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We studied anaerobic batch degradation of solid poultry slaughterhouse wastes with different initial waste and inoculum concentrations and waste-to-inoculum ratios and simulated the dynamics of the process with a new generation model. Our modelling results suggest that inhibited propionate degradation by long-chain fatty acids (LCFA) and inhibited hydrolysis by a high propionate concentration constituted the rate-limiting step in the waste degradation. Palmitate was the most abundant LCFA in the assays. Within 27 days of incubation, up to 0.55 to 0.67 m3 of methane (STP)/kg VS added was produced under the studied conditions. Lower waste-to-inoculum ratios exhibited a faster onset and rate of specific methane production. In all the assays, ammonification occurred within 3 to 6 days and accounted for 50 to 60% of total nitrogen.

A distributed model of solid waste digestion in a 1-D bioreactor with leachate recirculation and pH adjustment was developed to analyze the balance between the rates of polymer hydrolysis/acidogenesis and methanogenesis during the anaerobic digestion of municipal solid waste (MSW). The model was calibrated on previously published experimental data generated in 2-L reactors filled with shredded refuse and operated with leachate recirculation and neutralization. Based on model simulations, both waste degradation and methane production were stimulated when inhibition was prevented rapidly from the start, throughout the reactor volume, by leachate recirculation and neutralization. An optimal strategy to reduce the time needed for solid waste digestion is discussed.

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