Go to any of the state capitals and the number of pubs will be dwarfed by all the coffee shops and hipster hangouts promising ethically sourced beans and craft nitro brews.
At the same time, 6m tonnes of spent coffee grounds are ending up in landfill each year at a time when processing urban waste is becoming a major challenge for authorities to tackle.
“Finding novel approaches to reduce and recycle this waste, using value-adding applications, is paramount if we are to meet the needs of a growing population,” according to Tien Huynh, a senior lecturer in biosciences and biotechnology at RMIT University in Melbourne.
From coffee to coffee cups
Faced with this challenge, Aussie scientists and startups have been stepping up to the task.
Last year, a PhD student believed he’d found a way to turn coffee waste into biodegradable plastic coffee cups.
Dominik Kopp, then at Macquarie University in Sydney, had developed a method to turn coffee grounds into lactic acid, which could then be used to produce biodegradable plastics. He has since been refining the process.
“Australians consume 6bn cups of coffee every year, and the coffee grounds used to make these coffees are used only once and then discarded,” Kopp said.
“In Sydney alone, over 920 cafes and coffee shops produce nearly 3,000 tonnes of waste coffee grounds every year.
“Ninety-three per cent of this waste ends up in landfill, where it produces greenhouse gases that contribute to global warming.”
He surmised that 50% of coffee grounds are made up of sugars, which are ideal candidates to convert into valuable bio-based chemicals—compounds derived from plant- or animal-based feedstocks, rather than crude oil.
“We were looking for new ways to convert biowaste—whether that be agricultural, garden, paper or commercial food waste—into valuable raw materials that could be used to produce high-value compounds in more environmentally-friendly ways,” said Anwar Sunna, an associate professor of biomedical sciences and Kopp’s supervisor at the time.
The student sourced coffee grounds from one of the coffee shops on the university’s campus and took them back to the lab.
“We assembled a synthetic pathway to convert the most abundant sugar in the coffee grounds, mannose, into lactic acid,” he said.
“Lactic acid can be used in the production of biodegradable plastics, offering a more sustainable and environmentally-friendly alternative to fossil fuel-derived plastics.
“You could use such plastics to make anything from plastic coffee cups to yoghurt containers to compost bags to sutures in medicine,” he added.
Their method was inspired by a metabolic pathway that is thought to exist in an evolutionarily ancient organism, which lives in hot and extremely acidic environments.
Kopp received an award for the idea after presenting his research at the 18th European Congress on Biotechnology last September.
He has since been further refining his conversion pathway, and setting out to improve the yield of lactic acid.
“I think my project is one of many interesting approaches on how to use synthetic biology in a responsible manner for the development of a more sustainable and greener industry that doesn’t rely on crude oil,” Kopp said.
“The simple idea that we are converting waste into a valuable and sustainable product is extremely exciting.”
Building roads
Elsewhere, Swinburne University of Technology engineers have been turning used coffee grounds into building materials for roads.
Arul Arulrajah, a professor of geotechnical engineering and avid coffee drinker, had been investigating the use of recycled materials, such as crushed brick or glass and concrete, for use in road construction.
He said: “I saw the baristas throwing away the used coffee grounds and I thought, why not look at this as an engineering material?”
Professor Arulrajah, with a student, then collected used coffee grounds from cafés surrounding Swinburne’s Hawthorn campus. They dried them in a 50C oven for five days, then sieved the grounds to filter out any lumps.
They then mixed seven parts coffee grounds with three parts of slag—a waste product from steel manufacturing. A liquid alkaline solution was added to bind everything together.
The mixture was compressed into cylindrical blocks that proved strong enough to use as the subgrade material that sits under a road surface.
“On average the cafés we collect from dispose of about 150kg of coffee grounds per week,” said Professor Arulrajah.
“We estimate that the coffee grounds from Melbourne’s cafés could be used to build five kilometres of road per year. This would reduce landfill and the demand for virgin quarry materials.”
Oyster mushroom farm
It’s not just Australian scientists, though, who are coming up with the coffee waste innovations. In 2015, two entrepreneurial health workers left their jobs in Western Australian mines to start Life Cykel, a startup that uses coffee grounds from cafes to cultivate mushrooms.
They now sell mushroom-based extracts, powders and drinks, as well as oyster mushroom home-growing kits, through which Life Cykel made its name, containing spent coffee for the “soil”. These cardboard boxes can be ordered online, allowing customers to watch their fungus grow out of the front of them.
“We had launched our oyster mushroom farm in Fremantle and then chose crowdfunding to expand to Melbourne, so more people who support fresher food and cleaner living behind us,” said co-founder Ryan Creed.
They sell their mushrooms to cafes and restaurants while also taking coffee waste from these places, which in turn saves them the cost of disposal.
“The cafes are very supportive of us using their coffee waste and they do it for free. We are benefiting them and the environment. Plus it’s a feel-good story when the cafe is doing less environmental harm, and of course serving fresh mushrooms on the menus to their customers,” Creed added.
Herself a passionate advocate of finding premium ways to make use of coffee byproducts—in Australia it is said that only 1% of ground coffee is used up in making the drink—RMIT’s Huynh sees spent coffee as a potentially valuable resource.
“With coffee now the second largest commodity worldwide, recycling these nutrient-rich by-products could reduce the amount of organic waste sent to landfill, whilst producing value-adding products,” she said.
