Brewer's Waste Can Make Recycling E-Waste Easier
Humans have enjoyed beer for centuries, and now scientists discovered the leftover yeast from brewing beer has a surprisingly eco-friendly purpose
Hiya!
I can’t explain it, but beer has been a favorite beverage of our species for over 10,000 years and remains popular worldwide today. The Pacific Northwest, where I was born and raised, is known for its craft beers. Breweries are everywhere here; there are at least 70 in Portland, Oregon alone — meaning you could go to a different brewery every month for five years and still not visit them all.
Brewing beer requires several stages and lots of patience; one batch can take two to eight weeks. While the finished product is tasty, the process leaves behind plenty of yeast byproducts. But now scientists have discovered that this discarded waste can be used to make recycling e-waste more efficient. This is a big deal because electronic waste is a growing problem.
The Challenge
Millions of electronic devices are discarded every year as cell phones, computers, televisions, and medical equipment become obsolete or replaced. These discarded devices are called “e-waste,” which the World Health Organization (WHO) says is the “fastest growing solid waste stream in the world.”
E-waste can be dangerous to human health and the environment when it’s not treated, disposed of, or recycled properly. Unfortunately, the UN’s fourth Global E-waste Monitor (GEM), released in March 2024, found that e-waste is growing five times faster than the recycled rate. The amount has increased 82 percent between 2010 and 2022 and is projected to rise another 32 percent by 2030.
Meanwhile, the same report found that only 22.3 percent, less than a quarter, of the e-waste from 2022 was documented as being properly collected and recycled. According to The United Nations Institute for Training and Research, this means there was “$62 billion worth of recoverable natural resources unaccounted for and increasing pollution risks to communities worldwide” during 2022 alone.
There are a few reasons to explain these less-than-eco-friendly statistics, but a big one is that e-waste is notoriously challenging to recycle properly because it’s hard to separate the many different metals in the waste.
This isn’t a new issue; experts have already created several options for separating metal components from electronic waste, but none of them are particularly good or ideal solutions.
One such method is to use biosorbents — biological materials that can absorb pollution, including heavy metals. The problem is that chemical precipitation creates toxic slag, for one thing, and biochar, which is similar to charcoal, is challenging to isolate in wastewater. Meanwhile, techniques like pyrometallurgy, a high-energy melting process, can release toxic fumes.
But now, Anna Sieber, a Doctoral student and research assistant in the Department of Agrobiotechnology, along with Professor of Biotechnology Georg M. Guebitz and other colleagues at the University of Natural Resources and Life Sciences (BOKU) in Vienna, Austria, thinks they have found a better biosorbent solution: brewer’s yeast.
A Solution
The leftover yeast after brewing beer is a single-cell fungus called Saccharomyces cerevisiae, which is also used in bread making. It’s also often mixed with seasonings to create a paste called Marmite, which is spread on toast and eaten like a snack. Its bitter, earthy flavor may be an acquired taste, but it’s popular in the United Kingdom.
Still, most brewer’s yeast is a wasted byproduct, which means it’s widely available — and cheap — which inspired Siber to use it as a biosorbent solution for heavy metals. She explains that,
“Getting the metals in solution is a first step, but the selective recovery of the metals remains a challenge. Compared to processes such as chemical precipitation, biosorption using spent brewer's yeast presents a cheap and environmentally friendly approach.”
The Study
To test the idea, the researchers collected 20 liters of inactive brewer’s yeast, which they froze, dried, and ground up. Then, the team added some of the yeast to their solutions, which included aluminum, nickel, zinc, and copper — all of which are economically important metals.
After this, they added another solution with the same metals, except these came from scrapped circuit boards. The electrostatic exchanges between the yeast’s surface and the metal ions allow the metal to stick to the yeast. In other words, static interactions allow the yeast to absorb the metals.
Next, the team adjusted different variables, including temperature and acidity levels of the sugar molecules making up the yeast’s surfaces. Different metals are attracted to specific charges on the sugars, and changing the pH and temperature levels allowed the researchers to dictate which metals the yeast attracted and whether it was possible to strengthen the interactions to recover more metals.
They also tested the yeast against a polymetallic waste stream already in use. After each experiment, the team soaked the yeast in an acid bath to extract the collected metals.
The Results
The scientists recovered over 50 percent of aluminum, more than 40 percent copper, and over 70 percent zinc from the circuit board metal solutions. Further, the yeast absorbed more than 50 percent of aluminum and over 90 percent of zinc from the polymetallic waste stream they tested.
Zinc responded the most to temperature changes, which increased the absorption rate by 7.6 percent. At the same time, aluminum had the most significant response to changes in pH levels, leading to an increased recovery rate of 16 percent.
Sieber, the first author of an article published in Frontiers, explains:
"We demonstrated high metal recovery rates from a complex metal solution using an environmentally friendly and cheap biomass. Yeast biomass is considered a safe organism, and the demonstrated reusability of the biomass makes it an economically feasible approach."
That’s right. The scientists discovered a bonus benefit to using brewer’s yeast to extract metal from e-waste.
A Bonus Benefit
Remarkably, the scientists discovered that the yeast can be recycled and used again without significantly impacting its binding strength — not just once or twice, but up to five times — for different metals. Sieber told Frontiers:
"The metals can be removed from the yeast surface by acid treatment and thus could be recycled. It would be interesting to investigate potential applications for these reclaimed metals."
As exciting as the potential is, the scientists caution that more research is needed before the technique can be used on an industrial scale. Postdoctoral researcher Klemens Kremser, who was involved in the study, explains that,
"The metal removal process in this study was optimized for the four metals in question. The concentration of potentially interfering metal ions was very low in our starting solutions, but this would be important to consider when applying this approach to different mixed metal solutions."
Still, the discovery is exciting. Sieber points out to Riis Williams of Scientific American that, “In Austria, we produce a lot of beer and have a lot of brewer’s yeast that goes to waste.” So, knowing that brewer’s yeast can absorb metals, and more than a couple of times at that, “we think this method could actually help limit both the yeast and electronic-waste streams,” she says.
Most e-waste recyclers prioritize more valuable metals, such as gold, silver, and platinum, than the relatively inexpensive ones the researchers tested. However, aluminum, zinc, copper, and nickel from the study are still widely used in today’s electronics, so the process is still highly valuable.
Biologist Kerry Bloom at the University of North Carolina at Chapel Hill told Williams that yeast’s low costs and sheer abundance help make the process “relatively feasible at a large scale,” that is, if e-waste recycling centers are willing to invest in a new system. He says:
“There are huge vats of yeast that often have nowhere to go once brewers are done with them. So this is a fantastic source for it. It’s the master recycler.”
Perspective Shift
The research I just told you about was published in March, and by May, scientists at MIT and Georgia Tech found another use for the same concept and devised a way to make the technique even more efficient.
The researchers created a water filter by packaging brewer yeast inside hydrogel capsules. The porous hydrogel allows the water to flow freely while the yeast captures the lead, and the water comes out clean and ready to drink on the other side.
Afterward, the yeast can be cleaned and encapsulated again for use again. The yeast is biodegradable, benign, and biobased, making it an even more attractive solution for filtering drinking water.
All this research seems like a win-win-win-win to me. It helps reduce our e-waste, improve drinking water, upcycle previously discarded byproducts by tapping into a natural process of yeast fungi, and, of course, gives us yet another reason to continue brewing beer for as long as possible.
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Drink more beer, mend the earth.
I'm all in!
Excellent news! Thanks