As a casual observer of the ongoing LODO discussions, I have come across the spunding topic. I have always done a form of spunding, but I find myself wondering about a further level.
Specifically I’m thinking about connecting a sanitized keg to the fermenter in order to purge the keg of air, replacing it with the CO2 produced during fermentation. Then of course, when fermentation is done, just switch the connector to the ‘gas in’ post and the drain the fermenter via the ‘beverage out’ post, and the beer never comes in contact with oxygen… I hope. That all depends on whether enough CO2 is produced during fermentation to purge the keg.
Obviously it depends on gravity and minimally on temperature, but the average would be around 20 volumes of CO2 per volume of wort. You’d need a spunding valve on the receiving keg as well.
I can answer your question of purging the keg, as we had a member who used to do that. Due to gas mixing, and “pockets” in the keg( the same pockets is why we can’t properly purge kegs) it will result in a DO reading of about .2-4ppm in the finished beer, which will make your lovely lingering fresh malt go away in about 2-4 weeks.
Wouldn’t there also be some undesirable compounds in there as well? I know many breweries capture and use their CO2, but they must be purifying it as well.
When I saw the unit at Sierra Nevada, it was stated that they remove aromatic impurities, and had a foul smelling jar of the stuff, concentrated esters and sulfur compounds. Alcohol that is gassed off also gets recovered, and was used to full on site vehicles, I.e. No road tax.
We all know the smells coming off of fermentaion, and CO2 is odorless. So yeah, it has to be purified.
