Abstract
Removing methane from the air is possible, but do the costs outweigh the benefits? This note explores the question of whether removing methane from the atmosphere is justifiable. Destruction of methane by oxidation to CO2 eliminates 97% of the warming impact on a 100-yr time scale. Methane can be oxidized by a variety of methods including thermal or ultraviolet photocatalysis and various processes of physical, chemical or biological oxidizers. Each removal method has energy costs (with the risk of causing embedded CO2 emission that cancel the global warming gain), but in specific circumstances, including settings where air with high methane is habitually present, removal may be competitive with direct efforts to cut fugitive methane leaks. In all cases however, great care must be taken to ensure that the destruction has a net positive impact on the total global warming, and that the resources required would not be better used for stopping the methane from being emitted.This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.
Highlights
Removing methane from the air is possible, but do the costs outweigh the benefits? This note explores the question of whether removing methane from the atmosphere is justifiable
Methane can be oxidized by a variety of methods including thermal or ultraviolet photocatalysis and various processes of physical, chemical or biological oxidizers
Each removal method has energy costs, but in specific circumstances, including settings where air with high methane is habitually present, removal may be competitive with direct efforts to cut fugitive methane leaks
Summary
Scenarios for mitigating climate warming driven by greenhouse gas emissions envisage steep and immediate reductions in atmospheric methane [1]. This paper uses some very simple estimates of the gain and costs of atmospheric methane removal in terms of global warming potential (GWP) (gCO2eq). Methane is naturally destroyed by both chemical and biological processes, including reaction with atmospheric hydroxyl [OH] and chlorine, and by methane-consuming bacteria (methanotrophs) in soil and water This results in a lifetime in the air of 9.1 ± 0.9 years [12]. It may be preferable to dedicate the cost and energy involved in methane removal to the task of stopping methane emissions, which would accomplish the same end result of lessening, halting, or reversing the growth of methane-driven climate warming, or, alternatively, to ignore methane and dedicate all efforts to CO2 removal. The waste CO2 may itself be later removed by atmospheric CO2 capture technologies under investigation elsewhere
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