Engineers in Australia claim they can make concrete nearly 30% stronger by adding processed coffee grounds.
Researchers at RMIT University have developed a method to increase concrete strength by about 30% using recycled coffee waste. They convert used coffee grounds into biochar by heating the waste to about 350 °C, then replace part of the sand in the concrete mix with this biochar.
Their tests showed that substituting 15% of the sand normally used in concrete with coffee biochar boosted the material’s strength by 29.3%.
Dr. Shannon Kilmartin-Lynch, co-lead of the study, said the idea came from a desire to reduce coffee waste. The team is now working with local authorities on future infrastructure projects such as building footpaths and sidewalks.
They argue the technique benefits the environment by reducing the amount of coffee waste sent to landfill and cutting the demand for natural sand in construction.
According to Australia’s National Food Waste Strategy Feasibility Study, food waste accounts for around 3% of the country’s annual greenhouse gas emissions. Australia produces about 75,000 tons of coffee waste each year. The researchers estimate that if all this coffee waste were converted to biochar annually, it would yield around 22,500 tons of material.