Nitrous oxide emission mechanisms during intermittently aerated composting of cattle manure

► N2O emission mechanisms during intermittent aerated composting were studied. ► Nitrification was indicated as the main pathway for N2O emission under aeration. ► Occurrence of nitrification can be indicated by monitoring respiratory quotient. ► Rapid N2O emission was triggered by denitrification when oxygen level was dropped. ► Appropriate management of intermittent aeration is desirable for N2O reduction. To investigate the mechanisms of nitrous oxide (N2O) emission during intermittent aeration in the composting process, a laboratory scale experiment with continuous measurement of N2O emission was conducted with cattle manure. A low oxygen mode (2.5% oxygen in the inlet for 1day), anaerobic mode (0.13% oxygen for 0.25day), and aerated mode (20.5% oxygen for 2days) were sequentially set up three times after 22days of continuous aeration to replicate intermittent aeration. The total N2O emission was 0.26–0.35mmol, 0.27–0.32mmol, and 0.14–0.23mmol during the low oxygen, anaerobic, and aerated modes, respectively. Denitrification was indicated as the main N2O emission pathway in the anaerobic and low-oxygen modes, while nitrification was indicated as the main pathway in the aerated mode and under continuous aeration. Results from this study suggest that nitrification is an important pathway for N2O emission as well as denitrification.