Enhanced ex-situ biomethanation of hydrogen and carbon dioxide in a trickling filter bed reactor

• Published in: Biochemical engineering journal 2022-02, Vol.179, p.108311, Article 108311
• Main Authors: Thapa, Ajay, Park, Jun-Gyu, Jun, Hang-Bae
• Format: Article
• Language: English
• Subjects: Biomethanation; Digestate; Gas-liquid mass transfer; Hydrogenotrophic methanogen; Trickling filter bed
• ISSN: 1369-703X; 1873-295X
• DOI: 10.1016/j.bej.2021.108311

Ex-situ biomethanation is an emerging technology used for converting carbon dioxide (CO2) and renewable hydrogen (H2) into biomethane. The aim of this study was to investigate the influence of 4:1 and 6:1 stoichiometric H2:CO2 ratio for converting simultaneously exogenous and endogenous CO2 to natural gas quality (biomethane) in the trickling filter bed (TFB) reactor. The coupling of H2 and CO2 produced methane (CH4) content up to 75% and 98% at 4:1 and 6:1 H2:CO2 ratio, respectively. At 6:1 H2:CO2 ratio, the reactor demonstrated its potential to meet the criteria for natural gas quality biomethane and produced CH4 at a rate up to 2.65 L/LR.d with complete H2 utilization. Samples collected from the inoculum, the biofilm formed on the carrier material, and the liquid phase of the reactor showed distinct changes in the microbial community composition. The significant increase in relative abundance of Methanoculleus bourgensis upon H2 injection indicates hydrogenotrophic methanogenesis as the main pathway for enhanced biomethanation. Thus, our study provides a novel approach for simultaneous utilization of CO2 and digestate in a single-stage TFB reactor for achieving higher CH4 content in the output gas. [Display omitted] •Simultaneous biomethanation of exogenous and endogenous CO2 was demonstrated in the TFB reactor.•High CH4 production rate up to 2.65 L/LR.d and maximum 98% CH4 content were achieved.•100% H2 utilization was achieved.•Methanoculleus bourgensis was the most dominant species in liquid and biofilm phases.