Direct inoculation of a biotrickling filter for hydrogenotrophic methanogenesis

Hydrogenotrophic biomethanation in a biotrickling filter has been reported to be a proven technology for biological biogas upgrading in recent studies. However, the preparation of enriched hydrogenotrophic methanogens in a separate reactor prior to biomethanation in a trickled bed is a lengthy procedure and therefore hard to apply on an industrial scale. This study explored the direct inoculation of anaerobic biogas digestate for simultaneous enrichment of hydrogenotrophic methanogens and biofilm immobilisation in a trickled bed system. The direct inoculation and formation of hydrogenotrophic biofilm was successful and resulted in a stable H ₂ loading rate of 11 Nm _{H 2} ³m _R ^-3d ^-1, with the highest specific methane productivity recorded at 3.03 Nm ³m _R ^-3d ^-1 and a purity of 98% CH ₄ in thermophilic conditions. The DNA analysis confirmed that hydrogenotrophic methanogens dominated the archaeal consortia.