The lifespan of a shoe continues after the wearer has decided it’s useful life is over. It’s important to factor this in, because the most likely destination of a used shoe is a landfill site. Only a small proportion of shoes follow the alternative routes of reuse and recycling, and even then the ultimate endpoint is still landfill - it's just been postponed (rather than eliminated).
It’s difficult to find statistics that specifically mention footwear waste. Any information on textile waste streams most likely refers to clothing. The most up-to-date figures from 2007 state that in the EU, “the waste arising from post-consumer shoes will reach 1.2 million tonnes per year”. 
Where does this 1.2 million tonnes go? In the UK, approximately 15% (or 26,244 tonnes) of post-consumer shoe waste is collected and redistributed as secondhand. The remaining 85% (or 142,756 tonnes) is sent to landfill.  Why is this such a high proportion? Or to address the bigger issue, why are shoes being thrown away in the first place?
When it comes to looking for solutions, the first suggestion might be to pass your shoes on to someone else. But is this the best solution for post-consumer shoes?
“In the UK, Oxfam alone with its shop donations and door-to-door collections recovers around 5-10 tonnes of worn or unwanted shoes every week.”  As a solution for avoiding post-consumer shoe waste, how successful is this? Sure, it’s a nice feeling to donate your unwanted clothing and footwear. But looking at it from another angle, how often do you buy second hand shoes? Many people stigmatise pre-owned items for being “unsanitary” or for their “smell”. Whilst this problem with clothing can generally be solved with a run in the washing machine, footwear is a different story - secondhand shoes can be a little trickier to clean. Other solutions should be implemented first.
Recycling & Recyclability
There’s a general lack of recycling, with less than 5% of the world’s end-of-life shoes being recycled.  This is partly because of the materials used. Nike recognises the importance of material selection; Hannah Jones, their Chief Sustainability Officer says, “We know materials account for about 60% of the environmental footprint of a pair of Nike shoes.” 
Some materials don’t have the necessary recycling facilities in place. Leather is a popular material choice for shoes - “more than 60% of the UK shoe sales are leather-based shoes”  - and yet the recycling of leather from post-consumer shoes has not been commercially exploited. 
Other materials can be recycled, and yet it's not happening. EVA foam is a case in point. According to recycling specialists, INTCO, “At present, the global ethylene-vinyl acetate copolymer (EVA) recycling rate is generally very low. Recycling EVA foam companies are also very few.” 
Within any one pair of shoes, there’s a long list of materials: “Footwear is incredibly difficult to recycle as it can contain up to 40 different types of material, many of which are stitched or glued together.”  This makes it difficult to separate each of the different materials for recycling. The Centre for Sustainable Manufacturing & Recycling Technologies (SMART) at Loughborough University has devised a footwear recycling system that shreds the shoes and automatically sorts fragments by density. This method should be both environmentally and economically sustainable.
But what if our shoes were built to be recycled? Planning how shoes can be recycled post-consumer use generally doesn’t come into the design process - it’s an afterthought. Permanent methods cannot be repaired, so these shoes have a relatively short lifespan. One such example (often associated with cheap footwear) is cemented construction, where the sole is attached to the upper with a light layer of glue. Luxury brand Bally state that "once the sole and upper are parted or damaged, this is the end of the love affair. A cemented shoe cannot be resoled, and so it may only have a limited longevity." 
Another example is vulcanization - the process of turning rubber into a polymer - often seen in skate shoes. This blog post describes the process with visual cues, and can also be seen in action here. Vulcanised shoes can’t be resoled because the upper, outsole and tape bond together during vulcanisation, preventing them from being separated.
So, if certain materials and methods are difficult or impossible to recycle, why can’t we implement the design strategies like minimal design to limit their use? Fewer materials makes it easier to separate a shoe for recycling.
But being less bad still isn’t good.
Some shoe brands are marketing their product as being 100% biodegradable. This may appear as the ultimate sustainable solution, but most brands achieve this by incorporating certain bacteria within the shoe components to aid decomposition. This only resolves a small part of the shoe lifecycle - the technology does not improve the pollution of extracting raw materials or production processes.
Simple Shoes developed the “BIO-D additive”, enabling their shoes to decompose within 20 years rather than 1,000 years.
We also wish to point out that we haven’t seen any scientific studies that look into the long-term ecological impact of this technology.
Within the design world, there are a number of terms centering around the idea that our waste shouldn’t be wasted e.g. circular economy, cradle to cradle or a closed loop system. The list goes on. But they all contain a combination of design practices like biomimicry and Design for Disassembly, placing them within one holistic system.
If we go by the WRAP definition, a circular economy is “an alternative to a traditional linear economy (make, use, dispose) in which we keep resources in use for as long as possible, extract the maximum value from them whilst in use, then recover and regenerate products and materials at the end of each service life.”
The importance of nature within this kind of system is emphasised by this Ellen MacArthur Foundation explanation that states that cradle to cradle design “perceives the safe and productive processes of nature’s ‘biological metabolism’ as a model for developing a ‘technical metabolism’ flow of industrial materials.”
There are steps that could be taken to enable a circular economy to exist within the footwear industry:
Repairable manufacturing methods should be chosen over permanent methods e.g. vulcanisation. For example, the Goodyear Welt is a long lasting shoe construction method that is relatively easy to repair.
Quality materials e.g. latex are needed to ensure that the waste can become food for the next cycle.
Refuse collection systems need to be in place. Some materials need certain criteria in order to biodegrade.
Very few examples of this thinking exist in today’s footwear industry. The PUMA’s Incycle range, which launched in 2013, is one such illustration. "The materials used in the InCycle products belong to either a technical or biological cycle."  In preparation for the end of its useful life, PUMA have implemented a take-back scheme which sees the trainers shredded and turned into compost, the jacket turned into polyester pellets and old backpacks become part of new ones.
Looking for more examples? We mentioned Design for Disassembly when discussing design strategies.
- Huge quantities of post-consumer shoe waste exist. This is a big problem that needs an equally big solution. The answer ultimately lies in reducing the ‘need’ for new shoes. This could be done by raising awareness of the culture of consumerism like the Patagonia “Don’t buy this jacket” advert - honesty and transparency is attractive to consumers. The other option would be to encourage the use of pre-existing shoes, for example, by advising consumers on how to mend worn shoes.
- But shoes don’t last forever and there will always be a need for footwear manufacture - it just needs to be good footwear manufacture. The entire lifecycle of a pair of shoes needs to be considered from the design process all the way to post-consumption. The best outcome would come from using a number of approaches e.g. designing a shoe without the unnecessary materials or features, choosing materials that fit within a circular economy (e.g. the wet-green® OBE tanning agent is Cradle to Cradle Certified™) and offering repair services that deal with wear and tear.