When a brewery uses a 20bbl mashtun/lautertun, a 20bbl kettle/whirlpool, then they say they are using 40bbl fermenters. Are they producing 40bbls of beer on a 20bbl system or are they putting two batches into one fermenter, or are they leaving a ton of headspace? I was just trolling around on the used brewery equipment for sale on the internet and didnt know.