Methanogenic capacity and robustness of hydrogenotrophic cultures based on closed nutrient recycling via microbial catabolism: Impact of temperature and microbial attachment

•Enrichment of hydrogenotrophic cultures was performed at 37 °C and 55 °C.•Hydrogenotrophic biofilms were allowed to develop on two different support media.•Recovery rates after oxygenation were better at mesophilic temperatures.•Recovery after starvation and oxygenation was complete after 3–5 days.•Biofilms can be formed under intense agitation to help increase methanogenic capacity. A biological methanation system based on nutrient recycling via mixed culture microbial catabolism was investigated at mesophilic (37 °C) and thermophilic (55 °C) temperatures. At mesophilic temperatures, the formation of biofilms on two different types of material was assessed. Results showed that with intense mixing the biofilm reactors presented methanogenic capacities (per working volume) 50% higher than the ones operated with suspended cultures. Gas feeding rates of 200 L/L/d were achieved at a H2/CO2 to CH4 conversion efficiency of above 90% by linking two reactors in series. Furthermore the robustness of the cultures was assessed under a series of inhibitory conditions that simulated possible process interferences at full scale operation. Full recovery after separate intense oxygenation and long starvation periods was observed within 2–5 days.