Gas is our top choice for a convenience camping fuel - it's fast, easy to use and in the UK at least, easy to obtain, - there's a downside to all that ease of use though, and that's how you recycle the gas canister once it's empty.
Essentially butane/propane mix camping gas cans are just an aluminium and steel container with a self-sealing valve fitted. The problem of course is that they're filled with highly inflammable gas, which of course, is why you bought it in the first place.
The cans are also usually furnished with dire 'Do Not Puncture This Can' warnings. The trouble is that even when the canister is effectively useless for cooking, it can still contain small quantities of gas and recyclers won't accept them.
There is a way round it though. You can empty the can, then visibly puncture it and, preferably, crush it too. One option is to use a knife to puncture it or a screwdriver or awl with a hammer, but for a really neat solution, check out the CrunchIt from JetBoil.
It's a neat little dedicated gas can killing tool. Disappointingly it doesn't actually crunch the can into a compacted mass of shredded metal. Instead it's a neat way of visibly puncturing the can. First you completely empty the can using a screw-on stove.
Next, when the canister appears to be empty, you screw the centre cap of the CrunchIt onto the valve which will release any remaining gas - sniff that Butane guys - finally use hand pressure to force the pointy bit of the CrunchIt into the top of the can in four five places leaving a pattern of visible holes and a bad smell.
Finally, if you're feeing really keen, stomp the can into a squishy, shapeless, and clearly empty pulp. Job done. You can now simply chuck your dead gas canister in with all your other metallic recyling stuff.
Hot Tip - if you do buy a CrunchIt, do remember to remove the orange plastic cover before puncturing the can or it won't work. And if you want to snigger, note that the screw-on guide cap is labelled 'Orifice Wrench'. Sorry...
The CrunchIt sells for about a fiver. More info at www.jetboil.com.