The 10 Biggest Carbon Dioxide Polluters

For the first time, a look at the power companies with the most greenhouse gas emissions.

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Ten large companies generate more than one third of the 2.8 billion tons of carbon dioxide emitted each year by U.S. electric power generators, according to figures in a first-of-its-kind database unveiled Wednesday.

American Electric Power, based in Columbus, Ohio, and Southern Co. of Atlanta, which run the largest coal power plants in the country, top the list of U.S. companies responsible for greenhouse gas emissions from electricity, according to data compiled by the Center for Global Development, a global economic development think tank in Washington, D.C.

The database, called CARMA or Carbon Monitoring for Action, culls for the first time data both from government regulators around the world and commercial databases to provide an up-to-date look at the state of CO2 from power production—which accounts for one quarter of all carbon emissions. (The database doesn't look at other large sources, like transportation and manufacturing.) Here are the top sources of greenhouse gas emissions from electricity generation in the United States:

The 10 Biggest Carbon Dioxide Polluters

1. American Electric Power 174 million
With 5 million customers in 11 states from Ohio to Texas, its biggest carbon emissions come from its Gavin coal plant in Cheshire, Ohio.
2. SOUTHERN 172 million
Has 4.3 million customers in the Southeast and owns the top three carbon-emitting power plants in the country: Scherer, in Juliet, Ga.; Miller in Quinton, Ala.; and Bowen in Cartersville, Ga.
3. (tie) AES CORP. 108 million
Has power plants from New York to California, with the worst emissions from its Petersburg, Ind., plant.
3. (tie) DUKE ENERGY 108 million
Serves 4 million customers in the Carolinas, Ohio, Kentucky, and Indiana. Its Gibson plant in Owensville, Ind., is the nation's fourth-largest carbon emissions source in the power sector.
The nation's largest public power company serves the 8.7 million residents of the Tennessee Valley. Its Cumberland City, Tenn., plant ranks eighth in the nation in CO2 emissions.
6. NRG ENERGY 82.7 million
A wholesale power producer that operates in deregulated electricity markets throughout the country, its W.A. Parish plant in Thompsons, Texas, is the nation's No. 5 carbon emissions source.
7. XCEL ENERGY 76.1 million
With 3.3 million customers in the West and Midwest, its largest carbon generator is its Sherburne County plant in Becker, Minn.
A Warren Buffett Berkshire Hathaway company, MidAmerican serves customers in Iowa, Illinois, and South Dakota, with its largest CO2 emissions from the Jim Bridger plant in Point Of Rocks, Wyo.
9. PROGRESS ENERGY 68.1 million
Based in Raleigh, N.C., its plant in Roxoboro, N.C., is its biggest emissions source.
10. DOMINION RESOURCES 66.6 million
Dominion is based in Virginia, with operations stretching into the Northeast and Midwest. Its biggest carbon emissions source is its Mount Storm, W.Va., plant.

Strikingly, three Chinese power companies, South Africa's giant Eskom, and India's NTPC all generate more CO2 emissions than any single U.S. firm—underscoring the shared challenge posed by global climate change. The largest, Huaneng Power International of China, has emissions 68 percent higher than American Electric Power's.

The CARMA website, which will be updated quarterly, also allows any visitor to search the data from 4,000 electric power companies worldwide to find the largest carbon emitters, not only by company or individual power plant but also by city, state, county, congressional district, or country.

Individual power plants are plotted by latitude and longitude and linked to Google Maps, so a user can zero in to see the plant up close. Focusing on the map of Southern Co.'s massive Scherer plant north of Macon, Ga., the No. 1 U.S. power plant in CO2 emissions, it's possible to see the tracks where trains travel continuously to unload the 1,288 tons of coal Scherer burns per hour.

One of the most striking findings in the data, says David Wheeler, a Center for Global Development senior fellow who led the research, is how concentrated the problem is among a relatively few large power generators. He said the top 100 companies worldwide produce 57 percent of CO2 emissions coming from the power sector. The top 30 companies produce 30 percent of the total. "On the one hand, it's sobering," he says. "But it might be hopeful. You could actually assemble the CEOs of those firms, and there might be many channels through which they can organize and address this as a group themselves. I think that'll be critical to a solution."

Wheeler was a former lead economist in the World Bank's Development Research Group, where his team used public disclosure as a strategy to generate pressure from lenders and communities for pollution reduction in China, Indonesia, and the Philippines. Wheeler says his team similarly hopes the CARMA data will be used not only by environmental groups but by institutional and private investors and insurers, to encourage power companies to use less coal and oil and shift to renewable resources.

Although companies topping the list of carbon dioxide emitters are all among the country's largest power generators, more megawatts doesn't necessarily mean more CO2. Southern actually produces about 25 percent more power than AEP, but it has lower carbon emissions because 20 percent of its generation comes from nuclear plants, while close to 90 percent of AEP's power portfolio is fossil fuel. Also, Exelon is well out of the top tier of carbon emitters even though its operations in southeastern Pennsylvania and northern Illinois generate nearly as much power as the nation's No. 5 carbon emitter, the federally owned Tennessee Valley Authority. With the largest nuclear power fleet in the country, nearly 95 percent of Exelon's generation is carbon-emissions free.

The CARMA database color-codes the power generators from red to green, depending on how much of their mix is fossil fuel. AEP's color code is red, Southern's is orange, and Exelon's is green (although Wheeler says the group is making no value judgment on nuclear power).

Despite its high ranking, American Electric Power is viewed by many as a leader in the climate debate. The company was a founding member of the voluntary, legally binding Chicago Climate Exchange, through which it has committed to reduce greenhouse gas emissions 6 percent below its 1998 to 2001 average by 2010. In the short term, it is focusing on energy efficiency and adding renewable generation such as wind. But this spring it announced a project to install carbon capture technology on two of its big coal-fired plants, which would be the first commercial use of such technology in the world.

"We recognize that as a large coal-fired utility that our CO2 emissions are at or near the top of any list," says AEP spokesman Pat Hemlepp. "But we are also at or near the top of any list of companies taking action."