Salomon makes millions of shoes every year. But it's trying to develop a way to make those shoes more sustainable — the company's new concept shoe is made entirely out of one material, TPU. It can be ground down and combined with new TPU to form a brand new ski boot shell. Salomon expects this shoe to be available in 2021. Salomon isn't the only company developing a sustainable sneaker. Adidas' Futurecraft Loop shoe is also made from TPU. Adidas hopes to turn used shoes into a brand new pair.