The quest for a fuel that will both reduce air pollution and U.S. dependence on imported energy has led to massive investments in ethanol and other fuels produced from plants. Backers of programs to develop such energy resources include farmers and agricultural enterprises that see bigger profits as demand for corn, soybeans and other crops increases. But, as VOA's Greg Flakus reports from Houston, critics say the promise of biofuels is mostly hype.

Depending on who is speaking, ethanol and other biofuels are either the future of energy and the answer to air pollution or a false promise that diverts attention from finding real solutions to both our energy and environmental problems.

The biggest biofuel industry is that of ethanol, an alcohol additive that is produced from fermenting plant material. In the United States, most ethanol is produced from corn and, not surprisingly, corn farmers and politicians who represent corn-growing states are big backers of ethanol.

It is generally agreed that ethanol would be too costly for consumers if it were not heavily subsidized. But Kristin Brekke of the Sioux Falls, South Dakota-based American Coalition for Ethanol argues that the government should support alternative energy producers.

"The petroleum industry is certainly subsidized 10 times as much as the ethanol industry is," said Kristin Brekke. "Ethanol is really proving to be a promising alternative and, given the question of how long oil supplies will be around and environmental impacts being on people's minds as well, I think it is right that we are investing in the future, which is renewable fuels."

The US government gave ethanol a further boost last year when a commonly used oil additive was banned for environmental reasons and oil companies expanded the availability of a blend of ethanol and gasoline.

In response to increased ethanol production, there has been a 15 percent increase in corn production nationwide and even farmers in parts of the country where corn has not been a traditional crop are now starting to grow it.

But Kristin Brekke says this is a momentary situation that will be eased as soon as ethanol producers are able to produce fuel from other organic material, including waste products containing cellulose. That, she says, is when the true potential of this renewable energy source will be realized.

"The corn that could be used for ethanol here in the United States, without displacing those other needs as well, if you add to that, too, the potential of cellulosic ethanol, over the long term, those two things together could displace about half of the gasoline we currently use," she said.

One of the chief critics of this rosy scenario is Cornell University ecologist David Pimentel, whose studies of ethanol and other biofuels call into question their efficacy.

"Even using the Department of Energy's optimistic numbers, they claim we used 20 percent of the corn last year to produce five billion gallons of ethanol," said David Pimentel. "What does five billion gallons mean to petroleum use in the United States? It is less than one percent. If we use 100 percent of the corn, which would be an impossibility, to produce ethanol, it would produce seven percent."

Professor Pimentel also rejects the benefit to the environment that ethanol supporters often cite because the fuel produces far less harmful emissions than do fossil fuels. He says it is important to look at the effects of a massive increase in corn production as well.

"Corn production, for example, causes more erosion than any other single crop grown in the nation," he said. "It uses more nitrogen fertilizer than any other crop and that nitrogen fertilizer gets washed down the Mississippi. The National Academy of Sciences reports that corn production is the prime cause of that dead zone down in the Gulf of Mexico."

Pimentel and his research partner Tad Patzek have also done studies showing that, when all production efforts are factored in, it takes 29 percent more fossil fuel energy to produce a quantity of ethanol than the energy it provides. The study shows there is a similar ratio for producing bio-diesel from soybeans and other agricultural products.

But other recent studies have contradicted those findings. Douglas Tiffany, an economist at the University of Minnesota, worked on one such study.

"We were very thorough and looked at all the energy inputs," said Douglas Tiffany. "Our results conformed to the results of Argonne National Lab and some others that show a positive energy balance from the production of both ethanol and biodiesel."

But the University of Minnesota study also showed that some plant material may be better suited than corn for fuel production and that biodiesel may hold more promise than ethanol. The Minnesota researchers coincided with the Cornell study in saying that bio-fuels are not likely to reduce oil consumption to any significant degree. Still, Tiffany says, the rising cost of petroleum on the world market will keep interest alive in bio-fuel programs.

"There is strong incentive to do these bio-fuels when we have high crude oil prices," he said. "So, in some ways, it is the price of crude oil that is pushing a lot of this development. The question is should it be under control or should governments apply judicious targets?"

Critics like Cornell's David Pimentel, however, argue that the proper response to higher crude oil prices should be increased conservation and the development of other forms of energy that show more promise of being cost effective.