Several experiments for heat generation in composting process with livestock and farmyard wastes had been made by using a compost container in laboratory scale. Following the previously proposed procedure for estimation, the apparent rate of heat generation was calculated by applying the observed value of temperature in a compost bed to the analytical solution of temperature derived from a three dimensional model for heat conduction problem. The true (or total) rate of heat generation was also calculated by adding the latent heat loss due to vaporization of water to the apparent rate of heat generation. The following results were obtained.
1) Since the initial moisture content was relatively small, the increasing rate of temperature became large and the attainable maximum temperature was high in the early stage of the composting process. Because of the leakage of heat from the side walls of the compost container to the atmosphere, however, temperature decreased within a comparatively short period.
2) During the composting process, the effective region of heat generation moved gradually downward from the surface of the compost bed, so that the apparent rate of heat generation was varied remarkably with both the time and the vertical location in the compost bed.
3) As for some results of the experiments used relatively large contents of rice bran and chicken manure (Runs 3, 4), the steady high-temperature period became longer and the local maximum value of the apparent rate of heat generation was larger than the results of the other experiments (Runs 1, 2). Even in the latter experiments, in the limited region of the effective duration of heat generation, the average value of the apparent rate of heat generation in the compost bed was approximately 150kcal/m
3hr, and this value was not so different from the results of the former experiments.
4) The above-mentioned results on the average value of the apparent rate of heat generation were also similar to the results of the previous experiments under the considerably larger moisture conditions. As for a natural composting process, the average of the apparent rate of heat generation in the effective region of heat generation seemed to be almost independent of the moisture content and to fall within the range from 150 to 200kcal/m
3hr.
5) The calculated results of the true (or total) rate of heat generation agreed well with the values estimated from the consumption rate of carbon in the compost bed, and were almost equal to the results which had been obtained previously.
抄録全体を表示