Incorporation of Sweet Sorghum Juice into Current Dry-Grind Ethanol Process for Improved Ethanol Yields, Energy Saving, and Water Efficiency

Sweet sorghum is a promising energy crop due to his low fertilizers and water requirements, short grow period, and high biomass yield. However, the challenge for sweet sorghum as a feedstock for ethanol production is its short harvest period and the extreme instability of the juice. At current situation, it is difficult for sweet sorghum based ethanol industry to achieve a year-round production process. One possible way to solve this challenge and to meet the growing demand of bio-renewable ethanol is to incorporate sweet sorghum juice into current dry-grind ethanol process.

In this study, sweet sorghum juice with varying content of grain sorghum flour were liquefied, saccharified, fermented, and distilled to produce ethanol. Ethanol yield from the optimum grain sorghum flour loading with sweet sorghum juice achieved was about 28% higher than that from conventional ethanol process. It was also found that enzymatic hydrolysis with this process could be reduced by 30 minutes. The fermentation performance of sweet sorghum juice with grain flour using raw starch hydrolyzing enzyme was also investigated. The results showed that an ethanol yield was about 21% higher than that from the conventional process. This innovative technology of ethanol production by sweet sorghum juice could improve ethanol yield, save energy, and significantly decrease the use of water in the current dry-grind ethanol process.

Keywords: sweet sorghum, ethanol yield, hydrolyzing time, conversion efficiency.