As with stover, much needs to be learned about switchgrass, including yield, agronomic needs of the crop, agronomic practices, pests and diseases, as well as its economics, storage and transport.
With University of Tennessee Agricultural Extension assistance, farmers in the state's Henry and Benton Counties are growing close to 100 acres of switchgrass this year. The experiment is expected to answer some key agronomic questions.
The cost of growing switchgrass will vary by state or region, says Burton English, agricultural economist, University of Tennessee. He notes that, in Tennessee, yields of 8 to 10 tons/acre would not be uncommon, whereas in Iowa, for example, switchgrass might yield just 5 tons/acre. This warm-season grass performs better in warmer climates, English explains.
The University of Tennessee also will learn more about switchgrass now that the state legislature has approved funding for a $41 million pilot cellulosic ethanol plant. Under the Tennessee Biofuel Initiative, the university plans to build a pilot biorefinery in eastern Tennessee that will produce 5 million gallons of cellulosic ethanol per year when it becomes operational. Both switchgrass and wood chips will be used as feedstocks.
Farmers will need to see economic benefits to raising this perennial crop before they will grow it, says NRDC's Greene, adding that supplying switchgrass biomass for a small heating project would be one way to gain familiarity with the crop.
Growers will want to understand the logistics of storing and transporting the biomass. It would not be practical for most farmers to store the biomass, waiting for a cellulosic ethanol plant to take delivery, Greene adds.
“The biggest drawback to any of the cellulosic approaches is the volume of the material needed,” Duffy says. “Storage and transportation of switchgrass adds considerably to the cost. This issue will have to be resolved or new technologies will need to come along that will significantly improve the conversion before we see really widespread use of cellulose.”
The volume problem will affect the amount of land needed for storage and the amount of truck traffic on the roads. It raises the issue of who will own the material throughout the year, Duffy says. “A big issue is the type of storage,” he explains. “In studies, ISU researchers found that total enclosure for switchgrass was the most expensive. But it resulted in the least dry matter loss.”