The battle over the Renewable Fuel Standard is heating up a little more than a month before the Environmental Protection Agency is expected to reduce the amount of biofuel required in gasoline and as an investigation begins into the agency’s handling of the law.

On Nov. 30, the EPA is expected to lower the Renewable Fuel Standard, the annual requirement for refiners to blend corn-based ethanol and other biofuels into gasoline and diesel, for 2014, 2015 and 2016 from what Congress initially required.