US Secretary of Agriculture Tom Vilsack expresses concern about the future of the RFS

US Agriculture Secretary Tom Vilsack said he is concerned about the future of the Renewable Fuel Standard (RFS), the federal mandate that requires ethanol and biodiesel to be blended into the nation's fuel supply, according to media reports in the Des Moines Register.

President-elect Donald Trump nominated two RFS opponents to key agencies: Former Texas Governor Rick Perry is slated to lead the Energy Department and Oklahoma Attorney General Scott Pruitt is tapped for the US Environmental Protection Agency.

"There have been a series of mixed signals about the Renewable Fuel Standard," Vilsack said during a Des Moines Register editorial board meeting Monday. "It predated the election, and it's not been cleared up with the appointments."

Iowa's former governor said the oil industry's attack on the RFS has been comprehensive — through regulations, the courts and public opinion.

"There’s been an ongoing effort on the part of the oil industry to get rid of the Renewable Fuel Standard," Vilsack said. "I think people who are supportive of the renewable fuel standard should be incredibly vigilant now."