Belfast team turns brewery waste into valuable carbon

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Huge waste stream of used barley could become a source of carbon-based industrial fuel and filter material

Engineer readers may be surprised to read that carbon is a valuable resource. We, along with many other media outlets, commonly use “carbon” as a shorthand for emitted carbon dioxide and talk a lot about reducing it, to the annoyance of some of our commenters.

carbon
Charcoal briquettes could be made from draff - the waste barley grain from brewing beer and distilling whisky

But elemental carbon does indeed have value. “Liquid forms of carbon are normally shipped to the UK from the Middle East, and solid biocarbon, in the form of wood pellets is shipped from the US and elsewhere,” said Ahmed Osman, from the School of Chemistry and Chemical Engineering at Queen’s University Belfast, who has led a project to convert brewery waste into activated carbon and carbon nanotubes, two forms of the element of particular value to industry.

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Breweries and distilleries in the European Union throw out 3.4 million tonnes of barley every year, spent after being used to make alcoholic beverages. Osman’s team reports in the Journal of Chemical Technology and Biotechnology a novel and low-cost process for turning this mountain of soggy grain into valuable carbon.

“There are only a few steps in our approach – drying the grain out and a two-stage chemical and heat treatment using phosphoric acid and then a potassium hydroxide wash, both of which are very low cost chemical solutions. This then leaves us with activated carbon and carbon nanotubes – high value materials which are very much in demand,” Osman said.

The researchers converted 1kg of grain into enough activated carbon to spread across 100 football pitches. The solid material could be used to make fuel pellets to burn for energy, charcoal briquettes as a commercial product for barbecues, or parts for water filters, Osman suggested.

“Using this new technique, we can utilise more locally produced resources, reduce emissions linked with the agriculture sector, and we are also creating a high-value product. 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,” he said.

The synthesis of value-added products from barley waste is a prime example of the circular economy, by taking a waste food by-products and creating a high-value product. It has benefits to the environment and society through economic and social opportunities,” Osman added.