The RFS was enacted to reduce foreign-oil dependence while boosting purchases from domestic corn suppliers, and it mandates that Americans double biofuels usage by 2022 to 36 billion gallons annually, but it has also been a source of criticism. Some environmentalists say biofuels are more polluting, while others have argued that food supplies are reduced when some of the country's corn is diverted to fuel.
California's low carbon fuel standard was established in 2007, and requires that carbon intensity in the state's transportation fuels be lowered by 10 percent by the end of the decade. The plan also offers more flexibility to meet lower greenhouse-gas emissions than merely mandating greater biofuel use. That's meant a push for more electric-vehicle sales in the most populous US state as well as reduced emissions from coal-fired electricity plants.
Republican presidential candidate Donald Trump has said he's in favor of maintaining the RFS. As recently as May, Trump vowed his support of the RFS, and use the issue to criticize then-Republican opponent Ted Cruz for what he said was his support from Big Oil. Clinton had previously hinted that the RFS could be improved.