Charred coffee grounds could make concrete up to 30 percent stronger, scientists in Australia have discovered.
Your clever recipe could solve multiple problems at once.
Each year, the world produces about 10 billion kilograms (22 billion pounds) of coffee waste, most of which ends up in landfills.
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“Organic waste disposal poses an environmental challenge as it emits large amounts of greenhouse gases, including methane and carbon dioxide, which contribute to climate change,” explained RMIT University engineer Rajeev Roychand when the research was published in 2023.
With a booming construction market globally, there is also increasing demand for resource-intensive concrete, creating another set of environmental challenges.
Watch the video below for a summary of the study:
“The current extraction of natural sand around the world (usually extracted from river beds and banks) to meet the increasing demands of the construction industry has a major impact on the environment,” said RMIT engineer Jie Li.
“There are critical and long-standing challenges to maintaining a sustainable supply of sand due to the finite nature of the resources and the environmental impacts of sand mining. With a circular economy approach, we could keep organic waste out of landfills and also better preserve our natural resources like sand.”
Organic products like coffee grounds cannot be added directly to concrete because they leach chemicals that weaken the strength of the building material.
Then, using low levels of energy, the team heated the coffee waste to more than 350°C (about 660°F) while depriving it of oxygen.
This process is called pyrolization. It breaks down organic molecules, resulting in a carbon-rich porous carbon called biochar that can form bonds and therefore be incorporated into the cement matrix.
Roychand and his colleagues also tried pyrolyzing coffee grounds at 500°C, but the resulting biochar particles were not as strong.
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The researchers cautioned that they still need to evaluate the long-term durability of their cement product.
They are now working to test how the coffee-cement hybrid behaves under freeze/thaw cycles, water absorption, abrasions, and many more stressors.
The team is also working on creating biochar from other organic waste sources, such as wood, food and agriculture.
Scanning electron microscope images of the surface structures of pyrolyzed ground coffee. (Roychand et al, Cleaner Production Magazine2023)
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“Our research is in the early stages, but these exciting findings offer an innovative way to greatly reduce the amount of organic waste ending up in landfill,” said RMIT engineer Shannon Kilmartin-Lynch.
“The inspiration for my research, from an indigenous perspective, involves caring for the country, ensuring there is a sustainable life cycle for all materials and preventing them from going to landfills to minimize the impact on the environment.”
His research was published in the Cleaner Production Magazine.
A previous version of this article was published in September 2023.