Fermentation by the Non-Oxidative Glycolysis Pathway: a Techno-Economic Analysis

Abstract

Lignocellulosic bioethanol is a potentially attractive alternative to both gasoline and conventional cellulosic ethanol as a transportation fuel due to its lower associated carbon emissions. However, in the conventional pathway that converts fermentable sugars into ethanol, carbon is lost in the form of carbon dioxide, limiting both the potential yield of ethanol and producing a greenhouse gas. The James Liao Research Group at the University of California has engineered a pathway, the non-oxidative glycolysis route, in Escherichia Coli that converts sugars into stoichiometric amounts of two carbon metabolites, incurring no carbon losses along the way. This paper is the first to assess and model this novel pathway in a commercial fermentation plant to determine if further research efforts should be invested into moving toward commercializing the process. Using the National Renewable Energy Laboratory’s Ethanol Report (NREL) as a comparison point, two cases are considered – one with a steam reforming unit and one without. A minimum ethanol selling price of $1.90/gallon and $1.95/gallon are associated with the respective processes as compared to $2.15 for NREL’s plant. Both of these modeled processes have markedly lower carbon footprints than petroleum-derived fuels, although in order to compete with gasoline prices a carbon tax of $99/ton would be necessary. Given these results, it is worth further exploring the possibility of scaling the NOG pathway up to a commercial scale in order to offer both cost savings and lower carbon emission compared to comparable lignocellulosic biofuels plants.