Atmospheric removal of methane by enhancing the natural hydroxyl radical sink

Abstract

According to the latest report from the intergovernmental panel on climate change (IPCC), currently, global warming due to methane (CH4) alone is about 0.5°C while due to carbon dioxide (CO2) alone is about 0.75°C. As CH4 emissions will continue growing, in order to limit warming to 1.5˚C, some of the most effective strategies are rapidly reducing CH4 emissions and developing large scale CH4 removal methods. The aim of this review article is to summarise and propose possible methods for atmospheric CH4 removal, based on the hydroxyl radical (°OH), which is the principal natural sink of many gases in the atmosphere and on many water surfaces. Inspired by mechanisms of °OH generation in the atmosphere and observed or predicted enhancement of °OH by climate change and human activities, we proposed several methods to enhance the °OH sink by some physical means using water vapour and artificial UV radiation. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Soil organic matter oxidation by hydroxyl radical: an overlooked route of greenhouse gas production in drylands

“…However, the known pathways for CH 4 production related to ROS, such as those involving Bacillus subtilis and Escherichia coli, are not dominant in desert ecosystems 54 . In addition, •OH is the largest sink for CH 4 , and around 80-90% of global methane is absorbed through oxidation by •OH, while the oxidation of methane by methanotrophic bacteria accounts for less than 10% of methane consumption 55 . The limited microbial source of CH 4 may be rapidly absorbed by •OH.…”

Temperature responses from methane mitigation approaches vary widely due to non-methane impacts

“…Some CH 4 oxidation approaches, such as atmospheric hydroxyl radical enhancement, would target gases in different ratios. The majority of atmospheric hydroxyl radicals oxidize CO molecules, so we also consider an approach in which CO and CH 4 are destroyed at the same rates seen in the bulk atmosphere (5 tons of CO per ton of CH 4 , table 1) [12]. This approach (A3) results in ∼36% more cooling than negative emissions by 2100 (figure 1).…”

Assessing the potential benefits of methane oxidation technologies using a concentration-based framework

“…Another study demonstrated oxidation of 2 ppm CH 4 at ambient temperature through photolysis of chlorine gas into chlorine radicals (t R,99% = ∼350 s) [24]. Other proposals to generate radicals in ways that mimic methane's natural oxidation process include chlorine radicals through iron salt aerosols [25] and hydroxyl radicals through ozone photolysis [23,26,27].…”