Multi-Assay Characterization of an LED Recycler Feedstock for Economic and Environmental Valuation of Critical Metals

Urban mining is gaining importance as demand for critical metals continues to rise. Waste light-emitting diode (LED) lamps are a valuable secondary source of gallium, rare earth elements, precious metals, and base metals, yet accurately quantifying these metals remains challenging. In this work, various LED waste streams from a lamp recycler were subjected to critical metal characterization. The strengths and weaknesses of established metal assay techniques were evaluated to advance the determination of gallium, rare earth elements (Ho, Lu, Tb, Y, Er, Nd, Ce), and precious metals (Au, Ag, Pt, Pd) in LED waste. Metal assays, including alkaline fusion, four-acid digestion, aqua regia, a fire assay, and energy-dispersive X-ray fluorescence, were compared, and precision was assessed using a newly created LED lamp reference material and OREAS465. A metal-analysis-driven approach was developed to quantify the reduction in mining through recycling LED lamps using the rock-to-metal ratio metric. The economic value of LED waste streams, together with their recyclability and grindability, was assessed. The results indicate that LED strips can contain up to 147,484 g/t Cu, 452 g/t Ga, 367 g/t Lu, 89 g/t Tb, and 95 g/t of precious metals. Recycling one tonne of waste LEDs can offset mining 75.5 tonnes of rock and primary ore. The estimated economic value of mixed LED waste was USD 3351 per tonne, increasing to USD 4089 per tonne after physical separation. The results demonstrate the importance of robust analytical methods for accurate metal accounting and provide a stronger foundation for assessing the recycling potential of LED waste.