In a lab on the outskirts of the small city of Huesca in Spain, shoes are the main topic of conversation. The priority, however, isn’t fashion. Over the past two years, scientists at the company Podoactiva have been creating customised shoe soles using hemp and flax.
“The idea was to print prototypes through 3D printing with sustainable materials,” said Marina Azpíroz, research and innovation manager at Podoactiva, which focuses on developing customised insoles for patients with foot health issues.
The sole Podoactiva has developed was produced as part of the EU-funded INN-PRESSME project, which supports researchers and companies developing bio-based products.
Why it matters: Globally, around 24 billion pairs of shoes are produced every year – roughly three pairs per person alive today. One environmental agency found that the footwear industry is responsible for around 1.4% of annual global emissions – more than many developed nations.
Aside from emissions, shoes are often made from materials derived from fossil fuels. As a result, a single pair of shoes can take up to 40 years to biodegrade, studies show. Plant-based materials such as hemp and flax, on the other hand, are biodegradable.
Added benefits: “Natural fibres are from renewable resources, are relatively low-cost, and have specific strength and stiffness,” said Ulla Forsström, principal scientist at VTT Technical Research Centre of Finland, and coordinator of the INN-PRESSME project.
Podoactiva’s insoles can be integrated in the sole itself, which adds a therapeutic function as well, according to the company, which spent two years developing its flagship product.
“The results have been very good in terms of functionality,” said Azpíroz.
One test involving flexing the sole 10,000 times – mimicking the normal flexion that occurs when we walk – showed no damage nor permanent deformities to the sole.
Further, the sole has antimicrobial properties, which could help to prevent shoes from smelling, the company says.
Spanish group aitiip 3D prints the soles, while Germany’s Fraunhofer ISC supplies a specialised coating. The remainder of the shoe used in the testing process was designed using 100% recycled materials.
The 3D printing process not only reduces waste, but also allows “versatility, customisation, affordability, and rapid production of different parts,” said Forsström.
Podoactiva is now working with patients to test the design, and thinks the approach could be replicated elsewhere in the fashion industry.
For now, just 5% of the world’s shoes are recycled, studies show. The INN-PRESSME project hopes a shift to hemp and flax materials will help to lift that share.
