Approaches to Atmospheric Methane Removal

There are several approaches in very early exploration to accelerate the breakdown of atmospheric methane. All of these are either in early research stages, or are ideas that haven’t received much if any research attention yet. In each case, fundamental questions remain about their feasibility, scalability, and side effects. Research funding is a bottleneck for much of the field.

Atmospheric Oxidation Enhancement

Atmospheric Oxidation Enhancement (AOE) is the concept of enhancing the overall oxidative sink in the atmosphere, through generating additional chlorine or hydroxyl radicals. The current pathways in early research stages are Iron Salt Aerosols (ISA), hydrogen peroxide dispersal, and photocatalytic aerosols. Any approach proposing to alter atmospheric chemistry with the aim of oxidizing additional methane will need very careful study to understand its full atmospheric chemistry impact, including health, environmental, and climate-impact side effects. There is important supporting scientific work to pursue in parallel with any of these methods to advance our understanding of the impacts of altering oxidizing radicals in the atmosphere in general.

Terrestrial Methane Consumption

Terrestrial Methane Consumption explores whether natural terrestrial or aquatic methane sinks can be safely, sustainably, and meaningfully enhanced to breakdown additional atmospheric methane. Approaches under very early exploration are soil amendments, and introducing methane-oxidizing bacteria. Their potential ability to address atmospheric methane at scale is currently speculative.

Catalytic Engineered Systems

Catalytic engineered systems are designed to pass air from the atmosphere, either passively or actively, through catalytic systems which leverage energy from the sun, an artificial light, or heat to oxidize methane. These catalysts include thermocatalysts, photocatalysts, and radicals produced artificially through photolysis (using light to break apart a molecule). Generally, these catalysts could be deployed in reactors which use fans or passive air flow to intake air from the atmosphere, though photocatalysts might also be deployed as a coating on panels, rooftops, or other large surfaces exposed to sunlight and air.

Given the low atmospheric concentration of methane, any flow through system would have to process massive amounts of air to hit the 10 Mt/yr target. For example, if you put methane oxidizing reactors on every carbon dioxide direct air capture system that is supposed to be installed by 2030 (60 Mt CO₂/yr or around 5 billion CFM), it's only around 0.1 Mt/yr of methane removed.

In addition, innovation would be needed for any of these methods to bring down air-handling costs, and some of the approaches require approach specific breakthroughs in order to make each approach cost-plausible and climate-beneficial.

Some of these same technical approaches are also being explored for treating higher methane concentration streams before they enter the atmosphere. We do not evaluate these approaches for their potential ability to do so here, and focus on atmospheric methane concentrations.

State of Atmospheric Methane Removal Approaches

The evaluations below are all in the context of atmospheric methane concentrations (currently 2ppm). Some of these same technologies are being explored or deployed to address higher concentration methane streams from various sources before the methane becomes mixed into the atmosphere. For those applications of some of these same technologies, the evaluation on each axis could be very different.