I usually just throw it in the garden or in the compost bin. The main reason it's no good anymore is because it breaks down too fine and the garden plants aren't worried about that. if I had identified something particularly nasty in the pot in terms of a fungal infection or whatever I just put it in the bin but regualr repots go back into the gardening system.
My old mix just goes in the compost bin. I don't put it in my worm bin because my mix is still probably too fibrous for worms when I repot and I'm a bit cautious about any residual pesticides in the mix going into the worm bin.
Mine goes in the compost bin. Not sure what a worm bin is, there are worms and bugs in my compost bin helping it compost down.
Sometimes if the plant was sick when removed from the pot I instead put it in the bin that goes to the council for disposal. They compost in a hot fast compost rather than a slow one like you get at home. A hot compost is more likely yo kill anything in it than a slow one.
Hmm.... it won't let me edit that.
They all love actively decomposing material as well. So orchid bark and sphag that's bringing down seemed three perfect fit to me.