SAN FRANCISCO, CALIFORNIA--Boosting the use of ethanol-based fuels in the United States runs into a huge technical limitation: There's not enough arable land available to grow the necessary amount of corn--the current crop of choice. But researchers here at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW) say that hitch could be overcome by focusing on new sources of ethanol derived from the whole body of plants, not just the grain.
In his State of the Union address last month, President George W. Bush, called for the country to increase its ethanol production to 35 billion gallons per year by 2017--or nearly five times the 7.5-billion-gallon target for 2012 that Congress established in 2005. Raising biofuels consumption would cut U.S. dependence on foreign oil and help curb carbon dioxide emissions, because the plants from which the fuels are derived absorb atmospheric CO2 during photosynthesis. Ethanol is now produced domestically from corn grown on 54,000 square kilometers of farmland, or an area a little larger than West Virginia. Reaching the president's goal would require another 334,000 square kilometers, or the combined size of Kansas and Iowa.
Biologist Chris Somerville of Stanford University in California thinks he has a better idea. Instead of increasing the acreage devoted to corn, the ethanol industry should switch to Miscanthus, a perennial grass native to subtropical Africa and Asia that is currently only an ornamental plant in the United States. "It uses less water per gram of biomass produced than other plants," Somerville says. He also told attendees here that Miscanthus can grow on land not currently set aside for agricultural crops, so it would not increase pressure on corn prices.
An ethanol industry based on Miscanthus isn't yet economical. Even with corn, "half the cost of ethanol [today] is purchasing the feedstock," says molecular geneticist Gerald Tuskan of Oak Ridge National Laboratory in Tennessee. He says the current $50 per ton that ethanol manufacturers are paying for corn could be reduced to $32 or so for Miscanthus if that fuel could be grown on a scale to become competitive as an ethanol source.
"This [prospect of alternative ethanol sources] is beginning to capture the imagination of scientists," says physicist and Nobel Laureate Steven Chu of Lawrence Berkeley National Laboratory in California. Not that the effort will be easy, he says. The process of converting biomass to ethanol is expensive, Chu says, because it requires breaking down the lignin, the tough and woody part of plant cells, and treating the remaining product with enzymes to produce the sugars that can be fermented into ethanol. Corn-derived ethanol currently costs $2 to $3 per gallon to produce. Chu's laboratory has begun an effort called the Helios Project, which aims to replace oil with biomass as the country's primary source of transportation fuels.
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