It’s the end of the barrel for the world-famous union sets (pictured) used to ferment Pedigree at the Carlsberg Marston’s Brewing Co (CMBC), in Burton-upon-Trent.

The company says the process is no longer viable because of a drop in cask volumes. Two of the sets will remain at the brewery as a piece of brewing heritage.

CAMRA is urging CBMC to preserve these historic brewing vessels.

Burton unions, or Burton union sets, is an unusual method of brewing using a system of wooden barrels and pipes which recirculates beer and yeast during the fermentation period. 

CAMRA national chairman Nik Antona said: “It’s obviously hugely disappointing that CMBC has taken the decision to retire its iconic Burton unions. It is arguably the last brewery in the world, and certainly in the UK, using this method and this decision will see a unique and historic part of Britain’s brewing heritage declared completely extinct.

“We’d urge CMBC to find some way to preserve these historic pieces of brewing equipment rather than simply scrap them, or make the union sets available to another brewery which might be interested in preserving this tradition.

“We do understand the need for breweries to remain efficient and ensure quality at a time when we are sadly seeing many closures.

“CAMRA is reassured that this news is tempered by the fact CMBC has invested a significant sum, worth several millions, in the site, which hopefully will secure continued brewing and support the cask ales which have long been brewed in Burton-upon-Trent.”

Marston’s director of brewing Emma Gilleland said: “We take great pride in the quality of our brews, and by moving cask Pedigree to stainless steel fermenters we will be able to deliver consistent strong quality for our customers and consumers going forward.

“We are committed to protecting the legacy of the union sets, both for the brewery and for Burton. We will invest in preserving two union sets which will remain at the brewery so they can continue to be part of its future as enduring, iconic symbols of British brewing.”

In its heyday, Marston’s Pedigree was regarded as the most sublime and complex of British ales. Brewed with the uncompromising hard waters from Burton-upon-Trent, the beer has a nutty delicateness, which can be masked by the sulphurous “snatch” from the sulphates in the area’s legendary “just perfect” liquor.

Housed in high-ceilinged maturation rooms, described by beer writer Roger Protz as a “cathedral of brewing,” the system was introduced in the 1830s and was once widely used for the production of “better” ales.

Other breweries have long since torn down their Burton union systems as needlessly elaborate, expensive relics. The former Bass union stands in the car park of the National Brewery Centre in Burton,

After fermentation begins the beer is transferred into 264 linked oak barrels, the production of carbon dioxide, as a by-product of fermentation, helps expel the yeast off the beer through swan-necked pipes into yeast collection troughs.

The practical purpose of the system was to allow excess yeast foam (barm) to be expelled from the casks without leaving excessive amounts of head space within. The system was quickly refined to separate any expelled beer from the wasted yeast, allowing it to flow back into the casks to continue fermentation.

Brewing scientists regarded the system as unparalleled for the production of bright, clean, strong-tasting pale ales.

However, the system with its flurry of pipes and casks and the necessity to keep the cavernous fermenting rooms at a cool temperature – even through long, hot summers – is expensive.