Backed by the White House, corn-state governors and solid blocks on both sides of Congress’s partisan divide, the politics of biofuels could hardly look sunnier. The economics of the American drive to increase ethanol in the energy supply are more discouraging.

American corn-based ethanol is expensive. And while it can help cut oil imports and provide modest reductions in greenhouse gases compared to conventional gasoline, corn ethanol also carries considerable risks. Even now as Europe and China join the United States in ramping up production, world food prices are rising, threatening misery for the poorest countries.

The European Union has announced that it wants to replace 10 percent of its transport fuel with biofuels by 2020. China is aiming for a 15 percent share. The United States is already on track to exceed Congress’s 2005 goal of doubling the amount of ethanol used in motor fuels to 7.5 billion gallons by 2012. In his State of the Union speech in January, President Bush set a new goal of 35 billion gallons of biofuels by 2017. In June, the Senate raised it to 36 billion gallons by 2022. Of that, Congress said that 15 billion gallons should come from corn and 21 billion from advanced biofuels that are nowhere near commercial production.

The distortions in agricultural production are startling. Corn prices are up about 50 percent from last year, while soybean prices are projected to rise up to 30 percent in the coming year, as farmers have replaced soy with corn in their fields. The increasing cost of animal feed is raising the prices of dairy and poultry products.