In-situ control of biohythane production in electro-anaerobic digestion

Biohythane, consisting of methane and hydrogen, is a promising clean energy carrier with enhanced combustion properties and reduced greenhouse gas (GHG) emissions. Herein, electro-anaerobic digestion (EAD) was employed as a novel approach for regulating biohythane production. The results revealed that the applied potential significantly influenced biogas production rates and composition. The reactor under 0.1 V (EAD +0.1V ) demonstrated the highest methane yield and the shortest lag period with a final biohythane of 60 % methane and 13 % hydrogen. Meanwhile, improved consumption of volatile fatty acid (VFA) was observed, resulting in a relatively neutral pH. Microbial community analysis showed a substantial increase in hydrogenotrophic methanogens (85 %) and a reduction in acetoclastic methanogens (14 %). The +0.1 V electrode likely acted as an electron sink, enabling electroactive biofilm (EAB) to consume acetate and relieve fermentation bottlenecks and thus sustaining biohythane production. While the exact electron transfer pathway remains uncertain, the present results highlight the potential mechanistic role of electrode-driven acetate consumption in enabling metabolic redirection. Those findings would encourage future efforts to further understand the electron transfer pathways toward the design of scalable EAD systems. • An in-situ single-stage biohythane technology was developed. • Varying applied potentials significantly influence biogas composition, with EAD +0.1V achieving a 13% hydrogen accumulation. • EAD +0.1V shows the increase in hydrogenotrophic methanogens (relative abundance: 85%). • Obvious oxidation current and VFA consumption were observed in EAD_+0.1V group.