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Evaluation of Waxy Grain Sorghum for Ethanol Production¹

¹Contribution number 11-327-J from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. ²Department of Biological and Agricultural Engineering, Kansas State University, Manhattan, KS 66506. ³Present address: C. W. Brabender Instrument, Inc., 50 E. Wesley Street, S. Hackensack, NJ 07606. ⁴U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS), Center for Grain and Animal Health, Manhattan, KS 66502. ⁵USDA-ARS, Grain, Forage, and Bioenergy Research Unit, Lincoln, NE 68583. Names are necessary to report factually on available data; however, USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ⁶Department of Agronomy, Kansas State University, Manhattan, KS 66506. ⁷Corresponding author. Phone: (785) 532-2919. Fax: (785) 532-5825. E-mail: dwang@ksu.edu

The objective of this research was to investigate the fermentation performance of waxy grain sorghum for ethanol production. Twenty-five waxy grain sorghum varieties were evaluated with a laboratory dry-grind procedure. Total starch and amylose contents were measured following colorimetric procedures. Total starch and amylose contents ranged from 65.4 to 76.3% and from 5.5 to 7.3%, respectively. Fermentation efficiencies were in the range of 86.0–92.2%, corresponding to ethanol yields of 2.61–3.03 gallons/bushel. The advantages of using waxy sorghums for ethanol production include easier gelatinization and low viscosity during liquefaction, higher starch and protein digestibility, higher free amino nitrogen (FAN) content, and shorter fermentation times. The results showed a strong linear relationship between FAN content and fermentation rate. Fermentation rate increased as FAN content increased, especially during the first 30 hr of fermentation (R² = 0.90). Total starch content in distillers dried grains with solubles (DDGS) was less than 1% for all waxy varieties.