In Brest, a company transforms mud into materials for design and architecture

A mechanical arm plunges into the port of Landerneau (Finistère) to dredge the Elorn. Last fall, the city lived to the rhythm of the tides and dredging. Here, as in most ports of the Breton estuaries, the river no longer flows as before. So, the city invested in this painstaking work which is repeated tirelessly. This time, several thousand cubic meters of silt were extracted. A fraction found space, at the beginning of January, in the Gwilen hangar-workshop, in Brest.

A scientific study published in theAcademic Journal of Engineering Studies, in 2022, the total number of tonnes of silt dredged each year in ports in France will be 30 million. This represents “more than 70% of the annual budget of major seaports”, according to the open access journal. The vast majority is discharged offshore, thus affecting the environment: impact on water quality, marine protected areas, etc. The rest is stored on land in expensive and saturated sites. For example, 50,000 m3 lie dormant near Morlaix (Finistère), 70,000 m3 in Vannes (Morbihan).

Innovative decor

The Gwilen company – the name of the river “Vilaine” in Breton – was born from this observation. Yann Santerre, its founder, has heard about this situation since his childhood. “Near my home, the installation of a dam in the Vilaine estuary, fifty years ago, accelerated the siltation of the river,” testifies the thirty-year-old. The idea of ​​finding an outlet for this unused material – considered waste once on land – came to him after his architecture studies and his engineering course at Ponts et Chaussées. In 2017, he experimented with transforming vases into decorative materials in his kitchen. His business was born three years later with the help of his partner and friend, Mathieu Cabannes. The workshop soon produced floor tiles, wall tiles, but also coasters, table and serving trays.

Three employees are busy in the workshop this winter afternoon. A cart moves under the blue eyes of Léopold Leteurtrois. On the floors, molds filled with an indefinable gray substance jiggle. “I pass them on the vibrating table to remove any porosities that could form as they dry,” explains the materials science and engineering student. The smoothed blocks will go to a heating room for twenty-four hours. The time it takes for the compound to solidify.

With his eyes fixed on a table covered with colored tiles, Antoine Lomenech prepares the exhibition samples. “Sometimes we see a shell or grains of sand on the surface,” marvels the 29-year-old worker, a graduate of the École supérieure supérieure d’art de Bretagne with a transitional design option.

Towards the blue economy

The objects designed here are currently used indoors, which architects are fond of. But the team is studying exterior and substitutable applications so that builders and project managers can replace traditional polluting materials which require cooking at high temperatures and use limited resources: terracotta, concrete, etc.

This requires a long phase of research and development overseen by Guillemette Cardinaud. “We carry out tests on application to the ground and water absorption,” explains the doctor in civil engineering. That same morning, in the company of work-study student Thibault Maingot, she analyzed tests by sliding a chair across the sediment tiles. The 20-year-old student is delighted: “Since the beginning, we have improved a lot. We meet the highest expectations of existing flooring standards. »

Supported by the city of Brest, the department of Finistère and the Brittany region, Gwilen plans industrial development by 2027, with 5,000 to 10,000 m3 transformed per year compared to a few dozen currently. “There are still many questions about transport or the location of recovery sites so that the project is coherent from start to finish,” notes its founder, Yann Santerre. The prospects look even more promising as the blue economy law will prohibit the discharge of polluted dredged sediments into the sea in January 2025.