Potential Air Quality Side-Effects of Emitting H₂O₂ to Enhance Methane Oxidation as a Climate Solution

Methane (CH₄) is a greenhouse gas with a global warming potential 81.2 times higher than carbon dioxide (CO₂). The intentional emission of oxidants into the atmosphere has been proposed as a geoengineering solution to accelerate the oxidation of CH₄ to CO₂, thereby reducing surface warming. However, there has been little consideration for competing atmospheric oxidation pathways that will reduce CH₄ oxidation efficiencies and result in the formation of secondary pollutants such as ozone and particulate matter. Using a global chemical-transport model, we simulate a proposed technology to intentionally emit H₂O₂ into the atmosphere to elevate OH concentrations and enhance CH₄ oxidation. We find that proposed emission rates of oxidants have minimal impacts on monthly average tropospheric ozone and particulate matter concentrations. However, competition for the oxidation of CH₄ would necessitate widespread adoption of such technology to remove substantial concentrations of atmospheric CH₄, which would in-turn cause considerable increases in regional winter-time particulate matter. Our work underscores the need to consider competing chemistry in evaluating the efficacy and side effects of proposals to enhance the atmospheric oxidation of CH₄ as a climate solution.