I recycle my empty printer cartridges (and cellphones) by sending them to a recycle plant in Franklin. I got a stack of envelopes once at the Xeriscape expo. The recycle place refills and resells them and I am okay with that, as long as they do not go into the environment and polute.
I just received about 200 new envelopes from them, as I had ran out. So, if you are in the habit of throwing away your old cartridges and if you want some, I will bring them the Explora Monday at 1pm or to the PE classes at the UNM Thursdays at 08.30 Ask me for them.
The envelopes do not need postage. Just stick in the cartridge/cellphone and put it in the mail, that's all.