A record 1.77 billion gallons of the corn-based fuel was distilled last year. Ethanol arose in the 1970s as a home-grown response to fuel embargoes of the 1970s and an outlet for surplus crops. In recent years, it has been used to raise the octane level of motor fuels and produce cleaner-burning fuels.

Foes - including California and New York senators - object that ethanol is too costly to compete with petroleum without the benefit of federal subsidies and is an overall energy drain. A Cornell University researcher last year calculated a loss of 33,562 British thermal units for every gallon of ethanol produced.

In a new study, published last week by the U.S. Agriculture Department, researchers found a net energy gain of 21,105 BTU per gallon. A BTU is the amount of energy needed to raise the temperature of a pound of water by one degree F. A gallon of gasoline contains 125,070 BTU.

Monte Shaw, of the Renewable Fuels Association, a pro-ethanol trade group, said the report "could have an impact" on the energy bill by rebutting the 2001 study by David Pimentel of Cornell University, which showed an energy loss of 33,562 BTU. "It just helps ... to have something that's more current and up-to-date," Shaw said. Attempts to reach Pimentel for comment by telephone and via e-mail were unsuccessful.

ETHANOL FIGURES IN ENERGY BILL

Negotiations to write a broad energy bill promoting domestic oil and gas production and conservation measures are scheduled to resume in early September, following the congressional vacation this month. One of the most contentious issues in the bill is the proposal to triple the use of ethanol as a gasoline additive.

Supporters include President George W. Bush, Senate Majority Leader Tom Daschle and most farm state lawmakers.

But the ethanol mandate is opposed by Democratic Sens. Dianne Feinstein and Barbara Boxer of California and Charles Schumer and Hillary Clinton of New York. They fear gasoline prices would rise because ethanol is difficult and costly to transport to coastal locations and because agribusiness giant Archer Daniels Midland Co. controls some 41 percent of U.S. ethanol production.

The authors of the new report, Hosein Shapouri and James Duffield of the USDA and Michael Wang of Argonne National Laboratory, pointed to five other studies since 1995 that concluded ethanol provides a net energy gain, thanks to more efficient farming and processing. The energy advantage was likely to grow in the future, they said.

"Corn ethanol is energy efficient... For every BTU dedicated to producing ethanol there is a 34 percent energy gain," the study said.

"Only about 17 percent of the energy used to produce ethanol comes from liquid fuels, such as gasoline and diesel fuel. For every 1 BTU of liquid fuel used to produce ethanol, there is a 6.34 BTU gain," the researchers added.

Bob Dineen, president of the Renewable Fuels Association, said the new study shows that ethanol "clearly helps reduce our dependence on foreign oil." "I think that (6.34 BTU) is a number you're going to hear a lot about in the next couple of months," Shaw said in an interview.

In calculating the "energy balance" of ethanol, researchers looked at energy use, including so-called farm inputs such as fuel, fertilizer and pesticides, energy used in converting grain into ethanol and fuel used for transportation, compared with the BTU value of ethanol and co-products from corn milling.

The new study allocated 19 percent of the 77,228 BTU used in producing ethanol to byproducts such as corn gluten and corn oil. The Cornell study last year estimated nearly 132,000 BTU were needed to produce a gallon of ethanol.