Researchers in Australia have turned used coffee grounds into a material for constructing roads.
The team at Swinburne University of Technology’s Centre for Sustainable Infrastructure in Melbourne had been looking at the use of recycled materials in roads such as old brick, glass or concrete.
Coffee drinker Arul Arulrajah, who leads the geotechnical group, said: “I see the baristas throwing away the used coffee grounds and I think, ‘why not look at this as an engineering material?’”
Together with PhD student Teck-Ang Kua, they collected used grounds from local cafés and then dried them in a 50°C oven for five days and sieved out any lumps. Seven parts of grounds were then mixed with three parts of slag, and a liquid alkaline solution was added to bind the mixture. It was then compressed into cylindrical blocks and testing found it was strong enough to use as the subgrade material under a road surface.
“On average, the cafés we collect from dispose of about 150kg of coffee grounds per week,” said Arulrajah. “We estimate that the coffee grounds from Melbourne’s cafés could be used to build 5km of road per year. This would reduce landfill and the demand for virgin quarry materials.”
The findings were published in the journal Construction and Building Materials. The research was carried out in collaboration with Suranaree University of Technology, Thailand; Southeast University, Nanjing, China; and Shanghai Jiao Tong University, China.