A numerical model is presented based on conceptual considerations of chemical and biological reaction processes in landfills. The model enables the details of mixed-culture population dynamics and locally based multiple reaction schemes to be described as functions of the chemical and physical environmental conditions. In its current stage of development, the model is primarily used as a research tool to analyze the influence and value of various model parameters on biodegradation and landfill gas formation processes. In order to test the accuracy of the model, simulation results have been compared with experimental data obtained from a 340-day experiment on the degradation of waste within a “consolidating anaerobic reactor (CAR).” A good match with simulated results was obtained to the measurement of methane and carbon dioxide formation, as well as to the measured concentrations of sulphate and ammonium ions in the liquid phase. In particular, the experimentally observed influence of sulphate on the meth...