SUEZ and Carcassonne Agglo Inaugurate the Anaerobic Digestion Unit of the Saint-Jean Wastewater Treatment Plant
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 30 April.
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, hence avoiding 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.
The Carcassonne Agglo’s anaerobic digestion benefits from SUEZ’s expertise, which has contributed to build more than 85 percent of France’s sewage sludge methanation capacity. This new project draws on our capacity for innovation – integrating wastewater treatment and methanation technologies – to meet customer needs for sanitation and local energy. Through this long-term partnership with Carcassonne Agglo, which is committed to promoting the ecological transition of its region, we are pleased to provide innovative and sustainable solutions to preserve resources and the environment.
Pierre Pauliac, Interim Co-CEO & Chief Operating Officer Water
Local and sustainable energy production for the region
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. 4,500 MWh of biomethane are produced each year from 60,000 tonnes of sewage sludge, equivalent to the annual consumption of 750 households. The energy recovery from sludge, instead of fossil fuels, avoids the emission of 1,200 tonnes of CO² per year, equivalent to 700 return flights between Paris and New York.
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.
Improving the quality of life for residents
In addition to producing renewable energy, on-site sludge methanation reduces the volume of sludge to be disposed of by 30 percent, 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. The new buildings reflect the architectural features of the older ones and are barely visible from the banks of the river Aude.
Cutting-edge technology backed by SUEZ’s expertise
Built by SUEZ, BONNERY, TOUJA and other local companies, this plant draws on the expertise of SUEZ, which has over 50 years of experience and has built more than 85 percent of France’s sewage sludge methanation capacity.
As the plant’s builder and operator, SUEZ is putting its expertise at the service of Carcassonne Agglo to make it a key tool in the local energy production strategy. The plant uses SUEZ technologies to meet the community’s performance and sustainability objectives:
- A Digelis® Simplex metal digester with a capacity of 3,300m3. This steel biogas digester is based on innovative technology developed by our partner LIPP, which is seamless and bolt-free. It significantly reduces the methanation time while guaranteeing the same durability as a concrete digester.
- A Methanis® Grid biogas treatment unit to separate methane and carbon dioxide. The biomethane obtained is then injected into the local urban gas network.