Index.01: Your Question's Answered

October 17, 2022

Index.01: Your Question's Answered

When we unveiled the Index.01 recyclable running shoe last year, we received a TON of questions from media and from the public. So we locked our R&D and footwear product experts in a room for a few hours (literally) and did our best to answer them all. On this page, we listed the most common questions (and corresponding answers) to anyone who wants to “nerd-out” (go in-depth) on the Index.01 and the idea of recyclable running shoes.

  • Weight of one pair of Index,01 shoes: 540 grams for two shoes; size 8.5 UK
  • Weight of the materials you can recycle: 495 grams (92% of the shoe)
  • Weight of the materials we can’t recycle (sock liner): 45 grams; 8% (sock liner is made from recycled material)
  • Weight of recycled material used in every Index.01: 83 grams (15 %)
    • Sock liner: 100% recycled material
    • Upper: 40% recycled polyester

Why are running shoes typically difficult to recycle?

Running shoes are difficult to recycle because of the materials that are traditionally used to build them—various synthetic materials, textiles (cotton, wool), foams, rubbers and various bonding agents (glues). More specifically, those materials are all assembled together, so if you want to recycle the shoe, you need to somehow separate those materials from one another. That’s a very complex, time-consuming operation, which is why we took the approach of reducing the number of materials used, and constructing the shoe in such a way that the materials can be separated when the shoe reaches the end of its life. From there, the materials can be recycled separately to be used in a new product.

Can you describe the steps that you'll take to recycle the shoes when you receive them back? How are they disassembled, etc?

First, we gather large batches of shoes to clean them efficiently. Next, we separate the two major materials, TPU and Polyester, manually. We strive to refine this aspect of disassembly in the future. Once we have gathered enough materials to be used in a new product, we send the materials to local partners for recycling. This limits the environmental impact of transportation. One example is the TPU that we collect in Europe, which will be sent to our ski boot manufacturer. We have a global polyester partner that will use the recycled material to manufacture locally, including in the U.S. We are exploring a few options for the second-life of the TPU in the U.S., but not quite ready to share that yet. The sock liners will be stocked until we are able to find a recycling solution. 

How is the recycled TPU used in the ski boots? Does it lose quality as a material when it's recycled?

Actually, we found that we could improve certain characteristics of our ski boots using the recycled TPU materials from the Index.01. Many of our ski boots already use recycled materials. In the case of using the materials from Index.01, it was a matter of arriving at the right mixture of the recycled TPU and virgin TPU in order to maintain the performance and durability standards that we demand from our Alpine ski boots—such as testing of prototypes in our cold chambers as we always do. Roughly speaking, we use one recycled shoe bottom unit in each ski boot shell. 

Can you talk about why making a circular shoe was important for you as a company? 

More than being “important,” it’s necessary. For a couple reasons: First, we know the footwear industry is a large contributor to pollution and we have made a choice to be part of an industry shift that influences how shoes are made, how long they last, and what you do with them when it’s time for a new pair. Secondly, our company is full of outdoor-minded people—runners, skiers, hikers—so being more sustainable is extremely important to our employees. Beyond that, it’s simply important to you, the people who support our brand. Outdoor enthusiasts are passionate about the environment and want to see brands like Salomon make an effort to be more responsible.

How challenging would it be to move all of your products to a circular model? Do you aim for that?

That is the ultimate goal and these principles will influence our product development in the future. And yes, it is quite challenging for a few reasons. The first step is to create a recyclable product, and we’ve done that now with Index.01. Still, when it comes to footwear, people aren’t used to recycling their shoes like they would a milk carton or Coke can, so you need to make it easy for them. So there is the challenge of creating the infrastructure needed to recycle products. We are excited about this big step, but it will take partnerships with companies who are experts in gathering and recycling materials, and perhaps even working with some of our competitors to really transform the industry. Circularity is also about clean sourcing and durability (so that products last longer before they loop back), so we are also working on these aspects as well.

What happens to the ski boot shell after they are used? Do you recycle them too?

Good question. We do work to recycle rental ski boots from resorts. The goal of Index.01 is to extend the life cycle of a shoe, so the materials get used longer in another product. A ski boot lasts about 10x longer than a running shoe, so that's progress. Not perfection, but progress. As part of the French AGEC law (Anti-Waste and Circular Economic) voted on last year, which requires recycling solutions to be set up for sports articles from January 1, 2022, we are working with other French companies and a dedicated recycling organism to set up the national recycling scheme.

Where are the shoes produced?

The shoes are currently produced in Asia. The Index.01 was developed and tested here at the Annecy Design Center. We are opening a local factory in France in 2021. We’ll share more on that in the months to come.  

Why did you not make the Index.01 from recycled materials? And do you use recycled materials in other products?

Part of the upper of the Index.01 is made of recycled materials, and the sock liner is made of 100 percent recycled materials. Maybe you missed that in all the recycling talk. We forgive you. Many of our ski boots are already made with recycled material.

The shoe looks great. However, I am not really sure that white running shoes are the best choice to run outside, other colors?

Geez, tough room here, Mr./Mrs. Fashion! Lot of white shoes out there, don’t you think? Kidding, kidding. The (sustainability) answer is that we're trying to minimize the dye used = less chemicals. But you can wash the shoes! And if you run fast enough, your feet will hardly touch the ground = no dirt.

What’s the heel-toe offset of the midsole on Index.01?

The drop of the Index.01 is 9mm.

What are the areas you are looking to improve in the coming years/months as this area of creating sustainable footwear evolves?

Getting a little technical here with the question, aren’t we? We are working to simplify the separability of the two materials in the Index.01 and ensuring that our product return process has the lowest environmental impact possible. We know that we can’t have a classic collecting system in which many materials get mixed together like a stew. That just wouldn’t make sense considering the effort we went through to create the Index.01 from just two materials. We want to separate the materials while maintaining their purity so we can use them again in a new production system. That’s a new process so it’s a challenge we are currently working to improve. 

Can you explain the challenges of the collection process and why that is crucial to this entire effort?

It’s important to be sustainably consistent in collecting the shoes at the end of their life. We don’t want them to travel all over the planet. That’s why, as a first step, we set up collection centers in each region. From there, we had to find recycling partners in each region to recycle the used shoe materials locally. Salomon can recycle TPU in Europe and in partnership with our factories in Asia, but we had to find solutions for polyester in each region and for the TPU in North America.

Who will use the recycled materials and why not send all of them back to Salomon for ski boots?

In Europe, where roughly 80 percent of Index.01 quantities will be sold, the recycled TPU material from Index.01 shoes is being used to make new Salomon alpine ski boots. We are finalizing the polyester recycling. In other regions, we have partnered with companies that can use the material to make a variety of new products. We did this because we wanted to eliminate shipping the materials all the way back to Europe to make ski boots. This would have had caused a carbon impact that we wanted to avoid.

Why did you decide to use the recycled TPU from the Index0.1 for ski boot shells, rather than suggest they go back into the same type of shoe? How does Salomon’s expertise in the ski sector help that?

Most of our Index.01 shoes are for now distributed in Europe and North America. Our idea was to re-use the material as much as possible locally. If we wanted to re-use the material in a new shoe we would have had to ship the material back to Asia, which is not consistent with reducing our footprint. We are ready to recycle TPU in Europe because that’s already something we are doing for ski boots. We just had to fine-tune a few parameters to make it possible with the recycled footwear material. The amount of recycled material in a ski boot ranges from 5 to 20 percent. We can’t go higher than 20 percent in order to maintain the necessary grade of stiffness in the ski boot.

Will we be seeing an Index 0.2/0.3 etc. as the product gets refined?

The Index, as a concept, will live on in many different products. We have a few surprises in the works, so stay tuned.

What were/are the biggest challenges you face(d) when it came to creating a running shoe that is sustainable? 

The biggest challenge was constructing the shoe in a way that met our performance standards, but could be separated at the end of its life and recycled. Running shoes are difficult to recycle because of the many materials that are traditionally used to build them—various synthetic materials, textiles (like cotton and wool), foams, rubbers and various bonding agents (glues). When those materials are all assembled together, you need to somehow separate those materials from one another when it’s time to recycle the shoes. That’s a complex, time-consuming process, which is why we worked to reduce the number of materials used down to just two, and constructed the shoe so that the materials can be separated when the shoe reaches the end of its life. That was not easy. From there the shoe is washed and materials can be recycled separately to be used in a new product. Overall, another challenge with recycling today is that only brands know the composition of their product, which means they must create a collection system themselves. That can be very costly and might not be the system with the lowest CO2 impact. So that would mean brands working together to create a collective recycling system. The future is exciting.

How do you manage getting the balance right between performance for the runner and sustainability? What were the compromises that you had to make? 

No compromises. That was one of our internal rules in creating the shoe. The key element to the running performance is the plush, nitrogen-infused, TPU-based foam called INFINIRIDE, which can be ground into tiny pieces and recycled when the shoe reaches the end of its life. The shoe’s sole also has R.Camber (rocker) geometry, which helps propel the runner forward with a quick transition so he/she spends less time on the ground. I suppose it’s true that another challenge (in addition to what I mentioned above) was finding that foam material for the bottom unit that was both recyclable and could deliver the perfect amount of shock absorption and rebound needed for road running.

What's the estimated extension of life from making a recyclable product? 

When we talk about life extension, we mainly focus on material life extension at Salomon. The period of traditional use for road running shoes goes from six months to two years, depending on practice intensity, consumer weight and strike. A classic ski boot lasts at least six years. So, by recycling 85 percent of shoe materials into a ski boot, we extend material usage three to 12 times longer. The 15 remaining percent that isn’t going into the ski boot, which is polyester, will be recycled into a yarn and then a fabric. The extension life depends on the fabric usage: shoe, tee-shirt, pants, etc. But we can say we will at least double the lifespan of the fabric used to make that part of the shoe.