Massachusetts Institute of Technology (MIT) researchers from Materials Systems Laboratory recently discovered a typical pair of running shoes generated 30 pounds of carbon dioxide emissions. This is the carbon footprint equivalent to keeping a 100-watt lightbulb on for one week. A small amount of carbon dioxide emissions perhaps but it becomes significant when according to the study, about 25 billion of running shoes are sold worldwide every year. Two-thirds (68%) of the emissions produced by running shoes are thought to stem from the manufacturing processes. The group found much of the carbon impact came from powering manufacturing plants: A significant portion of the world's shoe manufacturers are located in China, where coal is the dominant source of electricity. Coal is also typically used to generate steam or run other processes in the plant itself. A single shoe contains 65 discrete parts that require 360 processing steps for assembly and these materials account for another 29%. Researchers found small, light components such processes are energy-intensive and therefore, carbon-intensive compared with the energy that goes into making shoe materials, such as polyester and polyurethane. Researchers suggest revised manufacturing processes, such as printing directly on a shoe instead of attaching separate pieces, could lower running shoes' carbon footprint. In that regard, some shoe companies are ahead of the researchers, as companies like Nike, New Balance and Adidas, among others, experiment with 3D printing, welding instead of stitching, and other innovative processes that produce shoes in fewer steps.
Cheah L, Ciceri ND, Olivetti E, Matsumura S, Forterre D, Roth R, and Kirchain R 2013 Manufacturing-focused emissions reductions in footwear production Journal of Cleaner Production Volume 44, pp 18–29.