Biogas: Maera, Montpellier's example of local energy at the heart of energy independence

Le blocage du détroit d’Ormuz et ses répercussions sur le GNL qatari, conjugués à l’arrêt de l’approvisionnement en gaz russe depuis la guerre en Ukraine, ont placé l’indépendance énergétique au premier plan. Dans ce contexte, le biométhane produit localement s’impose comme un actif stratégique. La station Maera, à Montpellier, en offre une illustration concrète. Le biogaz Maera illustre parfaitement cette dynamique de production locale de gaz vert.

Biogaz Maera : une station d’épuration qui produit du gaz vert

Le biogaz Maera est produit directement sur le site d’épuration. L’unité de traitement des eaux usées Maera, située à Lattes et gérée par la Métropole de Montpellier, a officiellement mis en service son dispositif de production de gaz vert le 4 juin 2026. Grâce à un chantier de modernisation de 165 millions d’euros lancé en 2023, les eaux usées collectées permettent désormais de produire du biométhane, une énergie locale et renouvelable injectée dans le réseau de GRDF.

Once the works are complete, the plant will produce twice as much energy as it consumes. Each year it will supply the equivalent of 9,000 low-energy (BBC) homes with biogas, as well as 3,000 homes with hot water and heating. Production will ramp up gradually: around 20 GWh by 2028, close to 10% of the gas consumed across the metropolitan area, then 32 GWh in 2029. On a broader scale, Montpellier Métropole plans to connect 45,000 households to its urban heating networks by 2030.

How biomethane is monetised in France

The production cost of biomethane remains on average higher than the market price of natural gas. To make a facility profitable, project developers have several monetisation mechanisms available, which currently coexist but cannot be combined on the same facility.

The state-backed feed-in tariff

Introduced in 2011, the feed-in tariff guarantees facilities producing less than 25 GWh per year a fixed remuneration over 15 years for each megawatt-hour injected (open window). Above 25 GWh per year, projects fall under the tenders organised by the French Energy Regulatory Commission (CRE), introduced in 2024 in line with the 2018 programming law, with a ceiling tariff set by the tender specifications.

Over-the-counter contracts (BPAs)

Biomethane Purchase Agreements (BPAs) are contracts negotiated directly between a producer and a consumer, often an industrial company wishing to green its gas consumption over the long term at a smoothed price. They can be direct or go through an intermediary supplier.

Biogas production certificates (CPBs)

Le cadre réglementaire des certificats de production de biogaz est défini par les pouvoirs publics ; voir le portail de l’ADEME pour les modalités officielles.

Established by the 2021 Climate and Resilience Act and specified by the decree of 6 July 2024, the biogas production certificates reverse the funding logic: it is now the gas suppliers themselves who finance the sector, by surrendering to the State each year a volume of certificates proportional to their sales. The stated objective is to reach 10% biomethane in the networks by 2030.

The obligation trajectory ramps up quickly: from 0.41% of the volume sold in 2026 to 4.15% in 2028, for an estimated cumulative total of 10.4 TWh. In the event of a shortfall, Article L. 446-46 of the Energy Code provides for a penalty of 100 euros per missing MWh, calibrated to stay above the expected market price of a certificate so as to discourage suppliers from preferring the fine to purchasing.

Guarantees of origin (GOs)

Distinct from CPBs, guarantees of origin trace the renewable origin of the gas for the end consumer: an electronic certificate is issued for each MWh of biomethane injected (Article L. 446-18 of the Energy Code). Since 1 October 2023, their registry has been managed by the company EEX. A notable point for a case like Maera: Article L. 446-22 allows a municipality, a grouping of municipalities or a metropolitan authority hosting a facility to receive, free of charge, all or part of these guarantees to certify the local origin of its own consumption — without being able to resell them.

A cost now spread across all consumers

Le modèle économique du biogaz Maera repose sur ce partage. Le prix d’un CPB se forme librement, à l’équilibre entre le coût complet de production du biométhane et la valeur de marché du gaz. Sur la base des coûts constatés en 2024-2025, la CRE estime ce prix d’équilibre autour de 80 €/MWh PCS en 2026, avec une baisse attendue à mesure que la filière gagne en maturité.

Passed on to bills, this mechanism has a concrete effect: for a gas-heated household consuming around 12 MWh per year, the CRE estimates the additional annual cost at close to 8 euros in 2026, then around 79 euros in 2028. Unlike guarantees of origin, which concern only voluntary green offers, CPBs weigh uniformly on all gas offers. Financing biomethane thus becomes the concern of all consumers.

Biomethane, a sovereignty asset

À l’image du biogaz Maera, la production locale renforce l’autonomie énergétique du territoire. Au-delà de sa dimension environnementale, le biométhane local présente un atout stratégique : sa chaîne de valeur — génie civil, technologies d’épuration, matière première — est intégrée sur le territoire, alors que le pays cherche à réduire sa dépendance aux importations de gaz. Le cas Maera illustre comment une infrastructure publique existante peut contribuer, à son échelle, à cet objectif d’indépendance énergétique. Cette dynamique rejoint la structuration plus large du European biomethane market for businesses.