i used to replace my old blades in the plastic container they came in- tape it all over with duct tape-and put them in the trash- then i found out that our hardware store would take them ( as part of their recycling program- along with batteries and a few other things that are hard to get rid of.) so now i place them in a tin-with a lid and when i am heading to the hardware for something i take them along- i don't know what they do with them- and don't care-even if they sharpen them & sell them- it's ok with me- i don't have to worry about disposal- or anyone getting hurt.
as for the sharpeners- i've had one for a number of years- to me it was more dangerous than changing them tends to be- i hate it- for me it is worth it to buy new ones- and one of those items i always add to my Christmas list- hubby usually buys me a couple of each size for stocking stuffers.
