About This Project

CH4 accounts for ~ 40% of greenhouse gases’ contribution to short-term global warming, making it an attractive target for climate mitigation to reduce near-term warming. However, currently there is no scalable, proven technology exists to capture CH4 from air in the range of 2 - 1000 ppm, and no feasible solution for 2- 200 ppm range. In this project, we aim to develop a proof-of-concept to capture CH4 from air in the range of 100 – 1000 ppm that has the potential for commercialization.

Ask the Scientists

Motivating Factor

CO₂ and CH₄ are the two most important anthropogenic enhanced Greenhouse gases in the atmosphere, contributing to 91% of anthropogenic heating since the industrial revolution, with ~75% from CO₂ and ~16% from CH₄ ¹. While CO₂ removal has seen great advancement and has commercial scale applications available, limited progress has been made for CH₄ removal, especially for non-trackable emissions such as methane released from animal farm, rice paddies and wetland, where the CH₄ concentration in air is very low (2 – 200 ppm).

Atmospheric methane-oxidizing bacteria (atmMOB) constitute the sole biological sink for atmospheric methane, and they play an important role in the carbon cycle on Earth. However, their CH₄ oxidation rate is extremely low, and substantial efficiency improvements over the state of the art are needed to have an economical solution applying atmMOB for methane capture from very dilute concentrations (2 – 200 ppm).

Specific Bottleneck

Methanotrophs grow slower at low CH₄ concentrations because of (1) the energy barrier associated with CH₄ activation and cellular growth and (2) lower CH₄ uptake rates. Under atmospheric concentrations, energy derived from the very low CH₄ uptake rate may not be sufficient to overcome the energy barrier. Specifically, recent research shows that for methanotrophs that can grow on air, both mixotrophic oxidation of atmospheric trace gases (such as H₂ and CO) and a high specific affinity for CH₄ are keys to obtaining sufficient energy to support cellular growth on air ². However, atmMOB that can grow on air are reported to exhibit extremely slow growth on air – it takes 6 -12 months to form a colony.

In addition, the atmMOBs that can grow at 2 ppm CH₄ grow slower than model aerobic methanotrophs at higher CH₄ concentrations. This presents a challenge in preparing the amount of biocatalysts needed for large-scale applications.

Actionable Goals

Desired biocatalysts for methane removal from air should exhibit enhanced growth at very low methane concentrations (2 – 200 ppm) for sustained CH₄ removal, which should be at least 10 folds of the reported atmMOB growth rate. In addition, they should exhibit one of the fastest growth rates at higher (such as 1%) methane concentrations for biocatalyst preparation. Finally, techno-economic analysis should be performed to determine the target growth rate for 2 – 2000 ppm CH₄.