GHG-R Flagship Destination

Insight at the Interface
A breakthrough in atmospheric methane removal

Team: Richard Zare

Atmospheric Methane Removal using Free Radicals - Atmospheric methane (CH4) concentrations have more than doubled from pre-industrial levels to 1,850 ppb in 2017. Methane, the second most concentrated greenhouse gas in the atmosphere, has a high global warming potential, 120 times larger than CO2 at the time of emission and 28 times larger after 100 years. The short-term impacts of CH4 therefore constitute a serious issue in climate change. The Global Methane Pledge, signed by more than 100 nations at the 2021 COP26, promises to reduce CH4 emissions 30 percent over the next decade. Because CH4 is a symmetric, inert molecule with no dipole and high activation energy, no sorbent can capture or separate it; therefore, atmospheric methane removal technologies do not exist. However, it may be possible to reduce the 20-year global warming impact of methane by 99 percent by oxidizing it to CO2. Most methane sources have concentrations between 10 and 2,000 ppm, while the atmospheric background concentration is around 2 ppm. The goal of this project is to develop room temperature water microdroplets-based strategies to remove dilute methane (down to 2 ppm) using the hydroxyl radicals. Our strategy is to convert dilute atmospheric methane to products with decreased greenhouse effect, such as CO2 and oxygenated methane derivatives, such as methanol.

Two approaches will be examined and evaluated, each taking advantage of our demonstration that hydroxyl radicals (•OH) are formed spontaneously at the air-water interface. The first approach will involve spraying water into air containing methane, the second approach will involve bubbling air containing methane into water. Our ultimate goal is to find an approach that can be operated at scale to remove methane at low concentrations, on the order of 2 ppm, from air.