SLICE: Used Tennis Balls Turned into Sneakers

Soroosh Riazi Isfahani, a design student at the Royal College of Art and Imperial College London, submitted his SLICE project to the James Dyson Award 2026 this summer. The system turns discarded tennis balls into footwear. Manufacturers produce between 300 and 400 million tennis and padel balls worldwide each year, and almost none are reused.

A ball loses pressure after only a few matches. Then, it usually goes to a landfill, where it can take more than 400 years to decompose. Only around 1% are recycled. The rubber, adhesive and felt are bonded in layers that recycling facilities cannot separate cost-effectively. A Grand Slam tournament uses close to 100,000 balls in two weeks. The small amount recovered becomes low-value products such as flooring material or dog toys.

In an effort to find more ways to reuse tennis balls, Isfahani initially shredded the balls, mixed the granulate with natural rubber and produced soles. The process worked, but it consumed significant energy and destroyed the properties that made the material interesting: its curvature, bounce and rubber-to-felt bond. He changed his approach. Instead of shredding the ball, he cut it.