Dynamic Crosslinking to Produce Secondary Feedstock from Recycled EVA as a Sustainable Solution for Footwear

Note: This is a follow-on project to 20-01-RR-4029

The U.S. International Trade Administration (ITA) reports that the U.S. imported more than 2.4 billion pairs of shoes in 2022, representing 96% of U.S. footwear demand.  According to the U.S. Environmental Protection Agency, only about 13% of clothing and footwear waste in the U.S. is recycled. The rest either gets incinerated (17%) or landfilled (70%).

For footwear that gets recycled, some materials like the ethylene-vinyl-acetate (EVA) foam used to provide cushioning in midsoles pose a challenge for recyclers. To increase the recycling rate of EVA foams, which is currently 15%, a research team involving Braskem, Massachusetts Institute of Technology, and two shoe companies, Allbirds and Adidas, is developing the first commercially scalable process to recycle the crosslinked EVA scrap generated by shoe midsole manufacturers.

Once developed, this process will allow manufacturers to increase their use of EVA scrap during shoe midsole manufacturing from 15% to 30%, saving 0.5 million metric tons (MMT) of EVA foam annually, decreasing greenhouse gas emissions by .39 MMT per year, and reducing energy use by 26.6 petajoules per year.