The schematic layout of the BTF reactor and the connections to ancillary equipment are shown in Fig- 1. The reactor body was built using a clear polyvinyl chloride pipe. The inner diameter was 5.4 cm, packed length was 22 cm, working volume (V r ) was 503.8 mL, and media sump volume (V s ) was 400 mL. The reactor had a heating jacket that was made by wrapping a silicon tube (6.4 mm inner diameter) around the whole length of the reactor. On top of the heating jacket, a layer of thermal foam insulation was wrapped. Water at 57 °C was circulated from a water bath in the silicon tube to maintain thermophilic conditions in the reactor. The reactor was packed with finned Raschig rings made of polyethylene and had the size of 7 mm x 10 mm (PE08, Tongxiang Small Boss Special Plastic Products Ltd. (). One piece of the packing materials had a vendor quoted surface area of 3500 m 2 /m 3 . The bed void fraction of the packing material was measured to be 76%. The feed gas used was a mix of N 2 , CO 2 , and H 2 . The inlet flowrate of these gas components was controlled using thermal conductivity-based mass flow controllers (EL-FLOW Select series, Bronkhorst ® ).