Despite pressure to lower the amount of ethanol blended into the U.S. fuel supply, the Environmental Protection Agency (EPA) has boosted its proposed ethanol volume for 2017.

Under the Renewable Fuel Standard enacted in 2007, specific quantities of ethanol must be blended the national fuel supply. Recently, critics have tried to cap that amount.

But final ethanol volumes announced by the EPA late last Wednesday even exceed the amounts the agency itself proposed in May.

DON'T MISS: Bill to cap ethanol in U.S. fuel supply gains momentum

The EPA is now calling for 19.2 billion gallons of ethanol and other biofuels to be added to the fuel supply in 2017.

That represents an increase of 1.2 billion gallons from 2016 to 2017, according to the agency.

It's also higher than the 18.8 billion gallons proposed this spring by the EPA.

U.S. Capitol Building

U.S. Capitol Building

The move should please ethanol producers, but will likely rankle the fuel's opponents.

A bill currently circulating in the House of Representatives—Food and Fuel Consumer Protection Act of 2016—calls for the amount of ethanol to be capped at 9.7 percent of the total fuel supply.

The 18.8-billion-gallon figure proposed by the EPA would have made ethanol about 10 percent of the national fuel supply.

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When Congress approved the Renewable Fuel Standard in 2007, lawmakers anticipated neither overall increases in fuel economy—leading to a marked decrease in fuel consumption—nor the emergence of plug-in electric cars.

Because the standard requires fixed volumes of ethanol, the fuel must take up a larger portion of the overall supply than projected in order to achieve compliance.

But a large-scale commercial market to absorb all of that ethanol hasn't materialized.

2011 Buick Regal flex-fuel badge

2011 Buick Regal flex-fuel badge

A relatively small number of gas stations sell E85—a blend of 85 percent ethanol and 15 percent gasoline—and that fuel is approved for use only in "flex-fuel" vehicles with components specially hardened to tolerate it.

E10—10 percent ethanol, 90 percent gasoline—has long been the default fuel at many stations. The EPA also says all cars built in 2001 or later can run an E15 blend (15 percent ethanol) without modifications.

To boost ethanol use, the EPA recently proposed adding E16 through E50 blends to the same "flex fuel" category as E85.

MORE: EPA proposes to add more ethanol blends to 'Flex Fuel' category

This would presumably mean vehicles would have to be modified to burn the fuel, but the EPA hopes it will create more interest in both "flex-fuel" vehicles and the "blender pumps" that are required to add greater amounts of ethanol to gasoline.

Those "blender pumps" allow drivers to select the specific amount of ethanol to be blended into the gasoline they buy, and require a minimum purchase of 4 gallons.

Gas stations have been hesitant to install these pumps, owing to the cost of installation and lack of consumer demand for currently-available E15 and E85 blends.

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