Atmospheric Methane Removal to Slow Global Warming

The rapid pace and dire impacts of climate change urgently require powerful short-term mitigation strategies. Appropriately, the long-term target for intervening in global warming is CO2, but experts posit that methane should be the short-term target. Methane is 85 times more potent than CO2 on a 20-year timescale, contributes about 30 percent to global warming, and is increasing in the atmosphere. We propose to slow global warming by removing methane from air at significant scale using bio-based technology, with bacteria that subsist on methane (methanotrophs).

Challenge meets opportunity

Around the world, industrial sites — landfills, feedlots, composting sites, sewage treatment plants, coal mines, hydroelectric dams, and oil and natural gas extraction sites — are implicated in the significant and growing presence of methane in the atmosphere. There are some 15,000 such sites in the United States alone and a vast number globally. While some of the methane produced as a byproduct of industrial processes is being harvested for energy, much still escapes into the air surrounding these sites. On average methane is at 1.9 ppm in the atmosphere, and this low concentration creates challenges for removal. However, it is significantly enriched in the atmosphere over emission sites, on the order of 500 ppm. This concentration of methane over such readily identifiable sites presents an opportunity to intervene at these primary sources of methane pollution.

Proposed solution

There is no current technology that has been shown to remove atmospheric methane  effectively, at low cost, and on a global scale. But recent scientific advances coupled with new technical capabilities suggest a path forward. The past decade has seen major advances in the understanding of methanotrophs, their metabolism and enzymes, and their role in nature. At this stage, opportunities exist for both natural and optimally engineered biological systems to consume methane. At the same time, improved bioreactor designs are opening up new capabilities and use scenarios.

Many methane mitigation strategies are focused on reducing methane emissions, and this is an important goal.  However, these solutions will take significant time to develop and implement at scale.

We propose a novel approach to remove methane from air using bioreactors designed to employ methanotrophs and enhance their ability to remove methane. Positioned near methane-emitting sites, these designed bioreactors will feature blowers that draw air in, where methanotrophs will consume methane from the air, converting it to usable biomass (see Figure). The biomass generated, almost a ton per ton of methane consumed, is a co-benefit for use as sustainable protein for fish and animal feed. 

Based on the estimated global methane budget imbalance and the current annual increase of methane in the air, we must capture 15 million tons of atmospheric methane a year to have meaningful impact. With our vision to install these methane bioreactors as standard equipment at landfills, feedlots, composting sites, gas and oil extraction sites and elsewhere — a deployment on the order of 30,000 to 50,000 bioreactors worldwide — there is the capacity to slow global warming by 2050.

Timing

Just a few years ago, the capacity to tackle atmospheric methane in the manner proposed was simply not possible. But today, we have new understanding of how methane is consumed, new strains of bacteria that consume methane at lower concentrations than past strains, new tools for engineering such bacteria, and new bioreactor technology for using low concentrations of methane. The key next step is to develop and demonstrate a prototype methane removal system, using specially developed bacterial strains and optimized bioreactor technology. Once this work is in place, it will serve as the platform for further optimization leading to commercialization. Ultimately, success at scale will require a viable business plan, a commercial manufacturing partner, and an extensive community engagement effort. 

Impact

We are developing technology to remove methane from air at emission sites at scale, decreasing the current rise in atmospheric methane and offering positive environmental impact short term and beyond. If successful, we will buy time for the development and launch of CO2–focused interventions while potentially keeping at bay some of the most devastating near-term impacts of a warming planet. The environmental benefit here is twofold. Not only will the bioreactor approach reduce atmospheric methane, but the end products made from the biomass — e.g., sustainable food-quality protein for use in fish farming and for livestock feed — will further contribute to decreased energy consumption. This co-benefit, coupled to carbon credits, create an opportunity for a financially sustainable and energy-neutral model. In the future, the capability could be extended to lower methane concentrations, to remove methane at near-ambient levels, for instance near wetlands and tundra. 

Funding and Collaborators

National Science Foundation MCB-2223496 and CBET-2218298

  collaborators David Shonnard and Robert Handler, Michigan Technical University

Carbon Technology Research Foundation

  collaborators Jessica Swanson, University of Utah; Amy Rosenzweig, Northwestern University