Precious Rubbish [e-waste - recycling

Abstract

Waste electronics are piling up around the world, the United Nations Global E-Waste Monitor estimated that consumers, governments and companies threw away some 53.6 million tonnes of unwanted electronics in 2019. There is money in all that e-waste. The equipment might be mostly plastic and processed sand but buried in every chip are commercially viable quantities of gold, silver and other rare metals. The gold and silver are used in minute quantities individually, mostly to coat connectors and form the tiny bond wires that connect silicon chips that do not use the more advanced flip-chip bonds to the pins of their epoxy package. But even in those trace amounts, the quantity of gold and silver in a tonne of printed-circuit boards (PCBs) with the components still attached is a little higher than you would expect to find in high-grade ore from a precious-metals mine. The bad news is the cost of extraction: you need to manually separate components, grind up the boards and finally burn the plastic waste to eradicate poisonous organic chemicals such as polychlorinated biphenyls, which results in more carbon emissions and needs aggressive filtering on the exhaust to avoid contaminating the surrounding environment. And extracting the precious metals largely calls for the same cyanide-based leaching agents that the mine operators would prefer to phase out. Not only are they notoriously toxic, they are expensive to dispose of or recycle.