When it comes to choosing a reusable shopping bag, what’s the greenest of them all? Turns out the thin (and durable) bags made entirely from nylon or polyester lead the pack. These bags are convenient because they fold up into small squares and they are machine washable, keeping them sanitary. If you invest in a nylon or polyester reusable bag, be sure to keep reusing it. It takes about 11 uses before you begin recouping the environmental savings of not using disposable plastic shopping bags.