It is down-cycled and turned into lesser things, while a glass bottle can be a glass bottle again or can be used again -- a plastic bottle can never be a plastic bottle again.
当一个塑料瓶 可以被重制成一个塑料瓶， 或者重被使用时， 正是被降级回收，使得塑料瓶被制成小塑料体，使得一个塑料瓶不再被制成塑料瓶回收利用。