What’s the Carbon Footprint of Your Shoes?

Andy Polk has spent the last year trying to put a number on the environmental impact of a shoe.

It wasn’t how he’d expected to spend the time. The executive director of the Footwear Innovation Foundation, a newly launched nonprofit think tank backed by the industry, initially set out to explore what innovations might help brands and manufacturers reduce factory-level pollution. But the first hurdle he ran across was a stunning lack of information to simply identify the scope and scale of the problem.

Most of the available estimates of the industry’s overall footprint had been extrapolated from studies focussed on apparel and textiles, which have very different supply chains to the footwear sector. The most common reference point for the impact associated with an individual pair of shoes was a study focussed on running sneakers conducted by the Massachusetts Institute of Technology (MIT) more than a decade ago. In other words, the industry was relying on outdated and inconsistent data to shape its approach to a fiendishly tricky challenge.

Polk switched tack. Instead of identifying solutions to footwear’s sustainability issue, he set out to try and build a more up-to-date picture of the industry’s carbon footprint. It’s a fraught task, plagued by limited data and controversies around methodologies for impact assessment.

Polk’s findings, published in a report on Monday, peg footwear’s environmental impact much lower than previous estimates, but also reveal gaping data gaps that still need to be addressed. He’s not expecting anyone to take the numbers at face value. In fact, he’s counting on the opposite, hoping it will spur more research and better insights in the future.

“We’re not trying to say this is the end all, be all number, but it’s a new baseline,” said Polk. “We’re not trying to boil the ocean; we’re trying to find the right places and spots and right people to act.”

The Data Gap

Like Polk, Yuly Fuentes-Medel has spent a long time puzzling over how to measure the footwear industry’s environmental impact. The programme director at the MIT Climate Project launched the Footwear Collective with brands including On, Crocs and New Balance in late 2023 partly to try and tackle the issue.

Right now, “that data doesn’t exist,” said Fuentes-Medel.

While the apparel industry’s first attempt to tally its environmental impact dates back more than two decades to the formation of the Sustainable Apparel Coalition (now known as Cascale) in 2010, efforts to establish similar initiatives focussed on footwear are still nascent.

That’s partly because shoes are much more complicated than clothes. A typical pair is made up of around 60 different materials and components and can go through more than 200 different manufacturing processes. Compare that to a T-shirt, which at its most complex is likely to be a blend of cotton and one other fabric and more often than not only needs to be sewn together and dyed before it hits shop floors.

“Because of the complexity of the product, it’s very difficult to gather accurate information within a reasonable timeframe that’s also business viable,” said Sophie van Kol, innovation manager at fashion innovation platform Fashion for Good. “Apparel was low-hanging fruit because it was simpler to get into first.”

The footwear industry also hasn’t faced as much scrutiny as the wider fashion sector. At least until now. Part of the reason why Footwear Innovation Foundation was set up is that that’s beginning to change: European policymakers are pushing forward with rules that will make fashion and footwear companies provide more information about their environmental impact and do more to address it, and despite the Trump administration’s sustainability pullback, individual US states are also pursuing climate-friendly policies focussed on the wider fashion industry. That leaves the footwear sector with some catching up to do.

“Apparel companies started to invest in research in this way earlier,” said Polk. “There wasn’t really a nudge on the shoe side like there is today.” He would know. Alongside his work with the Footwear Innovation Foundation, Polk is senior vice president at Footwear Distributors and Retailers of America, a trade group that represents the bulk of the industry in the US.

A New Baseline

One of the first things Polk did when he started his year-long quest to update the footwear sector’s environmental baseline was canvas suppliers for primary data on their footprint. What he found confirmed his view that the data badly needed updating. Most of the available analysis is based on the assumption that highly polluting coal-fired boilers are commonly used in production facilities.

This may have been true a decade ago, but based on information Polk gathered from 33 factories in China and Vietnam, it’s not the case anymore. Factories have also become more efficient, reporting much less energy is required to make a pair of shoes today than was assumed in the widely quoted MIT study from 2013, he found.

Next, Polk set out to put a number on the carbon emissions associated with an “average” pair of shoes today. This required a few assumptions, since footwear covers a vast array of products and a pair of flip flops has a very different environmental profile than a pair of knee-high leather boots. Polk trawled trade data and polled the industry for a sense of what would constitute a “typical” shoe, ultimately settling on a basic women’s sneaker.

The imaginary shoe was given detailed production specifications, from the weight and mix of materials required to make it, to its manufacturing location, shipping logistics and sales channels. That data was then fed into the Footwear Impact Calculator, a publicly available tool created by leather testing and technology centre Eurofins BLC with the support of companies within the footwear industry. Its impact calculations are based on a methodology developed by the European Union and rest on a database of environmental assessments powered by life cycle assessment software provider SimaPro.

The shoe’s environmental footprint was nearly seven kilograms of carbon dioxide equivalent across its entire lifecycle, roughly half the impact of the sneaker covered by MIT’s old study. Polk then took both numbers and multiplied them by 23.3 billion — the number of pairs of shoes the World Footwear Yearbook estimates were manufactured in 2023. That gave an estimate for the industry’s total carbon footprint of between 156 million tonnes of carbon dioxide equivalent and 322 million tonnes of carbon dioxide equivalent, comfortably less than 1 percent of the world’s total. Estimates for the fashion sector’s carbon footprint (some of which include footwear too) range from 2 to 10 percent of global emissions.

Polk acknowledged the numbers are still far from perfect. The methodology developed by the EU has been criticised for resting on outdated and limited impact assessments. The study hasn’t been peer reviewed.

At best, the data is still only directional. Footwear covers a vast array of products with very different footprints. For instance, injection-moulded footwear, like Crocs, requires just 0.5 kWh of electricity consumption per pair on average, while making an average pair of boots require more than five kWh per pair, according to Polk’s analysis.

“It’s not going to be a perfect number. … We’re trying to see where are we tacking,” said Polk. “We were just trying to find a new baseline people can work from. … Hopefully it’s a catalyst for more research from universities and academia.”

At least some of that work is already underway. Fuentes-Medel is working on a platform with the Footwear Collective that will use aggregated data from its members to help create new baselines for different types of shoes. She’s hoping to get it off the ground in 2026.