(64b) Biochemical Production of Ethanol and Water-Immiscible Biofuel From Lignocellulosic Biomass: A Comparative Analysis of Environmental and Economic Performance

Despite well-documented shortcomings – low energy density and infrastructure compatibility issues chief among them – ethanol remains the dominant biomass-derived transportation fuel in the U.S. and much of the rest of the world.  As advances in biotechnology have continued at a rapid pace, interest in the biochemical production of so-called “drop-in” fuels has increased among industry, academia, and the government as a way to avoid the shortcomings of ethanol as a fuel molecule as well as to potentially exploit the processing advantages of a water-immiscible fuel to reduce product recovery costs and energy requirements.  In the current study, two separate processes to produce either ethanol or a fatty acid ethyl ester (FAEE) – identical to oil-derived biodiesel – via the fermentation of sugars obtained from lignocellulosic materials are analyzed in terms of economic and environmental metrics.  Simplified process models are introduced and employed to estimate fuel production, net energy consumption, minimum fuel selling price, and water consumption for both processes.  Monte Carlo analyses were carried out to identify the parameters governing process performance, and an analysis of the impact of potential improvements to the FAEE process was performed.  We present the results of our analyses, capturing both the current state of technology development as well as paths to improve the performance of the FAEE process relative to that for producing ethanol.