Chapter 2: Biological Conversion of Syngas into Ethanol

This chapter describes the production of ethanol via fermentation of syngas. This ethanol production route shares some of its process lay-out with the Fischer–Tropsch route, but it has the advantage that it can be applied with less stringent syngas cleaning and on a smaller scale (30 kton per year) with evident logistic advantages. Desk research and lab experiments have resulted in considerable insight and knowledge about the metabolism and the cultivation of C. ljungdahlii for the conversion of syngas to ethanol. Experimental efforts have shown that syngas can be converted to ethanol and acetate (proof of principle). The alcohol concentrations in the end product as well as energy efficient ethanol purification are crucial for the feasibility of the whole process. While this chapter focuses on experimental gas fermentation work and process options based on wood gasification, it additionally describes the demonstration projects by companies like Synata, Lanzatech and Ineos Bio.