Abstract
Silicon is a Critical Raw Material of high economic importance that also faces a great supply risk in Europe. Conventionally, silicon is produced by reducing quartz with carbon, in a process known as carbothermic reduction of silicon. In this master thesis, a new approach that substitutes carbon reductants and primary materials by former aluminium and silicon waste streams is benchmarked. This production route, the aluminothermic reduction of silicon, could be more sustainable from an environmental perspective as it can reduce both furnace emissions and the overall electricity consumption of the process. A Life Cycle Assessment (LCA) is therefore developed to compare the sustainability of the conventional and aluminothermic silicon production routes. Different secondary input materials are explored in the aluminothermic route, for instance, the use of aluminium dross, post-consumer aluminium scrap or silicon skulls, and the influence of future scenarios is evaluated. Results show that the impact decrease substantially in the aluminothermic route for most studied impact categories, when new scrap is utilized as raw material, following a reduction in the energy consumed, pollutants emitted and enhanced waste utilization rate. However, the use of post-consumer aluminium scrap is dependent on the expected alternative use of the scrap fraction and could account for much higher impacts when applying a global scope. In the coming years, future scenarios show a great opportunity in the aluminothermic route as an example of industrial symbiosis for these raw material industries, following surplus volumes of aluminium scrap and an increased demand for silicon metal.
