Grain sorghum is a viable feedstock for ethanol production
- 760 Downloads
Sorghum is a major cereal crop in the USA. However, sorghum has been underutilized as a renewable feedstock for bioenergy. The goal of this research was to improve the bioconversion efficiency for biofuels and biobased products from processed sorghum. The main focus was to understand the relationship among “genetics–structure–function–conversion” and the key factors impacting ethanol production, as well as to develop an energy life cycle analysis model (ELCAM) to quantify and prioritize the saving potential from factors identified in this research. Genetic lines with extremely high and low ethanol fermentation efficiency and some specific attributes that may be manipulated to improve the bioconversion rate of sorghum were identified. In general, ethanol yield increased as starch content increased. However, no linear relationship between starch content and fermentation efficiency was found. Key factors affecting the ethanol fermentation efficiency of sorghum include protein digestibility, level of extractable proteins, protein and starch interaction, mash viscosity, amount of phenolic compounds, ratio of amylose to amylopectin, and formation of amylose-lipid complexes in the mash. A platform ELCAM with a base case showed a positive net energy value (NEV) = 25,500 Btu/gal EtOH. ELCAM cases were used to identify factors that most impact sorghum use. For example, a yield increase of 40 bu/ac resulted in NEV increasing from 7 million to 12 million Btu/ac. An 8% increase in starch provided an incremental 1.2 million Btu/ac.
KeywordsGrain composition Sorghum Bioconversion Bioprocess Ethanol Fermentation efficiency Energy life-cycle analysis
This project was supported by the National Research Initiative of the USDA Cooperative State Research, Education, and Extension Service, grant number 2004-35504-14808. The authors would like to thank Novozymes Inc. for providing Liquozyme SC DS and Spirizyme Fuel, and Fermentis of S.I. Lesaffre for the active dry yeast, Ethanol Red, used in this research.
- 1.Renewable Fuels Association (RFA) (2007) Building new horizons: Ethanol industry outlook 2007. Available at: http://www.ethanolrfa.org/media/pdf/outlook_2007.pdf
- 15.Yang P, Seib PA (1995) Low-input wet-milling of grain sorghum for readily accessible starch and animal feed. Cereal Chem 72:498–503Google Scholar
- 16.Yang P, Seib PA (1996) Wet-milling of grain sorghum using a short steeping period. Cereal Chem 73:751–755Google Scholar
- 21.American Association of Cereal Chemists (2000) Approved methods of the AACC, methods 46–30: crude protein—combustion method, 10th edn, AACC, St. PaulGoogle Scholar
- 22.American Association of Cereal Chemists (2000) Approved methods of the AACC, methods 76–13: total starch assay procedure (Megazyme Amyloglucosidase/alpha-Amylase Method), 10th edn. AACC, St. PaulGoogle Scholar