Figure 3 - Metal concentration versus carbon footprint per kilogram of recovered gold, silver and copper under conventional (BAU) and urban mining (R&R and R&R-MP) models. 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 gateto-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
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