Researchers at Swinburne University of Technology in Melbourne, Australia believe they could have found a use for the many millions of tonnes of coffee grounds that normally goes to waste every year. They think it could be used in roadbuilding.
In a paper in Construction and Building Materials, researcher Arul Arulrajah and colleagues noted that grinding and brewing coffee generates spent coffee grounds, which they describe as “an insoluble waste material that is rich in organic content.” They dried ground coffee collected from a local coffee shop and dried it in an oven. Next they mixed the coffee grounds with a waste product from steel manufacturing called slag and added an alkaline solution to bind it together. This material was then compressed into blocks which, they claim, is strong enough to use as the foundation for roadbuilding.
“The objective of the study was to evaluate the possibility of combining a highly organic waste with industrial waste into a sustainable subgrade construction material by a geo-polymerization process,” they said. “A geopolymeric material was synthesized using coffee grounds as the base material with a controlled ratio of industrial waste. A mixture of sodium silicate solution and sodium hydroxide solution was used as the alkaline liquid activator. Strength development of these geopolymers was assessed using the unconfined compressive strength test. The research findings have the potential to transform the construction industry in the sustainable usage of waste by-products in future road subgrades,” they concluded.
