Mitigate Nitrous Oxide Emissions

N2O is increasing rapidly in the atmosphere as a result of agricultural emissions. N2O is a powerful greenhouse gas and leads to ozone loss in the stratosphere. While CO2 and CH4 mitigation is actively being pursued N2O has received much less attention.

That’s certainly true. What are the major N2O sources? And would strategies or technologies of its reduction and mitigation vary significantly from others’?

Hey @wennberg, welcome to the Community and thanks for posting about this topic! @TerryMulligan and I actually had done some previous work on designing a competition centered around air pollution, but our main focus at the time was fine particulate matter affecting large metropolitan areas and addressing pollutants like NOx and SOx. N2O emissions as you point out are produced mainly from agricultural operations, and particularly from fertilizers.

Just thinking about loud, do you know of any efforts to innovate for low-to-no emissions fertilizer products/technology? Or is this still a blank space for significant innovation?

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Or, would biochar be relatively close this solving this problem if only it were available at the same price as conventional fertilizers?

This is a bit old but came across this: “Biochar reduces nasty nitrous oxide emissions on farms”

EPA had a relevant theoretical challenge here:
https://innocentive.wazoku.com/#/challenge/4380f517f84f49b78ad3dab8b4657e6e

Wondering if they got clues for reducing N2O emissions, while providing equivalent or better agronomic performance than conventional fertilizers.

Welcome to the community, @wennberg !

One thing I like with this challenge is that it’s “solution agnostic”, meaning that we’re not defining the solution but letting the competitors go through the typological space for potential solutions. Those solutions could range from as far as employing vertical agriculture on a mass scale, to geoengineering the atmosphere to sequester and chelate N2O.

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Hi @carlbozzuto, @KeithDPatch, @josephjjames, @bartc, @hopkepk, @jwangjun - Any inputs that you would like to share on agricultural emissions leading to N2O in the atmosphere, which in turn leads to ozone loss in the stratosphere?

The ubiquitous biological degradation of dead organic matter releases nitrogen in the form of ammonia. When ammonia is released and oxygen is present, autotrophic bacteria rapidly use the ammonia as an electron donor in a process referred to as nitrification. While the majority of the ammonia is converted to nitrite and then to nitrate, both that process and the reverse process (denitrification of nitrate and nitrite to nitrogen gas) release nitrous oxide. From an agricultural perspective the problem isn’t fertilizer, it is excess manure and chemical fertilizer application that is the problem. Years ago I was involved in evaluating a concept of using the nutrient content of treated domestic wastewater to support a hydroponics operation growing calla lilies - in this case a strain that was a nutrient scavenger. However, the agricultural objective was to maximize yield and fertilizer is comparatively inexpensive to the value of the flowers produced, so the grower literally “threw” excess fertilizer to the plants. I also experienced a situation in Denmark where the excess manure application to farm land increased the groundwater nitrate levels so high that the infiltration of groundwater into the sewer “contaminated” the sewage with so much nitrate the biological nutrient removal plant couldn’t function. We can’t eliminate fertilizer application to agricultural lands, but we can develop and follow best practice methods to match application with plant uptake needs, and minimize the potential for nitrous oxide formation associated with excess application. This also means we need to develop inexpensive methods of managing animal manure to match crop needs and avoid excess spreading.

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@AquaDoc -
Regarding your last point about the inevitability of using fertilizer: isn’t there a chance that new technologies would disrupt the need for fertilizer?

For example, this robot uses machine vision in conjunction with autonomous driving and laser, to incinerate ~100,000 weeds an hour. It’s probably not enough to replace weed killers all on its own, but future iterations might be able to do so.

Maybe we can redefine this idea as - “Disrupting fertilizer”?

Perhaps we could eliminate the need for food as well? A little facetious perhaps, but all living things require essential nutrients to survive. You can’t eliminate the need for food (source of energy) and nutrients, or the need for oxygen and water, or respiration that produces gaseous byproducts. What you may be able to do is control excess by examining how nutrients are supplied. For example, the Israelis have invested heavily in methods of miserly applying water to plants to meet growth and food production requirements, and are able to grow crops in the desert. Plants have seasonal variations in the need for nutrients, so matching supply with demand could avoid excess. But eliminating excess won’t stop the release of ammonia - which is a natural process resulting from organic decay - or prevent the formation of nitrous oxide. What we can do is minimize fertilizer application, eliminate manure application to land (as manure is an inefficient means of fertilizer application and inherently results in excess), minimize food waste that results in decay products while recovering energy, nutrients and carbon from what excess food production that is required to accommodate spoilage etc.

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Thank you @AquaDoc for posting this informative and illuminating comment . It’s helping me better understand that the problem is less about what fertilizer is used, but the how and when it is applied (or misapplied) that impacts the environment more

As @AquaDoc mentions, the key is development of methods and associated sensors/feedbacks for properly managing nitrogen inputs in agriculture. Given the costs of fertilizer, there is hope that solutions that mitigate N2O (and NO) production might be economically sustained even in the absence of GHG markets. In addition, reductions in N2O emissions would likely have co-benefits in mitigating air (via NO and NH3) and water (NO3-) pollution.

Thank you for your illuminating answer.

I admit to being a lay person on this subject (if that wasn’t clear already), but I can’t help by wondering: might it be that we could re-engineer plants themselves to minimize nitrous oxide / ammonia release?

Bacteria, not plants, are responsible for release of nitrous oxide through nitrification (oxidation of ammonia) and denitrification (reduction of nitrate and nitrite to nitrogen gas). They are also responsible for extracting nitrogen gas from the atmosphere and making it available for plants, including a symbiotic relationship with legumes, where the bacteria form nodules within the plant roots. This is used by farmers and gardeners to replenish nitrogen in the soil, by allowing an area to go fallow for a year to fix nitrogen. It is also the reason eutrophication in fresh water systems focus on controlling phosphorus, not nitrogen, as the latter is virtually limitless in availability. Where there is organic matter being produced, there is also decay and the production and inevitable oxidation of ammonia.

The atmosphere we breath is roughly 80% nitrogen gas, so it shouldn’t be surprising that lightning can also produce nitrous oxide gas.

Returning to my first comment in this thread, the reason agriculture is the focus of the discussion regarding the formation of nitrous oxide is because it is a point in the nitrogen cycle that we have some control. Farmers don’t want to waste money on increasingly expensive fertilizers, but the cost of fertilizer is comparatively low compared to the value of a crop - so there is a natural tendency to apply excess. Additionally, land application (disposal) of excess manure and the increasing amount of human secondary waste biosolids being produced as developing countries adopt wastewater collection and treatment is probably something that can be tackled by technology, as well as sensors or other means of determining just how much and when to apply fertilizer.

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Might need a more interesting title to generate excitement. Reducing N2O emissions: No laughing matter? … ???

That is funny!

I am not a soil expert. I am aware that bacteria are the real source of N2O production in the soil. I am also aware that N2O is destroyed in the upper atmosphere by photolysis. Ozone plays a small role, but more in the production of N2O from atmospheric nitrogen. N2O is fairly stable, resisting oxidation to NO or NO2 that also occurs due to the oxygen in the atmosphere. While N2O is a much stronger greenhouse gas than CO2 or methane (about 300 times), it has been relatively well mixed in the atmosphere at a concentration of about 0.5 ppm. The very slow oxidation rate seems to provide a very long life in the atmosphere of about 114 years.
All living things have proteins which are composed of polypeptides, which are made from amino acids that contain nitrogen. When these things die, the nitrogen gets converted to ammonia and then some to N2O, as has already been pointed out. More targeted use of fertilizer can help to reduce the total amount of nitrogen in the soil, but there are bacteria that take nitrogen out of the air to make it available to plants. I suspect a more promising approach would be to genetically modify plants to utilize more of the light spectrum to increase photosynthesis. If successful, that would remove more carbon from the atmosphere as well as allow greater food production with less fertilizer.

Thanks @carlbozzuto for sharing your thoughts on this topic. Have you come across any successful case study trying to mitigate N2O?

Thanks, @AquaDoc. I actually understood most of that :slight_smile:

There are a number of wastewater treatment processes developed for biological nutrient removal (i.e. removal of nitrogen and phosphorus) that claim a reduced production of nitrous oxide in comparison to more conventional nitrification/denitrification process designs developed over the past 40 years. For example,

Nitrous oxide emission during wastewater treatment - ScienceDirect; [N2O emission from a partial nitrification–anammox process and identification of a key biological process of N2O emission from anammox granules - ScienceDirect]
(https://www.sciencedirect.com/science/article/abs/pii/S0043135411005707); N2O emission in a partial nitrification system: Dynamic emission characteristics and the ammonium-oxidizing bacteria community - ScienceDirect.
However, it is important to take into consideration the trade-off’s between enhancing one treatment characteristic (in this case reduced N2O emissions) for increased energy consumption (for example) which also has emissions concerns - or other environmental impact considerations. I expect that the amount of nitrous oxide reduction achieved by these alternative tertiary treatment processes is likely insignificant in comparison with the N2O released due to natural organic degradation processes occurring world-wide. Nitrous oxide emissions from wastewater treatment processes | Philosophical Transactions of the Royal Society B: Biological Sciences (royalsocietypublishing.org)

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