Biogas production from sewage scum through anaerobic co‑digestion: the effect of organic fraction of municipal solid waste and landfill leachate blend addition Adewale Aromolaran, Majid Sartaj, Rania Mona Zeid Alqaralleh Biomass Conversion and Biorefinery, Sep. 2021 Abstract: Anaerobic digestion is a promising technology for biogas recovery from lipid-based wastes. Although other types of such wastes have been investigated, sewage scum (SS) produced from primary and secondary settling tanks of wastewater treat ment plants is yet to be fully explored as an alternative source of biogas. To this end, anaerobic co-digestion and blending were adopted as strategies to enhance biogas production from SS using biochemical methane potential (BMP) assay while three kinetic models were used for interpretation. This work examines the synergistic effect of percentage sewage scum loading: 10%, 20%, and 40% (volatile solids basis) during mesophilic co-digestion with various organic substrates, viz., organic fraction of municipal solid waste (OFMSW), old landfill leachate (OL), new landfill leachate (NL), and a leachate blend (LB) prepared from 67% old leachate and 33% new leachate. After 27 days, results showed that the highest level of improvement in the net cumulative methane yield (CMY) was observed in SS:OL ratio of 40:60 where the yield increased by 67% (105.2 ± 33.1 mL gVS−1) when compared with OL alone (35 ± 0.3 mL gVS−1). This increase was linked to positive synergism and improved anaerobic biodegradability of the mixtures. In addition, reactors containing leachate blends showed a higher methane recovery (338.1 ± 30.6 mL gVS−1) by 5.38-fold over other sets due to the associated effect of leachate blending. Furthermore, the modified Gompertz model achieved a better fit with up to an R2 value of 0.999 while co-digestion substantially reduced the lag time by 2.5-fold (2.1 day) compared with mono-digestion. Results from this study suggests that existing facilities can incorporate either SS addition or leachate blending as environ mentally friendly strategies to improve biogas production during waste treatment.