UCS said biofuel mandates proposed by the Environmental Protection Agency rely too heavily on food-based biofuels to make up for a shortfall in cellulosic biofuels, which are made from non-edible food stocks.
Jeremy Martin, a scientist at UCS's clean vehicles program, said that while last year's drought crimped crops that could be used for biofuels, the EPA shouldn't promote alternatives that compete with food supplies.
"EPA should exercise more discretion to reduce competition between food and fuel," he said in a statement. "Cellulosic biofuel production is behind schedule, but that doesn't mean we need to accelerate mandates that threaten our environment and our food supplies."
UCS estimates there's enough non-food feedstock in the United States to meet biofuels targets under a Renewable Fuels Standard, though it would take a bit longer to meet national objectives.
Oil lobby American Petroleum Institute, often critical of the RFS, said EPA's proposed mandate for 14 million gallons of biofuel for 2013 depends on a "non-existent" commercial cellulosic biofuel sector. EPA's proposal, said API, "is unworkable."