Roasted used coffee grounds are to be given a double shot at life after engineers in Australia found a way to use them to make concrete stronger, while lowering greenhouse gases.
The team developed a technique to make concrete 30 per cent stronger by turning waste coffee grounds into biochar, using a low-energy process without oxygen at 350°C, said lead author Dr Rajeev Roychand, from the Royal Melbourne Institute of Technology 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,” said Dr Roychand, from RMIT's school of engineering.
Globally, 10 billion kilograms of spent coffee are generated annually and most of it goes to landfills.
The study by RMIT engineers is the first to prove that waste coffee grounds can be used to improve concrete, with the findings published in the Journal of Cleaner Production.
“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,” said Dr Roychand.
“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.”
Pyrolysis involves heating organic waste in the absence of oxygen.
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Construction industries around the world could play a role in turning this waste into a valuable resource, joint lead author, said Dr Shannon Kilmartin-Lynch, a vice chancellor’s indigenous postdoctoral research fellow at RMIT.
“Inspiration for my research, from an Indigenous perspective, involves Caring for Country, ensuring there’s a sustainable life cycle for all materials and avoiding things going into landfill to minimise the impact on the environment,” said Dr Kilmartin-Lynch.
“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.”
The coffee biochar can replace a portion of the sand that was used to make concrete, corresponding author and research team leader Prof Jie Li 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,” Prof Li said.
Fifty billion tonnes of natural sand are used in construction projects globally every year.
“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,” Prof Li said.
“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 the construction industry needed to explore alternative raw materials to ensure its sustainability.
“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,” Dr Saberian said.
The researchers plan to develop practical strategies and work towards field trials.
They are keen to collaborate with various industries to develop their research.
