Methane (CH₄) is a powerful greenhouse gas that has caused about 0.5°C of warming today. Methane has a short-lifetime (about a decade in the atmosphere), during which it is a very powerful greenhouse gas — ~43x more powerful than carbon dioxide (CO₂) molecule to molecule (IPCC Table 7.15). Because of its short-lived nature, methane emissions reductions lead to decreased atmospheric concentrations on decadal timescales; decreased atmospheric concentrations lead to a decrease in global temperature. Methane has a particularly acute impact on near-term warming, while cumulative CO₂ emissions—given its long lifetime—drive long-term warming outcomes. Only by dramatically cutting our emissions of both in parallel, can we minimize peak global temperatures.
Methane emissions can be broken down into two broad categories: currently ~40% from natural sources (e.g. freshwaters, wetlands, geological), and ~60% from anthropogenic sources (ruminants, fossil fuel industry, landfills and waste). Methane emissions can be broken down into two broad categories: currently ~40% of emissions are from natural sources (e.g. freshwaters, wetlands, geological), and ~60% are from anthropogenic sources (ruminants, fossil fuel industry, landfills and waste). According to IPCC models, for the world to stay below 1.5°C or 2°C, and reduce overshoot, atmospheric methane levels must sharply decrease in parallel to racing to net-zero CO₂ emissions.
However, methane levels are still rapidly increasing. There are a few pieces of bad news here: (1) only 57% of projected 2030 anthropogenic methane emissions have technically-feasible solutions today (Ocko 2021), and (2) there’s increasing evidence that natural methane sources are increasing as a result of warming and will continue to do so, and this isn’t yet incorporated into IPCC climate models or the “methane budget” (Kleinen 2021). Some of the natural sources risk entering positive feedback loops emitting significantly more methane, and we have no direct response to this risk today (McKay 2022).
We must cut all possible methane emissions as quickly as possible in order to start bending the curve on warming, by urgently deploying available solutions. To complement those efforts, we must also invest in two urgent categories of methane R&D priorities to have more options in the future to further drive down atmospheric methane levels: (1) developing missing economically-feasible and readily-deployable solutions for methane emissions reduction to keep overall warming down, and (2) developing ways to accelerate the destruction of methane already in the atmosphere to address historical emissions, elevated natural emissions, and any remaining unabateable emissions, in order to further slow warming and build capacity to intercept possible natural methane feedback loops (Jackson 2021).
Fortunately, methane has useful properties that can be exploited for removal—methane naturally oxidizes to CO₂ + H₂O in the atmosphere and soil. While it has a much lower atmospheric concentration than CO₂, it has a much higher instantaneous warming impact, and because the conversion of methane to CO₂ and H₂O dramatically reduces its climate impact, storage and sequestration infrastructure is not necessary (Jackson 2021). Current commercialized technologies oxidize methane down to ~2,000 ppm (using regenerative thermal oxidizers); developing solutions that could economically oxidize methane down to 2ppm (atmospheric concentrations) would greatly expand the scope of current warming that could be addressed. Approaches currently being explored include catalysts, reactive radicals, and biological pathways using methanotrophic bacteria. Some of these technologies may be able to address concentrations between 2 ppm and 2,000 ppm, and if developed, could be used to treat methane emission sources before the methane enters the atmosphere, much like flaring does today for very high-concentration streams (>4%, or 40,000 ppm). We call this point-source (or area-source) methane removal.
If solutions are found that can safely address atmospheric concentrations (2 ppm) at large scale, atmospheric methane removal could be a game-changer for near-term climate management by mitigating the impact of the existing elevated atmospheric methane levels due to historical emissions (currently 0.5°C and still growing, though hopefully this trend will be reversed with methane mitigation), and continued growing natural methane emissions as a result of the warming that has already been caused. Potential atmospheric methane removal solutions have a broad range of possible form-factors, from catalysts that may be able to be integrated into existing airflow systems, to atmospheric interventions. The science is very early on all of these methods, and the current state of the science does not yet support deployment, particularly for atmospheric interventions. Due to the uncertainty surrounding the characterization of current proposed methods, and discovery of new methods, it is far too early to say if, when, at what scale, and at what cost these systems might operate in the future. These methods and research into them is not a replacement for decreasing all methane and other greenhouse gas emissions that we possibly can, and continuing to develop additional emissions reductions strategies in parallel.
In order to stay below 1.5°C, atmospheric methane concentrations need to sharply decrease at the same time that we cut CO₂ and all other greenhouses gases as rapidly as possible, achieving net-zero CO₂ emissions mid-century. Much of the decrease in atmospheric methane concentration will be achieved through methane emissions reductions, rapidly deploying available solutions, and developing more. Spark is helping to also rapidly accelerate the nascent methane removal field as a complement to these other strategies, with unique potential to help in avoiding and potentially mitigating the warming impacts of some natural feedbacks and tipping points (McKay 2022). In a decade, this field may be a critical part of global climate response, with a meaningful global impact on near-term warming. We’re actively mapping the potential solutions, building a global network of experts, and funding early research efforts to meet the world’s need.