WASHINGTON Feb 5 (Reuters) - Greenhouse gas emissions from U.S. power plants fell 4.6 percent in 2011 as more generators were switched to cleaner-burning natural gas and renewable sources from coal, according to new data from the Environmental Protection Agency.
The agency's second inventory of greenhouse gas emissions reported by the country's largest industrial polluters showed that power plants - which account for one-third of U.S. emissions - released 2.22 billion metric tons of carbon dioxide equivalent (CO2e) in 2011.
Despite the decline in power plant emissions, coal-fired power plants continue to be the largest single source of carbon emissions in the United States, the data showed.
The congressionally mandated EPA database covers 8,000 industrial sources that together emit more than 25,000 tonnes of CO2e per year - large enough to be subject to some of the rules being proposed by the EPA to curb greenhouse gas emissions.
This year, the database was expanded to include data on methane emissions, which are generally produced by large emitters in the oil and gas sector.
Oil and natural gas systems emitted 225 million tonnes of CO2e in 2011, making them the second largest greenhouse gas source.
Environmental group The Environmental Defense Fund said in a statement that the addition of methane to the EPA database will be valuable as lawmakers and regulators consider how to regulate emissions from the boom in U.S. natural gas production.
"Today's new data will provide insights into methane emissions industrywide, which can help policymakers as well as oil and gas operators identify cost-effective opportunities to reduce pollution and prevent the waste of a valuable domestic energy source," said Peter Zalal of EDF's Climate and Air legal team.
The EPA also showed that refineries increased their greenhouse gas emissions by 0.5 percent in 2011 from 2010, making them the third largest source of domestic greenhouse gases. (Reporting by Valerie Volcovici; editing by Jim Marshall)