Ex-situ biomethanation in a biotrickling filter is being developed as a robust technology for the conversion of CO2 to CH4 using H2 generated from renewable power. The technology uses hydrogenotrophic methanogens in a biofilm as the catalyst and the optimum supply of nutrients in the biofilm is imperative for stable and long-term operation. In this study, essential nutrients for the methanogens in the biotrickling filter were highlighted along with a systemic investigation of the nutrient supply methods. The results showed that ammonium and iron were the critical nutrients with a minimum required concentration of 0.3 g/L and 1.5 mg/L, respectively. Furthermore, thoroughly wetting the biofilm with nutrient media, either using flooding or flushing, was needed to maintain an active biofilm; although, these methods temporarily reduce the conversion for a duration of 18–24 h due to the interpreted formation of a thicker water film.
- Hydrogenotrophic methanogens