Researchers turn wastewater into clothes dye

What if the pigment in your next jumper came from a wastewater treatment plant? That is the premise of the collaboration between the Delft University of Technology (TU Delft) researcher Yuemei Lin and Dutch sustainable fashion label Hul le Kes, who have produced the first garments dyed with a natural pigment extracted from sewage sludge. The results, published this month in the journal Water Research, could be a turning point for a notoriously polluting industry, such as the clothing industry.

Some of the dyes used in clothes come from cuttlefish, a type of squid. This source of melanin has been used for decades, but it raises ethical questions and is limited in supply, given the seasonal nature of cuttlefish catches. The clothing industry also makes extensive use of chemical dyes harmful to the environment.

Lin's research offers a third way. The scientist succeeded in recovering a melanin-like biopolymer from sewage sludge and applying it to a wool dyeing process. The material shares many of the properties that make natural melanin desirable: ultraviolet light protection, antioxidant activity, redox activity and metal chelation — and it can also accelerate the dyeing process itself.

From lab bench to knitwear

The leap from laboratory to wardrobe had an unexpectedly domestic origin. When Lin's daughter Yiran Zhang knitted a jumper using the dyed wool, it became clear that the material also worked outside the laboratory.

From there, Lin reached out to Hul le Kes — a Dutch label known for combining craftsmanship with circular design principles, and one that had recently been promoted by the Dutch embassy at Paris Fashion Week. The brand embraced the experiment and incorporated the new pigment into a range of garments.

"I'm so happy that they're open to new materials and have gone to great lengths to incorporate them into their fashion designs," Lin said. "It has resulted in some beautiful garments."

A promising but early-stage result

The researchers are careful not to overstate the findings. Before these garments can be brought to market, further testing is required, and approvals must be obtained for the use of this new material in textile production.

Still, the collaboration illustrates a broader logic: the designs demonstrate that science and fashion can reinforce one another in the quest for sustainable solutions. The sludge that remains after treating municipal wastewater is typically an unwanted byproduct; finding a high-value use for it closes a loop that has largely gone ignored so far.

Hul le Kes is also working with organizations including ReShare Store, Yumeko, Grey Label and Fibershed to develop further alternatives to the current fashion system — suggesting this wastewater-dyed collection may be just one thread in a larger effort to remake how clothes are made.