Numerous semiconductor metal oxides can reduce N2O (some in presence of O2, others without O2), some few exemples of photocatalysts below. * Blyholder, G., & Tanaka, K.* (1971)*. Photocatalytic reactions on semiconductor surfaces. I. Decomposition of nitrous oxide on* zinc oxide*. *The Journal of Physical Chemistry*, *75*(8), 1037-1043. * Ju, Woo-Sung, et al. (*2004*). "The local structures of *silver (I) *ion catalysts anchored within *zeolite *cavities and their photocatalytic reactivities for the elimination of N2O into N2 and O2." *The Journal of Physical Chemistry B* 108.7 : 2128-2133. * Kočí, Kamila, et al. (*2017*). "Photocatalytic decomposition of N2O over *TiO2/g-C3N4* photocatalysts heterojunction." *Applied Surface Science* 396: 1685-1695.
*To answer Andrew's questions: * * will necessary wavelengths get into the chimney? More and more nano-photocatalys are active both with UV and with visible light. Active wavelengths depend of photocatalysts, size, doping agent, etc.The canopy green-house of a solar chimney can be in glass of several qualities, but it can also be made of different plastics like polycarbonate, or very thin ETFE sheet... * how can the system work at night, when bulk air movement is provided by sunlight? By numerous ways. The chimney can work all night long if we add thermal storage (10 cm water pockets). The chimney with heat storage can also provide peak-hours consumption. Other type of chimneys have been developed for coastal areas, where the latent heat of water condensation (or latent heat of water freezing), can be the driving force (no need of sunlight). Other type of chimneys have been developed to use the low grade heat of thermal power plants, often to be used as dry cooling towers, mainly to save water, or in order not to be dependent of rivers water flow rate and temperatures during heat waves and drought episodes. * what are the catalysts that work at night, and what's the evidence for their performance? The photocatalytic system as proposed only work during daytime with sunlight. But low cost and low consumption *UV* leds, diodes, or lamps can be used at night. * why can't you just use TiO2 coating on roads and buildings, which have a larger area? For many reasons, the principal ones are that in *urban areas* there is less constant sunlight illumination on facades, there are multiple shadows on reads, de-acivation of the photocatalyst can happen by other molecules form urban pollution (VOCs, incompletely burned hydrocarbons and fuel, others), acidic pollution can deposit on the alkaline photocatalyst (HNO3, H2SO4,...), ozone, NO and NO2 can occupy the active sites, instead of reduction of N2O to N2 and O2 you can get oxidation ... Le dim. 31 mars 2019 à 19:05, Andrew Lockley <[email protected]> a écrit : > I criticised the chimney (which is inefficient) , not the photo catalyst > approach (which I'm entirely unfamiliar with). > > I have a number of questions > * will necessary wavelengths get into the chimney? > * how can the system work at night, when bulk air movement is provided by > sunlight? > * what are the catalysts that work at night, and what's the evidence for > their performance? > * why can't you just use TiO2 coating on roads and buildings, which have a > larger area? > > On Sun, 31 Mar 2019, 14:22 Renaud de RICHTER, <[email protected]> > wrote: > >> Yes, there is! >> It consits in transforming N2O back into N2 and 1/2 O2 by photocatalysis >> >> Ming, Tingzhen, Renaud de_Richter, Sheng Shen, and Sylvain Caillol. "Fighting >> global warming by greenhouse gas removal: destroying atmospheric nitrous >> oxide thanks to synergies between two breakthrough technologies >> <https://link.springer.com/article/10.1007/s11356-016-6103-9>." >> *Environmental >> Science and Pollution Research* 23.7 (2016): 6119-6138. >> https://link.springer.com/article/10.1007/s11356-016-6103-9 >> >> The article has been abridged by an independent service of the European >> Union located in UK in >> >> http://ec.europa.eu >> /environment/integration/research/newsalert/pdf/nitrous_oxide_removed_atmosphere_generation_renewable_energy_476na3_en.pdf >> >> >> >> Andrew you criticized it on >> >> https://groups.google.com/forum/#!searchin/geoengineering/nitrous >> $20oxide%7Csort:relevance/geoengineering/wfc-qGC-Abs/iWtxCy0iEQAJ >> >> >> _ . _ . _ . _ ._ . _ . >> >> Article abstract >> >> Even if humans stop discharging CO2 into the atmosphere, the average >> global temperature will still increase during this century. A lot of >> research has been devoted to prevent and reduce the amount of carbon >> dioxide (CO2) emissions in the atmosphere, in order to mitigate the effects >> of climate change. Carbon capture and sequestration (CCS) is one of the >> technologies that might help to limit emissions. In complement, direct >> CO2removal from the atmosphere has been proposed after the emissions have >> occurred. But, the removal of all the excess anthropogenic atmospheric >> CO2 will not be enough, due to the fact that CO2 outgases from the ocean as >> its solubility is dependent of its atmospheric partial pressure. Bringing >> back the Earth average surface temperature to pre-industrial levels would >> require the removal of all previously emitted CO2. Thus, the atmospheric >> removal of other greenhouse gases is necessary. This article proposes a >> combination of disrupting techniques to transform nitrous oxide (N2O), the >> third most important greenhouse gas (GHG) in terms of current radiative >> forcing, which is harmful for the ozone layer and possesses quite high >> global warming potential. *Although several scientific publications cite >> “greenhouse gas removal,” to our knowledge, it is the first time innovative >> solutions are proposed to effectively remove N2O or other GHGs from the >> atmosphere other than CO2.* >> >> Keywords >> Greenhouse gas removal Solar chimney power plant Photocatalytic >> reduction Photocatalytic reactor Negative emission technology Cutting down >> atmospheric N2O concentration to protect the ozone layer and lessen global >> warming >> >> >> >> >> Le dim. 31 mars 2019 à 14:52, Andrew Lockley <[email protected]> >> a écrit : >> >>> Is there any literature on N2O geoengineering? I've not seen any, >>> despite searching. >>> >>> It's highly persistent (~century) and has a high GWP (~300). It seems >>> that the principal sink is soil bacteria, which relies on (very slow) gas >>> exchange through the soil surface layer. >>> >>> AFAIK, total mitigation is very difficult (as 3/4 is from agriculture) - >>> although partial mitigation can be achieved by better fertiliser practice, >>> etc. >>> >>> (cross posting due to expertise in soil on the carbon list) >>> >>> Sources https://www.epa.gov/ghgemissions/overview-greenhouse-gases >>> https://www.tandfonline.com/doi/abs/10.1080/00380768.2012.733869 >>> >>> Andrew >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Carbon Dioxide Removal" 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/CarbonDioxideRemoval >>> . >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/CarbonDioxideRemoval/CAJ3C-04ykwqcZ5nip%2Bi3XHeird9FSQeY86hWQcGwTSrFGKY%3DOg%40mail.gmail.com >>> <https://groups.google.com/d/msgid/CarbonDioxideRemoval/CAJ3C-04ykwqcZ5nip%2Bi3XHeird9FSQeY86hWQcGwTSrFGKY%3DOg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> 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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