The Case for Methane Abatement

A focus on warming potential

Under the current most-probable greenhouse gas emissions scenario, our planet will cross a dangerous threshold - 2°C of warming - by 2050. To avoid this, both sweeping emission reductions and negative emissions technologies (NETs) are essential. However, yearly greenhouse gas emissions are projected to increase between now and 2050. NETs may be the panacea, but existing approaches - which focus almost exclusively on carbon dioxide - today collectively remove less than 2 gigatons per year: well below the 10 gigaton-per-year scale required by 2050 to counteract rising temperatures. 

So, how can we buy ourselves time to address the impending climate crisis? By shifting our focus to methane. Just like carbon dioxide, methane is a potent greenhouse gas. Anthropogenic emissions have caused atmospheric concentrations of methane to double since the pre-industrial era, contributing about 30% of the net warming over the same interval. But methane is distinct from carbon dioxide - and has more power in preventing warming between now and 2050 - because of two critical characteristics: warming potential and residence time.

Over a 20-year timescale, the warming potential of methane - or the amount of heat that each molecule traps in the atmosphere - is approximately 80 times greater than the warming potential of carbon dioxide (Figure 1). Because of this, a NET focusing on methane rather than carbon dioxide could potentially have the same impact on near-term warming at 80 times smaller scale. The scaling of NETs currently represents the largest bottleneck in their effective rollout. For example, if carbon dioxide alone is targeted, our yearly negative emissions capacity will need to be 105 times larger by 2050 to avoid 2°C of warming. By targeting methane, we can therefore increase the chance that NETs make a meaningful impact before it’s too late.

Figure 1. Global warming potential (GWP) of methane as a function of time after an emission pulse (data from Timma et al., 2020). GWP is expressed relative to carbon dioxide. Markers at 10-year intervals. 

The atmospheric residence time of methane - or average length of time before it is removed from the atmosphere - is about 10 times shorter than the atmospheric residence time of carbon dioxide. Atmospheric methane concentrations therefore respond significantly faster to a reduction in emissions when compared to the response of atmospheric carbon dioxide to an equivalent reduction in emissions (Figure 2). By targeting methane emissions reduction, we can more effectively limit the concentration of greenhouse gases in the atmosphere in the near future, in turn limiting catastrophic near-term warming.

Figure 2. Simplified model showing the first-order response of the atmospheric methane and carbon dioxide burdens to a 25% reduction in total emissions. Methane and carbon dioxide are normalised to their initial inventories and plotted as a function of time since emissions reduction.

Because of these characteristics, the focus of efforts to avoid 2°C or warming is gradually shifting from carbon dioxide to methane. This is exemplified by the recent (2021) launch of the Global Methane Pledge: a voluntary framework that encourages international action to reduce atmospheric methane concentrations. Unfortunately, this ‘encouragement’ has so far proved insufficient. Over the last few decades, year-on-year methane emissions have been accelerating at a record-breaking rate. The only existing technology that can prevent these emissions at scale is ‘flaring’ - the conversion of methane to carbon dioxide through burning. Clearly, this is no long-term solution. And, because no existing technology can remove methane from the atmosphere at scale, these emissions remain free to cause unchecked damage to the planet.

The Challenge

What has prevented us from targeting methane? Both atmospheric methane removal and methane emissions reduction suffer the same fundamental limitations:

🧪 Low concentrations. Compared to other greenhouse gases, methane punches above its weight, contributing a significant share of the net global warming at low atmospheric concentrations. At present, the atmospheric concentration of methane is ~ 2 ppm: about 200 times less than the atmospheric concentration of carbon dioxide (420 ppm). If we adopt the status-quo for atmospheric carbon dioxide removal - direct air capture - this means that we’d need to process 800 m3 of air to remove a single gram of methane (and this is assuming we could achieve 100% efficiency!). What’s more, about half of all methane emissions are highly diffuse streams (< 50 ppm) originating in natural systems like wetlands, permafrost and freshwater systems. Together, these systems occupy about 40 million square kilometres, or about 8% of Earth’s surface. To date, no technology is capable of efficiently removing methane at such low concentrations - let alone across millions of square kilometres.

🌳 Environmental externalities. Let’s say that, to avoid having to process large volumes of air, we instead release a reagent into the atmosphere, or across natural systems, that can remove methane in-situ. It’s difficult to imagine that this reagent could target methane without unintended consequences on the environment or on ecology. For example, in the past few years chlorine has garnered attention as a reagent to enhance the chemical loss pathways of atmospheric methane. However, the complex, non-linear nature of atmospheric chemistry means that whole-scale chlorine release could cause as many problems as it solves - including reversing the recovery of the Antarctic ozone hole.

💰Market opportunity. Let’s face it, voluntary schemes that simply ‘encourage’ a reduction in methane emissions won’t provide sufficient incentive to target methane at the scale or urgency that is currently necessary. To make real impact, we need to work with, rather than against, the market: meaning that methane emission reductions or negative emissions must create value for the consumer. For carbon dioxide reduction, value is created through trading in carbon offsets in a well-established, global scheme of credits. However, no formalised equivalent exists for methane. This means that methane abatement remains woefully under-funded. For example, in 2021/22 methane abatement financing (13.7 billion USD) made up about 1% of global climate financing (1.3 trillion USD): a share that is less than one quarter of the projected annual need for methane financing by 2030 (48 billion USD). While there have been some attempts to incorporate methane into the existing carbon trading scheme, these attempts often assign credit value based on 100-year warming potential: artificially reducing the value of methane, which has its greatest warming potential within 20 years of emission. Attempts to trade methane offsets within the existing carbon market can therefore hinder, rather than help, incentivise methane removal. 

The Solution

To date few, if any, companies have demonstrated the capacity to overcome these constraints. Take Carbon Twist, Zeotech and Zelp for example: three promising companies that use catalytic or adsorption technologies to remove methane directly from air. For these technologies to work, the air must contain higher-than-background concentrations of methane, meaning that they are most effective at high-concentration point sources. The capacity of the technologies to remove methane from the diffuse sources that characterise natural systems - let alone the atmosphere - is therefore limited. Other companies, like Blue Dot Change, are attempting to circumvent this constraint by direct release of chlorine-containing reagents into the atmosphere. But while chlorine radical generation is a recognised pathway of methane removal at low concentrations, the scale of chlorine release required to remove 45% of the atmospheric methane burden by 2050 - 1.25 Gt of chlorine per year - cannot be achieved without serious environmental externalities. And, with the exception of Bluemethane (a company that uses methane captured from wastewater treatment as a source of renewable energy), there has been limited work to address how any methane-removal technology might be financed within current markets.

At DSV, we believe that our unique, outcome-driven approach to venture creation might allow us to flip the constraints that methane abatement faces, yielding new solutions. Here are just some of the ways we could do this:

🧪 Low concentrations: why do the work? Technical orthodoxy tells us that, in order to capture greenhouse gases directly from the atmosphere, we need to construct plants that pass large volumes of air across custom-built adsorption surfaces. Given the low concentrations of methane in the atmosphere and in emissions streams, the infrastructure and energy burden this entails is effectively insurmountable. Thankfully, we already have access to artificial surfaces in contact with the atmosphere: buildings. The global surface area of buildings is currently around 106 km2, and this is projected to increase by 50% by 2030. By seeding these surfaces with methane-oxidising photocatalysts, we can replace energy-intensive air-pumping with natural air circulation, all while powering methane oxidation using energy from the sun. 

🌳 Environmental externalities: but methane removal is natural! Billions of years of evolution have already fine-tuned methane removal through methanotrophs, a type of microbe that oxidises methane to release energy and source carbon. These methanotrophs are highly effective, removing about 60% of methane emissions from natural sources before they ever enter the atmosphere. By promoting the growth of methanotrophs that are already present in permafrost, wetlands and freshwater, we can therefore work with, rather than against, natural systems to prevent methane emissions.

💰Market opportunity: let’s use markets that already exist. The lack of a formalised market for methane offsets doesn’t have to mean that methane has no value to the consumer. When methane is captured from the atmosphere or from emissions, it can be broken down through processes such as steam reformation or pyrolysis to yield high-purity carbon and hydrogen. These both have existing value: hydrogen as a carbon-neutral energy source, and carbon as an essential feedstock for production of computer hardware. So, by creating an onwards supply chain for the methane we capture, we can have the best of both worlds: value for the consumer and reduced global warming!

By exploring, combining, and iterating on these approaches, we will determine the value of venture creation for methane abatement. We’re currently recruiting scientists and engineers to lead this process as Founders-in-Residence (full-time, remote, fixed-contract). Each Founder-in-Residence would be responsible for developing technical approaches to target methane - either through atmospheric removal or emissions reduction - which, if impactful, could then be spun-out as new ventures. At every step of the way, the Founder is backed by the expertise and funding of DSV and its partners. Through this supportive, outcome-driven approach, 90% of our Founders create a company within 12 months, and these companies progress to TRL4 in an average of 18 months. So, if you have the technical expertise and drive to explore new ventures for methane abatement, we’d love to hear from you! You can find links to the roles we’re recruiting for here.

This opportunity is funded by the Grantham Foundation, a 501(c)(3) private foundation whose mission is to protect and conserve the natural environment. The Grantham Foundation communicates the risks of climate change and environmental degradation, builds collaboration and alliances between like-minded groups and individuals, and invests in philanthropic and entrepreneurial missions to create new climate solutions.