SUEZ And Carcassonne Agglo Inaugurate The Anaerobic Digestion Unit Of The Saint-Jean Wastewater Treatment Plant To Support The Local Energy Transition

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 30th.

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% 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, CoCEO of SUEZ and 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%, 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% 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 3,300 m3. 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.

About Carcassonne Agglo:
Since 2009, Carcassonne Agglo has been responsible for wastewater treatment and, as such, has 73 treatment plants and 922 km of sewerage networks. It has entrusted the management and operation of its sanitation systems to SUEZ under a public service delegation contract for 35 of its municipalities and to EAU RECA under a public service contract for 44 of its municipalities. Each year, approximately 6 million cubic metres of wastewater are treated in the treatment plants before being discharged into the natural environment. For more information, visit www.carcassonne-agglo.f

About SUEZ:
Faced with growing environmental challenges, SUEZ has been delivering essential services that protect and improve our quality of life for more than 160 years. SUEZ provides its customers with innovative and resilient solutions for water and waste services. With 40,000 employees across 40 countries, the Group works with customers to create value over the full lifecycle of their assets and services, and to drive their low carbon transition. In 2023, SUEZ provided drinking water for 57 million people worldwide and sanitation services for more than 36 million people. The Group generated 7.7 TWh of energy from waste and wastewater. In 2023, SUEZ generated revenues of 8.9 billion euros. For more information, visit www.suez.com.