ABSTRACT
To upgrade synthesis gas, the low-Btu gas typically undergoes a catalytic shift reaction where carbon monoxide and water are converted to carbon dioxide and hydrogen. Liquid fuels such as alcohols and petrochemicals also may be produced from coal synthesis gas. Microorganisms may be used to convert coal to chemicals either directly or indirectly by their action on synthesis gas. Microbial processes offer certain advantages over chemical conversions. A cheaper source of synthesis gas can be used, since the problem of sulfur poisoning of the catalyst can be eliminated, because sulfur tolerance of microorganisms can often be developed or sulfur can be removed biologically, if necessary. The primary reactions in the biological conversion of synthesis gas to methane are the formation of methane precursors and the biomethanation reactions. This chapter demonstrates the technical feasibility of biological synthesis gas conversion to methane in both mixed and pure culture.
