Footwear recycling gets a kick-start
23/10/2013
It is being touted as the world’s first comprehensive system for separating and recovering useful materials from old footwear, and has been successfully trialled.
The system is able to granulate and segregate leather, plastic foams and rubber so that they can be reused in products including rubber playground surfacing to new shoes.
It was developed at the University’s Innovative Manufacturing and Construction Research Centre (IMCRC), whose 10 year research programme was funded by the Engineering and Physical Sciences Research Council (EPSRC).
“Footwear is incredibly difficult to recycle as it can contain up to 40 different types of material, many of which are stitched or glued together,” said Professor Shahin Rahimifard, who led the project. “In our process, the first, manual step is to pre-sort shoes into broad types, such as trainers, and to recover metals, such as eyelets. Next the shoes are automatically shredded and granulated, with the granules automatically separated into four waste streams: leather, foams, rubber and other material.”
The shoes are turned into 3-4mm fragments using a granulator. Low-cost air-based technologies developed by the project then separate the materials by exploiting their different sizes and weights: an air-cascade separator first removes lighter textile particles and other fine leather and foam residues by blowing them away from heavier granules; then a series of vibrating air-tables separate rubber from foam and leather by stratifying the granulated materials, with lighter granules ending up on top of heavier ones.
With EPSRC funding, collaboration is also under way with major footwear manufacturers to explore how shoes could be designed differently to make them easier to recycle. The team is also talking to a recycling company interested in incorporating the process into its operations.
The university estimates 95% of the 20 billion pairs of shoes produced globally each year end up in landfill.
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