Running is a wasteful sport. Each year billions of shoes are manufactured, worn until they start to fall apart and chucked into landfill. It’s estimated that 300 million pairs of running shoes are thrown away each year in the UK alone.
In a long-term plan to avoid excess rubbish, adidas is reconfiguring its factories to produce shoes that can be ground into pellets, melted down and made into new running trainers. The first experimental shoe of this kind is.
At first glance, the running shoe doesn’t look too different from any other. It’s an off-white trainer that’s made-up of all the usual components: a foam midsole, an outer sole, a knitted upper, an insole, laces and a torsion bar that’s added for stability.
Where Loop does stand out is in how it’s made – and remade. Engineers at adidas have made the entire pair of shoes from one material, a version of thermoplastic polyurethane (TPU). On average, other adidas trainers are made of at least 12 different materials. “The concept is that this shoe is 100 per cent recyclable and also zero waste,” says Tanya Sahanga, a materials engineers from adidas’s Futurecraft team, which has previously experimented with 3D printed trainers and trainers made from plastic pollution hauled from the ocean.
“We take the first generation shoe back,” says Graham Williamson, a senior director of Future Apparel at adidas and the lead on the Loop project. “We will recycle that and use that recycled material to create components for the subsequent shoe.”
To recycle the shoe, adidas has them washed and shipped to one of the plants of its industrial partner ASF. Once they arrive here the material is ground down into fine pellets, then melted back to its original state from which it can be turned back into a shoe again.
Crucially, TPU can be melted down once it has been used. TPUs are one type of the plastic polyurethane and is considered to have elastic properties, as well as being transparent, and largely resistant to oil and grease. This isn’t the first time the company has used a variant of TPU within its shoes; in February 2013 adidas introduced its Boost foam, which is used in the majority of its midsoles, after working with German chemical producer BASF.
When used in a midsole, Boost is formed of 2,500 elastic TPU beads that are pressed into a mould to create an unmistakeable rice cake look. “The upper is made from exactly the same material,” Sahanga says of Loop. (It’s an off-white colour because there’s no brightening chemical that usually gives trainers a pristine white look, she says). The problem for her team was that while the TPU can be manipulated into a midsole relatively easily, turning it into a thread that can be used to create a shoe’s upper is far more challenging.
The breakthrough in the project, which has been running for six year, came in 2016 when engineers modified the plastic so that it could be spun into a traditional fabric-style strand. “TPU yarn is available on the market but we have developed one specific for us and have advanced it,” Sahanga explains. Before this, adidas didn’t have one material that it could use to create an entire shoe – traditionally, the uppers of running shoes are made from polyester.
“At the start of 2017 we were able to make shoes and components in repeat, before that we had only been able to make one or two shoes at a time,” Sahanga says. “We made a batch of 50.”
Creating a new type of yarn for the upper wasn’t the only issue. The glue that shoes are pieced together with can’t easily be broken down during the recycling process. Workers assembling shoes using the glue have to wear masks to protect themselves from the fumes. To get around this, adidas has completely removed the glue from the shoes. Instead, it’s using lasers to weld the parts of the shoe together.
The technology was developed through its first speed factory in Germany. There are now two speed factories, the other is in the US, and within them robots assemble adidas trainers in less than a day. The factories allow adidas to move faster with its manufacturing and take some reliance away from factories in Asia where more than 90 per cent of its 360 million trainers are made each year.
The traditional factories can be environmentally inefficient. Landfill and environmental impacts are a huge problem for the sports manufacturers and the fashion industry as a whole. One 2012 study from researchers at the Massachusetts Institute of Technology found that a single shoe running shoe can include 65 individual parts, all of which normally end up in landfill.
While shoes can be recycled already, adidas’ effort is different because it’s using materials to make entirely new shoes that are designed for performance.
But it’s not alone. Nike has a recycling scheme it calls Grind. The company takes in old shoes, from any manufacturer, throws them into a machine that will break them down and then uses the materials to make flooring. 18 different substances have been used to create indoor basketball courts, playgrounds and astroturf football pitches.
Minimalist running shoe manufacturer VivioBarefoot has constructed shoes using repurposed algae and is working on a plant-based line that includes a material based on industrial field corn.
Going forward, Loop could change how adidas operates entirely. The Boost material is used across its range of lifestyle shoes, not just those designed for runners. There’s also potential for a new business model, which could conceivably include the option of a shoe subscription. A worn out running shoe may automatically be replaced with a recycled model after a certain number of miles. That used pair would then be melted down and shipped out as a new product.
But that’s still some time away. At the moment adidas needs to make Loop scaleable. So far it has only tested a few hundred shoes with its own staff. As it announced the shoes, it also handed out 200 pairs for journalists to try. These will all be recycled. The ones it has tested internally have all be subject to standard running shoe tests, being put through their paces over 500 kilometres of pavement-bashing.
“For the recycling industry, this is peanuts,” Sahanga says. “We are talking about one to five tons – that’s nothing. These guys process in the triple digits of tons.” Williamson adds that adidas expects the whole recycling and remaking process to take about six months. This is because it doesn’t have the speed factory technology in place within its Asian factories yet. “That’s geared to working with multiple materials, multiple components to create the shoe within an assembly process that involves a lot of gluing,” he says.
The company expects to offer a limited commercial run of the shoes towards the end of 2020. At that point, it might be the last running shoe you ever buy.