SUEZ and Carcassonne Agglo inaugurate AD unit at wastewater plant

SUEZ and Carcassonne Agglo have inaugurated an anaerobic digestion unit at the Saint-Jean wastewater treatment plant in Carcassonne, France.
The plant produces 4,500 MWh/year of biogas from 60,000 tonnes of sewage sludge, which is injected into the public natural gas network to replace fossil fuels.
This avoids the emission of 1,200 tonnes of CO2 equivalent.
This large-scale project for the region's ecological transition is part of Carcassonne Agglo’s Green Pact.
Launched in late 2024, the biogas unit of the Saint-Jean wastewater treatment plant is part of Carcassonne Agglo's Territorial Climate, Air and Energy Plan (PCAET).
The objectives are to create local, sustainable energy loops from wastewater residues and to accelerate the region's energy transition.
In addition, the anaerobic digestion facility is equipped with photovoltaic panels on the roof, producing 10,000 kWh/year of renewable energy to contribute to the power supply and security of the facility.
In addition to producing renewable energy, on-site sludge methanation reduces the volume of sludge to be disposed of by 30%, which cuts down on truck traffic and improves the quality of life for residents.
Furthermore, the sludge is stabilised to make it inert, and all flows are treated in a new Azurair deodorisation unit to control and prevent potential odour episodes.
Finally, particular attention was paid to the architectural integration of this new facility into the surroundings, said SUEZ.
The new buildings reflect the architectural features of the older ones and are barely visible from the banks of the river Aude.
To date, SUEZ has contributed to the building of more than 85% of France's sewage sludge methanation capacity, said the organisation.
This new project draws on its capacity for innovation – integrating wastewater treatment and methanation technologies – to meet customer needs for sanitation and local energy, it added.
Through this long-term partnership with Carcassonne Agglo, which is committed to promoting the ecological transition of its region, SUEZ said it is pleased to provide innovative and sustainable solutions to preserve resources and the environment.
Christian Pouget, Prefect of the Aude department, Régis Banquet, President of Carcassonne Agglo, Vice-President of Intercommunalités de France and Mayor of Alzonne, and Pierre Pauliac, Co-CEO of SUEZ and Chief Operating Officer Water, inaugurated the Saint-Jean wastewater treatment plant's anaerobic digestion unit on April 30.