699 3.2. Scenarios And System Boundaries Energy consumption across all systems was quantified for electricity and direct fuel use, and greenhouse gas emissions were calculated using emission factors consistent with the GHG Protocol. Electricity emission factors reflect the geographical context of each process stage, while fuel emission factors are based on standardized values reported in the literature. By combining primary operational data, real transport tracking, and established emission factors, this methodology enables a transparent and robust comparison between conventional mining and internationally integrated urban mining systems from a carbon footprint perspective. Three scenarios were evaluated: • BAU: Primary extraction and processing of gold, silver, and copper. Inventory data were obtained exclusively from secondary sources, including peer-reviewed literature and publicly available sustainability and operational reports from mining companies operating in Peru. The system includes extraction, concentration, and refining stages. • R&R: Urban mining pathway based on primary data, covering collection, dismantling, pretreatment, international transport, and metallurgical recovery of metals from electronic boards. Data were obtained through direct collaboration with a Peruvian e-waste operator (collection, dismantling, export) and a European metallurgical recycler (pyro-hydrometallurgical treatment). • R&R-MP: Extrapolated scenario if the exported material consisted exclusively of mobile phone printed circuit boards (PCBs). Metal yields were adjusted using literature-based concentration factors, while all logistical and treatment parameters remained unchanged. All scenarios are modeled under consistent cradle-to-gate boundaries. 3.3. Scenarios And System Boundaries The R&R analysis is based on a real industrial case involving 20.39 tons of electronic boards exported from Peru to Western Europe in 2024. Pre-treatment energy consumption data were collected directly from the Peruvian operator (Comimtel), who confirmed that the shipment consisted exclusively of segregated printed circuit boards (PCBs) dismantled prior to export. Maritime transport from the Port of Callao to the Port of Antwerp (14,133 km; 31 days) was modelled using vessel-specific operational data, with emissions allocated by mass fraction relative to the vessel’s deadweight tonnage. Inland transport and pyro-hydrometallurgical processing were included using operator-reported Scope 1 and Scope 2 emission intensities (kgCO₂eq/kg boards treated), calculated under ISO-compliant internal LCA procedures. Metal content estimations were based on PCB-specific characterization data. However, as industrial refining in Western Europe typically processes whole mobile phones (excluding batteries), where plastics and resins contribute to the thermal and reduction processes, this PCB-based modelling approach likely represents a conservative estimate compared to full-device industrial conditions. 3.4. Carbon Footprint Calculation And Extrapolation GHG emissions were calculated using IPCC 2006 [29] emission factors and location-based electricity grid factors. Emissions were aggregated as tCO₂eq, using GWP100 values. For the BAU scenario, carbon footprint values were derived from secondary data obtained from sustainability reports and annual reports of five of the largest mining companies operating in Peru, ensuring representativeness of conventional primary mining practices [29], [30], [31], [32], [33], [34]. For the R&R scenario, total emissions were allocated to recovered metals based on measured metal outputs. These metal-specific emissions were then summed to represent a multi-metal urban mining system, reflecting the economic and operational reality that recovery viability depends on the joint extraction of several metals rather than a single element. For the R&R-MP scenario, metal outputs were recalculated using reported concentration ranges for mobile phone
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