May 14, 2024

2 min read

After Brewing Beer, Yeast Can Help Recycle Metals from E-waste

This beer-making by-product could offer a sustainable way to isolate metals for recycling electronic waste

By Riis Williams

Microscopic view of brewer’s yeast.

Science Photo Library/Steve Gschmeissner/Getty Images

When brewer’s yeast left over from beer making is mixed with the right seasonings, it makes a bitter, earthy paste called Marmite that is especially popular in the U.K. Smeared on toast, it’s a snack that can be an acquired taste. But a study published recently in Frontiers in Bioengineering and Biotechnology found that residual yeast sludge can also be used to bind to electronic-waste metals—a capability the research suggests could help recycle the world’s growing mountains of discarded gadgets.

When the study authors introduced brewer’s yeast, a single-cell fungus, to a liquid mix of various metals, they found that the yeast could select and absorb particular metals and could be used repeatedly at least five times without its binding capacity being diminished. This method, according to the team, provides a greener alternative to conventional extraction methods such as pyrometallurgy, a high energy-consuming smelting process that may emit harmful gases. Even though brewer’s yeast may be appealing to some, much of it still ends up wasted, and it is exceptionally abundant and inexpensive.

“In Austria, we manufacture a significant amount of beer resulting in plenty of leftover brewer’s yeast,” states the study’s primary author, Anna Sieber, a postgraduate student at the University of Natural Resources and Life Sciences in Vienna. Considering the yeast’s ability to bind to metals and its potential for reuse, she believes, “this method could indeed assist in reducing both the yeast and electronic waste.”

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The scientists washed, froze, dried, and pulverized 20 liters of residue with inactive yeast from a brewery. They then poured some of the yeast into a concoction containing a lab-generated blend of aluminum, copper, nickel, and zinc, and introduced some to solutions with identical metals derived directly from discarded circuit boards. They modified the mixtures’ acidity and temperature to manipulate the sugar molecules’ charge on the yeast organisms’ surfaces. Certain metals are attracted to particular charges on the sugars, allowing this process to direct which metals the yeast attracted and bound. Following each experiment, the scientists extracted the yeast, immersed it in an acid solution to remove the metals, rendering the yeast ready for reuse.

The four tested metals are relatively inexpensive, and most e-waste recyclers currently prioritize recovering more valuable ones such as gold, silver and platinum. But the study’s metals are still beneficial and widely used—which “justifies the recycling process,” says Treavor Boyer, an environmental engineer at Arizona State University. Kerry Bloom, a biologist at the University of North Carolina at Chapel Hill, adds that the yeast’s low price and sheer abundance could make the technique relatively feasible at a large scale if e-waste recycling facilities prove willing to invest in something new. “There are huge vats of yeast that often have nowhere to go once brewers are done with them,” he says. “So this is a fantastic source for it. It’s the master recycler.”

Riis Williams is a New York City–based science journalist who specializes in climate, health and wildlife reporting. She currently serves as Scientific American’s news intern.