Klobuchar and Grassley represent two states where a lot of corn is grown and ethanol is produced. The federal Renewable Fuel Standard calls for 16.55 billion gallons of biofuels to be sold this year and 18.5 billion gallons in 2014. The US Environmental Protection Agency admits that the US may have hit the "blend wall," where more biofuel is being produced than the amount that is being demanded. The American Fuel & Petrochemical Manufacturers and the American Petroleum Institute have been petitioning to get that biofuel volume down to a little more than 14.8 billion gallons for next year. Big Oil has been warning Washington that producing too much biofuel would mean "severe economic harm" for the US. The American Petroleum Institute thinks that the senators' allegations are "a distraction from the fact that the [renewable fuels standard] is broken."
While the EPA has approved the use of E15 in newer cars, demand for it hasn't yet grown. The Renewable Fuels Association (RFA) says there are only about 30 gas station in eight states offering E15. Biofuel organizations say oil companies are pulling shenanigans to stop E15 from spreading; RFA says it knows of at least one gas station owner in Kansas who was pressured by Big Oil to stop offering E15.