In 2007, Congress passed the Energy Independence and Security Act, which includes a Renewable Fuel Standard requiring certain amounts of ethanol to be blended into the national fuel supply.
But over the past few years, the volumes of ethanol called for by the rule have been deemed unrealistic by analysts and critics.
And last week, the U.S. Environmental Protection Agency (EPA) announced a proposal to cut the amount of ethanol that is required to be blended into the gasoline supply.
If approved, this would be the first cut in ethanol requirements since the Renewable Fuel Standard was enacted almost nine years ago, according to CNN Money.
The 2007 standard required that 18.15 billion gallons of ethanol be blended with gasoline in 2014.
But the EPA proposal called for reducing that amount to between 15 and 15.52 billion gallons.
Big square baler harvesting wheat straw for production of cellulosic ethanol
Under the current rules, the levels of ethanol have increased yearly, with the 2013 figure set at 16.55 billion gallons.
The Renewable Fuel Standard was originally seen as a way to reduce dependence on foreign oil and cut carbon emissions, by encouraging use of a fuel that could be produced domestically from renewable sources.
But setting requirements for fixed amounts of ethanol to be blended with gasoline did not account for changes in overall fuel consumption.
ALSO SEE: EPA Resets Ethanol Rules To Reflect Reality: Cellulosic Sources Don't Exist (Apr 2014)
The fuel efficiency of new cars and trucks sold in the U.S. has increased appreciably since 2007--meaning drivers are using less fuel--largely due to increasingly stringent Corporate Average Fuel Economy standards starting in 2012.
The deep economic recession that started in 2008 and lasted several years also reduced work-related commuting as jobs were lost.
Yet the ethanol requirement didn't change to reflect this, because the rule only considers ethanol in terms of volume, not as a percentage of overall fuel consumed.
2011 Buick Regal flex-fuel badge
Consequently, adherence to the law's original targets could soon require higher volumes of ethanol than can be blended with gasoline--a problem known as the "blend wall."
Much of the gasoline sold in the U.S. is E10 fuel--a blend of 10 percent ethanol and 90 percent gasoline.
Blends with more ethanol are available on a very limited basis, including E85--with 85 percent ethanol--for "flex-fuel" vehicles.
And while the EPA approved sale of E15 several years ago for cars made in 2001 or later, the number of gas stations that have paid to install the required "blender pumps" is small--in part because there is no consumer demand for it.
The EPA proposal will now go through a 60-day public comment period.
[hat tip: Randall Hamlet]