More than a year ago, Congress passed a law requiring massive increases in the production of ethanol and other biofuels, but with the economy tanking, concerns about the mandate are popping up in every corner.

The Renewable Fuel Standard, passed as part of the Energy Independence and Security Act of 2007, requires the nation to produce 36 billion gallons of biofuels by 2022. Although increasing biofuels production at home could decrease U.S. dependence on foreign oil, the law has been controversial from the get-go as many have questioned the sustainability of corn-based ethanol.

Now, new worries have surfaced.

"In two short years, we face a very different world," said Sen. Thomas Carper, D-Del., at a Wednesday hearing in the Subcommittee on Clean Air and Nuclear Safety. "We face trying a economic time that is impacting our way of life -- including our fuel consumption and our investments in advanced fuels."

With less money to spend, Americans are consuming 2 billion gallons less gasoline per day now than they were when the RFS passed, yet the mandate requiring increased production of biofuels hasn't changed.

"Are we moving too fast for our infrastructure and engines to handle the biofuels safely?" Carper asked witnesses at Wednesday's hearing.

The answer to that question depends largely on how the Environmental Protection Agency decides to balance the implementation of the RFS with environmental concerns, many witnesses said. However, the EPA has yet to release its rule on the issue -- a sore subject for some industry representatives and policymakers, including Sen. David Vitter, R-La.

"Regulations to implement the RFS standards … were supposed to be finalized by last December, and they aren't in sight," Vitter said.

The delay has some environmentalists concerned, including Nathanael Greene, director of renewable-energy policy for the Natural Resources Defense Council, an environmental organization.

"It's extremely easy for biofuels to be produced in a way that actually leads to increased global warming," Greene said. "If using one acre of corn to make ethanol leads to just one-tenth of an acre of rainforest clearing, then all the benefits of avoided gasoline for the first 30 years are wiped out."

Corn-ethanol opponents like Greene fear the EPA delay means it won't include adequate safeguards when the rule finally emerges.

"There are efforts to take out (of the rule) critical provisions through backdoor politics," Greene said.

For instance, some policymakers, including Sen. John Thune, R-S.D., have pushed for higher ethanol blends to be allowed for general use.

But using mid-level ethanol blends containing 12 to 20 percent ethanol in regular cars and trucks could be dangerous for public health, said Blakeman Early of the American Lung Association.

That's because using these blends in non-flexible fuel vehicles could increase ozone emissions, he said.

"Ozone pollution can kill," Early told senators Wednesday. "High-ozone days increase the risk of dying early … (and) breathing moderate amounts day in and day out can increase the chance of dying from respiratory illnesses."

More research needs to be conducted before mid-level blends are approved, Early said.

"There has only been one scientific study on tailpipe emissions from today's cars running on E-15 or E-20 (ethanol blends)," he said.

In order for industry to phase out corn-based ethanol, though, producers need to increase production of new, advanced biofuels made from non-food feedstocks, like switchgrass and agricultural waste. The RFS requires that 21 billion of the 36 billion gallons mandated by 2022 come from advanced biofuels, but that won't happen without investments, which hinge on the EPA rule, said Michael McAdams, executive director of the Advanced Biofuels Coalition, which promotes the fuels.

"There is a need to get this rule done in the current credit market," McAdams said. "If you look at what's happened with investment since the end of 2008, it's like it goes off a cliff. This (rule) is key to driving the markets to fund advanced biofuels."

The technology is ready; all that's needed is the money to get it off the ground, said Kelly Tiller, director of external relations at the University of Tennessee Office of Bioenergy Programs.

The university has partnered with DuPont Danisco Cellulosic Ethanol, a biofuels company, to build a demonstration plant in Tennessee that will begin producing fuel by the end of the year.

"We are no longer on the verge," Tiller said. "Cellulosic biofuels are being produced today."

But not at the quantities needed to satisfy the demands of the RFS, said Charles Drevna, president of the National Petrochemical and Refiners Association, a trade organization.

"We are required to blend cellulosic ethanol now, not later," Drevna said.

With a new economic climate, the ambitious RFS as originally crafted may no longer be feasible, Drevna said.

"Let's suspend the RFS for corn ethanol where it is right now … and then use biofuels when they're available," he said. "A static statutory process may or may not fit the economic realities of today.

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