Camille Mesnil: Converting anaerobic digestion into an "energy transition solution" The case of the revival of anaerobic digestion in Île-de-France 1990-2020

The thesis focuses on the deployment of methanization in the Île-de-France region to shed light on what is at stake in the measures being developed in the name of the "green city." Also known as "anaerobic digestion," this process of breaking down organic matter in the absence of air produces a gaseous mixture and digestate, a type of humus. Its multifunctional nature (waste management, energy production, compost production), its considerable plasticity (in terms of technical intensity, inputs, and uses), and above all the dual environmental promise (as a means of producing so-called renewable energy or as a tool for the circular economy) with which methanization can be associated make it a preferred technique for those interested in environmental issues in the broadest sense.

By analyzing diverse framing, enrollment, and incentive scenarios in the Île-de-France region, as well as the trajectory of different types of assemblies, the thesis demonstrates the primacy of visions and mechanisms that are most compatible with the energy regime, particularly those associated with large gas networks. It also shows that the articulation of waste management and energy production issues is not self-evident and is subject to tensions. Beyond these two issues, the thesis shows the plurality of the "spillover effects" of the development of methanization in environmental (water and soil quality, etc.) and socio-economic (associated agricultural model) terms.