In early 2007, two University of Minnesota economists forecast that biofuels would sharply increase food prices by 2020, leading to a steep rise in the number of empty bellies in the world.

How wrong they were. Soaring rates of hunger didn't take a generation. It took a year.

The president of the World Bank recently estimated that 100 million more people around the world have slipped into hunger in the past year, in the wake of soaring oil and food prices.

"The kinds of price increases that we were using out to 2020 already have occurred and been exceeded," said Benjamin Senauer, one of the authors of an article in Foreign Affairs magazine that raised dire warnings brushed aside by the biofuels industry.

"There aren't villains in this," Senauer said. "I don't see the corn growers, the Renewable Fuels Association or [ethanol advocate Gov. Tim] Pawlenty as a villain. What we have here are unintended consequences."

He added, "It's remarkable, although not in a good sense, how much of what we said would come true [did], far before we predicted."

The International Food Policy Research Institute, a nonprofit think tank in Washington, D.C., recently estimated that 20 to 33 percent of the rise in grain and seed-oil prices worldwide can be tied to biofuel production.

Food riots and protests have broken out in more than two dozen countries, from Egypt and Morocco, to Haiti and Mexico, to Indonesia and the Philippines.

Minnesota corn farmers and national advocates for renewable energy plead not guilty. They say growing incomes and appetites in China and India, soaring oil prices, commodity speculation and other factors play a far larger role in food prices than does turning grain into ethanol.

"Is corn price affecting the price of food? The answer is yes -- by 4 percent," said Matt Hartwig, spokesman for the Renewable Fuels Association in Washington.

"Ninety-six percent can be attributed to other factors, many of them involving oil," he said.

Twenty-four percent of the U.S. corn crop last year was used in ethanol production.

But Hector Kramer, a Minnesota corn grower, noted that in 2007 corn used in ethanol consumed 3.1 billion bushels -- a billion more than a year earlier -- even as the U.S. corn crop harvest produced 2.5 billion more bushels.

"We grew more extra corn than we've used for the ethanol," he said.

Senauer and co-author C. Ford Runge concede that many forces have converged to push food commodity prices higher in recent months.

But using corn, sugar and other food staples to make ethanol is a major factor in rising food prices, both say. In Runge's view, rising oil prices have only increased the competition between fuel and food.

"The more expensive a barrel of oil is, the more you can afford to pay for corn and turn it into ethanol," Runge said. "I don't think we'd have predicted $120 oil or $6.50 corn a year ago."

He said ethanol producers have reason to root for soaring oil prices.

"If price of oil fell and corn remained relatively high, the ethanol industry would be on the floor dead in a matter of months," Runge said.

Senauer said governments should pare back ethanol subsidies.

"The bottom line is that the United States and other developed countries need to seriously reconsider their biofuels policy," he said. "This is something they can do something about."

The federal government pays 51 cents a gallon to ethanol blenders, the equivalent of $1.43 for every bushel of corn used to make that gallon.

"We're treating corn as $1.43 a bushel more valuable as a fuel than a food ingredient," Senauer said. "Does that seem right?"

Mike Meyers • 612-673-1746