Mitigation of greenhouse gas emission from the cattle manure composting process by use of a bulking agent.

摘要

The greenhouse gas (GHG) [methane (CH₄) and nitrous oxide (N₂O)] mitigation effects of mixing dried grass into passively-aerated manure during the composting process (which accounts for 68.7% of Japanese dairy manure management) were assessed. Gaseous emissions [CH₄, N₂O, carbon dioxide (CO₂) and ammonia (NH₃)] from about 4 t of fresh dairy manure with or without 400 kg of dried grass mixed in were measured by the dynamic chamber method. The addition of dried grass contributed to a decrease in GHG emissions from 20.8+or-1.3 g kg-1 volatile solids (VS) to 5.4+or-1.4 g kg-1 VS (74.3% mitigation) for CH₄ and from 7.4+or-2.6 g N₂O-N kg-1 N_initial to 2.7+or-0.4 g N₂O-N kg-1 N_initial (62.8% mitigation) for N₂O. By applying this strategy, the expected reduction of GHG emission would be 70,466 t CH₄ yr-1 and 1379 t N₂O-N yr-1 (1907 Gg CO₂ eq. yr-1 in total) in the Japanese dairy sector. On the other hand, it was showed that CO₂ and NH₃ emissions increase [from 424.4+or-214.9 g CO₂ kg-1 VS to 603.8+or-99.6 g CO₂ kg-1 VS for CO₂ and from 16.9 +or-7.1 g ammonium-nitrogen (NH₃-N) kg-1 N_initial to 38.3+or-3.5 g NH₃-N kg-1 N_initial for NH₃] by this method. Moreover, the mechanism of this significant N₂O mitigation effect cannot be explained, and a better understanding of this effect could further improve the GHG mitigation strategy.