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From coffee to concrete: Researchers offer a new solution

The construction materials industry could hold the key to reducing tonnes of landfill-destined coffee waste in Australia, according to a group of Melbourne engineering researchers.

The project from the RMIT University’s School of Engineering is investigating ways to develop concrete from coffee grounds that are produced from the 1.3 million cups consumed daily across the nation.

Bachelor of Engineering students Senura Kohombange and Anthony Abiad have worked with senior lecturer Dr Srikanth Venkatesan to test and develop ‘coffee bricks’, which they believe have potential real world uses.

The work has initially focused on using coffee waste as a sand replacement in materials that could one day be used in homes, driveways or office buildings. With most concrete mixes containing up to 80 per cent sand, the group found they could replace up to 10 to 15 percent of that with coffee grounds.

“It seems fitting than we’re working on this project in Melbourne, a city known for its great coffee culture,” Kohombange said.

The researchers estimate 2600 cafes in Melbourne alone produce about 156 tonnes of coffee ground waste every month, according to 2017 figures. In addition, sand is the third most used resource behind water and air, while quarries struggle to keep up with demand.

Sand in scarce supply
A frequent coffee drinker, Venkatesan said it was important to find a solution to the waste produced each day.

“Countries like Sri Lanka and India have restrictions on dredging and taking of the resource sand, so it is becoming a scarce material. Even if we replace 10 per cent of sand in the concrete mix, we really should be better off,” he said.

The research was built on the premise that coffee grounds blended well with sand in composting and gardening applications. Others had also previously experimented mixing coffee and concrete with limited success.

Venkatesan said the biggest challenge is ensuring the addition of spent coffee grinds does not reduce the concrete’s strength.

Depending on the proportions, the researchers found coffee grounds could weaken the concrete mix by 20 to 50 per cent, meaning the material would initially be used in non-structural applications. Due to coffee ground being an organic material, the researchers are also testing its durability.

However, Venkatesan said other environmentally friendly products could help bring the material up to full strength. “In addition to the coffee grounds, we can use other recyclable materials like quarry dust and copper slag to take the strength to 100 per cent,” he said.

The research project featured at RMIT’s EnGenius event on 23 October.


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