Syngas conversion to biofuels and biochemicals: a review of process engineering and mechanisms

Syngas is generated by thermochemical conversion of a wide range of organic wastes, or it is directly produced as an industry off-gas. The syngas components are converted into alcohols and other high-value-added bioproducts by acetogenic bacteria primarily via the Wood–Ljungdahl pathway. The feasibility of the syngas fermentation process to produce ethanol and other biochemicals is affected by many factors, such as microorganisms, fermentation strategies, gas–liquid mass transfer, and reactor types and design. This study offers new perspectives on the fermentation of syngas by focusing on all these factors to achieve commercialization of these value-added products. Moreover, it includes concepts regarding industrial applications by focusing on metabolic engineering and life cycle assessment for evaluating alternative sustainability dimensions and optimizing the production of ethanol and other biochemicals. This review paper lays a foundation for comparative studies that can be carried out to improve the technological, environmental, and socioeconomic aspects of bioethanol production.