As Roger says, throw 'em in the recycling bin. If you feel like you should do more, take the spool out & put that in the plastics bin.
Golly, I'm glad I've use FILCAs. I save the world OUNCES of scrap over a lifetime. Leitz was way ahead of his time, no? No crappy velvet light trap to catch sharp rocks to drag across your film, either. Look at me.....I've gone GREEN :>)