The DOE said 89 billion barrels could potentially be added to current proved US oil reserves of 21.9 billion barrels through injection of carbon dioxide, the main gas that most scientists believe is warming the earth.

The DOE gave no time frame for when the extra barrels could be added.

The amount is about what the United States, at current demand, uses in 12 years.

Adding billions of barrels in reserves is dependent upon the availability of commercial CO2, the DOE's fossil energy office said.

"Next generation enhanced recovery with carbon dioxide was judged to be a 'game changer' in oil production, one capable of doubling recovery efficiency," DOE said in a release.

Up to 430 billion barrels could be added by pumping the gas into fields that have yet to be discovered, the DOE said.

COSTLY?

A United Nations report in September said that burying large amounts of carbon dioxide could play a big role in fighting global warming, but would be a costly fix.

Electricity prices could typically rise by 25 to 80 percent if power plant operators adopted the technology, according the the report by the UN's Intergovernmental Panel on Climate Change.

The United States is the No. 1 emitter of heat-trapping gases.

In 2001 President Bush pulled out of the Kyoto Protocol on global warming which requires developed nations to cut greenhouse emissions. Bush said the pact would harm the economy. He favors using technology and voluntary methods of cutting emissions.

Capturing the greenhouse gases is an emerging technology. Power producers, anticipating future mandatory caps on gases most scientists believe are warming the earth, have been considering adding the technologies to their plants.

But because of the expense, none have yet been used commercially.

In Australia earlier this year, six of the world's major polluters led by United States pushed clean energy technology as an alternative way to tackle global warming outside the Kyoto Protocol.

Carbon dioxide capture and sequestration underground was one of the technologies discussed by the group.

But many environmentalists say it would be virtually impossible to measure leaks of the gas especially from oil and gas fields in which holes have been drilled repetitively over decades.

"How do you make sure you're not putting it in one end and leaking it out many other ends?" said Kert Davies, a climate specialist at Greenpeace in Washington. "If it leaks even at 1 percent per year you've thought you've saved something, but in fact you didn't."

Advancements in carbon capturing could be made at power plant called FugureGen. An international consortium of utilities and coal companies will join with the US government to build FutureGen, billed as a "zero-emissions" coal-fired power plant.