Continuous co-generation of biohydrogen and biomethane through two-stage anaerobic digestion of hydrothermally pretreated food waste

•Hydrothermal pretreatment (HTP) at 140 °C for 20 min was applied to food waste (FW).•Long-term continuous two-stage H2 + CH4 production of HTP-treated FW was validated.•Higher H2 (3.8%) and CH4 (167.7%) yields were achieved than that using untreated FW.•Microbial analyses revealed less proteolytic bacteria & more versatile methanogens.•A 66.7% increase in treatment capacity was achieved with a balanced energy yield.