Beer Might Help Us Recycle Electronic Waste

Scientists have figured out a way to use the leftovers from brewing beer to remove heavy metals from electrical recycling waste.

The metal waste that comes from the recycling of electrical products is notoriously difficult to treat, as the mixture of metals is complicated to separate.

Now, however, brewer’s yeast may be used to filter out the metals from the electrical waste streams, according to a new paper in the journal Frontiers in Bioengineering and Biotechnology.

“Electronic waste is difficult to recycle because it is very heterogeneous,” paper author Klemens Kremser, a biotechnology researcher at the University of Natural Resources and Life Sciences in Vienna, said in a statement. “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.”

While there are other methods of filtering out heavy metals, including using biological materials called biosorbents to mop up the pollution, and chemical precipitation, these approaches have several downsides, such as producing hard-to-remove or toxic byproducts themselves.

Brewer’s yeast is a byproduct of the beer-making process, and is the same ingredient used to make Marmite. It is cheap, widely available, and can even be reused. It can filter out heavy metals using a process called adsorption, which arises due to electrostatic interactions between the surface of the yeast and metal ions. By changing the pH of a solution of yeast and metal, the yeast can adsorb more, or different, metal ions.

According to the paper, the researchers separated out the biomass from 20 liters of used brewer’s yeast, which they used to test its ability to separate out zinc, aluminum, copper and nickel at a range of temperatures and pHs.

Over 50 percent of the aluminum, 40 percent of the copper and 70 percent of the zinc in the test solutions were recovered in the experiments, the paper revealed. When the yeast was used on a mock metal waste stream, akin to one from an electrical recycling plant, over 50 percent of copper and 90 percent of zinc were retrieved.

“Using waste biomass for metal recovery is not a completely new process, but the selectivity of biosorption processes is a key factor for efficient metal recovery from polymetallic waste streams,” paper author Anna Sieber, a fellow at Austrian metallurgical research center K1-MET, said in the statement.

“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,” she said.

Additionally, the researchers found that changing the pH only had an impact on the adsorption of aluminum, which its recovery efficiency was improved by 16 percent, and changing the temperature only impacted zinc recovery, increasing the recovery rate by 7.6 percent.

The yeast itself was able to be recycled between uses, with the scientists using it up to five times to recover different types of metal.

The researchers hope that this technique could be used to reclaim metals lost in the electrical recycling process, and prevent heavy metal pollution.

“The metals can be removed from the yeast surface by acid treatment and thus could be recycled,” said Sieber. “It would be interesting to investigate potential applications for these reclaimed metals.”

However, much more research needs to be done into how this yeast would be applied on an industrial scale.

“The metal removal process in this study was optimized for the four metals in question,” said Kremser. “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.”

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