@Minara - I looked into this once myself. According to my local recycler you have to puncture the cannister and then it can be recycled as "mixed metal".
There are a couple different adapters you can get. One will allow you to refill a canister from another canister. Basically this allows you to take a few different “almost empty” canisters and transfer their contents into one so you’re not wasting fuel
the second adapter allows you to refill from a larger ISO bottle.
Either way, though, you still end up with empty canisters. Refilling is more for economy than environment. Not a bad idea and if you get a large bottle to refill the smaller canisters, you do end up with fewer items heading to recycling. You just won’t reduce that much.