Regulation Trial of Nitrous Oxide Emissions Caused by Composting Swine Manure with Nitrite-Oxidizing Bacteria Added for Nitrification Promotion

We investigated the environmental effects of gas regulation practices using nitrite-oxidizing bacteria (NOB) for nitrification promotion in practical-scale manure composting experiments. With several tons of swine manure piled in parallel chambers, we determined the effects of adding NOB to matured swine manure by conducting two runs of composting trials. Both the control pile (without NOB) and the experimental pile (with NOB) were stored in composting chambers under continuous ventilation, and composting entailed several turnings in following the general swine farming procedure. During all periods of composting, the concentrations of greenhouse gas (GHG) and ammonia (NH3), ventilation rate, and temperature were measured every hour. We found that the addition of NOB significantly increased both the nitrate nitrogen (NO3--N) and nitrite nitrogen (NO2--N) content of compost products. However, environmental gas regulations were not met in the two runs. The addition of NOB effectively reduced N2O under oxidation facultative conditions (Run 1), but N2O increased in the passive-type compost under cool temperature conditions (Run 2). N2O emissions were found to largely depend on the manure composting conditions.