Leoben researchers unlock new recycling solution from used aluminium coffee-capsules

Pop in the capsule, press a button, and your coffee's ready, a quick, clean, and convenient process. But behind that ease lies an environmental challenge. In Austria, even with a dedicated collection system for used coffee capsules, only about 30 per cent make it to recycling.

Because a high amount of leftover coffee grounds is compared to the aluminium packaging, this complicates the melting process in smelters and makes recycling both technically and economically difficult. To tackle this, a team at the Chair of Nonferrous Metallurgy at Montanuniversität Leoben (Technical University of Leoben), in collaboration with industry partners, is working on an innovative treatment process.

Their goal is to recover aluminium from used capsules and turn it into a new material, helping close the loop in line with the university's vision for circular engineering. In collaboration with industry partners, the team is developing a new treatment process designed to turn used aluminium coffee capsules into brand-new ones, giving your daily brew a second life and moving one step closer to true circular recycling.

"The aluminium from such capsules is very valuable and should be preserved in the sense of a circular economy. Like Nespresso capsules, which consist of around 0.5 to 1 gram of packaging material, with aluminium being the main component, and contain around 6 grams of coffee. The challenge is to separate these components and ensure efficient recycling," said Ass.-Prof. Dr. Eva Gerold, researcher at the Chair of Nonferrous Metallurgy at the University of Leoben.

Also Read: Trump’s conscious move to exempt aluminium scrap from tariff is reflecting on booming recycling market

Coffee capsule alloys aren't one-size-fits-all they vary from brand to brand. And when used capsules aren't correctly sorted or get mixed, recreating a specific alloy becomes a real challenge. In such cases, the recycled material typically ends up as cast alloys, often used in engine blocks. But with the rise of e-mobility and the decline in demand for traditional combustion engines, that outlet is shrinking fast.

That's why researchers are stepping in to develop smarter alloys and flexible recycling processes, ones that can handle a mix of alloying elements and still deliver high-quality results. The goal is to open up new, sustainable pathways for reused aluminium. To test and refine the new recycling process, an industrial partner supplies the researchers with capsule materials prepared in various ways, differing in both the level of comminution and the proportion of organic residues.

"In a first step, the used coffee capsules are shredded, and the coffee they contain is separated. The oils and varnishes on the capsules are then removed. They contain organic components that would contaminate the melt. This conversion process works thermally in the absence of oxygen - with the aid of nitrogen, for example. The resulting gases have a high calorific value and are used to heat the melting furnace in an energy-efficient manner," explained the researcher. To minimise oxidation due to the high surface volume of the capsules, they are compacted before melting.

"The primary materials are first carbonised in so-called two-chamber furnaces and pushed into the melting bath to produce metallic aluminium. Salt treatment also helps to remove impurities and improve the composition of the melt," added Gerold.

In the next phase of the project, the team produces small aluminium ingots, which are then rolled into ultra-thin foils just 0.1 mm thick using the chair's mini rolling mill. This foil represents the target material for creating new coffee capsules. Looking ahead, an industry partner will take these foils and industrially shape them back into coffee capsules, paving the way for a truly closed-loop recycling system.

"But that's not the only possibility," one researcher pointed out, saying, "These recycled capsules don't have to become capsules again, they could just as easily be turned into a drinks can or even a new laptop, depending on what's needed and the alloy composition."

Also Read: Capral, Rio & Sims team up for closed-loop aluminium recycling

Note: To feature your brand and share insights, contribute an article or interview in our forthcoming e-magazine " Sustainability & Recycling: Aluminium's Dual Commitment.”