Frequent Questions About Coal Mine Methane
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- Why is EPA concerned about coal mine methane (CMM)?
- What is the difference between coalbed methane (CBM) and coal mine methane (CMM)?
- How does the Coalbed Methane Outreach Program (CMOP) work to reduce methane emissions?
- What is the Coalbed Methane Outreach Program’s (CMOP) role in promoting international coal mine methane (CMM) projects?
- How is methane emitted from coal mines?
- How much methane is emitted from coal mines?
- What are the uses for coal mine methane (CMM)?
- How much methane is captured and recovered from coal mines? Where are the projects?
- Where are the best opportunities for developing coal mine methane (CMM) projects in the United States?
- What is ventilation air methane (VAM) and how can it be used?
- What is abandoned mine methane (AMM)?
- How do I find out about international activities in CMM project development?
- How do I keep in touch with the Coalbed Methane Outreach Program (CMOP) and learn about new developments?
- What is global climate change and why should we be concerned about it?
1. Why is EPA concerned about coal mine methane (CMM)?
Methane (CH4) is the second most important greenhouse gas (GHG) after carbon dioxide (CO2). In fact, methane is more than 25 times more potent than CO2 on a mass basis over a 100-year time period. Coal mine methane (CMM) represents wasted emissions to the atmosphere, while capture and use of CMM has benefits for the local and global environment. More information about methane »
2. What is the difference between coalbed methane (CBM) and coal mine methane (CMM)?
CBM refers to methane that is found in coal seams. It is formed during the process of coalification, the transformation of plant material into coal. CBM is also known as virgin coal seam methane or coal seam gas. It is widely considered an "unconventional" source of natural gas. In the United States, CBM is a valuable resource that accounts for about 5 percent of total U.S. natural gas production annually. More information on CBM production in the U.S. » Exit
CMM refers to methane released from the coal and surrounding rock strata due to mining activities. In underground mines, it can create an explosive hazard to coal miners, so it is removed through ventilation systems. In abandoned mines and surface mines, methane might also escape to the atmosphere through natural fissures or other diffuse sources. Like CBM, CMM is a subset of the methane found in coal seams, but it refers specifically to the methane found within mining areas (e.g., within a mining plan), while CBM refers to methane in coal seams that will never be mined. Because CMM would be released through mining activities, recovering and using CMM is considered emissions avoidance.
3. How does the Coalbed Methane Outreach Program (CMOP) work to reduce methane emissions?
CMOP is engaged in numerous domestic and international outreach efforts. In the United States, CMOP works cooperatively with the coal mining industry to support project development, overcome institutional, technical, regulatory, and financial barriers to implementation, and communicate the benefits of CMM recovery.
Specific activities include:
- Identifying, evaluating, and promoting methane reduction options, including technological innovations and markets mechanisms to encourage project implementation.
- Conducting workshops to educate the mining industry and the broader community on the environmental, mine safety, and economic benefits of methane recovery.
- Preparing and disseminating reports and other materials that address topics ranging from technical and economic analyses to overviews of legal issues.
- Interfacing with all facets of the mining industry to advance project development.
- Conducting feasibility and pre-feasibility studies for U.S. mines that examine a range of end-use options.
- Providing global access to information regarding latest developments through our website.
4. What is the Coalbed Methane Outreach Program’s (CMOP) role in promoting international coal mine methane (CMM) projects?
CMOP continues to develop partnerships and engage in international outreach to promote CMM recovery and reduce CMM emissions globally in support of the Global Methane Initiative (GMI) Exit. CMOP supports CMM information clearinghouses and other collaborative efforts in several countries, including China, India, Kazakhstan, Mongolia, Poland, the Russian Federation, Turkey, and Ukraine.
5. How is methane emitted from coal mines?
There are three primary sources of CMM:
- Degasification systems at active underground mines. Also commonly referred to as drainage systems, these systems employ vertical and/or horizontal wells to recover methane before mining takes place to help the ventilation system keep the in-mine methane concentrations sufficiently low (well below the explosive limit) to protect miners.
- Ventilation air methane (VAM). This refers to the very dilute methane that is released from underground mine ventilation shafts. Although it is typically less than 1 percent methane, it is the single largest source of CMM emissions globally.
- Abandoned mine methane (AMM). Closed mines produce emissions of low- to medium-quality gas from diffuse vents, ventilation pipes, boreholes, or fissures in the ground.
Other, more minor sources of methane from coal mines include surface mines and post-mining activities (coal continues to emit methane as it is stored in piles and transported).
6. How much methane is emitted from coal mines?
U.S. coal mines emitted nearly four billion cubic meters or 61 million metric tons of carbon dioxide equivalent (MMTC02E) in 2015. Between 1990 and 2015, U.S. emissions decreased by 40 percent, in large part due to the coal mining industry's increased recovery and utilization of drained gas and decrease in ventilation air methane emissions.
By 2020, global methane emissions from coal mines are estimated to reach nearly 800 MMTCO2E, accounting for 9 percent of total global methane emissions. China leads the world in estimated coal mine methane (CMM) emissions with more than 420 MMTCO2E in 2020 (more than 27 billion cubic meters annually). Other leading global emitters are the United States, Russia, Australia, Ukraine, Kazakhstan, and India.
More information about international CMM emissions (PDF) » (33 pp, 4.8 MB) Exit
7. What are the uses for coal mine methane (CMM)?
Technology is readily available to recover methane — the major component of natural gas — from coal mines. Specific CMM end-uses depend on the gas quality, especially the concentration of methane and the presence of other contaminants. Worldwide, CMM is most often used for power generation, district heating, boiler fuel, or town gas, or it is sold to natural gas pipeline systems. CMM can also be used in many other ways:
- Coal drying
- Heat source for mine ventilation air
- Supplemental fuel for mine boilers
- Vehicle fuel as compressed or liquefied natural gas (LNG)
- Manufacturing feedstock
- Fuel source for fuel cells
8. How much methane is captured and recovered from coal mines? Where are the projects?
In 2015, U.S. coal mines recovered and utilized more than 33 billion cubic feet of coal mine methane (CMM). Nearly all of this gas was sold to natural gas pipelines.
Globally, as of 2015, there are more than 200 operating recovery and utilization projects in about 15 countries at active or abandoned coal mines and approximately 30 more projects in development. Collectively, these projects will mitigate nearly four billion cubic meters of methane each year (more than 60 million metric tons of carbon dioxide equivalent).
9. Where are the best opportunities for developing coal mine methane (CMM) projects in the United States?
CMOP has profiled 50 active underground coal mines in the United States with significant gas levels that might make them promising candidates for project development. As of 2015, about 26 of these mines have degasification (drainage) systems in place, and 16 mines have recovery and use projects. More about CMM recovery projects in the United States »
10. What is ventilation air methane (VAM) and how can it be used?
Methane is an explosive gas that is a hazard to underground miners. To ensure mine safety, fresh air is circulated through underground coal mines using ventilation systems to dilute in-mine concentrations of methane to levels well below explosive levels. These concentrations are regulated by mine safety authorities in each country. Typically, methane concentrations in ventilation air range from 0.1 percent to 1.0 percent.
Ventilation air methane (also known as VAM) refers to the very dilute methane that is released from underground mine ventilation shafts. VAM represents more than half of all coal mining emissions in the United States and worldwide. With few exceptions, it is simply released to the atmosphere. The high volumetric flowrate and low concentrations of VAM (i.e., less than 1 percent) make it challenging to capture and utilize cost-effectively. It is technically possible, however, to convert the dilute methane in ventilation air to useful energy and the economic feasibility of these projects are currently being developed, demonstrated, and commercialized.
11. What is abandoned mine methane (AMM)?
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 significant methane emissions from diffuse vents, fissures, or boreholes. This methane can be deliberately extracted and used to generate power or for other end uses.
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 successful projects at abandoned mines and mines that might be good candidates for project development.
EPA developed a methodology to estimate fugitive methane emissions from abandoned mines. This methodology is now incorporated in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories Exit.
12. How do I find out about international activities in coal mine methane project development?
The Coalbed Methane Outreach Program (CMOP) is actively engaged in implementing the international Global Methane Initiative (GMI) Exit, a voluntary initiative to reduce methane emissions from five key sectors: agriculture, coal mining, municipal solid waste (e.g., landfills), oil & gas systems, and wastewater. The Partnership focuses on near-term methane abatement or recovery for use as a clean, profitable energy source.
13. How do I keep in touch with the Coalbed Methane Outreach Program (CMOP) and learn about new developments?
Sign up as an Industry Contact! As an Industry Contact, you'll receive periodic updates or announcements via e-mail. If you choose, you can also be listed as a contact on our Industry Contact list.
14. What is global climate change and why should we be concerned about it?
For more information, please visit EPA's Climate Change website.