The Virtues of Switchgrass as an Alternative Fuel

When European settlers emerged from eastern forests onto the prairies, they encountered what at first seemed like an alien and hostile landscape: a veritable sea of tall grasses, with almost no wood for building homes and fences. But before too long, many of them came to see the wide-open spaces and fertile soil as a potential agricultural Garden of Eden—if only a way could be found to plow up the thick sod.

For thousands of years since the most recent ice age, the root systems of the tall grasses had been fingering ever outward, creating the prairie equivalent of root-bound houseplants. The result was some of the richest soils in the world, packed with organic matter and carbon. But the sod was so sticky and dense that even a team of oxen had difficulty dragging a plow through it. It was an exquisite irony: The very thing that made the soils so ready for agriculture—their extraordinary fecundity—actually prevented it.

Until 1837, that is, when John Deere invented a steel plow that could cut through the sod like a hot knife through butter. What followed, of course, was the transformation of a sea of grass into an ocean of corn and soybeans. Today the tallgrass prairie has been reduced to less than 1 percent of its original range, making it one of the rarest ecosystems in the world. And according to David Tilman, an ecologist at the University of Minnesota, farming those soils has caused them to lose up to half of the enriching carbon they once had—to the atmosphere in the form of heat-trapping carbon dioxide.

But now descendants of the sod-busting pioneers may be poised to help at least one native tallgrass species, switchgrass, stage a comeback. And not as feed for livestock but as something far more valuable in this age of expensive oil and global warming: ethanol for use as a renewable “biofuel.”

If all goes well (no trivial if), within five years or so farmers may begin replacing corn and other crops now grown on degraded land, or on land only marginally suitable for agriculture (because of its vulnerability to erosion and other factors), with cultivated fields of switchgrass. If recent research by Tilman and others pays off, we may eventually see farmers replanting not just with switchgrass but with a diverse array of grasses and other plants, re-creating something akin to the native prairies first encountered by the pioneers on their way west. The goal: replacing gasoline with ethanol that would reduce global warming while also helping struggling farm economies, restoring soil fertility, and improving habitat for imperiled grassland birds and other species.

Steve Fransen, a Washington State University (WSU) forage agronomist, is one of the researchers working to make this vision a reality. On a warm July morning beneath southeastern Washington’s Horse Heaven Hills, he stoops beside a lush three-acre plot of head-high switchgrass. Parting the thick growth, he fingers dozens of green blades growing from a single plant. “You can see here why switchgrass produces much more biomass than corn”—a key attribute that could help this tallgrass prairie species supplant corn as a raw material for producing ethanol, a form of biofuel. Fransen is experimenting with ways to cultivate switchgrass 1,000 miles west of its native Midwestern home, with help from a little irrigation. The soils here in the Yakima River valley are drier—so dry, in fact, that it takes two years for the earth up in Horse Heaven to accumulate enough moisture for wheat to be grown successfully. So if switchgrass can make it here, it can make it anywhere.

“We’re making real progress,” Fransen tells me as we walk among the plots at WSU’s Irrigated Agriculture Research and Extension Center in Prosser. “When we harvest this grass in a day or so, I think we’ll get a yield of five tons per acre.” With a second harvest in the fall, the annual yield should be 10 tons per acre. That much biomass translates into more than 1,000 gallons of ethanol—enough fuel to keep a hulking Hummer H2 rolling for 16,000 miles.

But it won’t mean much unless farmers choose to cultivate switchgrass, says Fransen’s collaborator, Hal Collins. A self-described “dirt guy” who refers to soil microbes as “my buddies,” Collins is a microbiologist and soils specialist with the USDA’s Agricultural Research Service. “You can’t just tell farmers to grow this stuff,” he says. “But they will grow it if they decide they can make money and it will stick around. We’re demonstrating in our fields right now that yes, you can grow it, and here’s how you do it.”

Along with its impressive biomass yield, switchgrass embodies other valuable qualities. It can grow in varied environments and requires less fertilizer than row crops like corn (and, in some environments, little or no fertilizer at all). What’s more, because it is a densely rooted perennial, it stabilizes the soil against erosion, preventing runoff into waterways. Best of all, the “cellulosic” ethanol made from switchgrass, along with many other inedible plant fibers, can do much more to reduce global warming by displacing fossil fuels than ethanol made from corn—possibly even cutting 80 percent of U.S. greenhouse-gas emissions from transportation by the year 2050, according to a report by the Natural Resources Defense Council.