Inaugurated on Friday, the brand new factory illustrates the green reindustrialization strategy advocated by the executive. It promises to emit three to five times less greenhouse gases than traditional large cement manufacturers and has been financially supported by the recovery plans and France 2030.

Every year, 250,000 tons of low-carbon cement are expected to come out. A straw compared to the needs of the country which consumes 18 million tons of cement per year. But a revolution in a sector that has hardly changed its highly polluting manufacturing methods since the invention of cement 200 years ago.

The traditional process - by firing limestone for 18 hours at more than 1,400 ° C to obtain the essential element of cement, clinker - requires gigantic volumes of natural gas and emits almost one tonne of CO2 per tonne of cement produced - 866 kilos - i.e. emission ratios higher than those of air transport.

The Vendée cement of Hoffmann Green "has no clinker", emits "on average 200 kg of CO2" per tonne, is manufactured "without cooking", "without gas", "without water" and "at room temperature", by "mixing industrial waste reduced to powder", summarizes for AFP Julien Blanchard, chairman of the board and co-founder of the start-up born in 2015.

The three main ingredients are "iron and steel slag" - waste from steelmaking - "clay sludge" recovered from quarries, and "gypsum" contained in plasterboard from the deconstruction of buildings.

Homemade patented admixtures then trigger a cold reaction that amalgamates the cement. The recipe was developed by David Hoffmann, mineral chemical engineer and former Séché Environnement, co-founder of the start-up.

In this vertical factory with a unique concept, the 70-metre-high tower mixes ingredients from 19 silos several tens of metres high. And above all to "halve the footprint" of the facility compared to the first small pilot plant installed next door.

Julien Blanchard co-founder of Hoffmann Green on the production site in Bournezeau (west) on May 10, 2023 © Sebastien SALOM-GOMIS / AFP

Another essential element of the decarbonization of the process, energy now weighs only 2% of the company's overall costs "against 20% in the traditional sector", according to Blanchard.

The "colossi" can "disappear"

A series of photovoltaic panels on stilts, like large metal trees following the orientation of the sun all day, generate 50% of the site's electricity consumption.

"All these elements mean that overall our cement generates five times less CO2 emissions than traditional cement," says Blanchard.

Of course the price is also "twice as expensive as that of traditional cement," he admits. "But the more we produce, the more prices will fall," he says, betting on a "crossing of price curves" between his cement and the traditional "in 2026-27".

An employee carries bags of cement in the storage room of Hoffmann Green's production site in Bournezeau (west) on May 10, 2023 © Sebastien SALOM-GOMIS / AFP

The cement industry "sees us as the bad guys who want to close traditional cement plants," says Stéphane Pierronnet, director of operations of the plant.

Yet the past five years have been a long and expensive road. Especially to obtain certifications allowing carbon-free cement to enter the court of large standardized and referenced cements.

"Between 5 and 10 million euros" were needed to finance the evaluations to obtain the guarantee that "our cements are as strong", "with such a long life, the same resistance to fire, sea salts .." as traditional cements, explains Mr. Blanchard.

The company, which employs 55 people, 20% of whom are in research and development, is planning a second plant in Dunkirk. She also has projects in Switzerland, Belgium and the United Kingdom.

"We have demonstrated that we can make cement without polluting clinker, but clinker is the raison d'être of the traditional industry which has not yet fully grasped the measure of the revolution underway," adds Blanchard.

"A bit like Kodak who did not believe in the end of film," he adds, "even if they are colossi, they can disappear very quickly if they do not adapt quickly to the new context."

© 2023 AFP