"Research on climate change has identified a wide array of sources that emit greenhouse gases (GHGs). Among the six gases that have generally been the primary focus of concern, methane is the second-most abundant, accounting for approximately 8% of total U.S. GHG emissions in 2008. Methane is emitted from a number of sources. The most significant are agriculture (both animal digestive systems and manure management); landfills; oil and gas production, refining, and distribution; and coal mining. […] This report discusses alternatives for addressing methane capture, sources of methane, opportunities and challenges for methane capture, and current federal programs that support methane recovery."
CRS Report for Congress, R40813
United States. Department of State, Foreign Press Centers, Bureau of Public Affairs: http://www.fpc.state.gov/