WASHINGTON – Politicians hail ethanol (search), the corn-based gasoline additive, as a boon to the environment and a way to reduce America's dependence on foreign oil.
But ethanol also comes with its own environmental problems and scientists disagree over whether producing ethanol actually uses more fossil energy than it replaces.
The Senate this week will decide whether to double the amount of ethanol to be used in gasoline, to 5 billion gallons a year. Critics say the plan is just one more subsidy for corn growers. Supporters make the case that the proposal is essential to an energy policy that is less reliant on oil.
"It will reduce our dependence on foreign oil. It will protect the environment," says Senate Majority Leader Bill Frist, R-Tenn (search).
There is skepticism about those claims.
Ethanol's benefits are "a mixed bag," says Blake Early, a lobbyist for the American Lung Association (search).
Ethanol's clearest air quality benefit is that it significantly cuts carbon monoxide, he says. But ethanol also releases more nitrogen oxide, a key element of smog, and evaporates more easily than gasoline, causing still other air pollution problems, Early says.
On balance, ethanol "certainly isn't worse than gasoline," Early says, but "it's not that helpful from a smog perspective."
The government also has identified ethanol plants as significant air polluters, but has reached deals to curtail plant emissions.
And some scientists now say that ethanol, while not as troublesome as a methanol-based additive known as MTBE (search), also may complicate cleaning up gasoline spills into waterways and groundwater.
"It certainly is not all that benign," says Tom Curtis, an official of the American Water Works Association (search), which represents professionals involved in the drinking water supply business.
Curtis cites research indicating that gasoline plumes containing ethanol degrade more slowly in groundwater than plumes of only gasoline. Toxic chemicals such as benzene in ethanol-blended gasoline disperse more widely and take longer to degrade, the studies found.
These studies "are far from conclusive" and should be pursued further, says Monte Shaw, a spokesman for the Renewable Fuels Association (search), which represents the ethanol industry.
But he maintains that because ethanol replaces 10 percent of the gasoline, there is also less benzene and other toxic chemicals - normally found in gasoline - going into the water in the first place. And, he says, refiners can blend their gasoline in ways to counter the air pollution concerns caused by ethanol's evaporation.
Ethanol supporters emphasize that it is a motor fuel made in America and that it is not a fossil fuel - particularly from another country.
That, they argue, makes it perfect for improving America's energy security, as well as helping to fight global warming because greenhouse gases mostly come from the burning of fossil fuels.
Critics counter that ethanol does not come through as advertised on either of those points.
"Ethanol does not increase energy security," insists David Pimentel, an agricultural ecologist at Cornell University. "It remains a fact that it takes more energy to produce a gallon of ethanol than you get out of it."
Pimentel says ethanol, when made from corn, should not even be considered a renewable fuel - and actually provides little help on global warming. It takes large amounts of nonrenewable natural gas, coal, and oil to make fertilizer and grow the corn, process ethanol and transport it in trucks and rail cars.
Pimentel's claims, frequently cited by ethanol critics, have prompted a pile of research. Reports from the Agriculture Department, the Energy Department's Argonne National Laboratory, and by scientists at two other universities concluded that Pimentel is wrong.
Michael Wang, a co-author in both the Argonne and Agriculture Department studies, maintains that Pimentel used old data that does not take into account substantial improvements in corn farming and ethanol processing. All of that, he contends, has reduced energy use.
In an interview, Piementel dismissed his critics and said he recently updated his findings to reflect current production improvements. Still, he insists, the numbers show a 30 percent net energy loss with ethanol.
By contrast, the Argonne lab and Agriculture Department studies conclude 34 percent overall energy gain in using ethanol. Most of the energy used in making ethanol comes from coal or natural gas, domestic sources instead of petroleum-based gasoline that relies on imports, they note.