In a greenhouse several hundred yards away, some of Geib's Pennsylvania State University colleagues are growing rows and rows of designer poplar trees. The slender plants have been genetically tweaked so that their woody fabric has a weak link, allowing better access to the energy-rich sugars inside.

One way or another _ whether by tinkering with trees or by borrowing the secrets of beetle larvae that eat them _ these researchers are determined to turn wood into liquid fuel for your car.

Called cellulosic ethanol, this fuel also can be made from grasses and other woody material, and some form of it could be in your car as soon as next year.

That's when refiners are required to start adding small amounts of the wood-based fuel to gasoline, both for energy security reasons and for the perceived environmental benefit. But for now the technology is costly, especially given the low price of oil. And the fledgling cellulosic industry will be hard-pressed to make as much as the law requires, analysts and federal officials say.

So efforts to improve the process, such as the ones at Penn State, are being closely watched.

"My sense is, this is like any other technology introduction," said Tom Tuffey, a renewable-energy expert at the nonprofit group Citizens for Pennsylvania's Future. "It will take some time to develop. When it develops, it's going to be pretty good stuff."

It is generally acknowledged that there will be no one-size-fits-all solution for powering the car of the future. Cars in Arizona might run on solar-powered electric batteries, say, while elsewhere, wind power could be used to make hydrogen to run a fuel cell. Gasoline will be part of the equation for decades.

In Pennsylvania, one answer could well be grasses and trees _ generally thought to be easier on the environment than corn, the current source of almost all U.S. ethanol.

A company called Coskata Inc., partly owned by General Motors, is building a 40,000-gallon-per-year cellulosic ethanol facility in Madison, 30 miles from Pittsburgh. Another firm is considering a plant in Clearfield County, west of State College. Two dozen cellulosic facilities are in the works elsewhere, anticipating the 2010 federal mandate for refiners to blend 100 million gallons of the stuff with gasoline.

But a recent report from ThinkEquity L.L.C., a San Francisco-based investment research firm, estimated next year's U.S.