Abstract A new model is proposed to deal with the composting reaction. This model made it possible to calculate the courses of the rate of carbon dioxide evolution, volatile matter conversion, temperature, and moisture content under various aerating operations. The prediction by the model was compared with measurements in laboratory and commercial scale compostings, and was found to agree satisfactorily with the measurements. The model was then used to search for the optimum conditions to obtain sufficiently dry compost. There are two key factors that affect the rate of water vaporization in composting: the aeration rate and the reaction temperature. These two factors are interrelated. The optimum reaction temperature for biological reaction was approximately 60°C regardless of the aeration rate in the parameter range studied. The calculation based on this model suggests that water can be eliminated most effectively when the aeration is so controlled as to keep the reactor at its optimum reaction temperature i.e., 60°C. The drying efficiency was evaluated in terms of the rate of water removal and the total amount of water removed in one batch operation.
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