Nanogirl Michelle Dickinson: Drink up, your beer could also heat your barbecue

Brewing waste can be turned into high-value materials that are in demand around the world. Photo / Getty Images

COMMENT

Making up more than 60 per cent of all alcohol sold, beer is the drink of choice for many Kiwis. With a new survey by the Brewers Association finding that New Zealand has more commercial breweries per capita than the US, UK or Australia, we not only make a lot of beer but also a lot of waste as part of the brewing process. This week researchers have found a new way to turn this waste into activated carbon, meaning beer-related products could be used to filter dirty water, cook your food and heat your home.

Making beer requires only four ingredients, grain, hops, yeast and water. The process starts with the grain and while wheat, corn and rice can be used, typically barley is the grain of choice. The barley is added to water turning it into malted barley and the seed is encouraged to grow to convert its starch into a sugar as it does. Once this happens the malted barley is heated or roasted to stop it growing and the intensity of this heat determines much of the taste of a beer.

The sugar is used by the yeast for fermentation, the hops add bitterness and the water turns it all into a flavourful, drinkable liquid. Before it gets to your lips, the solid grain particles are filtered out leaving behind what's known as "spent grain", which accounts for up to 85 per cent of brewery waste and makes up more than 40 million tonnes of brewing waste globally each year. This grain is a rich source of fibre and protein making it ideal for farmers, who can feed livestock such as cattle and pigs with it. However, as a wet, soggy product it needs to be delivered to the animals quickly before it goes off, which isn't practical for many brewers or farmers. With the application of heat to dry off the large volume of water in the spent grain, the remaining powder can be ground into a flour to make flavourful breads, pretzels and dog biscuits. Although these solutions help to prevent the waste product from going to landfill, the time and energy required to create what is a relatively low-value product might not be enough of an incentive to motivate brewers to be smart with their waste.

Making beer requires only four ingredients, grain, hops, yeast and water. Photo / File

This week, research published in the Journal of Chemical Technology and Biotechnology showed a simple two-stage chemical process that can be added to the dried grain waste to create activated carbon and carbon nanotubes, both high-value materials which are in demand around the world.

The process is simple and washes the dried beer waste grain firstly with low-cost phosphoric acid and then potassium hydroxide. The new material can then be compressed to form barbecue charcoal briquettes or fuel pellets to heat homes or ground up to make activated carbon for water filters. In initial tests, the activated powder was able to remove 77 per cent of heavy metals such as lead within the first hour of testing. While carbon is available from other sources in a liquid carbon and solid biocarbon form, all are shipped in from overseas.

This synthesis of a high-value product from locally produced waste is a great example of how a successful circular economy could improve sustainability practices through reducing emissions while also driving up financial profits when it comes to the production of beer.

With 1kg of activated grain material able to spread across 100 football pitches, the potential to create much higher value products from beer brewing could end up actually being more lucrative in the long run than the beer itself.