Conversion of Distiller's Grains to Renewable Fuels and High Value Protein: Integrated Techno-Economic and Life Cycle Assessment.

Distiller's grains are a byproduct of corn ethanol production and provide an opportunity for increasing the economic viability and sustainability of the overall grain-to-fuels process. Typically, these grains are dried and sold as a ruminant feed adjunct. This study considers utilization of the residuals in a novel supplementary fermentation process to produce two products, enriched protein and fusel alcohols. The value-added proposition and environmental impact of this second fermentation step for distiller's grains are evaluated by considering three different processing scenarios. Techno-economic results show the minimum protein selling price, assuming fusel alcohol products are valued at $0.79 per liter gasoline equivalent, ranges between $1.65-$2.48 kg protein-1 for the different cases. Environmental impacts of the systems were evaluated through life cycle assessment. Results show a baseline emission results of 17 g CO2-eq (MJ fuel)-1 for the fuel product and 10.3 kg CO2-eq kg protein-1 for the protein product. Sensitivity to allocation methods show a dramatic impact with results ranging between -8 to 140 g CO2-eq (MJ fuel)-1 for the fuel product and -0.3 to 6.4 kg CO2-eq kg protein-1 for the protein product. The discussion is focused on the potential impact of the technology on corn ethanol production economics and sustainability.