Determination of nitrous oxide, methane, and ammonia emissions from a swine waste composting process

The amounts of harmful gas emissions from the process of composting swine waste were determined using an experimental composting apparatus. Forced aeration (19.2–96.1 l/m3/min) was carried out continuously, and exhaust gases were collected and analyzed periodically. With weekly turning and the addition of a bulking agent in order to decrease the moisture content and increase air permeability, the temperature of most of the contents rose to 70°C and composting was complete within 3–5 weeks. NH3, CH4, and N2O emissions were high in the early stage of composting. About 10%–25% of the nitrogen in the raw material was lost as NH3 gas during composting. The emission rate of NH3 mainly depended on the aeration rate, so that as the aeration rate rose, the level of NH3 emissions increased. The CH4 and N2O emissions could be kept lower with adequate treatment at more than 40 l/m3/min aeration. N2O may be mainly the result of the denitrification of NOx-N in the additional matured compost used as a composting accelerator.