Switchgrass may offer one of the best options for cellulosic ethanol production for Southwest producers, but, as with any crop, risk and challenges come with the enterprise.
While it is a hardy, drought-resistant plant, it still requires some water to be productive, says Joe Bouton, senior vice president and director of the Forage Improvement Division at The Samuel Roberts Noble Foundation in Ardmore, Oklahoma.
“Switchgrass production will not be optimum in low rainfall areas,” he says. “Many talk about switchgrass producing 6 to 8 tons per acre with a goal of 10 to 15 tons per acre; however, this kind of production will depend on the soil and the amount of water the crop receives. The key is to understand the natural capabilities of the land and weather in the area.”
Bouton says determining an exact place where switchgrass will thrive could be challenging but he says Eastern Oklahoma, where annual rainfall typically averages 35 inches or more is a good bet. “From 25 inches to 35 inches should provide an opportunity for success. Anything below 20 inches of annual rainfall will not prevent establishment of the crop — let's remember that switchgrass is native to this region — but growers cannot expect maximum yield in such conditions.”
Irrigation is an “interesting option,” Bouton says. “From our experiences, growers who have irrigation equipment would be able to irrigate with less water (than with other row crops).”
He says switchgrass offers advantages over annual crop enterprises. “Stands are long-lived in a native state, but in cultivated conditions the U.S. Department of Energy is estimating stand-life at approximately 10 years.”
He says a stand at Auburn University in Alabama has persisted for 15 years.
“Switchgrass will need fewer cuts than alfalfa. Two cuts may be possible, one in early summer and another in the fall should be enough. Many are planning for switchgrass to be a one-cut system. Switchgrass producers will be looking for quantity — tons per acre — not necessarily the same quality that we look for in grazing or haying forages. Unlike alfalfa, annual switchgrass yields will be almost the same with one cut as with two, and it's cheaper to cut it just one time.”
Bouton says producers should not cut switchgrass too often. “With three or more cuts, the stand could suffer. It likes to grow and store energy in roots and rhizomes.”
Rather than “traditional” harvests, Noble Foundation researchers are looking at including switchgrass in a grazing system, where grazing cattle would provide the crops' first “cutting” each spring. “After the cattle are pulled off the crop in the spring, we would focus on producing sufficient tonnage to deliver to a biorefinery — we are looking at different ways for farmers and ranchers to benefit from switchgrass,” Bouton says.
He says switchgrass is a good carbon dioxide trap. “Growers could get double benefits. The plant's expansive root system serves not only to stabilize the soil, preventing erosion, but also to return much-needed carbon to the soil to enhance productivity. It is also possible that the grower could sell “carbon credits” for the switchgrass stand to carbon dioxide emitting companies if this option becomes available in the marketplace.”
Regular hay harvesting equipment probably will work for switchgrass, but Bouton says the industry needs to do significant research on harvesting, storing and transporting switchgrass. “We may find that we need different equipment to harvest biomass for renewable fuels,” he says. “We probably have room to maneuver early on and initially growers likely will use what they have available.”
He says a burgeoning switchgrass industry will provide opportunities for forage equipment manufacturers.
Because so many questions exist regarding establishment and management of cultivated switchgrass, Bouton says agronomists at the Noble Foundation are working on a producers' handbook. “This will be a learning experience and our agricultural division will work with farmer-cooperators to demonstrate how switchgrass performs and what we have learned in our research.”
As part of this research, he says Noble's agronomists will continue to look at fertility demands to achieve optimum yield goals and the related economics for achieving these goals.