704 5. CONCLUSIONS The results show substantial differences in carbon intensity depending on both the metal considered and the supply route. For gold, the BAU model exhibits a carbon footprint of 29.22 tCO₂eq/kg, compared to 8.57 tCO₂eq/kg under the R&R scenario and 1.20 tCO₂eq/kg under the R&R-MP scenario, corresponding to absolute emission reductions of 20.65 and 28.02 tCO₂eq/kg, respectively. For silver, BAU presents a footprint of 0.283 tCO₂eq/kg, while R&R and R&R-MP reach 1.583 and 0.53 tCO₂eq/kg. For copper, BAU remains the lowest-intensity route at 0.0023 tCO₂eq/kg, compared to 0.0056 tCO₂eq/kg (R&R) and 0.0062 tCO₂eq/kg (R&R-MP). When metals are evaluated jointly to reflect the operational reality of multi-metal recovery, supplying 1 kg of gold, 1 kg of silver, and 1 kg of copper results in 29.51 tCO₂eq under BAU, 10.16 tCO₂eq under R&R, and 1.74 tCO₂eq under R&R-MP. The lower combined footprint of the R&R-MP configuration is driven primarily by gold, which dominates total emissions due to its low geological grade in primary mining and high concentration in electronic waste. From a resource availability and value chain perspective, urban mining exhibits substantially higher metal concentrations than primary ores, with average BAU grades of 3.73 g/t for gold, 120 g/t for silver, and 50 kg/t for copper, compared to 164 g/t, 888 g/t, and 250.21 kg/t, respectively, in mixed electronic boards, and up to 1.17 kg/t of gold, 2.64 kg/t of silver, and 226.85 kg/t of copper in mobile phone boards. Emissions in the R&R and R&R-MP models are dominated by metallurgical treatment, while collection and international transport contribute a smaller share; operator-reported data indicate a gate-to-gate footprint of 1.327 kgCO₂eq per kilogram of electronic boards treated (Scope 1 and 2). Consequently, further emission reductions in urban mining depend primarily on the decarbonization of high-temperature metallurgical processes rather than logistics optimization. While primary mining remains necessary to meet global demand for copper and silver, particularly under energy transition scenarios, urban mining emerges as a complementary supply route capable of reducing emissions for gold and multi-metal systems, provided that effective collection, traceability, and access to low-carbon energy are ensured. 6. RECOMMENDATIONS The results demonstrate the need to rethink mining by expanding mineral supply strategies beyond exclusive reliance on primary extraction, while recognizing that urban mining functions as a complementary pathway rather than a substitute for conventional mining. Primary extraction remains indispensable to meet the scale of demand associated with the energy transition, particularly for copper and silver. However, the substantially higher metal concentrations identified in WEEE—especially in mobile devices—confirm that secondary resources already embedded in the economy represent a technically viable and currently underutilized source of supply. Allowing these materials to be lost leads to avoidable resource inefficiencies and unnecessary environmental impacts along the mineral value chain. In the Peruvian context, the main constraint to scaling Recovery and Reuse (R&R) systems lies upstream, in the collection, classification, and pre-treatment of WEEE. The results indicate that without a stable supply of high-grade and traceable feedstock, the emission reductions associated with urban mining cannot be translated into industrial-scale implementation. Future assessments should therefore adopt integrated multi-metal and multi-criteria approaches, combining carbon footprint analysis with full life cycle assessment, economic valuation, and sensitivity analyses of energy mixes and process efficiencies. This integrated perspective is essential to support evidence-based policy design, guide investment decisions, and position urban mining as a complementary pillar within a more circular, resilient, and climate-aligned mineral value chain. ACKNOWLEDGEMENTS The author acknowledges the support of the Department of Environmental Engineering at the University of Engineering and Technology (UTEC), Peru; Comimtel Recycling, the Peruvian e-waste
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