Corn ethanol faces its limits under EPA fuel mandate

Corn ethanol has reached its official limit under the Environmental Protection Agency's renewable fuel program, which means other less-developed, low-carbon fuels will have to step up to fill a 21 billion-gallon gap by 2022.Depending on where you stand on the future of the Renewable Fuel Standard, the cap on corn can be a blessing, a challenge or a curse.Under the Renewable Fuel Standard, which was passed by Congress in 2007, refiners must blend 36 billion gallons of biofuels in the nation's gasoline and diesel fuel supply by 2022. Corn ethanol, the biggest component of the program, and other conventional biofuels are capped at 15 billion gallons beginning in 2017.That means the remaining 21 billion gallons must be met by advanced biofuels derived from everything from municipal waste to switch grass cellulose and even algae. But those fuels are falling short of the amount required to be blended as of this year, raising serious questions about the future of the program after 2022.Gasoline and diesel refiners say the gap will create a situation in which differing biofuel factions spar against one another over their share of the market.