Best way is to run the gas out if not already done. Morning coffee by campstove instead of electric jug is one way. Then puncture the can. Do this outside well away from ignition sources. Then you can dispose or recycle as you wish. If your kerbside recycling will accept steel then thats the best option but make sure the puncture is obvious
Another option is to drop off non-empty canisters at hostels (call first obviously). Many have a hiker box. We always try to score free canisters from a hostel if we're staying at one, before buying a new one.
This post has been edited by the author on 7 April 2018 at 14:28.