Rheology and Fluid Mechanics for the Valorization of Biowaste through Anaerobic Digestion

Rheological and mechanical characterization of fluids, including heterogeneous biowaste-based suspensions, with the aim of optimizing process control or designing new, more efficient and less energy-intensive industrial valorization processes.

Air injection into a yield-stress fluid to visualize recirculation zones during pneumatic mixing in an anaerobic digester.

Objectives

This research project is part of the national plan for waste reduction and valorization. It aims to understand the rheology and flow behavior of biowaste to facilitate its valorization. The approaches considered include liquid- or thick-phase anaerobic digestion, as well as co-digestion with sewage sludge. These techniques offer significant potential for biogas production, providing substantial energy, agronomic, and economic benefits.

The main objective is to understand the rheological behavior and flow dynamics of these fiber- and/or particle-rich suspensions in non-Newtonian fluid matrices, with a focus on the influence of biowaste composition and structure on these phenomena.

Expected outcomes include the optimization of the operation of existing facilities and the design tools for new processes. Additionally, the results should enhance our understanding of the underlying flow mechanisms, which are essential for improving the efficiency of biowaste valorization processes.

Results

• A large-scale rheometer [1] for the characterization of centimeter-sized heterogeneous suspensions for anaerobic digestion.
• Modeling of flows generated by pneumatic mixing in anaerobic digesters [2–5].
• Measurement protocols and specialized tools for the rheological characterization of sewage sludge [6].

References

1.  V. Ruys, « Rhéologie des résidus agricoles pour un procédé multi-étapes de méthanisation en voie sèche multi-étapes » (2016). Thèse Université Grenoble Alpes.

2.  A. Hojeij, Laurent Jossic, Albert Magnin, Didier Blésès and Stéphane Hattou, “Gas injection in a yield stress fluid.” AIChE J. 66 (4) (2020) e16878.

3.  A. Hojeij, L. Jossic, P. Séchet, C. Bonamy, A. Magnin, S. Hattou, “Experimental study and numerical modeling of mixing by air injection in yield stress fluids using the OpenFOAM software.” AIChE J. 68 (2) (2021) e17442.
4. A. Hojeij, L. Jossic, P. Séchet, A. Magnin, S. Hattou, “Agitation of yield stress fluids by gas injection.” AIChE J. 68 (4) (2022) e17562.
5. L. Jossic, P. Séchet, A. Magnin, A. Hojeij, S. Hattou, “Bubbles morphology, frequency and rising velocity in yield stress fluid under downward gas injection.” Chemial Enginering Journal Advances 16 (2023) 100527.
6. A. Chitanu, “Caractérisation et compréhension de la rhéologie et physique des boues résiduaires et mélanges de biodéchets et boues résiduaires pour leur valorisation en digestion / co-digestion. » Thèse Mocopée.