This may be the solution you’re looking for
- Make sure the pressure has all been released
- Lay canister on the counter with a towel underneath (or something to help keep it from sliding around). Or, place upside down in a stable container that won’t break or slide.
- Use church key to puncture the bottom. (Additional leverage may be required)
Because this question intrigued me, I decided to follow up on it once I had an empty container to work with.
The “church key” can opener would probably work for someone with a bit more strength than me (I’m getting closer to little old lady muscles daily), but I was able to get a nice divot.
You can see from the photos above that I was able to remove the bottom of the canister. It took several revolutions around with a can opener, each one cutting a little deeper.
Before beginning, I did make sure there was no pressure left in the container.
At no time did this process feel unsafe.