"The real problem with corn ethanol...there isn't enough"...

Entrepreneurs like Bill Gates have begun investing in it. Every blue ribbon commission on energy has embraced it as a fuel of the future. And both the government and several leading environmental and public policy groups, including the Natural Resource Defense Council and the Energy Future Coalition , have suggested that ethanol — combined with other strategies like plug-in hybrids — could reduce the need for imported oil to zero.

Until recently, there were only two kinds of ethanol that were at all well-known: ethanol made from sugar cane , which accounts for approximately 40 percent of Brazil's non-diesel automotive fuel; and corn ethanol , which, at nearly 4 billion gallons annually, and used mainly as an additive, accounts for between two and three percent of America's automotive fuel.

Corn ethanol's image has suffered from its association with the agribusiness lobby — in particular a politically connected company called Archer Daniels Midland — and with presidential candidates hustling support every four years in the Iowa primaries. It has also suffered from the widespread belief that it takes more energy to make corn ethanol than the end product gives back, as well as from the belief that corn ethanol can't compete with gasoline without a generous federal subsidy.

All three complaints are outdated. A.D.M. is no longer the only big player in the field, which is growing rapidly to meet a Congressional mandate contained in the 2005 energy bill to expand the production of ethanol and biodiesel to 7.5 billion gallons by 2012, a target that almost surely will be met much earlier. Meanwhile, nearly every reputable study of corn ethanol's net energy balance (the value of inputs like plowing, planting and fertilizing vs. the value of the outputs) shows net benefits of 25 to 40 percent.

Finally, even accounting for its lower energy content, corn ethanol is competitive with gasoline in the United States when the price of oil is at $45 or above. That is well below the price of oil today , and also below where the U.S. Energy Information Agency expects the oil price to be over the next 25 years.

There is an added benefit. The corn ethanol studies also show that corn ethanol has a net benefit in greenhouse gas emissions of up to 20 percent.

So we are getting what we want: a competitive substitute for Middle Eastern oil that could also make a positive difference, albeit modest, in greenhouse gas emissions.

The real problem with corn ethanol is simply that there isn't enough of it, and for all sorts of good reasons having to do with sensible land use and the food supply, there never will be. By one estimate, devoting the entire U.S. corn harvest in 2005 to ethanol would have offset less than one-sixth of the nation's gasoline