Life Cycle Assessments of Ethanol Production via Gas Fermentation: Anticipated Greenhouse Gas Emissions for Cellulosic and Waste Gas Feedstocks

LanzaTech has developed novel microbial bioreactor systems capable of direct gas fermentation to produce ethanol from carbon-containing gases. In this study, a life-cycle assessment method is used to quantify the global warming potential of several scenarios for producing renewable ethanol with the LanzaTech process. Scenarios considering ethanol produced from steel mill waste gases or biomass (corn stover, forest residue, or switchgrass, via gasification) have been considered, using input data from peer-reviewed literature, government reports; life cycle inventory databases, and LanzaTech process engineering estimates. Using standardized life-cycle assessment methods, ethanol produced via LanzaTech fermentation appears to result in greenhouse gas emissions that are at least 60% lower than that of conventional fossil gasoline, with biomass based ethanol achieving close to 90% emission reductions. Results indicate that the LanzaTech gas fermentation technology can be a viable alternative for producing next-generation biofuels that satisfy United States Renewable Fuels Standard policies concerning fuels with a reduced greenhouse gas emissions footprint.