Using spent coffee grounds to replace some of the sand in concrete makes the material stronger and could reduce greenhouse gas emissions from coffee grounds in landfill
Concrete can be made 29 per cent stronger by incorporating recycled coffee grounds.
An estimated 18 million tonnes of spent coffee grounds are produced globally each year, with most ending up in landfill. Their decomposition in landfill releases methane, which has a global warming effect 21 times stronger than that of carbon dioxide.
Rajeev Roychand at RMIT University in Melbourne, Australia, and his colleagues wondered if they could keep coffee grounds out of landfill by finding new uses for them in building materials.
They collected used coffee grounds from several local cafes and investigated whether they could be used to replace some of the sand that is typically incorporated into concrete as filler.
In an unmodified state, the spent coffee grounds were found to weaken concrete when they replaced the sand component.
However, they became more useful when the researchers heated them in a 350°C furnace for 2 hours in the absence of oxygen to create a charcoal-like substance called biochar.