Australia faces a dual environmental challenge: managing organic waste and reducing the environmental impact of the construction sector. One of the most common types of organic waste is used coffee grounds, which often end up in garbage dumps, releasing methane—a gas that traps heat and contributes significantly to climate change. To tackle both waste and pollution, researchers looked into whether this everyday waste could be reused to make concrete stronger and more environmentally friendly.
Dr. Rajeev Roychand, and Professor Shannon Kilmartin from RMIT University carried out a detailed study, recently published in the scientific journal Journal of Cleaner Production. The team explored whether coffee grounds, after being heated and turned into a charcoal-like substance—known in science as biochar, a porous material made by burning organic matter in the absence of oxygen—could replace some of the sand that is typically mixed into concrete.
In their experiments, the researchers found that using untreated coffee grounds directly in concrete didn’t work well. The natural compounds in the grounds interfered with how the cement hardens, making the concrete weaker. However, when the coffee grounds were heated in an oxygen-free environment—a process known as pyrolysis, which breaks down organic material into stable carbon forms—the result was very different. Adding this treated coffee material into concrete in the right amount made it noticeably stronger.
This improvement in strength comes from a few key reasons. First, the treated coffee material has tiny holes that can hold onto water. This helps the cement harden more effectively from the inside, even after the outer surface has dried. In addition, the cement mixture can get into the pores of the treated coffee particles, creating a better connection between materials and helping the concrete hold together more firmly. Because of these effects, the coffee material doesn’t just fill space—it actually helps the concrete become stronger.
“The concrete with the coffee-based material treated at the lower temperature got stronger as we added more of it—up to a certain point,” explained Dr. Roychand. “Beyond that point, the benefits started to level off, but the concrete still performed well overall.” This means there is a sweet spot for how much of the coffee material should be used to get the best results.
Environmentally and economically, the outcome is encouraging. Australia throws away a large amount of used coffee grounds every year. According to the study, if this waste were instead turned into treated coffee material, it could produce enough useful material to replace a significant portion of the sand used in concrete construction. This would help cut down on waste going to landfills and reduce the need to mine sand, which often damages natural environments.
The team pointed out that this strategy fits well with the idea of using waste to create new products—a concept often called a circular economy, which refers to reusing and recycling materials continuously rather than discarding them. It can benefit the environment, boost the economy, and even create jobs. By turning waste into something valuable, the need for fresh raw materials is reduced, and new business opportunities can arise in recycling and green construction.
“Adding coffee-based material doesn’t just make concrete better; it also gives us a practical way to manage waste,” Professor Kilmartin said. They believe more studies should be done to see how this material holds up over time, especially in different weather conditions and building types.
Journal Reference
Roychand R., Kilmartin-Lynch S., Saberian M., Li J., Zhang G., Li C.Q. “Transforming spent coffee grounds into a valuable resource for the enhancement of concrete strength.” Journal of Cleaner Production, 2023. DOI: https://doi.org/10.1016/j.jclepro.2023.138205
About the Authors
Dr. Rajeev Roychand is a research fellow at RMIT University’s School of Engineering in Melbourne, Australia, where he specializes in sustainable construction materials. With a background in civil engineering and a deep interest in environmental innovation, his work focuses on recycling industrial and organic waste into high-performance building materials. Dr. Roychand has led several projects exploring the use of alternative materials—such as fly ash, waste plastics, and biochar—to improve concrete sustainability and performance. He is passionate about reducing the carbon footprint of the construction industry by developing practical, scalable solutions. Known for his hands-on approach and industry collaborations, Dr. Roychand aims to bridge the gap between academic research and real-world applications in infrastructure.
Professor Shannon Kilmartin-Lynch is an Indigenous pre-doctoral research fellow at RMIT University and a rising leader in sustainable materials research. Her work combines environmental science with community-focused engineering solutions. With a commitment to advancing Indigenous representation in STEM, she explores how waste materials—such as spent coffee grounds and personal protective equipment—can be transformed into valuable resources for construction. Professor Kilmartin-Lynch brings a strong focus on circular economy practices and environmental equity to her research, aiming to reduce landfill waste and promote green innovation. Her work not only advances sustainable technologies but also supports inclusive and culturally aware scientific engagement.
