Patterns and quantities of NH3, N2O and CH4 emissions during swine manure composting without forced aeration––effect of compost pile scale

To evaluate the NH3, N2O, and CH4 emissions from composting of livestock waste without forced aeration in turned piles, and to investigate the possible relationship between the scale of the compost pile and gas emission rates, we conducted swine manure composting experiments in parallel on small- and large-scale compost piles. Continuous measurements of gas emissions during composting were carried out using a chamber system, and detailed gas emission patterns were obtained. The total amount of each gas emission was computed from the amount of ventilation and gas concentration. NH3 emission was observed in the earlyperiod of composting when the material was at a high temperature. Sharp peaks in CH4 emission occurred immediatelyafter swine manure was piled up, although a high emissions level continued after the first turning onlyin the large-scale pile. N2O emissions started around the middle stage of the composting period when NH3 emissions and the temperature of the compost material began to decline. The emission rates of each gas in the small and large piles were 112.8 and 127.4 g NH3-N/kg T-N, 37.2 and 46.5 g N2O-N/kg T-N, and 1.0 and 1.9 g CH4/kg OM, respectively. It was found that changing the piling scale of the compost material was a major factor in gas emission rates