Polyester is derived from crude oil and polyethylene terephthalate, or PET.
Because polyester is made of PET, outside of lab conditions, it does not biodegrade, but it does decompose by slowly breaking down into smaller and smaller pieces, becoming micro plastics. Micro plastics, or microfibers (when broken off of synthetic fabrics) have polluted our water and food chain, affecting our ecosystems.
While upcycling, using, and reducing our plastic waste is a fantastic reason to use recycled plastics, it can take nine clear plastic water bottles to make one T-shirt, 25 plastic bottles to make one pair of leggings, and 12 bottles for Polo shirt.
Recycled polyester is an effective solution to recycle and reuse PET plastic that would otherwise not biodegrade, it requires less energy to produce and there is a lot of PET to use to recycle.
Because of that, and more, we use all kind of recycle plastic yarn, from plastic bottles to fishing nets.