Balancing energy, resources and emissions: a comparative analysis of alumina production technologies

The global demand for primary aluminium continues to rise, driving record productions of smelter-grade alumina. The main industrial route to produce alumina, the Bayer process, faces critical challenges, including the generation of bauxite residue and the high thermal energy demands reliant on fossil fuels. This study evaluates two alternative technologies, the Pedersen and AlSiCal processes, comparing their energy requirements, CO 2 emissions and resources utilisation to those of the Bayer process. The Pedersen process integrates smelting-reduction of bauxite to co-produce alumina and pig iron, while the AlSiCal process, developed within the H2020 AlSiCal project, utilises anorthosite as feedstock to co-produce alumina, silica, and precipitated calcium carbonate. Both processes were modelled in Aspen Plus, with the Pedersen process based on industrial and literature references and the AlSiCal process validated through experimental tests. Despite their environmental advantages, both processes exhibit higher energy intensities compared to the Bayer process, with the Pedersen and AlSiCal processes requiring 13.6–14.3 GJ/tonne and 42.2 GJ/tonne of alumina, respectively. Nonetheless, the consideration of co-products through economic allocation significantly improved the interpretation of resource and energy performance, highlighting the potential of both routes to enhance resource utilisation and reduce waste generation. These findings highlight the technical and environmental potential of the Pedersen and AlSiCal processes as complementary routes for alumina production, utilising low-alumina bauxites and underexplored mineral resources to reduce emissions, mitigate waste, and address mineral scarcity. Although their industrial implementation requires further techno-economic assessment and market validation, the integration of renewable energy, commercialising by-products, and adopting circular economy principles can pave the way towards a more sustainable alumina industry