Transforming processed bauxite into valuable resources
Processed bauxite, also known as bauxite residue or red mud, is the main by-product of alumina production. More than 7 million t of processed bauxite is produced annually in the EU alone, but less than 100 000 t is recycled. Most processed bauxite is landfilled because there is no large-scale, sustainable reuse option currently available.
Win-win scenario for European aluminium and cement sectors
As conventional supplementary cementitious materials (SCMs)(opens in new window) such as fly ash and blast furnace slag become scarcer, the cement industry is seeking alternatives like processed bauxite. The availability of processed bauxite and the proximity of alumina plants to cement plants across Europe offer a promising opportunity for resource efficiency and circularity through industrial symbiosis – unused or residual resources of one company are used by another. The EU-funded ReActiv(opens in new window) project established a symbiotic value chain between cement plants and alumina refineries, demonstrating the conversion of processed bauxite into a new SCM suitable for cement applications. It also substituted up to 30 % of clinker – the main ingredient in cement – in the production of cement.
Redefining perceptions around processed bauxite
“ReActiv transforms an abundant industrial residue into a valuable resource, enabling true industrial symbiosis,” comments Philippe Bénard, R&D project manager at Holcim Innovation Center(opens in new window), the Swiss-based company that coordinated the project. To achieve these goals, the researchers employed three different processing routes: processed bauxite thermal activation with kaolinite clay (co-calcination process), processed bauxite carbothermic vitrification for iron-rich SCM (vitrification process) and processed bauxite reductive smelting for iron-free SCM (smelting process). Specifically, project partners demonstrated the direct use of processed bauxite in two new alternative cement products. The first was a novel calcium sulfoaluminate-ferrite clinker that uses 35 % of processed bauxite as raw material. The three demonstrators are now up and running.
Replicable technology to reduce CO2 emissions
The technological solution can be replicated and used in the alumina and cement sectors, but also in recycling by-products of other industrial sectors. It also has the potential to reduce wastewater. “ReActiv reimagines what was once considered industrial waste – processed bauxite – as a cornerstone for Europe’s next generation of SCMs in the development of low-carbon cement products,” adds Bénard. “Its pioneering approach converts an environmental liability into industrial opportunity, unlocking a new class of high-performance SCMs.” Based on a life-cycle assessment, the 100-year global warming potential(opens in new window) for the SCMs was estimated at 200 kg CO2/t for co-calcined processed bauxite, 440 kg CO2/t for vitrified processed bauxite and 470 kg CO2/t for smelted processed bauxite. To further reduce the SCMs’ carbon footprint, key mitigation strategies included the electrification of processing routes with green energy instead of using fossil fuels and the substitution of fossil-based carbon with biocarbon as a reducing agent. “ReActiv exemplifies a transformative model of cross-sector collaboration, circular innovation and systemic integration that revitalises industrial value chains, optimises land use by minimising waste storage, and cultivates a skilled workforce aligned with the green transition,” concludes Bénard. “Project outcomes are in line with the EU Clean Industrial Deal and act as an enabler for a more sustainable future for Europe.”