Inaugurated a few days ago, 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 the large traditional cement manufacturers and has been financially supported by the recovery plans and France 2030.
Each year, 250.000 tons of low-carbon cement should 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 - firing limestone for 18 hours straight at over 1.400°C to obtain the essential element of cement, clinker - requires huge volumes of natural gas and emits almost a tonne of CO2 per tonne of cement. produced - 866 kilos - ie emission ratios higher than those of air transport.
Hoffmann Green's Vendée cement "has no clinker", emits "on average 200 kg of CO2" per ton, is manufactured "without cooking", "without gas", "without water" and "at room temperature", by "mixing powdered industrial waste", summarizes for AFP Julien Blanchard, chairman of the management board and co-founder of the start-up born in 2015.
The three main ingredients are "steel slag" -steel manufacturing waste- "clay sludge" recovered from quarries, and "gypsum" contained in plasterboard from the deconstruction of buildings .
In-house patented admixtures then trigger a cold reaction that allows the cement to amalgamate. 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-meter-high tower mixes the ingredients from 19 silos several tens of meters high. And above all "to halve the footprint" of the installation compared to the first small pilot plant installed right next door.
Another essential element of the decarbonization of the process, energy weighs more than 2% of the company's overall costs "compared to 20% in the traditional sector", according to Mr. Blanchard.
The "colossi" can "disappear"
A series of photovoltaic panels on stilts, like large metal trees following the orientation of the sun throughout the 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", summarizes Mr. 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".
The cement industry "sees us as the bad guys who want to shut down traditional cement plants", notes Stéphane Pierronnet, the plant's operations manager.
Yet the last five years have been a long and onerous road. Especially to obtain the certifications allowing low-carbon cement to enter the court of major standardized and referenced cements.
“Between 5 and 10 million euros” were necessary to finance the assessments making it possible to obtain the guarantee that “our cements are as solid”, “with such a long lifespan, the same resistance to fire, to sea salts .." than traditional cements, explains Mr. Blanchard.
The company, which employs 55 people, including 20% in research and development, is planning a second factory in Dunkirk. It also has projects in Switzerland, Belgium and the United Kingdom.
"We have demonstrated that it is possible to make cement without polluting clinker, but clinker is the raison d'être of traditional industry which has not yet fully taken the measure of the current revolution", adds M 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" .