Lisa Stein: Leveraging Methanotrophs for Mitigation and Removal of Methane

Abstract

The short atmospheric retention time and high global warming potential of methane means that slowing its rate of emission, or even removing it from the atmosphere, could potentially slow the increase in global temperature within this century. While the microbial process of methanogensis is the world's primary methane source, technologies that augment microbial methanotrophy offer viable strategies for both methane emissions reduction and atmospheric removal. Some strategies under development that leverage methanotrophs include enclosed bioreactors, soil amendments, tree engineering, and freshwater ecosystem engineering.  Methanotrophic bioreactors show promise at lab scale, but obstacles remain including limitations on methane conversion rates and capacities at low concentrations, materials and fabrication costs, energy and water requirements, and scale-up and deployment for meaningful removal rates that can impact climate change. Soil amendments can reduce methane emissions, but the type of amendment, rate of deployment, and ecosystem heterogeneity are common roadblocks. Tree engineering includes expressing microbial enzymes in leaves for passive atmospheric methane uptake and bark/rhizosphere engineering to augment naturally occurring methanotrophic populations. Freshwater lakes and reservoirs tend to accumulate methane in their anoxic zones, usually due to high nutrient loading from agricultural runoff. When water is released through dam turbines, dissolved methane is aerosolized and becomes a major atmospheric source. Approaches to augment methanotrophy and limit methanogenesis include deployment of constructed wetlands, water column aeration, and sediment amendments. Methanotroph-based strategies all show promise in limiting methane emissions and encouraging atmospheric removal, but no single strategy alone can remove enough methane in a meaningful time frame.

Bio

Dr. Stein is a Professor and Canada Research Chair in Climate Change Microbiology at the University of Alberta in Canada. Her research focuses on the metabolic pathways of nitrogen and methane cycles from molecular to whole-cell to ecosystem levels to predict how and when the greenhouse gases, methane and nitrous oxide, are consumed or released. Understanding the interconnections between the nitrogen and methane cycles enables novel climate change solutions that simultaneously reduce greenhouse gas emissions and maximize production of food, fuels, and material resources for humanity. Dr. Stein is a member of the NASEM committee on Atmospheric Methane Removal, an Editor in Chief of The ISME Journal (since 2020), an elected member of the American Academy of Microbiology (2023), a CAS PIFI Distinguished Scientist (2025), and a recipient of the Killam Excellence in Mentoring award (2022). Dr. Stein works in partnership with industries, NGOs, academics, and governments to translate microbiological solutions towards GHG mitigation in engineered, agricultural, and natural ecosystems.