Fermenting in a Corny Keg

Trying something new with my classic oatmeal stout recipe. This time I wanted to start experimenting with a closed fermentation set up. I created the closed system by working entirely in a Corny Keg for fermentation.

Most of us understand that oxygen post fermentation is an enemy of beer. Even in a dark stout too much oxygen getting into the finished beer leads shortened shelf life. I have used a specialized carboy cap with two inlets to push beer out of a carboy and into a keg before. The only real problem with that method is that putting pressure on a glass carboy is a bad idea. Even if the pressure is low, you can’t be too safe with glass carboys.

I have read of people using corny kegs to ferment in and I wanted to give it a try. I already had one keg that I trimmed 2 inches off the dip tube. So I thought that keg would be a perfect candidate for a fermentor. Post fermentation that short dip tube would hopefully be above the yeast trub and I could transfer clear beer into a new keg.

To ensure the system was clear of oxygen I first filled the receiving keg with sanitizer all the way to the top. I then pushed the sanitizer out with CO2. That left me a completely purged keg. I have never been to sure how well pressurizing and burping an empty keg works to get rid of the CO2. But doing it this way, I am sure much more oxygen was gone. To transfer the beer I hooked the CO2 up to the fermentation keg and I used a black to black connection to go from beverage dip tube to beverage dip tube. I used <10PSI of pressure to push the beer from the fermentation keg and into the serving keg. I could tell as the beer passed through the short tubing between black connectors that it was pretty clear of yeast trub. To deal with blow off CO2 and to keep things moving I used a grey connector with a barbed fitting. I attached one long piece of tubing and put it into a pitcher of sanitizer, essentially a big airlock...keeping the system closed. I was pretty happy with this process. Fermenting in a corny keg went very well and I like that I never had to get out the auto siphon and racking equipment. I think I need to run a few more batches through this process to really get a feel for whether I like it despite some drawbacks. The first drawback was the limited head space. I fermented only 4.25 gallons but still had a pretty good blow off during fermentation. I wonder if some foam control would help with that issue. Second was that I know had about 4 gallons of beer in the final keg vs. 5. This is a bit of a detractor, but I normally don't drink all the beer I brew before I need to empty a keg for a newer/fresher batch of beer. Maybe I'll experience less waste by only having 4 gallons in the fridge. A few batches will tell me if this is going to be a really issue. I figure if total volume is an issue I could ferment 3 gallons in two kegs then combine them into the same serving keg. This might actually get rid of the headspace issue too! Let us know if you've had experience using corny kegs as fermentors. BREW ON!!