Last year was the hottest on record, and scientists are clear that the world is on track to exceed 1.5 degrees C (2.7 degrees F) of global warming. Methane, a potent greenhouse gas (GHG), is a significant and growing part of this problem. It is the second-most impactful GHG after carbon dioxide (CO2) and, even though there is much less methane than CO2 in the atmosphere, it traps heat much more effectively than CO2.
Methane concentration in the atmosphere has accelerated rapidly since the early 1900s, driven both by human-caused methane emissions and increased methane emissions from natural sources due to human-induced climate change. Reducing these emissions is critical, and initiatives like the Global Methane Pledge and new technologies to track methane emissions show a growing commitment to do so. But climate models show it may not be enough to achieve climate goals. That’s why some scientists and researchers are now exploring atmospheric methane removal, which focuses on removing methane already in the atmosphere, as a potential option to further reduce warming.
Many questions about methane removal science, technology and governance remain. Moreover, there is still a limited body of research available on these topics. But based on available research — including a seminal report from the United States National Academies of Sciences, Engineering, and Medicine released in October 2024 — this article answers five key questions about what we know and what we still need to find out to understand whether atmospheric methane removal can be considered a viable way to help address the climate crisis.
1) Where does methane come from and where does it go?
More than half of global methane emissions come from human-caused, or anthropogenic, sources. Methane emissions primarily come from fossil fuels and the waste and agriculture sectors, including rice paddies and cows’ digestion (i.e., enteric methane), which will be difficult to fully avoid as global demand for food increases.
The remaining methane emissions come from natural sources, like wetlands, freshwater bodies and thawing permafrost. Methane emissions from these sources are increasing due to human-induced climate change. There is evidence that wetlands, particularly tropical wetlands, are contributing to the recent spike in methane concentration via a harmful feedback loop: the more global temperatures rise, the more methane is released.
Methane stays in the atmosphere for around 10 years because there are significant “methane sinks” that help break it down. More than 90% of methane is naturally broken down, or oxidized, into CO2 and water in the atmosphere. Since methane is a more potent greenhouse gas than CO2, breaking methane down into CO2 and water reduces its warming potential. This breakdown mainly happens with what is known as a hydroxyl radical – a highly reactive molecule that occurs naturally in the atmosphere and helps break down different types of air pollutants and greenhouse gases.
The remaining 10% of atmospheric methane is broken down by other molecules in the atmosphere and by bacteria in soils and plants.
2) Why are methane emissions a problem, and how can we reduce them?
Methane emissions have a relatively short lifetime in the atmosphere—typically nine to 12 years, compared to hundreds or even thousands of years for CO2. However, methane is a particularly potent GHG, trapping the sun’s heat 84 times more impactfully than CO2 over a 20-year period.
Because of its potency and short lifetime, methane concentration in the atmosphere has an outsized impact on near-term warming, including the level and timing of peak warming. In fact, methane has contributed around 0.5 degrees C of the 1.2 degrees C of global warming since pre-industrial times — over a third of the warming we’re experiencing today.
Reducing methane and other GHG emissions is the most important step to address climate change and is generally much more cost effective than removing emissions from the atmosphere.
Methane emissions come from scattered and diverse sources which makes mitigation challenging. But advancements like improving leak detection in oil and gas operations, better irrigation practices in rice cultivation, and capturing landfill gas can help address anthropogenic sources. Emissions from natural sources like wetlands are hard to reduce and are increasing due to climate change.
The Intergovernmental Panel on Climate Change (IPCC) estimates that the maximum feasible level of methane emissions reduction is 45% by 2050, but 1.5-degrees-C-aligned scenarios require greater reductions. As a result, some scientists are looking into methane removal as a complementary approach to reduce near-term warming and address methane emissions that can’t be fully abated.
3) What are some potential ways to remove methane from the atmosphere?
Potential approaches to remove atmospheric methane are in very early stages of development. A few scientific papers in recent years have started to explore the topic, but research funding is very limited, with less than $10 million estimated to have been invested to date.
Broadly, methane removal approaches aim to accelerate naturally occurring processes and fall into one of two categories: open and closed systems. Closed-system approaches treat air within a system that is closed to the wider environment, containing any unintended impacts. Open-system approaches intervene in the environment directly, meaning that any secondary impacts are less contained.
Open-system methane removal can involve changes to atmospheric chemistry that are not well understood and can be non-linear, meaning they can have unintended and exponential impacts on other climate forcers and air quality. These interactions must be better understood to make sure any methane removal activities have a net climate benefit.
Within these two categories there are several ways to remove atmospheric methane, each with different variations:
- Ecosystem Uptake Enhancement: Ecosystem-based approaches leverage natural methane sinks, mainly methane-consuming microorganisms in soils, to oxidize additional methane. For example, use of soil amendments — like compost, crop residue or biochar — and addition of certain minerals could enhance methane uptake in soils. It may also be possible to select or engineer methane-consuming bacteria to take up methane faster. These methods are in very early stages of development and require careful field level assessment of their impacts on ecosystems and biodiversity.
- Atmospheric Oxidation Enhancement (AOE): This involves introducing materials into the atmosphere that enhance methane oxidation, such as reactive chlorine or hydroxyl radicals. Similar to solar radiation modification (SRM), these methods could face significant public and regulatory scrutiny due to the uncertainties and potential negative side effects associated with altering atmospheric chemistry. Much more research is needed to understand feasibility and full impact on atmospheric chemistry, as well as robust governance structures, given the potential wide-ranging impacts.
- Methane Reactors: Methane reactors are semi-contained systems designed to expose methane in ambient air to materials that can oxidize or break it down. For example, ultraviolet light can directly oxidize methane and heat can activate a catalyst that oxidizes methane. Methane reactors are commercially available today for use where methane concentration is high, but significant technological advances are needed to make them effective for atmospheric concentration of methane. For example, moving enough air to capture 6 billion tonnes of CO2 through direct air capture (roughly the scale of carbon removal outlined by the IPCC to align with a 1.5-degrees C pathway) would only remove 10 million tonnes of methane (equivalent to 1 billion tonnes of CO2).
- Surface Treatments: Surface treatments include applying methane-oxidizing coatings to large, exposed surfaces, such as buildings or surfaces that contact lots of air, like wind turbine blades. These treatments use materials such as metallic coatings that break down methane when exposed to light. However, they are currently too expensive and require significant advancements in methane removal efficiency and scalability to be practical.
- Methane concentrators: Methane concentrators are materials or devices that could theoretically capture and concentrate methane from the air. However, none have yet been identified or tested, hence these are currently just at the idea stage. If developed, they could concentrate methane in ambient air before it enters a methane reactor to be broken down, but are not a methane-removal technology on their own.
Each of these technologies faces significant challenges. Some approaches are already applicable today for methane concentrations greater than 1,000 ppm, which exist near methane sources like coal mines and dairy farms. However, making them effective at the much lower atmospheric methane concentration of 2 ppm is a key challenge.
The National Academies report concludes that methane reactors, surface treatments and methane concentrators depend on significant technological breakthroughs to feasibly operate at atmospheric methane concentrations of 2 ppm. Atmospheric oxidation enhancement and ecosystem uptake enhancement have possible pathways to feasibility at 2 ppm, but there are significant uncertainties.
4) How does atmospheric methane removal compare to carbon dioxide removal?
There is scientific consensus that, along with deep emissions reductions, carbon dioxide removal (CDR) is needed to meet global climate goals. While atmospheric methane removal is another type of “removal,” it operates differently from CDR in key ways.
Carbon removal typically involves sequestering CO2 in soils, the ocean or underground. In contrast, methane removal focuses on breaking methane down into less harmful components: CO2 and water. As such, methane removal doesn’t require the transport and sequestration steps associated with carbon removal technologies. This difference makes measurement more challenging, as tracking chemical breakdown in the open atmosphere is inherently more complex than monitoring sequestered CO2.
While carbon dioxide can remain in the atmosphere for thousands of years, methane naturally breaks down within a decade or so. Further, methane spends less time in the atmosphere as its concentration decreases: a lower concentration of methane means more hydroxyl radicals are available, which speeds up the oxidation process — a positive feedback loop. This means that methane removal and reduction not only directly reduce concentration in the atmosphere, but also contribute to this positive feedback.
Unlike CO2, methane interacts with other gases in complex and sometimes unpredictable ways. Efforts to accelerate its breakdown could have unintended effects on air quality and climate systems and must be better understood to ensure a net climate benefit. For example, open system methane removal approaches that involve cycling chlorine to the atmosphere, increasing its capacity to break down methane, could also increase ozone-depleting substances and worsen surface air quality.
5) What existing governance frameworks would apply to methane removal?
Effective regulation of methane removal technologies is essential to address potential environmental impacts, jurisdictional complexities and societal implications. While there are no specific governance frameworks for atmospheric methane removal, some existing legal frameworks would apply to methane removal activities. Regulatory requirements largely depend on the type of approach (open or partially closed system), the location of the activity (over land or the ocean), whether it crosses national borders and the intent (research or commercial deployment).
Impacts of partially closed system technologies, like methane reactors and methane concentrators, would be more contained, so the relevant legal frameworks are more limited, primarily relating to siting processes and local impacts on the environment and people. For open-system technologies that introduce substances directly into the environment, like atmospheric oxidation enhancement, the legal framework is more complex due to potential transboundary impacts and a wider range of potentially affected parties.
Jurisdictional clarity is also crucial. In the United States, federal environmental laws such as the Clean Air Act and Clean Water Act govern land-based deployments, along with local zoning laws, land use regulations and tribal consultations. Ocean deployments, by contrast, are primarily regulated under international agreements like the UN Convention on the Law of the Sea (UNCLOS) for activities further than 200 nautical miles offshore, and the laws of coastal nations within 200 nautical miles off their shores. However, the overlapping authorities of federal, tribal, state and local jurisdictions underscore the need for streamlined governance frameworks.
Lastly, some legal frameworks differentiate small-scale research activities from commercial deployment. While it can be difficult to draw clear distinction between the two, the Convention on Biological Diversity and London Protocol, for example, have adopted decisions that allow small-scale research for climate geoengineering techniques, but bar large-scale deployment.
Beyond these laws and regulations, comprehensive governance would also require: strong protocols for measurement, reporting and verification; public engagement to understand concerns and inform project permitting; protocols for risk assessments; health and safety standards; and data sharing and transparency mechanisms.
What’s Next?
There are significant challenges associated with making atmospheric methane removal a viable option to help address near- and long-term climate change. Several proposed approaches rely on major technological breakthroughs, making them both uncertain and potentially cost-intensive.
Given constraints on public funding for climate research and development writ large, and the significant challenges outlined above, it is reasonable to consider whether funding is best used for methane removal research. It is also reasonable to be concerned whether focusing on methane removal may detract from more feasible efforts to reduce methane emissions — the same moral hazard, or mitigation deterrence concern, present with carbon dioxide removal.
However, if methane removal is proven to be net-climate beneficial, cost-effective, safe and scalable, and if appropriate governance frameworks are developed, it could help address growing methane emissions from natural and human sources that can’t be abated. For this inescapable reason, much more research is needed to better understand the feasibility of proposed methane-removal technologies and approaches, as well as cross-cutting areas like methane sources and sinks, governance, regulation and social impacts.
The National Academies recommend a two-phase research approach to assess the feasibility of methane-removal technologies. Phase one, lasting 3-5 years, with $50-80 million in research funding each year, would focus on addressing foundational knowledge gaps and enabling more targeted research. Phase two would evaluate the most promising technologies for climate-scale viability. This would aim to resolve remaining technical, economic and social barriers, determining whether further investment in specific methane-removal technologies is justified before considering potential deployment.
Atmospheric methane removal presents intriguing potential as a tool to address near-term warming and residual methane emissions, but significant uncertainties remain. Building a robust knowledge base will allow informed decisions about the role — if any — that methane removal can play in meeting climate goals, while ensuring prioritization of the most effective and equitable climate solutions.
