Mono-material footwear could probably become the most sustainable option in the market.
Designing for recycling: a reality check
Many people have a wrong idea about how footwear recycling currently works. For instance, a lot of designers focus on “design for disassembly”, assuming that shoes are somehow taken apart in the recycling process, but this actually never happens. So how are shoes recycled then? In order to be economically feasible, waste processing should involve high speed and minimal human labour, so that is why shoes are thrown into a big shredder while they are still intact and then the various materials are separated automatically based upon density, using a series of machines.
After this process you are left with granulates of fibres, leathers, plastics/rubbers and foams. (Any metals are often taken out beforehand). Generally, these are still a mixture of many different materials, with a multitude of chemical compositions. Because of that, these granulates are often downcycled into insulation materials or backings of carpets, for instance, rather than back into shoes.
Another issue that can come into play here, is that shoes in the waste stream can be quite a few years old, so the resulting granulate can actually be non-compliant with current chemical compliance standards, also making it hard to use in new shoes again.
The case for mono-material shoes
It is thus understandable why a lot of well-intended “eco” shoes could actually cause more problems than they solve. Yarns of recycled PET mixed with natural fibres, rubber soles with coffee grounds, combinations of bio-based and non bio-based foams… all these could result in granulates that are almost impossible to reuse! These shoes can best be incinerated to create energy or (in the USA) they will likely still end up in landfill.
Because of all this, Adidas is focussing on mono-material shoes. All components start from the same raw pellets of TPU, which are then processed into foams, yarns and films that make up the shoes. When these shoes are ground up after they have been worn, remelted and cut into pellets again, you have a pure TPU granulate, which you could indeed introduce back into footwear manufacturing.
What is important to understand here though, is that these recycled TPU pellets will no longer have the same quality as the virgin TPU pellets that the first shoe originated from. Polymers like TPU loose quality as they are processed, worn and then ground up again, so that is why only 10% of each Adidas Futurecraft Loop shoe can actually consist of recyled TPU. This means that 90% still has to be virgin plastic. And that is after the first cycle, as you recycle the TPU more often, the percentage of recycled plastic in a shoe will probably be even lower.
So it is a significant first step in a much longer process. Until now, people would associate mono-material shoes with Crocs; Adidas managed to create a mono-material shoe that looks just like their other multi-material footwear and that certainly is a big achievement.
There are many reports stating that the Futurecraft Loop can be turned into new shoes over and over again in an infinite loop and that is not correct. That is a future goal, not a reality.
It needs to be seen how Adidas will design the actual recycling process. In order to make the Loop work, you will have to collect the worn shoes and put them in a separate recycling process, away from multi-material footwear. They mention they are working with a startup that offers consumers cash if they hand in their old Adidas sneakers.
The question is where do you take the shoes to be recycled? Sending individual pairs by (air)mail to a single location will increase the footprint drastically. One option is that since it is all TPU, the recycling process might be simplified a bit – shoes being ground-up in store, turning the process of handing in your worn shoes into something engaging that brings people back into stores.
Currently, the parts for the Adidas Futurecraft Loop shoes are made in China, but assembled in Atlanta. This brings forward a big issue: One of the main hurdles for local manufacturing is the lack of locally available materials. We do not just want be able to assemble shoes locally, but also to produce all supplies locally. Only then will products like the Futurecraft Loop really make sense. Otherwise you still have to ship the granulate of the recycled shoes half way around the world to add virgin TPU and make the parts and then ship those parts back again to be assembled locally.
The extra carbon footprint of transportation will then annihilate the environmental advantages of making a mono-material shoe.
Will infinite plastic recycling even be possible?
But even if we can fully produce and recycle locally, then we still need to work on a better recycling method. TPU cannot be recycled continually if we use the method of shredding shoes into granulate; after a few cycles the quality becomes too low and it will still have to be downcycled and eventually discarded. If we could return plastics to their molecular building blocks through a closed-loop chemical process, then infinite plastics recycling becomes an option.
For the long-term though, we do not want to create any more plastics, as is still the case for the Futurecraft Loop in its current state. Completely eliminating plastic is also a key element of Parley’s vision that Adidas is fully subscribing to. They see plastic as a design failure that needs to be avoided, intercepted and redesigned.
Parallel to finding solutions for existing plastics, we need to focus on biofabrication – growing organic materials in a lab that can be recycled and eventually biodegraded – which is why Parley is also partnering in the annual Biofabricate conference that is organized by Modern Meadow.
Designing mono-material shoes
The purpose of the Futurecraft Loop is to initiate a new method of circular manufacturing for Adidas that will eventually be applied to more segments of the collection than just Futurecraft. That also means that in-line designers will now need to be trained to design for this method; otherwise you might see them applying “old thinking” to new concepts and that never leads to the best results. We often see though, that as a product transitions from the innovation department to in-line, this kind of training is forgotten or too short, due to time constraints.
Designing for mono-material footwear could come across as very limiting to in-line designers, because it essentially requires a very different toolbox to play with. Understanding what material you can and cannot make of TPU, is still the task of the innovation department. But if you are a designer and you are told that you can use a TPU knitted upper, then you will now need to be creative in other ways than before to adjust the look and feel of that upper. Basically, where you would normally play with colours, prints, finishes and different densities of materials, you will now need be creative with adjusting textures, structures and volumes of your one base material in order to achieve the desired look, feel & function.
It would also be wise to start exploring how to 3D print directly on the upper with TPU. It is a very common material for 3D printing and the adhesion to a TPU upper of the same chemical composition would be optimal. Furthermore, 3D printing would allow for customisation and then it would also make more sense to assemble the shoes locally.
Applying colour will be an interesting challenge. The absence of colour in this first Futurecraft Loop shoe is intentional. With polymers, colour is usually applied quite early on in the process, when the basic compounds are made, not after the product is finished.
If you design shoes with recycling in mind, then you hope to keep the granulate as pure as possible. If a shoe has multiple colours, you will also get a multi-colour granulate and even if you have mono-colour shoes, you will still have to somehow separate colours in your recycling process, unless you are willing to use this issue as a design feature and end up with only heathered colours. You could apply colour recognition sensors in your waste management system, but separating those colours will still be tough, because they all have the same density.
This could be a nice challenge for finishing companies. What if you could create a TPU colour finish that is applied on the assembled product and fades away over time? I do not mean it to peel off – we do not want any waste – we just need the colour to fade, for instance because it has not been fully UV stabilised.
In that case, the colour level could even work as a timer, indicating when you could hand in your shoes to have them recycled and buy new ones. That could bring us closer to the idea that consumers subscribe to a brand as a service, rather than buying individual products. Apart from technological research, this will also require an entirely new business model.