Circular economy potential of inorganic polymers from bauxite residues and other slags: An LCA study

The present study aims at discussing a new possible model of utilisation of bauxite residue, the waste produced from the extraction of alumina from its ore, and other metallurgical slags in the European Union, taking into consideration technological, economic, and environmental factor. The model aims at providing the EU construction sector with a more sustainable, and possible better performing alternative to ordinary Portland cement: alkali activated materials, inorganic polymers, and geopolymers produced from the byproducts of the metallurgical industries in the region. Full-scale utilisation of the resources was set as a goal of the new system, and assumptions were formulated from the results of the literature review. In order to build a supply model and measure the environmental performance of the new system, a combined approach and different methodologies were used. In subsequent steps, the system of production of bauxite residue-derived geopolymer binder was modelled and mass-balanced, and then used to build a life cycle assessment study. The resource base of BR and copper slag was quantified and mapped, and so was the consumption of OPC in the EU. The economic impact of transport was kept in mind when setting the conditions of the supply model, which was built with a GIS software. Finally, data were elaborated to give a final assessment of the circular economy potential of the new system proposed, in terms of potential supply, substitution of OPC, and avoided deposition of BR. The study argues that developments in this technology and its upscaling would bring net environmental benefits to the region, and underlines the scale of availability of the waste materials that could be used as inputs. In particular BR, who currently is a environmentally hazardous material and a cost for the aluminium industry, could become a valuable resource if a more circular model and the principles of industrial symbiosis were applied