LCA of precious metals recovery: Modelling the secondary supply of gold, silver, platinum, palladium and rhodium from an integrated refining plant

Precious metals are essential elements in modern technology and the green transition, with limited alternatives on the market. Primary production is the main supply source to meet their current demand, with secondary sourcing remaining still quite limited. Indeed, although precious metals could last virtually forever in the anthroposphere, and thus be potentially available for recycling, their value chain is characterized by inefficiencies and material losses that prevent the closure of material flows. In addition to the challenge of improving recovery and recycling processes, there is also the need to quantify the environmental impact associated with secondary sources to support informed choices. In this work, we apply life cycle assessment (LCA) to estimate the potential environmental impacts associated with an integrated refining process precious metals (i.e., gold, silver, platinum, palladium, and rhodium), recovered from heterogeneous waste inflows including production scrap, spent catalysts, liquid waste, and incineration ash. The LCA model was created by mainly using primary data collected from the integrated refining plant, located in northern Italy, complemented with secondary data from the relevant literature. The ReCiPe 2016, IPCC 2021 GWP100, and CED methods were used for life cycle impact assessment. The resulting carbon footprint amounted to 0.43 t CO2 eq/kg Au, 0.01 t CO2 eq/kg Ag, 0.47 t CO2 eq/kg Pd, 0.18 t CO2 eq/kg Pt, 1.55 t CO2 eq/kg Rh, respectively. The insights complement the existing datasets for LCA and are expected to inform stakeholders engaged with the sustainability challenge in the life cycle of precious metals.