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Wednesday, August 23, 2023

used Coffee grounds make strong Concrete !!

As Civilization progressed, humanity has been worried about land for living and the process of construction.  There are landfills and the decomposition of organic waste in such landfills produces methane gas, which reportedly is 21 times worse than CO2 in its global warming potential.  Spent Coffee grounds (SCG) are one type of organic waste that forms significant proportion of organic waste in landfills.   Sounds not so familiar to us !! 

Coffee is one of the most widely consumed drinks in the world, with two billion cups drunk worldwide every day.  South Indian coffee (a.k.a filter coffee) is a milk coffee (perfect example of South Indians' affinity for dairy products) – a great mixture of decoction and milk added with sugar,  primarily from coffee beans and chicory.  In recent past, on every highway in Tamilnadu, shops calling themselves - original Kumbakonam filter coffee shops have mushroomed. In South Indian culture, the visitor to a House is welcomed and offered a tumbler of coffee.  It is an energizer !

All coffee comes from the coffee tree (genus Coffea). The tree’s cherries are picked and processed to gain access to the tiny seeds they contain, which are called green coffee beans. These green coffee beans are then roasted before being ready for consumption and are called whole coffee beans.  Before being brewed however, whole coffee beans are ground into smaller particles to extract as much flavour as possible.  This is easily  accomplished using a variety of tools including electric coffee grinders, blenders, mortar and pestles, or food processors – there were handwound grinders in early days. After being ground in one of these devices, whole coffee beans are referred to as ‘ground coffee’.

Used coffee grounds is the result of brewing coffee, and are the final product after preparation of coffee. Despite having several highly-desirable chemical components, used coffee grounds are generally regarded as waste, and they are usually thrown away or composted.  On an average, 1 tonne of green coffee produces approximately 650 kg of spent coffee grounds,  and over 15 million tonnes of spent coffee grounds are generated annually.   

Today read this interesting piece in Guardian UK about an  idea that fittingly arose over a cup of coffee, researchers have devised a technique to recycle used coffee grounds to make stronger concrete.  Engineers at RMIT University say they have developed a way to make concrete nearly 30% stronger by incorporating processed coffee grounds into the material.  The researchers have converted waste coffee grounds into biochar, a lightweight residue similar to charcoal, and used that biochar to replace a portion of the sand required to make concrete. 

The idea arose from a desire to minimise coffee waste within the workplace, said study co-lead Dr Shannon Kilmartin-Lynch, a vice-chancellor’s Indigenous postdoctoral research fellow at RMIT. “There was a lot of ground coffee and coffee pods being discarded,” he said. “[We wanted] to see if we could transform those spent coffee grounds into a more valuable sort of material.” The researchers are now collaborating with local councils on future infrastructure projects such as the construction of walkways and pavements.

The technique could be environmentally beneficial if it can reduce the amount of coffee waste going to landfill, as well as the demand for natural sand used in the construction industry, the engineers say.  Australia produces an estimated 75,000 tonnes of coffee waste per year. The process, called pyrolysis, involves heating the coffee waste to about 350C. The team says their technique is more energy efficient because it requires lower than usual temperatures.  By replacing 15% of the sand typically used in concrete with coffee biochar, the researchers found that the addition enhanced strength by 29.3%.

“It definitely still is in its initial phase – there are further tests to be done on the durability and things like that.” If all waste coffee grounds produced in Australia each year were converted into biochar, it would amount to roughly 22,500 tonnes, the researchers estimate.  The research was published in the journal Journal of Cleaner Production.

Interesting !
With regards – S. Sampathkumar

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