Abstract
In order to produce the compost with high nitrogen contents, ammonia recovered from vacuum-induced aeration composting system was added to compost after the biooxidative phase was finished. The present study investigated how to add the recovered ammonia to compost during the maturation phase. Two addition methods were examined: One was to add a large quantity of recovered ammonia to compost for once at the beginning of the experiments, the other was to add gradually increased amount of recovered ammonia to compost several times during the experiments. Results showed that the addition of recovered ammonia with gradually increased amount had a significant effect on the increase of the ammonium and nitrate-nitrogen contents in compost. In this experiment using this addition method, the nitrification was progressing from the beginning of the experiment and the maximum nitrate-nitrogen content was increased up to about 8.3 g・kg-dm-1. The accumulation of nitrate-nitrogen resulted from the nitrification led to the decreases in compost pH value of 6.5-6.6. As a result, volatilization of ammonia gas was inhibited by low pH and ammonium-nitrogen was fixed with compost. In contrast, when a large quantity of recovered ammonia was added to compost once at the beginning of the experiments, the loss of ammonium-nitrogen increased. Therefore, the addition of recovered ammonia with a large quantity resulted in failure of the fixation of nitrogen to compost.
