Long green stems with light feathers with brown highlights… Myscanthus plots are not difficult to find around Bernwiller, in Haut-Rhin. Logically, this town of around 1,200 inhabitants located around fifteen kilometers southwest of Mulhouse has a particularity: it was the first in France to use this rhizomatous grass for… heating!
“Originally, we planted them in 1993 with several local farmers to fix the soil,” recalls Mathieu Ditner, the former mayor of Amertzwiller, now merged with the neighbor. “In 2008, we saw a deterioration in the quality of our water at the catchment well. The nitrate level had increased from 20 to 40 mg/l in ten years… We knew that miscanthus did not need any inputs (fertilizers, pesticides) so we put some in the rainwater collection basin . » Or 27 hectares, financed by the water union.
But the idea of using it in the communal boiler only came later. “I had already tried a little with my own culture and it worked with a very good calorific value, 5% higher than wood,” explains the former elected official. So, I suggested it. » And in 2011, the machine was launched. Without anyone regretting it today… “The miscanthus grows back on its own every year and is used in a short circuit, it’s perfect”, appreciates the current councilor, Patrick Baur, between two visits from representatives of communities, regions, towns, villages etc. Everyone came to discover this perennial and inexpensive plant.
“It works perfectly”
Because this is its other big advantage, especially in times of inflation: its price. The municipality has set its purchase from participating farmers at 110 euros per tonne. They do not take care of anything since the harvest, at the end of March and beginning of April, is managed by service providers, as is the storage in two large sheds. At the end of the chain, residents are now billed “0.077 euros” per kilowatt hour. Against at least 0.19 euros for electricity…
“You also have to pay a subscription,” specifies Marie, whose house built a dozen years ago was connected to the heating network some three kilometers long. “It works from September 15 to May 15. I never have more than 100 euros to pay per month. In total, we have a well over 1,500 euros annual bill for around 120 m². It works perfectly, we don’t regret it at all. »
Not all residents were able to benefit from it. “Only those who were close to the main road and this new subdivision,” specifies Patrick Baur, also delighted with the savings made for his municipality. Because the nursery and primary schools, the village hall, the church, the presbytery are connected to it. All via the two boilers, one at the old Amertzwiller and the other in Bernwiller. The latter was specially set up in 2018 in order to burn the majority of the approximately 300 tonnes harvested.
In a simple way: right next to it, a silo accommodates around five tonnes of miscanthus cut into small pieces of around five or six centimeters. Then the strands are automatically brought to the heating body. “A worker comes to refill the silo every two weeks, or even less if it is very cold,” adds the mayor, nevertheless admitting a small flaw to the miracle plant. “It makes a bit of dust, you have to sweep it up afterwards. »
Not enough to cool him down… Better still, he’s looking to increase production. “Sometimes, at the end of the season, we miss some. It would be good if we had around ten additional hectares, at a rate of 10 to 15 tonnes per hectare. We are going to have a meeting in November to see who would be willing to put some on their land. » It will certainly not be with Mathieu Ditner and his son, Jérémy. They have developed another sector for miscanthus, used as horticultural mulch. Before later being burned?