Here's another reason to enjoy that morning coffee: the used grounds can be used in road-building materials.
Engineers from China, Thailand and Australia developed an environmentally friendly recipe suitable for road construction using coffee grounds collected from cafes and blast furnace slag from iron production.
"This new material, derived from major sources of waste products, would significantly reduce landfill demand and carbon footprint," says Arul Arulrajah from Australia’s Swinburne University and co-author of the study.
It's no wonder coffee grounds are an attractive target for scientists keen to develop "green" construction materials, which are usually made of matter destined for landfill. In 2008, more than seven million tonnes of coffee grounds were produced with most going straight in the bin.
So Arulrajah and his team collected used coffee grounds from cafes in Melbourne, Australia, mixed them up with various ratios of slag, compressed their concoctions into blocks and tested them in a special pressurised cylinder to find their buckling point.
For subgrades – the foundation material underneath road pavement layers – 70% coffee grounds and 30% slag, mixed with a solution of 70% sodium silicate and 30% sodium hydroxide, produced the strongest product, comparable to common cement, with relatively low alkaline levels and almost no carbon emissions.
They also tested ratios incorporating fly ash, a byproduct from coal-fired power plants, but those mixtures weren't as strong.
While they've "ticked off the strength requirements", Arulrajah says, there's still work to do on the mix before it's rolled out, such as seeing how it fares long-term under the pressure of traffic.
But, he adds, if all the coffee grounds in Melbourne were incorporated in his mix, he estimates "up to five kilometres of roads can be constructed per year".
The work was published in Construction and Building Materials.
Originally published by Cosmos as Cafe to construction site: coffee grounds can be used to build roads
Phil Ritchie is a Melbourne-based journalist.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.