Impact of mixing grain sorghum with corn on ethanol and coproduct yields

Existing corn ethanol biorefineries produce about 94% of the ethanol capacity in the USA and currently have surplus production capacity. Expanding feedstocks for existing facilities rather than building new dedicated facilities could provide significant benefits and cost savings. Grain sorghum is a feedstock with a similar composition to corn, which could be utilized at significant incorporation levels in existing facilities with minimal or no modifications but it is currently only used minimally. To understand the impact of grain sorghum incorporation better we studied mixed corn and grain sorghum fermentation at the laboratory scale and utilized the data generated to develop technical models for the individual grains and for a 50/50 mixture at 119 million kg per year (40 million gal per year). Detailed processing and economic comparisons were developed to determine the overall impact. The results showed significant feedstock savings ($8 million per year) potential for utilization of sorghum relative to corn. Ethanol production cost was reduced by $0.07 per kg of ethanol using sorghum relative to corn. Other potential impacts on coproduct composition and values were also determined and discussed.