Assessing the impact of introducing biobased products intended for methanisation and/or agronomic use on the carbon content of agricultural soils using the Rock-Eval method.

In the face of the climate emergency and for carbon neutrality by 2050, our energy transition is moving towards sustainable development that promotes a largely carbon-free energy mix and soil recarbonization solutions. In the agricultural context, where food security is a major factor, this target is also accompanied by a demand for a massive reduction in the worldwide use of synthetic fertilizers to reduce, in addition to atmospheric CO2, another non-hydrocarbon greenhouse gas, nitrous oxide (N2O). These concomitant demands are leading, among other things, to the adaptation of new agricultural practices involving the application to the soil of an increasingly diverse type of biowaste residues integrating a circular economy perspective, while at the same time promoting mixed agronomic and energy valorization, such as through the methanization sector, which is gradually integrating the injection of biomethane into gas networks. 
The objective of the thesis is therefore (i) to develop a reference Rock-Eval® (RE) method in order to better characterize products derived from first unmodified or slightly modified biomass and second the same biologically (composting, methanization) or thermally (biochar) modified biomass, (ii) to assess their agronomic and methanogenic value and (iii) to better understand the impact of the introduction of biobased products on the organic matter of agricultural soils. The planned research strategy is based on a two-pronged methodological approach. The first is to optimize and validate the Rock-Eval method for the study of ORP from various origins. The second one aims at comparing the agronomic potential and the methanogenic power of these substrates using a coupling RE- Picarro CH4 and CO2 for use in methanization. Finally, the impact of the introduction of biowaste on the organic matter of agricultural soils will be studied through a comparative study of several experimental scenarios including incubations under controlled conditions on bare soil, on soil with ORP input and on soil with digested ORP input.
Keywords Bio-sourced products, Rock-Eval, methanisation, soil carbon, stability, fertility, amendment, IROC, methane potential

• Academic supervisor    Dr Didier KLEIBER, didier.kleiber@purpan.fr, ORCID : 0009-0003-9878-5888
• Doctoral School    ED458 SEVAB, Paul Sabatier (Toulouse)
• IFPEN supervisor    Dr Isabelle KOWALEWSKI, ORCID : 0000-0003-4165-2999
• PhD location    IFPEN, Rueil-Malmaison & Ecole d’Ingénieurs de Purpan, Toulouse (France)
• Duration and start date    3 years, starting in the fourth quarter 2024
• Employer    IFPEN
• Academic requirements    University Master degree in Soil Science, Agronomy, Physico-chemistry
• Language requirements    English level B2 (CEFR) and French A2 (CEFR)    
• Other requirements    Geochemistry (soil OM, chemistry, isotopes), strong interest in laboratory, experimental and measurement techniques

To apply, please send your cover letter and CV to the IFPEN supervisor indicated below.