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‘Pyrolyzing them at 350 degrees Celsius for a short duration is all it takes.’
Concrete production consumes a staggering 8 billion tons of sand annually, contributing to acute shortages of this essential building commodity. However, researchers from RMIT University in Australia have made an exciting discovery that could alleviate this problem. They have found that coffee grounds can be used as a silica substitute in the concrete production process, resulting in a significantly stronger chemical bond than sand alone.
The disposal of organic waste, such as coffee grounds, presents environmental challenges as it emits large amounts of greenhouse gases, including methane and carbon dioxide. Dr. Rajeev Roychand, the lead author of the study from RMIT’s School of Engineering, highlights that Australia alone produces 75 million kilograms of used coffee grounds each year, most of which end up in landfills.
The research team at RMIT experimented with pyrolyzing the coffee grounds at temperatures of 350 and 500 degrees C, making them more compatible with the other concrete materials. They then substituted the treated coffee grounds for sand in varying percentages (5, 10, 15, and 20 by volume) in standard concrete mixtures.
The team’s study, published in the September issue of the Journal of Cleaner Production, reveals that the perfect temperature for pyrolyzing the coffee grounds is 350 degrees C. At this temperature, the composite concrete blended with coffee biochar exhibited a 29.3 percent enhancement in compressive strength. This not only reduces emissions but also reduces the need for continuous mining of natural resources like sand.
Dr. Shannon Kilmartin-Lynch, a Vice-Chancellor’s Indigenous Postdoctoral Research Fellow at RMIT and co-author of the study, emphasizes the potential of the concrete industry to contribute significantly to the recycling of organic waste like used coffee. These findings offer an innovative way to greatly reduce the amount of organic waste that goes to landfills, where its decomposition generates large amounts of methane, a greenhouse gas 21 times more potent than carbon dioxide.
This breakthrough in utilizing coffee grounds in concrete production not only addresses the sand shortage but also provides an environmentally friendly solution for organic waste disposal. With further research and development, this innovation could have a significant impact on the construction industry’s sustainability efforts.