Enhanced Atmospheric Methane Oxidation
Atmospheric Methane Removal (AMR) 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.[1] Methane is the cause of about 30% (0.5 °C) of current global warming,[2] it is the second most important greenhouse gas.[3] Global methane emissions approached a record 600 Tg CH4 yr−1 in 2017.[4]
Atmospheric Methane Oxidation is a natural process which occurs in the atmosphere under sunny conditions in the presence of a catalyzer. The process oxidizes methane (CH4) into carbon dioxide (CO2) and water (H2O).[5]
CH4 + 2 O2 => CO2 + 2 H2O
The catalyzer, in 95% of all cases, is •OH, in 1-5% of all cases Iron(III) chloride (FeCl3).[6]
Oxidation of natural atmospheric methane by FeCl3 has been shown in field tests conducted in the North Atlantic in 2023.[7]
Chemistry of Atmospheric Methane Removal
Chlorine atoms are produced, for example, by photolysis from the FeCl3 stemming from iron-containing airborne dust aerosol particles, e.g. from the Sahara,[7] 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 oxidizes naturally to CO2 and water:
3.5O2 + 2oCH3 à 2CO2 + 3H2O
In AMR the catalyzer Iron(III) chloride (FeCl3) is used because chlorine atoms (radicals) oxidize methane at least 16 times faster than OH[5]. The impact of chlorine chemistry on the atmosphere due to pollution is well documented.[8]
Additional Benefits
Fine particles dispersed in the atmosphere can serve as Cloud Condensation Nuclei and thereby cause Marine Cloud Brightening.[9]
Eventually all FeCl3 particles are washed out of the air and hit land or water, where they dissolve into iron compounds and salt. Therefore EAMO would contribute to Iron Fertilization (OIF).[5]
References
- ↑ Euan Nisbet (August 14, 2023). "Rising methane could be a sign that Earth's climate is part-way through a 'termination-level transition'". The Conversation.
- ↑ "Methane and climate change". IEA (2022), Global Methane Tracker 2022, IEA, Paris. Unknown parameter
|url-status=ignored (help) - ↑ Tingzhen Ming, Wei Li ... (15 January 2022). "Perspectives on removal of atmospheric methane". Advances in Applied Energy. 5: 100085. doi:10.1016/j.adapen.2022.100085. Unknown parameter
|s2cid=ignored (help) - ↑ Robert B. Jackson, Sam Abernethy ... (2021). "Atmospheric methane removal: a research agenda". Philosophical Transactions A. 379 (2210). Bibcode:2021RSPTA.37900454J. doi:10.1098/rsta.2020.0454. PMC 8473948 Check
|pmc=value (help). PMID 34565221 Check|pmid=value (help). - ↑ 5.0 5.1 5.2 Franz D. Oeste, Renaud de Richter, Thingzhen Ming (2017). "Climate engineering by mimicking natural dust climate control: the iron salt aerosol method"". Earth System Dynamics. 8 (1–54): 1–54. Bibcode:2017ESD.....8....1O. doi:10.5194/esd-8-1-2017.CS1 maint: Multiple names: authors list (link)
- ↑ Allan W., Hamish Struthers, D.C. Lowe (Feb 22, 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. 112 (D4). Bibcode:2007JGRD..112.4306A. doi:10.1029/2006JD007369.CS1 maint: Multiple names: authors list (link)
- ↑ 7.0 7.1 Maarten van Herpen ... (2023). "Photocatalytic chlorine atom production on mineral dust–sea spray aerosols over the North Atlantic". PNAS. 120 (31): e2303974120. Bibcode:2023PNAS..12003974V. doi:10.1073/pnas.2303974120. PMC 10400977 Check
|pmc=value (help). PMID 37487065 Check|pmid=value (help). - ↑ Baker, A., Sauvage, C., Thorenz, U. ... (15 November 2016). "Evidence for strong, widespread chlorine radical chemistry associated with pollution outflow from continental Asia". Nature - Scientific Reports. 6 (36821): 36821. Bibcode:2016NatSR...636821B. doi:10.1038/srep36821. Unknown parameter
|s2cid=ignored (help)CS1 maint: Multiple names: authors list (link) - ↑ 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). Atmospheric Chemistry and Physics. 23 (1677–1685): 1677. Bibcode:2023ACP....23.1677M. doi:10.5194/acp-23-1677-2023.CS1 maint: Multiple names: authors list (link)
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