Scientists Utilize Ground Coffee Waste to Create Biochar, Replacing River Sand in Concrete and Building Footpaths in Gisborne.
Researchers at RMIT University, in collaboration with members of the Macedon Ranges Shire Council in Australia, are experimenting with the world’s first footpath made from coffee concrete in Gisborne, marking a significant advancement in constructing environmentally friendly infrastructure, as reported by Interesting Engineering on May 24.
Completed coffee concrete footpath in Gisborne, Australia. (Photo: Chris Matthews/Macedon Ranges Shire Council).
Australia generates 75 million kilograms of ground coffee waste annually, most of which ends up in landfills. Along with other untreated organic materials, landfills contribute to 3% of global greenhouse gas emissions. Researcher Dr. Rajeev Roychand and his colleagues at RMIT University aim to leverage coffee waste instead of allowing this valuable resource to decompose in landfills.
Organic waste cannot be directly mixed into concrete as it decomposes over time, weakening the structure. Therefore, the research team considered biochar—a solid carbon material produced by the incomplete combustion of organic waste. By heating ground coffee waste to 350 degrees Celsius in an oxygen-free environment, they created coffee biochar to prolong the lifespan of the waste, making it suitable as an ingredient in concrete.
Biochar Replaces River Sand in Concrete Mixes. “Sand is becoming increasingly scarce over time, and this waste can replace up to 15% of the sand in concrete,” Roychand stated. The 75 million kilograms of coffee waste, which is significantly denser, can replace over 655 million kilograms of sand in concrete. Globally, about 10 billion kilograms of ground coffee waste is produced each year, which could replace approximately 90 billion kilograms of river sand.
“We will allow people to walk over the concrete containing these products, and RMIT will return to check how well it holds up,” said Shane Walden, director at the Macedon Ranges Shire Council.
“Our research even presents the potential to reduce cement content. Since we achieve a 30% increase in strength with coffee concrete, we could potentially reduce the necessary cement content by up to 10%,” Roychand noted. The newly constructed footpath in Australia does not use less cement; however, the team at RMIT is working diligently to investigate this direction.
