Australians love their coffee – an estimated 1.3 million cups of coffee are drunk daily across the nation. 

But with that comes tonnes of waste from used coffee grinds, the majority of which end up in landfill.

This dark side to our love affair could take a lighter turn thanks to a group from RMIT University, who have looked at the potential of coffee waste to replace some of the sand content used in concrete for a variety of applications, from housing to driveways.

Most concrete mixes contain up to 80 per cent sand – the third most used resource on the planet. 

But this abundant resource can’t keep up with current demand, and extracting it from places with fragile ecosystems can have detrimental environmental consequences. 

The group found they could replace up to 10 per cent of sand in a concrete mix with coffee grounds and have produced sample ‘coffee bricks’, which will be on display at RMIT’s EnGenius event on 23 October.

The event will see more than 1000 final year engineering students from 11 disciplines showcase their projects and products to industry and the public, from coffee bricks to three-digit prosthetic hands.

Dr Srikanth Venkatesan, a senior lecturer in the School of Engineering, tested and developed the coffee bricks with the help of engineering students Senura Kohombange and Anthony Abiad.

Dr Venkatesan says as a regular cappuccino drinker he was inspired to find a solution to the waste he was making each day. 

‘The biggest challenge is ensuring the addition of spent coffee grinds does not lead to a reduction in strength of concrete, and this is the focus of further testing and development to make this product viable for use in real-world applications,’ he says. 

Engineering honours students Senura Kohombange says it seems fitting they are working on the project in Melbourne, given the city’s thriving coffee culture. 

‘We are very excited to present the project, share the idea with others and showcase how some innovative thinking can turn a waste product into an everyday construction material,’ he says.

There were an estimated 2600 cafes in the City of Melbourne alone in 2017, producing about 156,000kg of coffee-ground waste every month. 

Executive Dean School of Engineering, Distinguished Professor Adrian Mouritz said RMIT was proud to produce the next generation of engineers who were designing solutions to real world problems.

‘EnGenius takes engineering out of the classroom and brings it to life,’ he says. ‘Many of these projects focus on making our world a better place, be it more inclusive or more sustainable.

‘Meaningful partnerships and events like EnGenius provide opportunities for industry to meet its future workforce and students to connect with employers.’