The reason: the ratio of 6 grams of coffee grounds to around 1 gram of aluminium makes it difficult to efficiently recover the valuable shell in the smelters. This is a real challenge for the circular economy. But it is also a great opportunity.
Aluminium is far too valuable for waste
A research project at the Chair of Non-Ferrous Metallurgy at the University of Leoben aims to tackle precisely this problem. Together with industrial partners, a process is being developed that makes it possible to produce new coffee capsules from used ones. "The aluminium is of high quality and should definitely be preserved in the interests of a sustainable circular economy," emphasises project manager Assistant Professor Dr Eva Gerold. But that is easier said than done. The different alloys used by manufacturers make recycling tricky. And: "Once it's in aluminium, it stays in aluminium" - in other words, alloying elements such as silicon, zinc or iron must be taken into account during recycling.
From shredding to wafer-thin foil
How does the process work? First, the capsules are shredded, the coffee grounds are separated and then the varnish and oils are removed. This is done thermally in the absence of oxygen - the resulting gases serve as an energy source for the melting furnace. In this way, waste is utilised twice. Before being melted down, the capsules are compacted to minimise oxidation. Metallic aluminium is then produced in special two-chamber furnaces, which is additionally purified with salt treatments. The researchers use this material to cast small ingots, which are rolled into wafer-thin foils just 0.1 millimetres thick on a test facility - exactly the starting material for new capsules.
More than just coffee
The goal is clear: closed-loop recycling, in which a new capsule is created from an old one. But the potential goes far beyond this. Depending on the alloy, the aluminium obtained can also be used in drinks cans or even in laptop components. In this way, what appears to be a waste product becomes a versatile raw material for the future.
#schongenial, when your morning coffee is not only a pleasure, but also a piece of the future.
