Syngas fermentation process development for production of biofuels and chemicals: A review

Abstract Syngas is produced by thermochemical conversion, e.g., pyrolysis and gasification, of biomass, animal waste, coal, municipal solid waste and other carbonaceous materials, or directly from CO-rich off-gases from industry, e.g. steel mills. Syngas components (mainly CO, H2 and CO2) are converted to alcohols and other chemicals by acetogenic bacteria through the Wood-Ljungdahl pathway or its derivatives. Syngas fermentation is affected by the acetogen(s), type of reactor, gas composition, medium components, operating parameters, gas-liquid mass transfer and fermentation strategies. These factors affect product distribution, titer, yield, productivity and process feasibility. In this article, syngas fermentation process development with focus on microorganisms, gas composition, medium design, gas-liquid mass transfer fermentation strategies, techno-economic analysis and commercialization efforts are critically reviewed. This review provides new insights in syngas fermentation, which can guide future research towards commercialization of renewable and sustainable biofuels and chemicals.