The people of Melbourne are known for their addiction to coffee, which is sold here literally at every turn. However, this generally harmless phenomenon has a negative side - a huge amount of coffee waste. On average, one city cafe throws out up to 150 kg of grounds per week.
A professor at the local Swinburne University - Arul Arulrayah once asked himself the question: why not use coffee waste as a component of the road surface? The team under his leadership collected coffee grounds from all nearby establishments. After a thorough five-day drying in a special oven at a temperature of 50 ºC, the coffee waste was filtered, lumps were removed, and then mixed with steel production waste - slag in a ratio of 7: 3.
Next, a liquid alkaline solution was added to the mixture, which bound its components. As a result, strong cylindrical blocks have been produced that can be used as soil material under the road surface.
According to scientists, the available coffee waste in Melbourne would be more than enough to build 5 km of roads annually.