Life cycle assessment of aluminum-silicon alloy production from secondary aluminum in China

As the world's largest aluminum producer and consumer, less than 25% of China's aluminum production was obtained through the secondary aluminum production, which had far less energy consumption and greenhouse gas (GHG) emissions than primary aluminum production. It was as an effective pathway for China's aluminum industry to achieve its carbon neutrality goals by using the recycled aluminum. Therefore, this study adopted the method of life cycle assessment (LCA) to investigate the environmental impact of aluminum-silicon alloy production from recycled aluminum, based on the actual production data of the typical secondary aluminum enterprise in China. The production of 1t aluminum-silicon alloy from secondary aluminum was chosen as the functional unit for this study, which addressed the environmental aspects and potential environmental impacts throughout the systemic processes contained in the production of aluminum-silicon alloy. The LCA results showed that the remelting stage generated the highest environmental load, especially in terms of freshwater ecotoxicity and marine ecotoxicity, with normalized characters of 96.23 and 64.36 respectively. Silicon metal and natural gas were identified through sensitivity analysis as key substances for reducing the environmental burden. Then, the potential pathways to reduce the environmental burden were also discussed, such as selecting different processes for producing silicon metal and optimizing the process parameters of the remelting stage. Meanwhile, the analysis of GHG emissions showed that the carbon footprints can be significantly decreased by transferring the energy structure and deploying technologies of carbon capture, utilization and storage.