The United States burns through 20.6 million barrels of oil a day — about 25 percent of the world demand of 85.6 million barrels a day, according to a Boston University professor who studies oil economics.

During a teleconference Tuesday for the Foundation for American Communications based in Pasadena, Calif., Robert Kaufmann said that high costs for petroleum and oil-shale production make seeking alternative energy sources more attractive. Kaufman is a professor at Boston's Center for Energy and Environmental Studies,

The United States produces 25 percent of the world's economic activity, but developing countries such as China and India are catching up in economic activity and demand for oil. The U.S. imports 60 percent of its oil and hasn't been oil independent since 1947.

"The U.S. imports oil because it's less expensive than trying to produce it at home," he said.

If the U.S. government and industry leaders are serious about tapping oil shale, research and development should be further along than they now are, he said.

"You'll need to go from producing zero oil shale to 10 million barrels of oil shale in about seven years," he said.

Oil shale is in abundance in the Green River Basin of Colorado, Utah and Wyoming. President Bush has asked Congress to lift restrictions on oil-shale leasing on federal lands. Shell Exploration & Production Co. is researching whether oil shale in western Colorado is commercially viable and can be extracted without polluting groundwater. The results of the research will not be known for at least two years.

Kaufmann said that building a nuclear power plant takes about a decade, and unlike oil shale, scientists and engineers know how to produce nuclear power. Meanwhile, at some point during peak production, the world's largest oil fields will run dry, and production will sharply decrease.

"We're going to need alternatives in a timely fashion, and if they're not available, it will (result) in tremendous economic disruption," Kaufmann said.

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