What exactly qualifies as a “sustainable” shoe? If you find yourself stumped by that question, you’re not alone.

Amid the heightened awareness and interest in eco-friendly fashion — particularly among Gen Z and millennial consumers — companies are increasingly marketing their products as sustainable, basing their claims on an array of ingredients and processes.

Some tout their materials, which might be organic, recycled or bio-based (originating from plants rather than petroleum). Their shoes might be vegan or made with fair labor. They might support regenerative farming, fund tree plantings or have a takeback program.

The qualifications for using the term “sustainable” is still quite vague, which creates confusion at the consumer level and for those in the industry making and selling these products.

And while there is existing and proposed legislation aimed at clarifying product labeling and marketing, the footwear industry currently has no set standard. (Though any “green claims” withstanding will have to scientifically prove themselves, per the European Union’s directive proposed in March.)

“This reminds me a lot of shoe sizes, like every brand’s shoes don’t fit the same way,” said Andy Polk, SVP of the Footwear Distributors and Retailers of America. “For consumers, it’s just another frustration, trying to figure out the comfort, fit, feel and now sustainability.”

In 2021, the FDRA created a shoe sustainability guide about environmentally preferred materials (EPMs) — to provide industry leaders with benchmarks and goals to aid in their efforts to reduce their companies’ environmental impacts.

The trade association worked with sourcing and sustainability experts at companies including Caleres, Allbirds, Nike and Material Exchange to develop the guide.

“The goal was to create standards that we can all follow to grow as an industry with certifications we trust,” said Dan Friedman, chief sourcing officer at Caleres.

FDRA’s guide offers minimum and advanced “Green North Star” targets for footwear components, including leather, man-made fibers, foam, natural wool, natural rubber and bio materials. Polk said it has already helped many companies increase their usage of EPMs in manufacturing and to align their teams around stated thresholds or standards.

But following those guidelines is not required. Also, it doesn’t necessarily solve brands’ problem of how to clearly communicate their sustainable stance to consumers. And getting that part wrong has serious ramifications.

Last year, for instance, both Walmart and Kohl’s were respectively fined $2.5 million and $3 million in civil penalties by the Federal Trade Commission, following allegations that they “falsely marketed dozens of rayon textile products as bamboo.”

Meanwhile, H&M was hit with multiple lawsuits last year accusing the fast fashion company of “greenwashing” the sustainability aspects of its apparel. The retailer had based its claims on calculations from the Higg Materials Sustainability Index, which has since been highly criticized and dropped by many fashion organizations, including H&M.

Beyond legal action, Polk said there are other risks for companies caught overstating their green features, including receiving bad press and losing brand loyalty, which could impact retail and financial partnerships.

So what’s a well-meaning, eco-minded footwear company to do?

For now, they are charting their own paths, developing guidelines based on a range of metrics meant to make clear for internal teams — and consumers — where a product stands in terms of its environmental attributes.

One approach that is widely utilized by shoemakers is to use weight as a central measurement.

Cole Haan, for instance has set a threshold that any Cole Haan product labeled “sustainable” must contain — at minimum — 25% naturally derived or recycled content by weight.

The designation is part of the brand’s sustainable mission, dubbed Change Forward, which has a goal to “better itself and the world around it” by replacing many of its shoe components with eco-friendly materials to reduce waste in the supply chain.

David Maddocks, brand president of Cole Haan, noted that some products in its collection will exceed that percentage, but the 25% marker gives customers a base of understanding. “There’s a lot of confusion around sustainability, which is why we landed on a very simple, communicable threshold that people can rely on,” he said.

The brand kickstarted its Change Forward program in February 2022 with the Generation Zerøgrand II, featuring an outsole made with its patented Flower Foam (consisting of 25% dandelion rubber). In the year since, it has incorporated Flower Foam into several existing silhouettes and launching new styles, including a running sneaker, a golf shoe and the Generation Zerøgrand II SQL, which debuts this month.

Experts note that using weight to communicate environmental bonafides has its advantages, in that it is straightforward and easier to adopt. But it also has shortcomings.

Stuart Jenkins, CEO and founder of Blumaka, a company that specializes in recycling foam waste into new insoles and midsoles, said, “If you’re measuring the weight of recycled foam as your recycled content, why is using recycled heavy foam better for the planet than light foam?”

Another, somewhat more-complex way to measure is based on carbon footprint — a system used by brands like Allbirds.

Last month, as the brand revealed its first net zero carbon shoe, co-founder and co-CEO Tim Brown explained that Allbirds uses carbon emissions as its key measurement because it believes that concept is universally understood.

“We label every product with kilograms of carbon that are emitted in production in the same way that calories are on food,” Brown said. “Calories don’t represent everything about a healthy diet, nor does carbon [with sustainability], but it’s the one thing that connects me to you, New Zealand to America, the footwear industry to the transport industry, and allows us to compare apples to apples. We believe it’s the future of how we’ll measure impact and inform consumers to make better decisions.”