From Court to Sole: How One Designer Is Slicing Tennis Balls Into Shoes Instead of Landfills
Every year, roughly 400 million tennis balls are manufactured worldwide. Only about one percent of them are ever recycled. The rest follow a depressingly short and predictable path. In professional matches, balls are typically replaced every seven to nine games—about thirty minutes of play. Recreational players may get a few sessions before the internal pressure drops, the bounce softens, and the felt begins to wear. Once that happens, the ball is discarded. From the court it goes into a bin, and from the bin it usually goes into a landfill, where it can sit for around 400 years, slowly releasing methane and contributing nothing useful.
That volume of waste has long been an open secret in tennis. The sport produces an object engineered for resilience—rubber core, carefully bonded felt exterior—then treats it as almost single-use. Manufacturing a single ball involves multiple steps and materials that are difficult to separate later. The adhesive that holds felt to rubber resists conventional recycling. The result is a durable product that refuses to disappear and is rarely given a second purpose.
Soroosh Riazi Isfahani, a designer trained at the Royal College of Art and Imperial College London, decided the situation was worth confronting directly. His response is SLICE, a footwear project entered into the James Dyson Award 2026. Rather than grinding the balls into anonymous crumb or melting them into a generic compound, Isfahani cuts them. Using a custom guide for precision, he sections the used balls and works the pieces into a shoe. The rubber remains rubber. The felt remains felt. The material keeps its identity.
This approach is more radical than it first appears. Most sustainable design strategies still begin by destroying the original object. Materials are shredded, melted, or chemically broken down so they can be reconstituted as something new. That process consumes energy, often degrades performance, and tends to erase any connection to the source. Isfahani started in that conventional place. Early experiments involved shredding tennis balls and blending the material with natural rubber to form outsoles. The method worked on a technical level, but it felt incomplete. Shredding erased the very qualities that made the ball interesting: its layered construction, residual bounce, and textured surface.
SLICE reverses the logic. Instead of asking how to turn tennis balls into a generic recycled feedstock, it asks what the ball is already good at. Tennis ball rubber is tough and resilient. The felt provides grip and a distinctive tactile quality. These are properties that belong on the underside of a shoe. By slicing rather than pulverizing, the designer preserves those characteristics and builds the footwear around them. The ball is not a footnote in a sustainability claim; it is the central material and the conceptual starting point.
The process itself is deliberately low-intervention. A used ball is cleaned, positioned in the custom cutting guide, and sectioned. Those sections are shaped and integrated into the shoe structure. No high-temperature processing or chemical separation is required to reclaim the material in the first place. Energy that would have been spent breaking the ball down is saved. The resulting footwear carries visible traces of its origin—the curve of the rubber, the texture of the felt—rather than hiding them under a uniform new surface.
This matters in a broader industry context. Footwear is notoriously difficult to make circular. Shoes combine multiple materials, adhesives, and components that are hard to disassemble at end of life. Many “recycled” sneakers rely on shredded plastics or other post-consumer waste that has been heavily processed, then marketed with a green label. The connection between the waste stream and the final product is often tenuous. SLICE tightens that connection. The tennis ball is not an ingredient added for storytelling value; it is the structural and visual foundation of the design.
The project also highlights a quiet absurdity in sports equipment culture. A ball that takes days to manufacture and is engineered to survive repeated high-impact strikes is routinely retired after a fraction of an hour of professional use. The same object that is good enough for elite competition is treated as worthless the moment its bounce falls outside a narrow performance window. Giving it a second life as footwear does not solve the entire waste stream—400 million balls is an enormous number—but it demonstrates a different attitude toward material value. Durability is not a liability if the product can be redirected into a new use that benefits from that same durability.
Scaling such an idea presents obvious challenges. Collection systems for used tennis balls remain limited in most places. Consistency of supply, cleanliness, and material condition vary. Footwear manufacturing demands reliable performance standards for abrasion resistance, flexibility, and safety. Integrating irregularly shaped sections of tennis ball into a consistent shoe requires careful design and probably some adaptation of production methods. Yet the core insight remains powerful: the material already possesses properties suited to the new application. The design task is to respect those properties rather than erase them.
Isfahani’s work sits within a growing recognition that true circular design is not only about recycling rates. It is about matching waste streams to applications that can use their existing strengths. Furniture makers have experimented with whole tennis balls as cushioning or acoustic elements. Other projects have ground them into crumb for playground surfaces or shoe soles. SLICE distinguishes itself by refusing to homogenize the material. The ball remains recognizably itself even after it becomes part of a shoe.
In the end, the project is less a finished commercial product than a clear demonstration of method. One custom cutting guide. Used tennis balls that would otherwise spend centuries in landfill. A pair of shoes that carry the history and the performance characteristics of their source material. For an object that is typically discarded after thirty minutes of professional play, that is a more fitting conclusion than burial under layers of other trash.
The numbers remain stark—hundreds of millions of balls, almost none recycled, centuries of persistence in the ground. SLICE does not pretend to absorb that volume alone. What it offers instead is a practical and conceptually coherent alternative: stop treating high-performance waste as worthless, and start asking what it is already capable of becoming. In the case of the tennis ball, the answer turns out to be something people can wear on their feet.
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