Wasting the Risk, or Risking the Waste? Understanding the trends of critical raw material loss into waste streams during copper and aluminium processing

Many critical raw materials (CRM) necessary in the transition to carbon-neutral energy reside in the waste streams of mining projects, as they are by-products and often not recovered alongside the primary metal. This work aims to document (i) the loss and potential recovery of by-product metals during the host commodity processing and (ii) the consequences of non-recovery, via a multi-scale risk–reward analysis. The information on the deportment of by-product metals through processing circuits is crucial for treating them as a resource, without which they risk near-permanent loss when treated as ‘waste’. We review the deportment of tellurium and selenium as by-products of copper processing; and gallium, scandium and rare earth elements in aluminium processing, as these CRMs are representative of different geological settings, mining methods, processing circuits, and waste types. We classify the scale of the effects of their non-recovery using three risk categories: comprehensive differentiation covers individual risks (environmental, social, governance and economic); complex differentiation covers the interactions of compounding factors that alter the magnitude and timeframe of their impact; and ecological/systems diffraction comprises systematic, long-term effects that disproportionally affect vulnerable communities and locations globally. We offer a new perspective on by-product elements that rely on the production chain of primary commodities but are rarely recovered economically because of the lack of refinery infrastructure and technologies. We suggest that incentives to promote waste management strategies that preserve CRM resources for concurrent recovery or future reprocessing could substantially mitigate supply risks, while reducing social and environmental risk and impact.