Biogas upgrading with hydrogenotrophic methanogenic biofilms

• Published in: Bioresource technology 2019-09, Vol.287, p.121422-121422, Article 121422
• Main Authors: Maegaard, Karen, Garcia-Robledo, Emilio, Kofoed, Michael V.W., Agneessens, Laura M., de Jonge, Nadieh, Nielsen, Jeppe L., Ottosen, Lars D.M., Nielsen, Lars Peter, Revsbech, Niels Peter
• Format: Article
• Language: English
• Subjects: Biofilm; CO2 limitation; Mass transfer; Methane; Methanogenesis; Microsensor
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.121422

•Hydrogen addition resulted in CO2 limitation and pH increase.•Hydrogenotrophic methanogenesis was highly dependent on CO2 concentration.•A methanogenic biofilm was established on carrier material.•The methanogenic biofilm had a high rate of methanogenesis.•The methanogenic biofilm was enriched in the genus Methanoculleus. Hydrogen produced from periodic excess of electrical energy may be added to biogas reactors where it is converted to CH4 that can be utilized in the existing energy grid. The major challenge with this technology is gas-to-liquid mass transfer limitation. The microbial conversions in reactors designed for hydrogenotrophic methanogenesis were studied with microsensors for H2, pH, and CO2. The H2 consumption potential was dependent on the CO2 concentration, but could partially recover after CO2 depletion. Reactors with 3-dimensional biofilm carrier material and a large gas headspace allowed for a methanogenic biofilm in direct contact with the gas phase. A high density of Methanoculleus sp. in the biofilm mediated a high rate of CH4 production, and it was calculated that a reactor filled with 75% carrier material could mediate a biogas upgrading from 50 to 95% CH4 within 24 h when an equivalent amount of H2 was added.