"Cellulosic ethanol is far superior...so little carbon-based fuel is used to produce it"...

consumption, which exceeds 140 billion gallons a year, and nobody is talking about converting anything close to every kernel of corn to fuel.

What the experts are talking about is another kind of ethanol: cellulosic ethanol . This type of ethanol can be derived from a range of crops, including native grasses like switchgrass, trees like poplar, and even the waste components of farming and forestry — in short, just about anything rich in cellulose.

This is where the real promise of ethanol lies. Crops that yield cellulosic ethanol can be grown specifically for energy, in some cases on agriculturally marginal land without pesticides or fertilizer. And the energy-in energy-out balance is terrific: it gives back about five times more energy than it takes to produce, according to most studies.

One reason for this is that the manufacturing process consumes the entire plant, including lignin, a non-fermentable component of the plant that can be burned to run the ethanol refinery. And while both forms of ethanol are better than gasoline for reducing greenhouse gas emissions (since the CO2 they absorb from the atmosphere while growing helps offset the CO2 they produce during combustion), cellulosic ethanol is far superior on this score because so little carbon-based fuel is used to produce it.

The rub is this: at the moment, there is no commercial production of cellulosic ethanol in the United States. A Canadian company called Iogen , a leader in the field, makes its ethanol from wheat straw, and is planning a major facility in Idaho, and BP and DuPont are getting into the game. A Spanish company called Abengoa could have its operations up and running by next year. Secretary of Energy Samuel Bodman recently announced a goal of making cellulosic ethanol a practical and cost-competitive alternative by 2012, with sufficient commercial production to

A zero-emission fuel cell vehicle powered by hydrogen — a 'Freedom Car,' in Mr. Bush's words, running on 'Freedom Fuel.'

displace 30 percent of the nation's gasoline consumption by 2030. These are not impossible goals, but a national commitment and big money will be needed to meet them.

President Bush did not really start paying attention to energy problems until 9/11, when it became clear that our usually reliable sources of Middle Eastern oil were seriously at risk.

In addition to the predictable supply-side policies (drilling in the Arctic National Wildlife Refuge, for instance) Mr. Bush offered up, as the ultimate savior, a hydrogen economy . The centerpiece would be a zero-emission fuel cell vehicle powered by hydrogen — a “Freedom Car,” in Mr. Bush's words, running on “Freedom Fuel.” Such a vehicle would not only end our dependency on oil. It could also have payoffs in terms of global warming (a benefit that went largely unmentioned by Mr. Bush, who does not like to acknowledge the dangers of climate change).