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Recycling system developed for old shoes

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October 21, 2013

The raw materials and end products of the recycling process

The raw materials and end products of the recycling process

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Of all the things that we regularly dispose of, you would think that shoes would be one of the most difficult to recycle. Not only are well-used shoes kind of ... gross, but they're also made of a variety of different materials, all of which are joined together. Nonetheless, scientists at Loughborough University in the UK announced last week that they have created and trialled "the world’s first comprehensive system for separating and recovering useful materials from old footwear."

The recycling system was developed at the university's Innovative Manufacturing and Construction Research Centre, and is the end result of a 10-year research program.

The process begins with shoes being manually sorted into broad categories (such as "trainers"), and having metal components such as eyelets removed. They are then automatically shredded and granulated, ending up as tiny fragments. Those fragments are sorted according to material, using three main methods – cyclonic separation, zigzag separation, and vibrating tables.

The shoe-recycling line at the Innovative Manufacturing and Construction Research Centre
The shoe-recycling line at the Innovative Manufacturing and Construction Research Centre

In the cyclonic separation process, a tornado-like vortex of air is created within an enclosed cylindrical chamber. The lightest fragments are picked up by that vortex and carried out of the chamber through an outlet tube in the top, while heavier fragments remain behind on the bottom.

Next, in the zigzag separation process, fragments are fed into the top of an enclosed column, and fall to the bottom by "zig-zagging" back and forth between alternating sloping platforms. Along the way, jets of air blowing in from the sides push the lighter fragments off to other receptacles, allowing only the heavier ones to reach the bottom.

Finally, when mixed fragments are placed on a sieve-like screen built into a vibrating table, the vibrations cause the smaller fragments to fall through the gaps in the screen, with the larger ones remaining on top.

By the time they get to the end of the line, the shoe fragments are sorted into four material types: leather, foam, rubber and other materials. The leather fragments could then be used to create sheets of bonded leather (real leather mixed with synthetic); the foam could go into items such as carpet underlays; the rubber could be used either in playground-surfacing materials or even in the soles of new shoes; and the mixed materials might find use as building insulation.

The university is now working with "major footwear manufacturers" to develop methods of designing footwear that would make it as recycling-friendly as possible. This could include using materials of very different densities, as doing so would make the separation process quicker and thus cheaper.

Alternatively, shoes can also be kept from sitting in landfills for millennia by making them out of compostable materials.

More information on the Loughborough system is available in the slide show below.

Source: Engineering and Physical Sciences Research Council

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
6 Comments

Not sure how they think the can call themselves as being the 'First'. Nike Grind has been doing this for over 20 years. http://www.nikegrind.com

Daniel Shewmaker
22nd October, 2013 @ 08:37 am PDT

Not quite Daniel. The Nike process relies on separating the 3 materials prior to grinding:

"Nike Grind includes three types of raw materials made from recycled athletic shoes and manufacturing byproducts: rubber from the outsole, foam from the midsole and fabric from the upper"

This is fine if the shoe uses discrete materials for each component AND they are easilly seperable prior to grinding. The Loghbrough process seems to deal with the many shoes where this is (ufortunatley) not the case.

Brendan Dunphy
22nd October, 2013 @ 10:01 am PDT

Really? Do people go through shoes in such numbers that this is an issue? Like my dad, most of the shoes I have are 20 years old or older! If they have leather soles, they are considerably older because they can be (and are) resoled! I think that in my entire life, from infant to adulthood I've perhaps thrown away less than 10 pair of shoes...

Ed
22nd October, 2013 @ 01:04 pm PDT

Another great bit of research. However, I would be more pleased if the running & sport shoe makers could be made to use more durable materials for soles and a more durable foam than the crappy EVO foam they mostly currently use. Also, Ed, does not get it. This project is aimed at sport shoes which historically have far shorter service lives than traditional leather shoes.

StWils
24th October, 2013 @ 08:47 am PDT

What are the broad categories such as "trainers" ???

한결김
16th April, 2014 @ 07:14 pm PDT

We waste a lot of leather , and I see that can be recycle, can some tell me the industrial uses for this leather.

gonzo0376
10th September, 2014 @ 04:43 pm PDT
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