Nitrous oxide emission mechanisms during intermittently aerated composting of cattle manure

Abstract

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 1 day), anaerobic mode (0.13% oxygen for 0.25 day), and aerated mode (20.5% oxygen for 2 days) were sequentially set up three times after 22 days of continuous aeration to replicate intermittent aeration. The total N₂O emission was 0.26-0.35 mmol, 0.27-0.32 mmol, and 0.14-0.23 mmol 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.