Running shoes come at a surprisingly high environmental cost, according to a new study released by MIT. The production of each pair of sneakers may produce 30 pounds of carbon dioxide—the equivalent emissions of powering a 100-watt light bulb for one week.
The research team was surprised by the findings, as other “less advanced” products—or, generally, items that don’t qualify as electronics—do not create the same amount of waste. The reason for the divergence, the researchers discovered, was that the majority of pollution from running shoes results from the manufacturing process, rather than material acquisition. Many sneakers are made at plants in China, where coal is the primary energy source.
Furthermore, the complexity of running shoes is also at fault. The creation of each sneaker requires 360 distinct steps and 65 different parts, according to the scientists.
“In general, we found that if you have a product that has a relatively high number of parts and process steps, and that is relatively light [weight], then you want to make sure you don’t overlook manufacturing,” Randolph Kirchain, principal research scientist in MIT’s Materials Systems Laboratory, said in the MIT press release.
Luckily, the scientists identified numerous ways to limit the emissions: scraps can be recycled, parts of the shoe can be combined to cut back on energy-intensive steps such as welding, and designs can be printed directly onto the shoe rather than created on a separate piece of material.
“Understanding environmental footprint is resource intensive,” Kirchain says. “The key is, you need to put your analytical effort into the areas that matter.”