The quest for effective recycling solutions intensifies as the world's dependence on electronics continues to grow. Electronics often contain a mix of metals like aluminium, zinc, and copper, which pose challenges to proper separation and recycling. Recent research has found a remarkable solution in spent brewer's yeast, a byproduct of beer production and a key ingredient in Marmite.
About the discovery
In groundbreaking experiments, scientists have demonstrated that spent brewer's yeast (by-product of beer production) can be used multiple times to extract metals such as aluminium, zinc, and copper from solutions. The results were impressive when tested with a polymetallic waste stream: more than half of the copper and a remarkable 90 per cent of the zinc were successfully recovered.
Recycling electronic equipment, especially at the end of its usable life, is critical to ensure that the rare natural materials used in its production are fully utilised. However, the complex mix of metals in electronic waste makes recycling a formidable challenge.
This new method, employing spent brewer's yeast, offers a selective and environmentally friendly approach to extracting metals from waste streams. Moreover, the yeast can be reused multiple times, enhancing the sustainability and eco-friendliness of the entire process.
"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. 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," added Anna Sieber, Study First Author and PhD Fellow, K1-MET.
Result of the test
The scientists achieved impressive results from their tests on the metal solutions. They were able to extract over 50 per cent of aluminium, more than 40 per cent of copper, and over 70 per cent of zinc. Furthermore, when the yeast was applied to the polymetallic waste stream, they recovered over 50 per cent of copper and more than 90 per cent of zinc.
"Electronic waste is difficult to recycle because it is very heterogeneous. Getting the metals in solution is a first step, but the selective recovery remains a challenge. Compared to processes such as chemical precipitation, biosorption using spent brewer's yeast presents a cheap and environmentally friendly approach," said Dr. Klemens Kremser, Study Corresponding Author and Postdoctoral Researcher at the University of Natural Resources and Life Sciences.
Interestingly, temperature variations had minimal impact on efficiency, except for zinc, which boosted the recovery rate by 7.6 per cent. Similarly, alterations in pH levels had little effect on most of the metal solutions, except for aluminium, which saw a remarkable 16 per cent increase in recovery efficiency.
The scientists successfully recycled the yeast up to five times to reclaim various metals, observing minimal impact on its metal recovery capabilities. Yet, they caution that extensive research in practical, real-world environments is essential before implementing this metal recovery technique on an industrial scale.
Reason for using brewer's yeast
Numerous methods exist for separating the diverse metal components in electronic waste, including using additional biosorbents—biological materials capable of absorbing pollutants. However, these methods often come with significant drawbacks. For instance, chemical precipitation can produce polluted slag, while biochar, a charcoal-like biosorbent, poses challenges in its removal from wastewater.
In response to these challenges, scientists turned to a surprising yet effective solution: brewer's yeast. Spent brewer's yeast, a common byproduct of beer production, is inexpensive and readily available, making it an attractive option. The study received funding from Austria's COMET (Competence Center for Excellent Technologies) program.
How the test was done
The researchers conducted their study by collecting 20 litres of spent brewer's yeast. They then isolated the biomass from the remaining brewing residue and dried it. What follows is a fascinating process: due to electrostatic interactions, the yeast's surface can attract metal ions—a phenomenon known as sorption. By manipulating the solution's pH, scientists could alter these interactions. This adjustment allowed the yeast to adsorb a greater quantity or different types of metal ions, depending on the composition and pH of the solution.
The scientists assessed yeast biomass against commercially significant metals such as zinc, aluminium, copper, and nickel. They scrutinised each metal solution under different pH and temperature conditions to determine the feasibility of enhancing interactions and extracting additional metals. Moreover, the scientists subjected the yeast to a real polymetallic waste stream for further evaluation.
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