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Context

Anaerobic digestion of organic residues contributes to the circular bioeconomy by producing both energy and organic fertilizers. Indeed, the anaerobic digestion residue called “digestate” can be spread and used as organic fertilizer for crops soils. The direct spreading of the digestate, especially from agricultural residues, is commonly carried out and considered as fertilizers for crops growth to reduce the costs generated by mineral fertilizers and as organic amendment (Collective scientific expertise INRA-CNRS -IRSTEA, 2014). However, the effect of anaerobic digestion on the quality of organic carbon and residual organic matter (OM) has not really been studied. Moreover, few studies deal with the OM digestate impact on the fertility of crops soil. In fact, during the anaerobic digestion of organic residues, there are 2 types of not biodegraded OM found in the digestates: the exogeneous recalcitrant OM originating from the substrates and the endogenous recalcitrant OM produced by the biological metabolism of bacteria involved. Depending on the nature and quality of the substrates, the variability in terms of quantity and quality of these 2 compartments is unknown, as their fate in crop soil. In this context, this thesis proposal aims at (i) characterizing the processes involved in the biotransformation of OM during the anaerobic digestion of various organic residues (representative of the major biochemical families and variability of the complexity) in order to ( ii) determine the actuators allowing thereafter (iii) to better control and pilot the quality of the OM of the digestates and to (iv) assess the role of the different types of OM generated on soil fertility (biological, chemical and physical). The main goal will be to provide elements to control the anaerobic digestion process according to the agrosystems needs and to the methane production (compromise management) according to a "reverse engineering" strategy.

Keywords

characterization, modelling, organic matter, crops soil

Skills

Process and/or Agronomy Master or engineering school

Conditions

36 months (octobre 2020 – september 2023)

Location

LBE, Narbonne, France

Contacts

Send a CV and a motivation letter to Julie JIMENEZ (julie.jimenez (arobase) inrae.fr) and Dominique PATUREAU (dominique.patureau (arobase) inrae.fr)