Production of advanced biofuels via biomass gasification

Eleni T. Liakakou

Abstract

Statement of the Problem: The development of lignin derived energy products is one way to increase the value of bio-refinery residues. Gasification of (lignin-rich) biorefinery residues, followed by product gas cleaning and anaerobic fermentation, offers a potential to produce higher added-value products such as biofuels and chemicals. MILENA indirect gasification allows complete fuel conversion and produces a high value gas composed of CO, H2 and CO2, as well as compounds such as CH4, C2-C4 gases, benzene, toluene and xylene (BTX), and tars. The separation of the most valuable components of the product gas is a good way to maximize the value from the feedstock via co-production schemes. The product gas, after appropriate cleaning to remove impurities, can be applied in the gas fermentation process. Some anaerobic microorganisms, can be used as a biocatalyst for the microbial conversion of syngas into short-chain organic acids and alcohols (i.e. acetate and ethanol). The ability of these microorganisms to withstand some of the impurities contained in the syngas and their flexibility to use different syngas compositions makes them an attractive alternative to the chemical catalytic processes.  Methodology: A lignin rich feedstock is gasified with steam at 780°C using MILENA indirect gasifier, at TNO. The product gas after removal of the main impurities, consists of CO, H2, CO2, N2, CH4 and traces of other gaseous hydrocarbons, benzene and H2S. The influence of the obtained syngas quality and composition is evaluated in the fermentation process.  Conclusion & Significance: Despite many advantages, the integration of gasification with syngas fermentation is still in an early stage of development, where many questions exist concerning the syngas quality needed in the fermentation process. In this work a first attempt to combine the two processes is presented.