Hi David, The answer is YES, several TiO2 derivatives have proved to able to oxidize methane into CO2 by photocatalysis at room temperature, but for the moment the more efficient photocatalyst to remove CH4 is a ZnO derivative with 0.1% Ag. Keep in mind that global warming potential of methane GWP20 = 86 and GWP100= 28-32, so transforming CH4 into CO2 reduces its climate change burden.
The first large scale removal of CH4 at climatic relevant scales have been proposed here: - de Richter, R., Ming, T., Davies, P., Liu, W., & Caillol, S. (2017). *Removal of non-CO2 greenhouse gases* by large-scale atmospheric solar photocatalysis. <http://www.sciencedirect.com/science/article/pii/S0360128516300569>" *PECS,* 60 (2017): 68-96. (*Open access*) *GGR => removal of CH4 (and N2O and Montreal gases)* *There is another method to remove CH4 *from the lower troposphere, at a climatic relevant scale => by enhancing the generation of Cl atoms <https://www.earth-syst-dynam.net/8/1/2017/esd-8-1-2017.pdf>. Currently, in the troposphere the major sink for CH4 is the OH° (hydroxyl radical), but Cl atoms remove 2 to 4% of tropospheric methane. In polluted coastal regions, under the marine boundary layer, up to 10-15% of CH4 is destroyed by the Cl atoms (see this reference1 <https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JD025756> and reference2 <http://oceanrep.geomar.de/19720/1/Sommariva-2012-Multiphase%20halogen%20c.pdf>). The advantage of this method is that it also removes surface tropospheric ozone (which is also a GHG). The second large scale removal of CH4 at climatic relevant scales have been proposed here: - Oeste, F. D., de Richter, R., Ming, T., & Caillol, S. (2017). Climate engineering by mimicking natural dust climate control: the iron salt aerosol method. <https://www.earth-syst-dynam.net/8/1/2017/esd-8-1-2017.pdf> *Earth System Dynamics*, *8*(1), 1-54. (Open access) *GGR => removal of CH4*, tropospheric O3, HCFCs, black carbon, and CO2 *Some other GHG-REMOVAL papers published by our team: * - de Richter, R., Ming, T., Caillol, S., & Liu, W. (2016). Fighting global warming by GHG removal: *Destroying CFCs and HCFCs* <https://www.sciencedirect.com/science/article/abs/pii/S1750583616300858>in solar-wind power plant hybrids producing renewable energy with no-intermittency. *International Journal of Greenhouse Gas Control*, *49*, 449-472. - Ming, T., de Richter R., Shen, S., & Caillol, S. (2016). Fighting global warming by greenhouse gas removal: *Destroying atmospheric nitrous oxide* <https://link.springer.com/article/10.1007/s11356-016-6103-9> thanks to synergies between two breakthrough technologies. *Environmental Science and Pollution Research*, *23*(7), 6119-6138. - Kiesgen de_Richter, R., Ming, T., & Caillol, S. (2013). Fighting global warming by photocatalytic reduction of CO2 using giant photocatalytic reactors. <https://www.sciencedirect.com/science/article/pii/S1364032112005680> *Renewable and Sustainable Energy Reviews*, *19*, 82-106. *Related to CO2 Captue, reducing DAC costs by 30% and then performing CCUS.* - *Davies PA, Yuan Q, de Richter R. Desalination as a negative emissions technology <https://pubs.rsc.org/en/content/articlelanding/2018/ew/c7ew00502d/unauth#!divAbstract>. Environmental Science: Water Research & Technology. 2018;4(6):839-50. * Best, Renaud Le lun. 15 avr. 2019 à 16:12, Andrew Lockley <[email protected]> a écrit : > 737 wing span 35m. Surface area therefore about 300m2. Approx 10k planes > flying. Maybe Same number grounded. Total area 6m m2 = 6 sq km = 15x the > mall of America. > > This doesn't merit further discussion. > > Andrew Lockley > > Le lun. 15 avr. 2019 à 15:49, David Sevier <[email protected]> a écrit : > Planes are flying anyway. Titanium dioxide coating can be fractions of a > micron thick and therefore won’t add appreciable weigh. They fly in air > that is cold and which has greater amounts of UV than on the ground. The > cold conditions may favour desired reactions. They also fly quite fast, so > the rate of interaction with gas molecules is high. Whether this makes a > difference or not will depend on the reaction kinetics. > > > > You have jumped to conclusions on this. I don’t know if there is something > here or not. Hence my questions. > > > > Regarding roads and buildings: careful paint design is needed to maximize > gas to surface interaction. I am not convinced this would work for roads > due to wear and recent classifications of titanium dioxide as a cancer risk > when a dust. This is something that anyone thinking of using titanium > dioxide for SRM should bear in mind. > > > > *From:* Andrew Lockley [mailto:[email protected]] > *Sent:* 15 April 2019 14:27 > *To:* David Sevier > *Cc:* geoengineering > *Subject:* Re: [geo] titanium dioxide > > > > Planes have a tiny surface area, big weight penalty and the air is very > thin. Doesn't pass a sniff test. > > > > Using it in building and roadway surfaces is much more likely to work > > > > Andrew > > > > On Mon, 15 Apr 2019, 14:06 David Sevier, <[email protected]> > wrote: > > I am wondering about whether titanium dioxide when electroplated as a film > can be used to decompose methane under ultraviolet light conditions. Can > anyone advice on this? I am seeking to compare this against polycrystalline > titanium dioxide which is known for this. I am also interested to > understand if titanium dioxide can be used to decompose nitrogen oxide and > in particular nitrous oxide under UV light conditions. Again, also to > understand if electroplated films can do this. > > > > A possible application would be to coat planes with titanium oxides. There > might be some useful decomposition effects as they fly through the high > atmosphere under cold bright conditions. > > > > Just to head off any misunderstandings, I am not saying in any way that > this will fully mitigate the effect of the emissions that flying creates > but it might just have a useful *small *effect to reduce them. Hence the > questions. > > > > > > David Sevier > > Carbon Cycle Limited > > 248 Sutton Common Road > > Sutton, Surrey SM3 9PW > > England > > Tel 44 (0)208 288 0199 > > www.carbon-cycle.co.uk > > > > *PLEASE NOTE OUR NEW TELEPHONE NUMBER* > > > > This email is private and confidential > > > > > > [image: Rushlight_commended_Logo_white_2018_19_RGB] > > > > > > > > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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