Sweet sorghum is a drought-tolerant feedstock with the potential to produce more ethanol per acre than corn.
Sweet sorghum stalks contain up to 75% juice, varying between 12 and 23% in sugar, according to Ismail Dweikat, UNL plant breeder in an article in a UNL Extension publication. "There's enough juice in an acre of sweet sorghum to make 400 to 800 gallons of ethanol. Sorghum juice-derived ethanol is cheaper to produce than corn ethanol because it doesn't require the cooking and enzymes that corn requires for conversion of starch to sugar to fuel grade alcohol."
Current estimates suggest that intensive plant breeding and cultivation research could, over time, increase the sugar content of sorghum juice to a level needed to produce 1,000 gallons of ethanol per acre. "We plan to evaluate the potential of sweet sorghum as an ethanol-producing crop for Nebraska," Dweikat added.
Sweet sorghum is a perennial crop in areas that don't have a winter freeze. Plant breeding efforts continue to improve the cold tolerance of sorghum for growth in the Midwest. In the Corn Belt, sweet sorghum grows 10 to 15 feet tall during a growing season.
"The taller the plant and the thicker the stalk, the more juice the plant will produce," according to Dweikat.
To maximize juice and ethanol production in the Corn Belt, growers need to plant the crop early to mid-April. The grower could then make the first cutting for juice in early July, when the crop starts to flower. A second cutting could be made in October, shortly before frost, yielding enough juice for an additional 100 to 200 gallons of ethanol. Or, if feed were short, the grower could hay or graze the second cutting.
Ethanol is currently processed from sweet sorghum in Texas, Oklahoma and Iowa, as well as India and other parts of the world, Dweikat explained.
"Our belief is its excellent suitability for Nebraska ethanol production has prompted the present proposal. We seek to enhance sweet sorghum performance on marginal lands, and to identify a strategy for improving its ethanol processing potential, two key components for developing this system for production in Nebraska."