Would using ethanol save energy?
That question, it turns out, is not easy to answer. Ethanol's enthusiasts point to the potential benefits of replacing gasoline with a renewable energy source that they contend will reduce America's reliance on foreign oil and cut greenhouse gases produced by fossil fuels. But the benefits of ethanol, particularly when it is produced from corn, are not so clear cut.
A number of researchers who have looked at the issue have concluded that more energy now goes into making a gallon of ethanol than is contained in that gallon. Others, however, find a net benefit, though most see it as relatively modest.
Those who question whether ethanol is as "green" as advertised say that supporters ignore or downplay the large quantities of natural gas used to produce ethanol, as well as the diesel fuel used to transport it from plants to markets. Moreover, growing corn requires heavy use of nitrogen fertilizers, made from natural gas, and requires extensive use of farm machinery, which burns fuel refined from crude oil.
Given the complexities of the calculations, there is a wide range of estimates of the benefits of ethanol.
On the positive side, analysts at the Agriculture Department concluded in their most recent assessment that ethanol offered a substantial gain, producing a positive output 67 percent greater than the energy inputs. But others who view ethanol favorably are more conservative, with several estimating the net energy benefit at about 20 percent.
David Pimentel, a professor of agriculture and life sciences at Cornell University, is one of several researchers who has challenged the Agriculture Department's conclusion. He has estimated that ethanol requires 29 percent more energy from fossil fuels than it delivers in savings from not using gasoline.
Dr. Pimentel, along with Tadeusz W. Patzek, a civil and environmental engineer from the University of California at Berkeley, published research finding that the Agriculture Department's analysis excluded the energy required to produce or repair farm machinery, as well as the steel and cement used to build the plants.
The Agriculture Department counters by noting that the professors failed to consider the energy benefit of certain ethanol byproducts, including corn oil and corn gluten, and said they were using old farm machinery data.
"They put all the energy on the ethanol," said Roger Conway, director of the department's office of energy policy and new uses.
The Agriculture Department also points to increases in corn yields, and efficiency improvements in the fertilizer and ethanol industries, which add to ethanol's energy benefit.
Dr. Pimentel acknowledged the omissions of some byproducts, saying they might have boosted the energy balance to as much as break even. But he said that even a best-case scenario, using his calculations, did not justify a heavy investment in ethanol. He called the push into ethanol a "boondoggle" motivated by farm-state politics and big profits.
Dr. Pimentel, who first began criticizing ethanol as an energy alternative about 25 years ago, said that he has never been supported by the oil industry. Dr. Patzek has worked as a researcher for an oil company in the past but said that his biofuels research had received no support from the industry.
Several environmental groups that support ethanol concede that the energy savings from corn-based ethanol may be limited, but they say it will serve as a crucial bridge to more efficient sources like switchgrass, a type of prairie grass that could potentially be used to produce ethanol.
The choice of what fuel to use to run an ethanol plant will also play a role in determining its ultimate energy efficiency. In Hereford, Tex., White Energy expects to use natural gas to power its ethanol plant, while another Dallas-based company, Panda Energy International, plans to use Hereford's ample supplies of cow manure as fuel.
Driven by the high cost of natural gas, about 10 of 39 ethanol plants under construction are being designed to run on coal, according to Robert McIlvaine, who runs a market research firm in Northfield, Ill.
Mr. Conway of the Agriculture Department called the move to cheaper and more abundant coal to run ethanol plants "preferable."
But Nathanael Greene, senior policy analyst at the Natural Resources Defense Council, which has supported ethanol's use, disagreed, pointing out that burning coal normally produces twice as much greenhouse gas as natural gas.
"This is going to significantly increase the local air pollution," Mr. Greene said, "and diminish the benefits of using ethanol."The New York Times
