After successful trials in 2024, concrete produced incorporating used coffee grounds has made its debut in a major Victorian infrastructure project
Australia generates 75 million kilograms of ground coffee waste every year, with most of it going to landfills, according to RMIT University.
The university says this makes a decent contribution to the organic waste that goes to landfill, which every year contributes 3 per cent of the nation’s greenhouse gas emissions (GHGs).
Looking to reduce the amount of waste ending up in landfills and the emissions that result, a team from the School of Engineering at RMIT converted waste coffee grounds into biochar for use in concrete.
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Earlier this year, RMIT partnered with the Macedon Ranges Shire Council in Victoria to put it to the test. The world-first trial of coffee concrete was conducted in the construction of a footpath in the regional town of Gisborne, with the trial being hailed as a huge success.
Now, coffee concrete is being applied in the south-east Melbourne suburb of Pakenham, where it is being laid into a footpath as part of Victoria’s Big Build.
Concrete baristas
To make coffee concrete, waste coffee grounds and other organic material must first be converted into biochar to prevent its decomposition.
Lead inventor of coffee concrete and RMIT Postdoctoral Research Fellow Dr Rajeev Roychand says the biochar is created using a low-energy process, without oxygen, at 350 degrees Celsius.
“The spent coffee grounds are roasted instead of burnt, because burning them would lead to more GHG emissions,” Roychand says.
“In the absence of oxygen, and roasted at a 350-degree temperature, a black-coloured coffee biochar is produced.”
Using this method, it was found that biochar made the concrete 30 per cent stronger when used as a replacement for sand in the concrete mix.
Road upgrade
Major Road Projects Victoria (MRPV) and project contractor BildGroup have used the coffee concrete in the Pakenham Roads Upgrade, as a replacement of a portion of the river sand that is normally used with concrete mix.
This is just the latest circular economy initiative delivered for the Pakenham Roads Upgrade, which also includes using foam bitumen and rubber tyre road barriers.
“It’s very exciting collaborating with BuildGroup and MRPV, and it’s great to see coffee concrete getting in-field commercial application,” Roychand says.
“This proactive support plays a significant role in creating a potential for diverting all forms of biodegradable organic waste.”
As part of this project, five tonnes of spent coffee grounds – approximately 140,000 coffees worth of grounds – were converted into two tonnes of useable biochar. This was then laid into the 30 cubic metre footpath along McGregor Road in Pakenham.
BildGroup CEO Stephen Hill says he is happy that his company is the first to bring coffee concrete to a major infrastructure project in the Australian construction industry.
“With the coffee concrete we’ve poured, we’re diverting an estimated 140,000 coffees from landfill and saving over three tonnes of sand, which have enormous environmental benefits,” he says.
“From a triple bottom line perspective, this just makes good business sense.
“When the opportunity arose for us to partner with RMIT to look at this initiative around coffee concrete, we saw it as a great opportunity to help have an impact on the community.
“We’re committed to leaving the world a better place, and we see this initiative as an opportunity to help do that.”
To continue to convert coffee concrete into a commercial reality, RMIT is engaging with a commercialisation partner and with companies in the construction and agriculture sectors that would potentially benefit from using biochar products.
“Melbourne is the coffee capital of the world,” Roychand says.
“It’s very exciting to see the coffee that we love is getting a second shot of life, into concrete biochar that’s converted into construction applications.”