DAILY SCIENCE

Researchers have turned beer waste into valuable carbon materials
A simple, low-cost method converts the spent grains from beer brewing into renewable fuel and high-value carbon materials.
December 5, 2019

Here’s a reason to feel less guilty about the beer you’ll be drinking over the holidays. Researchers at Queens University Belfast have found a low-cost technique to convert the leftovers from beer brewing into renewable fuel and high-value carbon materials.

In a study in the Journal of Chemical Technology and Biotechnology, they show that using just two cheap chemicals and heat, they can convert dried grain into two forms of carbon, which have many high-value applications. One, activated carbon, is a highly porous material used in water filters. The other, carbon nanotubes, could find use in things like tough composites, batteries, drug delivery, and computers. The carbon could also be converted into liquid fuels.

Using just 1kg of the grain, the team could produce activated carbon with a surface area that could cover around 100 soccer fields, according to the press release.

Waste from brewing already finds some uses. Leftover yeast goes to making the iconic Australian spread Vegemite. Spent grain, most commonly barley, can be used as animal feed. Still, much of the used and unused barley ends up going to landfill. In the EU alone, breweries throw out around 3.4 million tons of barley a year.

Companies and researchers have more recently come up with other innovative uses for spent grain waste. Some breweries burn their spent grain and used the heat and energy to fuel their production process. Major beer maker AB InBev is converting waste alcohol from its low and no-alcohol beers into biofuel. And Mexico-based E6PR has concocted a way to convert the leftover grains from beer brewing into six-pack rings.

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The Belfast team uses a simple process. They first dry the grain. Then they mix it first with phosphoric acid and then potassium hydroxide, heating and drying after each step. This gives activated carbon. The researchers use this material as the carbon source to make carbon nanotubes via one more processing step.

This technique would allow the use of local resources, reduce emissions and waste, and in the end give a high-value product, said chemist and chemical engineer Ahmed Osman who led the new research. “If we are able to take something that would otherwise be a waste and turn it into a useful biofuel, it can only be a good thing for our planet. It could really help to solve global waste and energy problems.”

Source: Ahmed I. Osman. Upcycling brewer’s spent grain waste into activated carbon and carbon nanotubes for energy and other applications via two‐stage activation. J Chem Technol Biotechnol, 2019.

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