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WASHINGTON (AP) — Heat-trapping gases from U.S. power plants fell 4.6 percent in 2011 from the previous year as plants burned less coal, the biggest source of greenhouse gas pollution, according to a new government report.

The report, released Tuesday by the Environmental Protection Agency, said power plants remain the largest stationary source of carbon dioxide and other greenhouse gases that trigger global warming. Power plants were responsible for 2.2 billion metric tons of carbon dioxide equivalent in 2011.

The reduction from 2010 reflects a relative decline in the use of coal, the dominant U.S. energy source, and an increase in natural gas and renewable sources that produce lower amounts of greenhouse gases, the report said.

Power plants produced roughly two-thirds of greenhouse gas emissions from stationary sources, the EPA said, with petroleum and natural gas systems a distant second and refineries the third-largest carbon pollution source.

The annual report was the second produced by the EPA as it tracks global warming pollution by industry type and individual facility. The data include more than 8,000 facilities in nine industrial sectors that produced more than 3.3 billion tons of carbon dioxide equivalent.

The report shows that greenhouse gas pollution is concentrated at large power plants, petroleum refineries and chemical plants. Just 4 percent of the sites analyzed were responsible for 57 percent of the reported pollution in 2011.

For the second year in a row, the EPA's data shows that the largest greenhouse gas polluter in the nation in 2011 was the Scherer power plant in Juliette, Ga. The coal-fired plant, owned by Atlanta-based Southern Co., reported releasing more than 22 million metric tons of carbon dioxide, the chief greenhouse gas, in 2011.

Another Southern-owned plant was the second-largest polluter nationally: the James H. Miller, Jr. power plant in Quinton, Ala., which also produced 22 million metric tons of carbon dioxide equivalent.

Martin Lake power plant in Tatum, Texas, operated by Dallas-based Luminant, was third, with 18.4 million metric tons of carbon pollution, the report shows. Peter Zalzal, an attorney for the Environmental Defense Fund, called the EPA report "a call to action for America to work together" to find innovative solutions to address carbon pollution from power plants and methane from oil and gas production.

"We know where the largest sources are. We know where we have to apply smart solutions," he said.