Engineers in Australia have found a way of making stronger concrete with roasted used-coffee grounds.
Lead author Dr Rajeev Roychand from RMIT University said the team developed a technique to make concrete 30 per cent stronger by turning waste coffee grounds into biochar, using a low-energy process without oxygen at 350 degrees Celsius.
“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,” Roychand said.
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.
Roychand said several councils that are battling with the disposal of organic waste have shown interest in their work.
“They have already engaged us for their upcoming infrastructure projects incorporating pyrolysed forms of different organic wastes,” he said.
Pyrolysis involves heating organic waste in the absence of oxygen.
Joint lead author and RMIT Research Fellow, Dr Shannon Kilmartin-Lynch, said construction industries around the world could play a role in transforming this waste into a valuable resource.
“Inspiration for my research, from an Indigenous perspective, involves Caring for Country, ensuring there’s a sustainable life cycle for all materials and avoiding things going into landfill to minimise the impact on the environment,” Kilmartin-Lynch said.
“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.”
Corresponding author and research team leader Professor Jie Li said the coffee biochar can replace a portion of the sand that was used to make concrete.
“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,” Li said.
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,” Li said.
“With a circular-economy approach, we could keep organic waste out of landfill and also better preserve our natural resources like sand.”
Co-researcher Dr Mohammad Saberian said the construction industry needed to explore alternative raw materials to ensure its sustainability.
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.
Read the research paper: https://doi.org/10.1016/j.jclepro.2023.138205