Results’ variability in non-ferrous metal recycling life cycle assessment: study on waste-specific impacts and allocation methods

The European Commission’s 2023 update of the Critical Raw Materials list underscored the strategic importance of assessing recycling technologies for environmental protection and resource recovery. In parallel, Life Cycle Assessment (LCA) has become a key methodology for evaluating the environmental impacts of recycling systems processing metal scraps, electronic waste, and various industrial by‑products. Yet, from a methodological perspective, the intrinsic multifunctionality of recovery technologies, simultaneously operating as waste treatment solutions and as producers of secondary raw materials, creates substantial challenges for impact assessment. On top of this, LCA studies in this sector are subjected to arises from many factors, including the wide range of available technologies, the co production of multiple metals and the associated allocation methods, differences in energy mixes, and the diverse types of waste treated. Among these, waste heterogeneity of wastes has received comparatively less attention, even though the chemicals, energy and fuel requirements, as well as the specific unit processes involved, vary significantly with the type of waste processed. This study presents an ex ante LCA of a copper and precious metal recycling process. Environmental impacts are calculated for four waste categories per ton of waste, with the aim of attributing to each waste stream the impacts for which it is responsible. An average LCA result, based on the plant’s operational capabilities, is also evaluated for comparison. Then the impacts are allocated, according to common allocation methods found in the scientific literature, to the metals produced from every waste. Environmental performance varies with both waste composition and certain process parameters, such as total wastewater generated, the amount of black copper recovered, and the specific consumptions required for refining the metals present in the waste. This study highlights the need for transparent reporting of inventory assumptions and waste-specific data in metal recovery LCA studies.