Environmental Life Cycle Assessment of Heap-Leach Gold Production: Hotspot Characterization and Sensitivity Analysis

Heap leaching is commonly applied to low-grade oxide gold ores, yet its life-cycle burdens remain poorly quantified for U.S. operations. This study presents a cradle-to-gate life cycle assessment of 1 kg of gold produced by heap leaching in Nevada, following ISO 14040/14044 and applying TRACI 2.1 in SimaPro 9.4. The system comprises heap-leach pad construction (HLPC) and processing operations, modeled with primary data from the Granite Creek Preliminary Economic Assessment and ecoinvent v3.9/USLCI background datasets, with economic allocation between gold and silver. Processing uncertainty was quantified by Monte Carlo simulation (n = 10,000), and HLPC was examined through sensitivity analysis of material mass and sourcing. The total global warming potential (GWP) is 2.53 t CO2 eq kg–1 Au, of which processing contributes 75% (1.89 ± 0.29 t CO2 eq; CV = 15%) and HLPC 25% (0.65 t CO2 eq). Leaching and carbon-in-column adsorption dominate processing (65%), driven by sodium cyanide production (1.09 t CO2 eq kg–1 Au), followed by crushing and agglomeration. Within HLPC, geomembranes govern energy-related categories, whereas aggregates dominate ecotoxicity, and off-site aggregate sourcing strongly amplifies impacts. Hotspot rankings remain robust under uncertainty (NaCN > electricity > NaOH), with moderate dispersion for most categories (CV 10–40%). The GWP is lower than reported values for primary gold (11–25 t CO2 eq kg–1 Au), mainly because mining and refining lie outside the system boundary. Priority mitigation measures include reducing cyanide consumption through recovery and recycling, renewable electricity, local aggregate sourcing, and recycled geomembranes.