A group of engineers at RMIT have found a way to enhance the strength of concrete, utilising roasted used-coffee grounds in a bid to prolong the material’s lifespan and reduce waste, while preserving sand.

The researchers report that coffee grounds are able to strengthen concrete by 30 percent via transforming the grounds into biochar, which involves a low-energy process called pyrolysis. The process sees organic waste heated to 350 degrees without oxygen.

“The disposal of organic waste poses an environmental challenge as it emits large amounts of greenhouse gases including methane and carbon dioxide, which contribute to climate change,” says the research’s Lead Author Rajeev Roychand, from RMIT’s School of Engineering.

“The inspiration for our work was to find an innovative way of using the large amounts of coffee waste in construction projects rather than going to landfills – to give coffee a ‘double shot’ at life.”

Australia generates 75 million kilograms of ground coffee waste every year – most of it goes to landfills. Globally, 10 billion kilograms of spent coffee is generated annually. The coffee grounds could serve as a stronger, more sustainable alternative to sand.

“Several councils that are battling with the disposal of organic waste have shown interest in our work,” Roychand says.

“They have already engaged us for their upcoming infrastructure projects incorporating pyrolysed forms of different organic wastes.”

Joint Lead Author and a Vice-Chancellor’s Indigenous Postdoctoral Research Fellow at RMIT, Shannon Kilmartin-Lynch, says that the wider construction industry could assist in making the ‘coffeecrete’ commonplace.

“The concrete industry has the potential to contribute significantly to increasing the recycling of organic waste such as used coffee. Our research is in the early stages, but these exciting findings offer an innovative way to greatly reduce the amount of organic waste that goes to landfill.”

RMIT Professor Chun-Qing Li says swapping sand for coffee grounds is suitable for a sustainable future.

“There are critical and long-lasting challenges in maintaining a sustainable supply of sand due to the finite nature of resources and the environmental impacts of sand mining,” he says

“With a circular-economy approach, we could keep organic waste out of landfill and also better preserve our natural resources like sand.”

The researchers plan to develop practical implementation strategies and work towards field trials. The team is keen to collaborate with various industries to develop their research. The paper has been published in the Journal of Cleaner Production. To read, click here.

Image (L-R): Dr Rajeev Roychand, Dr Mohammad Saberian and Dr Shannon Kilmartin-Lynch with Jordan Carter, Co-founder of the Indigenous-owned Talwali Coffee Roasters.