A decade ago, lawmakers in Washington tried to address a trifecta of thorny challenges with one simple fix that has turned out to be anything but easy to assess.
The problems: an overreliance on foreign oil, rising greenhouse gas emissions and tepid economic growth.
The solution: the Renewable Fuel Standard, commonly known as the ethanol mandate. Enacted in 2005 and expanded two years later, the legislation required that refiners blend an increasing amount of biofuel into the gasoline that powers most American cars.
