The Environmental Protection Agency (EPA) has approved crops to use in a renewable fuel program that environmentalists have warned are invasive species.

The agency’s approval makes way for the two plants to be used in a federal program that mixes biofuel with gasoline, but adds extra restrictions to prevent their unexpected spread.

That renewable fuel standard, administered by the EPA, calls for levels of biofuel to be mixed into transportation gas in order to cut American reliance on oil and maximize use of new energy resources.