Senators on both sides of the aisle are pushing measures that would whack the corn ethanol portion of federal biofuel blending targets, unswayed by a recent Environmental Protection Agency proposal to slash next year's goal.

The efforts come as the House remains stalled on its legislative proposal, and after some lobbyists have suggested the EPA action last month could reduce congressional appetite to change the Renewable Fuel Standard.

"The hearing on Wednesday was a bit of a surprise," Michael McAdams, president of the Advanced Biofuels Association, said of a Senate Environment and Public Works Committee hearing on the Renewable Fuel Standard. "A lot of people thought that when the EPA released the rule that it would cut the legs out of doing anything legislatively."

But now lawmakers are concerned about letting the EPA take the reins on the fuel rule, which Congress passed in 2005 and expanded two years later to include advanced and cellulosic — made from cornstalks — biofuels as a way to reduce oil imports and greenhouse gas emissions.

While the move to slash the overall blending target to 15.21 billion gallons of biofuels next year, down from a scheduled 18.15 billion, was welcomed by the fuel rule's opponents, Congress is wary of the uncertainty a more activist EPA could invite.

"Members of the House and the Senate aren't enamored with a policy that needs to be adjusted by the EPA every year," said Jonathan Lewis, senior counsel with the Clean Air Task Force.

So the Senate got moving.

Odd-couple pairing Sens. Dianne Feinstein, D-Calif., and Tom Coburn, R-Oklahoma, introduced a measure to remove the corn ethanol segment of the mandate, which accounts for an overwhelming majority of domestic biofuel production.

Their concerns lined up with those expressed by the EPA, the oil industry, automakers, and agriculture and poultry groups. The lawmakers said the mandate's annual targets are accelerating too fast, forcing refiners to pump out fuel with higher concentrations of ethanol that opponents say harm car engines. They also said that corn ethanol is having an adverse impact on crop land and is driving up food prices.

"I strongly support requiring a shift to low-carbon advanced biofuel, including biodiesel, cellulosic ethanol and other revolutionary fuels. But a corn ethanol mandate is simply bad policy," Feinstein said.

And Sens. Ben Cardin, D-Md., and David Vitter, R-La., the top Republican on the Senate Environment and Public Works Committee, also championed legislation that would curtail corn's portion of the mandate.

The biofuel industry criticized the Feinstein-Coburn bill, and no doubt will have harsh words for the Cardin-Vitter effort once its details are known.

Biofuel boosters contend the oil industry, which is pushing for a full repeal of the mandate, is concerned about the impact a growing supply of ethanol has on its bottom line.

The biofuel industry also has defended the safety of E15 — gasoline blended with 15 percent ethanol, instead of the standard 10 percent. It notes that the EPA has approved it for use in cars made in 2001 or later, but opponents charge that most automakers won't cover E15-related damage in warranties.

The biofuel industry can rest a little easier knowing it has a friend in Sen. Barbara Boxer, D-Calif., chairwoman of the Senate Environment and Public Works Committee, which oversees the fuel rule. She warned at the end of Wednesday's hearing that lawmakers should not "turn our back" on the policy.

But while the Senate is churning, the House has hit a lull.

House lawmakers began working on legislation over the summer, but the EPA proposal has cooled some of the momentum.

A GOP committee aide says that the panel is considering a variety of options.

And therein lies the difficulty.

"The reason behind the stall is that, while they all agree they don’t like the [Renewable Fuel Standard], they don’t agree on why they don’t like it," said Paul Winters, a spokesman with biofuel group the Biotechnology Industry Organization.

The fuel mandate has strong backing from rural lawmakers, who say it has given birth to an industry that has revitalized communities in the heartland. Some of them — including those most supportive of corn ethanol — are key Republicans on the House Energy and Commerce Committee, such as Energy and Power Subcommittee Chairman Ed Whitfield, R-Ky., Energy and Environment Subcommittee Chairman John Shimkus, R-Ill., and Communications and Technology Subcommittee member Lee Terry, R-Neb.

Still, they're open to changes to the rule. In a July hearing, even Shimkus — perhaps, historically at least, the committee's most vocal corn ethanol promoter — said the mandate needed changing.

Lewis, of the Clean Air Task Force, said Shimkus' shifting position is indicative of the momentum behind a legislative push to change the rule. And he said it's one that Boxer alone might not be able to stop.

"I think Sen. Boxer is going to have to reconsider her opposition to changes to the [Renewable Fuel Standard] over time as it becomes increasingly impossible to implement it as Congress intended back in 2007," he said.

This article was first published Dec. 15 and has been corrected to reflect that Sen. Tom Coburn filed a corn ethanol measure with Sen. Dianne Feinstein.