Effect of  H₂:CO ration on theoretical carbon yield of bio-syngas and basic oxygen furnace gas fermentation to chemicals:A thermodynamic and metabolic-based approach

Abstract

Syngas fermentation is an up-and-coming technology that uses acetogenic microorganisms to produce ethanol at the commercial scale. Acetogens can produce many different types of products via their metabolic pathway called the Wood Ljugdahl Pathway (WLP). The WLP can natively produce many different fatty acids and alcohols, and with metabolic engineering, other molecules could be produced through syngas fermentation that are not native to the WLP. In this work isopropanol, 3-hydroxybutyric acid, hexanol, octanol, hexanoic acid, butyric acid and lactic acid were assessed for their feasibility to be produced through syngas fermentation. Two syngas cases were analysed; bio-syngas (H2:CO of 1:1.907) and basic oxygen furnace gas (H2:CO of 1:21.667). The feedstock capacity was fixed at 350 ktons/yr based on its availability. Using thermodynamic values, process reactions from the substrate to the product were found. To verify the metabolic feasibility, ATP yields were calculated based on the respective WLPs from the literature. Sensitivity studies of H2:CO ratios on the carbon yield are carried out to check its effect on the production yields of the product, biomass, and CO2. Sensitivity analysis showed that a higher H2:CO ratio in the feedstock will lead to higher production.</p