Carrier Material and Microbial Selection for Enhanced Methane Production in Ex-Situ Biomethanation

Abstract Choosing the appropriate carrier material for ex-situ biomethanation is a critical factor to consider when developing biogas upgrading technologies. The chosen material for biomethanation in a biotrickling filter reactor functions as a substrate that immobilises microorganisms, which act as catalysts in the reaction for producing biomethane. This study conducted experiments on waste-derived materials, including glass foam and vulcanised wood ash material, in addition to polyurethane foam and expanded clay pellets. The manometric test measured the rate of CH4 generation by quantifying pressure fluctuations. The results were confirmed by analysing final product gas samples using gas chromatography. To enhance the biomethane concentration in the end product, a strain of Methanobacterium alcaliphilum was evaluated alongside biogas digestate as the inoculum. This Methanobacterium alcaliphilum strain is a methanogen that utilises hydrogen and can thrive in a high pH environment. Thus, it has the potential to demonstrate improved biomethane production outcomes when a vulcanised wood ash material is used as the carrier material. Glass foam demonstrated excellent methane yields (up to 84 %), while vulcanized wood ash material was unsuitable due to its alkaline properties and inhibitory effects on microbial growth. Biogas digestate outperformed Methanobacterium alcaliphilum monoculture as inoculum, highlighting the need for further research on microbial community optimization, especially in larger reactor systems. These findings contribute to advancing sustainable biomethanation technologies and promoting circular economy principles.