N2O geoengineering

[Andrew Lockley]

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 

[Renaud de RICHTER]

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." 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

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[Thomas Goreau]

Complex N2O removal technology may not be needed. There are many simple biological methods to reduce N2O emissions and enhance N2O sinks once the N2O cycle, and its anthropogenic imbalances, are properly understood.

Unfortunately almost all models assume the N2O source is an obligate anaerobic heterotrophic microbial process, denitrification, and the sink is stratospheric photolysis, but in fact the microbial sources and sinks are much more complicated. My PhD thesis, the Biogeochemistry of Nitrous Oxide, found that the source of atmospheric N2O is in fact largely obligate aerobic autotrophic ammonium oxidizing bacteria, and denitrification is the major sink. N2O is thermodynamically the most effective terminal electron acceptor once oxygen is used up, and in anaerobic habitats N2O is completely consumed, not produced! 

Most interestingly, I found that N2O production by all ammonium oxidizing microbes is inversely proportional to oxygen, so the least N2O is produced at atmospheric O2 levels and the most is produced at low traces of oxygen. If composting is purely aerobic, it will produce the least N2O, but once anaerobic sites build up, high N2O production comes from boundary zones around them. 

Ammonium oxidizing bacteria and archea evolved shortly before the great oxidation event 2.2 billion years ago, when oxygen was being produced in the ocean but chemical sinks prevented it building up in the atmosphere. They REQUIRE oxygen but have no defense against oxygen toxicity, so their growth is inhibited at today's levels of oxygen (microaerophilic), and their fastest growth is now on the upper boundary between aerobic and anaerobic environments, where there are only traces of oxygen, just like the methane oxidizing bacteria, to which they are very closely related. Truly anoxic conditions result in very high CH4, but zero N2O, so N2O and CH4 fluxes across the redoxcline boundary (where oxygen goes to zero) are in opposite directions and increasing nitrous oxide sinks increases methane sources.

Composting under fully aerobic conditions is best in my view because it minimizes sources of both N2O and CH4, and maximizes CH4 sinks (but not N2O sinks). This requires turning your compost regularly!

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139
gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
http://www.crcpress.com/product/isbn/9781466595392

Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/CAHodn9-d5AGx1Aje-%2Bs_42HPvjxPSBXHc5_30dPjXvq%2BZLiV4A%40mail.gmail.com.

[Andrew Lockley]

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? 

[Thomas Goreau]

If we continue what we are now doing to turn the ocean into an anoxic dead zone due to global warming and eutrophication, it will become a N2O (and Carbon) sink, but a huge methane and hydrogen sulphide source!

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139
gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
http://www.crcpress.com/product/isbn/9781466595392

Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/E4B78329-7ECB-4AF0-9032-DE71168DCD57%40globalcoral.org.

[Renaud de RICHTER]

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 ...

[austin]

Yes, one of the most effective is to stop it at its source using biochar. Biochar sharply reduces N2O emissions from composting operations, and in soil.

To be clear, this is not a way to capture extant N2O in the atmosphere to reduce it to N2; this is to sharply abate the production and release of N2O from soil and compost.

See this: 

Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions?

https://www.nature.com/articles/srep01732

This paper also found that adding biochar to compost sharply abated the production of methane and N2O, in the range of 80-97%, with the high end being observed when biochar was added along with zeoites.

Biochar for composting improvement and contaminants reduction. A review 

https://www.sciencedirect.com/science/article/pii/S0960852417312117

Since the mechanism of N2O reduction seems to involve electron transfer mediated microbial activity, we (my company, All Power Labs) have a hypothesis that the enhanced electron transfer kinetics of conductive biochar ("geoconductor biochar") should enhance N2O reduction compared to non-conductive biochar. Biochar begins to pick up conductivity when its processing temperature hits 600˚C, but the conductivity rises sharply at 700˚C, and continues to rise until it hits diminishing returns above 800˚C. See this paper on the role of conductivity in dramatically speeding up the electron transfer kinetics among soil microbes:

Rapid electron transfer by the carbon matrix in natural pyrogenic carbon 

https://www.nature.com/articles/ncomms14873

Here's the piece on the chemistry of N2O and its reduction to N2:

 

Understanding Nitrous Oxide – the Greenhouse Gas of Most Significance in Agriculture

https://johnpaulprofessional.com/2014/09/01/understanding-nitrous-oxide-the-greenhouse-gas-of-most-significance-in-agriculture/

Background info: Microbial electron transfer

A huge part of the chemical and metabolic activity of microbes involves processes which cause some of them to accumulate excess electrons, and others to accumulate a deficit of electrons. These charge imbalances bottle-neck their activity, so these microbes actively reach out with microbial wires or nanofilaments called pili, which they use to touch other complementary microbes to transfer electrons:

Surface of living bacteria aids in direct electron transfer through use of network of nanofilaments (pili) that conduct electricity.

https://asknature.org/strategy/pili-direct-electron-transfer/#.W8gosBNKgWo

Extracellular electron transfer via microbial nanowires 

https://www.nature.com/articles/nature03661

 

These pili are made of protein and are materially expensive, slow in conduction, and limited in the number of other organisms they can touch and the distance they can reach. However, by being in contact with a macroscopic piece of geoconductor biochar along with millions of other microbes, they can exchange electrons simply by conducting their electrons into the char, or by pulling the electrons off of the char. (See the article I linked above, Rapid electron transfer by carbon matrix...) This mechanism is extremely rapid compared to pili and compared to redox mediating moieties. The char can even buffer discrepancies in the supply and demand like a capacitor, acting like a geocapacitor.

[Thomas Goreau]

Biochar may physically adsorb N2O (it’s basically activated charcoal), absorb it, but it may also outcompete the ammonium oxidizers by adsorbing ammonium on ion exchange sites before they can.

Ammonium in biochar can be directly taken up by mycorrhizal fungi symbiotic with plant roots, which grow right into biochar particles, biochar adsorbed ammonium provides a direct pathway to the plant, bypassing the mineral soil and the ammonium oxidizing bacteria. 

Thomas J. F. Goreau, PhD

President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139
gor...@globalcoral.org
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
http://www.crcpress.com/product/isbn/9781466595392

Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734

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[austin]

I would like to add one more thing. From this article I previously linked on how N2O relates to the nitrogen cycle, you can see this graphic:

Biochar appears to help stop N2O from two other mechanisms besides merely facilitating reduction of N2O to N2. Very recently, Prof. Johannes Lehmann published a paper on how charcoal captures ammonia by covalently bonding with it. This is worth reading. It would appear that reducing the pool of ammonium available would reduce N2O formation from ammonium:

Fire-derived organic matter retains ammonia through covalent bond formation

https://www.nature.com/articles/s41467-019-08401-z

Also, biochar captures nitrates, and keeps them available for plants as a nutrient. This seems to interpose itself between the pathway from nitrates and N2O on the graphic above.

Plant growth improvement mediated by nitrate capture in co-composted biochar

https://www.nature.com/articles/srep11080