At IRDL, Jihane Saad explored the reduction of health risks in agricultural methanization through innovative treatments.
Jihane Saad, chercheur·e au sein de IRDL (Institut National Polytechnique de Bretagne).
Thèse soutenue en 2025 à l'école doctorale École doctorale Sciences Pour l'Ingénieur (Lorient ; 2022-....).
Référencée dans le réseau ABES/STAR, cette thèse répond aux critères de rigueur de l'enseignement supérieur français.
Agricultural methanization, although it is a promising solution for the management of organic waste and the production of renewable energy, raises major health concerns. Indeed, the presence of pathogenic bacteria in the effluents resulting from this practice can pose risks to public health. These risks are even more concerning in a context where food security and the health of populations are absolute priorities. The thesis of Jihane Saad aims to evaluate the impact of thermal treatments and pulsed electric fields on the inactivation of pathogenic bacterial strains, notably enterococci and clostridia. These bacteria, often present in agricultural waste, represent a challenge for the sanitary safety of products resulting from methanization, and their management is crucial to avoid harmful consequences on human and animal health.
The preliminary results of this research are revealing and deserve to be highlighted. A significant reduction of 5 log10 of enterococci has been observed, indicating that thermal treatments can be effective in eliminating these bacteria. This discovery is of paramount importance, as it paves the way for safer treatment protocols for effluents resulting from methanization. However, the effectiveness of treatments on other strains, such as C. difficile and C. novyi, has proven limited, with population reductions ranging from 0.7 to 1.6 log10 after post-anaerobic digestion storage. These results underscore the importance of improving hygiene protocols to ensure adequate elimination of pathogens.
It is essential to note that the presence of these pathogenic bacteria in the effluents can have significant practical implications. For example, contaminated effluents can be used as fertilizers in crops, but if not properly treated, they can contaminate soils and crops, leading to health risks for consumers. The research also recommends exploring post-DA storage as a potential method for managing contaminated effluents. This approach could help reduce health risks associated with methanization while allowing for the valorization of animal by-products. Indeed, managing contaminated effluents is crucial to ensure the sustainability of methanization in the current agricultural context.
Decision-makers must therefore take these results into account to develop effective strategies for managing health risks. This involves not only a better understanding of methanization processes but also close collaboration between farmers, researchers, and health authorities. Furthermore, awareness initiatives are necessary to inform farmers about best practices for effluent management, in order to minimize contamination risks.
In summary, this thesis highlights the need to develop more effective treatment methods to ensure the sanitary safety of products resulting from agricultural methanization. The stakes are multiple: it is not only about protecting public health but also about fostering the social acceptability of this practice, which is essential for the energy transition and the management of organic waste. Methanization, as a sustainable solution, must be accompanied by rigorous measures to ensure the safety of products and the health of populations. In the West African context, where waste management and food security are major challenges, this research is particularly important. Indeed, it could contribute to a better integration of methanization into local agricultural systems while ensuring the sanitary safety of agricultural products.
Thus, it is imperative that the results of this research be taken into account in agricultural and environmental policies to promote responsible and sustainable methanization. By integrating this knowledge into agricultural practices, we could not only improve waste management but also strengthen the resilience of agricultural systems in the face of environmental and health challenges.
Données clés
- 5 log10 : Réduction significative des entérocoques grâce aux traitements thermiques.
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Sources et accès
Jihane Saad. Réduction du risque sanitaire en méthanisation agricole : impact des traitements thermiques et électriques pulsés sur les bactéries sporulantes ou non. Génie des procédés. Université de Bretagne Sud, 2025. Français. ⟨NNT : 2025LORIS746⟩. ⟨tel-05515524⟩