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Dr. Sarah Davis and class
Dr. Sarah Davis with her class in the field.

Mescal in your Mazda?

Agave among possible sources of biofuel, says OHIO researcher

Corinne Colbert
August 14, 2013

The agave plant—a spiky-leaved succulent native to the desert and tropical areas of the Americas—has myriad uses in landscaping, fiber production, and as a food source. An Ohio University researcher believes its sweet sap also could be used to make ethanol.

That's right: The same liquid that gives us tequila could someday power our cars.

Sarah Davis, assistant professor of environmental studies in the Voinovich School of Leadership and Public Affairs, is a leading expert on agave as a potential source of biofuel. She recently presented papers on agave's potential in biofuels at the C4 + CAM Plant Biology 2013 Symposium at the University of Illinois at Urbana-Champaign and at the 16th International Congress on Photosynthesis in St. Louis. She also is writing a chapter on agave for an upcoming book on bioenergy crops.

Most ethanol in the United States is made from corn. The trouble is, much of the American diet also is based on corn in one way or another. When corn is scarce (as in the 2012 drought), less corn is available for animal feed and processed food, driving up prices at the supermarket. Growing corn also takes a lot of fertilizer, which requires a great deal of energy to produce — resulting in further greenhouse gas emissions.

Agave could provide a more sustainable way to produce ethanol, Davis said. In a 2011 paper published in Global Change Biology: Bioenergy, Davis and her co-researchers noted that some agave species could outproduce corn, sorghum, soybeans, and wheat in per-acre yield. It's already proven as a source of alcohol; look at the tequila industry.

Growing agave for fuel production wouldn't necessarily require farmers to turn away from their current uses, either. Until the introduction of synthetic fibers, agave was grown in large areas of Africa and Mexico to make sisal. Many of those plantations—nearly 600,000 acres worldwide—currently lie unused. If they were planted, Davis projects that those farms could yield over 6 billion gallons of ethanol with little or no impact on land use. (For comparison, current U.S.ethanol production is 14.6 billion gallons.)

Best of all, agave grows on land that is either totally unsuited to farming or that requires intensive irrigation to be arable. Such land is found all over the world, including right here in America.

"Some areas are marginal for agriculture because they are dry or don't have high-quality soil," Davis said. "Right now a lot of that land [in the southwest U.S.] is being used to grow crops like cotton and pecans, which use a lot of water."

Davis is currently conducting a study of agave growth in the United States — funded in part by an Ohio University Research Challenge Grant — comparing the water needs and yield potential of agave plots in several locations in the southwestern U.S.

Of course, agave isn't the only potential ethanol source. Closer to home, Davis is growing perennial grasses and woody crops on The Ridges on the Ohio University campus, as well as investigating potential research sites on abandoned mine lands around southeast Ohio. The goal: finding effective, sustainable bioenergy crops that can grow in poor soils in more temperate regions — and still be profitable.

"We know there are likely to be lower yields [in poor soil], but can they still be commercially viable?" she said. "You don't have to maximize yield to be commercially viable."

Davis began her academic career studying the role of forests in fighting climate change. Although she still does forest research, she adopted a focus on bioenergy when she realized that just absorbing excess carbon dioxide wasn't going to be enough.

"A transformation in our energy industry is needed to slow climate change because it is one of the largest sources of carbon dioxide that is emitted to the atmosphere," she said. "I see bioenergy as part of the solution to our most important environmental problems: climate change, energy, and agriculture."