Biohythane production via single-stage anaerobic fermentation using entrapped hydrogenic and methanogenic bacteria

This study demonstrates the continuous biohythane production in a single-stage anaerobic digester using a biomass mixture of separately entrapped hydrogenic and methanogenic bacteria (H₂- and CH₄-producing bacteria, respectively). The entrapped hydrogenic/methanogenic bacteria biomass ratios of 1/4, 2/3, 3/2 and 4/1 were tested and shown to have a great effect on the single-stage biohythane production performance. At steady-states, the cultivations had biohythane production rates in the range of 381-480 mL/L-d, with H₂ content in biohythane (HCH) varying from 1% to 75% (v/v) and chemical oxygen demand removal efficiencies (TCOD_re) of 57.6-81.9%. Biomass ratio 2/3 (weight ratio 1/1.5) resulted in peak biohythane production with H₂ and CH₄ production rates being 64.6 and 395 mL/L-d, respectively, HCH 15% and TCOD_re 74.4%. The novelty of this work is to show the potential of producing biohythane from an innovative single-stage dark fermentation system using entrapped hydrogenic and methanogenic bacteria.