Optimization of operations for nitrous oxide production and mitigation in aerobic and Aerobic-Anaerobic landfill method on MSW degradation

N₂O is a potent greenhouse gas, induced by aeration coupled with leachate recirculation in Municipal Solid Waste (MSW) landfills. In this study, N₂O emission was measured in the aerobic and Aerobic-Anaerobic Landfill Method (AALM) with or without leachate recirculation at two aeration rates in synthetic MSW. The experiment was carried out for six Plexiglass® landfill simulation reactors. Low aeration (1.6 l/kg-DM/h) was supplied in RLA, RLAA (Recirculatory) and LAA (non-recirculatory) reactors, while an aeration rate three times higher (4.8 l/kg-DM/h) was performed for RHA, RHAA, and HAA reactors. Based on the supplied leachate quantity, leachate recirculation was performed in five different phases. The results showed that a significant amount of N₂O was produced in all reactors. The largest N₂O emission of 0.11 and 0.13 g/kg-DM were observed in the RHA and RHAA reactors, respectively. Higher N₂O and cumulative GHG was produced in high aeration reactors compared to the low aeration reactors. Recirculated leachate promoted waste stabilization, as reflected in the diminishing CH₄ production and other leachate pollutant parameters, especially NH₄ ⁺-N. It has been evaluated that in the operative or newly placed waste landfill, in-situ aeration with leachate recirculation exhibits the significant N₂O production. However, lower amount of leachate in the later stage beneficial to inhibit the N₂O production. It is recommended that in-situ aeration will become more effective after the recovery of CH₄ from newly placed waste in an operative landfill for net GHG reduction, especially N₂O reduction and early stabilization of landfills.