Encouraged by the government, is anaerobic digestion such an ecological green energy?

It was barely a month after the accident. Surrounded by his deputies and councilors, in the hall of the municipal council of Commana, a town of just over a thousand inhabitants in the heart of the Arrée mountains (Finistère), the mayor decided to table a motion, asking “That binding and effective standards be imposed to guarantee environmental safety around industrial and agricultural methanizers, whether they are in service or in the future”. The accident at Châteaulin, a month earlier, was in everyone’s mind.

On this day in August 2020, a leak in a methanization unit in Châteaulin, located by the river, contaminated the water pumped for the distribution of drinking water. West France title “Pollution of tap water affects 180,000 people in Finistère”, and the information circulates the committees of opponents to various projects of methanizers, everywhere in France.

A slap in the face of the industry

Chateaulin began to be cited as an example. In Commana, where a farmer had decided to build a methaniser on his farm, not far from Drennec Lake, a drinking water tower in Finistère. In Néant-sur-Yvel, on the edge of the Paimpont forest (Morbihan) where some were opposed to the project of a local farmer. But also further afield, as in Corcoué-sur-Logne, on the borders of Loire-Atlantique and Vendée, against a project for an “XXL” methaniser, the largest in France.

This accident at Châteaulin was a hell of a slap in the face of the anaerobic digestion industry. However, in principle, anaerobic digestion is all about an ecological process: transforming, thanks to the action of microorganisms, agricultural waste (dung, certain intermediate crops), agrifood or even mowing municipal lawns in gas, electricity, heat, fuel: a good idea to reduce the use of fossil fuels and their share of CO2 emissions that hate the climate.

But of course, nothing is that simple. Because this process involves risks, which the opponents stubbornly stress. There are potential accidents .

Odors and ammonia

There is also the fear that a growing part of cultivated fields in France will be dedicated to energy production, and no longer to food. Currently, the law imposes a ceiling of 15% maximum of food crops to supply a methanizer.

Among local residents, tensions also often revolve around odor nuisance, such as in Quimper where, in September 2017, an industrial methanizer was ordered by State services to stop odorous emissions.

And then there is air pollution, particularly ammonia, linked to the spreading of the material resulting from anaerobic digestion. Brittany is the first region emitting this gas, as proved by figures published by Ouest France in April 2020, confirmed by investigation from the investigative media Splann. A source of fine particles, its high concentration in the air threatens human health.

Senate report and government orders

However, anaerobic digestion remains a solution supported by the government. The Senate carried out a fact-finding mission last spring on “Methanization in the energy mix: challenges and impacts”. A report is expected to be released this fall.

Hearing by the senators, on this occasion, the Minister of Ecological Transition, Barbara Pompili, announced that decrees were being drawn up, aimed at further regulating the practice and preventing the risk of accidents. Here again, Châteaulin was on everyone’s mind. “I say it very clearly: some installations that were not operated with sufficient rigor have damaged the image of anaerobic digestion, she declared. We must therefore better control the risks and nuisances. The incidents of recent years show it clearly: it is about the protection of the environment, as well as the acceptability of projects. “

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