Freshly brewed coffee concrete may be coming to a street near you after RMIT University teamed up with Macedon Ranges Shire Council to conduct a world-first coffee concrete footpath trial.
Several other upcoming infrastructure projects around Victoria will also turn spent coffee grounds into biochar and transform this waste into a valuable resource for the construction industry.
The RMIT team will partner with Australian-owned BildGroup – a civil infrastructure, asphalt paving and road profiling company – to deliver the circular-economy projects.
Organic waste going to landfill, including spent coffee grounds, contributes three per cent of greenhouse gas emissions, but Dr Rajeev Roychand and his colleagues at RMIT are set on transforming this waste into a resource for the construction industry.
Organic waste cannot be added directly to concrete because it would decompose over time and weaken the building material. To overcome this challenge, the team has developed a technique to make concrete 30 per cent stronger by using coffee biochar made with a low-energy process without oxygen at 350 degrees Celsius, to give the drink-additive a “double shot” at life and reduce waste going to landfill.
They use a similar technique to turn other organic waste, including wood chips, into biochar that can also be used to make stronger concrete.
Australia generates 75 million kilograms of ground coffee waste every year – most of it goes to landfills, but it could replace up to 655 million kilograms of sand in concrete because it is a denser material. Globally, 10 billion kilograms of spent coffee is generated annually, which could replace up to 90 billion kilograms of sand in concrete.
Roychand said coffee and wood-chip biochar can replace a portion of the river sand that was used to make concrete, and the team was collaborating with the council to trial both types of biochar in concrete footpaths in Gisborne.
“It’s very exciting to see this world-first trial of our coffee and wood-based biochar in these footpaths collaboration with Macedon Ranges Shire Council,” said Roychand from the School of Engineering.
“Sand is getting scarce over time, and this waste can replace up to 15 per cent of the sand in concrete.”
Shane Walden, Council’s Director of Assets and Operations, said residents won’t see or smell any difference in the concrete product.
“It’s really important for council to be involved in projects such as this and to be working closely hand in hand with universities such as RMIT,” Walden said.
“This not only helps improve the knowledge level of our contractors and our staff, but it also has lots of other benefits that are important to our community.
“This includes helping the environment, acting sustainably and, most importantly, reducing waste to landfill and having a circular economy.”
Turning coffee concrete into a commercial reality
The researchers will evaluate the performance of the concrete in the trial footpaths in Gisborne, with the aim of supporting the further roll out of the concrete.
“We are currently working in the supply chain sector so that we can make this research into a mainstream product for commercial applications, and we’re not only looking into coffee – we’re expanding this into all forms of different organic waste,” Roychand said.
“Every biochar produced from a different organic material comes with varying composition, in addition to the difference in carbon content, particle size and absorbency, that can boost the performance of concrete in a range of ways.”
There are potential cost savings for construction companies and concreters if this RMIT innovation can be integrated into the supply chain.
The trial with Macedon Ranges Shire Council did not reduce the amount of cement normally used to make concrete for footpath projects, but the RMIT team plans to experiment with using less cement.
Support for the research
The authors acknowledge the support from ARUP Australia Pty Ltd, Earth Systems Pty Ltd and RMIT University, including the Strategic Capability Deployment Fund, Rheology and Materials Characterisation Laboratory, the X-Ray Facility and the Microscopy and Microanalysis Facility.
The team has published several peer-reviewed publications that provide evidence and analysis of their results related to the trials with Macedon Ranges Shire Council.
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