Coffee Biochar Could Replace Sand in Concrete

Australian engineers have discovered a way to make stronger concrete using roasted, used coffee grounds, giving the drink additive a “double-shot” and reducing waste going to landfills.

Coffee Biochar Could Replace Sand in Concrete

Image Credit: RMIT University

According to lead author Dr. Rajeev Roychand of RMIT University, the group developed a technique to make concrete 30 percent stronger by converting waste coffee grounds into biochar using a low-energy, oxygen-free process at 350 °C.

The disposal of organic waste poses an environmental challenge as it emits large amounts of greenhouse gases including methane and carbon dioxide, which contribute to climate change.

Dr. Rajeev Roychand, Postdoctoral Research Fellow, RMIT University

Australia generates 75 million kg of ground coffee waste each year, the majority of which ends up in landfills. Every year, 10 billion kg of spent coffee is produced worldwide.

The RMIT engineers’ study, published in the Journal of Cleaner Production, is the first to demonstrate that used coffee grounds can be used to improve concrete.

The inspiration for our work was to find an innovative way of using the large amounts of coffee waste in construction projects rather than going to landfills—to give coffee a ‘double shot’ at life. Several councils that are battling with the disposal of organic waste have shown interest in our work. They have already engaged us for their upcoming infrastructure projects incorporating pyrolyzed forms of different organic wastes.

Dr. Rajeev Roychand, Postdoctoral Research Fellow, RMIT University

Pyrolysis is the process of heating organic waste in the absence of oxygen.

The Construction Industry Can Support the Recycling of Waste

Joint lead author Dr. Shannon Kilmartin-Lynch, a Vice-Chancellor’s Indigenous Postdoctoral Research Fellow at RMIT believes construction industries around the world can help turn this waste into a valuable resource.

Dr. Kilmartin-Lynch comments, "Inspiration for my research, from an Indigenous perspective, involves Caring for Country, ensuring there’s a sustainable life cycle for all materials, and avoiding things going into landfill to minimize the impact on the environment. 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."

Preserving a Precious Natural Resource

According to the corresponding author and head of the research team, Professor Jie Li, coffee biochar can substitute for some of the sand used to make concrete.

The ongoing extraction of natural sand around the world—typically taken from river beds and banks—to meet the rapidly growing demands of the construction industry has a big impact on the environment,” Li notes.

Every year, 50 billion tons of natural sand are used in construction projects around the world.

There are critical and long-lasting challenges in maintaining a sustainable supply of sand due to the finite nature of resources and the environmental impacts of sand mining. With a circular-economy approach, we could keep organic waste out of landfill and also better preserve our natural resources like sand.

Jie Li, Study Corresponding Author and Professor, RMIT University

Dr. Mohammad Saberian, a Co-Researcher, stated that the construction industry needed to investigate alternative raw materials to ensure its sustainability.

Our research team has gained extensive experience in developing highly optimized biochars from different organic wastes, including wood biochar, food-waste biochar, agricultural waste biochar, and municipal solid-waste biochar, for concrete applications,” Saberian added.

What are the Next Steps?

The investigators intend to create practical implementation strategies and conduct field trials. The team is eager to collaborate with various industries to advance their research.

Support for the Research

The research was supported by ARUP Australia Pty Ltd, Earth Systems Pty Ltd, and RMIT University, including the Strategic Capability Deployment Fund, Rheology and Materials Characterisation Laboratory, the X-Ray Facility, and the Microscopy and Microanalysis Facility.

The authors also acknowledge Talwali Coffee Roasters, an Indigenous-owned coffee supplier, for supplying used ground coffee for the study.

Journal Reference:

Roychand, R., et al. (2023). Transforming spent coffee grounds into a valuable resource for the enhancement of concrete strength. Journal of Cleaner Production. doi.org/10.1016/j.jclepro.2023.138205.

Source: https://www.rmit.edu.au

Coffee offers performance boost for concrete | RMIT University

Video Credit: RMIT University

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