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

Abstract

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.