Dynamic emissions of N₂O from solid waste landfills: A review

Abstract

Nitrous oxide (N₂O) is an important greenhouse gas (GHG) and an ozone-depleting substance that can be emitted from landfills. Understanding the dynamics of N₂O and its contribution to total emissions is critical to effective mitigation measures. This study outlines the dynamics of N₂O in solid waste landfills and N₂O emissions from them. N₂O generation in anaerobic landfills is primarily due to denitrification and, to a lesser extent, nitrification, which occurs in the oxygenated cover soil layer and the working face. However, nitrification and denitrification are very limited within landfills. The landfill leachate contains high concentrations of ammonia (NH₃). Thus, a significant amount of N₂O is generated from aerobic processes during leachate treatment. Bioreactor landfills emit more N₂O than traditional anaerobic landfills. The majority of N₂O emitted from bioreactor landfills is generated through different pathways, such as hydroxylamine (NH₂OH) oxidation, nitrifier denitrification, and heterotrophic denitrification. These processes are affected by several factors, including the carbon-to-nitrogen (C/N) ratio, NH₃ oxidation rate NH₃ oxidation rate, redox conditions, and temperature. Addressing N₂O emissions from landfills will be necessary to achieve an integrated nitrogen management strategy that helps minimize N₂O emissions.