Dynamic Simulation for Domestic Solid Waste Composting Processes

Modeling composting processes is the prerequisite to realize the process control of composting. In this paper, a simulation model for domestic solid waste composting processes was developed based on microbial process kinetics, mass conservation equation, energy conservation equation and water balance. Differential equations describing microbial, substrate, oxygen concentrations, moisture content and temperature profiles were derived. Considering that several factors (temperature, oxygen, moisture and FAS) in the process interacted to composting processes, microbial biomass growth kinetics was described. In order to verify the model, a series of aerobic composting experiments on domestic solid wastes were conducted. Temperature, moisture, microbial biomass growth, oxygen consumption rate and the concentrations of organic components were monitored in the composting processes and also simulated with the developed model. The simulation results were well consistent with the experimental results. It also could be seen from the model that the efficiency of composting processes could be raised and aeration requirements could be reduced by controlling the oxygen concentration in the exhaust air within a proper range. When the range is 8% to 12%, the aeration requirements reduced 79.61%. This result was verified by the composting experiment. When initial moisture content was higher than 66% or lower than 33%, it would significantly reduce the rate of substrate degradation. It indicated the effect of initial moisture content on the composting processes was significant. A simple sensitivity analysis demonstrated that two key parameters in composting modeling to determine were maximum specific growth rate ( max μ ) and yield coefficient (YY/S). Therefore, the composting processes could be optimized by the application of the developed simulation model. [The Journal of American Science. 2005;1(1):34-45].