Briggs described the potential benefits:
there was real hope for the commercial success of continuous systems with the advantages comprising:
• lower capital cost
• lower working capital because of less beer in process, as a result of faster throughput
• lower product cost as a result of lower beer losses, more ethanol and less yeast
• lower fixed costs because of less manpower as a result of less cleaning and automatic
• fermenter control.
The first attempts were made in the late 19th century and several different systems were tried in the years leading up to WW I. None proved successful in practice. One system involving beer moving from one open tank to another was revived in the 1950s, with experiments in the UK, Canada and New Zealand. It was in the latter two that these trials were put into practice in the 1960s.
In the UK, the process was championed by L.R. Bishop, who worked at the Watney brewery in Mortlake. He seems to have dedicated a good chunk of his career to developing the process, starting in 1925 when he was a post-graduate student. But it was only after WW II that his interest was able to take practical form, in the shape of a 1,000-gallon pilot plant. When this proved a success, a 1,000-barrel plant was constructed.
By the early 1970s, Watney had the system installed in four of their breweries: Mortlake, Mile End, Drybrough and Murphy. Between them, they were capable of producing 20,000 barrels a week. Or around a million barrels a year. Which was around 22% of their total output. The bulk of this capacity – 13,000 barrels per week - was at Mortlake.
At its peak in the early 1970s, around 4% of UK beer was brewed using one of the continuous fermentation systems. Though much of that seems to have been at Watney. With their capacity equivalent to 2.7% of UK production.
This is an excerpt from my book on 1970s brewing, "Keg!". Get your copy of "Keg!" now!
Listen to George Thompson, who ran the last continuous fermentation system in the northern hemisphere, talk about the process.
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