Methane gas is a valuable energy resource and the leading anthropogenic contributor to global warming after carbon dioxide. By mass, methane has 21 times the global warming potential of carbon dioxide over a 100-year lifetime and accounts for 10 percent of U.S. greenhouse gas emissions (excluding sinks). Reducing methane emissions is key to reducing overall greenhouse gas emissions. The major anthropogenic sources of methane emissions in the U.S. are landfills, livestock enteric fermentation and manure management systems, natural gas and oil systems and coal mines. This Addendum presents EPAâ??s updated baseline forecast of methane emissions from the major sources in the U.S., and EPAâ??s cost estimates of reducing these emissions.
