A modern-day gold rush is on. But the source isn’t the California hills. Instead, today’s treasure hunters occupy laboratories and dig into televisions, computers, smartphones, and shortwave radios. Thar’s gold in them thar circuits!
For centuries, people have sought gold for its beauty and corrosion-resistance. So when the psalmist David called the rules of the Lord “more to be desired . . . than gold,” he was declaring God’s law exceedingly valuable. (Psalm 19:10)
In the tech world, gold imbues electronics with durability and helps them work effectively. As technology advances, out-of-date devices get discarded—along with small amounts of gold in their circuit boards and wiring.
Sometimes, people recycle old machines and salvage the precious metals inside. But often, the small amounts of gold or copper are too difficult, expensive, and even toxic to extract. So they become electronic (or e-) waste.
Raffaele Mezzenga is a scientist at ETH Zürich, a Swedish research university. He discovered an unusual agent for extracting gold from e-waste: leftover cheese.
Actually, it’s not cheese the scientists use for the extraction process. It’s a cheese byproduct. Milk that’s been curdled and strained leaves a leftover liquid called whey protein. (Remember little Miss Muffet?) It contains lactose (milk sugar) as well as minerals, proteins, and vitamins.
Mezzenga’s colleague, scientist Mohammad Peydayesh, creates a gel from whey protein. He and the ETH team dry the gel and form a sponge-like product out of the slender protein fibers.
The scientists also dissolve discarded computer circuit boards (called “motherboards”) in acid. The fluid separates gold ions in the boards from other metal ions. In goes the whey protein sponge. It soaks up the gold from the liquefied motherboards.
Scientists then heat the gold-soaked sponge to release the valuable element. In one case, the sponge and 20 dissolved motherboards rewarded scientists with a tiny gold nugget. It was 91% pure and weighed about 0.016 of an ounce. Hardly a motherlode, but still—gold from cheese.
Mezzenga loves the plan. It helps recycle or repurpose not one but two things: e-waste and food waste.
Next up for the would-be alchemists at ETH is finding ways to harness other waste products for uncommon uses. Silver from breadcrumbs? Platinum from wilted lettuce? Those options seem unlikely—but who knows what the next golden waste goose will be?
“The fact I love the most is that we’re using a food industry byproduct to obtain gold from electronic waste,” says Mezzenga. “You can’t get much more sustainable than that!”
Why? Good stewardship involves more than saving money. It includes astounding creativity and using even waste resources in innovative ways.
