Parkinson is correct that increasing global demand and higher production costs are pushing food prices up, but this is no excuse for using our tax dollars to subsidize the burning of 30 percent of our corn crop to produce less than 3 percent of our fuel. Furthermore, bioethanol has the really negative environmental impact of encouraging tropical deforestation to produce more grain, thus accelerating global warming rather than reducing it.

This was confirmed in two highly cited publications in Science earlier this year. Only crops with a high free sugar content such as sugar cane and sweet sorghum make sense to ferment as these can yield 12 to 20 times more ethanol per acre than any grain crop.

Parkinson says if we were to stop adding ethanol to the nation's fuel supply, gas prices would increase by 35 cents a gallon, but he ignores the fact that ethanol takes 50 cents per gallon of subsidy to produce from corn. We could skip the ethanol and lower gas prices by 15 cents.

Parkinson points to "new technology" to make ethanol from switchgrass, corn stover and wheat straw, as if this somehow justifies our current use of corn. He also completely overlooks the critical importance of retaining these crop residues on the fields to conserve moisture, organic matter and soil structure. The use of corn stover for ethanol would threaten all the improvements in soil fertility and crop yields achieved through adoption of no-till agriculture during the past 15 years.

The use of switchgrass would threaten the entire CRP program by encouraging farmers to abandon grassland conservation for a more profitable alternative. Furthermore, the volumes of raw material required for each gallon of cellulosic ethanol are intractably large and their shipping costs are prohibitive over any distance. How many ethanol plants are we planning to build?

Most biofuel scientists agree ethanol, whether from corn or cellulose, is not going to be the answer to our fuel problems for one very basic reason -- it is not "energy-dense" enough. A gallon of ethanol has only 70 percent as much energy as a gallon of gasoline -- so it needs to be 30 percent cheaper than gas before anyone in their right mind should buy it. Then there are higher distribution costs -- 30 percent more weight must be shipped to deliver the same energy -- an inherent limitation that no technology will solve. It is also a highly corrosive fuel that diminishes engine life and increases maintenance costs.

Biofuels do have a role in our energy future, but in the form of biodiesel that is far more energy-dense than ethanol. But this biodiesel cannot be allowed to compete with our food supply as corn ethanol presently does.

It must be made from waste materials, algae, or non-food crops that can be grown on land too poor for food production, otherwise it will have the same undesirable impacts on the environment and food security as bioethanol.