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Conséquences de l’introduction de la méthanisation dans une exploitation de polyculture-élevage sur les cycles du carbone et de l’azote. Combinaison de l’expérimentation et de la modélisation à l’échelle de la ferme

Abstract : The anaerobic digestion (AD) of animal effluents is strongly developing in France. It produces renewable energy (biogas). Like undigested effluents, the use of anaerobic digestates in the field enables the recycling of nutrients and organic matter in the soil, which decreases the need for synthetic fertilizers and maintains soil organic carbon stocks. However, the treatment and field application of those organic products can also cause greenhouse gas emissions and contaminants. The on-farm AD nfluences those impacts. In order to control them, we need to understand how the co-digestion of animal effluents with imported organic wastes influences C and N cycles at the farm scale. We studied this question with the support of a case study at INRAE in Nouzilly (Centre – Val de Loire, France): a crop and livestock farm where an anaerobic digester treats the cattle effluents together with imported wastes. During the MetaMetha field experiment, we compared N fluxes during a crop rotation that was fertilized with synthetic N fertilizers, undigested cattle slurry and farmyard manure, or digestates issued from their digestion. We found that digestates can substitute synthetic fertilizers, despite the risk of ammonia (NH3) emissions. Earthworms can be negatively impacted just after the application of digestate of slurry, but the input of organic matter induced similar positive impacts after two years. We then evaluated the STICS and SYS-Metha models to simulate the field experiment, and digestate treatment and storage, respectively. Both models were coupled to simulate C and N fluxes at the farm scale. The models showed that when large amounts of digested wastes are imported, AD promotes substitution of synthetic N fertilizers and storage of soil organic C, but also NH3 emissions. The study enabled us to better evaluate the consequences of the on-farm AD and therefore to optimize the sector.
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Submitted on : Friday, December 17, 2021 - 12:08:32 PM
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  • HAL Id : tel-03485490, version 1

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Victor Moinard. Conséquences de l’introduction de la méthanisation dans une exploitation de polyculture-élevage sur les cycles du carbone et de l’azote. Combinaison de l’expérimentation et de la modélisation à l’échelle de la ferme. Ingénierie de l'environnement. Université Paris-Saclay, 2021. Français. ⟨NNT : 2021UPASB049⟩. ⟨tel-03485490⟩

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