By this point, we’re all pretty familiar with the basics of recycling: You separate cans, glass and plastic into bins, and they’re carted off to be transformed back into their most basic elements.
Some things, like shoes, are more difficult to recycle, however. Whether they’re heels or hiking boots, chances are most of us have worn a pair of shoes past the point of being able to repair them or donate them to a thrift shop. It seems so wasteful to just toss them in the trash, but the local recycling service certainly won’t take them in the curbside bin. So what are we to do?
What makes shoe recycling difficult is that they’re made of a combination of vastly different materials. Unlike glass, which can just be melted down and formed into new glass objects, a shoe can be made of up to 40 different materials, including leather, vinyl, rubber, metal, glue, and natural and synthetic fabrics.
Separating what can be repurposed from what can’t is a time consuming process, that up until recently was too expensive to be worthwhile. But a new system developed by scientists at Loughborough University in the UK could change all of that.
After 10 long years of research, the University’s Innovative Manufacturing and Construction Research Centre has successfully tested what could be ”the world’s first comprehensive system for separating and recovering useful materials from old footwear.”
Here‘s how it works:
1. Shoes are sorted by type – running shoes, heels, boots, etc. — to expedite processing.
2. Any metal components, such as buckles or the eyelets around shoelace holes, are removed by hand.
3. Then, the shoes are mechanically shredded and granulated, reducing each pair to fragments no bigger than 4 millimeters.
4. Three custom-designed, air-based technologies — cyclonic separation, zigzag separation and vibrating tables — then allow for automatic separation of reuseable materials, based on how heavy they are. “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,” explains a University press release.
When they come out the other end, shoes have been reduced to neat little piles of leather, foams, rubber and other materials.
According to the scientists, the recovered leather can be reformed to produce bonded leather sheets. Some reclaimed rubber can be used as a running track or playground surfacing product, while finely ground rubber can be put back into new shoe soles, achieving so-called ‘closed loop’ recycling. Recycled foams can be used in underlay material for laminate floors and carpets, and mixed textiles and other lighter residues could be as insulation material for buildings.
In addition, ”The team has already developed a computerized tool that advises footwear designers on materials selection and helps them explore whether particular combinations of materials would make recycling harder or easier. The more similar two materials are in density, the harder it is to separate granules made of them, driving up the cost of recycling,” explains the team.
The breakthrough could lead to enormous environmental benefits as 95 percent of the 20 billion pairs of shoes produced globally end up in the landfill each year.
Image via Thinkstock
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