Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

CO2 EMISSIONS FROM STATIONARYCOMBUSTION OF FOSSIL FUELSA C K N O WL E D G E M E N T S
This paper was written by Tim Simmons (Avonlog Limited, UK).

ABSTRACTGood practice in inventory construction constitutes a body of approaches and procedures which facilitate thepreparation of inventories which are accurate, comparable and transparent. However, the good practice must be
conducted within a framework of a sound appreciation of the sources of data, their strengths and weaknesses andthe methods available.
This paper sets out the elements of the main methodologies for estimating emissions and discusses the data
availability and its consequences for the choice of method. It also describes the checks available within thesources of activity data and reviews the default values available from the Revised 1996 IPCC Guidelines for
National Greenhouse Gas Inventories (IPCC Guidelines).
At appropriate points within the discussion, estimates are given of the levels of uncertainty to be associated withthe main aggregates of activity data, calorific values and emission factors. These are mostly the result ofexperience and judgement rather than rigorous analysis.
The paper closes with a brief discussion of the assessment of inventory quality and the use of the Reference
Approach as a check on estimates prepared using other methods.

CO2 Emissions from Stationary Combustion of Fossil Fuels

15

Background Paper

1

INTRODUCTION

Anthropogenic emissions of carbon dioxide (CO2) weighted by global warming potentials, constitute by far, thelargest part of the emissions of greenhouse gases. Of these CO2 emissions, those that are produced from fuelcombustion make up the great majority and, almost all, may be directly and immediately estimated from the
combustion activities. Good quality estimates of CO2 emissions from fuel combustion are not only essential forthe construction of inventories and the monitoring of emission control obligations but, because of the potential
control measures implicit in the direct link between fuel use and emissions, the estimates are invaluable for the
preparation and analysis of emission abatement policies.
Simple methods for estimation of CO2 emissions from the use of fuels assume that the carbon in the fuel used foreach activity will enter the atmosphere in the short or long term. Short-term emissions are defined within the
IPCC Guidelines as those occurring within twenty years of the fuel use and are almost entirely reported in thefuel combustion module. Long-term CO2 emissions result from the final oxidation of long-life materials
manufactured from fuel carbon and are usually emissions from waste destruction. Tier 1 methods comprise theReference Approach (RA) and the Sectoral Approach (SA) and both estimate the amount of carbon released into
the atmosphere and express it as CO2. In fact, whilst the great majority of the emissions are CO2 others arecarbon monoxide (CO), methane (CH4) and non-methane volatile organic compounds (NMVOCs). The two
approaches are termed “top-down” because they estimate the eventual carbon emissions from the supply of fuels
to the economy or the main economic sectors rather than from the fuel consumption or actual emissions at
combustion plant.
More detailed (“bottom-up”) methods do not depart from the principle of estimating emissions from the carbon
content of the fuel but, as far as possible, use figures for the amounts of fuel consumed at individual large
combustion plants together with details of fuel supplies to other sources of emissions.

1.1

Sources of emissions and related data

Carbon and hydrogen in fossil fuels are used widely for heat raising and as raw materials for the manufacture ofother products. Carbon may also be used as a reducing agent and a few fuel products are used for their physicalproperties. The heat raising activity generates immediate emissions of CO2 as do the majority of activities which
use carbon as a reducing agent. Carbon used directly in the manufacture of other products and fuel products used
for their physical properties contribute mainly to the long-term emissions although some part of the fuel products
may be oxidised in use (for example, lubricants).
This paper is limited to the estimation of emissions from activities using stationary combustion plant. The
emissions form part of the total from fuel combustion reported under the activities classified under section 1A of
the Source/Sink categories given in Vol 1 of the IPCC Guidelines. By definition, emissions from mobile sources
should be excluded. However, this is not always possible because mobile sources cannot be excluded when using
the Reference Approach (RA) and may be only partly excluded when using the Sectoral Approach (SA) as theactivity data may conceal some fuel use in mobile plant.
The widespread use of fuel combustion in all human activities means that all sectors of economic activity andhouseholds are involved. The magnitude of the number of individual emission sources prevents any direct
assessment of the emissions from each source. However, the distribution of the number of sources with a given
quantity of emissions is very skewed with a large number of small emitters and relatively few large emitters. The
few large emitters account for the majority of the emissions. This permits a separation of the estimation problem
into a census or near census of the large emitters and sampling or indirect methods for the rest.

2

METHODS AVAILABLE

The extent to which the problem of estimation of emissions can, in practice, be separated into the two groups
mentioned above is very dependent on the data available and, in particular, the activity data. If few activity data are
available, then simple Tier 1 methods must be used. The RA is based on relatively few fossil fuel supply data whilst
the SA uses figures for deliveries to the main consuming sectors (main source categories). Where a country has
detailed information on the consumption of fuels in the main consuming activities or sectors then detailed, “bottom

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

up” calculation can be made. Figures for the consumption of fuels by an enterprise will, in general, differ from thedeliveries to it by the extent to which the enterprise builds or draws upon stocks of the fuels.
Whichever method is used the underlying equation is:
EQUATION 1
Cr = Q ● NCV ● EF ● (1-Sf) ● F
Where:
Cr:

quantity of carbon released and attributed to fuel combustion (multiply by 44/12 for CO2)

Q:

quantity of fuel delivered to or consumed by the activity (sector) expressed in natural units

NCV: net calorific value of fuel (TJ/natural unit)EF:emission factor (more precisely, the specific carbon content, t C/TJ)

Sf:carbon storage factor, that is the fraction of carbon delivered which remains unoxidised after useof the fuel either in a product manufactured from it or because the use does not involve deliberateoxidation of the carbon content.

F:

is the oxidation factor, the fraction of carbon which is oxidised during combustion.

“Bottom up” methods may use emission factors expressed as t C/natural unit and obviate the need for net
calorific values.
Tier 1 methods are the simplest to use but less accurate than the more detailed analyses where good andwidespread consumption data are available. The Reference Approach makes relatively few demands for data but
interpreting its results requires care and an understanding of the carbon flows into and from the country. This isdiscussed more fully at the close the paper under Inventory Quality.

2.1

The reference approach

The Reference Approach was introduced to provide simple estimates for CO2 emissions from fuel combustion for
countries which have insufficient data for the Sectoral Approach or for methods based on detailed analyses offuel consumption. The RA may also be useful as check on the completeness of emission estimates obtained byaggregating estimates for many combustion activities. The RA estimates fossil carbon flow into the economy andadjusts it for carbon stored in long-life materials and for any carbon not oxidised during combustion. Carbon in
bio-fuels is omitted from the accounting but reported for information. The RA provides estimates of CO2 from allfuel combustion and some fugitive emissions. It also offers a breakdown of emissions by main fuel type but theways in which fuels are used are not identifiable as stationary combustion, in particular, and emissions from themain source categories cannot be separately estimated. National fuel supply statistics are used to calculate thecarbon flows. Both fugitive and combustion emissions resulting from transport and use of these flows areincluded. Fuel supplies to a country are calculated using the following formula:(Production) + imports - exports ± stock change
for each fuel in turn. Production is included only for primary fuels (see the IPCC Guidelines Vol. 3).
Since the supply, so defined, should balance consumption this expression is referred to as the “apparent
consumption” and may be used in place of Q in the formula above. The figures for carbon release from each of
the fuels are summed to form the estimate of total emissions.
The relatively few but not insignificant flows of carbon outside the boundaries of the energy statistics systemshould be recognised and, where possible, should be taken into account when the RA is used as check against
other estimation methods. The most notable flows are fugitive carbon releases from oil, gas and coal extraction
activities as these usually occur before the measurement of production and are not, therefore, included in energy
statistics but under category 1B, Fugitive Emissions from Fuels. The flows of carbon resulting from imports andexports of basic organic chemicals and closely related intermediates are not part of the energy statistics but
contribute to some short-term and long-term carbon release during their use in the petro-chemicals industry andat their final destruction. There are no procedures at present for estimating their contribution through Tier 1
methods but studies of non-energy use of fossil carbon and its eventual fate are taking place in order to improvecarbon accounting in this difficult area.

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Background Paper

2.2

The sectoral approach

The RA does not provide estimates of emissions from the main groups of fuel using activities and, as suchinformation is essential for monitoring and abatement of emissions, the identical “top-down” principle has been
applied to deliveries of fuels to the main source categories defined in the IPCC Guidelines Vol 1. The method has
been introduced into the IPCC Guidelines as the Tier 1 method, Sectoral Approach (SA). CO2 emissions fromthe sources other than transport may be estimated separately in Tier 1 and considered broadly equivalent toemissions from stationary combustion. However, as transport vehicles are only part of the set of mobile emitters
this equivalence is not entirely correct.
The SA method uses the deliveries or consumption of fuels to each of the main source categories together with
their carbon content to estimate the emissions of CO2 from them.

2.3

Detailed technology-based method

Commonly known as the “bottom-up” method, this estimates emissions from detailed consumption data at plantlevel, at least for the larger combustion plant. The estimations are generally very good and are able todiscriminate clearly between stationary and mobile combustion sources because of the detailed work involved in
identifying and tabulating all main sources of emissions and the resources required to bring together thenecessary data from various sources. For smaller sources and those which are spatially distributed over a wide
area the method usually uses estimates based on deliveries data. Therefore for these cases, it resembles the
Sectoral Approach.

3

DATA AVAILABILITY AND QUALITY ISSUES

3.1
3.1.1

Activity data
Reference approach

National fuel supply statistics, needed for the RA, are usually readily available from the national energy publications.
These data are also published by the United Nations, International Energy Agency and Eurostat for most of thecountries in the world. However, national statistics should be used wherever possible because those who compile
them can explain their provenance and their limitations. Equally, national definitions of production or stocks may
differ from those employed by international organisations and these differences may create difficulties when
justifying the subsequent inventories. Those persons who prepare a Reference Approach estimate of CO2 should beaware of the basis for measurement of production and external trade figures. For example, natural gas production
statistics may be taken from field production measured whilst the gas still contains “liquids” (ethane, propane andbutane) which are largely removed before sale and distribution. Some countries will also include gases vented and/or
flared although it is more usual to exclude these quantities from production and take account of emissions from themseparately. Clearly the nature of the production measurement process has implications for the calorific value andemission factor employed when estimating the emissions.
There are, in general, two sources for figures of imports and exports. These are the national customs service (whocollect the data as a by-product of their functions of controlling and taxing traded fuels) and companies who are
the importers or exporters of the fuels. One or other of the sources will be better for different fuels. Nationalenergy statisticians can advise as they will have based the published data on their assessments of the relative
strengths of the available data.

3.1.2

Sectoral approach

For countries which have the necessary data, the SA is to be preferred to the RA as it produces estimates ofemissions by the main source categories defined in the IPCC Guidelines. With some important exceptions, theSA estimates emissions using the quantities of fuels delivered into the main source categories as the variable Q inequation 1 above. The deliveries data are usually provided by the fuel supply industries. The exceptions concern
certain of the large energy conversion industries and major consumers (for example, iron and steel) who report
directly their consumption. When deliveries data are used, the estimate encompasses not only CO2 emissions but
emissions of other carbon bearing molecules whether from fuel combustion or fugitive release within theenterprises. With only two exceptions (autogeneration and non-energy use) it does not enquire further into the18

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

reasons for fuel use within the source categories. If a country applies the Tier 1 method for fuel combustion andthe methods described in the Industrial Processes module of the IPCC Guidelines then the country should takecare to avoid double counting certain CO2 emissions. The areas of potential overlap between the methods aredescribed later and also mentioned in the relevant parts of the Industrial Processes module.
Collecting data for the deliveries and/or the consumption of fuels in the energy industries requires data systems
which are matched to the types of industry, the processes they undertake and the data they have available.
Similarly, the information on deliveries made to other source categories by the energy supply industries willreflect their methods for accounting for sales and classification of customers. Some countries conduct directsurveys of consumption in the larger enterprises on a yearly or longer regular basis and this information is“grossed-up” to national total. A good understanding of the conditions of reporting and subsequent validation andprocessing by the energy statisticians is essential for intelligent use of the data.
The main source categories used and for which worksheets are provided in the IPCC Guidelines are:•Energy industries;•

Manufacturing and construction;•

Transport;•

Commercial and Institutional;•

Residential;•

Agriculture, Forestry and Fishing, and•Other.

The economic activities contained within the main source categories are listed in the annex to this paper.
Countries which rely heavily on statistics of deliveries from suppliers of fuels will be conscious of thepossibilities for misallocation of deliveries between main source categories and the weaknesses of identifying
final consumers when direct importing of fuels takes place. The problems affect coal and oil in particular and thecommercial and household categories. These are often served by wholesalers whose receipts from suppliers
represent the last point of reporting (the downstream statistical boundary) for coal and oil in theses sectors.
Misallocation of deliveries to categories is revealed only when independent surveys of consumption are
undertaken and the extent of the problem can then be estimated.
The fuels covered by the SA method are given on the worksheets for each main source category. The fuels fall
naturally into two groups, “traded” and “non-traded” although some fuels may belong to both groups (fuelwood)and the groupings will depend on the country.
In the industrialised countries, total deliveries of the traded fuels is well known and, subject to the reservations
expressed in the preceding section, figures for the amounts going to each of the main source categories canusually be determined. In less developed countries, estimates are usually available for bottled gas but both the
supply and the consumption of oil products can be difficult to trace and traders difficult to identify. Where these
problems are severe the Reference Approach may be the only feasible method of obtaining CO2 estimates.
Figures for the consumption of non-traded fuels require surveys or indirect estimation (for example, for fuelwood
by forest management authorities based on forest losses). Unfortunately, there is evidence that indirect estimationof fuelwood consumption can be very inaccurate. Recent direct surveys of households in France and Central andEastern European countries have revealed levels of consumption three to eight times higher than official
estimates. Although one cannot generalise to all forms of solid biomass consumption in households it would be
prudent to treat indirect estimates of consumption with caution.
With a few important exceptions, Annex II countries do not conduct annual surveys of fuel consumption in
manufacturing, commercial and agricultural enterprises. They obtain figures for deliveries of fuels from suppliers
and, by their nature, these cover traded fuels. The use of wastes, renewables and by-products from processes are
surveyed only occasionally through special studies and these provide the basis for estimation in non-survey years.
The position in the former centrally planned economies is potentially better because most of them still have aregular survey of consumption in enterprises. These surveys do not collect details of waste and renewables use(with the exception of fuelwood) but with a little adaptation can be made to do so.
The various sources of data for each of the source categories (except transport) are discussed below.
3.1.2.1 Energy industries

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Background Paper

The “Energy Industries” source category emissions are estimated from direct combustion of fuels. The
throughputs of refineries and solid fuel manufacturing plants are not used. This source category may be divided
between the extraction industries and the transformation industries.
Transformation
For the public heat and/or power plants the fuel consumption data are readily available. Also most countries withrefineries can obtain the figures for oil fuels used within the refinery for heat raising. In contrast, refinery
statistics rarely record the use of methane within the refinery so some investigative work may be needed here. All
refineries are autogenerators and may purchase methane to supplement their local fuels for electricity generation.
Consumption of coke oven and blast furnace gas at coke ovens can be more difficult to obtain, particularly at
independent coke ovens (not sited at steel works). As the coke oven gas, produced during coke manufacture, isused to heat the ovens, there is often little interest in measuring the gas use. Where there are coke ovens at which
the consumption for heating is measured, the heat per tonne of coke output can be used to estimate for the ovens
where direct consumption has not been measured. The calculation of emissions from the combustion of fuels at
blast furnaces is not explicitly covered in the Tier 1 methods (RA or SA), but under metals production in the
Industrial Processes module. The CO2 is reported as an industrial process emission under manufacturingindustries source category. Nevertheless, the emissions from the combustion of coke and other fuels introduced
into blast furnaces will be contained in the estimates of emissions derived using the RA and SA because thequantities of carbon in the fuel supplies which will be emitted from blast furnaces cannot be identified in the
supply statistics.. To avoid double counting the blast furnace emissions, their estimated quantities calculated forthe Industrial Processes module should be subtracted from the SA estimates
Extraction
Fuel consumption statistics in the coal, oil and gas extraction industries are a mixture of figures for use of own
produced fuels and bought-in supplies. The latter are usually readily available from the supplier but the own use
consumption is more difficult to obtain because it may not be rigorously measured unless it is a significant use
and vital to the economics of the enterprise. The own use may also comprise consumption of products which are
not easily marketable and considered as waste (colliery methane) or not yet in a marketable condition (wetnatural gas at oil/gas production sites). As remarked earlier, this has implications not only for quantity statistics(activity data) but also calorific value and emission factor data.
3.1.2.2 Manufacturing and construction
Within the manufacturing sector fuels are used:(i)for heat raising;(ii) as raw materials;(iii) as reducing agents, and(iv) for their physical properties.
Only the first category is considered an energy use. All others are termed non-energy uses although some may
involve exothermic reactions from which the heat is recovered for use.
The non-energy uses include the use of fuel as carbon feedstock for incorporation in intermediate and final
goods, the use of solvents in paint manufacture and for general purposes, and the industrial process use of ovencoke or petroleum coke as reducing agents. There is also a general use of lubricants. The construction industry is
also a major consumer of bitumen
The figures for the deliveries of fuels to the manufacturing sector cannot generally provide information on thefuel use and thereby distinguish the energy from non-energy use. Certain oil products (lubricants, solvents andbitumen) are considered as non-energy products but the extent to which the carbon they contain is retained in theused product is difficult to know without additional information from the users. Waste oil recovery for re-use orfor heat raising is becoming more common but there are few statistics for the activity other than those obtained
through special studies.
Unless steps are taken to avoid it, there will be some double counting in the SA estimates of industrial process
emissions from the use of carbon in metals production (other than pig-iron) and in the manufacture of calcium
carbide. This is probably most simply handled by subtracting estimates of the CO2 from the relevant industrial
processes from the SA estimates of emissions.
The use of fuels for mobile combustion in these source categories varies considerably from one economic activity
to another and precise identification of the fuel for mobile sources needs information from each enterprise.

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Where transport fuels are heavily taxed then one can reliably infer that their use within the sector will be forvehicles. Equally, consumption of the heavier oils by the fishing industry may be considered to be for mobile
combustion and gas/diesel oil delivered to the minerals extraction industry will be used largely for mobile plant.
However, identifying the mobile use of gas oils in the construction or in agriculture is usually beyond the normal
range of energy statistics. In these, and similar cases, all combustion is treated as stationary combustion.
All other uses are considered to be for heat raising. However, the IPCC Guidelines now require the consumption
for and emissions from autogeneration electricity and heat for sale to be identified. This should be done byproviding two copies of the worksheet for manufacturing and construction (and any other main source category
where autogeneration takes place) containing the consumption and emissions from autogeneration on one sheet
and from all uses on the other. Currently, international energy data do not separate fuel use for autogeneration byeconomic activity of the enterprise and so it is likely that autogeneration by non-manufacturing enterprises is
included in the totals published. However, national statisticians collect autogeneration data on an enterprise basis
so the detail should be available at the national level.
3.1.2.3 Commercial and institutional; residential; other
Fuel consumption within these categories is almost entirely for stationary combustion. Fuels used for vehicles areallocated to the transport source category on the basis of the sales of vehicle fuels by oil companies throughservice stations. There may be some mobile combustion where organisations with significant transport needs
have direct deliveries of motor fuels but the gasoline and diesel fuel are usually readily identifiable and may be
excluded. Deliveries of gas oil for diesel engine use usually carry a significant tax and oil companies separately
record the quantities involved.
The “Other” category contains military fuel consumption for all purposes including marine use and aviation.
Note that transport covers the transport of goods or people therefore a significant part of the mobile combustion
by the military sector will not be for transport use even though it uses “transport” fuels. Unfortunately, theplacement of fuel for military uses in the “Other” category differs from that given in the internationalquestionnaires as regards military consumption for marine and aviation movements. This fact, together with thereluctance of many countries to include military fuel use in any clear manner (or at all) make good figures for the“Other” category difficult to obtain.

3.1.3“Bottom-up Approach”“Bottom-up”methods can proceed effectively where reliable data are obtained from the enterprises which use or
consume the fuels. Generally, this means that the approach is most satisfactory in manufacturing enterprises
owning large combustion plant and the energy conversion industries. In many of the other source categories theapproach uses models of the main activities based upon the stock of the fuel consuming equipment and/or thelevel of activity directly correlated with fuel consumption. The model results are checked against or constrainedby the figures for deliveries of the fuels to the source category or group of source categories containing theactivities of interest.

3.2

Calorific values and emission factors

The calorific values and emission factors (or more correctly, the carbon content) of fuels are both intrinsic
properties of fuels.
The table below repeats the values for net calorific values and emission factors found in the IPCC Guidelines.
Where there is a wide variation reported a range of values is given which encompasses the majority but not theextreme values. It is evident from the IPCC Guidelines that, for a number of countries, default values are used for
crude oil and liquefied natural gas (LNG).
For the countries who report to the OECD and Eurostat, net calorific values for energy commodities arecontained in the completed questionnaires.
The emission factors shown below are taken from various sources which have derived them from empiricalstudies or measurement (Table 1). In the source papers, the emission factors have sometimes been expressed as
specific carbon content using gross calorific values. The factors have then been converted to a net calorific basisby the IEA using approximate figures for the net/gross ratio. These are 0.95 for coal and oil, and 0.9 for natural

CO2 Emissions from Stationary Combustion of Fossil Fuels

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Background Paper

gas.1 Whilst the ratios used for coals and most natural gas mixtures are reasonable, the single ratio used for
petroleum products will not be correct for all products, particularly the lighter products.

TABLE 1
NET CALORIFIC VALUES AND EMISSION FACTORS FOR OILS AS FOUND IN THE 1996 IPCC GUIDELINES
Oil based Fuels

Net Calorific Value (GJ/t)

Emission Factor (tC/TJ)

Crude oil

41 - 43 GJ/t. Depends on crude stream.
Typical value 42.6 GJ/t. Not a characteristicof direct importance to the market someasurement is unusual.

20.0 - 21.0 tC/TJ.

Natural Gas Liquids(ethane, propane,butane and condensate)

42 - 45 GJ/t. Composition varies
considerably. Typical value 43.5 GJ/t. Local
advice needed on NCV.

17.2 tC/TJ. Dependent on composition
ranging from about 17.2 for light mixtures to19.0 for condensate rich mixtures.

Oil Shale

Usually 8.6 – 11.5 GJ/t but larger ranges arequoted.

29.1 tC/TJ (calculated using a NCV of 8.6 GJ/t)

Gasoline

44.8 GJ/t

18.9 tC/TJ

Jet Kerosene

44.59 GJ/t

19.5 tC/TJ

Other Kerosene

44.75 GJ/t

19.6 tC/TJ

Gas/Diesel oil

43.33 GJ/t

20.2 tC/TJ

Residual fuel oil

40.19 GJ/t

21.1 tC/TJ

Shale Oil

40.0 GJ/t

20.5 tC/TJ

LPG

47.31 GJ/t

17.2 tC/TJ

Ethane47.49 GJ/t

16.8 tC/TJ

Naphtha45.01 GJ/t

20.0 (default value)

Lubricants

40.19 GJ/t

20.0 (default value)

Petroleum Coke

31.00 GJ/t

27.5 tC/TJ

Refinery Gas

48.15 GJ/t Composition of gas varies withrefinery and with operations. Local advice
needed.

18.2 tC/TJ (see comment on calorific value)

Crude oil and LNG are rarely used directly for heat raising, so the NCV and emission factors are used only in the
Reference Approach. Annex 2 provides a direct means of estimating the percentage carbon content of crude oils
from the specific gravity and sulphur content of the oils. The specific gravity may be obtained from the listings of
the API gravity of the oils as traded. These tables are also attached, Annex 3. The figures for oil shale and shale
oil were provided by Dr S Soosaar, En Pro Inseneribüroo, Estonia
Solid fuels
The range of calorific values common amongst solid fuels reflects the considerable variations in their qualities
for nominally similar commodities. At present, the emission factors given in the IPCC Guidelines (Table 2) do
not show similar variations and this suggests that, for precise calculations, investigation of local fuel quality andthe associated emission factors is necessary.

1

Gross and Net Calorific Values are also known as Higher and Lower Heating Values respectively. Net calorificvalues exclude the latent heat of vaporisation of the water formed during combustion as the gaseous water isusually carried away with the flue gases . For solid fuels the difference between Net and Gross also includes thelatent heat of vaporisation of any water contained in the body of the fuel.

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

TABLE 2NET CALORIFIC VALUES AND EMISSION FACTORS FOR SOLID FUELS AS FOUND IN THE 1996 IPCC GUIDELINES
Solid Fuels

Net Calorific Value (GJ/t)(moisture free basis)

Emission Factor (tC/TJ)

Anthracite

Close to 29 GJ/t

26.8 tC/TJ

Coking coal

Typically between 26 - 29 GJ/t

25.8 tC/TJ

Other bituminous coal*

Between 24 - 29 GJ/t

25.8 tC/TJ

Sub bituminous coal

Varies considerably with quality.

26.2 tC/TJ

Lignite7 - 17 GJ/t.

27.6 tC/TJ

Peat

Typically about 17-20 GJ/t

28.9 tC/TJ

Patent fuelWill depend on the type of patent fuel. For low
temperature carbonisation products the coke CV s areclose. For aggregates of coal fines with a binder thecoal value can be used.

25.8 tC/TJ (default value)

Brown coal briquettes

Use a value for the quality of brown coal employed.

25.8 tC/TJ (default value)

Coke oven coke (hard coke)Gas coke

Typically 28 - 29 GJ/t

29.5 tC/TJ

Little information, assumed similar to hard coke.

29.5 tC/TJ* much lower figures for calorific values are cited in the IPCC Guidelines and probably reflect values for unprocessed coal containing noncombustible materials.

Gases and Wastes
Deliveries or consumption of gases are usually given in GJ or the local unit of volume (m3 or ft3).
The composition of the local gases is clearly important and can vary considerably, particularly, for coke oven andblast furnace gases. Where pig-iron and steel are both manufactured on the same site, the blast furnace gas willusually include basic oxygen steel furnace gas. This gas also contains carbon monoxide but in proportions which
are different from blast furnace gas.
The IPCC Guidelines do not contain figures for the NCVs of the gases and wastes as the data supplied to theinternational organisations are already expressed in TJ. However, data for emission factors are given and areshown in this table. The estimates below (Table 3) for the NCVs of the gases are the author’s and the emission
factor figures in parentheses correspond to the estimated NCVs. The calorific value and emission coefficient for
blast furnace gas depends on blast furnace operating conditions.

TABLE 3
NET CALORIFIC VALUES AND EMISSION FACTORS FOR GASES AND WASTES AS FOUND IN THE 1996 IPCC GUIDELINES
Gases

Net calorific value

Gas works gas
Coke oven gas
Blast furnace gas
Natural gas

Emission factor (tC/TJ)
13 tC/TJ

37.5 GJ/t, 17.5 MJ/m3
3

2.3 GJ/t, 3 MJ/m

13 tC/TJ, (11)66 tC/TJ, (80)350 GJ/t, 35.7 MJ/m

15.3 tC/TJ (15.1)

Equally, the calorific values and emission factors of the wastes used for heat raising will depend on theircomposition. In particular, the industrial wastes can vary considerably ranging from plastic waste, throughhospital wastes to the burning of old tyres for electricity generation. Emission factors are needed on the basis ofeach waste type (see the discussion below). Note that emissions from waste incineration without heat recovery
should be reported as waste emissions not as emissions from stationary combustion.

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Background Paper

3.3

Carbon storage factors

The carbon storage factor, a fraction, is used to discount part of the carbon content of the fuel. The part
discounted is deemed to be equal to the carbon stored within the long-life products manufactured from the fuel.
The storage factor depends on the fuel and its particular uses and is applied to the quantities delivered as
feedstock to the chemicals industry and to lubricants supply. The IPCC Guidelines provide factors for Ethane,
LPG, Naphtha, Gas/Diesel oil, and Natural gas although the values given are necessarily very approximate(Table 4). Correction of the carbon supply to the manufacturing source category should be done after
consultation with experts in petro-chemistry. Although the above fuels are explicitly identified in the IPCC
Guidelines as carbon feedstock, other refinery products may also be used. Some of these may not fall into theusual petroleum product categories and may be grouped under the “other (oil) products” heading in nationalenergy statistics. A carbon storage factor is also applied to lubricants to reflect the carbon remaining in waste oils
and any recycled quantities.
TABLE 4
CARBON STORAGE FACTORS AS GIVEN IN THE 1996 IPCC GUIDELINES
Fuel types

Storage factor

Ethane

0.8

LPG

0.8

Naphtha

0.8

Gas/Diesel oil

0.5

Natural gas

0.33

Lubricants

0.5

Storage of carbon in coal tars is assumed to be 100 percent and the Reference Approach suggests that theapparent consumption of coking coal should be adjusted downwards by 6 percent to account for the quantity
carbon deemed to pass into coal tars.
The Tier 1 method does not include consumption of coal tars in the list of fuels shown in the Worksheets as coaltar is assumed to be used almost entirely in applications where the carbon is stored. The light oils produced fromcoke ovens provide feedstock for motor gasoline and some solvent use. As such they are usually included in thedelivery figures for these products.

3.4

Oxidation factors

Not all carbon is oxidised during combustion. Some may be deposited in the combustion equipment and its
exhaust flues or be carried in its gases or remain in residues and ashes after combustion. The fraction which isoxidised is termed the oxidation factor. The completeness of oxidation varies with the fuel and combustion
equipment. It is highest for natural gas combustion and lowest for solid fuels. The appropriate factor for solid
fuels is critically dependent on the type of combustion equipment and the conditions of combustion.
TABLE 5OXIDATION FACTORS AS GIVEN IN THE 1996 IPCC GUIDELINES
Fuel

Fraction of carbon oxidised

Coal

0.98

Oil products

0.99

Gas

0.995

Peat for electricity generation

0.99

The table above sets out typical values given in the IPCC Guidelines (Table 5). It is limited in its range and contains
nothing for combustion in households where solid fuels (in particular, fuelwood and peat) may be burned under

24

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

conditions where combustion is restricted and particulate carbon formed. The Reference Manual (Vo.l 3) of the
IPCC Guidelines contains some additional information of the combustion of coal in different types of coal burners.
In the absence of detailed figures for the oxidation factor a value of 0.99 is recommended.

4

GOOD PRACTICE IN SELECTION OF
METHODS AND DATA

The aim is to prepare accurate, comparable and transparent inventories. Good practice guidance is intended to
improve the chances of meeting these objectives. Accuracy is determined by the quality of the data, including its
completeness and the comprehensiveness of the methodologies employed. Comparability results from the use ofcommon methodologies and transparency from the completeness of the reporting and documentation in which
both the results and the starting point and path to the results is clearly explained.
In the discussion of good practice for the preparation and reporting of greenhouse gas (GHG) inventories, it will
be important to distinguish between recommendations concerning choices of methods and values andrecommendations for work to improve the quality of data of all types.
Choice of estimation method
The primary decision facing those estimating CO2 emissions from fuel combustion is which method to use. The
choice is between the Reference Approach, the Sectoral Approach by main source categories, a combination of
the SA for some source categories, detailed estimates based on combustion plant in some sectors, and/or actual
emission measurements. The choice is entirely dictated by data availability; both activity data and emission
factors. Countries with a good statistical coverage of the main source categories and technical studies of point
and area sources may use any of the methods but would be expected to adopt the more detailed and accurate“bottom-up” methods. Countries with fewer data will be obliged to adopt the simpler methods.
Where countries are employing continuous emissions measurement systems (CEMS) for the measurement of non- CO2 gases they can also be used for CO2 measurements. However, the accurate calibration of the measurement
system is not a trivial matter and direct measurements of CO2 should not be assumed to lead automatically to themost accurate emission estimates.
Determination of calorific values and emission factors
The calorific values of traded fuels may be obtained from the fuel suppliers. For non-traded fuels, for example,
municipal, industrial and specialised wastes, the operators of the combustion plants may be able to provide
average calorific values. However, it is usual for the quantity combusted to be expressed in GJ and obtained fromthe boiler operating conditions. In this case a calorific value is not required.
The emission factors (carbon content, tC/TJ) of fuels are less readily available. The large producer/suppliers canprovide estimates based on their own fuel research. The relationship between carbon content and calorific value
for bituminous coals is reasonably linear and confirms the IPCC default values. More care is needed inestablishing the emission factors for sub-bituminous coals including lignites and the various types solid wastes
mentioned above.
If, for commonly traded fuels, the locally available values for either calorific values or emission factors differ bymore than two percent from the default values published in the IPCC Guidelines then reasons for the difference
should be found. In any continuing cases of doubt the local value should be used.
Obtaining storage factors
Storage factors are applied for petro-chemical feedstock, lubricants and bitumen. Mixtures of propane andbutane, naphtha and gas oils may all be used as chemical feedstock. The fraction of the carbon they containwhich is eventually stored in long-life products made from them can be determined accurately only throughconsultation with the manufacturers.2 The default values given in the IPCC Guidelines are, at best, approximate
figures. A factor of 0.5 is suggested for lubricants and will depend on the extent to which waste lubricants are2

See also : “International Network on Non-Energy Use and CO2 emissions. An activity within the European
Commissions’s ENRICH programme, DG RTD, “Environment and Climate”. July 2000.
http://www.eu.fhg.de/NENERGY/.

CO2 Emissions from Stationary Combustion of Fossil Fuels

25

Background Paper

collected and used for other purposes. All of the carbon contained in bitumen may be regarded as entering longterm storage.
Oxidation factor
The default values given in the IPCC Guidelines for natural gas and oil products may be used with confidence.
The uncertainties introduced into the emission estimates through the oxidation factor are related to obtaining a
reliable factor for solid fuels. The IPCC Guidelines, Vol.3 discusses this point and the variability in oxidation
factors for different types of coal combustion equipment. The discussion illustrates how oxidation factors for coalcan differ by several percentage points and, for countries where coal is an important fuel for electricity generationand industrial use direct contact is strongly advised with the major companies involved in coal burning.

5

COMPLETENESS OF THE ESTIMATES

The completeness of the estimates depends upon the comprehensiveness of the methodologies used and thecoverage of the activity data. When choosing the method for estimating emissions it is important to be confident
that all stationary combustion sources are naturally included in the approach adopted. Similarly, when choosing
data sources and fuels, their uses and coverage must be well understood so that any potential double counts oromissions can be identified and corrected. It is evident that each of the three approaches discussed in this paper(RA, SA and “bottom-up”) have their strengths and weaknesses. The first two can include emissions which are
not from stationary combustion and, where estimates of emissions from stationary combustion are required,adjustment of the total for the mobile contribution is needed. Equally, deliberate steps are necessary to ensurethat emissions from non-traded fuels are included. The ‘bottom-up” approach aggregates emissions from each of
the many sources and is the most accurate method provided that the compilers can be confident that all sources
have been identified and included and the relevant data are of good quality. It is clear that, where countries havethe data to prepare estimates using more than one methodology, a comparison of the results can throw light on
differences which may be caused by omissions or double counts. Countries that are able to prepare inventories
using several methods should do so.

6

UNCERTAINTY OF ESTIMATES

The uncertainty of the emission estimates reflects both the systematic and the random errors in the data whichlead to the estimate. In accordance with IPCC recommendations, uncertainty is expressed as a percentage(s) of
the estimate using its 95 percent confidence levels. The confidence levels are not necessarily symmetrical about
the estimate. It has to be recognised that it is rarely the case that the uncertainty in the basic data or the final
estimates can be established by rigorous means. It is more the result of judgement by those working closely withthe underlying data and the inventory preparation.

6.1

Systematic errors

Statistics of fuels deliveries and, for electricity and heat generation, consumption are usually collected by regularsurvey of fuel producers and suppliers and the energy industries’ own fuel use.
Systematic errors may exist in related energy commodities but with opposite sign. For example, crude oil
production, as reported, may contain some natural gas liquids which are removed before the use of the crude oil.
The supply of natural gas liquids will be understated and that for crude oil overstated but by compensating
amounts. Careful inspection of the commodity balances can reveal compensating systematic errors in many
related fuels due to misclassification.
Some countries also survey enterprises’ consumption. The regularity of the survey system implies consistency ofreporting and good tracking of trends. However, any failure to cover a part of the fuel market or non-traded fuels
will underreport deliveries and consumption. Over-reporting, through double counting is less usual. Equally, thecapacity of the survey system to identify correctly the economic activities (main source categories) of theconsumers depends on the diligence with which the suppliers review the economic activity classification of theircustomers or, in the case of direct surveys of consumers conducted by national statisticians, the quality of thebusiness registers.

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

6.2

Random errors

In addition to any systematic bias in the activity data as the result of incomplete coverage of consumption or
fuels, the emission estimates will be subject to random errors from mistakes in data collection and inaccuracies incalorific values and emission factors all of which may 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 toabout two to three percent of the annual figure. This figure reflects the implicit confidence limits on total energy
demand seen in models using the historical energy data and relating energy demand to economic factors.
Percentage errors for individual energy use activities can be much larger. Note that this takes no account of theerrors in the emission factors required for the emission calculations.
Uncertainties in calorific values usually reflect the uncertainty in the exact fuel composition. That is, whilst thefuel composition may be changing through the use of slightly different sources of supply monitoring, thecorresponding calorific value may be less frequent. Usually, however, where fuels are sold commercially there isa legal obligation to provide fuels (particularly to large consumers) with calorific values within certain ranges.
For the commonly traded fuels, a typical uncertainty in the figure provided by the supplier would be ± 3 percent.
For non-traded fuels and wastes the uncertainty is much higher, probably reaching 10 to 15 percent.

7

REPORTING AND DOCUMENTATION

The worksheets provided in the IPCC Guidelines Vol. 2 provide a good framework for the assembly of the data
and the procedure to be followed. Transparency is partly ensured by the rigorous recording of the sources for allof the variables involved in the calculation. A simple means of ensuring this, is to complete a copy of theworksheets with codes indicating the sources of the input data. The references, to which the codes correspond,
are then listed separately. Last revision dates for calorific values and emission factors should be given. Where
data sources are not available to the public, their use should be justified and the quality stated. The inventory
should also be adequately described by explaining any deviations from the methodology as presented in the IPCC
Guidelines and any special features of the results or factors affecting them.
The IPCC requires the worksheets for the RA (taken from Vol. 2 of the IPCC Guidelines) from all Parties for the
purposes of comparability. It does not require other Vol.2 worksheets to be submitted. However, the IPCC
requests worksheets supporting the national estimation method. Unfortunately, they will inevitably vary from one
another in format and this lack of uniformity will complicate comparison of country inventories.

8
8.1

INVENTORY QUALITY
Assessing the quality of activity data

Activity data for the Tier 1 methods are essentially the national energy statistics. Checks on their quality
comprise of internal consistency checks using the commodity balances and external consistency checks using
other sources of similar data. The balance checks use the conservation of mass and energy at various levels in theflow of an energy commodity from its extraction to its final disappearance as a commodity.
Balances for each fuel should, wherever possible, be constructed in mass units. Volume units are temperaturedependent (and pressure dependent for gases) and require correction to standard conditions. If quantities arereported in energy units there is always a doubt whether the correct calorific value has been applied by thereporter(s) at each point of the flow of the fuel from production to final consumption.
Failure to record supply or demand fully will be shown as a consistent annual statistical difference between the
total for each in the balance. There is no a priori reason why an excess of supply over demand cannot arise froman over-statement of supply and this sometimes occurs. However, obtaining good supply data involves surveying
far fewer activities and reporting units than the number involved in surveys of demand. In addition, the reporting
companies on the supply side are larger and better equipped to respond to questions concerning their supply data.
Therefore, as a general but not invariable rule, any significant and regularly occurring excess of supply overdemand usually implies incomplete (or erroneous) demand data. It is usual, however, for there to be small
differences (not greater than ± 1.5 percent for the major fuels).

CO2 Emissions from Stationary Combustion of Fossil Fuels

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Background Paper

If, when the commodity balances are expressed in energy units, the statistical differences change considerably inmagnitude and/or sign then at least one of the calorific values is suspect. This check applies only when more than
one calorific values are applicable to different parts of the balance.
Balances should be checked for compensating statistical differences across related commodities. For example,
where balances are prepared for separate types of coal, a positive statistical difference on one coal type which isregularly compensated by a negative difference on another type suggests misclassification of coal types by either
supplier or distributor.
There is no simple method of detecting systematic bias or misclassification of consumers in figures for deliveriesof commonly used fuels to the main source categories (excluding energy industries). Where bias exists, evidence
for it comes from independent surveys of consumption in enterprises or households.
Completeness of data for the fuel conversion processes, in refining, coke manufacture, blast furnace use andpatent fuel manufacture can also be assessed through checks on the inputs and outputs expressed in mass, mass ofcarbon and energy. The quantities entering the conversion processes and those leaving, each expressed in thethree types of unit should balance after known losses are taken into account. Heat losses from blast furnaces are
considerable and the carbon in the limestone should not be overlooked when constructing the carbon balance.
Emissions from blast furnaces are part of Industrial Processes emissions and not fuel combustion. Nevertheless,these checks should be applied to the blast furnace data (activity data, calorific values and emission factors) inorder to confirm their completeness or at least, expose major omissions.
External checks on activity data are very dependent on what other sources are available and this depends upon
the country approach to national energy supply and use. Where pollution control legislation exists and regulates
the activities of large energy users, the reporting it entails can provide independent data on fuel consumption as
well as the related emissions. In view of the magnitude of the combustion plants involved, this can be a usefulcheck on the reporting for national energy data and improving the overall balance quality. Independent surveys of
consumption may also be conducted for certain consumer groups (for example, households) and also

provide the opportunity to check deliveries information.

8.2

Assessing the quality of calorific values andemission factors

The balance checks on activity data when expressed in energy units and carbon content also throw light on theadequacy of the net calorific values and the emission factors. If a balance is achieved in mass and energy terms
but not in terms of the mass of carbon then it is likely that one or more of the emission factors is incorrect.
Beyond the “internal” checks there are relatively few independent means of checking the values other than accessto direct measurement by fuel laboratories or sites with emission measurement equipment using the fuel inquestion.

8.3

Using the RA to check inventory results

The IPCC Guidelines require that inventories prepared using methods other than the RA be compared with the
RA and that any significant differences be explained. For this check to be of value, the nature of the RA and therange of emissions covered by it should be appreciated. The basis of the RA is the identification and accountingof carbon flows into the nation from extraction from national reserves, net imports (imports - exports) and net
stock draw. The method described in the IPCC Guidelines adjusts the total for any carbon not likely to bereleased in the short term and (for policy reasons) any carbon delivered in fuels for international transport. It is
this principle which constitutes the RA and the estimate of emissions calculated from it should be made using thecalorific values, emission factors, storage factors and oxidation factors which are used for the preferred national
method. The default factors provided in the IPCC Guidelines are not part of the RA but are offered for use where
national factors are not available.
The paragraphs which follow set out the types of emission which are naturally included within the high-level“top-down” RA. In some cases, (explicitly indicated below), most of the emissions arise from the fossil fuelcarbon recorded in energy statistics but some are attributable to carbon (of fossil fuel origin) imported in organic
chemicals or intermediate products containing organic compounds. Although this contribution to the national
carbon flow, for most countries, is very small, those with a large carbon flow from foreign trade in organic
chemicals and derived products in primary forms may wish to estimate the effects of the flow when checking

28

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

their CO2 inventory against the RA. Similar trade corrections may also be needed if the supply of carbon anodes(principally to the aluminium industry) relies upon their import.
The types of carbon emissions covered by the RA may be grouped as follows:••

All emissions from combustion of fossil fuels including the combustion/oxidation occurring in the industrial
processes identified in Chapter 2, Vol. 3 of the IPCC Guidelines, namely:(i)

Production of ammonia;(ii)

Silicon carbide;(iii)

Calcium carbide;(iv)

Soda ash, Solvay process (from calcining), and(v)

Iron and steel, ferroalloys and other metals (however, see remark above on dependence of supply ofcarbon anodes on imports)

All fugitive emissions from the transport and use of fossil fuels and derived products. The transport and use
occurs after a point at which their production (or import) is measured. Emissions prior to these points are notincluded in the RA, viz:(a )Emissions in the transport and use of gas and oil products as fuels.

(b)

Production and use of halocarbons(c )Organic chemical and primary plastics manufacture(d)Asphalt manufacture and use, and(e)Adipic acid.

•

Short-life wastes comprising used oils, used solvents and plastics, and•There may be some emissions as the result of combustion/oxidation of feedstock used for these production
activities.

Reconciliation of the results of an RA inventory with those obtained from other methods will therefore need totake these additional sources into account either by subtracting their estimated contributions from the RA total orby adding their contributions to the estimate of emissions from fuel combustion obtained by alternative methods.

9

CONCLUSIONS•

Wherever data availability permits the most detailed method for the estimation of emissions should be
adopted for the inventory. However, if possible, several of the methods should be applied as any significant
differences will reveal possible errors or omissions.

•

The various methods for the estimation of CO2 from stationary combustion differ in their capacity to exclude
emissions from mobile sources. The methods using the most detailed activity data are the most successful inthis respect.

•

The coverage of the source categories for carbon emissions implicit in the Reference Approach should be
carefully considered when comparing the results with other methods.

•

Energy statisticians should be closely involved in the choice and use of energy data for the estimation ofemissions.

•

The distinctions made in the IPCC Guidelines (Vol. 3) between emissions from fuel combustion and from
Industrial Processes (notably when estimating emissions from metal manufacture) should be carefully
observed to avoid double counting.

•

Similarly, when hydrocarbons are used for both energy and non-energy purposes in the same enterprise
every effort should be made to obtain local expert knowledge rather than use the default carbon storage
factors offered in the IPCC Guidelines.

•

Further work is required to improve data on the use of waste oils for combustion and the fossil carbon
content of wastes, in particular, Municipal Solid Wastes.

CO2 Emissions from Stationary Combustion of Fossil Fuels

29

Background Paper•

Differences between the classification of military fuel consumption in national energy statistics and that usedin the IPCC Guidelines should be examined so that stationary and mobile consumption are not confoundedin energy data.

•

The simple default figures for the ratios of net to gross calorific values, used in the IPCC Guidelines forconverting GCV to NCV, should be re-examined for the light petroleum products.

•

Commodity, energy and carbon balances should be employed to check the overall adequacy of the energy
data, calorific values and certain emission factors.

REFERENCES
Revised 1996 IPCC GUIDELINES for National Greenhouse Gas Inventories Volumes 1, 2 and 3.
“International Network on Non-Energy Use and CO2 emissions. An activity within the European Commissions’s
ENRICH programme, DG RTD, “Environment and Climate”. July 2000. http://www.eu.fhg.de/NENERGY/.
International Standard Industrial Classification of all Economic Activities, Series M No. 4, Rev. 3, United
Nations, New York, 1990.
International Standard Industrial Classification of all Economic Activities, Series M No. 4, Rev. 3, United
Nations, New York, 1990.

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

ANNEX 1UNDERSTANDING THE COMMON REPORTING
FRAMEWORKThis chapter contains a listing, with definitions, of the categories you should use when reporting
emissions and removals. The source/sink categories have been grouped into sectors as follows:• Energy• Industrial Processes• Solvent and Other Product Use• Agriculture• Land-Use Change and Forestry, and• WasteThe sectors and their source/sink categories are described and discussed in the chapters of theReference Manual and the modules of the Workbook. This chapter also contains a brief
explanation of the principles underlying the Sectoral Tables and Summary Report Tables forreporting national inventories.
Source/sink categories
Users of the IPCC Guidelines are requested to estimate and report all anthropogenic emissions and removals ofgreenhouse gases. The numerous sources and sinks are categorised and described on the following pages. The
source/sink categories are grouped into the major sectors shown overleaf. The proposed categories should covermost activities emitting or removing greenhouse gases. However, some countries may need to add activities tothe “Other” sector in order to cover their particular circumstances. If so, then the nature of the activities should
be carefully described so that the list of sectors and their source/sink categories can be updated by the IPCC at alater date.
All activities are limited to anthropogenic activities and related emissions and removals.
Recognising that the IPCC needs to accommodate other existing inventory programmes, 1996 IPCC Guidelines
Vol. 1 Annex 2 and CORINAIR Source Categories provides details of correspondences with CORINAIR, aprogramme developed by the Commission of European Communities for use in Europe.

Sectors

Description of Activities Included

1

EnergyTotal emission of all greenhouse gases from stationary and mobile energy activities(fuel combustion as well as fugitive fuel emissions).

2

Industrial Processes

Emissions within this sector comprise by-product or fugitive emissions of greenhousegases from industrial processes. Emissions from fuel combustion in industry should bereported under Energy.
Emissions should, wherever possible, be reported according to the ISIC Group orClass within which they occur.

3

Solvent and Other Product
Use

This category pertains mainly to NMVOCs emissions resulting from the use of solventsand other products containing volatile compounds.

4

Agricutlture

Describes all anthropogenic emissions from this sector, except for fuel combustion
emissions and sewage emissions, which are covered in Energy and Waste modules.

5

Land-use Change & Forestry Total emissions and removals from forest and land-use change activities.

6

Waste

Total emissions from waste management.

7

Other

Any other anthropogenic source or sink not referred to above (must be appropriately
documented).

CO2 Emissions from Stationary Combustion of Fossil Fuels

31

Background Paper

Total emission of all greenhouse gases from stationary and mobile
energy activities (fuel combustion as well as fugitive fuel emissions).

1 ENERGY

Sum of categories I A and B.
1A

32

Fuel Combustion Activities

Total emissions of all greenhouse gases from all fuel combustion
activities as described further below. CO2 emissions from combustion of
biomass fuels are not included in totals for the energy sector. They may
not be net emissions if the biomass is sustainably produced. If biomass
is harvested at an unsustainable rate (that is, faster than annual
regrowth), net CO2 emissions will appear as a loss of biomass stocks inthe Land-Use Change and Forestry module. Other greenhouse gases
from biomass fuel combustion are considered net emissions and arereported under Energy. (Sum of I A 1 to I A 5). Incineration of waste forwaste-to-energy facilities should be reported here and not under Section
6C. Emissions based upon fuel for use on ships or aircraft engaged ininternational transport (1 A 3 a i and 1 A 3 d i) should, as far as
possible, not be included in national totals but reported separately.

1 A 1 Energy
Industries

Comprises emissions from fuels combusted by the fuel extraction orenergy-producing industries.

1A1 a

Sum of emissions from public electricity generation, public combined
heat and power generation, and public heat plants. Public utilities aredefined as those undertakings whose primary activity is to supply the
public. They may be in public or private ownership. Emissions from own
on-site use of fuel should be included. Emissions from autoproducers(undertakings which generate electricity/heat wholly or partly for theirown use, as an activity which supports their primary activity) should be
assigned to the sector where they were generated and not under 1 A 1 a.
Autoproducers may be in public or private ownership.

Public Electricity andHeat
Productioni

Public Electricity Comprises emissions from all fuel use for electricity generation except
Generation
those from combined heat and power plants.

ii

Public Combined Emissions from production of both heat and electrical power for sale toHeat and Power the public, at a single facility; co-generation plant.
Generation
(CHP)

iii

Public Heat
Plants

Production of heat for sale by pipe network.

1A1 b

Petroleum Refining

All combustion activities supporting the refining of petroleum products.
Does not include evaporative emissions, which should be reported
separately under 1 A 3 b v or 1 B 2 a below.

1A1 c

Manufacture of Solid
Fuels and Other
Energy Industries

Combustion emissions from fuel use during the manufacture ofsecondary and tertiary products from solid fuels including production of
charcoal. Emissions from own on-site fuel use should be included.

ciManufacture ofSolid Fuels

Emissions arising from fuel combustion for the production of coke,brown coal briquettes and patent fuel.

cii

Other Energy
Industries

Combustion emissions arising from the energy-producing industries
own (on-site) energy use not mentioned above. This includes theemissions from own-energy use in coal mining and oil and gas
extraction. Combustion emissions from pipeline transport should bereported under 1 A 3 e.

Energy Sector

Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Manufacturing Industries
and Construction(ISIC - 3rd Revision)3

1A2

a

Iron and Steel (ISIC Group 271 and Class 2731)

1A2b

Non-Ferrous Metals (ISIC Group 272 and Class 2732)

1A2

c

Chemicals (ISIC Division 24)

1A2

d

Pulp, Paper and Print (ISIC Divisions 21 and 22)

1A2

e

Food Processing, Beverages and Tobacco (ISIC Divisions 15 and 16)

1A2

f

Other

The remaining emissions from fuel combustion in industry should bereported here. This also includes emissions from the construction
branch. Please specify what is reported, as far as possible by ISIC
categories. Care should be taken not to double count emissions fromconstruction by including them also in Categories 1 A 3 e ii and/or 1 A
5.

1A3

Transport

Emissions from the combustion and evaporation of fuel for alltransport activity, regardless of the sector, specified by subsectors as
follows. Emissions from fuel sold to any air or marine vessel engaged
in international transport (international bunker fuels) should as far as
possible be excluded from the totals and subtotals in this category andshould be reported separately.

1A3

aCivil Aviation

Emissions from international civil aviation and domestic air transport(commercial, private, agricultural, etc.), including take-offs andlandings. Exclude use of fuel at airports for ground transport which isreported under 1 A 3 e Other Transportation (below). Also exclude
fuel for stationary combustion at airports; report this information
under the appropriate stationary combustion category.

iInternational
Aviation(International
Bunkers)

Emissions which relate to fuel use for international civil aviation. Notethat these emissions are to be excluded as far as possible fromnational totals but should be reported separately. (In other inventory
methodologies, landing and take-off (LTO) cycle emissions are often
considered as domestic emissions. For the purpose of greenhouse gas
emissions inventories, fuel used during landing and take-off for aninternational flight stage is considered to be part of International
Bunkers fuel use.)ii

Domestic

Includes all civil domestic passenger and freight traffic inside a
country (not used as international bunkers) and including take-offs
and landings for these flight stages.

1A3

3

Emissions from combustion of fuels in industry including combustion
for the generation of electricity and heat. Emissions from
autoproducers should be assigned to the sector where they weregenerated and an attempt made to separately identify the emissions
associated with autogeneration from those associated with process
heat. Emissions from fuel combustion in coke ovens within the ironand steel industry should be reported under 1 A 1 c and not withinmanufacturing industry. Emissions from the industry sector should bespecified by sub-sectors that correspond to the International Standard
Industrial Classification of All Economic Activities (ISIC). Energy
used for transport by industry should not be reported here but underTransport (1 A 3 below). Emissions arising from off-road and othermobile machinery in industry should, if possible, be broken out as aseparate subcategory. For each country, the emissions from thelargest fuel-consuming industrial categories (ISIC) should bereported, as well as those from significant emitters of pollutants. A
suggested list of categories is outlined below.

1A2

b

Road
Transportation

All combustion and evaporative emissions arising from fuel use inroad vehicles, including the use of agricultural vehicles on highways.

International Standard Industrial Classification of all Economic Activities, Series M No. 4, Rev. 3, United Nations, New York, 1990.

CO2 Emissions from Stationary Combustion of Fossil Fuels

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Background Paper

i

ii

Cars

Automobiles designated primarily for transport of persons and having
a capacity of 12 persons or fewer. Gross vehicle weight rating of3900 kg or less.

Passenger cars
with 3-way
catalysts

Passenger car emissions from vehicles with 3-way catalysts.

Passenger cars
without 3-way
catalysts

Passenger car emissions from vehicles without 3-way catalysts.

Light Duty
Trucks

Vehicles with a gross vehicle weight of 3900 kg or less designatedprimarily for transportation of light-weight cargo or which areequipped with special features such as four-wheel drive for off-road
operation.

Light duty trucks
with 3-way
catalysts

Light Duty Truck emissions from vehicles with 3-way catalysts.

Light duty trucks
without
3-way catalysts

Light Duty Truck emissions from vehicles without 3-way catalysts.

iii

Heavy Duty
Any vehicle rated at more than 3900 kg gross vehicle weight or
Trucks and Buses designed to carry more than 12 persons at a time.

iv

Motorcycles

Any motor vehicle designed to travel with not more than three wheels
in contact with the ground and weighing less than 680 kg.

v

Evaporative
Emissions from
VehiclesEvaporative emissions are included here (they are estimated with thesame activity data as are used for estimating combustion emissions).

1A3

c

Railways

Includes emissions from both freight and passenger traffic routes.

1A3d

Navigation

Emissions from fuels used to propel water-borne vessels, including
hovercraft and hydrofoils.

1A3iInternational
Comprises emissions from fuels burned by sea-going ships of all flags
Marine (Bunkers) that are engaged in international transport. These emissions should as
far as possible be excluded from national totals and reported
separately.

ii

National
Navigation

Emissions from fuel used for navigation of all vessels not engaged ininternational transport, except fishing (which should be reported
under 1 A 4 c iii). Note that this may include journeys of considerable
length between two ports in a country (e.g. San Francisco to
Honolulu).

OtherTransportation

Combustion emissions from all remaining transport activities
including pipeline transportation, ground activities in airports andharbours, and off-road activities not otherwise reported under 1 A 4 c
Agriculture or 1 A 2. Manufacturing Industries and Construction.
Military transport should be reported under 1 A 5 (see I A 5 Other,
below).

ei

Pipeline
Transportii

Off -road

1A4

Other Sectors

Emission from combustion activities as described below. Emissions
from autoproducers should be assigned to the sector where they weregenerated and an attempt made to separately identify the emissions
associated with autogeneration from those associated with process
heat.

1A4

a Commercial /Emission from fuel combustion in commercial and institutionalbuildings. (All activities included in ISIC categories 4103, 42, 6, 719,
72, 8, and 91-96).

Institutional

34

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

1A4

b Residential

1A4

c Agriculture / Forestry / Emissions from fuel combustion in agriculture, forestry, or domestic
Fishingi

Stationaryii

Off-road Vehicles
and Other
Machineryiii

Fishing

All emissions from fuel combustion in households.
inland, coastal and deep-sea fishing. This includes traction vehicles,
pump fuel use, grain drying, horticultural greenhouses and otheragriculture, forestry or fishing related fuel use. (Activities included in
ISIC categories 05, 11, 12, 1302). Highway agriculturaltransportation is excluded.

1A5

OTHER (Not else- where
specified)

All remaining emissions from non-specified fuel combustion. Include
emissions from military fuel use.

1A5

aStationary

1A5bMobileVehicles and Other Machinery, Marine and Aviation (not included in
1 A 4 c ii or elsewhere).

FUGITIVE EMISSIONS FROMFUELS

Fugitive emissions are intentional or unintentional releases of gases
from anthropogenic activities. In particular, they may arise from theproduction, processing, transmission, storage and use of fuels, andinclude emissions from combustion only where it does not support a
productive activity (e.g., flaring of natural gases at oil and gas
production facilities). Evaporative emissions from vehicles areincluded under Road Transport as Subsection 1 A 3 b v.
Sum of 1 B 1 & 1 B 2.

1B1

Solid Fuels

Total release of methane during coal mining and post-mining
activities. Combustion emissions from colliery methane recovered andused should be excluded here and reported under Fuel Combustion
Emissions.

1B1aTotal emissions from underground and surface mining and postmining activities.

Coal Miningi

Underground
Mines
Mining activities

Emissions from underground mines, brought to the surface byventilation systems.

Post-mining
activities

Emissions from coal after extraction from the ground, which occur
during preparation, transportation, storage, or final crushing prior to
combustion.

Surface Mines

Total emissions from surface mining and post-mining activities.

Mining activities

Emissions primarily from the exposed coal surfaces and coal rubble,
but also emissions associated with the release of pressure on the coal.

Post-mining
ativities

Emissions from coal after extraction from the ground, during
preparation, transportation, storage, or final crushing prior to
combustion.

ii

1B1

b

Solid Fuel
Transformation

Fugitive emissions arising during the manufacture of secondary andtertiary products from solid fuels.

1B1

c

Other

Fugitive emissions from fuel treatment plants not elsewhere specified.

CO2 Emissions from Stationary Combustion of Fossil Fuels

35

Background Paper

ANNEX 2METHOD TO ESTIMATE CARBON CONTENT BASEDON API GRAVITY AND SULPHUR CONTENT

The following formula, was provided by the US Department of Energy (Energy Information Administration), is basedon the ultimate analyses of 182 crude oil samples and may be used to estimate the carbon content of crude oil.
URL:

http://www.eia.doe.gov/oiaf/1605/gg98rpt/appendixb.html
Carbon Content = 76.99 + (10.19 ● SG) - (0.76 ● Sulphur Content)

Where:
SG denotes the specific gravity of the oil
Carbon and Sulphur content are measured in percent by weight.
Specific Gravity may be calculated from the API gravity figure using:
SG = 141.5 / (API + 131.5)
The following table provides the equivalence between API degrees and density. Intermediate values can beobtained by linear interpolation with reasonable accuracy.

TABLE 6EQUIVLENCES BETWEEN API DEGREES AND DENSITY

36

API

Density (kg/cu.m)

Density (kg/bbl)

API

Density (kg/cu.m)

Density (kg/bbl)

20

933.99148.5038834.81132.7321927.87147.5339

829.91131.9622921.82146.5740825.07131.1923915.86145.6241820.29130.4324

909.97144.6842815.56129.6725

904.15143.7643810.89128.9326

898.41142.8544806.27128.2027

892.74141.9545801.70127.4728

887.15141.0646797.18126.7529881.62140.1847792.72126.0430

876.16139.31

48

788.30125.3431870.77138.4549783.93124.6532865.44137.6150

779.61

123.9633

860.18136.7751775.34123.2834854.98135.9452771.12

122.6135

849.85135.1353

766.94121.9436844.78134.3254762.80121.2937839.76133.5255

758.71120.64

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

ANNEX 3TYPICAL API GRAVITIES AND SULPHUR CONTENTS
FOR VARIOUS CRUDE STREAMSTABLE 7TYPICAL API GRAVITIES AND SULPHUR CONTENTS FOR VARIOUS CRUDE STREAMSCountry of Origin

Crude Category

Typical API Gravity

Typical Sulphur % wt

Abu Dhabi

Murban39.8

0.8

Umm Shaif

37.5

1.4

Upper Zakum

34

1.8

Lower Zakum

40

1.1

Other Abu Dhabi

46.7

0.8

Dubai

31-32

1.9

62.5

0.1

Iranian Light

34

1.4

Iranian Heavy

31

1.6

Other Iran

32.6

2.1

Basrah Light

34

2.1

Kirkuk36

2.0

Other Iraq

36.1

2.0

KuwaitKuwait Blend

30-31

2.5

Neutral Zone

Offshore (Khafji/Hout)

28-33

1.9-2.9

Onshore23-25

3.3-3.9

Oman

Oman

34

0.8

Qatar

Qatar Marine

36

1.5

Qatar Land

41

1.2

Arab Light

33-34

1.7

Arab Medium

30-31.5

2.3

Arab Heavy

27-28

2.8

Berri (Extra Light)

37-38

1.1-1.2

Other Saudi Arabia

52.3

0.7

Syria Light

36

0.6

Souedie24

3.9

Marib Light

40

0.1

Masila Blend

30-31

0.6

Other Yemen

41

0.4

31.7

2.1

Dubai
Sharjah
Iran

Iraq

Saudi Arabia

Syria

Yemen

Other Middle East

CO2 Emissions from Stationary Combustion of Fossil Fuels

37

Background Paper

TABLE 7 (CONTINUED)TYPICAL API GRAVITIES AND SULPHUR CONTENTS FOR VARIOUS CRUDE STREAMSCountry of Origin

Crude Category

Typical API Gravity

Typical Sulphur % wt

Algeria

Saharan Blend

44

0.1

Other Algeria

45.1

0.1

Cameroon

32

0.15

Congo

37.4

0.1

Medium/Light (30-40o)

31.1

1.9

Heavy (<30o API)

27.9

2.1

Rabi/Rabi Kounga

34

0.1

Other Gabon

32.1

0.6

Light (>40o API)

41.7

0.2

Medium (30-40o API)

37.2

0.3

Heavy (<30o API)

26.2

1.7

Medium (<33o API)

29.6

0.2

Light (33-45o API)

36.3

0.2

Condensate (>45o API)

46.1

0.1

Tunisia

36.1

0.6

Zaire

31

0.2

Other Africa

29.7

0.2

Seria Light

36

0.1

Champion25

0.1

Daqing (Taching)

33

0.1

Shengli24

1.0

Other China

32

0.2

Minas

34

0.1

Cinta

33

0.1

Handil

33

0.1

Duri

20

0.2

Arun Condensate

54

0.02

Other Indonesia

38

0.1

Tapis

44

0.1

Labuan33

0.1

Other Malaysia

38.9

0.1

Bach Ho

38.6

0.1

Other Vietnam

41.6

0.1

52.6

0.04

Gippsland45

0.1

Other Australia

41.1

0.1

44.3

0.04

Egypt

Gabon

Libya

Nigeria

Brunei

China

Indonesia

Malaysia

Vietnam

Other Asia
Australia

Papua New Guinea

38

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

TABLE 7 (CONTINUED)TYPICAL API GRAVITIES AND SULPHUR CONTENTS FOR VARIOUS CRUDE STREAMSCountry of Origin

Crude Category

Typical API Gravity

Typical Sulphur % wt

RussiaUrals

31.0-32.5

1.2-1.4

Other Russia

33.3

1.2

Azerbaijan

47.7

0.01

Kazakhstan

46.5

0.5

Ukraine40.1

0.9

Other FSU

44.6

0.2

Denmark

33-34.5

0.3

Statfjord

37.5-38.0

0.28

Gullfaks29.3-29.8

0.44

Oseberg

34.0

0.3

Ekofisk

43.4

0.14

Other Norway

32.3

0.3

Brent Blend

37-38

0.4

Forties

39-40

0.34

Flotta34.7

1.0

Other UK

31.8

0.5

35.9

1.3

Light Sweet (>30o API)

36.6

0.2

Heavy (<30o API)23.4

not available

Alaska30.2

1.1

Other United States

39.5

0.2

Argentina

28.1

0.3

Brazil20.7

0.5

Cano Limon

30

0.5

Other Colombia

35.8

not available

Oriente28-29

0.9-1.0

Other Ecuador

not available

not available

Maya

22.2

3.3

Isthmus34.8

1.5

Olmecas

39.8

0.8

20.2

1.3

32.6

1.1

Medium (22-30 API)

27.7

1.6

Heavy (17-22o API)

19.5

2.5

14.5

2.8

NorwayUnited Kingdom

Other Europe
CanadaUnited States

Colombia

EcuadorMexicoPeru
Venezuela

Light (>30o API)ooExtra Heavy (<17 API)
Source: International Energy Agency.

CO2 Emissions from Stationary Combustion of Fossil Fuels

39

Background Paper

TABLE 8AVERAGE API GRAVITIES AND SULPHUR CONTENTS OF IMPORTED CRUDE OIL FOR SELECTED ANNEX II COUNTRIES
Average API Gravity

Average Sulphur % wt

Australia

39.9

0.34

Austria

37.4

0.84

Belgium

32.8

1.25

Canada32.4

0.9

Denmark

40.9

0.22

Finland

35.8

0.54

France35.8

1.01

Germany

36.5

0.76

Greece33.9

1.65

Ireland

36.9

0.25

Italy

34.1

1.15

Japan

34.8

1.51

Nethland

33.3

1.45

New Zealand

34.4

1.01

Norway33.3

0.39

Portugal

33.2

1.39

Spain

31.5

1.36

Sweden34.5

0.76

Switzerland

39.4

0.46

Turkey34.2

1.48

United Kingdom

35.9

0.64

United States

30.3

not available

Source: International Energy Agency.
Note: Average API gravities and sulphur contents have been calculated from imports into the above countries in 1998. Values willchange 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.

40

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