Researchers in Australia have discovered that 30% stronger concrete can be produced by processing and adding coffee grounds to the cement mix.
Every year the world produces a staggering 10 billion kilograms of coffee grounds, most of which end up in landfills.
“The disposal of organic waste poses an environmental challenge because it emits large amounts of greenhouse gases, including methane and carbon dioxide, which contribute to climate change,” explains engineer Rajiv Roychand, from RMIT University.
As the global construction market booms, there is also a growing demand for resource-intensive concrete, causing another set of environmental challenges.
“The continued extraction of natural sand around the world – typically taken from river beds and banks – to meet the rapidly increasing demands of the construction industry is having According to Jie Li, an engineer at RMIT, this has a massive influence on the environment. Due to the resource scarcity and the effects sand extraction has on the ecosystem, sustaining a sustainable supply of sand presents serious, long-term issues.
Organic products such as coffee grounds cannot be added directly to concrete because they leach chemicals that weaken the strength of building materials. So, using lower power levels, the team heated coffee grounds to more than 350 degrees Celsius (about 660 degrees Fahrenheit) while depriving them of oxygen.
This process, called pyrolysis, breaks down organic molecules, resulting in a porous, carbon-rich char called biochar, which can form bonds with the cement matrix and thus embed itself in it.
Roychand and his colleagues also attempted to pyrolyze coffee grounds at 500 degrees Celsius, but the resulting biochar particles were not as strong.
The researchers caution that they still need to evaluate the long-term durability of their cement product. They are now testing how hybrid coffee cements perform under freeze/thaw cycles, water absorption, and other stresses.
The team is also working on producing biochar from other organic waste sources, including wood, food waste, and agricultural waste.
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