The Environmental Protection Agency proposed slashing anticipated biofuel blending targets for 2014 on Friday, a move that rattled the biofuel industry while emboldening the renewable fuel mandate’s Capitol Hill opponents.

The EPA proposed requiring refiners to blend 15.21 billion gallons of renewable fuels into conventional transportation fuel next year, though it does include some variability that could allow as much as 15.52 billion gallons. That’s a cut from the 18.21 billion gallons Congress set as a target for 2014 when it passed the Renewable Fuel Standard in 2005.