Do Soil Methanotrophs Really Remove About 5% of Atmospheric Methane?

It has been experimentally proved that microorganisms in soils are able to remove atmospheric methane (CH4), particularly through experiments with radioelements such as 14CH4. However, a curious question arises: are these microorganisms the only responsible sink for all atmospheric CH4 uptake attributed to soils, or do non-microbial (e.g., chemical) processes also contribute part of it? In this perspective article, we propose that atmospheric methane removal (AMR) in soils may result from a combination of microbial and non-microbial processes. In addition to oxidation by MOB, we analyzed the potential roles of photocatalytic reactions on soil minerals, Fenton-like chemistry in water droplets, chlorine radical pathways in chloride-rich soils and ozone/VOCs-driven •OH generation. These chemical mechanisms may act independently or intertwined with microbial activity under specific environmental conditions. We suggest that future studies use experimental approaches to explore and quantify the relative contributions of these pathways and to help refine our understanding of the soil CH4 sink in the global methane budget.