AustraliaScientists use ground coffee waste to make biochar, replace river sand in concrete and build walking paths in Gisborne.
Researchers at RMIT University and members of the Macedon Ranges Shire Council, Australia, collaborated to trial the world’s first walkway made from coffee concrete in Gisborne, an important step forward in building environmentally friendly projects, Interesting Engineering reported on May 24.
Australia generates 75 million kg of ground coffee waste annually, most of which ends up in landfills. Along with other untreated organic materials, landfills contribute 3% of the world’s greenhouse gas emissions. Postdoctoral researcher Rajeev Roychand and colleagues at RMIT University want to make use of coffee waste instead of letting this valuable resource decompose in landfills.
Organic waste cannot be added directly to concrete because it will decompose over time and weaken the structure. Therefore, the research team thought of biochar – a solid mass of carbon created by incomplete combustion of organic waste. By heating ground coffee waste to 350 degrees Celsius in the absence of oxygen, they created coffee biochar to increase the longevity of the waste, making it suitable as an ingredient in concrete.
Biochar helps replace river sand in concrete mixes. “Sand becomes increasingly scarce over time and this waste can replace up to 15% of sand in concrete,” Roychand said. 75 million kg of coffee waste, which is much denser, could replace more than 655 million kg of sand in concrete. On a global scale, about 10 billion kg of ground coffee waste is generated annually, which can replace about 90 billion kg of river sand.
“We will have people walk through the concrete containing these products and RMIT will come back and check how they are holding up,” said Shane Walden, director at Macedon Ranges Shire Council.
“Our research even offers the potential to reduce cement content. Since we achieved a strength increase of 30% with coffee concrete, it is possible to reduce the required cement content by up to 10%,” Roychand said. Newly built walkways in Australia do not use less cement, but a team of experts at RMIT is working hard in this direction.
Thu Thao (Theo Interesting Engineering)