Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

CH4 EMISSIONS: COAL MINING AND
HANDLINGA C K N O WL E D G E M E N T
This paper was written by William Irving (USEPA) and Oleg Tailakov (Russia Coalbed Methane Center). It wasreviewed by Dina Kruger (USEPA) and David Williams (CSIRO).

ABSTRACTThe amount of methane (CH4 ) released during coal mining depends on a number of factors, the most importantof which are coal rank, coal seam depth, and method of mining. Underground coal mining releases more methane
than surface or open-pit mining because of the higher gas content of deeper seams. Total national emissions fromcoal mining, regardless of the selected methodology, should be calculated as the sum of emissions fromunderground mining, surface mining, post-mining activities, and emissions avoided due to recovery. The Revised
1996 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC Guidelines) provide two generalapproaches to estimating CH4 emissions from coal mining. The first approach, outlined in the Tier 1 and Tier 2
methodology is based on coal production and an emission factor. The second approach, the Tier 3 method, uses
mine-specific measurement data from ventilation and degasification systems to develop national estimates forunderground mines. For countries with significant underground mining, the Tier 3 method is much more reliablebecause it takes into account variability in geologic formations and mining practices. The difference between Tier 1
and Tier 2 emissions factors for coal mining is that Tier 2 requires measurement data from underground mines within
the country itself.
Generally, for both Tier 1 and Tier 2, the uncertainty in the activity data (coal production) is low compared to theuncertainty in the emission factors. Ventilation data from underground mines are much more accurate, typically
being accurate to within 20 percent. Important considerations for completeness include emissions fromabandoned mines and from waste piles, although currently no methodologies exist and data are difficult tocollect. For reporting of emissions, it is important that countries disaggregate fugitive emissions from coal mining
and natural gas systems, and also provide information on the method and emission factors used.

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Background Paper

1

INTRODUCTION

1.1

Nature, magnitude, and distribution of source

1.1.1

Overview of emissions from coal mining and handling

Methane (CH4) is produced during coalification (the process of coal formation). Only a fraction of this remains
trapped under pressure in the coal seam and surrounding rock strata. This trapped methane is released during themining process when the coal seam is fractured. Methane released in this fashion will escape into the mine works,
and will eventually escape into the atmosphere.
The amount of CH4 released during coal mining depends on a number of factors, the most important of which arecoal rank, coal seam depth, and method of mining. Coal rank represents the differences in the stages of coalformation and depends on the temperature history of the coal seam. As coal rank increases, the amount of CH4
produced also increases. Because pressure increases with the depth of the coal seam and the adsorption capacityof coal increases with pressure, deeper coal seams generally contain more methane than shallow seams of the1same rank. In addition, over time methane can be released to the atmosphere from near surface coal seams
through natural fractures in overburden strata. Coal extraction tends to lead to the release of more methane than
was originally trapped within the mined coal seam itself, because the drop in pressure draws in additional gas
from surrounding strata. Also, the mining process tends to fracture the surrounding strata including neighbouring
2
seams, particularly where long wall extraction is used.
Underground coal mining releases more methane than surface or open-pit mining because of the higher gas
content of deeper seams. Because CH4 is highly explosive in air concentrations between 5 and 15 percent, mine
operators have developed two types of systems for removing methane from the underground mine workings: (i)ventilation systems, and (ii) degasification systems. The purpose of ventilation systems, used extensively in all
major coal producing countries, is to reduce CH4 concentrations to safe levels, usually less than 1 percent.
Despite the low CH4 concentration, the large amount of air flushed through mine ventilation shafts leads tosignificant annual emissions. At present almost all ventilation air is emitted into the atmosphere. Preliminary
3
studies by USEPA indicate that economic options exist in some situations for the use of vented air.
Drainage or “degasification” systems have been installed at some of the gassiest underground mines in Australia,
United States, Russia and other countries. Typically, these systems are employed at mines that need tosupplement ventilation systems with additional CH4 recovery for safety reasons. Degasification systems extract
CH4 from the coal seams in advance of mining, during extraction, and during post-mining, by means of bore
holes drilled from surface or horizontally into the seam or surrounding strata. Depending on the quality of thegas, which in some cases can be high, mine operators can use recovered CH4 for on-site electricity generation orsell it to a local pipeline.
At surface mines, methane escapes from newly exposed coal faces and surfaces, as well as from areas of coal rubble
created by blasting operations. Additional CH4 may come from the overburden, which is broken up during themining process, and the underlying strata, which may be fractured and distressed due to the removal of theoverburden. Emissions per ton of coal are generally much lower from surface mining than from underground mining.

1

See discussion of methodologies for further elaboration of correlation between emissions and depth.

2Whilst CH4 in coal is usually assumed to have been produced by coalification, detailed isotopic studies showthat CH4 found in shallower (< 500m) seams is not necessarily consistent with this notion. The isotopic
signature is more like that of landfill gas, which is produced by microbial processes such as CO2 reduction or
fermentation. Seams with this type of CH4 are generally dry, i.e., contain no significant amounts of higherhydrocarbons. Some coal seams, particularly in Australia, but also in France and Poland, have high CO2
contents. Indeed, the gas in some seams may contain close to 100 percent CO2, and is thought to have amagmatic origin. High levels of CO2 are usually restricted to the shallower seams less than 500m depth.

3

USEPA (1998) Draft, Technical Assessment Report: Mitigation of Methane Emissions from Coal Mine
Ventilation Air“130

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Methane emissions also occur during post-mining handling, processing, and transportation. Some CH4 is released
from coal waste piles and abandoned mines. Emissions from these sources are believed to be low because muchof the CH4 would likely be emitted within the mine.
The top ten largest coal producing nations account for over 80 percent of world coal production, and over 90
4percent of hard coal production (see Table 1). The top three producers, China, US, and India account for over
two-thirds of global hard coal production.
TABLE 1LEADING PRODUCERS OF COAL (1997)
Producers

Hard Coal (Mt)

Brown Coal (Mt)

China

1,348

*

United States

909

79

India

310

23

South Africa

220

0Australia

207

58

Russia157

85

Poland138

63

Ukraine71

5

Kazakhstan

70

3Indonesia

540Rest of the World

290

585

3,775

901

World

* Included in Hard Coal. The majority of Chinese production is hard coal.
Sources: Energy Statistics and Balances of non-OECD Countries; Coal Information.

Global estimates of methane emissions from coal mining show a large variation, in part due to the lack ofcomprehensive data from all major producing countries. USEPA estimated in 1994 that global emissions from5coal mining in 1990 were in the range of 24 - 40 Tg. The large range is a result of the use of global or regionalemissions factors as substitutes for country-specific data. Leading emitters, alongside 1990 coal production, areshown in Table 2. Emissions have decreased since 1990 in countries such as Germany, Russia, and UK, becauseof coal industry restructuring. Increased production in India, China, and Indonesia through the 1990s may lead tohigher emissions later in the decade. Annual inventory data from the United States and Australia indicate
increased use of coal mine methane, thus avoiding emissions to the atmosphere.

4

Hard coal produces the highest methane emissions

5

USEPA (1994) International Anthropogenic Methane: Estimates for 1990.

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TABLE 2ESTIMATE OF GLOBAL METHANE EMISSIONS FROM COAL MINING (1990)
Country

Coal Production (Mt)

CH4 Emissions (Tg)

Underground

Surface

Total

Low

High

China

1,024

43

1,066

9.5

16.6

United States

385

548

934

3.6

5.7

Former USSR

393

309

701

4.8

6.0

Germany

77

359

436

1.0

1.2

India

109

129

238

0.4

0.4

Poland

154

58

212

0.6

1.5

Australia

52

154

206

0.5

0.8

South Africa

112

63

175

0.8

2.3

Czechoslovakia*

22

85

107

0.3

0.5

United Kingdom

75

14

89

0.6

0.9

Subtotal (Top 10)

2,043

1,762

4,164

22.1

35.9

4,740

24.4

39.6

World Total
Source: USEPA (1994).

2
2.1

METHODOLOGICAL ISSUES
Selection of good practice methods

Total national emissions from coal mining, regardless of the selected methodology, should be calculated using
the following general equation:
Total Emissions = Emissions from Underground Mines+ Emissions from Surface Mines+ Emissions from Post-Mining Emissions- Emissions Avoided Due to Recovery
Underground Mining: The IPCC Guidelines provide two general approaches to estimating CH4 emissions fromcoal mining. The first approach, outlined in the Tier 1 and Tier 2 methodology uses the following basic equation:
EQUATION 1
Emissions (Gg CH4) = Emissions Factor (m3 CH4 / tonne) ● Tonnes of Coal Produced● Conversion Factor (Gg/ 106m3)
The Tier 1, or “Global Average Method,“ requires the selection of an emissions factor (10-25 m3/ tonne) within arange specified by IPCC and drawn from the findings of regional studies. This method is to be used whennational underground coal production data are available, but more detailed regional data are not. For the Tier 2
method, also known as the “Country or Basin Specific Method,” national experts develop emissions factors
unique to a country or coal basin on the basis of at least a limited number of measurement data. These data could
be used to develop emission factors through expert judgement or statistical analysis. For both Tiers, theconversion factor is given as 0.67 Gg/106 m3.
The second approach, the Tier 3 method, uses mine-specific measurement data from ventilation anddegasification systems to develop national estimates for underground mines. For the minority of mines withoutdata, this method requires assumptions to fill data gaps. The mine-specific method produces the most accurate
estimate because it uses actual emissions rather than assumed emission factors.

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The assumption that deeper coal seams generally contain more methane than shallow seams of the same rank
usually holds true for gas content data from a single bore-hole, but when such data are examined basin-wide,
there is a lot of variability as seen in Figure 1. This is one of the compelling reasons why a mine by mine
approach (ie Tier 3) is necessary for credible estimates of fugitive emissions to be made. Nevertheless, formining situations where emission factors have to be used, the rough correlation of gas content with depth can beused as guide for the choice of emission factor.
Figure 1

Variation of gas content with depth across a coalbasin

Surface Mining: The IPCC recommends a Tier 1 and Tier 2 method for surface mining, both of which use thesame general equation form as described for underground mining. For the Tier 1 Global Average Method, theemission factor range of 0.3 – 2.0 m3/ tonne reflects a range of literature estimates and incorporates both in-situ
gas content and migration of CH4 from surrounding strata. The Tier 2 Country Basin Specific Method separates
the emissions factor into a term for the in-situ CH4 content, and a term (usually a multiple or percentage of in-situ
CH4 content) that accounts for emissions from surrounding strata:
EQUATION 2
Emissions (Gg CH4) = [In-Situ Gas Content (m3 CH4 / tonne) ● Surface Coal Production (Mt) ●Conversion Factor (Gg/ 106m3)]+ [Assumed Emissions Factor for Surrounding Strata (m3 CH4 / tonne) ● Surface Coal Production(Mt) ● Conversion Factor (Gg/ 106m3)]
Data on in-situ CH4 content usually come from measuring coal samples from specific basins and mines.
Post-Mining There are few estimates on which to base emissions factors for post-mining emissions. Due to thehigher in-situ CH4 content, post-mining emissions of underground-mined coal are assumed to be higher thansurface-mined coal. The Tier 1 Global Average Method recommends an emissions factor range for both surface(0 to 0.2 m3/tonne) and underground-mined coal (0.4 to 4.0 m3/tonne), and the Tier 2 Country or Basin SpecificMethod uses the following equation:
EQUATION 3
Emissions (Gg CH4) = In-Situ Gas Content (m3 CH4 / tonne) ● Underground or Surface Coal
Production (Mt) ● Fraction of Gas Released During Post-Mining Activities (% ) ● Conversion
Factor (Gg/ 106m3)
Emissions Avoided: For all Tiers, the IPCC Guidelines account for methane utilization by adjusting the estimate ofgross emissions downward by the amount recovered and used. Data on gas utilization is obtained from either the coalindustry itself or it must be inferred from information about recovery efficiency, gas sales or end-use data.

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2.2

Emissions factors

Tier 1: The IPCC default emissions factor ranges listed in Table 3 are synthesized from a number of countryspecific studies, and do not necessarily reflect current conditions in any particular country. As more countries
conduct emissions studies, there will be less of a need to choose an emissions factor from these ranges.
TABLE 3
TIER 1 DEFAULT IPCC EMISSIONS FACTORS (M3 CH4 / TONNE)
Category

Low

High

Underground Mining

10

25

Surface Mining

0.3

2.0

Post-Mining (Underground)

0.9

4.0

Post-Mining (Surface)00.2

Use of the Tier 1 emissions factors introduces uncertainty. Because of the magnitude of emissions, it isparticularly important to choose an underground mining emissions factor that reflects country-specific conditions
as closely as possible. The IPCC Guidelines cite numerous studies as the basis for underground mining emissions
factors. These and other studies of mines or basins whose geological and engineering conditions closely resemble
those within the country will provide insight into choosing within the IPCC range. A database of emissions
factors, which includes a description of contributing factors such as in-situ content, depth, and permeability,
would facilitate this expert judgement.
Tier 2: Underground Mining The difference between Tier 1 and Tier 2 emissions factors for undergroundmining is that Tier 2 requires measurement data from underground mines within the country itself. Because
geologic factors rather than political borders determine emissions, it is advisable to generate emissions factors foreach basin within countries that have multiple basins.
The Australian inventory used 1990 CH4 concentrations, ventilation flow rate, in situ CH4 content, and coalproduction rate data provided by a subset of individual mines to develop country-specific emissions coefficients
6for gassy and non-gassy mines. In Australia, as in the United States and other large coal producing nations, thebulk of emissions come from a relatively small number of gassy mines, and the relationship between theunderlying variables and emissions for these mines is qualitatively different from smaller less gassy mines.
Statistical regression produced the following equation for gassy mines:
EQUATION 4
Emissions1990 = (4.95 ● Coal Production ● In-Situ Content1990 + 5.58) ● Conversion Factor
Repeating the analysis for the same subset of mines four years later produced a different equation:
EQUATION 5
Emissions1994 = (4.01 ● Coal Production ● In-Situ Content1994) ● Conversion Factor
That the second equation gives an estimate that is about one-third lower than the first highlights the need for
multiple measurements in different years for the same mines, and from as many mines as possible with the same
year. Part of the change in the equations is due to actual variability in mining emissions, and the remainder is due
to uncertainty in the measurement data. Emissions from a given level of production could change because offactors such as the closure or opening of large gassy mines, mining deeper into the same or neighbouring coalseam, or a change in mining techniques. The Australian inventory takes the average of these two results to comeup with a national estimate.
Tier 2: Surface Mining Measurements of actual emissions from surface mining are technically difficult, costly,
and generally are not available for inventory preparation. An alternative outlined in Tier 2 is to base the estimate
on the in-situ gas content of surface coal. In-situ gas contents can vary greatly within a country as demonstrated
by basin-specific data from the US inventory as shown in Table 4.

6

Australian National Greenhouse Gas Inventory.
(http://www.greenhouse.gov.au/inventory/natinv/95/95energy/n95_1b1.html)

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TABLE 4US SURFACE COAL IN-SITU CONTENT
Basin

Average In-Situ Content (m3/tonne)

Northern Appalachia

1.3

Central Appalachia

1.3

Warrior

1.3

Illinois

1.0

S.West/Rockies

0.4

N. Great Plains

0.08

West Interior

0.08

Northwest

0.08

Source: EPA (1993).

The assumption is that all of the in-situ gas is released during surface mining, although to avoid double counting,this assumption should be modified if countries also assume that a fraction of in-situ CH4 is released during postmining activities. To account for the methane that migrates from surrounding strata, the assumed emissions factor
should be based on measured variables such as gas content, and qualitative characteristics such as permeability.
Tier 2: Post-mining Tier 2 post-mining emission factors are based on the in-situ contents of coal seam. The
quality of these emission factors will depend primarily on the quality of the emission factors developed forsurface and underground mining.
Tier 3: Underground Mining Coal mine methane is a safety hazard because it is highly explosive in ambientconcentrations between 5 and 15 percent. All gassy underground mines must ventilate CH4 to ensure safe
working conditions, and data from these measurements can be used to estimate national emissions. In theory,
total national ventilation emissions are equal to the sum of emissions from each mine. There are five generalissues associated with using mine-specific ventilation data, however, that should be considered:•

For each mine, periodic sample measurements (usually CH4 concentration or flow rate) must be used toestimate total emissions over one year. In almost all cases, mines do not currently monitor CH4 emissions
continuously. Instead, the frequency of sampling depends on national and local regulations, and local
practices. It may be necessary to take the average of multiple measurements. The greater the variability inventilation emissions, the more measurements will be needed to complete a representative sample.

•

Sampling should be representative of typical mining conditions. If samples are taken when there is a temporary stopin coal production, for example, ventilation estimates are likely to underestimate CH4 emissions.

•

Data may not be available for each mine. In some countries, only data from the gassiest mines are available
and the emissions from the remainder must be estimated. Data may also be missing when mine operators
report it on a voluntary basis. In most coal basins, however, a small number of gassy mines contribute to adisproportionately large share of total emissions. Figure 1 shows that, in the case of four major coalproducing countries (US, Poland, Australia and Russia) the 10 gassiest mines emit over 60 percent of total
7
emissions. With limited resources, it is recommended that countries focus on obtaining data for the top 10
to 20 emitting mines, and then estimate emissions from less gassy mines, rather than abandon the Tier 3
method for more general emission factors (see Figures 2 and 3.). While it may not be possible to determine
which mines are in the top 10-20 percent without original data, a complete survey during one year would
allow countries to focus on the high emitting mines in future years. Where this is not possible, periodic
surveys of mine operators would enable countries to determine which mines are the gassiest. Such mines
typically suffer from more work slowdowns, outbursts, and, in unfortunate cases, methane explosions.
Estimating emissions from the less gassy mines without data is relatively straightforward since total
emissions from a large number of small sources are less susceptible to yearly fluctuations. If, in a year with

7

Mine totals include both ventilation emissions and emissions from degasification or drainage systems.

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Background Paper

full data, the subset of less gassy mines accounted for 20 percent of total emissions, the same subset will
8
likely account for a similar proportion in future years.
•

Data may not be available for each year. If data is available for one year, but not subsequent years, coalproduction-based emission factors can be back-calculated and applied to production statistics for future years.
If the same mines are in operation from year to year, this technique can produce a high quality estimate. If,
however, key mines close and others open, the back-calculated emissions factors are less reliable.

•

Ventilation air measurements are not possible when CH4 concentrations are below detectable levels. While itis technically possible to measure minute amounts of CH4, from a mine safety perspective, it is not necessary
to measure CH4 below approximately 0.1 percent of overall volume. For widely used methanometers,
concentrations below 0.1 percent are considered non-detectable. Flushing a large air volume with even small
amounts of CH4 over the course of a year can produce significant emissions. One strategy to account forthese emissions is to assume an average methane concentration (a figure below 0.1 percent) and multiply thisfigure by an average ventilation rate. For example:
EQUATION 6
Non-Detectable CH4 Emissions = 0.05%CH4 /Air Volume ● Average Ventilation
Flow Rate/Day ● 365 Days

A complete inventory should also account for CH4 emitted from gassy mines with degasification or drainage
systems. The following issues should be resolved when accounting for degasification system emissions:•

Degasification system emissions can occur before, during and after the coal seam has been mined through. In
the US, mine operators often drill vertical wells into the coal seam in advance of mining to drain as much
CH4 as possible. Similarly, many countries drill wells into the gob area remove CH4 after the seam has been
mined through. If a country is using actual emissions data from degasification systems, both of theseemissions should be accounted for in the year in which the coal was mined. The same conditions apply to theuse of gas sales data for estimating emissions from degasification systems.

•

Degasification system emissions can be estimated on the basis of recovery efficiency. It is in the interest ofmine operators to know the efficiency with which degasification systems remove CH4 from a coal seam.
Emissions can be estimated from the following equation:
EQUATION 7
3

Total Mine Emissions (m ) = [Ventilation Emissions (m3)] / [100% - Efficiency Factor]
When information on degasification efficiency is not available, countries should apply default efficiencies. One
option is to apply high, medium, and low efficiencies of 60 percent, 40 percent, and 20 percent.

2.3 Activity data
Tiers 1 and 2: For Tier 1, data on national underground and surface coal production are sufficient for estimating
national emissions. This data can be obtained from the appropriate national agency, or from the International
Energy Agency. If a country disaggregates emission factors by coal basin or political district, coal production
statistics should follow the same breakdown. In cases where a political district contains two or more coal basins
and production statistics are available only at the district level, the production data should be allocated to eachbasin. For both tiers, post-mining emissions requires the same activity data as underground and surface mining.
Tier 3: Coal production data are not used when a country bases the estimate of underground mine emissions on
ventilation and degasification system measurements. It may be useful to check the Tier 3 method by comparing itto the emissions estimate based on coal production and emissions factors. This would allow inventory experts toevaluate the relevance of commonly used emissions factors to specific countries. Production data is also
necessary when measurement data is not available each year, and the methodology uses emissions factors thathave been back-calculated from previously used data.

8

This assumes no major changes in the subset of large gassy mines.

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Figure 2
Distribution of emissions from US (1997), Poland(1988), Russia (Kuznetsk Coal Basin, 1998) and Australia (1995)
underground mines

USA

PolandRussia (Kuznetsk Coal Basin)

Australia

100%
90%
80%

% of emission

70%
60%
50%
40%
30%
20%
10%

1

Figure 3

10100number of mines

0%
1000

Distribution of emissions from US (1997), Polish(1998), Russia (Kuznetsk Coal Basin, 1998) andAustralian (1995) underground mines

USA

PolandRussia (Kuznetsk Coal Basin)

Australia

100%
90%
80%
% of emission

70%
60%
50%
40%
30%
20%
10%
0%

1%

10%

0%
100%

% of mines

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2.4

Calculating emissions avoided

Wherever possible, the national emission estimates should take into account the collection and use of CH4 as
9fuel. At present, all recovered CH4 comes from degasification systems, and the calculation of emissions avoided
requires much of the same data and techniques as the calculation of emissions. If degasification system data are
available, then it should be possible to determine the total amount of gas collected, the amount of gas used for
fuel, and any portion vented to the atmosphere. It may be necessary to estimate the amount of methane drained
from degasification systems, and then subtract the amount of methane burned from data on gas sales. In this case,
it is important to determine whether or not the gas sold was drained from coal seams that are being mined in thecurrent year. A general rule is that emissions avoided are linked to specific coal seams. For example:•

If gas is recovered from a degasification system and used as fuel, but the coal seam is never mined due tounforeseen economic or engineering factors, this should not be counted as emissions avoided.

•

Similarly, if coal seams are being mined for gas and there is no intention of ever mining the coal itself, thisgas use should not be counted as emissions avoided. Fugitive emissions from this process should be
accounted for as part of the oil and gas sector calculation.

•

Gas recovered in advance of mining should be counted as emissions avoided in the year when the sourcecoal seam is mined through.

Annex 2 shows a sample calculation of emissions avoided from a set of underground mines, using gas sales data.
While almost all recovered gas comes from underground coal mines, in the western US and in other countries,
CH4 is being recovered from gassy surface coal seams.

2.5

Uncertainty

Parallel to the IPCC sector-specific workshops on good practice guidance, the IPCC is completing a programmeof work on emissions inventory uncertainty. This work will result in recommendations to the United Nations
Framework Convention on Climate Change (UNFCCC) on approaches to assessing and managing uncertainty.
During the IPCC Inventory Experts Group Meeting in Paris (October 1998), technical experts in the uncertainty
programme came up with a series of questions to be answered in the sector workshops. Specifically, the sector
workshops should provide answers to these questions in the individual source context. The questions are listed in
the general background paper.
Generally, for both Tier 1 and Tier 2, the uncertainty in the activity data (coal production) is low compared to theuncertainty in the emission factors. Underground mining emission factors are based on more measurement data
than surface mining, and there are very few measurements on which to base emission factors for post-mining
activities. Given the large contribution to total emissions from underground mining, and the feasibility ofcollecting accurate measurement data from these mines, the best way to reduce uncertainty is focus on the Tier 3
method. Below is a description of the major uncertainty issues for the Tier 1, 2 and 3 IPCC methodologies.
Tier 1: Given that the emissions factors for Tier 1 are not based on country-specific data, they do not represent
geologic conditions accurately for each country. The emissions factors are highly uncertain as a result.
Tier 2: The primary sources of uncertainty in the Tier 2 emissions factors are the unrepresentative measurement
samples, and the natural variability of in-situ CH4 content. Consequently, efforts undertaken to reduce uncertainty
should focus first on improving emission factors, or in the case of underground mining, collecting the necessary
ventilation data to use a Tier 3 method.
Tier 3: The Australian national inventory estimates that mine ventilation data is accurate to within approximately± 20 percent. More frequent measurement could reduce this uncertainty. More work needs to be done to assess
the accuracy of ventilation system data, but there is more uncertainty associated with estimating the recovery
efficiency of degasification systems, and estimating emissions avoided from gas sales for previous years.

9

Coalbed methane is generally not flared on site because of safety concerns. Should this practice be adopted,
countries should subtract flared gas from national emissions totals.

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2.6

Completeness

Abandoned coal mines: Emissions from abandoned mines may come from unsealed shafts and from vents
installed to prevent the build-up of CH4 in mines. There is very little information on the number of abandoned
mines, and no data are currently available on emissions from these mines. The IPCC Guidelines do not suggest amethodology for estimating these emissions, but if a country has data on which to base a measurement, it should
do so in a transparent manner.
Waste piles: Coal waste piles are comprised of rock and small amounts of coal that are produced during mining
along with marketable coal. There are currently no emission measurements for this source. Emissions are
believed to be low, however, because much of the methane would likely be emitted in the mine and the waste
rock would have a low gas content compared to the coal being mined.

2.7

Other important issues

Baseline: An emissions baseline is an important component of an inventory program. When a country has
sufficient ventilation data for a Tier 3 method during the current year, but this data is not available for thebaseline year, the inventory will have to reconcile different data sets.

3

REPORTING AND DOCUMENTATION

A recent report from the UNFCCC Secretariat "Methodological Issues Identified While Processing Second
National Communications" (UNFCCC/SBSTA/1998/7) noted that some Parties presented aggregate emission
figures for broad IPCC sectors only, such as for industrial processes and fugitive emissions, and did not
disaggregate their emissions on sub-sectors and source categories as is requested by the IPCC Guidelines. For
the purpose of transparency and comparability, it is important to disaggregate fugitive emissions from fossil fuels
into coal mining, natural gas, and oil. The processes are quite distinct and, since the calculations must be done
separately, this should not impose a burden. In addition, reporting them separately should not reveal any
confidential information
Transparency will be improved if all countries report estimates for underground, surface, and post-mining
activities separately, and indicate whether they use Tier 1, Tier 2, or Tier 3 methods for each sub-source. It isalso important that all information used to estimate emissions be available either directly in national inventories
or indirectly by citing other documents. For Tier 1 and Tier 2, countries should report coal production and theemission factors used. Tier 2 calculations should also show how emissions factors were developed. For Tier 3
calculations of emissions from underground mining, countries should report the number of mines with andwithout data, any assumptions necessary to use the data, the number of mines with degasification systems inplace, and the number of mines recovering gas for use as fuel.

3.1

Current IPCC reporting guidelines

The IPCC Guidelines: Reporting Instructions are used to guide countries in the preparation and submissions ofannual greenhouse gas emissions inventories to the UNFCCC. The Guidelines establish:•

Standard tables, definitions, units, and time intervals for reporting all types of emissions;•

Necessary documentation to enable comparison of national inventories, including worksheets, major
assumptions, methodological descriptions, and enough data to allow a third party to reconstruct the inventory
from national activity data and assumptions, and•An uncertainty assessment.

CH4 emissions from coal mining are reported in sheet 2 of Table 1: Sectoral Report for Energy, which calls for
entries under fugitives for emissions from coal mining, solid fuel transformation, and 'other'. Reporting the shareof emissions from the different sub-categories – underground mining, surface mining, post-mining activities –
would provide significantly more transparency than is requested currently.

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3.2

Confidential business information

Coal mine operators may judge degasification system emissions specifications, emissions avoided data, or mining
practices to be sensitive. Should this be the case, inventory agencies will need to publish only aggregate data on
recovery and emissions avoided, or estimate emissions from publicly available information on gas sales.

4

INVENTORY QUALITY

4.1

Introduction

Inventory quality assurance and quality control (QA/QC) is a process integral to the development of a credible
inventory. A well-developed and well-implemented quality assurance programme fosters confidence in the final
inventory results regardless of the purpose and goal of the inventory. A successful quality assurance programme
requires internal quality control procedures and an unbiased, external review and audit. The internal QC activities
are used to ensure accuracy, documentation, and transparency during inventory preparation. The external
independent review (QA) process is designed to identify errors that occur in the preparation of emissions
inventories, and reduce or eliminate potential inherent bias. Figure 4 outlines the flow of information andprocesses followed at each step.
Figure 4

Inventory QA/QC process
Mine Safety Agency

Internal QC:
assessment

Ventilation emissions data; degasification data (if applicable); uncertainty

Documentation:

Mine-specific emissions data; QC results; number, frequency, and location ofsamples
GOVERNMENT INVENTORY AGENCY

Review/QA:

Production data, externally developed emissions factors, mine-specific data,
gas sales, and calculations

Internal QC:

Emission factor development, emissions calculations, emissions avoided
account

Documentation:

Results of compilation and results of QA/QC

Reporting:

Official submission to UNFCCC
External Review

External Review:

External audit, stakeholders, peer & public review of inventory results,
external verification against other data etc.

Documentation:

Results of external review

4.2
4.2.1

Internal inventory QA/QC systems
Emission factor development

Emissions factors QC
Tier 1 The range of default emissions factors comes from an IPCC assessment of relevant literature. QC
procedures include reviewing the national circumstances and documenting the rationale for selecting specificvalues. Other QC procedures are not required.
Tier 2 QC procedures for the Tier 2 emissions factors involve checking the equations and calculations used to
calculate the emissions factor. The Tier 2 emissions factors are based on country or basin-specific information on

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

in-situ gas contents and a limited set of emissions measurements for underground mines. Sampling should follow
consistent protocols to ensure that conditions are representative and uniform.
Tier 3 Because of safety concerns, each individual mine should already have in place a QA/QC programme formonitoring ventilation emissions. The mine safety agency carries out random sampling checks of these mines andwill have additional quality control procedures. The inventory agency should work with mine operators to ensure
the quality of data from degasification systems.
Emissions Factors Documentation
Documentation is a crucial component of the review process because it enables reviewers to identify mistakes
and suggest improvements. A standardized reporting form is recommended to provide transparent information on
the steps taken to calculate the emissions factor or measure emissions. Each step should contain the numbers usedin each calculation, including the source of any data collected.

4.2.2

Collection of activity data

Activity Data QC
Tier 1 and Tier 2 - Coal Production Data A country’s ministry of energy generally collects annual coalproduction data or a similar organization focused on the energy sector. The data are generally not collected forgreenhouse gas inventories. The personnel that collect data are responsible for reviewing the data collection
methods, checking the data to ensure they were collected and aggregated correctly, and cross-checking the datawith previous years to ensure the data are reasonable. In addition to a description of weak spots and suggestions
for improvement, the basis for the estimates, whether statistical surveys or 'desk estimates,' must be reviewed anddescribed as part of the QC effort.
Activity Data Documentation
Documentation is a crucial component of the review process, because it enables reviewers to identify mistakes andsuggest improvements. Among others, the following information is needed for the reviewing/auditing agency:•

A highly detailed description of the methods used to collect the activity data, and•A discussion of potential areas of bias in the data, including a discussion of whether the animal and feedcharacteristics are representative of the country.

4.2.3

Inventory agency level activities

Inventory Agency Review (QA) of Activity Data
Before accepting the activity data, the inventory agency should assess its quality. This review involves close
cooperation with the personnel responsible for collecting, compiling, and analyzing the data. The assessment
should include a review of the detailed methods used to collect the data, including a review of any surveys andinterviews performed to collect the data. In addition, the assessment should include a comparison of the activity
data with historical data, a discussion of the potential for bias, and recommendations for improvement.
Inventory Agency Review (QA) of Emission Factors
When the inventory agency applies emission factors from the literature, it should review the background data,measurements and assumptions used to come up with these emissions factors. It is particularly important to checkfor representative sampling, sufficient sampling size, and documented assumptions. This may entail contacting
researchers to ask for additional information. Review of ventilation data should follow a procedure similar to thereview of coal production data. This review will involve close cooperation with the mine safety agency todetermine collection methods and review raw data.
Inventory Agency Review (QA) of Emissions Avoided Data
Emissions avoided data will be based on reports from mine operators, and from gas sales statistics. A review
should determine the completeness and accuracy of this data, and its suitability for determining CH4 use. The
magnitude of reported emissions avoided should be consistent with degasification system capacity and coalproduction for a given year.
Inventory Agency QC on Compiling National Emissions
In addition to a thorough quality assessment of data discussed above, the inventory agency should ensure that theprocess of aggregating data to develop the national inventory undergoes quality control. This should include,
among other things:

CH4 Emissions: Coal Mining and Handling141

Background Paper•

Back-calculating national and regional emission factors from the Tier 3 measurement data (if using Tier 3);•

Ensuring that the emission factors are representative of the country (if using Tiers 1 and 2);•

Ensuring that all mines are included, and•Comparing with national trends to look for anomalies.

Inventory Agency Documentation on Compiling National Emissions
For the CH4 emission inventory for coal mining, a QA/QC management plan should address the specific items
needed to perform audits and reviews. Examples of the types of information needed for documentation andexternal audit include:•

A detailed description of the inventory methodology;•

Identification of the input parameters that are needed and how the input parameters are obtained, and•Frequency of data collection and estimation and results of determinations of accuracy and precision.

4.3

External inventory QA/QC systems

External QA activities include a planned system of review and audit procedures conducted by personnel not
actively involved in the inventory development process. The key concept is independent, objective review toassess the effectiveness of the internal QC programme, the quality of the inventory, and to reduce or eliminate
any inherent bias in the inventory processes. Several types of external reviews, or audits, may be appropriate forthe inventory of CH4 emissions from coal mining. Reviews should always occur when methods change. If
methods do not change, it is recommended that countries review the methods annually, or, if resources arelimited, every three to four years. The reviews should be as follows:•

Third party audit by an accredited organization, expert, independent third party: An audit of the
documentation and calculations ensures that each number is traceable to its origin.

•

Expert (peer) review: Although a detailed peer review would be appropriate when a procedure fordetermining CH4 emissions is first adopted or revised; it would not be needed on an annual basis. Such a
review is designed to ensure that the methodology is rigorous, accurate, and that the data and assumptions
reflect the best available information.

•

Stakeholder review: Review by industrial organizations and government can provide a forum for review ofthe methods used, such as a review of the emissions factors, and emissions avoided data, and•Public review: Some countries make their entire inventory available for public review and comment. This
process may result in a range of comments and issues broader than those from other review processes.

5

CONCLUSIONSAll estimates of total national emissions from coal mining, regardless of the selected methodology, should be
calculated using the following general equation: Total Emissions = Emissions from Underground Mines +Emissions from Surface Mines + Emissions from Post-Mining Emissions - Emissions Avoided Due to Recovery.
The IPCC Guidelines provide two general approaches to estimating CH4 emissions from coal mining. The first(Tier 2 and Tier 1) uses coal production as the activity data and an emission factor based on methane emissions
per unit of coal production. Tier 2 emissions factors require measurement data from underground mines within
the country itself, whereas there are default Tier 1 emission factors for regions. The Tier 3 method uses minespecific measurement data from ventilation and degasification systems to develop national estimates forunderground mines. Given the large contribution to total emissions from underground mining, and the feasibilityof collecting accurate measurement data from these mines, the best way to reduce uncertainty is to focus on the
Tier 3 method. Wherever possible, the national emission estimates should be corrected for the amount of CH4
that is used as fuel, by subtracting this amount from total estimated emissions
There are no methodologies for estimating emissions from abandoned mines or coal waste piles in the IPCC
Guidelines, but if a country has data on which to base a measurement, it should do so in a transparent manner.
For the purpose of transparency and comparability, it is important to disaggregate fugitive emissions from fossil
fuels into coal mining, natural gas, and oil. The quality of all activity and emission factor data should be studied
and reviewed in cooperation with the personnel responsible for collecting, compiling, and analyzing the data.

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Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

When the inventory agency applies emission factors from the literature, it should review the background data,measurements and assumptions used to come up with these emissions factors.

REFERENCES
Australian National Greenhouse Gas Inventory.
(http://www.greenhouse.gov.au/inventory/natinv/95/95energy/n95_1b1.html)
International Panel on Climate Change (IPCC), 1996. Greenhouse Gas Inventory Reference Manual (Revised).
v.3.
International Energy Agency (IEA), „Energy Statistics and Balances of non-OECD Countries; Coal Information“,(http://www.iea.org/stats/files/keystats/p_0105.htm).
USEPA, 1993. Anthropogenic Methane Emissions in the United States, Global change Division, Office of Air
and Radiation, Washington, DC.
USEPA, 1991. Assessment of the Potential for Economic Development and Utilization of Coalbed Methane in
Poland, Office of Air and Radiation, Washington, DC.
USEPA, 1994. International Anthropogenic Methane Emissions: Estimates for 1990, Office of Policy, Planningand Evaluation, Washington, DC.
USEPA, 1993. Options for Reducing Methane Emission Internationally. Volume II: International Opportunities
for Reducing Methane Emissions, Global change Division, Office of Air and Radiation, Washington, DC.
USEPA, 1996. Reducing Methane Emissions From Coal Mines in Russia, Office of Air and Radiation,
Washington, DC.
USEPA, 1996. Reducing Methane Emissions From Coal Mines in China: The Potential for Coalbed Methane
Development, Office of Air and Radiation, Washington, DC.
USEPA, (1998) Draft „Technical Assessment Report: Mitigation of Methane Emissions from Coal Mine
Ventilation Air“CH4 Emissions: Coal Mining and Handling143

Background Paper

ANNEX 1ESTIMATED UNDERGROUND EMISSIONS FACTORSFOR SELECTED COUNTRIESCountry

Emission Factors (m3/tonne)

SourceFormer Soviet Union

17.8 – 22.2

USEPA (1993c)

United States

11.0 – 15.3

USEPA (1993a)

Germany (East & West)

22.4

Zimmermeyer, 1989

United Kingdom

15.3

BCTSRE, 1992

Poland

6.8 – 12.0

Pilcher et al, 1991

Czechoslovakia

23.9

Bibler et al., 1991

Australia

15.6

Lama, 1992

ANNEX 2

SAMPLE EMISSIONS AVOIDED CALCULATION

Gas Sales in Each Year (m3)

Mine

Total
Avoided (m3)

Y-6

Y-5

Y-4

Y-3

Y-2

Y-1

Y

1

1050

1500

2000

2000

2200

1250

1250

4

2000

2

-

-

-

9000

9500

8000

8500

2

9500

3

5800

6000

6250

4000

3000

-

-

6

5800

4

1900

2200

2550

3000

3150

4000

4400

4

2550

5

-

-

-

9500

10000

10500

12000

6

0

Total

144

Years in advanceof mining

14630

Energy Sector