Life cycle assessment and techno-economic analysis of a novel closed loop corn ethanol biorefinery

Abstract

Corn-based ethanol provides an opportunity to lower life cycle impacts in comparison to fossil fuels. A novel biorefinery design is proposed, which avoids energy intensive treatment of by-products and aims at further reducing the environmental impacts of corn-ethanol production. In this biorefinery, an anaerobic digester replaces energy-intensive evaporators to treat thin stillage, a by-product with high COD, followed by struvite recovery, aerobic treatment and utilization of the digestate for the cultivation of algae. The treated digestate and microalgae is then recycled to the front-end of the plant to reduce corn and water consumption. Life cycle assessment and techno-economic analysis were conducted based on primary industry data to compare the environmental footprint and economic performance of the novel plant design compared to a conventional baseline. Reductions in energy use and increased production of salable co-products led to decreases in most relevant environmental impact categories for the novel biorefinery, including global warming, land use, fossil resource use, acidification, and water use. The economic analysis indicated that the revenue decreased by about $0.10/gal of ethanol in the novel biorefinery when capital, operating and material costs were considered.