Scientists still haven’t cracked how to turn water into wine—but they might have figured out how to turn beer into clean water. From the literal ashes of breweries’ by-products, researchers made a charcoal-like substance that clings to bacteria, and they are using it to test a new way of filtering water.
In a recent study, scientists heated up a common waste product from beer making called spent malt rootlets, which are little sprouts that grow from barley during the malting process, to produce biochar, a porous material created from burned organic matter. They found that when they mixed this substance with sand and sent water through it, the biochar was able to remove around five times as much Escherichia coli bacteria as a filtration system that used only sand.
Sending water through sand filtered bacteria like a colander: by physically stopping microbes from moving through. But when the team used a sand mix that was 10 percent biochar, the biochar actively glommed on to slow microbes’ passage.
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Groundwater is constantly moving through soil. There it can become contaminated with agricultural waste or fecal matter—potentially infecting any humans who drink it. Adding biochar to certain soils could offer a public health solution and “a sustainable approach for water remediation and the protection of groundwater,” says Ioannis Manariotis, senior author on the study and an environmental engineer at the University of Patras in Greece.
Manariotis and his team have also tested whether waste from olive oil and coffee production can have similar water-purifying effects. Now that the researchers have found the beer by-product can filter out bacteria in laboratory conditions, he says, they plan to test its efficacy under more unpredictable real-life conditions. The results were published in the journal Biochar.
Using brewery waste for water filtration in this way is a “proof of concept,” says Alcina Johnson Sudagar, an independent chemistry researcher who studies other beer-making by-products and was not involved in the study. But the repurposing of by-products from this industry for other applications is already common, she says. Leftover brewery grain is frequently used to make animal feed, and other research suggests beer-making by-products can be used for everything from sunscreen to electricity. The brewing process can have up to 11 steps, and each step produces organic waste materials with different chemical makeups—potentially ideal for different uses.
Sudagar says she hopes Manariotis and his team continue to study biochar. Her most pressing question is whether the material can be used more than once for filtration. If it can trap bacteria only once, it quickly becomes waste again, negating its value as a consistent filtration system or sustainable brewery by-product.
As the global beer industry grows, these new and innovative ways of using the by-products are crucial to sustainability, Sudagar adds. “It’s important to continue because the waste produced will keep increasing, and you would need different applications,” she says. “You cannot just send it to one place and say that we are done with it.”
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