Anaerobic co-digestion of various organic wastes: Kinetic modeling and synergistic impact evaluation

Anaerobic mono- and co-digestion of coffee pulp (CP), cattle manure (CM), food waste (FW) and dewatered sewage sludge (DSS), were assessed using biochemical methane potential tests. The effects of two different inocula, anaerobically digested cattle manure (ADCM) and anaerobically digested waste activated sludge (ADWAS), and five different co-feedstock ratios for CP:CM and FW:DSS (1:0, 4:1, 2:1, 4:3, and 0:1) on specific methane yields were also evaluated. Mono-digestions of both CP and FW yielded the highest methane yield compared to the co-digestion ratios examined. Furthermore, no synergistic or antagonistic effect was observed for any of the co-digestion ratios tested. Nine different kinetic models (five conventional mono-digestion models and four co-digestion models) were compared and evaluated for both mono- and co-digestion studies. For CP:CM, cone and modified Gompertz with second order equation models were the best-fit for mono- and co-digestion systems, respectively, while for FW:DSS, superimposed model showed the best-fit for all systems.