This is from another, non-beer forum I frequent, the guy started with 5l on Heinekin:
So, now I am wondering how the mini-kegs work. Some chemical reaction to make CO2, that leaves charcoal? Some other technology that we need to know?
"I finally cut all the way around and lifted the top off. There was a plastic pick-up tube attached to the tap fitting on top (duh) and a White cylinder glued to the bottom. I pulled that off easily enough. It looked like one of those Ronsol butane canisters, and it was about the same size, too. The can had something in it that made noise when I shook it. I sounded like it was full of gravel. I figured I'd need to open it to find out what that was. I was going to just pull off the cap assembly, but I was afraid there might be some residual pressure, so I needed to figure out a way to depressurize the thing.
I decided a pellet gun would do the trick (heh heh heh)
Well, there was no pressure in there at all, but what was in there was very surprising. Charcoal. Hmmm? Anyone here in the liquified gas industry can explain what that would be for?
Oh, and the cap was a rather ingenius balanced regulator made of plastic to maintain the proper pressure.
All in all, a very clever and useful bit of engineering. Certainly this will have a bigger impact on all of our lives than the Segway personal scooter.
But seriously, why the charcoal?"
So, now I am wondering how the mini-kegs work. Some chemical reaction to make CO2, that leaves charcoal? Some other technology that we need to know?