How much recycled rubber can go in a sole before it stops working
We ran the trials. There is a point where recycled content is free, and a point past it where you are selling someone a shoe that wears out.
Ground-up rubber from our own offcuts goes back into a casual or training outsole at a fifth of the mix without any measurable loss. It saves material, it keeps waste out of the ground, and there is no reason not to do it.
Where it stops
Push it further and the sole starts wearing through. On a casual shoe that is survivable. On a work boot it is a different product, and the wearer notices inside one winter.
A buyer once asked us to go well beyond that because a retailer had set a target. We could have shipped it. The number would have been accurate and the boot would have worn out in a season.
A shoe that wears out twice as fast is not the greener option, whatever the paperwork says.
We said no, showed the test data and proposed a lower share with a longer-wearing compound instead. That is what shipped.
Written by the Lab Multi team. For press enquiries or to speak to the people behind this work, contact info@labmulti.com.
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Send a spec, a sketch or a shoe you already sell. We will take it from there.