Green hythane production from food waste: Integration of dark-fermentation and methanogenic process towards biogas up-gradation

This study presents an integration of acidogenesis (dark-fermentation) and methanogenesis for green hythane/biohythane production from food waste in two stages (S–I and S-II) and phases (P–I and P-II) of operational variations. The regulatory influence of biocatalyst and redox environment on anaerobic fermentation was evaluated  through a rapid protocol in the context of biogas up-gradation with reference to bio-hydrogen (bio-H₂), biomethane (CH₄), bio-hythane (H₂+CH₄) and their composition (H₂/(H₂+CH₄)) as major markers. Bioreactors with two different parent cultures (heat-shock pretreated and untreated) were operated at pH 6 and 7 in two phases to overcome the impediment of single-phase operation aiming for maximum energy recovery from the untreated substrate of P–I. Integration of S–I with S-II was beneficial to achieve 1.22 times higher cumulative bio-hythane production (4.25 L) compared to S–I (3.47 L) condition alone. The bio-hythane composition mimics the H₂ enriched CNG (H-CNG) and showed the potential to be implemented for biogas up-gradation as a tool.