Advanced steam explosion of mixed organic fraction of municipal solid waste and sewage sludge to determine biomethane potentials

The potential of advanced steam explosion-based thermal hydrolysis process (THP) has been extensively explored for municipal sludges, however, the effect of THP on the anaerobic co-digestion of mixed organic fraction of solid waste (OFMSW), and sewage sludge (SS) remains inadequately investigated. Given the limited understanding on the effect of THP and co-digestion compared to mono-digestion, the present study evaluates the effects of THP on the biomethane potential of mixed OFMSW and dewatered SS [80:20 ratio on volatile solids basis, carbon to nitrogen ratio 24, 16 % total solids]. Variable combinations of THP temperature (120, 140, 160, 180°C) and reaction times (30, 60, 90, and 120 min) were tested for substrate solubilization and subsequent biogas generation. Among the studied THP conditions, 140°C- 60 min −3.5 bar pressure pretreatment resulted in the highest biogas and methane yields of 603 and 506 mL/g VSadded,i.e., 4 times higher than control, and maximum volatile solids and soluble chemical oxygen demand (sCOD) removals of 58.7 and 71.3 %, respectively. Above 140°C- 60 min pretreatment, sCOD removal, and methane yield were decreased despite higher sCOD solubilization achieved, owing to the formation of recalcitrant compounds during thermal hydrolysis process. The THP-integrated anaerobic co-digestion of mixed organic fraction of municipal solid waste and sewage sludge could maximize biogas recovery and solids reduction and also provide a significant advantage of compactness over conventional anaerobic digestion. • THP applied on best OFMSW-SS mixing ratio of 80:20 (VS basis) and C/N ratio of 24. • Highest COD solubilization of 40 % was achieved at 160°C temperature regime. • Highest CH 4 yield (506 mL/gVS added ), VS reduction (58.76 %) achieved at 140°C- 60 min THP. • Above 140°C THP pretreatment CH 4 yield decreased by 30–40 %. • Higher COD solubilization > 140°C could not transform to corresponding CH 4 yield.