Voice of America
December 21, 2006
In his State of the Union address early this year, President Bush urged a speed-up of research into energy sources other than fossil fuels. And he mentioned one that many Americans had never heard of: switchgrass. It's a hardy wild plant that thrives on America's Great Plains, from Texas north to Canada.
Millions of Americans are already driving cars powered principally by ethanol made from corn, or biodiesel made from soybeans. But switchgrass, a perennial with thick, hard stems that grows up to three meters tall, may have more long-term potential as a fuel source. Charles Taliaferro, an Oklahoma State University emeritus professor of agriculture, has helped breed high-yielding varieties of the tenacious grass. "It produces seeds that are valued by wildlife, particularly birds," he says. "So it's environmentally friendly. It's more easily established than some of the other major perennial grasses. It grows on non-crop soils where corn and other row crops cannot be produced. It has relatively high biomass production capability with minimal fertilizer and water."
The corn from which most ethanol is made today must be planted annually on farmland with rich soil, and is in constant demand as a food source. Meanwhile, not even cattle go out of their way to munch on brittle switchgrass. Whatever its source, that ethanol is a bit less powerful than gasoline, which is one reason why a bit of gasoline is mixed into most ethanol formulas.
Danielle Bellmer, an associate professor at Oklahoma State University's School of Biosystems and Agricultural Engineering, says sugar can be extracted from cellulose in the switchgrass plant. She says that is turned into fuel, though the process is by no means easy. "Years of research have gone into hydrolysis, as it's called. Specific enzymes are required to break the cellulose down into sugar."
Creating protein-based enzymes that can break down coarse grasses costs a lot more than coaxing sugar out of the starch in corn or soybeans. But the cost has been steadily dropping, and the time may be near when it's commercially viable to turn switchgrass into fuel. Says Professor Bellmer, "You just have to harvest the grass, chop it up, put it into a fermenter where there are enzymes, allow the enzymes to work and break down the cellulose into sugar, and then add yeast, which will convert the sugar into ethanol."
The latest research at Oklahoma State University includes work on a different approach that uses switchgrass to create what's called "grassahol." The entire plant, diced into bits, is burned at high temperatures in a device called a "gasifier." This produces carbon monoxide, carbon dioxide, and hydrogen gases that are "bubbled" through a bioreactor, where micro-organisms convert them into ethanol. As an engine fuel, it's about 85 percent as efficient as gasoline.
"In exchange for the lower fuel mileage, you have to consider benefits to the environment and to our economic system in America," Danielle Bellmer points out. "So we're supporting ourselves if we're buying our own fuel, as opposed to supporting countries around the world. And it's a sustainable fuel."
Millions of hectares of switchgrass once swayed and whistled in the wind across the North American heartland. Over two centuries, farmers plowed much of it under to plant edible corn, wheat, and soybeans. But if today's successful research leads to actual grassahol production, wide swaths of the great tallgrass prairie could make a triumphant return.