Project Title: CRITICAL ANALYSIS OF SYNGAS FERMENTATION REACTORS FOR BIOLOGICAL ALCOHOL PRODUCTION
PI: Dr. Hasan Atiyeh (Oklahoma State University, Biosystems and Agricultural Engineering)
Co-PI: Dr. Randy Lewis (Brigham Young University)
Start Date: 12/01/2009 End Date: 11/30/2012
Gasification of cellulosic biomass (e.g. perennial grasses) to produce syngas (primarily carbon monoxide, carbon dioxide and hydrogen) used in fermentation for the production of ethanol and other alcohols is a novel technology. Critical bottlenecks that diminish alcohol productivity, lower syngas conversion efficiency, and inhibit the movement of this process to commercial scale include low cell density and gas-liquid mass transfer limitations. This work will expand upon previous syngas fermentation studies by exploring and critically evaluating the enhancement of mass transfer and associated alcohol productivity with various types and modifications of reactor designs.
In this study, the reactor designs will include a continuous stirred tank reactor (CSTR), a trickle bed reactor (TBR), and a hollow fiber reactor (HFR) system. Unlike traditional reactors in which only one gas is usually critical for the design (such as oxygen), this study is important since carbon monoxide, carbon dioxide, and hydrogen are all vital for the fermentation and each gas has different aqueous solubilities and diffusivities (which affect mass transfer). Clostridium strain P11, a novel bacterium in which the PIs have significant experience, will be used.
Additional strengths of this work include the following:
1) Unlike previous studies which often addressed one species (usually carbon monoxide), this study will address mass transfer associated with carbon monoxide, carbon dioxide, and hydrogen and assess which, if any, of these species may limit the process.
2) This study will focus on multiple comparison parameters including mass transfer rates, conversion efficiencies of both carbon monoxide and hydrogen, and product and cell formation rates.
3) This study will assess unique changes to syngas fermentation reactors and incorporate pH control to provide a more complete comparison between reactors.
Successful completion of this work will provide valuable guidance towards designing large scale bioreactors with increased alcohol productivity and syngas utilization. An improved efficiency in alcohol production will increase the cost effectiveness of the syngas fermentation technology, leading towards a more economically viable cellulosic biofuels process to meet a portion of the biofuels production target of 36 billion gallons per year by 2022.