Methaniser illustration -

G.VARELA / 20MINUTES

  • Régaz Bordeaux has just won the operation of the Hourtin gas network in the Médoc, which will be carried out using biomethane produced in an anaerobic digestion plant.

  • The share of biomethane in the Régaz network is only 1% at present, but could reach 7 to 10% within four years.

  • Its defenders put forward a virtuous energy, but its detractors warn of too rapid development in France in recent years.

The inhabitants of the commune of Hourtin in the Médoc, will be able to benefit from natural gas by 2023. The Departmental Syndicate of Electricity of Gironde (Sdeeg) has in fact just entrusted Régaz Bordeaux with the construction, the operation and development of natural gas distribution networks in the municipality.

This will be an extension of the network already operated by Régaz in the neighboring town of Saint-Laurent-Médoc, with the particularity that this gas will not be fossil gas imported from abroad, but biomethane manufactured locally in the factory. methanization.

Régaz aims to significantly increase the share of this biomethane in its network over the next few years.

Explanations.

Who manufactures biomethane in Gironde?

To date, only two factories, located in the Médoc, manufacture biomethane: Médoc Biogaz since 2019, and Médoc Energie in Hourtin since February 2020. The first already supplies the municipality of Saint-Laurent-Médoc, the second will supply that of Hourtin.

If these municipalities can thus benefit from 100% biomethane in summer, in winter, on the other hand, "this share falls to less than 50% due to increasing consumption," specifies Géraldo Alves, director of project management at Régaz. Bordeaux.

The natural gas which feeds the rest of our network, and which is imported from Russia, Norway, the Netherlands and Algeria, is then mixed with biomethane to meet these peaks in consumption.

"

What is the share of biomethane in the Régaz network?

Biomethane represents around 1% of the gas distributed on the Régaz network, which supplies 46 municipalities in the Gironde.

With the upcoming projects of anaerobic digestion plants in the department, “the objective is to distribute 7 to 10% within four years, announces Geraldo Alves, without counting the biomethane coming from outside and which will be injected into the gas transmission network, which will therefore be added to local production.

"Among the future projects," Médoc Biogaz will build a new unit in June 2021 still in Saint-Laurent-Médoc, there will be another one south of Saint-Jean-d'Illac, then one on the wastewater treatment plant de Bègles with Bordeaux Métropole, a fourth near Bassens and a fifth in the town of Lanton.

"

In 2019, 32 anaerobic digestion units had already been subsidized throughout Nouvelle-Aquitaine and 39 deposits were identified by 2050.

What exactly is a biogas plant?

The principle of an anaerobic digestion plant is to digest organic matter: this can be sludge from wastewater treatment plants, canteen, agro-industrial or agricultural waste, or intermediate crops for energy (CIVE).

“It is the bacteria that degrade this organic matter that produce biogas,” explains Géraldo Alves.

This is made up of carbon dioxide (CO2) and methane.

Before distributing this gas in our network, its 50% CO2 must be removed from it, as well as sulfur dioxide, we then purified this biogas and transformed it into biomethane.

This is why it is more correct to speak of biomethane than of biogas.

»The degraded material is then spread over the land, and acts as a natural fertilizer.

The Médoc Energie facility in Hourtin was sized to process 65,000 tonnes of inputs each year, mainly waste from farming (vegetable waste from the station, cereal waste, pig slurry, etc.) and used vegetable oils.

Médoc Biogaz, for its part, recovers 10,800 tonnes of Cive (mainly silage corn and rye.)

What are the advantages of these anaerobic digestion plants?

The gas produced locally from Cive and agricultural waste is 100% renewable energy, assure its promoters, Régaz and Sdeeg.

“It contributes to the development of the economic activity of farmers, they continue, and the biomethane sector contributes to the development of a circular economy anchored in the heart of the territory and generates local jobs that cannot be relocated.

"

Are these biogas plants a danger?

When it comes to large units, as is the case for the largest project in France, MéthaHerbauges located near Nantes, which plans to treat 560,000 tonnes of animal waste and 120,000 tonnes of plant crops, local residents are worried about the consequences (noise, odors, etc.).

And in particular the daily traffic of trucks which transport the material.

We also remember that last summer, the overflow of a digestate tank at the Kastellin biogas plant in Finistère, caused water pollution, depriving some 180,000 people of drinking water for several days.

The Eaux et Rivières de Bretagne association denounces "numerous incidents in methanizers" and is worried about methanization "which is developing at full speed in recent years in France (...) with large amounts of public money.

"

Is biomethane cheaper than fossil gas?

Far from there.

To extract fossil gas, "you just have to dig a hole, while biomethane has to be manufactured" summarizes Géraldo Alves.

Consequence: when the cost of fossil gas is around 20 euros per MW / h, that of biomethane is more of the order of 100 euros.

In particular, the investments made for the construction of factories, in the order of 5 million euros for those in the Médoc, must be made profitable.

Biomethane benefits from a feed-in tariff, on the same principle as photovoltaic electricity, and the price difference with fossil gas is supported by a tax paid by all consumers.

Planet

Finistère: The methanizer causing pollution authorized to restart

Planet

Brittany: After pollution, agriculture defends its taste for anaerobic digestion

  • Gas

  • Methanization

  • Aquitaine

  • Agriculture

  • energy

  • Bordeaux