Comparison of in-situ and ex-situ electrolytic H2 supply for microbial methane production from CO2

• Published in: Bioresource technology 2023-11, Vol.388, p.129728-129728, Article 129728
• Main Authors: Shang, Gaoyuan, Yu, Jinpeng, Cai, Wenfang, Cui, Kai, Shen, Xiaoying, Jin, Pengkang, Guo, Kun
• Format: Article
• Language: English
• Subjects: Gas fermentation; Methanogenesis; Microbial CO2 fixation; Microbial electrosynthesis; Power to methane
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2023.129728

[Display omitted] •A CSTR equipped with internal and external electrolyzers was constructed.•In-situ and ex-situ electrolytic H2 supply for methanogenesis was compared.•In-situ electrolysis resulted in higher H2 dissolved concentration and KLa.•In-situ H2 supply enabled higher productivity, CE, and energy efficiency. Both in-situ and ex-situ electrolytic H2 supply have been used for biomethane production from CO2. However, the pros and cons of them have not been systematically compared. The present study makes this comparison using a 20 L continuous stirred-tank reactor equipped with external and internal electrolyzers. Compared to the ex-situ H2 supply, the in-situ electrolytic H2 bubbles were one order of magnitude smaller, which resulted in improved H2 mass transfer and biomass growth. Consequently, the methane production rate and the coulombic efficiency of the in-situ H2 supply (0.51 L·L-1·d-1, 96%) were higher than those of the ex-situ H2 supply (0.30 L·L-1·d-1, 56%). However, due to high internal resistance, the energy consumption for the in-situ electrolysis was 2.54 times higher than the ex-situ electrolysis. Therefore, the in-situ electrolytic H2 supply appears to be more promising, but reducing energy consumption is the key to the success of this technology.