The polyester T-shirt you threw away three years ago may have ended up in a 300-degree oven, turning it into high-calorie carbonized granules. Its ash, according to researchers at the Kaunas University of Technology in Lithuania, it was not supposed to be a waste to be disposed of, but an additive that can replace up to 7,5% of cement and increase the compressive strength of concrete by 16%. A bit like if the problem of the textile waste and the construction industry emissions problem met and decided to collaborate: neither problem is solved, but both are alleviated.
Europe generates billions of tons of textile waste every year. Most of it ends up in landfills or incinerators. fiber-to-fiber recycling (transforming old clothes into new fabrics) is still in its infancy, and when it works, it produces cleaning rags, padding, and insulation. Low-value materials.
The problem is that modern fabrics are complex mixtures: synthetic fibers, chemical additives, microplastics that are released during washing. Sorting, separating, recycling is technically difficult and expensive. So it's either burned or buried. And every ton burned contributes to CO₂ emissions.
Textile ash, the Lithuanian discovery
The team led by Dr. Raimonda Kubiliūtė, from the Department of Silicate Technology, has developed a different model. Textile waste is thermally treated at around 300°C in an oxygen-free environment (pyrolysis). The process generates carbon-rich granules with high calorific value. These granules can be used as an alternative fuel in energy-intensive industries (such as cement factories). Combustion, however, produces ash. And here's the interesting part.
The mineral composition of the ash varies depending on the type of tissue burned, but laboratory tests show that This ash can function as a supplementary cementitious material (SCM, Supplementary Cementitious Material). It replaces up to 7,5% of traditional Portland cement and, under standard curing conditions, increases the compressive strength of samples by up to 16%.
The cement industry, particularly rotary kiln firing processes, contributes to the8% of global CO₂ emissionsReducing the sector's environmental impact is a necessity, and textile ash offers a double benefit: fewer emissions and less textile waste in landfill.
Textile waste, not just ash: fibers work too
Kaunas researchers also tested another approach. Adding directly recycled polyester fibers (recovered from discarded clothes) to the concrete, in the amount of 1,5% of the weight of the mixture. Result: Increase in compressive strength between 15% and 20%, improved resistance to freeze-thaw cycles, reduction of microcracksThe fibers act as mechanical reinforcement, while the ash acts chemically. Two different approaches, the same goal: transforming a problem (textile waste) into a resource for construction.
As Dr. Kubiliūtė explains:
“This technological solution not only reduces CO₂ emissions during cement production, but also offers an innovative and environmentally friendly approach to textile waste management.”.
The research is part of the project Textifuel (Production of Alternative Fuel from Textile Waste in Energy-Intensive Industries), conducted together with the Lithuanian Energy Institutetute.
The circular economy enters the construction site
The idea of using industrial waste as an additive for cement is not new. Rice ash, coal fly ash, calcined clays, even mollusc shells: global research has been moving for years towards additional cementitious materials that reduce dependence on Portland clinker.
The novelty of the Lithuanian work is its specific application to textile waste, a particularly problematic waste stream. Most European countries collect only a fraction of post-consumer textiles separately, and only a tiny percentage is transformed into new products. The rest disappears. Using this invisible mass as a construction resource could open a scalable market: generate energy by burning textile granules, recover the ash, and sell it to cement factories. A closed-loop circular economy.
Textile waste in cement: it needs to work outside the lab too.
The research is still in the laboratory phase. Industrial feasibility studies, ash quality standardization, supply chain analysis, and a complete life cycle assessment are needed. Not all fabrics burn the same way, and not all ash has the same mineral composition. It's important to understand which blends work best, which chemical additives in clothing create problems, and whether any pollutants are released during combustion.
The principle, however, is more solid than concrete: Reducing clinker reduces emissionsUsing textile waste empties landfills. Two environmental emergencies meet in a construction site oven. Until fiber-to-fiber technology becomes scalable and competitive, burning clothes to build houses may be less absurd than it seems. The future of sustainable construction also lies in the closet.
