How Atmospheric Methane Removal Works

Atmospheric methane removal involves breaking down, or oxidizing, atmospheric methane to produce carbon dioxide, water, and other byproducts, or using biological processes that produce biomass. Atmospheric methane removal could be an important additional climate response tool to limit near-term warming and is not a substitute for other climate solutions. Some approaches mimic the natural process by which methane is oxidized and leaves the atmosphere: ~90% from hydroxyl (OH) radicals, 1-5% from chlorine (Cl) radicals, and ~5% methanotrophic bacteria in the soil. Since a methane molecule is 43x more warming than a carbon dioxide molecule, this oxidation reaction results in a net decrease in near-term warming.

Methane is a stable molecule, so energy input is needed to kickstart the reaction. This energy can come from heat, light, radicals, electric potential, or biological enzymes. Multiple approaches to atmospheric methane removal have been proposed, ranging from biological methods to engineered catalytic systems to atmospheric methods. Some are in the early research stage and have potential for feasibility, scalability, and safety; some have been tested at the lab scale and would need significant advances to become feasible; and some are purely theoretical, limiting our ability to assess their potential.

Developing these potential approaches will require significant research and development and careful consideration of direct and indirect climate benefits, cost, environmental and health impacts, governance, and social license to operate over the full lifecycle of the approach. These impacts should be assessed holistically, comparing any potential deployment against a counterfactual future where atmospheric methane removal was not deployed, rather than against the present. The potential scale and time to scale for each approach are also important considerations, given the urgency of addressing rising temperatures.

Atmospheric methane removal is a challenging prospect given the very low concentration of atmospheric methane (currently ~2 ppm). Studying atmospheric methane removal would help us determine what, if any, additional tools may be able to be added to our overall climate response portfolio. If safe, effective, and scalable atmospheric methane removal solutions are found, it’s critical that they always supplement, not replace, other emissions avoidance and carbon dioxide removal solutions to further reduce climate risk. Atmospheric methane removal is not a substitute for other climate solutions. As the future feasibility and scale of atmospheric methane removal is unknown, it’s also crucial we don’t depend on potential future atmospheric methane removal solutions at the expense of greater ambition today with current climate solutions.