This is an item I usually throw away in the trash, however, I have become more aware of what I throw away and try to recycle as much as I can.
By the way, they can be washed in the washer with detergent and bleach.
Here are some recycling uses for those old shower curtain liners . . .
In the garden . . . use in place of landscape fabric or in conjunction with newspapers in preparing new raised beds or an area being prepared for paving to prevent weeds from coming up (my favorite use!).
Use in place of drop cloths when painting for easy clean up.
Use as a table cover when working on your crafts.
Make an outdoor table cloth.
Put in the back of the truck, van or trunk of car when hauling stuff around for easy clean up.