Aluminum scrap recycling: from waste pickers to smelters – a comprehensive review of processes, challenges, and opportunities

Aluminum recycling plays a pivotal role in reducing environmental impacts and meeting the growing global demand for lightweight and versatile materials. This review provides a comprehensive overview of the aluminum recycling chain, starting from informal waste pickers responsible for post-consumer scrap collection to advanced industrial smelting processes that generate high-quality secondary aluminum. The study highlights key technical stages, including sorting, cleaning, pre-treatment, and melting, while addressing the challenges posed by scrap contamination, process inefficiencies, and the integration of informal sectors into formal recycling systems. From an environmental perspective, aluminum recycling requires up to 95% less energy and emits 90% fewer greenhouse gases compared to primary production, positioning it as a central strategy for climate change mitigation and circular economy goals. Economically, the industry faces market volatility, heavily influenced by global demand and London Metal Exchange (LME) price fluctuations. Socially, the lack of formalization for waste pickers remains a barrier to equitable and efficient collection networks. Future innovations such as Industry 4.0 automation, blockchain traceability, and Extended Producer Responsibility (EPR) policies are identified as essential for improving efficiency, transparency, and sustainability. Despite significant progress, research gaps persist in digital integration, life cycle assessment (LCA), and global policy harmonization. This review emphasizes the need for an integrated approach combining technological innovation, regulatory frameworks, and social inclusion to achieve a truly sustainable aluminum recycling sector.