It’s no wonder Congress is having trouble reducing the nation’s carbon emissions. One of its most intractable holdouts is the Capitol Power Plant, just two miles from the White House and now the single largest source of carbon emissions in the District of Columbia.

According to an account in The New York Times, the plant provides heating and cooling to 23 buildings in the Capitol complex, including the Library of Congress, the Supreme Court and the Capitol itself.

But despite efforts that date back more than a dozen years, the plant’s fuel mix still includes some coal, as well as diesel fuel, and efforts to convert the plant to burn only natural gas appear to be going nowhere.

No one wants to talk about the plant

Neither the District of Columbia’s Department of the Environment nor the Environmental Protection Agency has forced the plant to meet air emissions laws, The Times said. Congress itself is responsible for the plant, but ranking members of House and Senate committees that oversee wouldn’t talk to the newspaper. Nor would the office of the architect of the Capitol, which oversees the plant’s operation.

The Democrats who first launched efforts to end the use of coal at the plant in 2000 blame Republicans for stalling the efforts. Drew Hammill, a spokesman for former House Speaker Nancy Pelosi, told The Times, “We worked to figure out a way to get around the issue of coal. But it is a futile effort until you get rid of the Republican majority. They do not believe in the word ‘green.'”

According to an article posted at Climate Progress, the 1910 plant has seven boilers that can burn three types of fuel: coal, natural gas and oil.

The proportion of coal has declined from 56% of the plant’s fuel mix in 2007 to just 5% in 2011, Climate Progress reported, and it’s used mostly as an emergency backup fuel source. But as the amount of coal declined, the difference was made up mostly by diesel fuel oil, also a dirty fuel.

The Architect’s office has permits that would allow the plant to operate exclusively on natural gas, and to begin providing electricity to the Capitol complex as well. But Congress has allocated no money for the project, estimated in 2008 to cost between $6 million and $7 million.