factors.9 These emission factors may be developed by national programmes alreadymeasuring emissions of indirect greenhouse gases such as NOx, CO and NMVOC for local air quality;•

Regional emission factors;10•

IPCC default emission factors, provided that a careful review of the consistency of these factors with thecountry conditions has been made. IPCC default factors may be used when no other information is available.

If national activity data are not sufficiently disaggregated to enable the use of Tier 2, then aggregate Tier 1
emission factors should be applied, provided that no other referenced data are available that are more
representative of combustion conditions within the country.
Emission factors for biomass fuels are not as well developed as those for fossil fuels. Preliminary results from aninternational biomass emission factor research project, focusing on developing countries (e.g. India, Kenya, andChina) show emission factors for small biomass devices and carbonisation that are different from the IPCC
defaults. Given the importance of biomass in many countries, it is suggested that country experts consider the
new well-researched emission factors as soon as they are published (Smith et al., 1993; Smith et al., 1999; Smithet al., 2000; Zhang et al., 1999; Zhang et al., 2000).

2.2.1.3

C HOICE OF ACTIVITY DATA

Due to the technology-specific nature of non-CO2 formation, detailed fuel combustion technology statistics areneeded in order to provide rigorous emission estimates. It is good practice to collect activity data in units of fuelused, and to disaggregate as far as possible into the share of fuel used by major technology types. Disaggregation
can be achieved through a bottom-up survey of fuel consumption and combustion technology, or through topdown allocations based on expert judgement and statistical sampling. Specialised statistical offices or ministerial
departments are generally in charge of regular data collection and handling. Inclusion of representatives fromthese departments in the inventory process could facilitate the acquisition of appropriate activity data.
Good practice for electricity autoproduction (self-generation) is to assign emissions to the source categories (orsub-source categories) where they were generated and to identify them separately from those associated withother end-uses such as process heat. In many countries, the statistics related to autoproduction are available andregularly updated. Therefore, activity data do not represent a serious obstacle to estimating non-CO2 emissions in
those countries.
For some source categories (e.g. energy use in agriculture), there may be some difficulties in separating fuel usedin stationary equipment from fuel used in mobile machinery. Given the different emission factors of these twosources, good practice is to derive the energy use of each of these sources by using indirect data (e.g. number ofpumps, average consumption, and needs for water pumping). Expert judgement and information available fromother countries may also be relevant.

9 Since the associated uncertainty ranges are dependent on the instrumentation used and on the frequency of measurements,

these should be described and reported.
10 The sources of the regional emission factors should be documented and the uncertainty ranges reported.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.39

Energy

Chapter 2

2.2.1.4

C OMPLETENESS

Completeness should be established by cross-referencing to the source categories used for reporting CO2
emissions from stationary combustion. The same source categories should be used in cases where choice ispossible (e.g. emissions from coke used in blast furnaces that can be reported either with industrial emissions orunder stationary combustion depending on national circumstances as explained in Section 2.1.1.3 and below).
Cross-referencing with CO2 categories will not necessarily cover non-CO2 emissions from biomass fuels, since
CO2 emissions from biomass fuels are reported as memo items but not included in national totals. Therefore, thenational energy statistics agencies should be consulted about use of biomass fuels, including possible use of noncommercially traded biomass fuels. Biomass related issues are particularly important for the quality of
inventories in developing countries. A major effort is required by country experts in order to improve related
non-CO2 estimates.
The reporting of emissions from coke use in blast furnaces requires attention. Crude iron is typically produced by
the reduction of iron oxide ores in a blast furnace, using the carbon in coke (sometimes other fuels) as both thefuel and reductant. Since the primary purpose of coke oxidation is to produce pig iron, the emissions should beconsidered as coming from an industrial process if a detailed calculation of industrial emissions is being
undertaken. It is important not to double-count the carbon from the combustion of coke. Therefore, if theseemissions have been included in the Industrial Processes sector, they should not be included in the Energy sector.
However, there are countries where industrial emissions are not addressed in detail. In these instances, theemissions should be included with Energy. Good practice is to state clearly whether non-CO2 emissions fromcoke use in blast furnaces have been allocated to Energy or to Industrial Processes, to indicate that no double
counting has occurred.
Uncontrolled situations that might affect estimates and sectoral distribution (e.g. statistical differences or thefts)
require special consideration. Inventory agencies are encouraged to make the most appropriate interpretation of
the related emissions.

2.2.1.5

D EVELOPING A CONSISTENT TIME SERIESAs improved emission factors and emission estimation methods are developed over time, base year emission
estimates determination will be an important issue for non-CO2 emissions from stationary combustion. Good
practice guidance on ensuring time series consistency and base year determination is provided in Chapter 7,
Methodological Choice and Recalculation, Section 7.3.2.2, Alternative Recalculation Techniques.
Many countries, particularly developing ones, do not undertake annual surveys. Where data are missing for an
inventory year, it may be necessary to estimate activity data through extrapolation for the current year orinterpolation between years. These extrapolations or interpolations require regular cross-checking with survey
data collected at least every three to five years. Chapter 7, Methodological Choice and Recalculation, Section
7.3.2.2, Alternative Recalculation Techniques, describes in more detail methods for making such calculations.
Biomass data may be incomplete, particularly for small combustion devices. If the data are missing for theinventory year, inventory agencies could extrapolate to the relevant year based on past trends, or interpolate,again using the methods described in Chapter 7.11 Additional cross-checking should be done to ensure theconsistency of the estimates with related data that are available annually (e.g. wood production potential fromforests, and annual dung production).

2.2.1.6

U NCERTAINTY ASSESSMENT

Default uncertainty ranges for non-CO2 stationary combustion emissions are not provided in the IPCC
Guidelines. It is good practice to quantify the uncertainties associated with the inventory results regardless of thetier adopted.

11 Two recent meetings at the IEA addressed the issues of gathering and modelling biomass energy data. The findings are
published in (i) Biomass Energy: Key Issues and Priority Needs. Conference Proceedings. IEA/OECD, Paris, France. 3-5
February 1997; (ii) Biomass Energy: Data, Analysis and Trends. Conference Proceedings. IEA/OECD, Paris, France. 23-24
March 1998.

2.40

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyEMISSION FACTOR UNCERTAINTIESThe default uncertainties shown in Table 2.5, derived from the EMEP/CORINAIR Guidebook ratings(EMEP/CORINAIR, 1999), may be used in the absence of country-specific estimates.
TABLE 2.5
DEFAULT UNCERTAINTY ESTIMATES FOR STATIONARY COMBUSTION EMISSION FACTORS
SectorCH4

N2O

Public Power, co-generation and district heating

50-150%Order of magnitudea

Commercial, Institutional & Residential combustion

50-150%Order of magnitude

Industrial combustion

50-150%Order of magnitude

Agriculture/forestry/fishing

Not reported

Not reportedaI.e. having an uncertainty range from one-tenth of the mean value to ten times the mean value.

Source: Judgement by Expert Group (see Co-chairs, Editors and Experts; Stationary Combustion).

While these default uncertainties can be used for the existing emission factors (whether country-specific or takenfrom the IPCC Guidelines), there may be an additional uncertainty associated with applying emission factors thatare not representative of the combustion conditions in the country. It is good practice to obtain estimates of these
uncertainties from national experts taking into account the guidance concerning expert judgements provided in
Chapter 6, Quantifying Uncertainties in Practice.

ACTIVITY DATA UNCERTAINTIESAggregate data related to energy consumption by fuel type are generally estimated accurately. There is more
uncertainty for biomass and traditional fuels. Uncertainties associated with sectoral (or sub-sectoral) distributionof fuel use are also generally higher, and will vary with the approach (survey or extrapolation) used and thespecificity of the country’s statistical systems.
The activity data uncertainty ranges shown in Table 2.6, Level of Uncertainty Associated with Stationary
Combustion Activity Data, may be used when reporting uncertainties. It is good practice for inventory agencies
to develop, if possible, country-specific uncertainties using expert judgement or statistical analysis.

TABLE 2.6
LEVEL OF UNCERTAINTY ASSOCIATED WITH STATIONARY COMBUSTION ACTIVITY DATA
Well Developed Statistical Systems
SectorLess Developed Statistical Systems

Surveys

Extrapolations

Surveys

Extrapolations

less than 1%

3-5%

1-2%

5-10%

Commercial, institutional,
residential combustion

3-5%

5-10%

10-15%

15-25%

Industrial combustion(Energy intensive industries)

2-3%

3-5%

2-3%

5-10%

Industrial combustion (others)

3-5%

5-10%

10-15%

15-20%

Biomass in small sources

10-30%

20-40%

30-60%

60-100%Public Power, co-generation anddistrict heating

The inventory agency should judge which type of statistical system best describes their national circumstances.
Source: Judgement by Expert Group (see Co-chairs, Editors and Experts; Stationary Combustion).

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.41

Energy

Chapter 2

2.2.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and the steps in their calculation may be retraced.
The current IPCC reporting format (spreadsheet tables, aggregate tables) provides a balance between thetransparency requirement and the level of effort that is realistically achievable by the inventory agency. Good
practice involves some additional effort to fulfil the transparency requirements completely. In particular, if Tier 2(or a more disaggregated approach) is used, additional tables showing the activity data that are directly associatedwith the emission factors should be prepared.
Most energy statistics are not considered confidential. If inventory agencies do not report disaggregated data due
to confidentiality concerns, it is good practice to explain the reasons for these concerns, and report the data in amore aggregated form.
For a highly disaggregated stationary non-CO2 estimate, it may be necessary to cite many different references ordocuments. It is good practice to provide citations for these references, particularly if they describe new
methodological developments or emission factors for particular technologies or national circumstances.
It is good practice to state clearly whether non-CO2 emissions from coke (or other fuels) used in crude ironproduction have been allocated to the Energy or to the Industrial Processes Sector, to show that no double
counting has occurred. The attribution of emissions from blast furnaces and other industrial processes should beconsistent between CO2 and non-CO2 emissions (see Section 2.1.1.4).

2.2.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Comparison of emission estima tes using different approaches•

If a Tier 2 approach with country-specific factors is used, the inventory agency should compare the result toemissions calculated using the Tier 1 approach with default IPCC factors. This type of comparison may
require aggregating Tier 2 emissions to the same sector and fuel groupings as the Tier 1 approach. The
approach should be documented and any discrepancies investigated.

•

If possible, the inventory agency should compare the consistency of the calculations in relation to the
maximum carbon content of fuels that are combusted by stationary sources. Anticipated carbon balances
should be maintained throughout the combustion sectors, and the non-CO2 estimates should not contradict
maximum theoretical quantities based on the total carbon content of the fuels.

Rev ie w o f e missio n f a c t o r s•

If country-specific emission factors are used, the inventory agency should compare them to the IPCC
defaults, and explain and document differences.

•

The inventory agency should compare the emission factors used with site or plant level factors, if these areavailable. This type of comparison provides an indication of how reasonable and representative the national
factor is.

2.42

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyReview of direct measurements•

If direct measurements are used, the inventory agency should ensure that they are made according to goodmeasurement practices including appropriate QA/QC procedures. Direct measurements should be comparedto the results derived from using IPCC default factors.

Activity da ta check•

The inventory agency should compare energy statistics with those provided to international organisations to
identify any inconsistencies that require explanation.

•

If secondary data from national organisations are used, the inventory agency should ensure that theseorganisations have appropriate QA/QC programmes in place.

External review•

The inventory agency should carry out a review involving national experts and stakeholders in the different
fields related to emissions from stationary sources, such as: energy statistics, combustion efficiencies fordifferent sectors and equipment types, fuel use and pollution controls. In developing countries, expert review
of emissions from biomass combustion is particularly important.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

2.43

Energy

Chapter 2

2.3

MOBILE COMBUSTION: ROAD VEHICLES

2.3.1

Methodological issues

Road transport emits significant amounts of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as
well as several other pollutants such as carbon monoxide (CO), non-methane volatile organic compounds(NMVOCs), sulfur dioxide (SO2), particulate matter (PM) and oxides of nitrate (NOx), which cause or contributeto local or regional air pollution problems. This chapter covers good practice in the development of estimates forthe direct greenhouse gases CO2, CH4 and N2O.

2.3.1.1

C HOICE OF METHOD

Emissions of CO2 are best calculated on the basis of the amount and type of fuel combusted and its carbon
content. Emissions of CH4 and N2O are more complicated to estimate accurately because emission factors depend
on vehicle technology, fuel and operating characteristics. Both distance-based activity data (e.g. vehiclekilometers travelled) and disaggregated fuel consumption may be considerably less certain than overall fuelconsumption.
Figure 2.4, Decision Tree for CO2 Emissions from Road Vehicles and Figure 2.5, Decision Tree for CH4 andN2O Emissions from Road Vehicles outline the process to calculate emissions from the Transport Sector. Two
alternative approaches can be used, one based on vehicle kilometres travelled and the other based on fuelconsumption. The inventory agency should choose the method on the basis of the existence and quality of data.
Models can help ensure consistency and transparency because the calculation procedures are fixed in thesoftware. It is good practice to clearly document any modifications to standardised models.
Figure 2.4

Decision Tree for CO2 Emissions from Road Vehicles

Areroad transport
fuel combustion data
available?

No

Collect
fuel use
data

Yes

Box 1
Are
country-specificemission factors
available?

No

Estimate emissions
by using default
emission factors

Yes
Box 2
Estimate emissions byusing country-specificemission factors

2.44

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

EnergyFigure 2.5

Decision Tree for CH4 and N2O Emissions from Road
VehiclesIs
there awell-documented
national
method?

Box 1
Yes

Estimateemissions using
national method

No
Are
fuel data
available by fueland vehicle
type?

Box 2
No

Is this a
key source
category?
(Note 1)

Yes

Yes

Allocate
consumption ofeach fuel type todifferent vehicle

Collect
information on
fuel consumption
and vehicle types

Are pollution
control technology data
available for eachvehicle type?

No

No

Estimate emissions byusing theTier 1 method

Collect information on the typeof pollution control technologies
used and estimate percentage intotal fleet

Yes

Is it
possible to estimate
vehicle km travelled bytechnology
type?

No

Is it
possible to estimate
fuel consumption bytechnology
type?

Yes

Apportion fuel use tocontrol technologies using
vehicle registration
numbers
Yes

Yes
Box 4

Allocate consumptionof each fuel type todifferent vehicle
control technologies

No

Estimate emissions
using fuel-based
emission factors

Box 3
Estimate emissions
using fuel-based
emission factors

Box 5
Estimate emissions using vehicle
km based emission factors(e.g. COPERT, MOBILE)(Tier 3)Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.). Note 2: The decision tree and key source category determination should be applied to methane and nitrous oxide emissions separately.

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Energy

Chapter 2

CO 2 EMISSIONSThe IPCC Guidelines provide two methods to estimate CO2 emissions from Road Transport. The Tier 1, or ‘top
down’ approach calculates CO2 emissions by estimating fuel consumption in a common energy unit, multiplying
by an emission factor to compute carbon content, computing the carbon stored, correcting for unoxidised carbon
and finally converting oxidised carbon to CO2 emissions. The approach is shown in Equation 2.4.
EQUATION 2.4

Emissions =Σj [(Emission Factor j • Fuel consumedj) – Carbon Stored]• Fraction Oxidisedj • 44/12

Where j = fuel type

Alternatively, a Tier 2, or ‘bottom-up’ approach estimates emissions in two steps. The first step (Equation 2.5) is
to estimate fuel consumed by vehicle type i and fuel type j.
EQUATION 2.5

Fuel Consumptionij = nij • kij • eij
Where:
i = vehicle typej = fuel typen = number of vehicles
k = annual kilometres travelled per vehiclee = average litres consumed per kilometre travelled

The second step is to estimate total CO2 emissions by multiplying fuel consumption by an appropriate emission
factor for the fuel type and vehicle type (Equation 2.6).
EQUATION 2.6
Emissions =ΣiΣj (Emission Factorij • Fuel Consumptionij)

It is good practice to calculate CO2 emissions on the basis of fuel consumption statistics using the Tier 1 (topdown) approach. This is illustrated in the decision tree in Figure 2.4, Decision Tree for CO2 Emissions from
Road Vehicles. Except in rare cases (e.g. where there is extensive fuel smuggling), the top-down approach ismore reliable for CO2 estimates and is also much simpler to implement. The main issue is to ensure that double
counting of agricultural and off-road vehicles is avoided.
It is also good practice to use the Tier 2 (bottom up) approach in parallel for the following reasons:•First, use of these two approaches provides an important quality check. Significant differences between the
results of the top-down and bottom-up approaches indicate that one or both approaches may have errors, andthere is a need for further analysis. Areas of investigation to pursue when reconciling top down and bottomup approaches are listed in Section 2.3.3, Inventory quality assurance/quality control (QA/QC).

•

Second, a reliable and accurate bottom-up CO2 emissions estimate increases confidence in the underlying
activity data used for the bottom-up inventory. These in turn are important underpinnings for the ‘bottom-up’
calculation of CH4 and N2O emissions from road transport.

When calculating emissions using both the top-down and bottom-up approaches in parallel, it is good practice,where feasible, to develop the bottom-up estimates independently from the top-down estimates.

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Chapter 2

EnergyCH 4 AND N 2 O EMISSIONS
CH4 and N2O emissions depend primarily on the distribution of emission controls in the fleet. Good practice is touse a bottom-up approach taking into account the various emission factors for different pollution control
technologies. This approach should be applied if this is a key source category, as defined in Chapter 7,
Methodological Choice and Recalculation.

2.3.1.2

C HOICE OF EMISSION FACTORSIn the IPCC Guidelines, CO2 emission factors are developed on the basis of the carbon content of the fuel. It isgood practice to follow this approach using country-specific data if possible. Default emission factors provided
in the IPCC Guidelines may be used if there are no locally available data.
Developing emission factors for CH4 and N2O is more difficult because these pollutants require technology-based
emission factors rather than aggregate default emission factors. It is good practice to calculate an emission factor
for each fuel type and vehicle type (e.g. passenger cars, light trucks, heavy trucks, motorcycles) based on thelocal mix of engine types and the distribution of installed control technologies. Further refinements in the factors
can then be made if additional local data (e.g. on average driving speeds, temperatures, altitude, pollution control
devices) are available. It is good practice to document the basis for the data.
Recently published data indicate that the default emission factors in the IPCC Guidelines for US gasoline
vehicles should be updated.12 Based on this test data, the N2O emission factors in the IPCC Guidelines for US
vehicles (Tables I-27, Estimated Emission Factors for US Gasoline Passenger Cars to Table I-33, EstimatedEmission Factors for US Motorcycles in the Reference Manual) should be replaced by the tables below.
TABLE 2.7
UPDATED EMISSION FACTORS FOR USA GASOLINE VEHICLESEmission Factor
Control Technology(g N2O/kg fuel)(g N2O/MJ)

Low Emission Vehicle (low sulfur fuel)0.20

0.0045Three-Way Catalyst (USA Tier 1)

0.32

0.0073

Early Three-Way Catalyst (USA Tier 0)

0.54

0.012

Oxidation Catalyst

0.27

0.0061

Non-Catalyst Control

0.062

0.0014

Uncontrolled

0.065

0.0015

Source: Harvey Michael, (1999), US Environmental Protection Agency. Personal communication to Michael Walsh.
Notes:
Tier 0 and Tier 1 in this table refer to tiers used in the USA methodology, not to the IPCC tiers. These data have been rounded to two
significant digits.
A database of technology dependent emission factors based on European data is available in the Copert tool at
http://etc-ae.eionet.eu.int/etc-ae/index.htm.
To convert to g/km, multiply emission factor (g/kg) by the fuel density in kg/l and then divide by fuel economy in km/l. For example, if
the emission factor is 0.32 g/kg, fuel density is 0.75 kg/l and fuel economy is 10 km/l, then the emission factor in g/km is(0.32 g/kg • 0.75 kg/l) / 10 km/l = 0.024 g/km.
In the IPCC Guidelines, Tables 1-37, Estimated Emission Factors for European Diesel Passenger Cars, to Table 1-39, EstimatedEmission Factors for European Diesel Heavy-duty Vehicles, list N2O emission factors for European diesels of 0.01, 0.02, and 0.03 g/km
for cars, light trucks, and heavy duty vehicles respectively. These factors are order of magnitude estimates roughly following fueleconomy differences. Emission factors from other countries may differ from the data provided in Table 2.7. The average value 0.172
g/kg is recommended for all USA diesel vehicles regardless of control technology. This corresponds to 0.0039 g/MJ, assuming 44
MJ/kg.

12 In order to refine the N O emission factors, the USEPA Office of Mobile Sources carried out an evaluation of available

2

data supplemented by limited testing in June and July 1998. They determined emission factors for Early Three-Way Catalyst
and previous vehicles primarily from the published literature. For (advanced) Three-Way Catalyst vehicles and LowEmission Vehicle Technology, data were used from the testing program. USEPA also assessed the limited data that exist fortrucks.

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Chapter 2

2.3.1.3

C HOICE OF ACTIVITY DATA

The first step in estimating CO2 emissions using the top-down approach is to determine total fuel use in thetransportation sector by major fuel type. These data should be available from national energy statistics. Following
this, several issues must be addressed, including:•

Provision of data for fuels with minor distribution such as compressed natural gas or biofuels. These data
should also be available from the national authority responsible for the energy statistics. According to the
IPCC Guidelines, CO2 emissions from biofuels are reported as memo items but not included in national
totals. Non-CO2 emissions from biofuels should be included in national totals.

•

Provision of data to distinguish between fuel use for on-road vehicles from fuel use for off-road vehicles,
which are reported in different source categories in the IPCC Guidelines. Two alternatives are suggested:(i)A bottom-up calculation of fuel used by each road vehicle type. The difference between the roadvehicle total (bottom-up) and the total transportation fuel used is ascribed to the off-road sector; or(ii)

The bottom-up calculation of fuel used by each road type is supplemented by special studies todetermine off-road fuel use. The total fuel use in the transportation sector (top-down estimate) isthen disaggregated according to each vehicle type and the off-road sector in proportion to thebottom-up estimates.

•

Data for fuel that is sold for transportation uses but which then may be used for other purposes (or the
opposite).

•

Estimates of smuggling of fuels into or out of a country.

Some inventory agencies have or will have greater confidence in vehicle fuel consumption data by vehicle type
and technology while others prefer vehicle kilometres. Either approach is acceptable so long as the basis for theestimates is clearly documented.
If non-CO2 emissions from mobile sources are a key source category, more information is needed on factors that
influence emissions such as:•

Vehicle type (cars, light duty trucks, heavy duty trucks and motorcycles) distribution in fleet;•

Emission control technologies fitted to vehicle types in the fleet;•

Fleet age distribution;•

Climate;•Altitude of operation;•

Maintenance effects.

If the distribution of fuel use by vehicle and fuel type is unknown, it should be estimated based on the number ofvehicles by type. If the number of vehicles by vehicle and fuel type is not known, it must be estimated fromnational statistics. If local data on annual kilometres travelled per vehicle and average fuel economies by vehicle
and fuel type are available, they should be used.

2.3.1.4

C OMPLETENESS

Lubricants should be accounted for in other emissions categories, as very little is combusted directly in thetransportation sector.
Regarding the problem of purchase and consumption of fuels in different countries (i.e. fuel in tanks that arecrossing a border) and the question of allocation, the IPCC Guidelines state: ‘Emissions from road vehicles
should be attributed to the country where the fuel is loaded into the vehicle.’
Oxygenates and other blending agents should be carefully accounted for in making CO2 estimates, if used in large
quantities. It is important that all fossil carbon is accounted for, and that carbon from biomass is reported as amemo item but not included in national CO2 totals, as required by the IPCC Guidelines.

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Chapter 2

2.3.1.5

EnergyD EVELOPING A CONSISTENT TIME SERIESWith the use of models and updates or revisions of models, it is important that time series remain consistent.
When models are revised, it is good practice to recalculate the complete time series. A consistent time series withregard to initial collection of fleet technology data could be difficult. Extrapolation, possibly supported by the useof proxy data will be necessary in this case for early years. Inventory agencies should refer to the discussion
Chapter 7, Methodological Choice and Recalculation, Section 7.3.2.2, Alternative Recalculation Techniques forgeneral guidance.

2.3.1.6

U NCERTAINTY ASSESSMENT

Carbon dioxide is usually responsible for over 97% of the CO2-equivalent emissions from the transportation
sector.13 Expert judgement suggests that the uncertainty of the CO2 estimate is approximately ±5%, based onstudies with reliable fuel statistics.14 The primary source of uncertainty is the activity data rather than emission
factors.
Nitrous oxide usually contributes approximately 3% to the CO2-equivalent emissions from the transportation
sector. Expert judgement suggests that the uncertainty of the N2O estimate may be more than ±50%.The major
source of uncertainty is related to the emission factors.
Methane usually contributes less than 1% of the CO2-equivalent emissions from the transportation sector. Experts
believe that there is an uncertainty of ±40% in the CH4 estimate. The major source of uncertainty is again
emission factors.
To reduce uncertainty, a comprehensive approach is needed that reduces uncertainties of emission factors as wellas activity data, especially with regard to the bottom-up approach. By encouraging the use of locally estimateddata, inventories will improve despite the large uncertainties that may surround national data.
Chapter 6, Quantifying Uncertainties in Practice, describes how to use national empirical data and expert
judgement to estimate uncertainties, and how to combine uncertainty estimates for the inventory as a whole.

2.3.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
Confidentiality is not likely to be a major issue with regard to road emissions, although it is noted that in somecountries the military use of fuel may be kept confidential. The composition of some additives is confidential, but
this is only important if it influences greenhouse gas emissions.

2.3.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.

13 According to 1990 data for Annex I countries in the UNFCCC secretariat’s database on GHG emissions, updated

September 1999.
14 The percentages cited in this section represent an informal polling of assembled experts aiming to approximate the 95%
confidence interval around the central estimate.

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Energy

Chapter 2

In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Co mpa r iso n o f e missio ns using a lt e r na t iv e a ppro a c hes
For CO2 emissions, the inventory agency should compare estimates using both the top-down and bottom-up
approaches. Any anomalies between the emission estimates should be investigated and explained. The results ofsuch comparisons should be recorded for internal documentation. Revising the following assumptions could
narrow a detected gap between the approaches:•

Off-road/non transportation fuel uses;•

Annual average vehicle mileage;•

Vehicle fuel efficiency;•

Vehicle breakdowns by type, technology, age, etc.;•

Use of oxygenates/biofuels/other additives;•

Fuel use statistics;•

Fuel sold/used.

Rev ie w o f e missio n f a c t o r s
If IPCC default factors are used, the inventory agency should ensure that they are applicable and relevant to thecategories. If possible, the IPCC default factors should be compared to local data to provide further indicationthat the factors are applicable.
For non-CO2 emissions, the inventory agency should ensure that the original data source for the local factors isapplicable to the category and that accuracy checks on data acquisition and calculations have been performed.
Where possible, the IPCC default factors and the local factors should be compared. If the IPCC default factors
were used to estimate N2O emissions, the inventory agency should ensure that the revised emission factors in
Table 2.7, Updated Emission Factors for USA Gasoline Vehicles were used in the calculation.
Activity da ta check
The inventory agency should review the source of the activity data to ensure applicability and relevance to thecategory. Where possible, the inventory agency should compare the data to historical activity data or model
outputs to look for anomalies. The inventory agency should ensure the reliability of activity data regarding fuelswith minor distribution, fuel used for other purposes, on and off-road traffic, and illegal transport of fuel in or outof the country. The inventory agency should also avoid double counting of agricultural and off-road vehicles.
External review
The inventory agency should perform an independent, objective review of the calculations, assumptions, anddocumentation of the emissions inventory to assess the effectiveness of the QC programme. The peer review
should be performed by expert(s) who are familiar with the source category and who understand the inventory
requirements. The development of the factors for the non-CO2 emission estimates is particularly important due tothe associated uncertainty.

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Chapter 2

Energy2.4

MOBILE COMBUSTION: WATER-BORNENAVIGATION

2.4.1

Methodological issues

This source category includes all emissions from fuels used to propel water-borne vessels, including hovercraft
and hydrofoils. Water-borne navigation gives rise to emissions of carbon dioxide (CO2), methane (CH4) andnitrous oxide (N2O), as well as carbon monoxide (CO), non-methane volatile organic compounds (NMVOC),
sulfur dioxide (SO2), particulate matter (PM) and oxides of nitrate (NOx). This section focuses on the direct
greenhouse gases CO2, CH4, and N2O.
Parties to the UNFCCC have not made a final decision yet on the allocation to national GHG inventories ofemissions from fuels used for international aviation and from international marine bunkers. For the moment, allemissions from these fuels are to be excluded from national totals, and are to be reported separately.

2.4.1.1

C HOICE OF METHODThe IPCC Guidelines present two methodological tiers for estimating emissions of CO2, CH4, and N2O fromwater-borne navigation. Both Tier 1 and Tier 2 rely on essentially the same analytical approach which is to apply
emission factors to fuel consumption activity data. The fuel consumption data and emission factors in the Tier 1
method are fuel type and mode-specific (e.g. oil used for navigation). The Tier 2 method presents a variety ofemission factors based on research in the United States and Europe, requiring varying degrees of specificity inthe classification of modes (e.g. ocean-going ships and boats), fuel type (e.g. gasoline), and even engine type(e.g. diesel). Figure 2.6, Decision Tree for Emissions from Water-borne Navigation helps in making a choice
between the two tiers.
Good practice is to use Tier 1 for CO2, and Tier 2 for CH4 and N2O. Tier 1 for CO2 emissions is based on fuelconsumption by fuel type, the carbon content of the fuel, and the fraction of the fuel left unoxidised. Tier 2 for
non-CO2 emissions also uses fuel consumption by fuel type, but provides a variety of generic and countryspecific emission factors for selected fuel, engine, and vehicle types. National approaches may also be goodpractice if they are well documented and have been peer reviewed.
Until the uncertainties in the CH4 and N2O emission factors are reduced, more detailed methods will notnecessarily reduce uncertainties in the emission estimates. Despite this limited reduction in uncertainty, however,these methods are likely to be desirable in the longer term for a number of other reasons. One reason is toharmonise with other emission inventory efforts that are more detailed. More detailed methods are also better
able to account for changes in technologies and therefore emission factors in the future. If improved enginespecific and fuel-specific emission factors become available, a historic database of disaggregated fuel use willallow the backcasting of a trend to the base year.

MILITARY
The IPCC Guidelines do not provide a distinct method for calculating military marine emissions. Emissions frommilitary marine fuel use can be estimated using the same ‘hybrid’ approach recommended for non-military
shipping (i.e. Tier 1 approach for CO2, Tier 2 approach for CH4 and N2O). However, military marine navigation
may include unique operations, situations, and technologies without a civilian analogue (e.g. aircraft carriers,
very large auxiliary power plants, and unique engine types). Therefore, inventory agencies should consult
military experts to determine the most appropriate emission factors.

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Energy

Chapter 2

Figure 2.6

Decision Tree for Emissions from Water-borne
Navigation

Are
fuel consumption
data available by fuel typefor water-borne
navigation?

Collect data or
estimate using
proxy data

No

Yes

Have
the data been
allocated between
international anddomestic?

No

Develop allocation
based on otherinformation orproxy data

Yes
Box 1
Are
national carbon
content data and CH4 andN2O emission factors
available?

No

Is this a
key source
category?
(Note 1)

No

Estimate CO2 emissions
using IPCC default
carbon contents; estimate
CH4 and N2O emissions
using IPCC default
emission factors

Yes

Yes

Initiate datacollection

Box 2
Is
fuel-use databy engine typeavailable?

No

Use Tier 1 with country specificcarbon contents for CO2 and
IPCC default emission factors
for CH4 and N2O

Yes
Box 3
Estimate emissions using
Tier 2 with country specificcarbon content factors andengine specific CH4 andN2O emission factors

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 2

2.4.1.2

EnergyC HOICE OF EMISSION FACTORS

Carbon dioxide emission factors are based on the fuel type and carbon content as well as the fraction of fuel left
unoxidised. It is good practice to use national carbon content and fraction oxidised factors for CO2 whenavailable. Default values can also be used when no other information is available (IPCC Guidelines, Workbook,
Table 1-2, Carbon Emission Factors and Table 1-4, Fraction of Carbon Oxidised).
There is limited information on the emission factors for CH4 and N2O from marine shipping. The IPCC
Guidelines provide factors for the USA and the EU as well as factors developed by Lloyd’s Register (Table
1-47, Estimated Emission Factors for US Non-road Mobile Sources to Table 1-49, Estimated Emission Factors
for European Non-road Mobile Sources and Machinery, Reference Manual). Large ocean-going cargo ships are
driven primarily by large, slow speed and medium speed diesel engines and occasionally by steam and gas
turbines. For CH4 and N2O emissions from large marine diesel engines consuming distillate or residual fuel oils,
it is good practice to use the factors developed by Lloyd’s Register. These factors are based on the most recent
and extensive set of test data. As marine shipping engines are predominantly diesel, and do not vary by country,
national emission factors are not likely to yield improved emission estimates unless they are based on peer
reviewed studies. For other vessels, such as recreational craft on inland waterways, national emission factors
should be used if available. Alternatively, the IPCC default factors from Lloyds, the USA or the EU can be used.
The difference in emission rates illustrates the importance of characterising fleet engine types and fuel use forregional scale emissions.

MILITARY
Currently, emission factors for N2O and CH4 for military vessels are not available. The default emission factors
for civilian shipping should be used unless national data are available of sufficient quality, taking into account theadvice in Chapter 8, Quality Assurance and Quality Control.

2.4.1.3

C HOICE OF ACTIVITY DATA

Data on fuel consumption by fuel type and (for N2O and CH4) engine type are required to estimate emissions. In
addition, in the current reporting procedures, emissions from domestic water-borne navigation are reported
separately from international navigation which requires disaggregating the activity data to this level. For
consistency, it is good practice to use similar definitions of domestic and international activities in the aviation
and water-borne navigation estimates. These definitions are presented in Table 2.8, Criteria for Defining
International or Domestic Marine Transport, and are consistent with the IPCC Guidelines. They are more
precise, however, in order to make them workable with respect to the sources of activity data. The definitions inTable 2.8 are independent of the nationality or flag of the carrier.
TABLE 2.8
CRITERIA FOR DEFINING INTERNATIONAL OR DOMESTIC MARINE TRANSPORT
Journey Type

Domestic

International

Originates and terminates in same country

Yes

No

Departs from one country and arrives in another

No

Yes

Departs in one country, makes a ‘technical’ stop in the same country
without dropping or picking up any passengers or freight, then departs
again to arrive in another country

No

Yes

Departs in one country, stops in the same country and drops and picks
up passengers or freight, then departs finally arriving in anothercountry

Domestic segment

International segment

Departs in one country, stops in the same country and only picks up
more passengers or freight and then departs finally arriving in anothercountryNo

Yes

Departs in one country with a destination in another country, andmakes an intermediate stop in the destination country where no
passengers or cargo are loaded

No

Both segmentsinternational

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Energy

Chapter 2

Fuel use data may be obtained using several approaches. The most feasible approach will depend on the national
circumstances, but some of the options provide more accurate results than others. Several likely sources of actual
fuel or proxy data are listed below, in order of typically decreasing reliability:•

National energy statistics from energy or statistical agencies;•

Surveys of shipping companies;•

Surveys of fuel suppliers (e.g. quantity of marine fuels delivered to port facilities);•

Surveys of individual port and marine authorities;•

Surveys of fishing companies;•

Equipment counts, especially for small gasoline powered fishing and pleasure craft;•

Import/export records;•

Ship movement data and standard passenger and freight ferry schedules;•

Passenger counts and cargo tonnage data;•

International Maritime Organisation (IMO), engine manufacturers, or Jane's Military Ships Database.

It may be necessary to combine these data sources to get full coverage of shipping activities.

MILITARY
Due to confidentiality issues (see completeness and reporting), many inventory agencies may have difficulty
obtaining data for the quantity of fuel used by the military. Military activity is defined here as those activities
using fuel purchased by or supplied to the military authority of the country. It is good practice to apply the rules
defining civilian national and international operations in navigation to military operations where they arecomparable. Where they are not comparable, decisions on national and international operations should be
explained. Data on military fuel use may be obtained from government military institutions or fuel suppliers. If
data on fuel split are unavailable, all the fuel sold for military activities should be treated as domestic.
According to Decision 2/CP3 of the Conference of the Parties (COP), multilateral operations should not be
included in national totals but reported separately, although there is no clear operational definition of‘multilateral operation’ available at this time.

2.4.1.4

C OMPLETENESS

For water-borne navigation emissions, the methods are based on total fuel use. Since countries generally haveeffective accounting systems to measure total fuel consumption, the largest area of possible incomplete coverageof this source category is likely to be associated with misallocation of navigation emissions in another source
category. For instance, for small watercraft powered by gasoline engines, it may be difficult to obtain complete
fuel use records and some of the emissions may be reported as industrial (when industrial companies use small
watercraft), other off-road mobile or stationary power production. Estimates of water-borne emissions should
include not only fuel for marine shipping, but also for passenger vessels, ferries, recreational watercraft, otherinland watercraft, and other gasoline-fuelled watercraft. Misallocation will not affect completeness of the total
CO2 emissions inventory. It will affect completeness of the total non-CO2 emissions inventory, because non-CO2
emission factors differ between source categories.
Completeness may also be an issue where military data are confidential, unless military fuel use is aggregatedwith another source category.
There are additional challenges in distinguishing between domestic and international emissions. As eachcountry's data sources are unique for this category, it is not possible to formulate a general rule regarding how tomake an assignment in the absence of clear data. Good practice is to specify clearly the assumptions made so thatthe issue of completeness can be evaluated.

2.4.1.5

D EVELOPING A CONSISTENT TIME SERIESFor good practice guidance on determining base year emissions and ensuring consistency in the time series, see
Chapter 7, Methodological Choice and Recalculation, Section 7.3.2.2, Alternative Recalculation Techniques. It isgood practice to determine fuel use using the same method for all years. If this is not possible, data collection
should overlap sufficiently in order to check for consistency in the methods employed.

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Chapter 2

EnergyIf it is not possible to collect activity data for the base year (e.g. 1990), it may be appropriate to extrapolate data
backwards using trends in freight and passenger kilometres, total fuel used or supplied, or import/export records.
Emissions of CH4 and N2O will depend on engine type and technology. Unless technology-specific emission
factors have been developed, it is good practice to use the same fuel-specific set of emission factors for all years.
Mitigation activities resulting in changes in overall fuel consumption will be readily reflected in emission
estimates if actual fuel activity data are collected. Mitigation options that affect emission factors, however, canonly be captured by using engine-specific emission factors, or by developing control technology assumptions.
Changes in emission factors over time should be well documented.

2.4.1.6

U NCERTAINTY ASSESSMENT

ACTIVITY DATA
Much of the uncertainty in emissions estimates is related to the difficulty of distinguishing between domestic andinternational fuel consumption. With complete survey data, the uncertainty may be low, while for estimations orincomplete surveys the uncertainties may be considerable. The uncertainty will vary widely from country tocountry and is difficult to generalise. The use of global data sets may be helpful in this area, and it is expectedthat reporting will improve for this category in the future.

EMISSION FACTORS
Experts believe that CO2 emission factors for fuels are generally well determined within ±5%, as they are
primarily dependent on the carbon content of the fuel.15 The uncertainty for non-CO2 emissions, however, ismuch greater. The uncertainty of the CH4 emission factor may be as a high as a factor of two. The uncertainty of
the N2O emission factor may be an order of magnitude (i.e. a factor of 10).

2.4.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
Some examples of specific documentation and reporting issues relevant to this source category are provided
below.
Emissions related to water-borne navigation are reported in different categories depending on their nature. For
good practice, the categories to use are:•Civilian domestic activities;•

Military domestic activities;•

International bunker fuels;•

Fishing.

The IPCC Guidelines require that emissions from international navigation be reported separately from domestic,
and not be included in the national total.
Emissions related to commercial fishing are not reported under water-borne navigation. These emissions are to bereported under the Agriculture/Forestry/Fishing category in the Energy sector. By definition, all fuel supplied tocommercial fishing activities in the reporting country is considered domestic, and there is no international bunker
fuel category for commercial fishing, regardless of where the fishing occurs.
Military marine emissions should be clearly specified to improve the transparency of national greenhouse gas
inventories.

15 The uncertainty ranges cited in this section represent an informal polling of assembled experts aiming to approximate the
95% confidence interval around the central estimate.

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Chapter 2

In addition to reporting emissions, it is good practice to provide:•

Source of fuel and other data;•

Method used to separate domestic and international navigation;•

Emission factors used and their associated references;•

Analysis of uncertainty or sensitivity of results or both to changes in input data and assumptions.

2.4.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Co mpa r iso n o f e missio ns using a lt e r na t iv e a ppro a c hes
If possible, the inventory agency should compare estimates determined for water-borne navigation using bothTier 1 and Tier 2 approaches. The inventory agency should investigate and explain any anomaly between theemission estimates. The results of such comparisons should be recorded.
Rev ie w o f e missio n f a c t o r s
The inventory agency should ensure that the original data source for national factors is applicable to eachcategory and that accuracy checks on data acquisition and calculations have been performed. For the IPCC
default factors, the inventory agency should ensure that the factors are applicable and relevant to the category. If
possible, the IPCC default factors should be compared to national factors to provide further indication that thefactors are applicable and reasonable.
If emissions from military use were developed using data other than default factors, the inventory agency should
check the accuracy of the calculations and the applicability and relevance of the data.
Che c k o f a c t iv it y da t a
The source of the activity data should be reviewed to ensure applicability and relevance to the category. Where
possible, the data should be compared to historical activity data or model outputs to look for anomalies. Data
could be checked with productivity indicators such as fuel per unit of marine traffic performance (freight andpassenger kilometres) compared with other countries.
In preparing the inventory estimates, the inventory agency should take steps to ensure reliability of the activity
data used to allocate emissions between domestic and international water-borne navigation and to ensure that all
fuel sold in the country for water-borne navigation is accounted for in the estimates. A comparison of the activity
data should be conducted between multiple references due to the high uncertainty associated with this data.
External review
The inventory agency should carry out an independent, objective review of calculations, assumptions or
documentation or both of the emissions inventory to assess the effectiveness of the QC programme. The peer
review should be performed by expert(s) who are familiar with the source category and who understand national
greenhouse gas inventory requirements.

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Chapter 2

Energy2.5

MOBILE COMBUSTION: AIRCRAFT

2.5.1

Methodological issues

The IPCC source category for civil aviation includes emissions from all civil commercial use of airplanes(international and domestic) consisting of scheduled and charter traffic for passengers and freight, including air
taxiing, as well as general aviation16 (e.g. agricultural airplanes, private jets or helicopters). Methods discussed inthis section can be used also to estimate emissions from military aviation, but emissions should be reported underthe IPCC category 1A 5 ’Other‘. Stationary combustion and ground transport at airports are to be included inother appropriate categories.
Aircraft emit carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as carbon monoxide (CO),non-methane volatile organic compounds (NMVOCs), sulfur dioxide (SO2), particulate matter (PM) and nitrogenoxides (NOx). This section focuses on the direct greenhouse gases CO2, CH4 and N2O. For more information on
the impact of aviation on the global atmosphere see IPCC (1999).
Parties to the UNFCCC have not made a final decision yet on the allocation to national GHG inventories ofemissions from fuels used for international aviation and from international marine bunkers. For the moment, allemissions from these fuels are to be excluded from national totals, and are to be reported separately.

2.5.1.1

C HOICE OF METHODOne Tier 1 and two Tier 2 methods (designated Tier 2a and 2b) are outlined in the IPCC Guidelines. All methods
are based on distinguishing between domestic fuel use and international fuel use. Tier 1 is purely fuel based,
while the Tier 2 methods are based on the number of landing/take-off cycles (LTOs) and fuel use. The CO2
estimate depends on carbon content of fuel and the fraction oxidised and therefore should not vary significantlywith the tier. Given the current limited knowledge of emission factors, more detailed methods will notsignificantly reduce uncertainties for CH4 and N2O emissions. However, reasons for choosing to use a higher tierinclude estimation of emissions jointly with other pollutants (e.g. NOx), harmonisation of methods with otherinventories, and the possibility of accounting for changes in technologies (and therefore emission factors) in the
future.
All three methods will capture changes in technology that influence fuel consumption. However, only Tier 2b cancapture the effects on CH4 and N2O emissions of changing emission factors. National approaches can also be
used if they are well documented and have been peer reviewed. The choice of method will depend on national
circumstances particularly the availability of data (see the decision trees in Figure 2.7 and Figure 2.8).
The simple Tier 1 method is based on an aggregate figure of fuel consumption for civil aviation multiplied byaverage emissions factors. The emissions factors have been averaged over all flying phases based on theassumption that 10% of the fuel17 is used in the LTO18 (landing/take-off) phase of the flight. Emissions arecalculated according to Equation 2.7:
EQUATION 2.7
Emissions = Fuel Consumption • Emission Factor

The Tier 2 method is only applicable for jet fuel use in jet engines. Aviation gasoline is only used in small
aircraft and generally represents less than 1% of fuel consumption from aviation. In the Tier 2 method a
16 ICAO’s ‘Manual on the ICAO Statistics Programme’ defines ‘general aviation’ as all civil operations other than scheduled
air services and non-scheduled air transport operations for remuneration or hire. For ICAO statistical purposes, the generalaviation activities are classified into instructional flying, business and pleasure flying, aerial work and other flying.
17 Source: Olivier, 1995. This percentage will vary according to national circumstances and countries are encouraged tomake their own assessment.
18 Both a single landing together with a single take-off define one LTO operation that includes all activities near the airportthat take place under an altitude of 914 m (3000 feet): engines running idle, taxi-in and out, take-off, climbing anddescending. Aircraft operations above 914 m are defined as ‘cruise’.

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distinction is made between emissions below and above 914 m (3000 feet) to increase the accuracy of theestimates as emission factors and fuel use factors vary between phases of the flight. The emissions in these two
flying phases are estimated separately, in order to harmonise with methods that were developed for air pollution
programmes that cover only emissions below 3000 feet. Emissions and fuel used in the LTO phase are estimatedfrom statistics on the number of LTOs (aggregate or per aircraft type) and default emission factors or fuel use
factors per LTO cycle (average or per aircraft type).
There may be significant discrepancies between the results of a bottom-up approach and a top-down fuel-based
approach for aircraft. An example is presented in Daggett et al. (1999).

Figure 2.7

Methodology Decision Tree for Aircraft

Box 3
Are
data available onindividual aircraft
LTOs?

Yes

Consider using
Tier 2b based on
individual aircraft
movements

No

Are
LTO data
available at an
aggregatelavel?

Box 2
YesConsider using
Tier 2a based on
aggregate aircraft
movements

No
Box 1
Estimate emissions
using Tier 1

Note 1: There is no key source decision in this decision tree because there is no gain in inventory quality by moving from Tier 1 to Tier 2
if activity data are not complete. Inventory agencies should use the most appropriate method, given the availability of data.

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Chapter 2

EnergyFigure 2.8

Activity Data Decision Tree for Aircraft

Are
total national
fuel statistics
available?

Is itfeasible tosurvey airports or fuelsuppliers?

No

No

Yes

Yes

Initiate datacollection

Do thenational fuelstatistics differentiate
between domestic andinternational fuel use, or is it possible
to survey licensed airlines on
their domestic versus
international
fuel use?

No

Box 3
Yes

Is it
possible to estimate
domestic/international
fuel use based on LTO data per
aircraft type anddistance/time
travelled?

No

Initiate work on datacollection.
Ensure that CO2
emissions arecalculated using theReference Approach

Yes
Box 2
Estimate fuel consumption andcalculate ratio between
domestic and international fueluse. Correct for other uses:
subtract total for stationary use,
add fuel for general aviation.
Verify the data and use
for emission estimation.

Box 1
Estimate fuel consumption andcalculate ratio between
domestic and international fueluse. Correct for other uses:
subtract total for stationary use,
add fuel for general aviation.
Verify the data and use
for emission estimation.

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Chapter 2

Both Tier 2 approaches use Equations 2.8 to 2.11 to estimate emissions:
EQUATION 2.8
Emissions = LTO Emissions + Cruise Emissions
Where
EQUATION 2.9
LTO Emissions = Number of LTOs • Emission FactorLTO

EQUATION 2.10
LTO Fuel Consumption = Number of LTOs • Fuel Consumption per LTO

EQUATION 2.11
Cruise Emissions = (Total Fuel Consumption – LTO Fuel Consumption) • Emission FactorCRUISE

These equations can be applied at either the aggregated level of all aircraft (Tier 2a) or at the level of individual
aircraft types (Tier 2b). For the Tier 2b approach, the estimate should include all aircraft types frequently used
for domestic and international aviation. For the Tier 2a approach, all aircraft are included and the IPCC
Guidelines provide aggregate emission factors per LTO. The aggregated emission factors are proposed fornational and international aviation separately, and for an old and average fleet.
Cruise emissions depend on the length of the flight among other variables. In the Tier 2 method the fuel used in
the cruise phase is estimated as total fuel use minus fuel used in the LTO phase of the flight as shown inEquation 2.11. Fuel use is estimated for domestic and international aviation separately. The estimated fuel use ismultiplied by aggregate emission factors (average or per aircraft type) in order to estimate the emissions.
The resource demand for the various tiers depends on the number of air traffic movements and the availability ofthe data in the country. Tier 1 and Tier 2a, based on aggregate LTO data, should not require considerable
resources, while Tier 2b, based on individual aircraft, may be very time consuming.

2.5.1.2

C HOICE OF EMISSION FACTORS

It is good practice to use emission factors from the IPCC Guidelines. National emission factors for CO2 should
not deviate much from the default values because the quality of jet fuel is well defined. However, there is limited
information on the emission factors for CH4 and N2O from aircraft, and the IPCC default values are similar tovalues found in the literature. Since aircraft technologies do not vary by country, national emission factors should
generally not be used unless based on peer reviewed studies.
Within this sector, different types of aircraft/engine combinations have specific emission factors and these factors
may also vary according to distance flown. It has been assumed that all aircraft have the same emission factors
for CH4 and N2O based on the rate of fuel consumption. This assumption has been made because moredisaggregated emission factors are not available.

MILITARY
Emissions from military aviation may be estimated by the Tier 1 approach (total fuel use and average emission
factors). However, the term ‘military aircraft’ covers very different technologies (e.g. transport planes,
helicopters and fighters) and the use of a more detailed method is encouraged if data are available. No emission
factors for N2O and CH4 have been developed for military aviation. However, many types of military transport
aircraft and helicopters have fuel and emissions characteristics similar to civil types. The default emission factors
for civil aircraft should be used for military aviation unless better data are available. For fuel use factors see‘Choice of activity data’ below.

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2.5.1.3

EnergyC HOICE OF ACTIVITY DATA

According to the IPCC Guidelines, emissions from domestic aviation are reported separately from international
aviation. For this reason, it is necessary to disaggregate fuel use into domestic and international components.
Table 2.9, Distinction between Domestic and International Flights presents good practice in flight classification.
These definitions are a precision of the ones given the IPCC Guidelines. These definitions should be appliedirrespective of the nationality of the carrier.19
TABLE 2.9
DISTINCTION BETWEEN DOMESTIC AND INTERNATIONAL FLIGHTS
Domestic

International

Depart and arrive in same country

Yes

No

Depart from one country and arrive in another

No

Yes

Depart in one country, stop in the same country without dropping or
picking up any passengers or freight, then depart again to arrive inanother country

No

Yes

Depart in one country, stop in the same country and drop and pick up
passengers or freight, then depart finally arriving in another country

Domestic stage

International stage

Depart in one country, stop in the same country, only pick up morepassengers or freight and then depart finally arriving in anothercountryNo

Yes

Departs in one country with a destination in another country, andmakes an intermediate stop in the destination country where no
passengers or cargo are loaded.

No

Both segmentsinternational

For consistency, it is good practice to use similar definitions of domestic and international activities in theaviation and water-borne navigation estimates.
Fuel use data distinguished between domestic and international aviation may be obtained in different ways. Whatis feasible will depend on national circumstances, but some data sources (e.g. energy statistics or surveys) will
give more accurate results than others. The following data sources should be evaluated:
Bottom-up data can be obtained from surveys of airline companies for fuel used, or estimates from aircraft
movement data and standard tables of fuel consumed or both.
Top-down data can be obtained from national energy statistics or surveys of:•

Airports for data covering the delivery of aviation kerosene and aviation gasoline;•

Fuel suppliers (quantity of aviation fuel delivered);•

Refineries (production of aviation fuels), to be corrected for import and export.

Fuel consumption factors for aircraft (fuel used per LTO and per nautical mile cruised) can be used for estimatesand may be obtained from the airline companies. Table 2.10, Fuel Use and Average Sector Distance for
Representative Types of Aircraft, shown in Appendix 2.5A.1 shows the data derived for the sixteen aircraft types
used to represent the world's commercial passenger fleet in the ANCAT/EC2 global inventory20 (ANCAT/EC2,
1998) plus three aircraft which subsequently came into revenue service (Falk, 1999). Similar data could be
19 The treatment of domestic and international aviation, both in the IPCC Guidelines and in Table 2.9 above, differs fromthat recommended to states by the International Civil Aviation Organization for the purposes of classifying flight stages whenreporting air carrier statistical data (ICAO, 1997). In this context, ICAO defines as domestic, all flight stages flown between
domestic points by an air carrier whose principal place of business is in that state and therefore (i) includes flight stages
between domestic points that precede a flight stage to another country, and (ii) excludes flights between domestic points byforeign carriers.
20 The ANCAT/EC2 global inventory was a programme that was part-funded by the EC to produce a world-wide 3D gridded

inventory of fuel used and NOx produced from civil commercial and bizjet aircraft, cargo planes and military operations. Thebase year was 1991/92 and the forecast year was 2015. The data were gridded into 1o • 1o • 1 km boxes by summing
individual movements. The results of the ANCAT/EC2 and NASA inventories were similar to each other.

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obtained from other sources (e.g. EMEP/CORINAIR inventory guidebook, second edition, 1999). The equivalentdata for turboprop and piston engine aircraft need to be obtained from other sources. The relationship between
actual aircraft and representative aircraft is shown in Table 2.11, Correspondence between Representative
Aircraft and Other Aircraft Types in Appendix 2.5A.2.
Aircraft movement data may be obtained from:•

Statistical offices or transport ministries as a part of national statistics;•

Airport records;•

ATC (Air Traffic Control) records, for example EUROCONTROL statistics;•

OAG (Official Airline Guide), published by Reed Publishing (monthly) which contains timetable passenger
and freight movements, but does not contain non-scheduled traffic (e.g. passenger charter and non-scheduled
freight operations);•

Passenger numbers and cargo tonnage data (these are not very reliable because of variations in load factor
and type of aircraft used).

Note that some of these sources do not cover all flights (e.g. charter flights may be excluded). On the other hand,airline guide data may count some flights more than once (Baughcum et al., 1996). Whatever data source is used,inventory agencies must assure completeness. If fuel data for domestic aviation are not readily available, bothdata collection and estimation will usually be time consuming to perform.

MILITARY
Due to confidentiality concerns, it may be difficult to obtain data covering the quantity of fuel used by the
military. This will have consequences for transparency and possibly completeness. Military activity is defined as
those activities for which aviation fuel has been purchased by, or supplied to, the military authority of thecountry. It is good practice to apply the rules defining civilian national and international operations in aviation tomilitary operations where they are comparable. Where they are not comparable, it is good practice to explain
decisions on national and international operations. Unless better information is available, all the fuel should beallocated as domestic. Data on military fuel use may be sought from the military authorities themselves and thefuel suppliers.
The IPCC Guidelines do not provide a method to assess the quantity of fuel from military aviation althoughmilitary fuel use should be available from national data sources. An estimate of fuel used for military aviation is
given in ANCAT/EC2 (1998) (transport and tanker, fighter/bomber and light aircraft/helicopters) together withthe method used to obtain it. Methods for estimating CH4 and N2O emissions are not included.
Alternatively, fuel use may be estimated from the hours in operation. Default fuel consumption factors are given
in Table 2.12, Fuel Consumption Factors for Military Aircraft shown in Appendix 2.5A.3.
According to COP Decision 2/CP3 a multilateral operation should not be included in national totals but reported
separately, although there is no clear operational definition of ‘multilateral operation’ available at this time.

2.5.1.4

C OMPLETENESS

Regardless of method, it is important to account for all fuel sold for aviation in the country. The methods are
based on total fuel use, and should completely cover CO2 emissions. However, the Tier 2 methods focus onpassenger and freight carrying scheduled and charter flights, and not all aviation. In addition, they do not
automatically include non-scheduled flights and general aviation such as agricultural airplanes, private jets orhelicopters, which should be added if the quantity of fuel is significant. Completeness may also be an issue where
military data are confidential, unless military fuel use is aggregated with another source category.

2.5.1.5

D EVELOPING A CONSISTENT TIME SERIES

Chapter 7, Methodological Choice and Recalculation, Section 7.3.2.2, Alternative Recalculation Techniques
provides more information on how to develop emission estimates in cases where the same data sets or methods
cannot be used during every year of the time series. If activity data are unavailable for the base year (e.g. 1990)
an option may be to extrapolate data to this year by using changes in freight and passenger kilometres, total fuelused or supplied, or the number of LTOs (aircraft movements).
Emissions trends of CH4 and NOx (and by inference N2O) will depend on aircraft engine technology and thechange in composition of a country's fleet. This change in fleet composition may have to be accounted for in the

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Chapter 2

Energyfuture, and this is best accomplished using the Tier 2b method based on individual aircraft types for 1990 and
subsequent years. If fleet composition is not changing, the same set of emission factors should be used for all
years.
Every method should be able to reflect accurately the results of mitigation options that lead to changes in fueluse. Only the Tier 2b method, based on individual aircraft, can capture the effect of mitigation options that resultin lower emission factors.

2.5.1.6

U NCERTAINTY ASSESSMENT

ACTIVITY DATA
The uncertainty in the reporting will be strongly influenced by the accuracy of the data collected on domestic
aviation separately from international aviation. With complete survey data, the uncertainty may be very low (lessthan 5%) while for estimates or incomplete surveys the uncertainties may become large, perhaps a factor of two
for the domestic share.21

EMISSION FACTORSThe CO2 emission factors should be within a range of ±5%, as they are dependent only on the carbon content of
the fuel and fraction oxidised. The uncertainty of the CH4 emission factor may be as a high as a factor of 2. The
uncertainty of the N2O emission factor may be of several orders of magnitude (i.e. a factor of 10, 100 or more).

2.5.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
Some examples of specific documentation and reporting relevant to this source category are provided below.
The IPCC Guidelines require that inventory agencies report emissions from international aviation separatelyfrom domestic aviation, and exclude international aviation from national totals. It is expected that all countries
have aviation activity and should therefore report emissions from this category. Though countries covering small
areas might not have domestic aviation, emissions from international aviation should be reported.
Transparency would be improved if inventory agencies report emissions from LTO separately from cruise
operations (defined here as operations above 3000 feet or 914 m).
Emissions from military aviation should be clearly specified, so as to improve the transparency on national
greenhouse gas inventories.
In addition to the standard reporting required in the IPCC Guidelines, provision of the following data would
increase transparency:•

Sources of fuel data and other essential data (e.g. fuel consumption factors) depending on the method used;•

The number of flight movements split between domestic and international;•

Emission factors used, if different from default values. Data sources should be referenced.

Inventory agencies should provide the definition of international and domestic that has been used and document
why and how it was applied.
Confidentiality may be a problem if only one or two airline companies operate domestic transport in a given
country. Confidentiality may also be a problem for reporting military aviation in a transparent manner.

21 The uncertainty ranges cited in this section represent an informal polling of assembled experts aiming to approximate the

95% confidence interval around the central estimate.

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2.5.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Co mpa r iso n o f e missio ns using a lt e r na t iv e a ppro a c hes
The inventory agency should compare the emission estimates for aircraft using both Tier 1 and Tier 2
approaches. Any anomaly between the emission estimates should be investigated and explained. The results ofsuch comparisons should be recorded for internal documentation.
Rev ie w o f Emissio n f a c t o r s
If national factors are used rather than the default values, directly reference the QC review associated with the
publication of the emission factors, and include this review in the QA/QC documentation to ensure that theprocedures are consistent with good practice. If possible, the inventory agency should compare the IPCC default
values to national factors to provide further indication that the factors are applicable. If emissions from military
use were developed using data other than the default factors, the accuracy of the calculations and the applicability
and relevance of the data should be checked.
Activity da ta check
The source of the activity data should be reviewed to ensure applicability and relevance to the source category.
Where possible, the inventory agency should compare current data to historical activity data or model outputs tolook for anomalies. In preparing the inventory estimates, the inventory agency should ensure the reliability of theactivity data used to allocate emissions between domestic and international aviation.
Data could be checked with productivity indicators such as fuel per unit of traffic performance (per passenger km
or ton km). Where data from different countries are being compared, the band of data should be small.
External review
The inventory agency should perform an independent, objective review of calculations, assumptions or
documentation of the emissions inventory to assess the effectiveness of the QC programme. The peer review
should be performed by expert(s) (e.g. aviation authorities, airline companies, and military staff) who are familiar
with the source category and who understand inventory requirements.

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EnergyAppendix 2.5A.1 Fuel use and average sector
distance for representative types of aircraft
TABLE 2.10
FUEL USE AND AVERAGE SECTOR DISTANCE FOR REPRESENTATIVE TYPES OF AIRCRAFT
Aircraft
A310

A320

A330
300 LR

A340

BAC1- BAe 146
11

B727

B737
100-200

B737
400

Total flight

1 228

663

1 087

2 860

465

327

583

504

531

Climb

81

159

113

111

143

106

117

127

100

Cruise

1 034

393

832

2 615

234

152

384

291

339

Descent

113

111

142

134

88

69

82

86

92

Total flight

12 160

4 342

15 10837 317

2 965

2 272

6 269

3 747

3 750

LTO (flight < 3000 ft)

1 541

802

2 232

2 020

682

570

1 413

920

825

Flight minus LTO(flight > 3000 ft)

10 6203 539

12 87635 298

2 284

1 702

4 856

2 827

2 925

8.65

5.34

11.85

12.34

4.91

5.21

8.33

5.61

5.51

Average sector distance innautical miles (nm)

Fuel use (kg)

Fuel use (kg per nm)
Flight minus LTO(flight > 3000 ft)

These data should be used with care as national circumstances may vary from those assumed in this table. In particular, distances travelled
and fuel consumption may be affected by national route structures, airport congestion and air traffic control practices. Fuel consumption
may also be affected by wind. For example, since westbound transatlantic flights usually take more time and burn more fuel than eastboundones, use of the averages in the table (or those in the IPCC Guidelines) may underestimate fuel consumption of westbound flights (reported
by e.g. European countries) and overestimate eastbound (reported by e.g. USA or Canada).

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TABLE 2.10 (CONTINUED)FUEL USE AND AVERAGE SECTOR DISTANCE FOR REPRESENTATIVE TYPES OF AIRCRAFT
Aircraft
B747
100-300

B747
400

B757

B767
300 ER

B777

F28

F100

DC9

DC1030MD
82-88

Total flight

2 741

2 938

958

1 434

1 579

295

360

384

2 118

557

Climb

152

95

106

100

112

131

118

118

117

161

Cruise

2 480

2 727

744

1 205

1 325

91

158

182

1 902

306

Descent

109

116

108

129

141

73

84

84

99

90

Total flight

60 70558 3258 111

14 80623 627

2 104

2 597

3 202

35 171

4 872

LTO (flight < 3000 ft)

3 414

3 402

1 253

1 617

2 563

666

744

876

2 381

1 003

Flight minus LTO (flight >3000 ft)

57 29154 9236 858

13 18921 064

1 438

1 853

2 326

32 790

3 869

20.90

18.69

7.16

9.20

13.34

4.87

5.15

6.06

15.48

6.95

Average sector distance innautical miles (nm)

Fuel use (kg)

Fuel use (kg per nm)
Flight minus LTO(flight > 3000 ft)

Source: ANCAT/EC2 and UK Department of Trade and Industry (DTI/EID3cC/199803).

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EnergyAppendix 2.5A.2 Correspondence between
representative aircraft and other aircraft types
TABLE 2.11
CORRESPONDENCE BETWEEN REPRESENTATIVE AIRCRAFT AND OTHER AIRCRAFT TYPES
Generic
Generic ICAO IATA
aircraft aircraft
aircraftin group type
type
BAe 146 BA46

Airbus
A310

A310

141

Generic
ICAO IATA
aircraft aircraftin group typeAirbus A320 A320

320

Boeing
747-400

143

32S

Boeing
757

146

ICAO

Generic
IATA
aircraft aircraftin group type

ICAO

IATA
aircraftin group

B744

744

DC10

D10

McDonnell
Douglas
DC10

757

D11

321

75F

D1C

TR2

D1F

762

L10

14F

Airbus A319 A319

319

310

Airbus A330 A330

330

Boeing
767

312

332

763

L11

313

333

767

L12

340

AB3

L15

A31

Airbus A340 A340

Boeing727-100

B721

721

342

AB6

M11

Boeing727-200

B722

722

343

A3E

M1F

Boeing727-300

B727

727

B11

ABF

72A

B15

AB4

D8F

72F

CRV

Boeing
777

777

D8M

72M

F23

Boeing
777-200

B772

772

D8S

72S

F24

Boeing
777-300

B773

773

707

TU5

YK4

McDonnell
Douglas
DC-9

D92

70F

BAe 111BA11McDonnell
Douglas DC8

DC8

Boeing
737-200

B732

732

Boeing 747- B741
100-300

741

D93

IL6

Boeing
737-500

B735

735

B742

742

D94

B72

73A

B743

743

D95

73B

747

D98

73F

74D

D9S

73M

74E

DC9

73S

74F

F21

D86

A4F

TRD

JET

74L

YK2

DAM

74M

McDonnell MD81Douglas
88
M81-88M80

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TABLE 2.11 (CONTINUED)CORRESPONDENCE BETWEEN REPRESENTATIVE AIRCRAFT AND OTHER AIRCRAFT TYPES
Generic
Generic ICAO IATA
aircraft aircraft
aircraftin group type
type

Generic
ICAO IATA
aircraft aircraftin group type

ICAO

Generic
IATA
aircraft aircraftin group type

Boeing
737-300

B733

733

IL7

M82

Boeing
737-700

B737

737

ILW

M83

Fokker
100

F100

100

NIM

M87

Fokker
F-28

F28

F28

VCX

M88

TU3

C51

ICAO

IATA
aircraftin group

MD90 goes as MD81-88 and B737-600 goes as B737-400. DC8 goes as double the B737-100.
Source: Falk (1999b) and EMEP/CORINAIR (1999).

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EnergyAppendix 2.5A.3 Fuel consumption factors formilitary aircraft
TABLE 2.12
FUEL CONSUMPTION FACTORS FOR MILITARY AIRCRAFT
Group

Sub-group

Representative type

CombatFast Jet - High Thrust

F16

3 283

Fast Jet - Low Thrust

Tiger F-5E

2 100

Jet trainers

Hawk

720

Turboprop trainers

PC-7

120

Large Tanker/Transport

C-130

2 225

Small Transport

ATP

499

MPAs, Maritime Patrol

C-130

2 225

Trainer

Tanker/Transport

Other

Fuel flow (kg/hour)

Source: Tables 3.1 and 3.2 of ANCAT/EC2 1998, British Aerospace/Airbus.

TABLE 2.13
ANNUAL AVERAGE FUEL CONSUMPTION PER FLIGHT HOUR FOR UNITED STATES MILITARY AIRCRAFT ENGAGED IN
PEACETIME TRAINING OPERATIONS
Aircraft Type

Aircraft Description

Fuel Use(Litres per Hour)

A-10A

Twin engine light bomber

2 331

B-1B

Four engine long-range strategic bomber. Used by USA only

13 959B-52H

Eight engine long-range strategic bomber. Used by USA only.

12 833

C-12J

Twin turboprop light transport. Beech King Air variant.

398

C-130E

Four turboprop transport. Used by many countries.

2 956

C-141B

Four engine long-range transport. Used by USA only

7 849

C-5B

Four engine long-range heavy transport. Used by USA only

13 473

C-9C

Twin engine transport. Military variant of DC-9.

3 745

E-4B

Four engine transport. Military variant of Boeing 747.

17 339

F-15D

Twin engine fighter.

5 825

F-15E

Twin engine fighter-bomber

6 951

F-16C

Single engine fighter. Used by many countries.

3 252

KC-10A

Three engine tanker. Military variant of DC-10

10 002KC-135E

Four engine tanker. Military variant of Boeing 707.

7 134

KC-135R

Four engine tanker with newer engines. Boeing 707 variant.

6 064

T-37B

Twin engine jet trainer.

694

T-38A

Twin engine jet trainer. Similar to F-5.

262

These data should be used with care as national circumstances may vary from those assumed in this table. In particular, distances
travelled and fuel consumption may be affected by national route structures, airport congestion and air traffic control practices.
Source: US Environmental Protection Agency, Inventory of US Greenhouse Gas Emissions and Sinks, 1990-1998, EPA-236-R-00-001(Forthcoming, April 2000). Data provided by the US Department of Defense.

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2.6

FUGITIVE EMISSIONS FROM COALMINING AND HANDLING

2.6.1

Methodological issues

The geological process of coal formation also produces methane (CH4), some of which remains trapped in thecoal seam until it is mined. Generally, deeper underground coal seams contain more in-situ methane thanshallower surface seams. Consequently, the majority of emissions come from deep underground mines.
Additional emissions come from open-pit mines and post-mining activities.

2.6.1.1

C HOICE OF METHOD

Those coal-mining countries whose major production is from underground mining, particularly longwall
operations, the emissions from this sub-source category will dominate and efforts should focus on this part of theoverall coal estimate. However, where there is extensive open-cut mining such as in Australia, emissions fromthis activity can also be significant. Figure 2.9, Decision Tree for Surface Coal Mining and Handling, to Figure
2.11, Decision Tree for Post-mining provide guidance in choosing the appropriate method for all sources of coalmine methane. The IPCC Guidelines give the following general equation for estimating emissions:
EQUATION 2.12
Emissions = Coal Production (Surface or Underground) • Emission Factor

The Tier 2 approach is to use country or basin-specific emission factors that reflect the average methane content
of coal actually mined. The Tier 1 default approach requires that countries choose from a global average range ofemission factors, and is more uncertain as a consequence. For underground mines, actual measurement data may
be available. Although not specified explicitly as Tier 3 in the coal chapter of the IPCC Guidelines, the use ofmeasurement data is generally regarded as a Tier 3 approach.
Total annual emissions are calculated according to the following equation:
EQUATION 2.13
Total Emissions = Underground Mining Emissions + Surface Mining Emissions +Post-Mining Emissions – Methane Recovered and Used or Flared

UNDERGROUND MINING
Emissions from underground mining come from ventilation systems and degasification systems. Ventilation
systems are a safety requirement at underground mines and dilute the ambient methane concentration of mine air
below a dangerous level by flushing the mine with air from the surface. Degasification systems are wells drilled
before, during, and after mining to drain methane from the coal seam itself.
For countries with underground mining operations, it is good practice to collect data for the Tier 3 method if themine-specific measurement data are available for safety reasons. Mine-specific data, based on ventilation air
measurements and degasification system measurements, reflect actual emissions on a mine-by-mine basis, andtherefore produce a more accurate estimate than emission factors. This is due to the variability of in-situ gas
content of coal and its geological environment. As emissions vary greatly over the course of a year, good practiceis to collect measurement data at least every two weeks to smooth out variations. Daily measurements would
ensure a higher quality estimate. Continuous monitoring of emissions represents the highest stage of emission
monitoring, and is implemented in some modern longwall mines, but it is not necessary for good practice.

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Chapter 2

Figure 2.9

EnergyDecision Tree for Surface Coal Mining and HandlingIs therecoal mining in the
country?

No

Report‘Not Occurring’Yes

Are nationalemission factors
available?

Yes

No

If CoalMining is a key
source category, is surface
mining significant?
(Note 1)

Box 1
No

Estimateemissions using
Tier 1

Yes
Collect data todevelop nationalemission factors

Box 2
Estimate emissions
using nationalemission factors(Tier 2)

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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Figure 2.10

Decision Tree for Underground Coal Mining and
Handling

Is therecoal mining in the
country?

No

Report‘Not Occurring’Yes

Are any
measurement data
available?

No

If
Coal Mining isa key source category, isunder-ground mining
significant?
(Note 1)

Box 1
Is anyNocoal mine methane
used or flared?

No

Estimateemissions using
Tier 2 or Tier 1

Yes

Yes
Yes
Box 2

Estimate emissions
using Tier 2 or Tier 1,
adjusted formethane use

Collect
measurement
data

Box 4
Is anycoal mine methane
used or flared?

No

Estimate emissions using
direct measurement(Tier 3) supplemented with
Tier 2 estimates for mines
without measurements

Yes
Box 3
Estimate emission using
direct measurements (Tier3) supplemented with Tier 2
estimates for mines without
measurements and adjustingfor methane use

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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Chapter 2

Figure 2.11

EnergyDecision Tree for Post-mining

Is therecoal mining in the
country?

No

Report‘Not Occurring’

Yes
Box 1
Are nationalemission factors
available?

No

Estimateemissions using
Tier 1

Yes
Box 2
Estimate emissions
using nationalemission factors(Tier 2)High quality measurements of methane drained by degasification systems should also be available from mine
operators for those mines where drainage is practised. If detailed data on drainage rates are absent, good practiceis to obtain data on the efficiency of the systems (i.e. the fraction of gas drained) or to make an estimate of thisfraction from a range (e.g. 30-50%, typical of many degasification systems). Another option is to compare
conditions with associated mines where data are available. In cases where drainage occurs years in advance ofmining, methane recovery should be accounted for in the year in which the source coal seam is extracted.
Methane recovered from degasification systems and vented to the atmosphere prior to mining should be added tothe amount of additional methane released through ventilation systems so that the total estimate is complete. In
some cases, because degasification system data are considered confidential, it may be necessary to estimate
degasification system collection efficiency, and then subtract known reductions to arrive at the net degasification
system emissions.
An alternative hybrid Tier 3 - Tier 2 approach is appropriate in situations when mine-specific measurement data
are available only for a subset of underground mines. For example, if only gassy mines report data, emissions
from the remaining mines can be calculated with Tier 2 emission factors. These factors could be based on
specific emission rates derived from Tier 3 data if the mines are operating within the same basin as the Tier 3
mines, or on the basis of mine-specific properties, such as the average depth of the coal mines.
Comprehensive mine-by-mine (i.e. Tier 3) data may be available for some but not all years. If there have been no
major changes in the population of active mines, emissions can be scaled to production for the missing years. If
there were changes in the mine population, the mines involved can be removed from the scaling extrapolation andhandled separately. However, care must be taken in scaling because the coal being mined, the virgin exposed coaland the disturbed mining zone have different emission rates. Furthermore, mines may have a high backgroundemission level that is independent of production.
When no mine-by-mine data are available, inventory agencies should employ the Tier 2 method (country orbasin-specific emission factors). For some countries, it may be necessary to separate the mine production into
production from larger mines (Tier 2) and smaller independent mines (Tier 1) if smaller mines exhibit
significantly different methane emission patterns (e.g. shallower seams).

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SURFACE MINING
It is not feasible to collect mine-by-mine Tier 3 measurement data for surface mines. The alternative is to collectdata on surface mine production and apply emission factors. For countries with significant coal production andmultiple coal basins, disaggregation to the basin level will improve accuracy. Given the uncertainty of
production-based emission factors, picking emission factors from the range specified by the IPCC Guidelines canprovide a reasonable estimate.

POST-MINING
Methane still present in the coal after mining will escape to the atmosphere eventually. Measurement of postmining emissions is not feasible, however, so an emission factor approach must be used. The Tier 2 and Tier 1
methods in the IPCC Guidelines should be reasonable for this source, given the difficulty of obtaining better
data.

RECOVERY OF METHANE FOR UTILISATION OR FLARING
If methane is drained from coal seams and subsequently flared or used as a fuel, it is good practice to subtract
this amount from the total estimate of emissions. (Emissions from combustion of recovered methane should be
accounted for appropriately in the combustion section.) Where utilisation data are not directly available frommine operators, gas sales could be used as a proxy. If gas sales are unavailable, the alternative is to estimate theamount of utilised methane from the known efficiency specifications of the drainage system.
In some countries, it is common practice to drain and utilise coal bed methane many years prior to mining. In
other instances, gas wells are drilled in coal seams that are too deep to be mined. Fugitive emissions up to thepoint of utilisation should be counted in coal mining activities. Subsequent downstream emissions should beallocated to the source category appropriate to the manner of utilisation. Examples include oil and natural gas
when the methane is fed to the natural gas grid and to electricity autoproducers when used to generate electricity.
Note that where coal seam methane is recovered with no intention of mining the coal, emissions fall within the oiland natural gas source category.
The estimate of CH4 emissions from coal mining may or may not need to be corrected for the amount of gas
released depending on whether:•

The coal is extracted a few years later and the CH4 emissions estimate for that year is based on average
emission factors that do not take account of early gas draining; in this case a correction is needed for the yearof extraction;•

The coal is extracted a few years later and the CH4 emissions estimate is based on direct emissions
measurements. In this case no correction is needed;•

The coal is never extracted (e.g. due to changes in plans or because it was never the intention). In this caseno correction is needed.

Flaring is an option for reducing methane emissions from coal mines, and is practised at some coal mines. Dataon the amount of methane flared should be obtained from mine operators with the same frequency ofmeasurement as pertains to underground mine emissions generally.

2.6.1.2

C HOICE OF EMISSION FACTORSUNDERGROUND MINING
Tier 3: The Tier 3 method does not use production-based emission factors, but rather actual measurement datathat account for the temporal and spatial variability in coal mine emissions. As this is by far the most reliable
method, inventory agencies should make every effort to collect these data if underground mining is a key subsource category.
Tier 2: Country-specific emission factors can be obtained from sample ventilation air data, or from a quantitative
relationship that accounts for the gas content of the coal seam and the surrounding strata affected by the mining
process. For a typical longwall operation, the amount of gas released comes from the coal being extracted andfrom the coal and any other gas bearing strata 150 m above and 50 m below the mined seam. Where such
relationships are used, they should be peer-reviewed and well documented.
Tier 1: Inventory agencies choosing from the emission factor range (10-25 m3/tonne) in the Tier 1 methodology
should consider country-specific variables such as depth of major coal seams. As gas content of coal usually

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Chapter 2

Energyincreases with depth, the low end of the range should be chosen for average mining depths of <200 m, and for
depths of > 400 m the high value is appropriate. For intermediate depths, intermediate values can be chosen.

SURFACE MINING
There are few measurements of methane emissions from surface mining. They are difficult and expensive to carryout and no routine methods are currently available. Data on in-situ gas contents before overburden removal arealso very scarce, and in freshly uncovered coal the gas content is often close to zero. Where local data on
emissions are available, they should be used.
For the Tier 1 approach, it is good practice to use the low end of the specific emission range for those mines withaverage overburden depths of <25 m and the high end for overburden depths over 50 meters. For intermediate
depths, intermediate values for the emission factors may be used. In the absence of data on overburden thickness,
it is good practice to use an emission factor towards the high end of the range, namely 1.5 m3/tonne.

POST-MINING EMISSIONS – UNDERGROUND
Measurements on coal as it emerges on a conveyor from a mine without pre-mining degasification indicate that25-40% of the in-situ gas is still in the coal (Williams and Saghafi, 1993). For mines that practice pre-drainage,
the amount of gas in coal will be less by some unknown amount.
For mines with no pre-drainage, but with knowledge of the in-situ gas content, it is reasonable to set the post
mining emission factor at 30% of this value. For mines with pre-drainage, an emission factor of 10% of the insitu gas content is suggested. Where there are no in-situ gas content data or where pre-drainage is practised, but
to an unknown extent, a reasonable approach is to increase overall underground emissions by 3% (Williams etal., 1993; Riemer, 1999).

POST-MINING EMISSIONS – SURFACE MINING
Unless there are data to the contrary, emissions from this sub-source category are assumed to be negligible, as thegas content of surface coal are typically very low. Emissions can be viewed as being accommodated within thesurface emission factor.

2.6.1.3

C HOICE OF ACTIVITY DATA

For the Tier 3 method, coal production data are not necessary because actual measurements are available.
However, it is good practice to collect and report these data to illustrate the relationship, if any, between
underground coal production and actual emissions on an annual basis.
The activity data for Tiers 1 and 2 are coal production. Mine operators are likely to know more about coalproduction than methane emissions, but inventory agencies need to consider how the information is collected. For
example, using cleaned coal production data instead of raw coal production data will change the final emissions
estimate because emission factors are expressed in cubic meters per ton. Variable moisture content is anotherimportant issue.
If the data on raw coal production are available these should be used. If coal is not sent to a coal preparation
plant or washery (used to upgrade the raw ‘run of mine’ coal by removing some of the mineral matter), then raw
coal production equals the amount of saleable coal.
Where coal is upgraded, some coal is rejected in the form of coarse discards containing high mineral matter andalso in the form of unrecoverable fines. The amount of waste is typically around 20% of the weight of raw coal
feed, but may vary considerably by country. Where activity data are in the form of saleable coal, some effort
should be made to determine the amount of production that is washed. Raw coal production is then estimated byincreasing the amount of ‘saleable coal’ by the fraction lost through washing.
An alternative approach that may be more suitable for mines whose raw coal output contains rock from the roof
or floor as a deliberate part of the extraction process, is to use saleable coal data, provided the emission factors
used refer to clean coal not raw coal. This should be noted in the inventory.

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2.6.1.4

C OMPLETENESSUNDERGROUND MINING
The estimate of emissions from underground mining should include both ventilation systems and degasification
systems when both are present.

ABANDONED MINESNo method currently exists for estimating emissions from this sub-source category. For mines that are flooded,
emissions are likely to be prevented, but some leakage is likely in mines that are sealed mechanically. Good
practice is to record the date of mine closure and the method of sealing. Data on the size and depth of such mines
would be useful for any post hoc estimation.

CO 2 IN SEAM GASCountries with significant quantities of CO2 in their coal seam gas should make efforts to evaluate or quantify
these emissions.

COAL FIRES, COMBUSTION AND OXIDATION OF WASTE COAL AND
OTHER CARBONACEOUS MATERIALS (CO 2 )IPCC recognises that there are emissions from these sub-source categories, but does not provide methods.
Emissions could be significant, but are very difficult to estimate.

2.6.1.5

D EVELOPING A CONSISTENT TIME SERIESIn cases where an inventory agency moves from a Tier 1 or Tier 2 to a Tier 3 method, it may be necessary to
calculate implied emissions factors for years with measurement data, and apply these emission factors to coalproduction for years in which these data do not exist. It is important to consider if the composition of the mine
population has changed dramatically during the interim period, because this could introduce uncertainty. For
mines that have been abandoned since 1990, data may not be archived if the company disappears. These minesshould be treated separately when adjusting the time series for consistency. For good practice guidance on
ensuring time series consistency, see Chapter 7, Methodological Choice and Recalculation.

2.6.1.6

U NCERTAINTY ASSESSMENTEMISSIONS
Tier 3
Methane emissions from underground mines have a significant natural variability. Spot measurements of [CH4](the square brackets denote concentration) in ventilation air are probably accurate to ±20% depending on theequipment used. Time series data or repeat measurements will significantly reduce the uncertainty of annual
emissions to ±5% for continuous monitoring, and 10-15% for every two weeks.22 Ventilation airflows are usually
fairly accurately known (±2%).
Spot measurement of [CH4] in drained gas (degasification systems) is likely to be accurate to ±2% because of its
higher concentration. Measurements should be made with a frequency comparable to those for ventilation air to
get representative sampling. Degasification flows are probably known to ±5%. Degasification flows based on gas
sales are also likely to have an uncertainty of at least ±5% due to the tolerances in pipeline gas quality.
As the gas liberated (gas make) by longwall mining can vary by a factor of two during the life of a longwall panel(a 1-2 km long x 200 m wide block of coal that is extracted in the course of 6-9 months by a single longwall
machine), it is necessary to make frequent measurements of underground mine emissions. Frequent
measurements will also reduce the intrinsic errors in the measurement techniques. Mines with multiple longwall

22 The uncertainty ranges cited in this section represent an informal polling of assembled experts aiming to approximate the
95% confidence interval around the central estimate.

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Chapter 2

Energymachines will be less subject to such wide fluctuations. There may also be uncertainty concerning utilisation ofany methane gas drained years before the source coal seam is extracted.
For a single longwall operation, with continuous or daily emission measurements, the accuracy of monthly or
annual average emissions data is probably ±5%. The accuracy of spot measurements performed every two weeks
is ±10%, at 3-monthly intervals ±30%. Aggregating emissions from mines based on the less frequent type ofmeasurement procedures will reduce the uncertainty caused by fluctuations in gas make. However, as fugitive
emissions are often dominated by contributions from only a small number of mines, it is difficult to estimate theextent of this improvement.

Tiers 1 and 2
If a Tier 2 emission factor for underground mining is derived from Tier 3 data, then the errors or uncertainty in
the Tier 3 data can flow through to the derived emission factor for Tier 2. The following table gives some
impression of likely uncertainties:
TABLE 2.14
LIKELY UNCERTAINTIES OF COAL MINE METHANE EMISSION FACTORS
MethodUnderground

SurfacePost-Mining

Tier 2±50-75%factor of 2

±50%

Tier 1

factor of 2

factor of 3

factor of 3

Source: Judgement by Expert Group (see Co-chairs, Editors and Experts; Fugitive Emissions from Coal Mining and Handling).

ACTIVITY DATA
Coal production: Tonnages are likely to be known to 1-2%, but if raw coal data are not available, then theuncertainty will increase to about ±5%, when converting from saleable coal production data. The data are also
influenced by moisture content, which is usually present at levels between 5-10%, and may not be determinedwith great accuracy.
Apart from measurement uncertainty, there can be further uncertainties introduced by the nature of the statistical
databases that are not considered here. In countries with a mix of regulated and unregulated mines, activity data
may have an uncertainty of ±10%.

2.6.2

Reporting and documentation

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
To ensure transparency, the following information should be supplied:•

Emissions by underground, surface, and post-mining components of CH4 and CO2 (where appropriate), themethod used for each of the sub-source categories, the number of active mines in each sub-source category
and the reasons for the chosen EFs (e.g. depth of mining, data on in-situ gas contents etc.). The amount ofdrained gas and the degree of any mitigation or utilisation should be presented with a description of thetechnology used, where appropriate.

•

Activity data: Specify the amount and type of production, underground and surface coal, listing raw andsaleable amounts where available.

•

Where issues of confidentiality arise, the name of the mine need not be disclosed. Most countries will havemore than three mines, so mine-specific production cannot be back calculated from the emission estimates.

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2.6.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Co mpa r iso n o f e missio ns using a lt e r na t iv e a ppro a c hes
The inventory agency should compare the emission estimates for fugitive methane emissions from coal mining
and handling using both Tier 1 and Tier 2 approaches. If direct measurements are available, these should also becompared to the Tier 1 and 2 estimates. Large discrepancies between the emission estimates should be
investigated and explained. The results of such comparisons should be recorded for internal documentation.
Review of direct emission measurements
If direct measurements are used to develop country-specific emission factors, it should be established whether
measurements at the sites were made according to internationally recognised, standard methods. If themeasurement practices fail this criterion, then the use of these emissions data should be carefully evaluated,uncertainty estimates reconsidered, and qualifications documented. Frequent measurements are usually requiredby regulatory bodies. In the absence of such regulations, measurements should be done frequently enough(weekly if possible), as emissions rates may vary considerably over the year.
Emission factors check
The inventory agency should compare measurement-based factors to IPCC defaults and factors developed byother countries with similar coal mining and handling characteristics. The QA/QC review associated with theoriginal data should be directly referenced in the documentation.
If IPCC default factors are used, the inventory agency should ensure that they are applicable and relevant to thecategory. If possible, the IPCC default factors should be compared to national or local data to provide further
indication that the factors are applicable.
Activity da ta check
The inventory agency should ensure that the data reflects raw coal production. Where possible, the data should
be compared to historical activity data to look for anomalies. Compare activity data between multiple references(e.g. national statistics and mill-level data). To check methane utilisation consistency, gas or electricity sales
could be used as a cross-check.
External review
The inventory agency should arrange for an independent, objective review of calculations, assumptions, and/or
documentation of the emissions inventory to be performed to assess the effectiveness of the QC programme. The
peer review should be performed by expert(s) who are familiar with the source category and who understandinventory requirements.

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Energy2.7

FUGITIVE EMISSIONS FROM OIL ANDGAS OPERATIONS

2.7.1

Methodological issues

Fugitive emissions from oil and natural gas activities include all emissions from the exploration, production,
processing, transport, and use of oil and natural gas, and from non-productive combustion (e.g. flaring and wastegas incineration). It excludes use of oil and gas or derived products to provide energy for internal use, in energy
production, processing and transport. The latter are considered fuel consumption and are addressed separately in
the IPCC Guidelines (Sections 1.3 to 1.5).
Fugitive emissions of methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) from oil and gas operations
are a source of direct and indirect greenhouse gas emissions in many countries. Unfortunately, these emissions
are difficult to quantify accurately. This is largely due to the diversity of the industry, the large number andvariety of potential emission sources, the wide variations in emission-control levels, and the limited availabilityof emission-source data. The main emission assessment issues are:•

The use of simple production-based emission factors introduces excessive error;•

The application of rigorous bottom-up approaches requires expert knowledge and detailed data that may bedifficult and costly to obtain;•

Measurement programmes are time consuming and very costly to perform.

If a rigorous bottom-up approach is chosen, then it is good practice to involve technical representatives from theindustry in the development of the inventory.

2.7.1.1

C HOICE OF METHODThe IPCC Guidelines describe two methods to calculate CH4 emissions from both the oil and gas industries(called Tier 1 and Tier 3), and one additional method (called Tier 2) to calculate CH4 emissions only from oilsystems. The Tier 3 method is a rigorous source-specific evaluation, requiring detailed inventories ofinfrastructure, and detailed bottom-up emission factors. The Tier 2 approach for CH4 emissions from the oil
industry is based on a mass balance estimate of the maximum amount of CH4 that could be emitted. The Tier 1
method uses aggregate production-based emission factors and national production data.23
Good practice is to disaggregate the industry into the applicable segments and subcategories indicated inTable 2.15, Major Categories and Subcategories in the Oil and Gas Industry, and then evaluate the emissions
separately for each of these parts. The approach to estimate emissions from each segment should becommensurate with the emissions level and the available resources. Consequently, it may be appropriate to apply
different approaches to different parts of the industry, and possibly even include some direct monitoring ofemission sources. The overall approach, over time, should be one of progressive refinement to address the areasof greatest uncertainty and consequence, and to capture the impact of specific control measures.
Figure 2.12 provides a general decision tree for Natural Gas Systems for selecting an appropriate approach for agiven segment of the natural gas system. Similarly, Figures 2.13 and 2.14 apply to oil production and transportsystems, and to oil upgraders and refineries, respectively.

23 There is no Tier 2 method for natural gas systems in the IPCC Guidelines.

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Figure 2.12

Decision Tree for Natural Gas Systems

Is therea natural gas systemin the country?

No

Report‘Not Occurring’Yes

Are actual
measurements or
sufficient data available toestimate emissions using
rigorous emission
source models?

Box 4
Yes

Estimate emissions
using rigorous emission
source models (Tier 3)

No

Are detailed
infrastructure data
available?

No

If
Fugitive
Emissions from Oil and
Gas Operations are key source
categories, are Natural Gas
Systems significant?
(Note 1)

Yes

Box 1
No

Estimate emissions
using a Tier 1
approach

Yes

Collect detailed
infrastructuredata

Are nationalemission factors
available?

Yes

No
Box 2
Estimate emissions using
appropriate emission
factors from the generalliterature andinfrastructure data

Box 3
Estimate emissions
using national emission
factors andinfrastructure data

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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Chapter 2

EnergyFigure 2.13

Decision Tree for Crude Oil Production and Transport

Is therecoal mining in the
country?

No

Report‘Not Occurring’

Yes

Is it
possible to collector estimate data for thevented, flared, utilised conserved
and reinjected volumes ofassociated and solution
gas production?

No

Box 1

If Fugitive
Emissions from Oiland Gas Operations are key
source Categories, is the
sub-source significant?
(Note 1)

No

Estimate emissions
using a Tier 1
approach

Yes
Collect data on associatedand solution gas

Yes
Is it
possible to estimate
total associated and solution
gas volumes (e.g. based on GOR
data (Note 2)), and is morethan 20% vented
or flared?

Box 2
Estimate emissions
using a Tier 2
approach

Yes

No
Box 3

Are detailed
infrastructure data
available?

Yes

Are nationalemission factors
available?

Yes

Estimate emissions
using a Tier 3
approach andnational emission
factors

No

No
Box 4
Collect or
estimate detailed
infrastructure data

Estimate emissions
using appropriate
emission factors fromthe general literature

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)
Note 2: GOR stands for Gas/Oil Ratio.

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Figure 2.14

Decision Tree for Crude Oil Refining and Upgrading

Is there
crude oil refining
or upgrading in the
country?

No

Report‘Not Occurring’

Yes

Is it
possible to estimate
flared and vented
volumes?

Yes

No

If Fugitive
Emissions from Oiland Gas Operations are key
source categories, is the subsource significant?
(Note 1)

Box 1
No

Estimateemissions using a
Tier 1 approach

Yes

Collect data on
venting andflaring
Box 2
Estimate emissions
using a Tier 3
approachNote 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

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Chapter 2

EnergyTABLE 2.15
MAJOR CATEGORIES AND SUBCATEGORIES IN THE OIL AND GAS INDUSTRY
Industry Segment

Sub-Categories

Wells

Drilling
TestingServicingGas Production

Dry Gasa
Sweet Gasb
Sour Gasc

Gas Processing

Sweet Gas Plants
Sour Gas Plants
Deep-cut Extraction Plants

Gas Transmission & Storage

Pipeline Systems
Storage Facilities

Gas Distribution

Rural Distribution
Urban Distribution

Liquefied Gases Transport

Condensate
Liquefied Petroleum Gas (LPG)
Liquefied Natural Gas (LNG) (including associatedliquefaction and gasification facilities)

Oil Production

Conventional Oil
Heavy Oil (Primary Production)
Heavy Oil (Enhanced Production)
Crude Bitumen
Synthetic Crude Oil (From Oilsands)
Synthetic Crude Oil (From Oil Shales)

Oil Upgrading

Crude Bitumen
Heavy Oil

Waste Oil Reclaiming

None

Oil Transport

MarinePipelines
Tanker Trucks and Rail Cars

Oil Refining

Heavy Oil
Conventional and Synthetic Crude Oila

Dry gas is natural gas that does not require any hydrocarbon dew-point control to meet sales gas specifications. However, it may stillrequire treating to meet sales specifications for water and acid gas (i.e. H2S and CO2) content. Dry gas is usually produced from shallow(less than 1000 m deep) gas wells.
b
Sweet gas is natural gas that does not contain any appreciable amount of H2S (i.e. does not require any treatment to meet sales gas
requirements for H2S).
cSour gas is natural gas that must be treated to satisfy sales gas restrictions on H2S content.

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It is good practice to use the Tier 3 approach which will produce the most accurate emissions estimate. However,
the ability to use a Tier 3 approach will depend on the availability of detailed production statistics andinfrastructure data, and it may not be possible to apply it under all circumstances. A Tier 2 (mass balance)
approach is primarily intended for application to oil systems where the majority of the associated and solution
gas production is vented or flared. While much less reliable when applied to oil systems with gas conservation or
to gas systems, a crude mass balance approach based on national production statistics may sometimes offer agreater degree of confidence than that offered by the Tier 1 approach. In such cases, the net balancing term (i.e.
unaccounted-for losses) may be comparable to total fugitive emissions from non-venting or flaring sources. The
Tier 1 approach is susceptible to substantial uncertainties and may easily be in error by an order-of-magnitude ormore. For this reason, it should only be used as a last resort option.

2.7.1.2

C HOICE OF EMISSION FACTORSEmission factors for conducting Tier 2 and Tier 3 assessments are not provided in the IPCC Guidelines due tothe large amount of such information. Moreover, these data are continually being updated to include additional
measurement results and to reflect development and penetration of new control technologies and requirements.
Regular reviews of the literature should be conducted to ensure that the best available factors are being used, andthe references for the chosen values should be clearly documented. Typically, emission factors are developed andpublished by environmental agencies and industry associations, and it will be necessary to develop inventory
estimates in consultation with these organisations.
The selected emission factors must be valid for the given application and be expressed on the same basis as theactivity data. It also may be necessary to apply other types of factors to correct for site and regional differences inoperating conditions and design and maintenance practices, for example:•

Composition profiles of gases from particular oil and gas fields to correct for the amount of CH4, raw CO2
and other target pollutants in the emissions;•

Annual operating hours to correct for the amount of time a source is in active service;•

Efficiencies of the specific control measures used.

The following are additional matters to consider in choosing emission factors:•

It is important to assess the applicability of the selected factors for the target application to ensure
similar/comparable source behaviour and characteristics;•

In the absence of better data, it may sometimes be necessary to apply factors reported for other regions thatpractice similar levels of emission control and feature comparable types of equipment;•

Where measurements are performed to develop new emission factors, only recognised or defensible test
procedures should be applied. The method and quality assurance (QA)/quality control (QC) proceduresshould be documented, the sampled sources should be representative of typical variations in the overallsource population, and a statistical analysis should be conducted to establish the 95% confidence interval on
the average results.

New Tier 1 emission factors are presented in Table 2.16, Refined Tier 1 Emission Factors based on North
American Data. Although still a simplified means of estimating fugitive emissions, the new factors allow for
improved correlation of emissions with commonly-available activity data, and may be expected to limit
uncertainties to within an order of magnitude. The improved correlations are achieved through increased
disaggregation of the industry and, in several cases, by switching to different activity parameters. For example,
fugitive emissions from gas transmission and distribution systems do not correlate well with throughput, and are
better related to lengths of pipeline.
The new factors are derived from detailed emission inventory results for Canada and the United States, and arepresented as examples. Notwithstanding this, these values may be applied to regions outside of North America
that practice similar levels of emissions control and feature comparable types and quality of equipment. Even
where moderate regional differences exist, the new factors may still offer more reliable results than that obtained
from use of the factors given in the IPCC Guidelines. Nonetheless, it is good practice to consider the impact ofregional differences before adopting a specific set of factors. In the absence of data for a particular industry
segment or where conditions in the United States and Canada are not representative, the emission factors given in
the IPCC Guidelines, Reference Manual Tables 1-57, Summary of Methane Emission Factors, and Table 1-58,
Revised Regional Emission Factors for Methane from Oil and Gas Activities should be used.

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EnergyIn general, the developed factors reflect the following practices and state of the oil and gas industry:•

Most associated gas is conserved;•

Sweet waste gas is vented;•

Sour waste gas is flared;•

Many gas transmission companies are voluntarily implementing programmes to reduce methane losses due tofugitive equipment leaks;•

The oil and gas industry is mature and actually in decline in many areas;•

System reliability is high;•Equipment is generally well maintained and high-quality components are used;•Line breaks and well blowouts are rare;•

The industry is highly regulated and these regulations are generally well enforced.

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TABLE 2.16
REFINED TIER 1 EMISSION FACTORS FOR FUGITIVE EMISSIONS FROM OIL AND GAS OPERATIONSBASED ON NORTH AMERICAN DATA
Category

SubCategory

Emission
Type

Default emission factora,bUnits of Measure

CH4

CO2

N2O

Drilling

Allc4.3E-07

2.8E-080

Gg per number of wells drilled

Testing

All2.7E-04

5.7E-03

6.8E-08

Gg per number of wells drilled

ServicingAll

6.4E-05

4.8E-070

Gg/yr per number of producing
and capable wells

All

Fugitivesd

2.6E-03 to
2.9E-03

9.5E-05

0

Gg per 106 m3 gas production

Flaringe

1.1E-05

1.8E-03

2.1E-08

Gg per 106 m3 gas production

Fugitives

6.9E-04 to
10.7E-04

2.7E-05

0

Gg per 106 m3 gas receipts

Flaring

1.3E-05

2.1E-03

2.5E-08

Gg per 106 m3 gas receipts

Fugitives

2.1E-04

2.9E-05

0

Gg per 106 m3 gas receipts

Flaring

2.9E-05

4.6E-03

5.4E-08

Gg per 106 m3 gas receipts

Raw CO2
Venting07.1E-020

Gg per 106 m3 gas receipts

Deep-cut
Extraction
PlantsFugitives

1.0E-05

3.0E-070

Gg per 106 m3 gas receipts

Flaring

6.2E-06

9.7E-04

1.2E-08

Gg per 106 m3 gas receipts

Transmission

Fugitivesf

2.1E-03 to
2.9E-03

1.6E-05

0

Gg per year and per km oftransmission pipeline

Ventingg

0.8E-03 to
1.2E-03

8.5E-06

0

Gg per year and per km oftransmission pipeline

StorageAll

4.3E-04 to
42.0E-04

00

Gg per year and per 106 m3 gas
withdrawals

Gas
Distribution

All

All

5.2E-04 to
7.1E-04

00

Gg per year and per km of
distribution mains

Natural Gas
Liquids
Transport

Condensate

All1.1E-04

7.2E-06

0

Gg per 103 m3 Condensate andPentanes Plus

Liquefied
Petroleum
Gas

All

0

4.3E-04

2.2E-09

Oil
Production

Conventional
Oil

Fugitives

1.4E-03 to
1.5E-03

2.7E-04

0

Gg per 103 m3 conventional oil
production

Venting

6.2E-05 to
270E-05

1.2E-05

0

Gg per 103 m3 conventional oil
production

Flaring

0.5E-05 to
27E-05

6.7E-02

6.4E-07

Gg per 103 m3 conventional oil
production

Fugitives

0.8E-04 to
12E-04

6.7E-06

0

Gg per 103 m3 heavy oil
production

Venting

2.1E-02 to
2.7E-02

5.0E-05

0

Gg per 103 m3 heavy oil
production

Flaring

0.5E-04 to
2.0E-04

4.9E-02

4.6E-07

Gg per 103 m3 heavy oil
production

Wells

Gas
Production

Gas
Processing

Sweet Gas
PlantsSour Gas
Plants

Gas
Transmission& Storage

Heavy Oil2.86

Gg per 103 m3 LPG

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Chapter 2

EnergyTABLE 2.16 (CONTINUED)REFINED TIER 1 EMISSION FACTORS FOR FUGITIVE EMISSIONS FROM OIL AND GAS OPERATIONSBASED ON NORTH AMERICAN DATA
SubCategory

Emission
Type

Default emission factora,b
CH4

CO2

N2O

Crude
Bitumen

Fugitives

1.0E-04

1.2E-04

0

Gg per 103 m3 crude bitumen
production

Venting

1.0E-03

1.2E-030

Gg per 103 m3 crude bitumen
production

Flaring

8.8E-05

2.2E-02

2.4E-07

Gg per 103 m3 crude bitumen
production

Synthetic
Crude (fromOilsands)

All

2.3E-0300

Gg per 103 m3 synthetic crude
production from oilsands

Synthetic
Crude (fromOil Shale)

All

NA

NA

NA

Gg per 103 m3 synthetic crude
production from oil shale

Oil
Upgrading

All

All

ND

ND

ND

Gg per 103 m3 oil upgraded

Oil Transport

Pipelines

All

5.4E-06

4.9E-070

Gg per 103 m3 oil transported bypipeline

TankerTrucks andRail Cars

Venting

2.5E-05

2.3E-06

0

Gg per 103 m3 oil transported by
Tanker Truck

Loading ofOff-shore
Production
on Tanker
Ships

Venting

NAh

NAh

NAh

Gg per 103 m3 oil transported by
Tanker Truck

Category

Oil
Production(continued)

Units of Measure

NA - Not Applicable ND - Not DeterminedaWhile the presented emission factors may all vary appreciably between countries, the greatest differences are expected to occur withrespect to venting and flaring, particularly for oil production due to the potential for significant differences in the amount of gas
conservation and utilisation practised.
b
The range in values for fugitive emissions is attributed primarily to differences in the amount of process infrastructure (e.g. average
number and sizes of facilities) per unit of gas throughput.
c‘All’ denotes all fugitive emissions as well as venting and flaring emissions.
d‘Fugitives’ denotes all fugitives emissions including those from fugitive equipment leaks, storage losses, use of natural gas as the
supply medium for gas-operated devices (e.g. instrument control loops, chemical injection pumps, compressor starters, etc.), and ventingof still-column off-gas from glycol dehydrators.
e‘Flaring’ denotes emissions from all continuous and emergency flare systems. The specific flaring rates may vary significantly between
countries. Where actual flared volumes are known, these should be used to determine flaring emissions rather than applying thepresented emission factors to production rates. The emission factors for direct estimation of CH4, CO2 and N2O emissions from reported
flared volumes are 0.012, 2.0 and 0.000023 Gg, respectively, per 106 m3 of gas flared based on a flaring efficiency of 98% and a typicalgas analysis at a gas processing plant (i.e. 91.9% CH4, 0.58% CO2, 0.68% N2 and 6.84% non-methane hydrocarbons by volume).
f
The larger factor reflects the use of mostly reciprocating compressors on the system while the smaller factor reflects mostly centrifugal
compressors.
g‘Venting’ denotes reported venting of waste associated and solution gas at oil production facilities and waste gas volumes fromblowdown, purging and emergency relief events at gas facilities. Where actual vented volumes are known, these should be used todetermine venting emissions rather than applying the presented emission factors to production rates. The emission factors for direct
estimation of CH4 and CO2 emissions from reported vented volumes are 0.66 and 0.0049 Gg, respectively, per 106 m3 of gas vented
based on a typical gas analysis for gas transmission and distribution systems (i.e. 97.3% CH4, 0.26% CO2, 1.7% N2 and 0.74% nonmethane hydrocarbons by volume).
hWhile no factors are available for marine loading of offshore production for North America, Norwegian data indicate a CH4 emission
factor of 1.0 to 3.6 Gg/103 m3 of oil transferred (derived from data provided by Norwegian Pollution Control Authority, 2000).
Sources: Canadian Association of Petroleum Producers (1999); GRI/US EPA (1996); US EPA (1999).

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2.7.1.3

C HOICE OF ACTIVITY DATA

The activity data required to estimate fugitive emissions from oil and gas activities may include production
statistics, infrastructure data (e.g. inventories of facilities/installations, process units, pipelines, and equipment
components), and reported emissions from spills, accidental releases, and third-party damages. The basic activity
data required for each tier and each type of primary source are summarised in Table 2.17, Typical Activity Data
Requirements for each Assessment Approach by Type of Primary Source Category. Specific matters to consider
in compiling this information include the following:•

Production statistics should be disaggregated to capture changes in throughputs (e.g. due to imports, exports,
reprocessing, withdrawals, etc.) in progressing through oil and gas systems.

•

Production statistics or disposition analyses24 may not agree between different reporting agencies eventhough they are based on the same original measurement results (e.g. due to possible differences interminology and potential errors in summarising these data). These discrepancies may be used as anindication of the uncertainty in the data. Additional uncertainty will exist if there is any inherent bias in theoriginal measurement results (for example, sales meters are often designed to err in favour of the customer,
and liquid handling systems will have a negative bias due to evaporation losses). Random metering andaccounting errors may be assumed to be negligible when aggregated over the industry.

•

Production statistics provided by national bureaux should be used in favour of those available frominternational bodies, such as the IEA or the UN, due to their generally better reliability and disaggregation.
Regional, provincial/state and industry reporting groups may offer even more disaggregation.

•

Reported vented and flared volumes may be highly suspect since these values are usually estimates and notbased on actual measurements. Additionally, the values are often aggregated and simply reported as flared
volumes. Operating practices of each segment of the industry should be reviewed to determine if the reported
volumes are actually vented or flared, or to develop appropriate apportioning of venting relative to flaring.
Audits or reviews of each industry segment should also be conducted to determine if all vented/flared
volumes are actually reported (for example, solution gas emissions from storage tanks and treaters,
emergency flaring/venting, leakage into vent/flare systems, and blowdown and purging volumes may notnecessarily be accounted for).

•

Infrastructure data are more difficult to obtain than production statistics. Information concerning thenumbers and types of major facilities and the types of processes used at these facilities may often be
available from regulatory agencies and industry groups, or directly from the actual companies.

•

Information on minor facilities (e.g. numbers of field dehydrators and field compressors) usually is notavailable, even from oil and gas companies. Consequently, assumptions must be made, based on local design
practices, to estimate the numbers of these facilities. This may require some fieldwork to develop
appropriate estimation factors or correlations.

•

Many companies use computerised inspection-and-maintenance information management systems. Thesesystems can be a very reliable means of counting major equipment units (e.g. compressor units, process
heaters and boilers, etc.) at selected facilities. Also, some departments within a company may maintaindatabases of certain types of equipment or facilities for their own specific needs (e.g. tax accounting,production accounting, insurance records, quality control programmes, safety auditing, license renewals,etc.). Efforts should be made to identify these potentially useful sources of information.

24 A disposition analysis provides a reconciled accounting of produced hydrocarbons from the wellhead, or point of receipt,

through to the final sales point or point of export. Typical disposition categories include flared/vented volumes, fuel usage,
system losses, volumes added to/removed from inventory/storage, imports, exports, etc.

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Chapter 2

EnergyTABLE 2.17
TYPICAL ACTIVITY DATA REQUIREMENTS FOR EACH ASSESSMENT APPROACH FOR FUGITIVE EMISSIONS FROM OIL ANDGAS OPERATIONS BY TYPE OF PRIMARY SOURCE CATEGORY
Assessment Tier

Primary Source Category

Minimum Required Activity Data

1All

Oil and Gas Throughputs

2

Oil Systems

Gas to Oil Ratios
Flared and Vented Volumes
Conserved Gas Volumes
Reinjected Gas Volumes
Utilised Gas Volumes
Gas Compositions

3

Process Venting/Flaring

Reported Volumes
Gas Compositions
Proration Factors for Splitting Venting from Flaring

Storage Losses

Solution Gas Factors
Liquid Throughputs
Tank Sizes
Vapour Compositions

Equipment Leaks

Facility/Installation Counts by Type
Processes Used at Each Facility
Equipment Component Schedules by Type of Process Unit
Gas/Vapour Compositions

Gas-Operated Devices

Schedule of Gas-operated Devices by Type of Process Unit
Gas Consumption Factors
Type of Supply Medium
Gas Composition

Accidental Releases & ThirdParty Damages

Incident Reports/Summaries

Gas Migration to the Surface& Surface Casing Vent Blows

Average Emission Factors & Numbers of Wells

Drilling

Number of Wells Drilled
Reported Vented/Flared Volumes from Drill Stem Tests
Typical Emissions from Mud Tanks

Well Servicing

Tally of Servicing Events by Types

Pipeline Leaks

Type of Piping Material
Length of Pipeline

Exposed Oilsands/Oil Shale

Exposed Surface Area
Average Emission Factors

Component counts by type of process unit may vary dramatically between facilities and countries due todifferences in design and operating practices. Thus, while initially it may be appropriate to use values reported in
the general literature, countries should strive to develop their own values.
Use of consistent terminology and clear definitions is critical in developing counts of facilities and equipment
components, and to allow any meaningful comparisons of the results with others.

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Some production statistics may be reported in units of energy (based on their heating value) and will need to beconverted to a volume basis, or vice versa, for application of the available emission factors. Typically, where
production values are expressed in units of energy, it is in terms of the gross (or higher) heating value of the
product. However, where emission factors are expressed on an energy basis it is normally in terms of the net (orlower) heating value of the product. To convert from energy data on a GCV basis to a NCV basis, theInternational Energy Agency assumes a difference of 5% for oil and 10% for natural gas. Individual natural gas
streams that are either very rich or high in impurities may differ from the average value given above. Emission
factors and activity data must be consistent with each other.
In comparing fugitive emissions from the oil and gas industry in different countries it is important to consider the
impact of oil and gas imports and exports, as well as the types of oil and gas activities and the levels of emission
control. Otherwise, emissions viewed on either a per-unit-consumption or a per-unit-production basis will be
misleading.
Production activities will tend to be the major contributor to fugitive emissions from oil and gas activities incountries with low import volumes relative to consumption and export volumes. Gas transmission anddistribution and petroleum refining will tend to be the major contributors to these emissions in countries withhigh relative import volumes. Overall, net importers will tend to have lower specific emissions than net exporters.

2.7.1.4

C OMPLETENESS

Completeness is a significant issue in developing an inventory of fugitive emissions for the oil and gas industry.
It can be addressed through direct comparisons with other countries and, for refined inventories, throughcomparisons between individual companies in the same industry segment and subcategory. This requires use of
consistent definitions and classification schemes. In Canada, the upstream petroleum industry has adopted abenchmarking scheme that compares the emission inventory results of individual companies in terms of
production-energy intensity and production-carbon intensity. Such benchmarking allows companies to assess
their relative environmental performance. It also flags, at a high level, anomalies or possible errors that should be
investigated and resolved.
The indicative factors presented in Table 2.18 may be used to help assess completeness and to qualify specificmethane losses as being low, medium or high. Specific methane losses which are appreciably less than the low
benchmark or greater than the high benchmark should be explained. The ranking of specific methane losses
relative to the presented activity data should not be used as a basis for choosing the most appropriate assessment
approach; rather, total emissions (i.e. the product of activity data and emission factors), the complexity of theindustry and available assessment resources should all be considered.

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Chapter 2

EnergyTABLE 2.18
CLASSIFICATION OF GAS LOSSES AS LOW, MEDIUM OR HIGH AT SELECTED TYPES OF NATURAL GAS FACILITIES
Yearly emission factors
Low

MediumHigh

Units ofMeasureNet gas production (i.e. marketed
production)

0.05

0.2

0.7

% of netproduction

Transmission
Pipeline Systems

Length of transmission pipelines

200

2 000

20 000m3/km/yr

Compressor
Stations

Installed compressor capacity

6 000

20 000100 000

m3/MW/yr

Underground
Storage

Working capacity of undergroundstorage stations

0.05

0.1

0.7

% of working
gas capacity

LNG Plant(liquefaction orregasification)

Gas throughput

0.005

0.05

0.1

% of throughput

Meter and
Regulator Stations

Number of stations

1 000

5 000

50 000m3/station/yr

Distribution

Length of distribution network

100

1 000

10 000m3/km/yr

Gas UseNumber of gas appliances

2

5

20

Facilities

Activity data

Production andProcessing

m3/appliance/yr

Source: Adapted from currently unpublished work by the International Gas Union, and based on data for a dozen countries including
Russia and Algeria.

Smaller individual sources, when aggregated nationally over the course of a year, may often be significant total
contributors. Therefore, good practice is not to disregard them unless their collective contribution to total
fugitive emissions is proven to be negligible. Conversely, once a thorough assessment has been done, a basis
exists for simplifying the approach and better allocating resources in the future to best reduce uncertainties in the
results.

2.7.1.5

D EVELOPING A CONSISTENT TIME SERIES

Ideally, emission estimates will be prepared for the base year and subsequent years using the same method.
Where some historical data are missing it should still be possible to use source-specific measurements combinedwith backcasting techniques to establish an acceptable relationship between emissions and activity data in thebase year. Approaches for doing this will depend on the specific situation, and are discussed in general terms in
Chapter 7, Methodological Choice and Recalculation, Section 7.3.2.2, Alternative Recalculation Techniques.
While establishing base year emission levels is meaningful and important at a regional or national level, it isoften a misleading indicator at the company level due to frequent mergers, divestitures and acquisitions in many
areas. This may be an issue where national inventories are developed based on a rollup of company-level
inventories, and some extrapolations or interpolations are required.
Where changes in methods and emission factors are substantial, the whole time series should be recalculated andreported in a transparent manner.

2.7.1.6

U NCERTAINTY ASSESSMENT

Sources of error occur in the following areas:•

Measurement errors;•

Extrapolation errors;•

Inherent uncertainties of the selected estimation techniques;•

Missing or incomplete information regarding the source population and activity data;

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Poor understanding of temporal and seasonal variations in the sources;•

Over or under accounting due to confusion or inconsistencies in category divisions and source definitions;•

Misapplication of activity data or emission factors;•

Errors in reported activity data;•

Missed accounting of intermediate transfer operations and reprocessing activities (e.g. repeat dehydration ofgas streams [in the field, at the plant, and following storage], treating of slop and foreign oil receipts) due topoor or no documentation of such activities;•

Variances in the effectiveness of control devices and missed accounting of control measures;•

Data-entry and calculation errors.

Due to the complexity of the oil and gas industry, it is difficult to quantify the net uncertainties in the overall
inventories, emission factors and activity data. While some semi-quantitative analyses have been conducted, amore thorough quantitative analysis is warranted.
High-quality refined emissions factors for most gases may be expected to have errors in the order of ±25
percent.25 Factors based on stochiometric ratios may be much better (e.g. errors of ±10%). Gas compositions areusually accurate to within ±5% on individual components. Flow rates typically have errors of ±3% or less forsales volumes and ±15% or more for other volumes.
A high-quality bottom-up (Tier 3) inventory of fugitive methane losses from either oil or gas activities might be
expected to have errors of ±25 to ±50%. In comparison, default production-based emission factors for methane
losses may easily be in error by an order of magnitude or more. Inventories of fugitive CH4 and CO2 emissions
from venting and flaring activities will be quite reliable if the raw gaseous composition and actual vented andflared volumes are accurately known. Estimates of fugitive N2O emissions will be least reliable but will only be aminor contributor to total fugitive greenhouse gas emissions from oil and gas activities.
Estimates of emission reductions from individual control actions may be accurate to within a few percent to±25% depending on the number of subsystems or sources considered.

2.7.2 Reporting and documentation
It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Section 8.10.1 of Chapter 8, Quality Assurance and Quality Control.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates aretransparent and steps in their calculation may be retraced.
Some examples of specific documentation and reporting relevant to this source category are provided below.
Documentation is particularly important where a Tier 3 approach is used since the IPCC Guidelines do notdescribe a standard Tier 3 approach for the oil and gas sector. There is a wide range in what potentially may beclassified as a Tier 3 approach, and correspondingly, in the amount of uncertainty in the results.
If available, summary performance and activity indicators should be reported to help put the results inperspective (e.g. total production levels and transportation distances, net imports and exports, and specificenergy, carbon and emission intensities). Reported emission results should also include a trend analysis to showchanges in emissions and activity data over time. The expected accuracy of the results should be stated and theareas of greatest uncertainty clearly noted. This is critical for proper interpretation of the results and any claimsof net reductions.
The current trend by some government agencies and industry associations is to develop detailed methodology
manuals and reporting formats for specific segments and subcategories of the industry. This is perhaps the mostpractical means of maintaining, documenting and disseminating the subject information. However, all suchinitiatives must conform to the common framework established in the IPCC Guidelines so that the emission
results can be compared across countries.

25 The percentages cited in this section represent an informal polling of assembled experts aiming to approximate the 95%
confidence interval around the central estimate.

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EnergySince emission factors and estimation procedures are continually being improved and refined, it is possible forchanges in reported emissions to occur without any real changes in actual emissions. Accordingly, the basis forany changes in results between inventory updates should be clearly discussed and those due strictly to changes inmethods and factors should be highlighted.
The issue of confidential business information will vary from region to region depending on the number of firms
in the market and the nature of the business. The significance of this issue tends to increase in progressing
downstream through the oil and gas industry. A common means to address such issues where they do arise is toaggregate the data using a reputable independent third party.

2.7.3

Inventory quality assurance/quality control(QA/QC)

It is good practice to conduct quality control checks as outlined in Chapter 8, Quality Assurance and Quality
Control, Table 8.1, Tier 1 General Inventory Level QC Procedures, and expert review of the emission estimates.
Additional quality control checks as outlined in Tier 2 procedures in Chapter 8 and quality assurance procedures
may also be applicable, particularly if higher tier methods are used to determine emissions from this source
category. Inventory agencies are encouraged to use higher tier QA/QC for key source categories as identified in
Chapter 7, Methodological Choice and Recalculation.
In addition to the guidance in Chapter 8, specific procedures of relevance to this source category are outlined
below.
Emission inventories for large, complex oil and gas industries will be susceptible to significant errors due tomissed or unaccounted sources. To minimise such errors, it is important to obtain active industry involvement in
the preparation and refinement of these inventories.
Review of direct emission measurements
If direct measurements are used to develop country-specific emission factors, the inventory agency should
establish whether measurements at the sites were made according to recognised standard methods. If themeasurement practices fail this criterion, then the use of these emissions data should be carefully evaluated,
estimates reconsidered, and qualifications documented.
Emission factors check
The inventory agency should compare measurement-based factors to IPCC default factors and factors developedby other countries with similar industry characteristics. If IPCC default factors are used, the inventory agency
should ensure that they are applicable and relevant to the category. If possible, the IPCC default factors should becompared to national or local data to provide further indication that the factors are applicable.
Activity da ta check
Several different types of activity data may be required for this source category, depending on which method isused. The inventory agency should check different types of activity data against each other to assess
reasonableness. Where possible, multiple sources of data (i.e. from national statistics and industry organisations)should be compared. Significant differences in data should be explained and documented. Trends in main
emission drivers and activity data over time should be checked and any anomalies investigated.
External review
Emission inventories for large, complex oil and gas industries will be susceptible to significant errors due tomissed or unaccounted for sources. To minimise such errors, it is important to obtain active industry involvementin the preparation and refinement of these inventories.

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REFERENCES
NON-CO 2 EMISSIONS FROM STATIONARY COMBUSTION
EMEP/CORINAIR (1999). Atmospheric Emission Inventory Guidebook, 2nd edition. European Environment
Agency, Copenhagen, Denmark.
Intergovernmental Panel on Climate Change (IPCC) (1997). Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories, J.T. Houghton et al., IPCC/OECD/IEA, Paris, France.
Smith, K.R., Pennise D.M., Khummongkol P., Chaiwong V., Ritgeen K.., Zhang J., Panyathanya W., Rasmussen
R.A., Khalil M.A.K., and Thorneloe S.A. (1999). Greenhouse Gases from Small-scale Combustion Devices
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Environmental Protection Agency, Office of Research and Development, Washington, D.C., USA.
Smith K.R., Uma R., Kishore V.V.N., Lata K., Joshi V., Zhang J., Rasmussen R.A. and Khalil M.A.K. (2000).
Greenhouse Gases from Small-scale Combustion Devices in Developing Countries, Phase IIa: Household
Stoves in India. EPA-600/R-00-052. U.S. Environmental Protection Agency, Office of Research andDevelopment, Washington, D.C., USA.
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S.A. (1999). ‘Carbon monoxide from cookstoves in developing countries: 1. Emission factors’.
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Zhang J., Smith K.R., Uma R., Ma Y., Kishore V.V.N., Lata K., Khalil M.A.K., Rasmussen R.A., and Thorneloe
S.A. (1999). ‘Carbon monoxide from cookstoves in developing countries: 2. Potential chronic exposures’.
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Zhang J. and Smith K.R. (1999). ‘Emissions of carbonyl compounds from various cookstoves in China’.
Environmental Science and Technology, 33 (14), pp. 2311-2320.

MOBILE COMBUSTION: AIRCRAFT
ANCAT/EC2 (1998). ANCAT/EC2 Global Aircraft Emissions Inventories for 1991/92 and 2015. R. M. Gardner,
report by the ECAC/ANCAT and EC Working Group, ECAC-EC, ISBN 92-828-2914-6.
Baughcum S. L., Tritz T. G., Henderson S. C. and Pickett D. C. (1996). Scheduled Civil Aircraft Emission
Inventories for 1992: Database Development and Analysis. NASA Contractor Report 4700.
Daggett, D.L. et al. (1999). An Evaluation of Aircraft Emissions Inventory Methodology by Comparison With
Reported Airline Data. NASA CR-1999-209480, NASA Center for AeroSpace Information, 7121 Standard
Drive, Hanover, MD 21076-1320, USA.
EMEP/CORINAIR (1999). Atmospheric Emission Inventory Guidebook, 2nd edition. European Environment
Agency, Copenhagen, Denmark.
Falk (1999). Estimating The Fuel Used And NOx Produced From Civil Passenger Aircraft From ANCAT/EC2
Inventory Data. Report No DTI/EID3c/199803, Department of Transport and Industry, UK.
Falk (1999b). Estimating the fuel used and NOx produced from civil passenger aircraft from ANCAT/EC2
inventory data. Table 2 of DTI Report DTI/EID3c/199803, Department of Transport and Industry, UK.
ICAO (1997). Statistics Division - Report of the Ninth Session, Montreal, 22-26 September 1997. Document no.
9703, STA/9 (1997) International Civil Aviation Organization, Montreal, Canada, 1998.
Intergovernmental Panel on Climate Change IPCC (1997). Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories, J.T. Houghton et al., IPCC/OECD/IEA, Paris, France.
IPCC (1999). Aviation and the Global Atmosphere. Intergovernmental Panel on Climate Change, Cambridge
University Press, Cambridge, UK.
Olivier J.G.J. (1995). Scenarios for Global Emissions from Air Traffic. Report No. 773 002 003, National
Institute of Public Health and Environment (RIVM), Bilthoven, The Netherlands.

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EnergyUNFCCC (1999). Methods Used To Collect Data, Estimate And Report Emissions From International Bunker
Fuels. Draft report from the secretariat to the United Nations Framework Convention on Climate Change,
April 21 1999.

FUGITIVE EMISSIONS FROM COAL MINING AND HANDLINGIntergovernmental Panel on Climate Change (IPCC) (1997). Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories, J.T. Houghton et al., IPCC/OECD/IEA, Paris, France.
Riemer P. (1999). ‘Technologies for Abatement of Methane Emissions’. Methane emissions from coal mining,
Volume 1, Chapter 4, IEAGHG/SR7, restricted circulation.
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37-42.
Williams, D. J., Saghafi, A., Lange, A. L. and Drummond, M. S. (1993). Methane emissions from open-cut minesand post-mining emissions from underground coal. CET/IR 173, CSIRO Division of Coal and Energy
Technology, unrestricted investigation report to the Department of Environment, Sports and Territories,
Australia.

FUGITIVE EMISSIONS FROM OIL AND GAS OPERATIONSCanadian Association of Petroleum Producers (1999). CH4 and VOC Emissions from the Canadian Upstream Oiland Gas Industry. Canadian Association of Petroleum Producers, Calgary, AB, Canada.
GRI/US EPA (1996). Methane Emissions from the Natural Gas Industry. Report No. EPA-600/R-96-080, GRI /United States Environmental Protection Agency.
Intergovernmental Panel on Climate Change (IPCC) (1997). Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories, J.T. Houghton et al., IPCC/OECD/IEA, Paris, France.
USEPA (1999). Methane Emissions from the U.S. Petroleum Industry. EPA Report No. EPA-600/R-99-010, p.
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