Once all of the fuel in a recyclable canister has been burned off, you can punch a hole into the side or bottom of the empty canister and dispose of it at an appropriate disposal site or facility. Extreme caution must be exercised when disposing of or recycling a gas canister, as any pressurized fuel left in the container could lead to injury or an explosion.
Fuel canisters contain pressurized gas that is most often used in stove or grill operation. Lightweight butane canisters often used in backpacking or camping can often be crushed and recycled at a recycling facility. Heavy-duty propane canisters are not recyclable.
Some companies manufacture refillable bottles or canisters with a self-puncturing option for easy disposal.
Before punching a hole in canister, it is vitally important to ensure that all the fuel has been removed by hooking the tank to a stove or heater and allowing the fuel to completely burn away.
As an added measure of security, Outdoors.org suggests putting a rag between the canister and the puncturing implement to prevent any sparking. The punctured canister should be labeled as empty or dented to show that it is safe to be processed by a disposal facility.