The ethanol industry sharply rebuked a study by University of California, Berkeley freshmen concluding it takes more energy to produce ethanol than the amount of petroleum saved when the additive is combined with gasoline.

Despite criticism Friday by an ethanol industry spokesman, the students' professor stands by their conclusion. They may be freshmen, but theirs was an impartial, semester-long study that began without any preconceived notions, said Geoengineering Professor Tad Patzek.

"I may get mud on my face," Patzek said. "So be it." The study is a good one, he added.

But Monte Shaw, spokesman for the Renewable Fuels Association, a trade association for ethanol producers, sharply disagreed. "This issue has been looked at for 20 years, by the Department of Energy Argonne Lab and others. They concluded that ethanol releases 39 percent more energy than is required to produce it," he said.

Patzek said he received two angry phone calls from Washington, D.C., on Friday, the day after the study was released. The callers demanded to know the source of his funding.

There wasn't any special funding, Patzek said, explaining it was a regular college class that did the study. He said his specialty is the movement of fluid in rocks -- something far removed from ethanol. His research is supported by the Department of Energy and can be used by the oil industry, he said.

"I wanted to teach a freshman seminar on a subject that would have merit and scientific value," he said. "We chose ethanol because I wanted to learn more about the issue. Little did I know what the impact would be. There were initially 12 students, but two dropped out when they found out there was work to do," he said.

In a prepared statement, one of Patzek's students, Jason Lee, said that ethanol, which is distilled from field corn, appears to be environmentally friendly.

"But if you dig underneath, you find that it's really misleading," Lee said. "The amount of fuel and oil needed to use ethanol is greater than the value of energy ethanol provides. It's ridiculous to think it would decrease our dependence on oil," he said.

Patzek said his students' research showed that when all energy elements are included -- including use of pesticides and petroleum-based fertilizers on the corn, and all the petroleum energy used to harvest the corn, deliver it to market and then make ethanol -- the cost exceeds the additive's benefits.

The student report concludes it takes the equivalent of 4.93 gallons of gasoline to produce an energy output of 1.74 gallons. That's a net loss of 65 percent, the students said.

As the report was issued, the U.S. Senate on Thursday approved a provision in the new energy bill that would double the amount of ethanol to be used as a gas additive, to 5 billion gallons a year nationwide by 2012.

Both California senators opposed the bill -- arguing that the proviso might increase gas prices in California. However, most refineries in the state have already switched to ethanol as a nonpolluting substitute for MTBE (methyl tertiary-butyl ether), an additive that pollutes groundwater.

The UC Berkeley report used studies that relied on bad data, according to Shaw of the Washington-based Renewable Fuels Association. "There really is no debate. Once we look at the (UC Berkeley) study, I'm sure we'll find flaws."

Patzek demurs. "That Argonne study is flawed and full of faulty assumptions," he said. "I intend to add a chapter in our report pointing out the omissions and errors," he said.

The bottom line on ethanol: "We are burning the same amount of fuel twice to drive a car once," Patzek said.

"They're just wrong; their assumptions are flawed," Shaw replies.