Effect of bulking agent on the reduction of NH3emissions during thermophilic composting of night-soil sludge

Abstract

Night-soil sludge contains a high percentage of nitrogen and releases large amounts of ammonia when it is composted. In this research, three types of bulking agents, sawdust, perlite, and activated carbon, were used, and the effects of these bulking agents on the reduction of NH₃ emissions during thermophilic composting were evaluated. It was found that not only is sawdust the most effective agent in reducing NH₃ emissions, but that it also effectively promotes organic matter decomposition. Increases in the mixing ratio of sawdust in the range adopted in the present research, from 70% to 92% on a dry-weight basis, appeared to cause no adverse effects on the decomposition of sludge itself. And the higher the mixing ratio of sawdust, the more effective the reduction in NH₃ emissions, however this effect was not enough to completely suppress these emissions, even at the highest mixing ratio.