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TECHNICAL SUPPORT DOCUMENT FOR 

UNDERGROUND COAL MINING: RULE FOR 

MANDATORY REPORTING OF GREENHOUSE 

GASES 

Office of Air and Radiation 

U.S. Environmental Protection Agency 

May 26, 2010 
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CONTENTS 

1. Source Description.................................................................................................................3 

a. Total Emissions (based on Inventory).................................................................................3 

b. Types of Emissions to be Reported.....................................................................................4 

2. Options for Reporting Thresholds ...........................................................................................8 

a. Options Considered ............................................................................................................8 

b. Emissions and Facilities Covered Per Option .....................................................................9 

3. Existing Relevant Reporting Programs/Methodologies..........................................................10 

4. Proposed Monitoring Methods ..........................................................................................13 

Monitoring Methods Considered...........................................................................................13 

5. Procedures for Estimating Missing Data...............................................................................17 

6. QA/QC and Verification Requirements................................................................................17 

7. Reporting Procedures...........................................................................................................18 

REFERENCES.........................................................................................................................20 
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1. Source Description 

Coal production in the United States reached a record level in 2006, with production of 1,163 

million short tons, according to the Energy Information Administration (EIA 2007). This was 

produced from 1,424 mines, of which, 612 were underground mines and 812 were surface 

mines.

1

Two greenhouse gas (GHG) emissions are of concern in the coal mining sector. The first and 

largest source of emissions is fugitive emissions of methane (CH4) released from the coal and 

surrounding rock strata due to mining activities. There are five primary sources of fugitive CH4

emissions from coal mining operations: 

• Ventilation air from underground mines, which contains dilute concentrations of CH4

• Degasification systems at underground coal mines (also commonly referred to as 

drainage systems). These systems may employ vertical and/or horizontal wells to recover 

CH4 in advance of mining (known as "pre-mine drainage") or after mining (called "gob" 

or "goaf" wells) 

• Fugitive emissions from post-mining operations, during which coal continues to emit 

CH4 as it is stored in piles, processed, and transported 

• Surface mines, from which CH4 in the coal seams is directly exposed to the atmosphere 

• Abandoned or closed mines, from which CH4 may seep out through vent holes or through 

fissures or cracks in the ground. 

The second source of GHG emissions -- combustion-related CO2 emissions -- are associated with 

the use of energy in mining operations, both from stationary and mobile sources, for both surface 

and underground mines. In some cases, CH4 produced from the coal mine itself is combusted as 

a source of energy. 

Total Emissions (based on Inventory)

The annual Inventory of U.S. GHG Emissions and Sinks considers active coal mining-related 

fugitive CH4 emissions to the atmosphere from three sources: underground mining, surface 

mining, and post-mining (i.e., coal-handling) activities (EPA 2008). Total CH4 emissions from 

active mining operations in 2006 were estimated to be 58.5 million metric tons of CO2 equivalent 

(CO2e) from these sources, a decline of 30% since 1990. Of this, underground mines accounted 

for 35.9 million metric tons of CO2e, surface mines accounted for 14.0 million metric tons of 

CO2e, and post-mining emissions accounted for 8.6 million metric tons of CO2e. Fugitive CH4

emissions from inactive, closed (or abandoned) coal mines were estimated to contribute another 

5.4 million metric tons of CO2e. 

The relative contribution of the various sources of coal mine emissions is illustrated in Figure 1. 

 

1 An underground mine is where coal is produced by tunneling into the earth to the coalbed, which is then mined 

with equipment such as cutting machines and continuous, long wall, and shortfall mining machines. Underground 

mines are classified according to the type of opening used to reach the coal, i.e., drift (level tunnel), slope (inclined 

tunnel), or shaft (vertical tunnel). In contrast, surface mines are mines that are usually within a few hundred feet of 

the surface. Earth and rock above or around the coal (overburden) is removed to expose the coalbed, which is then 

mined with surface excavation equipment such as draglines, power shovels, bulldozers, loaders, and augers. Surface 

mines include: area, contour, open-pit, strip, and auger mines. 
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Figure 1 

Estimated Fugitive CH4 Emissions from U.S. Coal Mines (2006) 

5.40 

2.3 (8%)

(4%)

6.3 

(10%)

14.0 

(22%)

35.9 

(56%)

Underground mines

(ventilation and

degasification)

Surface mines

Post mining

(underground)

Post mining (surface)

Abandoned underground

mines

Source: Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and 

Sinks: 1990-2006, USEPA #430-R-08-005, April 2008 

Coal mining operations require a wide variety of equipment that uses coal, distillate, residual fuel 

oil, natural gas, gasoline, and purchased electricity, and hence, results in emissions from 

combustion. An estimated 9 million metric tons of CO2 equivalent emissions were associated 

with energy use in coal mining operations in the United States in 2006 (see discussion below). 

Types of Emissions to be Reported

i) Process Emissions 

Five categories of CH4 emissions from the coal mining sector are addressed in the U.S. national 

inventory: 

• Ventilation air from underground mines 

• Degasification systems at underground coal mines 

• Fugitive emissions from post-mining operations 

• Surface mines 

• Abandoned and/or closed mines. 

The nature of each of these sources of emissions, and considerations associated with various 

options for inclusion in the proposed rulemaking, are discussed in more detail below. 

Underground mines – mine ventilation emissions

Mine ventilation emissions from underground coal mines account for the largest share of fugitive 

CH4 emissions -- 32.8 million metric tons of CO2e, or 56% of all U.S. coal mining fugitive 

emissions. In underground mines, CH4 can create an explosive hazard to coal miners. To ensure 

mine safety, fresh air is circulated through underground coal mines using ventilation systems to 
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dilute in-mine concentrations of CH4 to well below explosive levels. In the U.S., mine safety 

authorities at the Mine Safety and Health Administration (MSHA) regulate these concentrations. 

Typically, CH4 concentrations in ventilation air range from 0.1% to 1.0%. These ventilation 

systems can exhaust significant amounts of CH4 to the atmosphere in relatively low 

concentrations. 

MSHA field inspectors, as part of periodic mine safety inspections, conduct air sampling 

according to well-defined procedures for mines with CH4 emissions exceeding defined 

thresholds (see discussion below). The results of this sampling currently provide the basis for 

estimating CH4 emission rates from ventilation systems at underground coal mines for the EPA 

Inventory of U.S. Greenhouse Gas Emissions and Sinks (EPA, 2008). 

Underground mines – Degasification 

In many cases, it is necessary to supplement the mine ventilation with a CH4 degasification 

system. Methane drainage must be performed when the ventilation system cannot dilute CH4

emissions from the mine to below statutory levels. Mines that employ degasification systems 

also liberate large quantities of CH4 in relatively high concentrations. Degasification systems 

use wells drilled from the surface or boreholes drilled inside the mine to remove CH4 before, 

during, or after mining operations. These degasification systems usually consist of a network of 

boreholes, pumping systems, and gas gathering pipelines. The majority of the CH4 liberated 

from degasification systems is input into natural gas pipelines, is used for energy on site, or is 

combusted by flaring. Of the 21.8 million metric tons CO2e of CH4 liberated by degasification 

systems in 2006, 18.7 million metric tons CO2e of CH4 was combusted, and 3.1 million metric 

tons were emitted to the atmosphere. 

In 2006, twenty U.S. coal mines supplemented their ventilation systems with active 

degasification systems. Thirteen coal mines collected CH4 from degasification systems and sold 

this gas to a pipeline. One coal mine used CH4 from its degasification system onsite to heat mine 

ventilation air. Two of the coal mines that sold gas to pipelines also used CH4 to generate 

electricity or fuel a thermal coal dryer on site (EPA 2008). 

Before mining, drainage wells are drilled through a coal seam or seams to pre-drain the CH4. 

The wells are normally placed in operation 2 to 7 years ahead of mining and the coal seam is 

often hydraulically fractured to remove much of the CH4 and water from the seam. These premine drainage wells can recover relatively high-quality gas from the coal seam and the 

surrounding strata in most cases because the CH4 is not diluted by ventilation from the mine. 

The total amount of CH4 recovered depends on site-specific conditions such as the gas content of 

the coal seams and surrounding strata, permeability of the geologic materials, the drainage time, 

the amount of pressure differential applied, and other characteristics of the geologic and 

extractive systems. Such pre-mine drainage wells can recover 50% to 90% of the gas content of 

the coal. 

Horizontal holes can also be drilled into the coal seam from development entries in the mine to 

drain CH4 from the unmined areas shortly before mining, reducing the flow of CH4 into the 

mining section. In this case, because CH4 drainage occurs only from the mined coal seam, and 

the period of drainage is relatively short, and the recovery efficiency of this technique is 

relatively low -- normally, about 10% to 20% of the CH4 is recovered from the drilled area. 

Higher recoveries can generally be achieved in room-and-pillar sections by drilling longer holes 

farther in advance of mining. 
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Gob wells and cross-measure bore holes recover CH4 from the overburden (i.e., gob area) after 

mining of the seam, primarily in longwall mines. The gob area is a fractured zone in a mine seam 

that is the result of the relaxation and collapse of strata surrounding the mined coal seam. Such 

“gobs" can be significant sources of CH4 emissions. Gob gas vent holes drilled into mine gobs 

after mining generally vent the degasified CH4 directly to the atmosphere. These are typically 

equipped with exhausters on the surface to draw the gas from the gob. Monitoring equipment 

may or may not be equipped as part of the surface infrastructure for these gob gas vent wells, but 

would generally be in place where the collected gas is sold or used onsite. 

In many cases, the CH4 recovered from degasification systems can be productively utilized. 

Methane emitted from coal mine ventilation systems constitutes an unused potential source of 

energy. Utilization technologies for recovered coal mine CH4 fall into three broad categories: 1) 

natural gas substitution, 2) direct use at or near the mine site, and 3) electricity generation and/or 

cogeneration. High quality coal mine gas may require only modest processing before 

compression and pipeline injection, while medium-quality coal mine gas may require some 

processing or upgrading, but then can be used in nearby boilers or furnaces, or in internal 

combustion engines and gas turbines. 

In cases where the sale and/or use of coal mine gas would not be profitable or feasible, an 

alternative to utilization for mitigating coal mine CH4 emissions is to destroy the CH4 via 

flaring, thus converting the higher global warming intensity CH4 into lower intensity CO2. 

Procedures to estimate CH4 emissions from degasification will include estimating “emissions 

avoided.” Estimating these “emissions avoided” has value in several respects. First, it provides 

a method for verifying emissions estimates for gassy mines. Second, it provides a mechanism 

for documenting current actions by operators to reduce emissions, even if these reductions were 

primarily implemented for safety, rather than GHG emissions reduction, reasons. 

Emissions from post mining operations

Other sources of CH4 emissions from the mining sector relate to activities after the coal is mined, 

and include coal piles and coal storage areas, coal transport operations, and the coal preparation 

plant. Estimated post-mining emissions accounted for 14% of all coal mining sector fugitive 

CH4 emissions in 2006, representing 8.6 million metric tons of CO2e. These emissions apply to 

both underground and surface coal mines. For these sources of fugitive emissions, emissions 

estimates are generally developed for emissions inventory purposes by using standard region or 

basin-specific emission factors, multiplied by rates of coal production, applied to all “postmining” activities. Measuring and/or monitoring emissions from these operations would be 

difficult, since no robust monitoring methodology has been developed for these emissions. 

Moreover, existing emission factors are highly uncertain; and are established based on very 

sporadic data, if based on any emissions data at all. 

One category of post-mining emissions that could be considered for monitoring is emissions 

from coal preparation plants. On April 16, 2008 (Federal Register: April 28, 2008, Vol. 73, No. 

82, pp. 22901-22913), EPA proposed revisions to emissions control requirements for new coal 

preparation plants. These proposed new source performance standards (NSPS) would apply to 

new coal preparation plants that process more than 200 tons of coal per day. The proposed NSPS 

would apply to new, modified, and reconstructed coal preparation plants and reflect 

improvements in emission control technologies for particulate matter (PM) that have been 

developed since the original NSPS for these sources were issued in 1976. 
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As part of these new proposed NSPS requirements, EPA is proposing to require 

owners/operators of thermal dryers and pneumatic coal-cleaning equipment at constructed, 

modified, or reconstructed coal preparation plants to either install and operate a PM continuous 

emissions monitoring system (CEMS), or to conduct annual PM performance tests. A possible 

logical extension of this proposal would be to also include monitoring for fugitive CH4 emissions 

from these coal preparation plants. For the installation of a new CEMS, the incremental costs of 

adding CH4 monitoring capability to the PM monitoring capability would be relatively small, 

since the dual monitoring capability can be designed within the same system. Retrofitting after 

the fact to add CH4 monitoring would cost more. 

It is important to note that fugitive emissions from coal preparation plants represent a small 

portion of the total emissions from the coal mining sector. In fact, the vast majority of GHG 

emissions from a coal preparation plant correspond to the fuel consumed for various operations 

such as coal drying. Fugitive CH4 emissions will only correspond to any remaining CH4 emitted 

from the coal during processing. 

Emissions from surface mines

Surface coal mines release CH4 as the overburden is removed and the coal is exposed. The level 

of estimated emissions from surface mines is much lower than that from underground mines, 

representing 22% of all coal mine fugitive emissions, amounting to 14.0 million metric tons of 

CO2e. Moreover, similar to that for post mining operations, emissions for surface mining are 

generally estimated for national inventory purposes by using standard region or basin-specific 

emission factors, multiplied by rates of coal production, applied to all surface mining activities. 

Monitoring emissions from these operations would be difficult, since; again, no robust facilitylevel methodology has been developed. Moreover, existing emission factors are highly 

uncertain; and are established based on very sporadic data, if based on any emissions data at all. 

Emissions from abandoned mines

When coal mines are no longer operated to produce coal, they are known as closed or 

"abandoned" mines. Even though active mining no longer occurs, these abandoned mines can 

still produce CH4 emissions from diffuse vents, fissures, or boreholes. This CH4 can be 

deliberately extracted and used to generate power or for other end uses. 

Methane liberated from abandoned mines is estimated to be 6.8 million metric tons of CO2e per 

year, of which an estimated 1.4 million metric tons of CO2e per year is recovered and used (EPA 

2008). Therefore, an estimated 5.4 million metric tons of CO2e is emitted per year, representing 

8% of all fugitive CH4 emissions from coal mines. 

There are several thousand abandoned coal mines in the United States. Of these, EPA has 

identified some 400 abandoned mines that are considered "gassy," and has developed profiles of 

potential projects at abandoned mines that may be good candidates for project development 

(EPA 2004). 

Measuring and/or monitoring emissions from abandoned mines would be difficult. There is 

currently no robust way to measure fugitive emissions from individual abandoned mines. 

Measuring at discrete borehole/wellhead sites would not adequately capture the emissions 

seeping out of various other fissures and leakage points. Moreover, in many cases, it can be 

quite difficult to identify owners of abandoned mine sites, i.e., it would be difficult to identify the 

responsible parties to monitor and report. Even where the owner is known, abandoned sites are 
6/11/2010 8

unmanned and often remote; and it would be burdensome to require company personnel to travel 

to each abandoned mine site to measure emissions, along with being expensive and resourceintensive, especially given the relatively small contribution abandoned mines make to total GHG 

emissions in the coal mining sector. 

ii) Combustion Emissions 

Estimates of fuel consumption in the mining sector are reported by the Bureau of the Census 

(Census, 2004a, 2004b, 2004c, 2004d) for 2002, which include coal consumed directly in mining 

operations, distillate, residual fuel oil, natural gas, gasoline, and purchased electricity. The 2002 

fuel consumption estimates were updated to 2006 based on 2006 levels of coal production, and 

based on this, an estimated 9 million metric tons of CO2 emissions were associated with energy 

use in coal mining operations in the United States in 2006. The majority of these emissions 

result from the generation of electricity purchased to support mining operations. The CO2

emissions from only on-site combustion (the value used in this analysis) are estimated to be 3.62 

million metric tons. 

2. Options for Reporting Thresholds 

Several different thresholds were considered for CH4 emissions from underground coal mines 

based on the data in MSHA databases, and the Inventory of U.S. Greenhouse Gas Emissions and 

Sinks: 1990-2006 (EPA, 2008). The estimated emissions and facilities covered are summarized 

in Table 1 below for different emissions threshold levels, based on 2006 emissions levels. 

a. Options Considered

5.1 Emissions-based thresholds 

Data were collected and analyzed to evaluate several potential reporting thresholds. The primary 

options were based on the CH4 liberated from mines: 

i. An emissions threshold of 1,000 mtCO2e 

ii. An emissions threshold of 10,000 mtCO2e 

iii. An emissions threshold of 25,000 mtCO2e 

iv. An emissions threshold of 50,000 mtCO2e 

v. An emissions threshold of 100,000 mtCO2e 

5.2 Other threshold options

In general, MSHA samples (quarterly or more frequently) CH4 emissions for mines liberating 

more than 100,000 cubic feet of CH4 per day from ventilation systems,

2

which is equivalent to 

about 15,000 metric tons CO2e per year. MSHA also samples methane from mines with special 

conditions, such as safety concerns. Of the over 600 underground coal mines operating in the 

U.S. according to EIA, ventilation air emissions based on MSHA inspections were reported and 

electronically accounted for in 128 mines in 2006. 

 

2

Personal communication, Fred H. Menke, Jr., Supervisory IT Specialist, Mine Safety and Health Administration, 

to Michael Godec, Advanced Resources International, April 25, 2008. 
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Table 1 

Threshold Analysis for Underground Coal Mining 

Emissions Coveredc Facilities Covered 

Source 

Category 

Threshold 

Level 

(Metric 

tons CO2e 

per year) 

Total 

National 

Emissionsa

(Metric 

tons 

CO2e) 

Number 

of 

Facilitiesb

Process 

Emissions 

(Metric 

tons 

CO2e/yr) 

Estimated 

Combustion 

CO2

Emissions 

(Metric 

tons/yr) 

Metric 

tons 

(CO2e/yr) 

Percent Number Percent 

Underground 

Coal Mining 

100,000 39,520,000 612 30,649,815 405,040 31,054,856 79% 53 9% 

Underground 

Coal Mining 

50,000 39,520,000 612 32,316,726 438,262 32,754,988 83% 77 13% 

Underground 

Coal Mining 

25,000 39,520,000 612 33,082,854 453,531 33,536,385 85% 100 16% 

Underground 

Coal Mining 

MSHA 

quarterly 

reporting 

threshold 

39,520,000 612 33,364,265 459,140 33,823,404 86% 114 19% 

Underground 

Coal Mining 

10,000 39,520,000 612 33,465,371 461,155 33,926,526 86% 122 20% 

Underground 

Coal Mining 

1,000 39,520,000 612 33,483,922 461,524 33,945,446 86% 125 20% 

a Estimated national fugitive CH4 emissions for underground mining from 2006 Annual Inventory (Table 3-

26) (http://epa.gov/climatechange/emissions/downloads/08_Energy.pdf); plus estimated combustion 

emissions of 3.62 million metric tons, excluding those associated with purchased electricity. 

b Number of active underground coal mines in the U.S. in 2006 according to the Energy Information 

Administration (EIA 2007). 

c Based on the fugitive CH4 emissions volumes reported for individual mines in the MSHA database 

"Analysis of 2006 Emissions Data for Active Underground Mines,” along with estimated combustion-related 

emissions from these mine sites, but not including emissions associated with purchased electricity. 

Estimates made for fuel combustion emissions based on Bureau of Census data on fuel use as a % of 

coal mined (for gassiest mines) or as % of vented emissions for less gassy mines. Combustion emissions 

calculated as approximately 1% to 3% of vented emissions, on CO2e basis. 

b. Emissions and Facilities Covered Per Option 

CH4 emissions from the 114 of the 128 underground coal mines reporting ventilation emissions 

in 2006 of over approximately 15,000 metric tons of CO2e per year (equivalent to the current 

MSHA threshold for accounting for emissions from gassy mines) accounts for 86% of the 39.5 

million metric tons estimated to be emitted by underground coal mines (35.9 million metric tons 

from CH4 emissions and 3.6 million metric tons from combustion emissions, excluding those 

emissions associated with purchased electricity). These 114 mines represent 19% of the active 

underground mines in the United States. Increasing the reporting threshold to 25,000 metric 

tons of CO2e per year would reduce the number of reporting mines by 14 to 100 and would 

reduce the amount of total emissions reported from this sector by 3%. If no threshold is 

established, and all mines must report, this will add nearly 500 mines to the number required to 
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report, but these 500 mines would only represent another 14% of the total GHG emissions from 

underground coal mines. 

Other options for establishing thresholds could be based on other factors, such as coal 

production. An option using coal production as a threshold was considered, but not proposed 

because coal production is not closely correlated to CH4 liberation. Alternative threshold levels 

for reporting could also be considered. However, thresholds for and procedures for sampling 

CH4 liberation above defined levels are already established by MSHA, utilizing this threshold is 

the most logical and least burdensome method for establishing GHG monitoring and reporting 

thresholds for the coal mining sector, while capturing a majority of GHG emissions from the 

sector. 

3. Existing Relevant Reporting Programs/Methodologies 

For this proposal, EPA reviewed several protocols and programs with guidance monitoring 

and/or estimating GHG from this source, including the 2006 IPCC GL, U.S. GHG Inventory, 

California AB32 (“CARB rule”), EIA’s 1605(b) program, EPA’s Coalbed Methane Outreach 

Program (CMOP), MSHA, BLM, and Australia’s National Mandatory GHG Reporting Program 

(draft). 

In general, there are three methods for monitoring emissions: the use of emission factors, 

periodic sampling of CH4 concentrations and flow, and direct measurement. 

This section presents the existing relevant monitoring methods by coal mine CH4 sources. 

Underground mines – mine ventilation 

MSHA regulatory requirements specify that qualified and trained MSHA field inspectors 

perform periodic mine safety inspections at all underground coal mines in the United States, and 

as part of these inspections, test CH4 emissions rates at each coal mine according to MSHAapproved sampling procedures.3

 Air sampling is conducted by MSHA inspectors collecting air 

bottle samples at a mine's main fans, along with a total quantity air ventilation volume reading. 

Sampling procedures and equipment are approved by MSHA (NIOSH 2006). The sample bottles 

are sent to the MSHA lab for analysis and the results are provided back to the MSHA district 

offices for inclusion in the inspection report. The results are also maintained separately by the 

district ventilation group. 

In general, air sample readings with CH4 concentrations below 50 ppm are considered nondetectable. Air samples and ventilation readings are taken annually unless CH4 emission rates 

exceed 100,000 standard cubic feet per day, where quarterly sampling is then conducted. MSHA 

electronically keeps track of emissions for mines liberating more than 100,000 cubic feet of CH4

per day,

4

which is equivalent to about 15,000 metric tons CO2e per year. If emissions levels are 

greater that 200,000 cubic feet per day, according to Section 103 (i) of the Federal Mine Safety 

 

3 MSHA requires that monitoring be performed by a qualified person using CH4 monitoring devices approved by 

MSHA (under 30 CFR Parts 18,21,22,23,27, and 29); and that are maintained in permissible and proper operating 

condition and calibrated with a known CH4-air mixture at least once every 31 days. 

4

Personal communication, Fred H. Menke, Jr., Supervisory IT Specialist, Mine Safety and Health Administration, 

to Michael Godec, Advanced Resources International, April 25, 2008. 
6/11/2010 11

& Health Act of 1977 (Public Law 95-164), more frequent inspections are mandated, with the 

frequency determined by the daily CH4 liberation rate calculated for the mine. 

For the mines with emissions exceeding 100,000 cubic feet per day, annual ventilation emissions 

estimates are developed by averaging the four quarterly tests, and are accurate to the extent that 

the data collected are representative of actual emissions. 

In addition, for federal coal leases where degasification systems are in place, the Bureau of Land 

Management (BLM) requests that mine operators provide CH4 emissions rates from both 

degasification and ventilation systems to BLM. Operators currently provide this information 

voluntarily; it is not a requirement either by regulation or under their federal coal lease terms.5

For this source, the IPCC Guidelines recommend that where mine-specific measurement data are 

available, it is good practice to use a method comparable to that based on the MSHA sampling 

results. In situations when mine-specific measurement data are available only for a subset of 

underground mines (which generally should not be the case in the United States), the Guidelines 

specify that emissions from the remaining mines can be calculated with emission factors based 

on the mines with measurement data. These emission factors can be based on specific emission 

rates derived from operating mines within the same basin, or on the basis of mine-specific 

properties, such as the average depth of the coal mines. When no mine-specific data are 

available, but country- or basin-specific data are, the IPCC Guidelines suggest that it is good 

practice to employ a Tier 2 method. Where no data (or very limited data) are available, the 

Guidelines specify that it is good practice to use a Tier 1 approach, provided underground coal 

mining is not a key sub source category. 

To calculate emissions from ventilation at underground mines in the Inventory of U.S. 

Greenhouse Gas Emissions and Sinks (EPA, 2008), EPA uses the IPCC guidelines, and CH4

emissions data collected through the MSHA sampling program process, which also serves as the 

basis for EPA’s CMOP emissions estimates from this source. 

DOE 1605(b) inventory reporting guidelines specify that mines with undetectable CH4 levels can 

calculate ventilation emissions by multiplying a flow rate of 3,000 cubic feet per minute by an 

assumed CH4 concentration of 0.05% to derive a CH4 emissions rate (DOE 2007). DOE 1605(b) 

guidelines otherwise provide the same methodology as the Inventory of U.S. Greenhouse Gas 

Emissions and Sinks (EPA, 2008) and IPCC. 

Australia’s National Mandatory GHG Reporting Program (draft) (Australia 2008) recommends a 

methodology comparable to that in the 2006 IPCC Guidelines. 

Recent draft reporting regulations proposed by the California Air Resources Board (CARB 2008) 

do not prescribe any approach for estimating emissions from coal mining operations; these only 

propose the use of emission factors to estimate emissions from post-mining coal storage and 

handling activities (see discussion below). 

Underground mines – degasification 

As discussed above, of the 20 U.S. coal mines deploying degasification systems in 2006, 13 

mines sent this gas to a pipeline. It is common practice for these mines to monitor the volume of 

gas produced and delivered to the pipeline (which also monitors these volumes). Coal mines 

 

5

Personnel communication, Desty Dyer, U.S. Bureau of Land Management (BLM), Montrose Field Office, to 

Michael Godec, Advanced Resources International, Inc., June 6, 2008 
6/11/2010 12

using CH4 from degasification systems on site to heat mine ventilation air are also likely to 

monitor the volumes of CH4 produced. 

In contrast to CH4 emissions from ventilation systems, no agency requires mines to report the 

amount of CH4 they drain from degasification systems. MSHA collects information about the 

presence and type of degasification systems in some mines, but does not collect quantitative data 

on the amount of CH4 liberated. As mentioned above, BLM requests that mine operators on 

federal coal leases provide information on CH4 emissions from both ventilation and 

degasifications systems. Most mines do provide degasification information voluntarily to 

CMOP. 

As part of the annual U.S. inventory, EPA estimates the volume of CH4 drained assuming 

drainage efficiencies based on information obtained from MSHA district offices or from 

information provided by operators. Some of the coal mines employing degasification systems 

have provided EPA with information regarding CH4 liberated from their degasification systems. 

In cases in which mines sell CH4 recovered from degasification systems to a pipeline, gas sales 

are used to estimate CH4 liberated from degasification systems. For those mines that do not sell 

CH4 to a pipeline and/or do not currently provide information to EPA, CH4 liberated from 

degasification systems is estimated by EPA based on the type of system employed. For example, 

for coal mines employing gob wells and horizontal boreholes, the methodology assumes that 

CH4 volumes liberated from degasification systems account for 40% of total CH4 liberated from 

the mine. This is also the recommended method presented in the DOE 1605(b) Guidelines. 

The IPCC Guidelines suggest a similar approach. Where ventilation can be measured (or can be 

estimated from measurements from similar mines in the same basin or region), but not 

degasification volumes, they suggest that reporters estimate the amount degasified (although no 

methodology is specified) and use appropriate methods for accounting for the disposition of the 

degasified CH4 (e.g.; vented, flared, sold, consumed on-site). Several suggested approaches are 

provided in the Guidelines. Australia’s National Mandatory GHG Reporting Program (draft) 

(Australia 2008) recommends a methodology comparable to that in IPCC Guidelines. 

Post mining operations

For post-mining operations, since mine-specific emissions measurements are not available, 

emissions estimates for the U.S. inventory are developed by using basin-specific coal production 

multiplied by a basin-specific emission factor. Emission factors for surface mined coal were 

developed from the in situ CH4 content of the surface coal in each basin. Furthermore, the postmining emission factors used were estimated to be 25 to 40% of the average in situ CH4 content 

in the basin. Thus, for the current inventory, the post-mining emission factor was determined to 

be 32.5% of the in situ CH4 content in the basin. 

The IPCC Guidelines and the DOE 1605(b) guidelines also recommend this approach for 

inventory development purposes, and CARB recommends this approach (for coal storage) as part 

of its mandatory greenhouse gas reporting program. Australia’s National Mandatory GHG 

Reporting Program (draft) (Australia 2008) recommends a methodology comparable to that in 

IPCC Guidelines. 

Surface mines

Similarly, surface mining emissions estimates for the U.S. inventory are also developed by using 

basin-specific coal production multiplied by a basin-specific emission factor. Emission factors 
6/11/2010 13

for surface mined coal were developed from the in situ CH4 content of the surface coal in each 

basin. Surface mining emission factors were estimated to be from 1 to 3 times the average in situ 

CH4 content in the basin. For the current inventory, the surface mining emission factor was 

determined to be twice the in situ CH4 content in the basin. 

Again, the IPCC Guidelines and the DOE 1605(b) guidelines also recommend this approach for 

inventory development purposes, as does Australia’s National Mandatory GHG Reporting 

Program (draft). 

Abandoned mines

EPA (EPA 2004) and the IPCC (IPCC 2006) have developed emissions estimation 

methodologies for abandoned underground mines for emissions inventory purposes. EPA 

developed emissions estimation methodologies for abandoned or closed underground mines for 

emissions inventory purposes based on the time since abandonment; gas content and adsorption 

characteristics of the coal, CH4 flow capacity of the mine; mine flooding; the presence of vent 

holes, and mine seals. The IPCC methodology is based on the elapsed time since abandonment, 

the mine's initial gassiness, and the extent to which the mines have become flooded. 

Australia’s National Mandatory GHG Reporting Program (draft) (Australia 2008) recommends a 

methodology comparable to that in IPCC Guidelines. 

DOE 1605(b) guidelines contain no specific recommendations for estimating emissions from 

abandoned coal mines. 

4. Proposed Monitoring Methods 

a. Monitoring Methods Considered

Emissions in Ventilation Air

i. Option 1: Continuous Monitoring 

The direct measurement option considered would involve implementing continuous monitoring 

systems in underground coal mine ventilation shafts. This option builds upon the fact that 

continuous monitors are already in place throughout all underground coal mines. For 

compliance with this GHG emissions monitoring rule, such monitoring devices could be placed 

at or near the mine vent outflows where the air samples are taken by MSHA inspectors. 

Federal safety standards6 mandate that, “when 1.0 percent or more CH4 is present in a working 

place or an intake air course [...] electrically powered equipment in the affected area shall be deenergized, and other mechanized equipment shall be shut off.” A flammable mixture of CH4 and 

air can be ignited by electric arcs and sparks, open flames, or by the heat of friction between the 

cutting bits of mining equipment and the mine rock immediately above or below the coal. 

To ensure that CH4 levels in underground coal mines remain below combustible levels, 

continuous monitoring devices are in operation within underground coal mines. MSHA 

regulations require that wall and/or machine-mounted CH4 monitors are mounted at various 

locations and on certain types of machinery to continuously monitor mine air quality. These 

 

6 Code of Federal Regulations, Title 30, Part 75: Mandatory safety standards--underground coal mines 
6/11/2010 14

monitors are certified under 30 CFR Part 27,7which requires monitoring system design and 

operation that prevents the mining equipment from operating unless the CH4 monitoring system 

is functioning. The CH4 monitoring system has a warning device that activates when the CH4

concentration is above 1.0% to 1.5%, and has a means to shut off power to the equipment when 

the CH4 concentration is above 2.0%. 

Methane detectors fall into two categories: portable CH4 detectors and wall or machine-mounted 

monitors. Most CH4 detectors used in mining use a catalytic heat of combustion sensor to detect 

CH4 and other combustible gases. These have been proven reliable through many years of 

operation. For detection of CH4, proper operation of catalytic heat of combustion sensors 

requires both a CH4 concentration below 8% (by volume) and oxygen content above 10% -- 

requirements that are usually satisfied in mining applications. 

Some detectors measure the CH4 concentration by using infrared absorption as an operating 

method. These infrared detectors can measure accurately without oxygen and at concentrations 

up to 100% CH4. However, water vapor and dust can cause operating difficulties. In some 

mines, the CH4 may be accompanied by ethane, which can produce an exaggerated infrared 

detector response. 

Machine-mounted CH4 monitors are usually mounted on mining and tunnel-boring machines. 

They are designed to have their readout display separated from the sensing head so that the 

readout is visible to the machine operator and the sensing head is placed in a location where CH4

is most likely to accumulate. Machine and wall-mounted monitors operate continuously and can 

identify emission peaks. Using machine or wall-mounted monitors could likely improve the 

accuracy of emissions measurements in underground mines, when operated and calibrated 

properly, compared to periodic sampling. The resolution of these monitors can be specified – in 

general, the higher the resolution, the higher the cost. Resolutions at levels lower than the 50 

ppm limit, which characterizes the current MSHA sampling protocol, are certainly achievable. 

Nonetheless, emissions at levels below the resolution of the monitors, if assumed to be zero 

could correspond to an underestimation of emissions. 

The advantage of continuous monitoring is that it takes into consideration any variability in 

emissions from mining operations that may not be represented in periodic sampling. Moreover, 

since such devices are already used within the mine, mine operator personnel are familiar with 

their operation. 

A disadvantage would be the larger costs associated with purchasing and maintaining these 

continuous emissions monitoring systems (CEMS) devices for this application. 

ii. Option 2: Quarterly Sampling of CH4 Content and Gas Flow 

Under this option, coal mine operators would be required to duplicate the MSHA process of 

collecting air samples and ventilation rates, submitting the samples to a lab for analysis, and 

developing estimates of emissions on their own. This would require mine operators to purchase 

sampling equipment, train personnel in their use, develop emissions estimates based on the data 

collected, and report the results. If this option is pursued, the operator would have to incur the 

capital and O&M costs involved in purchasing and maintaining the air sampling equipment, and 

in sending air samples to an independent lab for analysis. 

 

7 A list of approved gas monitors for U.S. mines is available from MSHA’s Approval and Certification Center 

(http://www.msha.gov/TECHSUPP/ACC/lists/27mthmon.pdf) 
6/11/2010 15

Alternatively, the results of MSHA inspections could be used to estimate ventilation air 

emissions. In this case, mines would obtain data from MSHA (it is not currently shared with the 

mine). An advantage of MSHA sampling and reporting is that MSHA inspectors have 

procedures in place, and a high level of QA/QC is established for this process. Minimal 

additional training of operator personnel would be required, the implementation period could be 

almost instantaneous, and the accuracy of emissions estimates would most likely be higher. 

iii. Option 2: More Frequent Sampling 

Sampling could be done more frequently than quarterly. This could provide a more consistent, 

reliable, and representative characterization of fugitive CH4 mine emissions, but at a higher cost. 

iv. Option 3: Simplified Emission Calculation 

This option would involve utilizing the same procedures as recommended by the IPCC and DOE 

1605(b) Guidelines, assuming no mine-specific data were available. For inventory reporting 

purposes, the IPCC Guidelines recommend that when ventilation emissions cannot be measured, 

they can be estimated from measurements from similar mines in the same basin or region. If 

analogous mine-specific data are unavailable, they recommend using basin/region-specific 

emission factors multiplied by production, and representative emissions factors are provided in 

the Guidelines. 

Degasification Systems

(i) Option 1: Continuous Monitoring 

This option involves continuous monitoring of gas recovered from mine degasification systems. 

This option would apply to all degasification wells, including gob gas vent holes and other 

degasification wells that are currently not monitored. 

Approaches for monitoring the volumes of CH4 produced from coal mine degasification systems 

prior to mining use the same general techniques for monitoring gas flows from natural gas 

production wells. Recommendations for improved approaches for both degasification systems 

and monitoring gas flow specifically from degasification wells date back to the mid-1970s 

(Lambert and Trevits, 1978; Diamond, 1994). Degasification systems operate in conjunction 

with the ventilation system and overall mining operations, generally requiring coordinated 

management (using measuring instruments, monitoring, controls, and good communications) to 

optimize overall operations.8

The advantages to this approach are that continuous monitoring provides accurate data and can 

captures seasonal changes in gas flow and concentrations, and that most degasification systems 

where the produced CH4 is sold or used on site for energy generally already have continuous 

monitoring in place. The disadvantage would be the costs incurred by mines that do not 

currently have these systems in place, and the infeasibility of installing and maintaining monitors 

at all degasification sites, some of which are in remote and inaccessible locations. 

ii) Option 2: Sampling of CH4 Content and Gas Flow

This option would involve continuous monitoring for those wells already deploying such 

systems, but would allow periodic sampling for those that do not. For example, gob gas vent 

holes that are currently not monitored could conduct periodic sampling, as could perhaps any 

 

8

http://www.epa.gov/cmop/docs/ggasrecpv.pdf 
6/11/2010 16

other degasification borehole, rather than installing continuous monitoring. For example, weekly 

or monthly sampling at each gob gas vent hole/well could be conducted. While such an 

approach would involve less capital costs, greater labor costs would be involved with traveling to 

each (often remote) well/vent site to take samples. 

If direct measurements of gas volumes are not available for degasification wells, other options 

could be to: (1) use gas sales data, and/or (2) apply an assumed degasification efficiency based 

on the technology used. This is the procedure suggested in the IPCC and DOE 1605(b) 

Guidelines, and is the method currently used in the U.S. inventory if underground coal mine 

degasification volumes are not available. For example, for coal mines employing gob wells and 

horizontal boreholes, the methodology assumes that degasification emissions account for 40% of 

total CH4 liberated from the mine. Gas sales data, if available, would be a direct proxy for the 

volume of methane produced from degasification systems, and is more accurate than an assumed 

degasification efficiency. While simple in application, the use of an assumed degasification 

efficiency is highly uncertain, since such an efficiency is clearly a function of many minespecific parameters that can vary considerably from mine-to-mine. 

Option 3: Simplified Emission Calculation 

This option would involve utilizing the same procedures as recommended by the IPCC and/or 

DOE 1605(b) Guidelines, assuming no mine-specific data were available. For GHG inventory 

reporting purposes, the IPCC Guidelines recommend that when recovered gas from 

degasification systems cannot be measured, they can be estimated from measurements from 

similar mines in the same basin or region. If analogous mine-specific data are unavailable, they 

recommend using basin/region-specific emission factor multiplied by production, and 

representative emissions factors are provided in the Guidelines. Again, similar to that discussed 

above, while simple in application, the use of simplified emissions calculation approach is highly 

uncertain, since emission are a function of many mine-specific parameters that can vary 

considerably from mine-to-mine. 

Methane Combustion at Ventilation or Degasification Systems

(i) Option 1: Continuous Monitoring 

This option involves continuous monitoring of the disposition of gas recovered from coal mines. 

Although this measurement is continuous, reporting would only be annual. This option would 

apply to all combustion sites, including those occurring at gob gas vent holes and other wells that 

are currently not monitored. 

Approaches for monitoring the volumes of CH4 combusted are generally well established. Many 

mines already monitor the amount of CH4 liberated from coal mine degasification that is 

combusted on site. 

The advantages to this approach are that continuous monitoring provides accurate data and can 

captures seasonal changes in gas flow, concentrations, energy use, and combustion efficiencies, 

and that most degasification systems already have continuous monitoring in place. The 

disadvantage would be the costs incurred by mines that do not currently have these systems in 

place. 

(ii) Option 2: Simplified Combustion Calculation 
6/11/2010 17

This option would involve utilizing the same procedures as recommended by the IPCC and/or 

DOE 1605(b) Guidelines, assuming no mine-specific data were available. For GHG inventory 

reporting purposes, the IPCC Guidelines recommend that when combusted gas cannot be 

measured, simple combustion calculations be used. 

5. Procedures for Estimating Missing Data 

Options and considerations for missing data vary will vary depending on the proposed 

monitoring method. In general, each option would require a complete record of all measured 

parameters and parameters determined from company records that are used in the GHG 

emissions calculations (e.g., carbon contents, monthly fuel consumption, etc.). Therefore, 

whenever a quality-assured value of a required parameter is unavailable (e.g., if a monitor or 

CEMS malfunctions during unit operation or if a required fuel input parameter is not obtained), a 

substitute data value for the missing parameter must be used in the calculations. 

In addition, since periodic inspections are performed on all underground coal mines, data on CH4

concentrations (above 50 ppm) and ventilation rates exist for all mines. For mines below the 50 

ppm “detectable” threshold, estimates could be made for emission rates assuming some value for 

CH4 concentrations (say 25 ppm). However, it again should be emphasized that the vast 

majority of emissions from underground coal mines come from roughly 1/6 of the gassiest 

underground coal mines. 

For emissions avoided from degasification systems, methods are described above for estimating 

volumes for CH4 recovered (Option 3) should recovered volumes not be known. 

For missing gas flow or gas recovery data, the substitute data value could be the arithmetic 

average of the quality-assured values of that parameter immediately preceding and immediately 

following the missing data incident. If, for a particular parameter, no quality-assured data are 

available prior to the missing data incident, the substitute data value shall be the first qualityassured value obtained after the missing data period. 

EPA considered not deducting CH4 combustion that was not recorded, but not including CH4

recovery could greatly overestimate a facility’s emissions. On the other hand, allowing extended 

periods of missing data provides a disincentive to repairing the monitoring system. 

6. QA/QC and Verification Requirements 

In addition, mines should conduct quality assurance and quality control of emission estimates 

reported. Facilities are encouraged to prepare an in-depth quality assurance and quality control 

plan which would include checks on the data collected, and the calculations performed to 

estimate GHG emissions. 

MSHA has established specific regulatory requirements for maintaining and ensuring the 

accuracy of mine sampling processes and for the operation of in-mine monitors. In particular, 30 

CFR Part 75 specifies requirements for the maintenance and use of in-mine CH4 monitors and 

for portable air quality detectors and measurement devices. The section also sets forth 

requirements for ensuring that MSHA inspectors are trained and certified to take samples, and 

operators responsible for in-mine monitoring systems must also be certified. 

Similarly, since they are used to register volumes for gas sales, existing monitors for measuring 

gas produced from degasification systems are considered to be accurate, and both sellers and 
6/11/2010 18

buyers of the gas produced have a vested interest in ensuring that the volumes recovered are 

accurate. 

7. Reporting Procedures 

For underground coal mines, the issues to consider with regard to reporting relate both to the 

party responsible for reporting emissions to EPA, and to the frequency of reporting. In the case 

of the reporting party, options to consider include whether MSHA does the reporting to EPA (of 

emissions from ventilation systems), or if the operator should be responsible for reporting. 

Recovered CH4 volumes from degasifications systems (emissions avoided) will be reported by 

the operator. 

In terms of frequency, options considered include annual, quarterly, and, perhaps, even more 

frequent reporting. 

The issues (other than frequency, as noted above) to consider are somewhat different for 

reporting of emissions from ventilation systems or emissions avoided from degasification 

systems, so each of these two areas are discussed separately below. 

Emissions in Ventilation Air

With regard to mine CH4 ventilation emissions, the information currently collected by MSHA 

(CH4 concentration, ventilation flow rates, major changes in mine activity, etc.) should be 

sufficient to support implementation of Options 2, 3, or 4, discussed above. However, current 

CH4 emissions data collection and reporting are conducted by MSHA field inspectors, with the 

results reported to and maintained by MSHA district offices. In general, mine operators are 

currently not provided a copy of the results of the sampling or the estimates made for CH4

emissions, unless emission levels are of concern to MSHA. 

As discussed above, MSHA currently voluntarily provides EPA with its mine-by-mine estimates 

of annual CH4 emissions for the gassiest mines. This provides the basis for both EPA’s estimates 

of coal sector emissions in the national inventory (EPA 2008), as well as providing the Coalbed 

Methane Outreach Program (CMOP) its basis for identifying opportunities for CH4 recovery at 

U.S. coal mines (EPA 2005). However, in developing its annual emission estimates, MSHA 

develops these estimates by averaging the sample data results from quarterly inspections. 

Several options are available for reporting the results of GHG emissions monitoring in the coal 

mining sector. These are: 

• MSHA continues to collect ventilation air samples and rates, and from these develop 

estimates of GHG emissions for all mines that exceed a defined CH4 emissions threshold 

(currently 100,000 cubic feet per day). Then, MSHA would be responsible for reporting 

CH4 emissions estimates directly to EPA. Under this option, the incremental burden on 

both coal mine operators and MSHA would be small. 

• MSHA continues to collect ventilation air samples and rates, and from these develop 

estimates of GHG emissions for all mines that exceed the defined CH4 emissions 

threshold. Then, MSHA would make these emissions estimates available to mine 

operators, and the operators would be responsible for reporting emissions levels to EPA. 

Under this option, the burden on MSHA would be the same – it would now just provide 
6/11/2010 19

its emissions estimates back to the operator, rather than EPA. In this case, the burden on 

the operator would be greater, since it would now need to report to EPA. 

• MSHA would continue to collect ventilation air samples and rates, but provide just the 

sampling results to the operator, and the operator would develop its own estimates of 

GHG emissions from these sample results, and report emissions estimates to EPA. Here, 

the burden on MSHA would actually be reduced somewhat from the above options 

(though it would still need to send the operators the sampling results), but the burden on 

the operator would be considerably greater. 

• Coal mine operators would duplicate the MSHA process, by collecting air samples and 

ventilation rates, submitting the samples to a commercial lab for analysis, developing 

estimates of CH4 emissions, and reporting this information to EPA. This would impose a 

burden on the operators. 

Currently, although MSHA collects samples quarterly for the gassy mines, emissions estimates 

are only developed on an annual basis. If quarterly reporting is implemented, this would require 

that MSHA develop quarterly, rather than annual, CH4 emissions estimates, and report these 

either to EPA or to the mine operator. 

If mine air ventilation emissions are monitored using a CEMS, the operator would be responsible 

for reporting, at the frequency specified (annual, quarterly, etc.). 

Under any of the reporting options, it would also be expected that operators should also report 

any CH4 emissions from ventilation air that are destroyed or utilized. This data is presumably 

automatically collected by the installed equipment. It is also recommended that operators report 

the number of days in a quarter that the mine is shut down. 

Degasification Systems

With regard to coal mine degasification systems, even when continuous monitoring of CH4

recovered from degasification systems, reporting is done on an annual or quarterly basis. 

Operators would be responsible for reporting the volumes of CH4 recovered from these systems, 

along with the disposition of the CH4 (sold, used on site, and/or destroyed/flared. Reporting 

would be directly to EPA. 
6/11/2010 20

REFERENCES 

Australian Government, Department of Climate Change, National Greenhouse and Energy 

Reporting (Measurement) Technical Guidelines 2008 v1.0, July 2008 

California Air Resources Board, Second 15-Day Modified Regulatory Language For Public 

Comment, Regulation For The Mandatory Reporting Of Greenhouse Gas Emissions, May 15, 

2008 (http://www.arb.ca.gov/cc/reporting/ghg-rep/ghg-rep.htm) 

Diamond, William P., Methane Control for Underground Coal Mines, Bureau of Mines 

Information Circular 9395, 1994 

United States Department of Energy, Office of Policy and International Affairs, Technical 

Guidelines Voluntary Reporting of Greenhouse Gases (1605(B)) Program, January 2007 

http://www.pi.energy.gov/enhancingghgregistry/documents/january2007_1605btechnicalguideli

nes.pdf

Environmental Protection Agency, Methane Emissions from Abandoned Coal Mines in the 

United States: Emission Inventory Methodology and 1990-2002 Emissions Estimates, Coalbed 

Methane Outreach Program, April 2004 

(http://www.epa.gov/coalbed/docs/amm_final_report.pdf) 

Environmental Protection Agency, Identifying Opportunities for Methane Recovery at U.S. Coal 

Mines: Profiles of Selected Gassy Underground Coal Mines: 1999-2003, EPA 430-K-04-003, 

September 2005 (http://www.epa.gov/coalbed/docs/profiles_2003_final.pdf) 

Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 

1990-2006, USEPA #430-R-08-005, April 2008 

(http://www.epa.gov/climatechange/emissions/usinventoryreport.html) 

Energy Information Administration, Annual Coal Report: 2006, DOE/EIA-0584 (2006), 

November 2007 (http://www.eia.doe.gov/cneaf/coal/page/acr/acr_sum.html ) 

Intergovernmental Panel on Climate Change (IPCC), 2006 IPCC Guidelines for National 

Greenhouse Gas Inventories, Gas Inventories, National Greenhouse Gas Inventories Programme, 

Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds.)., 2006 (http://www.ipccnggip.iges.or.jp/public/2006gl/index.htm) 

Lambert, S.W., and M.A. Trevits, “Improved Methods for Monitoring Production from Vertical

Degasification Wells, U.S. Bureau of Mines, Report of Investigations 8309, 1978 

(http://www.cdc.gov/niosh/mining/pubs/pdfs/ri8309.pdf

National Institute for Occupational Safety and Health (NIOSH), Handbook for Methane Control 

in Mining, CDC Information Circular (IC) 9486, June 2006 

U.S. Census Bureau, Bituminous Coal Underground Mining: 2002, 2002 Economic Census, 

December 2004a 

U.S. Census Bureau, Bituminous Coal and Lignite Surface Mining: 2002, 2002 Economic 

Census, December 2004b 

U.S. Census Bureau, Anthracite Mining: 2002, 2002 Economic Census, December 2004c 

U.S. Census Bureau, Support Activities for Coal Mining: 2002, 2002 Economic Census, 

December 2004d 
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