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Methane (CH4) is a potent greenhouse gas. Methane in the atmosphere is eventually oxidized, producing carbon dioxide and water. This breakdown accounts for the decline in the "global warming potential" of methane over longer periods of time.[1]

The 2007 Intergovernmental Panel on Climate Change (IPCC) report estimated the global warming potential of methane to be 25 times that of carbon dioxide over 100 years, and 72 times averaged over 20 years.[1]

The 2013 IPCC report increased the GWP of methane to 28 over 100 years and 84 over 20 years. If carbon feedbacks from methane emissions are taken into account, then the GWP for methane increases to 34 over 100 years and 86 over 20 years (Chapter 8, Table 8.7 on page 8-58).

Methane is both a greenhouse gas and a contributor to background levels of ozone. Tropospheric ozone is a significant greenhouse gas and the primary constituent of photochemical smog.[2]

Methane and climate change

Global levels

Global methane levels stabilised in the early 2000s, and scientists suspected this was due to better management of wetland rice crops (which produce methane from anaerobic decomposition), and better management of fugitive emissions from mining coal and other fossil fuels. However, after 2006 methane emissions began to rise again, and scientists believe this is due to an increase in global coal mining and fossil fuel production from shale rock.[3]


In September 2008, The Independent newspaper reported how preliminary scientific findings suggested that massive deposits of sub-sea methane were bubbling to the surface as the Arctic region becomes warmer and its ice retreats. This methane time-bomb is seen as extremely worrying, because it could be a positive feedback mechanism, where the more the Arctic melts the more methane is released, which could put us on the path to runaway global warming.[4]

The IPCC estimates that up to 80 percent of the Arctic permafrost could melt this century. Yet the threat of permafrost [methane] feedback was not included in the climate models of the 2013 IPCC report, as the first estimates of it came out in 2011 - too late by IPCC standards for inclusion in the report and its climate projections.[5]

U.S. regulations

The global warming potential of methane was estimated at 21 times that of carbon dioxide averaged over 100 years in the IPCC Second Assessment Report (1995), and the 21 figure is currently used for regulatory purposes in the U.S.,[6] although in 2013 the EPA proposed increasing the number to 25, in line with the 2007 IPCC estimate.[7]

Methane and coal

Methane released by coal mining

Coal mining accounts for about 10 percent of US releases of methane.[8] It is the fourth largest source of methane, following landfills, natural gas systems, and enteric fermentation.[8]

Methane released by coal mining includes:[9]

  • 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 emissions from coal mines has not been regulated by the Environmental Protection Agency. Earthjustice and other groups asked the EPA in 2010 to mandate cuts in methane emissions from coal mines. The EPA said in May 2013 that mandatory U.S. budget cuts did not leave it with the resources to determine if the pollution is a significant risk, and that the coal mines category represents only about 1 percent of total greenhouse gas emissions, according to EPA data.[10]

Coalbed methane

Coalbed methane (CBM), also known as coal seam gas (abbreviated "CSG"), is a type of natural gas extracted from coal beds. It is formed by the geological process of heating and compressing plant matter to create coal. Over millions of years, methane forms within the coal. The methane is trapped by water in the gaps and cracks between the coal molecules. These gaps are known as cleats. Australia has been found to have many deposits, and is increasingly mining them through hydraulic fracturing, also known as fracking. In recent decades, CBM has become an increasingly used source of energy in Australia, as well as the United States, Canada, and other countries.[11]

Methane and coal mining explosions

When coal is mined, fissures and pores in the coal bed in which methane is lying are exposed, releasing methane into the confined area. This can be dangerous because methane is not only highly flammable, with the potential to violently explode in a ball of flame, but is also an asphyxiant, capable of driving out oxygen and causing death by suffocation. A build up of hazardous gas in a mine is known as a damp, with methane build-ups called “fire damps”. Carbon monoxide accumulation, called “white damp,” adds to these dangers. When methane combusts, this highly toxic and flammable gas is generated as a by-product and spreads through a mine’s tunnels and shafts. Coal dust also reacts badly to a methane explosion. As part of a violent chain reaction, it can burst into flames in a series of secondary explosions throughout a mine.[12]

The properties of methane make it difficult to detect without equipment. It is colorless and odorless, so there are no obvious physical signs such as coughing or watering eyes to warn of its proximity, although it will cause suffocation if it builds up in a badly ventilated space. It is also difficult to assess how much methane is likely to be freed from a particular coal bed – factors such as coal type, the depth of the mine, and the geologic age of the coal strata all play a part.[12]

Once present in the atmosphere of the mine, methane can be easily ignited. Modern mining equipment includes electric arcs, hammers, and cutters that can all generate sparks and open flames that can detonate a pocket of methane gas. U.S. federal standards stipulate that if there is 1.0 percent or more of methane in the working area, miners must immediately shut down all electrically powered tools and other mechanized equipment.[12]

The 1907 Monongah Mine Disaster of West Virginia, which claimed the lives of 362 men and boys and is known as the worst mining disaster in American History,[13][14] is thought to have been caused by the ignition of methane, which in turn ignited highly flammable coal dust.[15]

Methane and the Upper Big Branch Mine Disaster

In July 2010, an electrician at the Upper Big Branch Mine, site of the Upper Big Branch Mine Disaster in April 2010, confirmed that he was ordered to bypass the methane detector on a piece of mining equipment. Such detectors are designed to automatically turn off a machine once methane reaches a certain level; with the detector bypassed, the machine would continue operating regardless of methane levels. The detector was on a continuous mining machine four miles from the origins of the explosion and was not thought to have played a role in the explosion. Investigators, however, are now looking to see if the practice of bypassing the detectors had happened in other areas of the mine, something that could point to wider questions about safety practices at the mine. Micah Ragland, spokesman for Massey Energy, confirmed that someone had bridged the methane monitor.[16]

Federal investigators first learned of the monitor bridging from Ricky Lee Campbell, a former Upper Big Branch miner who was fired from his job at another Massey mine after he publicly criticized safety practices at Upper Big Branch. Massey lawyers said Mr. Campbell was fired for violating a safety rule at the company's Marfork Coal Co., but in June 2010, Department of Labor officials won temporary reinstatement of Mr. Campbell after an administrative law judge ruled that he had actually been fired in retaliation for speaking out. According to Campbell, he and two other miners at Upper Big Branch saw a supervisor instruct Mr. Holtzapfel to run a wire that would bypass a methane detector on a continuous mining machine on Feb. 13 -- seven weeks before the blast. Campbell said Holtzapfel had protested the order, calling it improper, but was forced to make the bridge. When told of Mr. Campbell's account, Mr. Holtzapfel said, "That's how it went."[16]

Methane and gas production

Methane leakage from oil/gas wells

Various studies by academics, government, and industry have found that methane leakage can range from less than 1 percent to as much as 8 percent of the natural gas produced each year. The difference is attributed to the small amount of raw data available and variations in the way the data are interpreted.[17]

Using the small data available from the oil/gas industry so far, EPA has estimated that 2.8 percent of gas produced from a well each year leaks. Oil/gas companies and Devon Energy, in particular, have criticized EPA for relying on what they say is a small, outdated sample with data gaps.[17]

A 2011 study out of Cornell University found leakage of 2.2 to 3.9 percent of produced gas per well, and up to 8 percent.[17]

A 2012 NOAA study to be published in the Journal of Geophysical Research is considered the most authoritative because scientists based it on actual measurements of leakage at Colorado gas fields in 2008. That study found that about 4 percent of the 202 billion cubic feet of gas produced that year may have leaked in the Denver-Julesburg Basin. NOAA's assumptions have been challenged, most prominently by Michael Levi, director of the Program on Energy Security and Climate Change at the Council on Foreign Relations, who reworked the raw data of the NOAA study without the same assumptions, Levi has found leakage of 1.3 to 2.3 percent.[17]

In October 2012 the University of Texas, Austin, the Environmental Defense Fund, and nine major natural gas companies said that, in January 2013, the group will begin publishing raw data, collected at their drilling sites, and offer them for peer review.[17]

In September 2012 researchers at the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado in Boulder reported preliminary results from a field study in the Uinta Basin of Utah suggesting methane leakage of up to 9% of total gas production, nearly double the cumulative loss rates estimated from industry data. The NOAA researchers collected their data in February 2012 as part of a broader analysis of air pollution in the Uinta Basin, using ground-based equipment and an aircraft to make detailed measurements of various pollutants, including methane concentrations.[18]

A 2016 Harvard study published in the Journal Geophysical Research Letters shows a 30% rise in methane admissions since 2002. The study hypothesizes that the U.S. could have caused the approximately 30-60% of the global growth in human-caused atmospheric methane emissions since 2002 because of a 30% increase in methane emissions across the U.S. The study does not pinpoint the source of the methane emissions but the 30% spike of U.S. methane emissions in 2002 coincides with the shale boom.[19]

Cornell professor Robert Howarth, who did earlier ground breaking research on methane emissions, told Climate Central that he was almost certain that the increase in methane was due to fracking and increased natural gas usage.

The Harvard researchers calculated emissions measurements with satellites rather than using leak estimates of oil and gas wells. This could account for why the Harvard methane estimates are higher than those figures produced by EPA based on leak estimates.[20]

Gas flaring

Global gas flaring crept up by 4.5 percent to around 140 billion cubic meters (bcm) in 2011, up from 134 bcm the previous year, and the first rise since 2008, preliminary data from the World Bank shows. Flaring of the gas (methane) is used to eliminate gas at mineral exploration sites, and is released via pressure relief valves to ease the strain on equipment. The increase is mostly due to the rise in shale oil exploration in North Dakota. Globally, flaring amounts to around 4.5 percent of global industrial emissions.[21]

In addition to methane, gas- and oil-suffused bedrock contains many toxic hydrocarbons, some of them volatile gases. As soon as a hole is drilled into the formations, the fugitive native gases can escape, including benzene.[22]

Urban Methane leakage

Boston, Massachusetts area infrastructure loses two to three times more gas than state authorities say, adding to evidence of downstream operations' (including pipelines, storage terminals and power plants) role in greenhouse emissions according to a study published in January 2015 Proceedings of the National Academy of Sciences.[23] This is the first peer reviewed study that quantifies emissions of methane, a gas is roughly 86 times as potent as carbon dioxide as a driver of climate change over a period of 20 years, from natural gas operations in urban centers.[24] Many previous studies focused on methane leaks from the drilling and hydraulic fracturing wells. Less attention was given to natural gas storage and pipelines that deliver gas to homes.

The university researchers estimate the amount of Boston area methane lost over a year in the study area to be worth $90 million.[25]

Biogenic methane production

Companies are looking into stimulating methane production for energy use. As of May 2010, Luca Technologies is working on a large scale pilot program in an old natural gas field west of Gillette, Wyoming, on a process called “biogenic methane production.” The process involves gravity feeding water and what the company calls “nutrients” down old methane wells to stimulate the native microbes in the coal seams to multiply and produce methane at an accelerated rate. Many believe it took millions of years for the microbes to make the methane now being extracted in the basin. Luca researchers think that with a little help, the microbes can make enough to extract methane at a profit in only a few years.[26]

In 2001, Luca started work on the idea of biogenic methane production in its lab in Golden, Colorado. After years of study, the company began an initial pilot program near Sheridan with 100 wells in 2006. In 2008, the company bought 529 old wells west of Gillette from Kennedy Oil and added them to the roster. Luca bought another 725 former Devon Energy wells in the same area. With more than 1,350 wells, Luca believes it can grow methane on a commercial scale in the Powder River Basin.[26]



  1. 1.0 1.1 Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)"Climate Change 2007: Working Group I: The Physical Science Basis: 2.10.2 Direct Global Warming Potentials", IPCC Fourth Assessment Report: Climate Change 2007, Cambridge University Press, 2007.
  2. "Linking climate and air pollution: Methane emission controls yield a double dividend" NOAA, accessed November 2010.
  3. Anna Salleh, "Rising methane 'due to mining and wetlands,'" ABC, September 23, 2013.
  4. Steve Connor, "Exclusive: The methane time bomb", The Independent, September 23, 2008
  5. Fred Pearce, "Has the U.N. Climate Panel Now Outlived Its Usefulness?" Yale 360, Sep 30, 2013.
  6. "Methane," U.S. Environmental Protection Agency information page, accessed July 2010
  7. Jason Mark, "Methane’s Contribution to Global Warming is Worse than You Thought," Earth Island Journal, August 20, 2012.
  8. 8.0 8.1 U.S. Environmental Protection Agency ,"Methane: sources and emissions," U.S. Environmental Protection Agency website, October 20th, 2006.
  9. "Coal Mine Methane Recovery," Power Partners Resource Guide, accessed May 2008
  10. Mark Drajem, "Coal Mines’ Methane Curbs Fall Victim to EPA Budget Cuts," Bloomberg, May 7, 2013.
  11. Jargon Buster. BG Group. Retrieved on 18 July 2010.
  12. 12.0 12.1 12.2 "Coal Mining and The Risk Of Methane Gas Explosions", accessed September 2010.
  13. Historical Data on Mine Disasters in the United States, U.S. Department of Labor website, accessed November 2009.
  14. Coal Mining Disasters, National Institute for Occupational Safety and Health, accessed November 2009.
  15. "Monongah Mining Disaster" Boise State Website, accessed November 2009
  16. 16.0 16.1 Dennis B. Roddy and Daniel Malloy, "Detector bypassed before W.Va. coal disaster" Pittsburgh Post-Gazette, July 15, 2010.
  17. 17.0 17.1 17.2 17.3 17.4 Gayathri Vaidyanathan and Saqib Rahim, "Data-heavy project aims to move methane emissions research beyond 'he said, she said,'"] E&E, October 15, 2012.
  18. Jeff Tollefson, "Methane leaks erode green credentials of natural gas," Nature 493, 12, January 2, 2013.
  19. Bobby Magill, "US 'likely culprit' of global spike in methane emissions over last decade," The Guardian, February 17, 2017.
  20. Bobby Magill, "US 'likely culprit' of global spike in methane emissions over last decade," The Guardian, February 17, 2017.
  21. Henning Gloystein and Alessandra Prentice, "Exclusive: Shale causes rise in waste gas pollution," Reuters, May 2, 2012.
  22. Sandra Steingraber, "Safe Hydrofracking Is the New Jumbo Shrimp," HuffPo, June 4, 2012.
  23. "Methane Leaks From Gas Pipelines Far Exceed Official Estimates, Harvard Study Finds" Lisa Song, Inside Climate News, January 28, 2015.
  24. Bobby Magill, "US 'likely culprit' of global spike in methane emissions over last decade," The Guardian, February 17, 2017.
  25. "Methane Leaks From Gas Pipelines Far Exceed Official Estimates, Harvard Study Finds" Lisa Song, Inside Climate News, January 28, 2015.
  26. 26.0 26.1 Steve McManamen, "Luca says natural gas industry is alive and well ... literally", May 17, 2010.

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