A group of researchers at RMIT University has presented fresh evidence that everyday organic waste, specifically used coffee grounds, can be transformed into construction materials that contribute to reducing the carbon footprint of infrastructure development.

Their latest life cycle assessment reveals that biochar made from spent coffee grounds can help produce a lower carbon concrete while maintaining the strength gains demonstrated in previous laboratory trials.

In earlier experiments, the RMIT team had produced a fine biochar by heating used coffee grounds to about 350°C without oxygen. When used to replace 15% of sand in the concrete mix, it boosted the 28-day concrete strength by roughly 30%, pointing to a practical way to reduce pressure on natural sand supplies.

*The team’s coffee biochar (left) next to spent coffee. Credit: Carelle Mulawa-Richards, RMIT University*

The new study, led by Dr Jingxuan Zhang and Dr Mohammad Saberian, expands on this research with a cradle-to-grave analysis covering carbon emissions, resource use, and environmental impacts from production through to end of life.

Their assessment found life cycle carbon dioxide reductions of 15%, 23%, and 26% when coffee biochar replaced 5%, 10%, and 15% of sand, respectively. It also reported up to 31% lower fossil-fuel use and improved outcomes for rivers and lakes. These results support Australia’s transition towards a circular economy by turning abundant organic waste into functional construction materials, reducing reliance on natural sand, and building public engagement with resource recovery.

*Dr Rajeev Roychand (left) and Professor Jie Li add coffee biochar into a concrete mixer in their lab at RMIT University. Credit: Carelle Mulawa-Richards, RMIT University*

The findings strengthen the case for real‑world trials, says Dr Zhang. “We showed that coffee biochar can cut concrete’s carbon footprint in the scenarios we assessed, while earlier trials demonstrated strength gains using the same approach.”

Professor Chun-Qing Li, who provided guidance to the team, notes that the innovation turns organic waste into a practical ingredient for lower‑carbon infrastructure. “Using moderate amounts of coffee biochar offers a clear, measurable pathway to lower‑impact concrete,” he observes.

Dr Saberian informs that the team is already engaging with industry as well as state and local governments on construction projects.

“Next steps include larger pilots, mix optimisation and alignment with standards so projects can adopt this confidently,” he says. “We welcome collaboration on supply chains and field deployments.”

The study, ‘Carbon footprint reduction in concrete using spent coffee grounds biochar: a life cycle perspective’, is published in the International Journal of Construction Management (DOI: 10.1080/15623599.2025.2584549).

Jingxuan Zhang, Mohammad Saberian, Rajeev Roychand, Jie Li, Chun-Qing Li, Guomin Zhang and Dilan Robert are authors on the paper.

Main image: Council officers and the RMIT research team were present for the pour of the coffee concrete for the footpath trial in Gisborne. Credit: Bodey Dittloff, Macedon Ranges Shire Council

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