UNITED NATIONS (AP) -- A U.N. expert on Friday called the growing practice of converting food crops into biofuel "a crime against humanity,'' saying it is creating food shortages and price jumps that cause millions of poor people to go hungry.

Jean Ziegler, who has been the United Nations' independent expert on the right to food since the position was established in 2000, called for a five-year moratorium on biofuel production to halt what he called a growing "catastrophe'' for the poor.

Scientific research is progressing very quickly, he said, ``and in five years it will be possible to make biofuel and biodiesel from agricultural waste'' rather than wheat, corn, sugar cane and other food crops.

Using biofuel instead of gasoline in cars is generally considered to cut carbon dioxide emissions, which contribute to global warming, although some scientists say greenhouse gases released during the production of biofuel could offset those gains.

The use of crops for biofuel has being pursued especially in Brazil and the United States.

Last March, President Bush and Brazilian President Luiz Inacio Lula da Silva signed an agreement committing their countries to boosting ethanol production. They said increasing use of alternative fuels would lead to more jobs, a cleaner environment and greater independence from the whims of the oil market.

Ziegler called their motives legitimate, but said that ``the effect of transforming hundreds and hundreds of thousands of tons of maize, of wheat, of beans, of palm oil, into agricultural fuel is absolutely catastrophic for the hungry people.''

The world price of wheat doubled in one year and the price of corn quadrupled, leaving poor countries, especially in Africa, unable to pay for the imported food needed to feed their people, he said. And poor people in those countries are unable to pay the soaring prices for the food that does come in, he added.

``So it's a crime against humanity'' to devote agricultural land to biofuel production, Ziegler said a news conference. ``What has to be stopped is ... the growing catastrophe of the massacre (by) hunger in the world,'' he said.

As an example, he said, it takes 510 pounds of corn to produce 13 gallons of ethanol. That much corn could feed a child in Zambia or Mexico for a year, he said.

Benjamin Chang, a spokesman for the U.S. mission to the United Nations, said the Bush administration didn't consider biofuel development a threat to the poor.

``It's clear we have a commitment to the development of biofuels,'' he said. ``It's also clear that we are committed to combatting poverty and supporting economic development around the world as the leading contributor of overseas development assistance in the world.''

Ziegler, a sociology professor at the University of Geneva and the University of the Sorbonne in Paris, presented a report Thursday to the U.N. General Assembly's human rights committee saying a five-year moratorium on biofuel production would allow time for new technologies for using agricultural byproducts instead of food itself.

Researchers are looking at crop residues such as corn cobs, rice husks and banana leaves, he said. ``The cultivation of Jatropha Curcas, a shrub that produces large oil-bearing seeds, appears to offer a good solution as it can be grown in arid lands that are not normally suitable for food crops,'' he said.

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