for National Geographic News
Amid growing concerns about unstable oil supplies and the impact of fossil fuels on global warming, biofuels are receiving increased attention.
A new study now suggests that the most important biofuelethanol, which is made from corn in the United Statesis more energy efficient than previously thought.
Some prior studies have suggested that ethanol production may consume more energyfrom nonrenewable sourcesthan is available in the resulting fuel.
But a reexamination of those studies show that current corn-ethanol production technologies are far less petroleum-intensive than gasoline, though both fuels have similar greenhouse gas emissions.
"The doomsdayers are wrong," said Alexander Farrell, the lead study author and an assistant professor in the Energy and Resources Group at the University of California, Berkeley. "We show that the net energy is in fact positive for corn ethanol."
He later added that to "really evaluate this fuel we need to look at other indicators like petroleum and greenhouse gas emission."
Farrell and other scientists say that new technology could dramatically boost the environmental performance of ethanol.
The research is reported tomorrow in the journal Science.
Ethanol is used as a motor fuel additive. It is a renewable energy source, unlike petroleum and coal.
In the United States, ethanol accounts for about 2 percent of total transportation fuel. In Brazil, where ethanol is produced from sugarcane, the fuel powers the majority of the country's road transport.
About 5 percent of the road fuels used in the United States and the European Union are expected to be bio-derived within the next five years. The U.S. Department of Energy aims to replace 30 percent of the liquid petroleum transportation fuel with biofuels by 2025.
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