Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/5/2008
Publication Date: 1/23/2008
Citation: Wang, D., Bean, S., Mcclaren, J., Seib, P., Madl, R., Tuinstra, M., Shi, Y., Lenz, M., Wu, X., Zhao, R. 2008. Grain Sorghum is a Viable Feedstock for Ethanol Production. Journal of Industrial Microbiology and Biotechnology. 35:313-320. Interpretive Summary: Although we generally know that ethanol yield from sorghum is comparable to that from corn, many factors might affect the ethanol yield from sorghum, the quality of distiller’s dried grain, and eventually the profit margin of an ethanol plant. After several years of research on ethanol production from grain sorghum, our research group found some important factors that significantly impact the performance of grain sorghum for ethanol production. In addition, an energy life cycle analysis model for grain sorghum has been developed, based on our findings. We believe that both sorghum growers and ethanol plant managers will benefit from some basic knowledge of the most important factors impacting ethanol yield and quality.
Technical Abstract: 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 bio-based 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.