Source of carbon dioxide in kegged beer

Is all the carbon dioxide in a keg of beer the result of fermentation? If not, what would be the other source(s)?

Forced carbonation.

It’s funny. I had a related question i wanted to ask, but I didn’t think it was practical so I didn’t ask. As long as something related is here though. It seems that when I brew beer, especially during the initial fermentation, a whole lot of CO[sub]2[/sub] gets waisted. If i run it through a drier, is there anyway to compress it into a cylinder so I can use it again to bottle with the aforementioned torced carbonation?

Sure. How much you wanna pay for it?

Lets start with money is no object and widdle it down from there.

Probably not worth the time and effort.
disposable CO2 cartriges run $10.50 for 144 grams of CO2 (12 cartridges @ 12g each), or just over 7¢ per gram.

In the long run, a larger system, say a 5# tank, would be even cheaper, but takes more gear to set up. Filling a 5# tank should run you less the 1¢ per gram.

All of the equipment you would need to use a CO2 tank (filled by someone else) you will also need to bottle your own CO2, and that’s just the storage side. That wouldn’t take into account capturing and compressing the CO2.

So the math comes down to: can you capture and compress the CO2 for under a penny a gram?

I understand that it is not worth the money or effort. I just want to know how to do it.

So the companies that bottle the CO2: where do they get their CO2?

Back when I worked at McDonald’s, we had a machine that made our carbonated water. Can’t remember what it was called, though – duplexer? It didn’t use bottled gas as far as I’d ever seen. Any idea how this sucker worked?

Later when I worked at a small, independent pizzeria, our soda fountain used the same gas bottles I use now for my beer.

One way would be cryogenically: capture the gas and cool it to the temperature at which CO[sub]2[/sub] solidifies (-78.5 degrees C). Pick up the resulting bits of dry ice and toss them in a handy container.

For a slightly more practical approach, pressurize the gas to something over 5 atmospheres; when cooled under sufficient pressure, CO[sub]2[/sub] will liquefy. This will make it easy to put in a bottle. If your bottle will withstand something like 800 psi, you’ll have liquid CO[sub]2[/sub] at typical room temperatures (if not, you’ll have an exploded bottle).

Then there’s the low-tech method of piping (hosing,if you will) the generated CO2 into carboy/sixtel/next step vessel to purge oxygen prior to racking/bottling etc.