Developing a sole is something of an art form. So when we set out to create a sole that brings together sustainability, style, and performance, we needed to find a manufacturer who is a master of their craft. Our search led us to Samuele, the creator behind our Koio ReCycled™ [68 TPU] outsole.

Samuele was born into a family of fine footwear artisans in Marche, Italy, where “everything was connected to [the] shoe business.” Both of Samuele’s parents worked in shoe production, so he says “the smell of leather—it comes in your blood, your DNA.” It’s only natural, then, that he went on to carve out his own niche in the industry—as a sole-maker.

Ahead of Earth Day, Samuele walked us through the production of our Koio ReCycled™ [68 TPU] outsole.

STEP 1: GATHER DISCARDED MATERIALS

Sixty-eight percent of the TPU used to make the Koio ReCycled™ [68 TPU] outsole comes from excess, pre-consumer TPU. Some of these recycled components are sourced from discarded or leftover soles from previous production processes. 

Samuele says the soles pictured on the left were discarded because “maybe the logo was not okay, there were spots of dust, or […] color that doesn’t match our color card.” The “carrots” shown on the right are left over from previous sole production processes as well. They’re the excess material left behind in the injection channels of the mold—think of them like spillover dough that comes out of your waffle iron. Had Samuele not gathered these discarded soles and ‘carrots,’ they likely would’ve been sent to a landfill.

STEP 2: GRANULATE & MIX RECYCLED TPU WITH NEW TPU

“We take the [discarded] soles and we […] granulate [them].” Using innovative machinery, the excess soles are ground into small, pellet-like spheres.

The recycled TPU is then mixed with fresh TPU to create a new compound. Samuele says it’s important to use a mixture of both, because recycled TPU feels more like “a plastic than a rubber”, while the virgin material TPU has “a gummy touch.” By mixing the two, we can create a durable yet bouncy outsole. 

Samuele created the “recipe” for these soles (68% recycled TPU, 32% virgin TPU) through trial and error. ”You have to change maybe 3%, maybe 5%” of the makeup, altering the ratio of recycled and virgin materials until it’s just right.

STEP 3: INJECT THE MIXTURE INTO THE MOLD

Once they’re mixed, the recycled and virgin TPU are injected into the mold.

STEP 4: COMPLETION

The sole is removed from the mold. At this point, it’s ready to be attached to the upper!

When it comes to sustainable soles, Samuele says the Koio ReCycled™ sole is one of “the only one[s] you can trust.” Why? Because we can prove how much of the makeup is recycled, and why we used a combination of both recycled and new materials to create it. In other words, we can really measure what makes it sustainable.