Methane released by coal mining

Coal mining accounts for about 10 percent of US releases of methane (CH4), a potent global warming gas. It is the fourth largest source of methane, following landfills, natural gas systems, and enteric fermentation.

Coal mining releases methane in four ways:
 * Underground Mining: In the United States, methane from underground mining operations is typically vented. In some other countries it is also flared.
 * Surface Mining: During surface mining, methane is released directly to the atmosphere.
 * Post-Mining Activities: Some methane remains in the coal after mining and is released during subsequent processing and transportation.
 * Abandoned Mines: Methane emissions from abandoned mines are not quantified and included in U.S. inventory estimates, but may be significant.

Methane plays a significant role in the dynamics of global warming due to the following factors:


 * Methane is a relatively potent greenhouse gas with a high global warming potential of 72 (averaged over 20 years) or 25 (averaged over 100 years). Methane in the atmosphere is eventually oxidized, producing carbon dioxide and water. As a result, methane in the atmosphere has a half life of seven years (if no methane was added, then every seven years, the amount of methane would halve).


 * CH4 concentrations have more than doubled over the last 150 years.


 * According to calculations reported in 2005, methane emissions may account for a third of the climate warming from greenhouse gases between the 1750s and the present, twice the level of previous estimates.


 * An average molecule of CH4 lasts around eight to nine years before it gets oxidized into carbon dioxide (CO2) and water (H2.

Amount of methane released by coal mining
A study by the National Renewable Energy Laboratory estimated that surface mining releases 1.91 grams of methane per kilogram of surface mined coal. The same study estimated that mining releases 4.23 grams of methane per kilogram of underground-mined coal.

Related SourceWatch articles

 * The methane time-bomb

External resources

 * "Coal Mine Methane Emission Offsets," Chicago Climate Exchange
 * "Comparison of Carbon Capture and Storage with Renewable Energy Technologies in the Year 2020 by Way of a Life Cycle and a Cost Assessment," Peter Viebahn et al (PDF file)
 * "Comparison of carbon capture and storage with renewable energy technologies regarding structural, economic, and ecological aspects in Germany" Peter Vieban et al, Int. J. Greenhouse Gas Control (2007)
 * "Methane: Sources and Emissions," U.S. Environmental Protection Agency
 * "Methane" (Wikipedia article)