The mountains of discarded clothing growing in Europe’s landfills tell a stark story: the way we produce and dispose of textiles is fundamentally unsustainable. Every year, millions of tonnes of garments, often made from complex fibre blends, are discarded with no viable route to recycling. But what if instead of treating these fabrics as waste, we could transform them into something useful — fuels, chemicals, and monomers for new materials?
Researchers from Aarhus University, in Denmark [56.2°N, 10.2°E] have pioneered a process that does exactly that. By applying hydrothermal liquefaction (HTL), they have managed to break down mixed textile waste into valuable hydrocarbons and key chemical building blocks. This breakthrough offers a new path to dealing with one of the most challenging waste streams of our time.
Beyond Mechanical Recycling — A More Radical Approach
Traditional textile recycling has long been constrained by the complexity of fabric blends, dyes, and additives. Cotton can be shredded and re-spun, but with reduced quality. Polyester can sometimes be chemically broken down into its base monomers, but only if the input is pure. Most textile waste, however, is a chaotic mix of fibres, coatings, and contaminants, making it nearly impossible to recycle efficiently.
HTL offers a way around this problem. By using high temperatures and pressures in a water-rich environment, this process breaks down textiles at the molecular level, producing:
- Bio-oil — a hydrocarbon-rich liquid that can be further refined into fuels or chemicals
- Terephthalic acid (TPA) — a key ingredient in polyester production, recovered at high purity
- Gaseous by-products — which can be used for energy recovery
- Char — a carbon-rich solid with potential applications in materials production
Crucially, this technique can handle real-world textile waste, not just carefully sorted mono-material inputs.
Scaling Up — The Role of Water Recycling
One of the most significant advances in this study is the use of aqueous phase (AP) recirculation. Normally, HTL requires a lot of water, but by recycling the process water, the researchers were able to:
- Increase oil yields from 5% to 39%
- Boost terephthalic acid (TPA) recovery to 48%
- Reduce energy consumption per kilogram of recovered material
This means that instead of just converting textiles into low-value sludge, this method maximises the amount of useful products extracted, making the process far more commercially viable.
From Waste to Fuels and Chemicals
Once the bio-oil is produced, it can be further refined through hydrotreatment. This process removes oxygen, nitrogen, and other impurities, producing hydrocarbons that can be used as:
- Blended fuels for transport (kerosene, diesel, marine fuel)
- Feedstocks for the chemical industry
- Base materials for plastic production
While challenges remain — particularly the high nitrogen content of the oil, which complicates further refining — the study shows that discarded textiles can be successfully transformed into liquid fuels and valuable raw materials.
Taking Action
For Northern Europe, where circular economy policies are driving ambitious recycling targets, this technology could be a game-changer. Instead of relying on low-value downcycling, we now have a way to turn textile waste into high-value resources.
Further developments in catalyst technology, process efficiency, and policy incentives will determine how quickly this method can scale. But the vision is clear: a world where fast fashion no longer ends up in landfill, but in a closed-loop system where every discarded garment is a resource waiting to be unlocked.
Source
Aisha Matayeva, Juliano Souza dos Passos, Petr Straka, Sofie Klara Gissel Skibsted, Patrick Biller, Chemical recycling of post-consumer textile waste via continuous hydrothermal liquefaction and hydrotreatment for simultaneous monomer and hydrocarbons production,
Chemical Engineering Journal, 2025-02-26
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