701 Figure 1 – GHG emission hotspots and source contribution in the R&R system. 4.2. Carbon Footprint by Metal Supply Model Conventional mining (Business as Usual – BAU) exhibits the highest greenhouse gas emissions among the evaluated metal supply models. When considering the combined recovery of 1 kg of gold, 1 kg of silver, and 1 kg of copper, total emissions exceed 29.59 tCO₂eq. These values are primarily driven by the low concentration of target metals in primary ores, which results in energy-intensive extraction, beneficiation, and refining processes. Urban mining pathways show markedly improved environmental performance. The recovery and reuse of mixed electronic boards (R&R) reduce the carbon footprint associated with the joint recovery of the three metals to approximately 10.17 tCO₂eq, representing a reduction of nearly 66% relative to the BAU model. The most pronounced improvement is observed for the recovery and reuse of mobile phone electronic boards (R&R-MP), where emissions decrease to approximately 1.75 tCO₂eq for the same combined metal output. This corresponds to a reduction of up to 94% compared to conventional mining. These results highlight that, if the objective is to supply 1 kg of gold, 1 kg of silver, and 1 kg of copper, conventional mining generates substantially higher greenhouse gas emissions than urban mining pathways based on electronic waste. The magnitude of these differences across the evaluated models is illustrated in Figure 2.
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