11 décembre 2025
- Valorization of Pig Manure through Hydrothermal Treatment: Investigation of P and N Conversion Dynamics / PhD Defense Carolina Ochoa-Martinez
Doctorante Carolina OCHOA MARTINEZ
Date and location: Thursday, December 11, 2025, at 2:00 PM in the Forum projection room ; Arbois-Méditerranée
Abstract: Global agriculture relies heavily on non-renewable phosphorus (P) reserves and energy-intensive nitrogen (N) fertilizers to sustain crop production. At the same time, intensive livestock farming generates large volumes of liquid effluents rich in organic matter and nutrients, which, if not properly managed, can lead to environmental impacts associated with their discharge.
To address these challenges, hydrothermal treatment of real pig manure was carried out to investigate the influence of operating conditions on P and N conversion and distribution. Comparative experiments were performed across a wide severity range (107–200 °C, 25–95 min to 300 °C, 10–60 min). The resulting solid, aqueous and oil phases were systematically characterized through physicochemical analyses and sequential phosphorus extractions.
Results show that more than 90% of P was recovered in the solid phase. The mineralization of organic P and Al/Fe-bound P dissolution into calcium phosphates was identified as the main mechanism governing P retention in the hydrochar. Temperature emerged as the most influential parameter affecting P conversion and speciation, with strong correlations observed between P forms and the availability of metal cations (Ca, Mg, Fe, Al). Dissolved organic nitrogen remained the dominant N fraction in the aqueous phase, highlighting a major limitation in current hydrothermal valorization strategies.
Keywords: Hydrothermal treatment, pig manure, phosphorus speciation, nitrogen transformation, biocrude, process water recirculation, hydrothermal liquefaction, hydrothermal carbonization.
Jury :
Audrey VILLOT Rapportrice, IMT Atlantique
Magali CASELLAS Rapportrice, Université de Limoges
Boram KIM Examinatrice, INSA Lyon
Stéphan BOSTYN Examinateur, Université d’Orléans
Olivier BOUTIN Examinateur, Aix Marseille Université
Jean-henry FERRASSE Directeur de thèse, Aix Marseille Université
Cristian BARCA Co-directeur de thèse, Aix Marseille Université