Western governments that are promoting the large-scale conversion of plants into fuel should reconsider the strategy, which is “unsustainable,” according to a new report from a prominent environmental think tank.

“I would say that many of the claims for biofuels have been dramatically exaggerated,” Andrew Steer, president of the World Resources Institute, a global research organization based in Washington that is publishing the report this morning, told The New York Times. “There are other, more effective routes to get to a low-carbon world.”

Several studies have found that the policy has helped drive up global food prices, has worsened some types of air pollution and has done relatively little to reduce overall emissions of carbon dioxide, the gas primarily responsible for global warming, according to The Times report.

The institute’s paper cited mandates adopted by U.S. policy-makers that require as much as 30 percent to 40 percent of the American corn crop to be turned into fuel for cars each year, displacing about 6 percent of the nation’s demand for gasoline.

This policy is likely to use up vast tracts of fertile land that could be devoted to helping feed the world’s growing population, the institute said.

Where there is spare land, bioenergy is a “stunningly inefficient” way to use it, Tim Searchinger, lead author of the paper, told the London-based Responding to Climate Change, a news and analysis website. Making ethanol from corn harnesses 0.3 percent of the sun’s energy, compared with 16 percent for a solar panel.

“The basic rule is: Don’t divert the productive capacity of land to bioenergy because there is always a big cost. People have just not calculated those costs,” Searchinger told RTCC. “We’ve only got one planet, with only so much land. If you use land for one purpose, you can’t use it for another.”