(758b) Hybrid Thermochemical/Biochemical Gas Fermentation Process for Production of Fuels and Chemicals

The ever increasing demand for renewable feedstock-based fuels and chemicals is driving the interest and rapid development of 2^nd generation biofuel processes worldwide. There is significant research into improving the overall carbon and energy efficiency of biorefineries in order to compete with petroleum derived products in terms of economics and sustainability. A range of 1^st generation renewable thermochemical or biochemical processes face various challenges including high energy demands, high capital costs, poor carbon utilization, or a combination of these factors. Integrated thermochemical/biochemical processes have the potential advantage to overcome these challenges to produce sustainable fuels and chemicals from renewable feedstocks.

The hybrid thermochemical/biochemical LanzaTech process captures various gas streams with renewable resources and converts them into low-carbon fuels and chemicals. The gas feedstock can come from a variety of sources including gaseous waste carbon from industrial processes or from thermochemical processes such as gasification of biomass/MSW or reformed natural gas. The CO, H₂, and/or CO₂ contained in the feed gas are fermented via a biocatalyst to chemicals/fuels such as ethanol, acetic acid, or 2,3-butanediol which also serve as building blocks to longer chained hydrocarbon drop-in fuels. The LanzaTech process offers superior carbon conversion, energy efficiency, and greenhouse gas emission performance compared to conventional and emerging routes to the same products.

The LanzaTech’s integrated thermochemical/biochemical gas fermentation process is described including a comparison to current stand-alone biochemical and thermochemical technologies for the case of producing ethanol from renewable feedstocks, such as biomass. The different routes are compared in terms of product yields, overall carbon capture, thermal efficiencies, and green house gas (GHG) emissions based on overall mass and energy balances of the various processes. A previous analysis comparing gas fermentation to the thermochemical route to ethanol¹ is expanded here to include an assessment of ethanol production via biochemical routes. It is demonstrated that engineering combined thermochemical & biochemical processes can result in benefits that neither process can achieve independently.

[1] Griffin, D.W. and Schultz, M.A. (2012).  Fuel and Chemical Products from Biomass Syngas: A Comparison of Gas Fermentation to Thermochemical Conversion Routes. Environmental Progress & Sustainable Energy. 31, 219-224.