Pep in your step: coffee-concrete footpaths cut emissions

Council officers and researchers wear high-vis vests while watching coffee-concrete being poured for a footpath
Image supplied

Freshly brewed coffee-concrete may be coming to a street near you after RMIT University teamed up with Victoria’s Macedon Ranges Shire Council to conduct a world-first coffee concrete footpath trial.

Several other upcoming infrastructure projects around Victoria, Australia, will also turn spent coffee grounds into biochar and transform this waste into a valuable resource.

The RMIT team will partner with Australian-owned BildGroup—a civil infrastructure, asphalt paving and road profiling company—to deliver these circular-economy projects.

Related article: Coffee-boosted concrete is stronger, uses less energy

Organic waste going to landfill, including spent coffee grounds, contributes 3% of greenhouse gas emissions, but Dr Rajeev Roychand and his colleagues at RMIT are set on transforming this waste into a valuable 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% stronger by using coffee biochar made with a low-energy process without oxygen at 350°C. 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,” Dr Roychand said.

Related article: Low-carbon concrete helps clean up coal ash deposits

“Sand is getting scarce over time, and this waste can replace up to 15% of the sand in concrete.”

The researchers will evaluate the performance of the concrete in these trial footpaths in Gisborne, with the aim of supporting the further roll out of this innovation.

“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,” Dr Roychand said.

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