In response to the construction industry’s need to explore alternative raw materials, engineers from RMIT University have found a way to recycle coffee grounds to make concrete 30 per cent stronger.

Published in the Journal of Cleaner Production, the study conducted by RMIT engineers outlines that converting used coffee grounds into biochar through pyrolysis can turn it into a sand-substitute.

The process of pyrolysis involved heating the used grounds at 350 degrees Celsius via a low-energy process, in the absence of oxygen.

Corresponding author and research team leader Professor Jie Li stated that the ongoing extraction of natural sand around the world — typically taken from river beds and banks — to meet the rapidly growing demands of the construction industry has a big impact on the environment.

Some 50 billion tonnes of natural sand are used in construction projects globally every year.

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

Lead author and RMIT University researcher Dr Rajeev Roychand said: “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.

“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,” said Roychand.

Several councils looking for solutions to the disposal of organic waste have shown interest in this work, engaging the RMIT University team for upcoming infrastructure projects incorporating pyrolysed forms of different organic wastes.

Co-researcher Dr Mohammad Saberian said the construction industry needed to explore alternative raw materials to ensure its sustainability.

“Our research team has gained extensive experience in developing highly optimised biochars from different organic wastes, including wood biochar, food-waste biochar, agricultural waste biochar, and municipal solid-waste biochar, for concrete applications,” said Saberian.