A team of engineers at Australia’s RMIT University has developed a process to turn spent coffee grounds into biochar, which can be used to make concrete that’s nearly 30% stronger. The process can help reduce the amount of coffee waste that goes to landfill – which one figure estimates to be six million tons annually – and cut the methane emissions produced during its decomposition.

To transform used coffee into concrete, the scientists convert the spent grounds into biochar – a charcoal-like lightweight residue – via a roasting method not dissimilar to how beans are roasted to extract flavour. The process is called pyrolysis, and involves heating the grounds to 350°C in the absence of oxygen, which prevents carbon dioxide from being produced and adding to greenhouse gas emissions. The engineers say the process is more energy-efficient than typical pyrolysis techniques as it requires lower temperatures than usual. Normally, pyrolysis can be a high-energy procedure as “you need to raise temperatures to somewhere between 700°C to 900°C”, according to study co-lead Dr Shannon Kilmartin-Lynch.

This process helps replace 15% of the sand typically used in concrete manufacturing with coffee biochar, which, in turn, enhances the strength of the concrete by 29.3%. “Structurally, the coffee biochar itself is finer than a sand… but it’s also a porous material, so it allows the cement to bind within the porous structure of the biochar itself,” explained Kilmartin-Lynch.

To read the full story, visit https://www.greenqueen.com.hk/scientists-recycled-spent-coffee-grounds-waste-stronger-concrete-landfill/.
Image: RMIT University