Stella McCartney has partnered with material science company Balena to create its new S-Wave Sport trainers, part of its Autumn 2025 collection.
The sole of the S-Wave Sport is made from Balena’s BioCir Flex, a non-toxic, compostable, recyclable and bio-based alternative to conventional plastics. It is also designed to absorb impact and respond to motion.
BioCir Flex, which is dyed naturally with cinnamon, is as durable as TPU (thermoplastic polyurethane) and as flexible as rubber. It is made from sustainable sources like castor beans, oils, and polysaccharides – ensuring it does not compete with food resources – and biodegrades into renewable biomass when composted in industrial facilities or can be recycled for continuous use.
Known for its circular and ecologically minded approach to fashion, Stella McCartney aims to make use of the most up-to-date and progressive materials that aim to reduce environmental impact and are cruelty free. In 2008, McCartney began phasing out the use of PVC plastic, and by 2010, all of her products were PVC-free.
McCartney actively raises awareness about environmental issues, as seen in her SS25 show at Paris Fashion Week, which emphasised the urgency of protecting nature, where she hosted a street market with 21 stalls selling sustainable produce, including Linda McCartney vegetarian sausages.
Stella McCartney said: “I mean [the new sole] is insane. My shoe designer came up to me and said, ‘smell the sole’. It’s made of cinnamon waste. It smells of cinnamon! And it’s basically 100% plant based, recyclable and biodegradable textile. Its a closed-loop production, so it ensures completely zero waste. It is mind-blowing.”
David Roubach, Founder of Balena Science, said: “This collaboration represents more than just a partnership—it’s a shared vision of a future where materials are circular, sustainable, and high-performance. Stella McCartney has always been a beacon of innovation and responsibility in fashion, and to see Balena’s material, BioCirFlex, integrated into her designs is a milestone I could only have hoped for when we began this journey.”
