Pretty much since its passage in 2007, the Renewable Fuel Standard has been a controversial piece of legislation.

Enacted as part of the Energy Independence and Security Act, it requires increasing amounts of ethanol to be blended with gasoline.

But critics call the volumes of ethanol required unrealistic, and implementation has consistently lagged behind the mandated volumes of the biofuel.

DON'T MISS: Final 2016 Ethanol Rule: Fuel Blenders, Biofuels Interests Unhappy With EPA Numbers (Dec 2015)

Now, a new House bill seeks to undo the essential premise of the Renewable Fuel Standard.

House Resolution 5180 calls on the Environmental Protection Agency (EPA) to set an annual cap on the amount of ethanol that is required to be blended into the nation's gasoline supply.

The proposed limit is 9.7 percent of the country's anticipated fuel consumption for the coming year.

FlexFuel badge on E85-capable 2009 Chevrolet HHR

That's lower than the 10.1 percent called for in EPA volume requirements for 2016.

And the target of 18.1 billion gallons of ethanol this year is lower than the 22.3 billion gallons lawmakers had mandated for the year back in 2007.

The bill also stipulates that should the EPA fail to meet its annual deadlines for setting volume requirements—which has happened before—then the limit would revert to the total from the most recent year.

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The majority of blended fuel sold in the U.S. is currently "E10," containing 10 percent ethanol and 90 percent gasoline.

Proposed EPA E15 gasoline pump warning label for ethanol content

Blends with more ethanol are also available—on a limited basis—up to E85, which contains 85 percent ethanol.

Several years ago, the EPA also approved E15 fuel for use in all cars made in 2001 or later, but implementation has been extremely slow.

Gas stations have hesitated to pay the cost of installing the required "blender pumps," in part due to a lack of consumer demand.

Despite the EPA's approval, not all carmakers have approved their new models for E15.

The majority of new cars are approved to use E15 by their manufacturers, but some holdouts remain, including Mercedes-Benz and Nissan.

Passage of HR 5180 would likely frustrate efforts to increase E15 adoption, but it could set a more realistic standard for ethanol blending.

MORE: Why Isn't The 2016 Chevy Volt A Flex-Fuel Plug-In Hybrid That Can Use E85 Ethanol?

Previous ethanol targets have been difficult to reach in part because they call for specific volumes of the fuel to be added into the fuel supply, rather than a percentage of the gasoline actually consumed.

The original legislation did not take into account significant increases in fuel economy across the board, codified in a steady rise in corporate average fuel economy levels from 2012 through 2025.

Last month's average of 25.2 mpg for new cars was fully 5.1 mpg higher than the corresponding figure for October 2007, according to the University of Michigan Transportation Research Institute (UMTRI).

Non-ethanol gasoline pump

The original volumes of ethanol mandated by the 2007 RFS would be far higher than anticipated by the legislators, whose projections assumed steadily increasing gasoline consumption.

Instead, U.S. gasoline consumption has actually fallen for several years running, meaning most consumers seem to have little interest in the higher-ethanol blends.

The backers of HR 5180 argue that while basing ethanol targets on the actual amount of gasoline consumed might lead to lower levels of the biofuel, it could ensure that the resulting targets are actually capable of being met.

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