The subject of carbonating beer with dry ice comes up pretty often, and I got a shipment of food today with a BIG block of the stuff, so I decided to experiment a little.
On the bright side, it worked!
Unfortunately, it's probably a very dangerous way to carbonate beer (either in bottles or kegs). As many have pointed out, dry ice sublimates rapidly in liquid, creating large bubbles that do not readily dissolve into solution. This causes a pressure buildup in the head space that could VERY likely lead to bottle (or keg) bombs. The pressure buildup is so rapid that a Corny keg's pressure relief valve would probably be overwhelmed. The only way to decrease the pressure is to violently shake the vessel, causing the gas to be absorbed into solution. I doubt you could successfully achieve that with a 5 gallon keg, and it's impractical to shake every bottle of beer you fill.
Here's the video I made that shows a successful trial with a plastic soda bottle. Note that ALL of the dry ice that I put into the bottle was used up, but if I hadn't shaken the bottle, it likely would've exploded.
http://www.youtube.com/watch?v=t-MBJlBHRkE
I'm sure the ensuing discussion will debate more ways of doing this successfully, but my official stance is:
DON'T USE DRY ICE FOR CARBONATION!!!
Priming sugar and gas cylinder refills are cheap. Using dry ice in closed containers is always a bad idea.
Oh, and if you're wondering why the instructions in the video are so explicit...it's because I know a few of you are going to try this at home even though I said not to. I'd rather give you enough info not to hurt yourself than leave things unexplained.
Dry Ice Carbonation (video)
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