About This Project

Soils are the largest terrestrial sink of atmospheric CH4; even small increases in methanotrophy over large areas could contribute significantly to CH4 removal. We will use 13C tracing and microbial assays to determine the potential of pH changes to stimulate atmospheric CH4 oxidation across a range of soil conditions. Our work builds on exciting preliminary results suggesting that increased soil alkalinity could remove up to 5 MMT CH4/y by stimulating high affinity CH4 oxidizers in soils.

Ask the Scientists

Motivating Factor

Methane is a potent greenhouse gas with a 20-year global warming potential approximately 80 times that of CO2 [1]. The atmospheric concentration of CH4 continues to increase at twice the rate of CO2 [2, 3]. Both emissions reduction and atmospheric CH4 removal are needed to help slow climate change [4, 2]. Methane is a short-lived climate pollutant and thus reductions in its atmospheric concentration would have a disproportionately strong impact on limiting near-term warming [5]. Soils are the largest terrestrial CH4 sink removing an estimated 38 Tg of CH4/y [6]. Enhancing the soil CH4 sink by stimulating methanotrophic bacteria could provide a pathway for meaningful atmospheric CH4 removal [7, 8]. Preliminary evidence suggests that methanotrophy can be stimulated by decreasing soil acidity; liming and rock dust amendments could potentially contribute to CH4 removal while providing co-benefits for agricultural productivity and soil carbon sequestration.

Specific Bottleneck

Background rates of CH4 removal are typically low in soils at atmospheric CH4 concentrations [9]. However, soil methanotrophs can be sensitive to pH and evidence suggests that CH4 uptake rates increase as soils become less acidic, particularly in the range of pH 4-8 [Anthony et al. 2025, 11, 12, Vaughan et al. in prep). We found that increasing soil alkalinity significantly enhanced rates of CH4 oxidation at (near) atmospheric conditions. To be able to exploit pH-sensitivity to increase CH4 removal requires a better understanding of the biogeochemistry and microbiology of this dynamic. Specifically we need to determine the range of conditions under which pH-sensitive methanotrophy occurs, and identify the microbial species and mechanisms responsible for the response rate.

Actionable Goals

- Determine the role of key biogeochemical characteristics and processes related to enhanced CH4 oxidation in soils. This will allow us to narrow the conditions that drive increased methanotrophy.

- Determine patterns in CH4 oxidation rates across soils with different physical and chemical properties. This will allow us to begin to narrow conditions that favor or inhibit enhanced methanotrophy and facilitate later modeling and scaling.

- Determine the methanotroph(s) responsible for enhanced CH4 oxidation via metagenomic analyses as well as targeted sequencing and quantification of genes involved in CH4 oxidation (e.g., pmoA and mmoX) as well as broad phylogenetic analyses via 16S/18S rRNA sequencing. With these metagenomic and genomic data, we can then begin to delineate what interactions might exist between methanotrophs and other microbial community members that may facilitate CH4 uptake, as well as develop strategies for the cultivation and isolation of these novel microbes.