Techno-economic evaluation of a combined biomass gasification-solid oxide fuel cell system for ethanol production via syngas fermentation

Abstract

Bioethanol is regarded as a high-quality and clean liquid fuel with a renewable production process through bioconversion and chemical synthesis technology. Syngas fermentation route has received increasing attention due to mild reaction conditions and the elimination of expensive pretreatment and enzyme. To improve the economy and energy efficiency of the bioethanol production, a novel combined biomass gasification-syngas fermentation-solid oxide fuel cell system is proposed in this work. The techno-economic assessment is performed by the parametric analysis of the gasification and fermentation process. The sensitivity analysis shows that the dual fluidized bed with woodchips has the highest CO and H2 content, and the ethanol yield can be enhanced by improving the substrate conversion rate. A tentative economic assessment is performed with a total production cost of 430.1 €/t ethanol, revealing the economy of the hybrid gasification-syngas fermentation process. Besides, the problem of syngas distribution and fermenter exhaust recycling is further explored by introducing the SOFC system to realize the cascade utilization of energy. The trade-off between the combined system efficiency, total annual cost, and product price is conducted by multi-objective optimization with the technique for order of preference by similarity to ideal solution (TOPSIS) method. The optimized system can reach the system efficiency of 55%, the minimum total annual cost of 19.9 M€, and the total product price of 64.5 M€. The proposed system could demonstrate the feasibility of bioethanol production via biomass syngas fermentation with a high-efficiency and cost-competitive pathway.