Carbon-Neutral Silicon via Aluminothermic Reduction? Exploring Industrial Symbiosis through Life Cycle Assessment

Silicon is conventionally produced by carbothermic reduction, which reduces quartz with a carbon source. An alternative process is the aluminothermic reduction, which uses an aluminum source instead, leading to a substantial decrease in direct CO₂ emissions. This paper assesses a case study on industrial symbiosis by producing silicon through aluminothermic reduction using aluminum dross resourced as a reductant material. Various process alternatives are evaluated, with inventories constructed from thermodynamic process simulations and mass and energy balances. We find that the impact of global warming and cumulative energy demand can be reduced by up to 80% in the aluminothermic route. Still, other impacts increase due to the strong influence of the expected alternative use of the aluminum scrap fraction and the need for additional input materials. From the different process parameters and configurations studied in the aluminothermic route, recirculating carbonation gases, reprocessing the byproduct slags, and the use of surplus aluminum scrap hold the most significant potential. The methodology used in this article exemplifies the use of prospective Life Cycle Assessment (LCA) in support of concept development to identify environmental hotspots and improvement potential in the early phases of production technologies.