Improved Cellulosic Biorefinery Economics via a Novel Catalytic Membrane Reactor for Biomass Hydrolysis

Five years ago, Congress set a goal of 500 million gallons of cellulosic ethanol produced in 2012. Although progress has been made, EPA has drastically reduced its 2012 U.S. production projection to only 8.65 million gallons. This huge shortfall is due to many factors, including high capital costs of existing technologies for converting cellulosic biomass feedstocks to sugars, leading to difficulty financing new facilities, and high operating costs of using acid solutions and cellulase enzymes in traditional processing methods. EPA has carefully chosen to set standards that balance the uncertainty of commercial-scale cellulosic ethanol production this year with the goal of promoting growth of the cellulosic biofuels industry. The problem is producing sugars at low enough cost to supplant corn-based sugars. Therefore, there is a clear need for next-generation cellulosic biomass processing technologies that reduce the cost of fermentable sugars production, both in terms of capital costs and operating costs. In Phase I of our STTR project designed to address this problem, we propose to develop and test a novel Catalytic Membrane Reactor (CMR) that simultaneously solubilizes and hydrolyzes biomass and separates hydrolyzed monomeric sugars in an economically efficient manner. Our process is designed to eliminate toxic sulfuric acid and expensive enzymes. The technology exploits our unique ability to tailor the surface of these ceramic membranes in order to impart the desired catalytic properties in a highly controlled manner. The overall goal of this multiphase project is to create a scalable system for the lowest cost production of sugars from cellulosic biomass, thereby overcoming a major hindrance in the manufacture of fuels and other chemicals from renewable biomass feedstocks. By creating an immobilized ionic liquid at the membrane surface, the cellulose is solubilized at the catalyst surface. Since the catalyst is immobilized on the membrane surface, no catalyst recovery step is required. Sugars are removed as they are produced, thus preventing degradation of the sugars and maximizing yields. The hydrolysate detoxification step after pretreatment and prior to fermentation will consequently be eliminated. We will build on extensive preliminary data to further optimize the catalytic membranes. Based on data obtained, an economic analysis of our technology vs. other existing technologies will be conducted in order to prove feasibility of a 40% cost reduction in cellulosic ethanol production. Successful completion of the work proposed here will result in a membrane modification protocol and a bench-scale CMR ready for Phase II scale-up. Symbios and collaborator University of Arkansas believe the requested STTR funding will prove feasibility of using the CMR to improve the economics of cellulosic biorefinery processing by eliminating costly enzymes, reducing biomass pretreatment and hydrolysis process steps from three to one, eliminating consumable acid catalyst use, decreasing sugar degradation, and speeding the process by over an order of magnitude relative to enzymatic hydrolysis.