How your morning coffee leftovers could turn into concrete

Two years later, the team of RMIT engineers launched their first coffee concrete trial in Gisbourne, Victoria.

Collaborating with Macedon Ranges Shire Council, Dr Roychand and his team converted spent coffee grounds into an 11-metre footpath panel.

Turning coffee into concrete was part of a project to reduce organic waste in landfills, Dr Roychand said.

"There is a huge amount of organic waste, which is ending up in landfill which can be transformed into a high value product," he said.

Australia produced 48 million tonnes of organic waste between 2021 and 2022, according to the Department of Climate Change, Energy, the Environment and Water.

Each year organic waste in landfills totals three per cent of Australia's greenhouse gas emissions, which is 13 million tonnes.

Dr Roychand said discarded coffee waste made up 75,000 tonnes of Australia's organic waste.

He said while coffee leftovers were used for plant nutrition, there was still a significant amount not being utilised.

"We were approached by some companies who are collecting coffee grounds, in multiples of tonnes every week, and they are looking for some solution to that," he said.

Used coffee grounds are converted into biochar, a lightweight black residue similar to charcoal, by heating the substance to 350 degrees without oxygen.

"We are preserving carbon, we are not burning it and we are using the process in absence of oxygen, we are basically sequestering carbon," he said.

The coffee biochar replaced 15 per cent of sand typically used in concrete, and created 30 per cent stronger concrete, Dr Roychand said.

By producing stronger concrete, Dr Roychand said there was an opportunity to reduce the amount of cement content in concrete, which could lower emissions.

"Cement is produced at 1500 degrees centigrade temperature and has a very high carbon footprint in itself," he said.

Dr Roychand said they completed the path a month ago alongside a control panel and a wood-chip panel.

"We have reviewed it and had inspections, and the council is happy with the performance," he said.

Macedon Ranges council director of assets and operations, Shane Walden told RMIT the trial was going well and that residents would not see or smell any difference in the concrete.

"This not only helps improve the knowledge level of our contractors and our staff, but it also has lots of other benefits and benefits that are important to our community," Mr Walden said.

"This includes helping the environment, acting sustainably and, most importantly, reducing waste to landfill and having a circular economy."

Dr Roychand said they were in the process of collaborating with BildGroup for level-crossing projects throughout Victoria and had potential plans for other states.

"We had interest even from a major coffee chain, they approached us for collaboration, and are based in the US but has operations throughout the world," he said.