Nowadays, polyester can be recycled, plastic bottle will be collected and remake into other things or fiber for weaving into fabric and then make into garment. If those polyester garments become too old and not fashionable, you can decide to donate to other poor countries, but if it is ruined or broken, how can these garments can be recycled? It seems it is still very difficult even it is 100% polyester. It is better to leave this question to scientist to develop biodegradable polyester.