In late April, Puma announced it would make a commercial version of its Re:Suede 2.0 compostable sneaker. The brand created 500 pairs of its Re:Suede sneaker in 2021 as an experimental project, then asked volunteers to wear them for half a year to test comfort and durability. Now, the brand has stated it would make an additional 500 pairs of the commercial version of the shoe. The news attracted significant attention for understandable reasons: it was the latest in a series of new announcements and releases of compostable sneakers and materials by several producers and brands in the last few months and the first by a brand the size of Puma.
All these developments point to compostable sneakers inching closer to the mass market, offering a solution for some of the footwear industry’s long-standing problems with sustainability. “It feels like we’re really close to compostable sneakers reaching the mass market,” says Yael Joyce Vantu, the Chief Product Officer of Balena, a material science company working in the space. “We’re basically already there.”
The footwear industry has a sustainability problem. According to World Bank estimates, fashion, in general, was responsible for some 10 percent of global carbon emissions in 2019, and the industry’s emissions were on track to grow by 50 percent by 2030. And every year, in the United States alone, people throw away more than 300 million pairs of shoes. Because most shoes are made with synthetic fabrics, rubber, plastic and metal glued together with strong adhesives, 95 percent of them end up in landfills, where they can take hundreds of years to break down.
Quest for fully compostable materials is a prominent trend
That’s why, according to Giovanni Maria Conti, associate professor in design at the Polytechnic University of Milan and co-author of the book Designing Sustainable Clothing Systems, the quest to produce fully compostable materials has been a prominent trend in the industry for years. “Materials manufacturers have invested heavily for years to produce biodegradable materials,” he told our sister publication Shoe Intelligence. He said several companies started at least a decade ago to use alternative materials such as apple skins, orange peel and prickly pears to produce leather-like products and recycled PET bottles for sneakers.
He added that most biodegradable materials are tested thoroughly before being put on the market and deliver performance levels similar to those of less sustainable materials. But their availability often remains a bottleneck. “You would need who knows how many tonnes of orange peel if those products become mainstream,” he says. “One thing is having the material, another is its industrial application.”
Biodegradable polymers do not have the same supply problem. However, using them requires a mindset shift from brands, according to Balena’s Vantu. “It’s not like you pick a different material and it’s job done,” she told Shoe Intelligence. “We try to make it as easy as possible for brands to replace plastics, but a rethink is always needed. Brands have to completely change how they think and create products.”
Producing compostable shoes comes with design limitations: there can be no eyelets or aglets, which are typically made of metal, and they have to be replaced with, for example, embroidery. And excessive amounts of adhesive can jeopardize a shoe’s sustainable credentials. But Vantu believes the mindset shift is underway. “In the beginning, brands would come to us, show us their shoe, and ask us to replicate it with compostable materials,” she said. “Now they come to us much earlier in the process, and they understand the design has to change.” She says Balena’s compostable materials can already compete on price compared to plastic equivalents.
Balance between biodegradability and performance remains a challenge
According to Matt Thwaites, VP and GM of Cirql, a subsidiary of the US-based insole specialist OrthoLite that produces sustainable materials solutions for the global footwear industry, the balance between biodegradability and performance remains a big challenge in the quest for genuinely compostable shoes. “Products need hydrolysis to compost, but this cannot happen until the end of life,” he told Shoe Intelligence.
In other words, producers need materials that compost – but only at the right time, without running any risk that products might biodegrade while still in use. On the other hand, the more durable and performative the materials are, the harder it tends to be for them to biodegrade. For that reason, most compostable sneakers remain lifestyle models, and producers agree that it might take some more time before the market sees a truly biodegradable high-performance shoe.
The industry has addressed the problem between durability and performance on the one hand and biodegradability on the other by making shoes that can be composted only through industrial processes. This tends to use specific enzymes that attack the material in industrial facilities. Doing that requires that brands and retailers introduce takeback programs, ensuring they put in place processes to receive used shoes from customers and deliver them to industrial composting sites.
That remains one of the missing links for compostable sneakers to gain market share. Some believe that retailers have the responsibility to screen the products they offer to select the more sustainable ones. Still, they must also take responsibility for the composting gathering process and takeback programs.
But, Thwaites believes the growing demand for sustainability is already driving that transition. “Consumers no longer want to throw shoes away, they want to do the right thing, they want a sustainable solution,” he said. “Armed with the facts and a range of innovative sustainable products, consumers will use their influence to demand more options from the brands. And the footwear industry needs to communicate that there are options available today through recyclable, biodegradable and compostable footwear.”
Balena, a startup focusing on compostable biopolymers
Balena is a material science and circular economy startup with offices in Tel Aviv and Milan focusing on compostable biopolymers in the footwear industry. It was founded by its current CEO, David Roubach, in 2020 with the idea of launching a brand that could introduce true circularity in fashion.
“David did some research, and he found that there wasn’t a biodegradable material offering performance,” explains Yael Joyce Vantu, the chief product officer. She noted that several compostable biopolymers were available to producers at the time, but none held up to the materials they tried to replace in terms of performance. “So we thought that maybe we had to create a circular material first.”
Balena partnered with a polymer laboratory in Israel to develop its first fully compostable plastic elastomer that, unlike many biodegradable materials, does not yellow in a few months and offers high durability in terms of grip and resistance to abrasion.
In late 2022, to gain a foothold in the industry, Balena manufactured 1,000 pairs of compostable slides as a proof of concept, managing everything from the material to design, manufacturing, packaging and shipping. It has also produced a biodegradable lifestyle sneaker through direct injection in the upper without using glue as proof of concept. In February 2024, Balena announced joining forces with the Portuguese sole brand For Ever to produce compostable soles with its materials.
Balena has experimented with manufacturing through 3D printing and injection molding, but Vantu says the company is “very focused” on injection molding and only experimenting with 3D printing. “Injection will be the way to go because it’s fast and cheap, has good resolution in the finish of the products,” she said. 3D printing offers fewer design constraints, flexibility and bespoke fitted products for customers but remains a more expensive and lengthy process.
Balena currently offers three materials to partners:
- BioCir flex, a durable and injectable TPU-like (thermoplastic polyurethane) material that the company
- BioCirX, a rigid material based on PHA and bacteria fermentation, is designed to be fully compostable but durable with regards to hits and impact and for use in buckles, buttons and toy blocks.
- BioCir flex 3D, used as filaments and pellets for 3D printing.
Vantu pointed out the company was also working on a foam for the footwear industry based on BioCirFlex, and was looking to improve the material enough to use it for performance shoes.
To prove to brands that its materials are truly compostable, Balena partners with industrial composting facilities in Europe and the US, taking its products there so that the sites can test if they decompose and that the products don’t interfere with their recipe. Balena doesn’t manage the process, but if the testing goes well, the company sets up partnerships with the sites to offer brands a possible solution if they decide to start a takeback program.
In 2023, the company made 80 percent of its sales to the footwear industry and 20 percent to the automotive industry, but Vantu said it was set to expand to other sectors, too. “We want to replace plastics,” she explains. “We are starting with shoes, but the materials could also apply to many other industries.”
Fruitleather, a provider of leather alternatives made from mango skins
Fruitleather is a Dutch material manufacturer based in Rotterdam. It focuses on producing leather alternatives made with the skins of discarded mangos.
While leather is not as unsustainable as the plastic-based materials used in sneakers because it is largely the by-product of the meat industry, the cleaning process of leather materials alone produces millions of kilograms of CO2 every year. Vegan leather is often made with plastic.
Designers Koen Meerkerk and Hugo de Boon had the idea to turn discarded food into an alternative material for the fashion industry in 2015 after they graduated from the Willem de Kooning Academy in Rotterdam and tried to come up with a way to turn discarded food into an alternative material for the fashion industry.
After experimenting with several types of fruit, including watermelons, they found that mangoes were easier to work with and offered the most potential for producing leather-like materials. More than half of the mangos in Europe are imported or traded by the Netherlands, often through the port of Rotterdam. The country discards some 12 percent of them.
After Fruitleather collects the discarded mangos, they are inserted into a machine that destones them and then crushes them into a pulp. The company adds several additives, then pours the pulp into baking trays, smoothed out to create cream-colored layers with even thickness. The layers go into a dehydrator overnight, and the color changes to brown for Palmer mangos and black for Keitt mangos. Finally, the layers go to a leather finishing plant, where they are coated in a protective glaze to make them more durable and water repellent, then inserted in an embossing machine to make the material look like genuine leather.
Recycled discarded mangoes make up 76 percent of the end product, with organic cotton accounting for 14 percent and water-based polyurethane making up the remaining 10 percent.
Fruitleather’s production remains small scale. The company currently produces some 200 square metres of material per month, which would be enough to make some 625 pairs of shoes.
Fruitleather’s material can be used in the footwear industry, but also in fashion accessories, upholstery, and furniture.
Cirql, proposes a compostable foam for footwear
Cirql is a subsidiary of OrthoLite, an insole and footwear materials brand headquartered in Ho Chi Minh City, Vietnam. One of its innovations is a patented foam technology solution for the footwear industry that is industrially compostable, recyclable and biodegradable.
Unlike the conventional foaming methods commonly used, the material is entirely free from traditional plastics and forever pollutants and offers an alternative to conventional plastics typically used for midsoles, such as EVA (ethyl vinyl acetate), which is petroleum-based and therefore not biodegradable.
Cirql’s range is based on a plant-derived biopolymer plus synthetic biodegradable materials that are expanded using nitrogen gas during a chemical-free foaming process to create performance foam.
The material can be returned to the production cycle through low-energy, advanced chemical recycling to help keep materials in use or returned to nature as fully compostable through industrial composting processors.
The caveat with Cirql is that the business produces a fully compostable midsole. However, for it to be composted, it would first need to be extracted from the shoe unless all the other components were also compostable.
To produce the material, Cirql partnered with Novamont, an Italy-based B-Corp manufacturer of bioplastics and biochemicals.
“We believe that our midsole foam innovations bond to all outsoles on the market today, and we will work with footwear brands to look at all of their outsole options,” explains Matt Thwaites, the vice president and general manager of Cirql.
Thwaites also said that the development process was not without challenges and setbacks, including experiments with hydrolysis. Another challenge was adapting processes and materials to match the traditional standards for testing midsoles, which he said are designed for existing materials that are not recyclable or compostable.
In April 2024, Cirql also announced its new Cirql rTPU30, a comfort midsole foam fully recyclable and made with 30 percent post-consumer recycled TPU.
