Saponification pretreatment and solids recirculation as a new anaerobic process for the treatment of slaughterhouse waste

► Novel anaerobic digestion systems for the treatment of fatty waste are proposed. ► Substrate saponification and solids recirculation both benefits the process. ► Saponification enhances emulsification and bioavailability of fatty residues. ► Recirculation minimizes substrate/biomass wash-out and induces microbial adaptation.