Abstract
An optimum control problem for the first stage of the composting process was formulated based on the variational principle. The whole period for the composting process can be divided into three sub-periods, i.e., temperature increasing period, stable temperature period, and temperature decreasing period. The optimum control problems for the first two subperiods were numerically solved individually. It was found that 1) the aeration rate in the 1st sub-period should be low in order to raise the temperature of the compost mass as fast as possible to the value at which the composting reaction rate reaches the maximum, and 2) a much higher aeration rate is necessary in the 2nd sub-period than in the 1st sub-period so as not to accumulate excess heat generated in composting. Although the theory described in this paper was obtained for the batch-type composting process, this theory can be extended to a continuous system by replacing the sum of the 1st and 2nd sub-periods of composting process to the retention time in the vessel for compost mass.
