Towering over the Poitou countryside, a 100-meter-tall concrete “cyclone tower” flanked by 13 cranes is the centerpiece of a cutting-edge cement plant under construction in Airvault (Deux-Sèvres).
This ambitious project aims to produce lower-carbon cement against the backdrop of global warming.
Approximately 500 workers are busy on this “pharaonic” construction site owned by the German giant Heidelberg Materials, which is investing around 350 million euros to halve the site’s CO2 emissions by 2030.
This 21-hectare cement plant is scheduled to begin operations in 2025, replacing its historic neighbor founded in 1919, while retaining its 150 employees.
The Airvault plant (emitting 549,000 tons of CO2 in 2022) was ranked as the 12th largest industrial emitter of greenhouse gases in France, in a sector that alone accounts for 7% of global CO2 emissions.
“We are the second largest cement producer in the world. Our decarbonization efforts are visible on a global scale,” asserts Bruno Pillon, President of Heidelberg Materials’ French operations.
The traditional cement manufacturing process requires a significant amount of energy and emits approximately 800 kg of CO2 per ton produced, a ratio higher than that of air travel.
However, according to the French Environment and Energy Management Agency (ADEME), deploying the best available technologies by 2050 “could lead to a 50% reduction in emissions, with a production cost increase of 15 to 25%.”
Rotary Kilns
In Airvault, the two massive rotary kilns of the historic site, tubes heated to 1,450°C, transform the “crude,” a white granulated limestone, into lava. After cooling, the “clinker,” a blackened granule with new hydraulic properties, is ready to be mixed with other materials to form cement, the basic ingredient of concrete.
This firing process, known as calcination, generates incompressible CO2 through a chemical reaction, accounting for two-thirds of a cement plant’s emissions. The remaining emissions are related to energy consumption.
With its new “cyclone tower” and a “latest generation” cooler, Heidelberg is targeting the latter by replacing 90% of fossil fuels with alternative fuels, such as non-recyclable waste.
“The preheater tower with precalciner is truly the lever for decarbonization,” explains Bruno Manivet, director of the cement plant. “By 2030, this aligns with the group’s global commitment to reach 400 kg of CO2 per ton of cement.”
A report by the Climate Action Network acknowledged in 2023 “a reduction in [Heidelberg France’s] global emissions since 2019,” which, however, “remains to be confirmed.”
The group, investing 650 million euros in France, aims to achieve carbon neutrality by 2050.
To address the two-thirds of incompressible emissions, Heidelberg is part of the GOCO2 consortium, which plans to capture and transport industrial carbon dioxide to storage or utilization sites.
The group also intends to reduce the proportion of “clinker” in its cement. This path is being explored by the French start-up Hoffmann Green, which produces cements without firing, composed of “steel slag” (waste from steel production), clay sludge, and gypsum.
A “Hardly Credible” Goal
The professional organization France Ciment estimates the cost of decarbonizing the French sector at 3.8 billion euros, twice its annual turnover.
Nevertheless, the goal of neutrality seems “hardly credible,” according to Morgane Moullié, project manager at the Sustainable Real Estate Observatory (OID), who questions the methodology used – for example, for steel slag, sometimes counted “as zero” in the cement’s carbon footprint because it is derived from reuse.
“I don’t think we’re tackling the problem from the right angle,” she continues, citing the need to move towards bio-sourced materials like stone or wood, which are “more promising.”
“If we were to generalize low-carbon impact materials in new buildings by 2030, we would have a 22% reduction in emissions,” confirms Andrés Litvak, Sustainable Building Manager at the southwest regional office of Cerema, a public establishment for expertise on ecological transition.
However, “if we look at the market, the easy solution is concrete,” due to insufficient supply of bio-sourced materials, he adds, also emphasizing the necessity of this material for foundation construction.