According to a new paper from the World Resources Institute, producing even "modest" quantities of bioenergy would increase the demand for already-shrinking land.
The paper, authored by WRI senior fellow and former Environmental Defense Fund attorney Tim Searchinger, finds that the limited amount of land that is available for food and timber growth is insufficient to produce the amount of biofuel that would meet current targets.
He notes in a blog posted Wednesday that producing 20% of human energy needs from bioenergy by 2050 would require "an amount of biomass equal to all the plants harvested annually across the entire world today."
Searchinger goes on to suggest that cellulosic energy crops like grasses – while compatible with marginal lands – would be unable to produce as much ethanol per acre as corn. He says also that "bioenergy isn't carbon free," explaining that estimates often do not account for the carbon emitted when bioenergy crops are burned.
Groups were quick to point out concerns with the new working paper. National Corn Growers Association Corn Board member Keith Alverson said numerous other studies have reached different conclusions.
"When calculating the amount of energy used to produce ethanol, from farm to pump, ethanol represents a 40% net energy gain," Alverson said of ethanol's efficiency. "No other energy source comes close."
The paper also questions the ability of land to provide needed food and fuel, but Alverson said farmers are able to grow corn more efficiently each year. He said corn yields have increased by 88% since 1980.
Ethanol proponents, too, said the paper represented an incorrect picture of the food vs. fuel concern.
"WRI’s criticism of biofuels is based on the limited assumption that the U.S. and the rest of the world must choose between a cleaner, healthier environment resulting from renewable transportation fuels and an adequate, affordable food supply," said Tom Buis, CEO of Growth Energy.
Nonetheless, the report urges governments to phase out bioenergy production. It offers a few steps to making the change: a phase-out of biofuels subsidies; ineligibility of biofuels for low-carbon fuel standards; and maintaining current limits on the amount of ethanol blended into gasoline, among others.
In his blog post, Searchinger also suggests that solar cells may offer an alternative, generating more than 100 times as much useable energy per acre as bioenergy.
"The ultimate challenge is that land, particularly fertile land, is a finite resource that becomes ever more valuable as the world becomes more crowded," he wrote. "Using solar technologies to produce more of our energy and cropland to produce our food is the wiser, more efficient and food-secure path to a sustainable food and climate future."