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Some numbers to start

Between 2005 and 2016, global GHG emissions increased by 19.3%, from 38,679 to 46,141 megatons of carbon dioxide equivalent (Mt CO2 eq).

In 2017, GHG emissions generated by human activities represented the equivalent of 53.5 billion tons of CO2 (Gt CO2 eq), of which 75% was CO2. Between 1990 and 2017 these emissions had increased by more than 60%. China accounts for almost 30% of emissions, the United States for 14% and the European Union for 10%. On a global average, emissions per capita are five tons of CO2 per year, or 15% more than in 1990.

In Canada, total greenhouse gas (GHG) emissions from all activities in 2018 were 729 megatons of carbon dioxide equivalent (Mt CO2e).

Types of GHGs

The Kyoto Protocol lists six greenhouse gases generated by human activities. Three of these gases account for 98% of the adverse effects on the atmosphere

CO2 or carbon dioxide (79%), CH4 or methane (14%), and N2O or nitrous oxide (5%). The three other gases are HFCs or hydrofluorocarbons, PFCs or perfluorocarbons and finally SF6 or sulfur hexafluoride. Of course, these are not the only air pollutants. For example, ammonia is considered an air pollutant. It combines in the atmosphere with sulfates and nitrates to form secondary fine particles (PM2.5).

– Carbon dioxide (CO2) from industrial activities comes mainly from fossil fuels or from industries such as cement. Massive deforestation also affects the generation of carbon dioxide, as it is no longer captured by photosynthesis.

– Methane (CH4) emissions come from livestock farming, hydrocarbon production, certain intensive crops such as rice, and the decomposition of organic matter.

– N2O or nitrous oxide is released during chemical processes, such as nylon production, or from the use of nitrogen-based products (fertilizers, manure, slurry and crop residues).

GHGs and agriculture

Globally about a quarter of GHG emissions are attributable to the various activities of agriculture. In 2014, they accounted for 10 to 12 gigatons of CO2 equivalent, or 24% of global emissions.

The main greenhouse gases emitted by agriculture are methane (CH4) and nitrous oxide (N2O).

Methane has a warming power 28 times higher than carbon dioxide (CO2), while nitrous oxide has a warming power 310 times higher than carbon dioxide

Enteric digestion of livestock represents a significant portion of agricultural GHG emissions, particularly methane. We should also mention the emissions during the storage, through the anaerobic digestion process, and the spreading of manure and slurry, as well as the application of fertilizers, which in 2011 represented some 13% of agricultural GHG emissions.

Type of animal CH4 emission factor , in kg CH4/head/year
Dairy cows 27,8
Dairy heifers 19,1
Bulls 3,3
Steers 1,6
Piglets 1,66
Pigs 6,48
Sows 7,71
Boars 6,4
Source: http://legisquebec.gouv.qc.ca/fr/ShowDoc/cr/Q-2,%20r.%2046.1

CH4 emissions from manure storage and spreading

Nitrous oxide emissions occur during the nitrification and denitrification of the nitrogen contained in manure. In Quebec and Ontario, we consider an emission capacity of 0.012 kg of nitrous oxide per kilogram of manure.

Canadian Agriculture and GHGs

Canadian agricultural activities account for 12% of GHG emissions in Canada.

Emission sources can be classified into three main categories:

– Nitrogen fertilizer sources

– Livestock sources

– Sources related to the use of fossil fuels (farm machinery, various vehicles, including those used to transport manure),

Nitrogenous fertilizers are, in large part, responsible for N2O emissions from the soil, and by their industrial production method. The increase in GHG emissions from the agricultural sector is mainly due to the production and use of nitrogen fertilizers.  Fertilizer-related GHG emissions increased by more than 50% between 1990 and 2017, and the amount of nitrogen fertilizer used in Canada has doubled since 1993.

Synthetic fertilizers and GHGs

The manufacture of nitrogen fertilizers emits mostly CO2, while their application to fields emits mostly N2O. Approximately 28% of all GHG emissions from the Canadian agricultural sector come from the production and application of nitrogen fertilizers.

Synthetic nitrogen fertilizers are synthesized through a process that requires nitrogen and hydrogen.  The manufacture of synthetic fertilizers generates a significant amount of greenhouse gases.

Agricultural input type Nutrient unit kg CO2/ Kg nutrient unit
Ammonia anhydrous kg N 2,97
Ammonitrate 33.5 kg N 5,86
Nitrogen solution kg N 5,01
Urea kg N 3,69
Ternary fertilizer (N-P-K) kg N, kg P205, kg K20 5,29 – 0,94 – 0,51
Medium N fertilizer kg N 5,34
Medium P fertilizer kg P205 0,57
Medium K fertilizer  kg K20 0,45

 

Source: Arvalis, Institut du Végétal, recognized by the French Ministry of Agriculture and the French Agency for Ecological Transition.

Solugen, drastic limitation of GHG emissions

The storage of liquid manure in pits is a major source of methane emissions. In this anaerobic environment, volatile solids, undigested elements of the feed, are transformed into methane by bacteria.   During the spreading process, nitrous oxide is emitted. The process developed by Solugen to treat contaminated effluents applies to pig manure and allows the treatment of animal excrement to extract pure water and fertilizers.

The technology works on an energy efficient distillation principle based on the use of electricity, heat recovery by thermal transfer, and steam recompression. 30 to 35 kWh are sufficient to treat one cubic meter of slurry.

By treating the slurry directly from the pre-pit, it is no longer necessary to store it in a pit. Furthermore, during the process, the manure is divided into a solid fraction, which represents about 10% of the initial volume of manure, and a liquid fraction which, after treatment, will be broken down into pure water, a concentrated potassium bioliquid and a nitrogenous fertilizer solution.

It is estimated that 90 to 95% of the GHGs normally emitted during storage and spreading of liquid manure are thus eliminated. For a farm that produces 10,000 m3 of manure annually, this reduction represents some 572 t C02 eq.

Thus, not only does the process revolutionize conventional manure management by treating animal waste to extract water and considerably reduce GHG emissions, but it also provides agriculture with a much sought-after fertilizer solution, since its active ingredient, ammonia nitrogen, is normally lost to crops because in its gaseous form it volatilizes rapidly and in large proportions into the atmosphere.

Considering the reduction of GHG emissions mentioned above, we can logically conclude that the production of this nitrogen fertilizer solution does not generate a carbon footprint.

Sources

https://perspective.usherbrooke.ca/bilan/servlet/ComprendreContexteGES?codePays=bfa

https://www.nfu.ca/wp-content/uploads/2020/02/GES-du-secteur-agricole.pdf

https://www.sciencedirect.com/science/article/abs/pii/S0176161713003611

https://fertilisation-edu.fr/nutrition-des-plantes/le-role-des-elements-nutritifs/potassium.html

https://www.environnement.gouv.qc.ca/changements/ges/guide-quantification/index.htm

https://reseauactionclimat.org/wp-content/uploads/2017/09/agriculture-emissions-indirectes-engrais-azotes-mineraux-rac-2017-09-11-final.pdf

https://www.terre-net.fr/actualite-agricole/economie-social/article/les-engrais-une-fausse-solution-pronee-par-les-fabricants-face-au-rechauffement-202-113523.html

https://www.canada.ca/fr/environnement-changement-climatique/services/indicateurs-environnementaux/emissions-gaz-effet-serre.html

http://espace.inrs.ca/id/eprint/1890/1/T000549.pdf

https://www.sciencedirect.com/science/article/abs/pii/S0176161713003611

https://fertilisation-edu.fr/nutrition-des-plantes/le-role-des-elements-nutritifs/potassium.html

https://www.environnement.gouv.qc.ca/changements/ges/guide-quantification/index.htm

https://www.agr.gc.ca/fra/agriculture-et-environnement/pratiques-agricoles/changements-climatiques-et-agriculture/gaz-a-effet-de-serre-et-agriculture/?id=1329321969842

https://www.worldometers.info/co2-emissions/

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