How used coffee grounds make concrete stronger

By Jim Leffman via SWNS

Concrete has been made a third stronger by adding used coffee grounds.

As well as making the end result stronger, it cuts down on the mining of sand and also used coffee ending up in landfill.

The grounds are turned into biochar using a low-energy process without oxygen at 350 degrees celsius before partly replacing sand in concrete.

Lead author Dr. Rajeev Roychand from RMIT University in Melbourne, Australia, said:
“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."

Globally, 10 billion kilograms of spent coffee is generated annually.

Biochar looks like charcoal and is produced using pyrolysation, where organic matter is heated at high temperature without oxygen.

It can be used to enhance soil, as an additive in cattle feed, in water filtration and in industry.

The study, published in the Journal of Cleaner Production, is the first to prove that waste coffee grounds can be used to improve concrete.

Roychand added: “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 pyrolysed forms of different organic wastes.”

The latest discovery shows that the construction industry can support the recycling of waste.

Joint lead author, Dr. Shannon Kilmartin-Lynch, said construction industries around the world could play a role in transforming this waste into a valuable resource.

“Inspiration for my research, is ensuring there’s a sustainable life cycle for all materials and avoiding things going into landfill to minimise the impact on the environment," she said.

“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.”

Corresponding author and research team leader Professor Jie Li said the coffee biochar can replace a portion of the sand that was used to make concrete.

He said: “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."

He said that 50 billion tonnes of natural sand are used in construction projects globally every year.

He added: “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.”

Co-researcher Dr. Mohammad Saberian said: “Our research team has gained extensive experience in developing highly optimised biochars from different organic wastes, including wood biochar, food-waste biochar, agricultural waste biochar, and municipal solid-waste biochar, for concrete applications."