Recapture CO2 once keg is empty

[hiphopperforever]

I tried a search, and maybe used the wrong terminology - found nothing.

Once a soda keg has been emptied of beer, its full of CO2 gas at serving pressure. Is there a way to recapture that CO2, or is it just wasted? I have a three spigot setup, and I guess the individual regulators must have a back flow preventer because I couldn't get the gas to flow from the pressurized empty keg coming out of the kegerator into the new full keg being readied to go into the kegerator. Would a jumper line push some of that CO2 into the fresh keg?
Is it worth bothering? I only have a five pound tank so it seems to empty quickly with the three tap setup and friends that like to drink...

 

[Paps]

I've also wondered how one would go about `harvesting CO2` from the actual fermentation. But like you have found nothing on searches.

 

[helibrewer]

You could use a jumper but then you have a keg tied up as a giant pressurized reservoir. It probably isn't worth it. Bite the bullet and get a 10 pound tank, the fill cost is almost identical for twice the volume.

 

[helibrewer]

I've also wondered how one would go about `harvesting CO2` from the actual fermentation. But like you have found nothing on searches.

That CO2 would need to be scrubbed since there are a lot of volatile compounds being driven off by the CO2 and you wouldn't want to reuse it.

 

[Bobby_M]

Assuming the next on deck beer is similar to the old one, the aroma transfer wouldn't be too unwelcome. However, a keg with 12 psi of gas would basically drop down to 6psi when coupled to another non carbed keg and it would take a pretty long time to equalize to 6. Long story short, without a clean compressor, you can only save half the CO2.

 

[b-boy]

You could use a jumper but then you have a keg tied up as a giant pressurized reservoir. It probably isn't worth it. Bite the bullet and get a 10 pound tank, the fill cost is almost identical for twice the volume.

I can verify this. I just had a 5 lb tank filled for $20 and a 10 lb tank filled for $23. It doesn't make sense to me, but they said the labor to fill the tanks was the same so that accounts for the small $ difference.