The U.K. Royal Society has issued a report claiming that the effort to increase the use of biofuels may not result in significant reductions in greenhouse gas emissions, Bloomberg reports. The Renewable Transport Fuel Obligation program stipulates that 5 percent of the fuel sold by 2010 must be derived from a plant or crop, but because it doesn’t specify which biofuels must be used, the U.K. may be “locked in” to using inefficient energy sources. John Pickett, a professor with the Society, says that the government should change its policies to promote “fuels with the lowest emissions.”Some environmentalists have argued that biofuels can contribute to the depredation of rain forests and wetlands and have launched campaigns to fight the problem. “One biofuel is not the same as another,” says Pickett. The Society has also called for the fuel obligation to be extended for 20 years, thereby stimulating long-term investment in the industry.