Of course, it’s nowhere near as simple as that. Many of the new wave of “craft keg” beers are essentially conventional kegs, where the beer is filtered, and a cylinder of CO2 is connected up to the container to propel it to the tap at the bar. However, some use a system called “KeyKeg”, which is well explained here by Magic Rock Brewing. Here, the beer is held in an inner bag within the container, in a similar way to bag-in-box wine, and the dispense gas exerts pressure on this bag to push the beer to the bar, but doesn’t actually come into contact with it. A big advantage of this for small breweries is that it uses one-way containers, so all the trouble of reclaiming empty kegs is avoided, although obviously there is a cost penalty.
People soon realised that, if the beer in the keykeg was unfiltered, and therefore retained its natural yeast, it could qualify as “real ale”, as it could undergo a secondary fermentation, and avoids all contact with the CO2 used to pressurise the outer container. Now, CAMRA has always been notorious for pedantic nitpicking over methods of dispense, which I have to say I’ve never been able to get particularly worked up about. It’s not so much the principle, as the mind-blowing black and whiteness of it all. Ideally, it would be better to serve cask beer without a cask breather, but to my mind it’s far preferable to either proper keg or sour cask. A potential problem immediately occurs to me that, as the inner container does not vent to the atmosphere, if a meaningful secondary fermentation does take place, it could lead to a build-up of CO2, thus producing very fizzy beer and possibly stirring up the sediment to dispense cloudy beer. But I’m no expert.
The question occurs, though, as to what problem this system is actually meant to solve. It reminds me of the great Dr Johnson when he said: “Sir, a woman's preaching is like a dog's walking on his hind legs. It is not done well; but you are surprised to find it done at all.” So, you can (perhaps) serve real ale from a keg. But I doubt whether that will make any difference to the customer who is already happy to drink craft keg, and the average punter who goes into a pub and looks for handpumps on the bar will just regard it as another keg beer, even if it has a little notice saying “this is actually real ale”. And some may fear that it is, in a sense, relegitimising keg beer and may end up to be the thin end of the wedge.
I’ll give it a try if I come across it, but I can’t really see it becoming a mass-market phenomenon, especially given the extra cost and dubious environmental credentials of disposable containers. And, personally, if I order a keg beer, the least I would expect is that it will be crystal clear, as that surely is one of keg’s key advantages. At the end of the day, it’s hard to see “real ale in a keg” being any more than an exercise in proving a point.