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Environmental impact during a product’s life – part 6

In this final article of the series considering sustainability throughout the footwear product lifecycle, we discuss the challenges of developing sustainable end-of-life options for footwear.

by Nicola Pichel-Juan

Image © kulkann |

The development of sustainable end-of-life solutions for footwear is one of the biggest problems facing the industry. It is estimated that more than 24 billion pairs of shoes are produced globally each year, with more than 85 per cent of these ultimately being sent to landfill.

As discussed in part 5 of this series, it is vital to extend the viable life of the footwear as far as possible. This can be done by making it durable and long-lasting, ensuring that it can be repaired or restored, and encouraging strategies that can give the item a second life – such as through refurbishment or resale programmes.

However, all footwear will eventually reach a point where it is no longer wearable and cannot be repaired. What happens to it at that point is crucial if the product is going to be truly sustainable.

The power of legislation

Any organisations which are not already considering end-of-life solutions for their footwear will be forced to do so in coming years. Such pressure will be brought to bear by existing and planned legislation requiring companies to take more responsibility for what ultimately happens to the items they place onto the market. This includes a new law in France – ‘Loi relative à la lute contre le gaspillage et a l’économie circulaire’ (AGEC) – which was discussed in more detail in the article ‘Sustainability – legislation update for the footwear sector’. The legislation requires all footwear to be labelled to provide information to the consumer on how it should be responsibly disposed. The proposed ‘EU product passport’ will also set requirements to ensure that products are easier to maintain, refurbish and recycle.

Although most organisations are now working to use more sustainably-sourced materials in their products, what is likely to happen to those items at the end of their life is not always fully considered. For instance, while there has been a huge increase in the use of recycled polyester for many applications, this substance can be extremely difficult to recycle again – especially if it is blended with other materials. While recycling technology is developing all the time, recycled polyester is currently unlikely to provide a true ‘circular’ solution.

Where does footwear and clothing sent for recycling actually go?

While some fashion items will be placed into the most appropriate recycling stream for that material or be resold within the original market, there is often an ‘invisible problem’ in which much of the footwear and clothing placed into recycling schemes in good faith by the original owner may end up being effectively ‘dumped’ in other parts of the world.

For example, in 2019, 185,000 tonnes of used garments were reportedly imported into Kenya (said to be an increase from the 2013 figure of 100,000 tonnes). Greenpeace has estimated that 30 to 40 per cent of this clothing was unable to be sold due to its poor quality, which led to these products being disposed of within Kenya, typically in landfill. The huge volume of imported textiles may also effectively hamper the domestic textile industry by reducing the demand for new, locally-produced goods.

Final resting place

Most footwear placed into municipal waste streams around the world today is likely to end up either being sent to landfill or incinerated. However, a proportion of footwear – either intentionally or accidentally – will also end its life in other environments, such as rivers, seas and in the ground. In an ideal scenario, footwear would not harm any environment into which it may be placed and would potentially even enhance some of those environments – as an example by breaking down into nutritious compost. As a starting point, it is probably useful for organisations in the footwear supply chain to consider the most likely, or desired end-of-life scenario for their products.

Biodegradability in a bioreactor plant or a landfill environment is a potential option for products and materials that cannot be recycled. When additives are incorporated into materials to enhance their ability to biodegrade, the item breaks down into biogas that can be captured, purified and converted into biomethane which can be used as a ‘green’ fuel. SATRA can arrange for the two main tests used to assess the biodegradability of a material under these conditions – ASTM D5511-18 (equivalent to ISO 15985) – ‘Determining anaerobic biodegradation of plastic materials under high-solids anaerobic-digestion conditions’ and ASTM D5526-18 – ‘Determining anaerobic biodegradation of plastic materials under accelerated landfill conditions’.

Dmitry Naumov |

A biogas production plant in Germany

Compostability is increasingly being considered as a sustainable end-of-life option, and this is often linked to the large uptake in the use of bio-based materials. A material that can break down into compost that can then support the growth of new crops is a truly circular solution. For a material to be certified as ‘compostable’, it must pass the following tests and assessments:

This testing was discussed in more detail in the article ‘Investigating the biodegradability of footwear’. There are two main specifications available for compostability – BS EN ISO 14855 – ‘Determination of the degree of disintegration of plastic materials’ and BS EN 13432 – ‘Packaging: Requirements for packaging recoverable through composting and biodegradation’. Again, SATRA is able to arrange for all relevant testing and certification to these two specifications.

Dmitry Naumov |

Compostability is increasingly being considered as an end-of-life option

It is important to note that the information above refers to composting in a controlled industrial composting environment and does not mean that an item will be compostable in a home-composting environment. In fact, although there has been a proliferation of single-use items such as cutlery and coffee cups that claim to be compostable at home, an extensive study carried out recently in the UK has found that in many cases the items do not break down. This is largely due to the variability between the test environment used to assess if something is home-compostable and the actual conditions in home composting bins. Even industrial composting sites are struggling to deal with some ‘compostable’ items, as they simply do not break down sufficiently within the time constraints of the process.

In terms of footwear, compostability is still in its infancy and requires both the development of materials and products that are compostable, and the infrastructure that can and will accept footwear for processing in this way.

What is the difference between ‘biodegradability’ and ‘compostability’?

These two terms are often used interchangeably, but actually have quite different meanings.

‘Biodegradable’ means that something has the capability of being degraded by biological activity – including the actions of bacteria and fungi – and ultimately breaks down into carbon dioxide, other gases (an example being ammonia), water and biomass. The term is not specific to a particular environment. Some items may biodegrade in an anaerobic environment (without oxygen) – for instance, most landfill sites – and some may biodegrade in an aerobic environment (with oxygen), such as in compost or soil.

Something that is ‘compostable’ will break down in a specific composting environment under controlled conditions. All compostable items are biodegradable, but not all biodegradable products are necessarily compostable.

A final option to consider is footwear that can be shredded or ground up to create a material that can then be used as input to make new materials and components as part of a circular process. This type of solution is typically accompanied by the company offering a take-back scheme to ensure that it is convenient and straightforward for the consumer to get the footwear into its intended end-of-life solution.

From small beginnings

The options discussed above of biodegradable, compostable, or otherwise recyclable footwear are all desirable options for new footwear that is being developed. However, that still leaves billions of pairs of footwear in existence that were not designed or manufactured to go into any of these processes. Currently, the main viable option for these items is to disassemble the footwear into its constituent parts and to get each individual material into the best possible recycling or waste stream available in that locality.

This is how testing samples submitted to SATRA are currently being processed. The outsoles are removed and are reprocessed into items such as playground surfaces and car mats. The textile materials are shredded and go into insulation, the leather goes into waste-to-energy processes, and any metals are sent into metal recycling streams.


Some footwear outsoles can be reprocessed into playground surfaces and other products

While some of this may be downcycling, thus resulting in lower-quality items, it is a better option than incineration or landfill. In the 18 months to the end of June 2022, this action reduced the amount of waste SATRA sent to landfill by around three tonnes. The number of pairs of footwear that can be processed in this way is limited by the fairly manual processes that must typically be used to break the item down into the different material types. Nevertheless, SATRA is aware of projects that are looking to add a greater degree of automation to the process. This end-of-life option could become more viable in future if products are designed for disassembly, and as recycling technology develops to allow more materials to be recycled while maintaining a higher quality.

How can we help?

Please contact to discuss potential end-of-life options for your footwear, or to arrange testing and certification.

Publishing Data

This article was originally published on page 10 of the March 2023 issue of SATRA Bulletin.

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