Biohythane production via single-stage fermentation using gel-entrapped anaerobic microorganisms: Effect of hydraulic retention time

Research of single-stage anaerobic biohythane production is still in an infant stage. A single-stage dark fermentation system using separately-entrapped H₂- and CH₄-producing microbes was operated to produce biohythane at hydraulic retention times (HRTs) of 48, 36, 24, 12 and 6 h. Peak biohythane production was obtained at HRT 12 h with H₂ and CH₄ production rates of 3.16 and 4.25 L/L-d, respectively. At steady-state conditions, H₂ content in biohythane and COD removal efficiency were in ranges of 7.3-84.6 % and 70.4-77.9%, respectively. During the fermentation, the microbial community structure of the entrapped H₂-producing microbes was HRT-independent whereas entrapped CH₄-producing microbes changed at HRTs 12 and 6 h. Caproiciproducens and Methanobacterium were the dominant genera for producing H₂ and CH₄, respectively. The novelty of this work is to develop a single-stage biohythane production system using entrapped anaerobic microbes which requires fewer controls than two-stage systems.