Researchers from RMIT University in Australia have found an innovative solution to two pressing global issues: the excessive consumption of sand in concrete production and the disposal of coffee grounds, which contribute to environmental challenges. Their study, published in the September issue of the Journal of Cleaner Production, reveals that coffee grounds can be utilized as a sustainable substitute for sand in concrete, resulting in a significantly stronger chemical bond.
Every year, humans produce a staggering 4.4 billion tons of concrete, consuming approximately 8 billion tons of sand, out of the 40-50 billion tons used globally annually. This massive sand consumption has led to acute shortages, driving up costs and causing environmental concerns. Simultaneously, the world generates about 10 billion kilograms of used coffee grounds annually, most of which ends up in landfills, contributing to greenhouse gas emissions, including methane and carbon dioxide.
Lead author of the study, Dr. Rajeev Roychand of RMIT’s School of Engineering, emphasized the significance of their findings, stating, “The disposal of organic waste poses an environmental challenge as it emits large amounts of greenhouse gases, which contribute to climate change.” He noted that in Australia alone, 75 million kilograms of used coffee grounds are discarded each year.
The key breakthrough lies in the process of pyrolyzing the coffee grounds at temperatures of 350 degrees Celsius. By doing so and substituting them for sand in various percentages (5%, 10%, 15%, and 20%) in standard concrete mixtures, the research team achieved remarkable results. The optimal temperature was found to be 350 degrees Celsius, leading to a “29.3 percent enhancement in the compressive strength of the composite concrete blended with coffee biochar.”
Dr. Roychand highlighted the dual benefits of this discovery, stating, “In addition to reducing emissions and making a stronger concrete, we’re reducing the impact of continuous mining of natural resources like sand.”
Co-author Dr. Shannon Kilmartin-Lynch, a Vice-Chancellor’s Indigenous Postdoctoral Research Fellow at RMIT, emphasized the potential of this research to address the issue of organic waste disposal. She stated, “The concrete industry has the potential to contribute significantly to increasing the recycling of organic waste such as used coffee. Our research is in the early stages, but these exciting findings offer an innovative way to greatly reduce the amount of organic waste that goes to landfill,” where its decomposition would otherwise generate significant amounts of methane, a greenhouse gas 21 times more potent than carbon dioxide.
This breakthrough not only offers a promising avenue for more sustainable construction practices but also highlights the potential for creative solutions to address environmental challenges by repurposing waste materials.
