On Monday afternoon, as temperatures dipped into the 20s, thousands of energy activists crowded the Spirit of Justice Park armed with homemade signs, green hard hats and thick jackets.

They came to protest the Capitol Power Plant, a century-old facility that heats and cools the Capitol complex using a mixture of natural gas and coal. As the No. 1 polluter in Washington, D.C., it seemed like the perfect symbol of Congress’ failure to force a change in energy policy.

But last week — just days before the scheduled protest — Speaker Nancy Pelosi (D-Calif.) and Senate Majority Leader Harry Reid (D-Nev.) announced their intention to switch the plant entirely to natural gas.

So before protesters had even marched to the plant to block the entrances and disrupt its operations, organizers were hailing the effort as a victory.

“Do you guys think it’s a coincidence that three days ago they made the announcement about the plant?— Joshua Kahn Russell yelled to the bundled-up crowd. “That tells us we’re powerful.—

Within a couple of hours, though, the estimated 3,000 protesters had dwindled to a few dozen at each of the plant’s entrances. Capitol Police made no arrests.

Apart from a few protesters who yelled for solar power, many in the crowd seemed pleased with Congress’ decision.

“It’s a symbol,— said Paul Rogat Loeb, who has written several books on how activism can change energy policy. “It’s good to green the Capitol. Now you need to green the country.—

But Pelosi is still working to perfect that symbol of a green Capitol.

The Speaker and Reid’s plan to switch the century-old plant to 100 percent natural gas will cost about $7 million, according to past estimates from the Architect of the Capitol. And Pelosi’s plans to continue with the less difficult greenings — using recycled paper, environmentally friendly cafeterias, energy-efficient light bulbs — will continue to cost money and time in the 111th Congress.

As protesters sat at the power plant, House Chief Administrative Officer Dan Beard released a year-end report Monday on the progress made through the Speaker’s Green the Capitol Initiative.

In the 110th Congress, the House reduced its carbon footprint by 74 percent — but fell short of declaring “carbon neutrality,— the main tag line of the project.

All the original goals were met, according to CAO spokesman Jeff Ventura — including the purchase of about $90,000 worth of carbon offsets to make up for the plant’s emissions in 2007 and 2008.

But declaring carbon neutrality became a moving target, difficult to claim because no universally accepted definition exists, Ventura said.

It’s the “idea of running your project as it relates to that zero goal when that zero number is so ill-defined.—

Pelosi’s plan to get to carbon neutrality also become controversial — particularly the purchase of carbon offsets. Republicans ridiculed the offset purchase as a waste, while reports from the Congressional Research Service and the Government Accountability Office questioned the reliability of private cap-and-trade markets.

Now, the CAO is switching gears. Beard has no plans to buy any more offsets, and his next focus will be on reducing the House carbon footprint through sustainable business practices.

That includes “reducing the amount of physical hardware used in offices across the Capitol complex.—

In other words: getting rid of those individual servers in each House office and consolidating them in one place.

Beard’s staff will also aim to make their office a model of sustainability.

“There is immense opportunity inherent in this endeavor,— Beard’s year-end report reads. “Because CAO employees quite literally touch every corner of House operations, a fully sustainable CAO, in effect, brings us all-the-closer to a fully sustainable House of Representatives.—