Syngas biomethanation in countercurrent flow trickle-bed reactor operated under different temperature conditions

Abstract

Syngas, a mixture of CO, H2, and CO2, is produced by waste carbonaceous feedstocks gasification, which plays an important role in renewable energy production. This study investigated the biomethanation of syngas (45% H2, 30% CO, 25% CO2) in a trickle-bed reactor operated under mesophilic (35 °C), hyper-mesophilic (45 °C), and thermophilic conditions (55 °C). The results revealed that CH4 production increased with increasing temperature. CH4 production under steady-state conditions at the hyper-mesophilic and thermophilic temperatures were comparable; 92.2 ± 1.7 mmol/(Lbed∙d) and 93.9 ± 0.9 mmol/(Lbed∙d), respectively. On the contrary, electron losses in volatile fatty acids were the highest under mesophilic conditions. Additionally, digestate can be dosed as a nutrient addition and as a continuous inoculum source to ensure the optimal syngas biomethanation performance. The hyper-mesophilic conditions strategy illustrates possible energy savings for bioreactor heating with CH4 production comparable to thermophilic conditions, thus saving operating costs.