Atmospheric Removal of Nitrous Oxide: Approaches and Feasibility

Nitrous oxide (N2O) is the third-largest contributor to anthropogenic greenhouse gas forcing and the dominant anthropogenic ozone-depleting emission. While mitigation can flatten emissions, there is no clear pathway to eliminate residual emissions from agriculture and other diffuse sources, a key challenge for climate stabilization. The potential role of atmospheric removal has not been holistically assessed, yet N2O's high potency and long atmospheric lifetime indicate the potential for a durable climate benefit. This review synthesizes emerging approaches for atmospheric N2O removal, organized by reaction mechanism (thermal destruction and thermocatalysis, photolysis, gas-phase radical reactions, photocatalysis, and biological reduction) and deployment format (closed versus open system). Each is evaluated for technical efficacy, climate viability, environmental and social viability, and economic plausibility using lower-bound cost models. No approach yet satisfies all four: gas-phase radical reactors are precluded by their kinetics, thermocatalytic and photocatalytic reactors require ten- to hundred-fold performance gains, and open-system approaches have the lowest cost floors but face the greatest measurement and governance challenges. These results identify the performance thresholds and broader constraints that govern feasibility across pathways, providing a foundation for a research agenda and for assessing the role of N2O removal alongside emissions mitigation.