My solution is similar to blackswanwood's above- I have a glass jam jar, with a slot cut in the lid for all my old blades. I put any old bladses- stanley, snap-off, razor blades etc. in there. When it's full I empty into an old steel can (clean paint cans are ideal), seal down the top and put it in my recycling bin for collection. I try to avoid visiting our local "civic amenity" as it's called, so any and all metal recyclables are stripped down and cut up, if needed, so they'll fit in the bin. Medical sharps are a biohazard so I wouldn't do that with them, but otherwise metal blades, once safely packed, are just another piece of raw material that's going back into the recycling stream to be used again.