Researchers from the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) \ have found that three UF/IFAS-developed sorghum varieties could produce up to 10,500 liters of ethanol per hectare (about 1,100 gallons US per acre). Sorghum is the fifth-largest cereal crop in the world and the third-largest in the United States, according to the US Department of Agriculture. In 2014, the US was the largest producer of sorghum in the world.
UF/IFAS scientists like sorghum because it can be cultivated twice a year in Florida, requires little fertilizer, uses water efficiently and can be drought resistant. For a newly published study in the journal Industrial Crops & Products, UF/IFAS scientists wanted to see if they could use the three sweet sorghum cultivars as raw material for bioethanol production.
Eulogio Castro, a former visiting assistant professor at UF/IFAS and lead author of the study, worked with UF/IFAS researchers to grow the sorghum cultivars at the UF/IFAS Plant Science Research and Education Unit in Citra, Florida. Castro is now a researcher at the University of Jaén in Spain.
Once researchers grew and harvested the sorghum, they took it to the UF/IFAS Stan Mayfield Biorefinery Pilot Plant in Perry, Florida. There, they processed the crop and collected the sugar-rich juice from the stems, which could be directly fermented to fuel ethanol. The bagasse was processed to generate an additional source of fermentable sugars that could also be converted to ethanol.
Results show a sugar concentration in the juice ranging from 140 to 170g/L, which were almost completely converted into ethanol by yeast. Concerning the L+SScF, the final ethanol concentration produced increased with enzyme dosage, with little difference among all three sorghum cultivars, reaching up to 27.5g EtOH/L at enzyme concentrations of 11.5FPU/gDW. Considering the ethanol produced from juice and from Sweet Sorghum Bagasse (SSB), there is a potential of producing up to 10,600L of ethanol per hectare, improving on the values reported for corn ethanol.—Castro et al.
Based on the yields obtained from field tests, it would be possible to generate between 5000 to more than 6300 L EtOH/ha for the sorghum cultivars, considering only the sugars produced from the juice. In 2014, corn ethanol averaged some 4200 L/ha.
Eulogio Castro, Ismael U. Nieves, Vanessa Rondón, William J. Sagues, Marco T. Fernández-Sandoval, Lorraine P. Yomano, Sean W. York, John Erickson, Wilfred Vermerris (2017) “Potential for ethanol production from different sorghum cultivars,” Industrial Crops and Products, Volume 109, Pages 367-373 doi: 10.1016/j.indcrop.2017.08.050