You take it out and put it in the bin, MayBe70. It goes to landfill, which is not ideal, but at least it doesn't go into the sea and end up in our food.
I got my guppy bag from Natural Collection a while ago and have used it for washing my e-cloths, but haven't had massive amounts of plastic to throw away, it must be said.
I'm another who will not buy any more fleeces, and I do prefer knitting with pure wool rather than acrylic or nylon, unless it's for a DGC who is allergic to wool
. Why does 'baby wool' consist of plastic? I know, it's because it washes, but if a baby's finger gets trapped in a hole in a woollen garment, it's much less likely to have a serious injury than if it happens with a plastic one.