Gold is unique because it can be recycled endlessly without any loss of quality or purity. This intrinsic property makes gold recycling a fundamental part of the global gold supply chain, providing a stable source of the metal. Recycling involves recovering gold from discarded materials and purifying it for use in new products, returning the metal to the market. Recycled gold is chemically and physically identical to gold extracted through primary mining.
Primary Sources of Scrap Gold
The materials used for gold recovery originate from two major streams: high-value consumer goods and industrial scrap. The largest volume source is post-consumer material, which primarily consists of old jewelry, bullion, and coinage. This high-value scrap accounts for the vast majority of the total recycled gold supply, often estimated to be around 90%.
The second major stream is industrial and technological scrap, often termed “urban mining.” This category is dominated by electronic waste (e-waste), which contains gold in circuit boards, connectors, and processors. While e-waste represents a smaller percentage of the total recycled volume, the concentration of gold in certain electronics can be quite high. For instance, a single ton of discarded mobile phones can yield up to 80 times more gold than a ton of raw gold ore. Other minor sources include dental alloys and materials from gold-plating industries.
Methods for Gold Recovery and Purification
The process of transforming scrap gold into high-purity metal requires several technical steps, beginning with initial preparation specific to the source material. For e-waste, this involves mechanically dismantling the devices to isolate gold-bearing components, such as printed circuit boards and connectors. High-value scrap like jewelry is often melted down directly to separate the gold from any non-metallic inclusions, which is less complex than treating industrial waste.
Once the gold-containing material is ready, it undergoes pyrometallurgical treatment, involving high-temperature smelting to concentrate the precious metals. This step removes base metals and non-metallic material, leaving a crude metal alloy rich in gold and other precious metals like silver or platinum. The resulting alloy must then be subjected to refining to achieve the purity levels required for investment-grade bullion or manufacturing, typically 99.99% pure.
Refining is accomplished through two primary methods: chemical treatment or electrolysis. One common chemical method uses Aqua Regia, a powerful mixture of nitric acid and hydrochloric acid, which dissolves the gold and other metals, allowing for selective precipitation of the pure gold. For the highest purity, the Wohlwill electrolytic process is often used, where the crude gold alloy is cast into an anode and immersed in an electrolyte solution. An electric current causes the gold atoms to dissolve and deposit onto a stainless steel cathode as pure gold. The Miller process, which uses gaseous chlorine to react with impurities at high temperatures, is a faster method but yields a slightly lower purity, typically around 99.5%.
The Role of Recycling in Gold Supply
Gold recycling plays a significant role in stabilizing the global gold supply, consistently accounting for about 25% to 33% of the total annual supply. This recycled volume provides a buffer against fluctuations and disruptions in primary mining operations, contributing to market equilibrium. Recycled gold also promotes a circular economy by keeping existing resources in use and reducing the reliance on newly extracted material.
The environmental advantages of recycling are substantial when compared to traditional mining. The energy required to produce gold from scrap is much lower than the energy needed for primary extraction and refining. High-value gold scrap recycling has a significantly lower cumulative energy demand and global warming potential than both electronic scrap recycling and primary mining. By avoiding the need to excavate and process tons of raw ore, recycling greatly reduces habitat destruction, water usage, and the generation of toxic chemical waste associated with mining practices.