Effect of nitrite accumulation on nitrous oxide emission and total nitrogen loss during swine manure composting(Environment)

概要

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The present study investigated the nitrogen balance in swine manure composting to evaluate the effect of nitrite (NO_2^-) accumulation, which induces nitrogenous emissions, such as N_2O, during compost maturation. During active composting, most N losses result from NH_3 emission, which was 9.5% of the initial total nitrogen (TN_<initial>), after which, NO_2^- began to accumulate as only ammonia-oxidizing bacteria proliferated. After active composting, the addition of mature swine compost (MSC), including nitrite-oxidizing bacteria (NOB), could prevent NO_2^- accumulation and reduce N_2O emission by 70% compared with the control in which NO_2^- accumulated as a result of delayed growth of indigenous NOB. Total N_2O emissions in the control and in the treatment of MSC addition (MA) were 9.3% and 3.0% of TN_<initial>, respectively, whereas N losses as the sum total of NH_3 and N_2O over the whole period were 19.0% (control) and 12.8% (MA) of TN_<initial>, respectively. However, the difference in total N losses was markedly greater than that measured as NH_3 and N_2O, which were 27.8% (control) and 13.3% (MA) of TN_<initial>, respectively. These results demonstrated that the magnitude of nitrogen losses induced by NO_2^- accumulation is too large to ignore in the composting of swine manure.