Sir

We fully agree with your Editorial 'Kill king corn' (Nature 449, 637 2007) that corn (maize) is not a good feedstock for biofuels for a host of environmental, economic and humanitarian reasons.

We also agree that a sustainable biofuels industry needs to rely on non-food crops, such as cellulose from switchgrass or poplar trees, jatropha and possibly corn stover (stalks). Further research and development is necessary before such feedstocks will become commercially viable.

In the United States, neither the 51 cents per gallon tax allowance given to blenders who mix ethanol (the biofuel derived from corn) into their petrol, nor the 54 cents per gallon tariff on imported ethanol are defensible. The latter serves largely to keep low-cost Brazilian ethanol from sugar cane out of the country.

Unfortunately, the new Farm Bill currently moving through Congress looks almost certain to preserve the farm-subsidy system of direct payments based on a per-bushel price scale for corn and other major crops. Subsidies go mainly to large farm operations, as these produce the most bushels. Corn producers have been among the largest beneficiaries of these subsidies, which encourage overproduction and excessive use of nitrogen fertilizer, the main source of the very potent greenhouse gas nitrous oxide. A new report from the National Academy of Sciences, Water Implications of Biofuels Production in the United States, also warns: “If projected future increases in use of corn for ethanol production do occur, the increase in harm to water quality could be considerable.”

The current system of farm subsidies should have been reformed long ago to reward sound environmental practices, set an income cap for those receiving government payments and provide insurance against weather-related disasters.

But rather than killing king corn, we would prefer to say that the emperor — corn-based ethanol — has no clothes.