A potential use of coffee may not only be in starting the day, but also in its leftovers. These can play a revolutionary role in the construction industry.
A recent study published in the Journal of Cleaner Production has shown that spent coffee grounds (SCG), when properly treated, can significantly improve the properties of concrete, an essential material in construction.
From waste to resource: uses of spent coffee grounds
The disposal of organic waste, such as spent coffee grounds, in landfills significantly contributes to the emission of greenhouse gases, especially methane, with a climate impact 21 times greater than carbon dioxide.
Facing this challenge, a new method for recycling this waste has been discovered, using it as a partial replacement for sand in concrete.
What is pyrolysis?
The key process is pyrolysis, a technique that involves heating the coffee grounds in an oxygen-free environment at temperatures of 350 °C or higher. This process converts the grounds into biochar, a porous and carbon-rich material.
The study revealed that biochar obtained at 350 °C (referred to as 350CBC) can replace up to 15% of the sand in concrete mixes, with a 29.3% increase in the compressive strength of the resulting structures compared to conventional concrete.
Factors of success of 350CBC
The success of 350CBC is attributed to three factors:
- Enhanced adhesion: The biochar interacts effectively with the cement paste, creating a stronger microstructure.
- Structural reinforcement: The pores of the biochar allow cement to penetrate and strengthen the mixture.
- Internal curing: The water stored in the biochar’s pores is gradually released, improving the curing process.
In contrast, when coffee grounds are subjected to higher temperatures (500 °C), the resulting biochar has a more fragile structure that reduces the concrete’s strength.
A sustainable advancement
The research not only paves the way for a sustainable method to manage coffee waste but also offers environmental and economic benefits.
Using coffee grounds to partially replace sand in concrete could reduce its extraction and lower carbon emissions associated with the transportation and production of traditional materials.
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