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Atmospheric Methane Removal
[edit]Definition
[edit]Atmospheric Methane Removal[1] is a proposed method to enhance the natural process of atmospheric methane oxidation. It is a case of biomimicry.
Atmospheric methane has increased since pre-industrial times from 0.7 ppm to 1.9 ppm[2]. Methane is the cause of ca. 30% (0.5 °C) of current global warming[3]. Global methane emissions approached a record 600 Tg CH4 yr−1 in 2017[1]
Atmospheric Methane Oxidation is a natural process which occurs in the atmosphere under sunny conditions in the presence of a catalyzer[4]. The process oxidises methane (CH4) into carbon dioxide (CO2) and water (H2O).
1 CH4 + 2 O2 => 1 CO2 + 2 H2O
The catalyzer, in 95% of all cases, is •OH, in 1-5% of all cases Iron(III) chloride (FeCl3)[5].
The occurrence of natural atmospheric methane oxidation by FeCl3 has been shown in field tests in 2023[6]
Chemistry of Methane Removal
[edit]Most atmospheric methane is removed in nature by OH radicals. Chlorine atoms are produced, for example, by photolysis from the FeCl3 stemming from iron-containing airborne dust aerosol particles in the oceanic boundary layer:
FeCl3 + hv à FeCl2 + oCl
Methane oxidation is initiated by the chlorine atoms:
CH4 + oCl à HCl + oCH3
The resulting methyl radical is unstable and oxidises naturally to CO2 and water:
3.5O2 + 2oCH3 à 2CO2 + 3H2O
In EAMO the catalyzer Iron(III) chloride (FeCl3) is used because chlorine atoms (radicals) oxidize methane at least 16 times faster than OH[4]. The impact of chlorine chemistry on the atmosphere is well known[7].
Additional Benefits
[edit]Fine particles dispersed in the atmosphere can serve as Cloud Condensation Nuclei and thereby cause Marine Cloud Brightening [8]
Eventually all FeCl3 particles are washed out of the air and fall on land or water, where they dissolve into Iron compounds and salt. EAMO would contribute to Iron Fertilization (OIF) of both the sea and the land [4]
Literature
[edit]- ^ a b "Atmospheric methane removal: a research agenda". Phil. Trans. R. Soc. A 379: 20200454.
- ^ "Rising methane could be a sign that Earth's climate is part-way through a 'termination-level transition'".
- ^ "Methane and climate change".
- ^ a b c Franz D. Oeste, Renaud de Richter, Thingzhen MIng. "Climate engineering by mimicking natural dust climate control: the iron salt aerosol method". Earth System Dynamics, 8, 1-54, doi: 10.5194/esd-8-1-2017.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Allan, W. (Feb 2007). "Methane carbon isotope effects caused by atomic chlorine in the marine boundary layer: Global model results compared with Southern Hemisphere measurements". Journal of Geophysical Research Atmospheres. 112 (D4).
- ^ van Herpen, Maarten. "Photocatalytic chlorine atom production on mineral dust–sea spray aerosols over the North Atlantic". PNAS 2023 Vol. 120 No. 31.
- ^ Baker, Angelika. "Evidence for strong, widespread chemistry associated with pollution outflow from continental Asia". Scientific reports, 6, 36821, doi: 10.1038/srep36821 (See table 2, page 4).
- ^ Gerald G. Mace, Sally Benson , Ruhi Humphries, Peter M. Gombert, and Elizabeth Sterner (1 February 2023). "Natural marine cloud brightening in the Southern Ocean" (PDF). Atmos. Chem. Phys., 23, 1677–1685, 2023.
{{cite journal}}: CS1 maint: multiple names: authors list (link)