I think the fly vs batch argument is akin to the "does AG make better beer than extract". Whatever suits your system and your
approach to brewing is the right answer.
There are more advantages to batch sparging than just speed though. As discussed by Denny Conn (probably the biggest
proponent of batch sparging), it is important that your lautering vessel has no channelling and you are prepared to measure the
pH of the runoff. (from
here)
Lauter design is also highly important in fly sparging. Your lautering system must allow no channeling, or the sparge liquor
will drill straight down through the grain bed in only one or 2 locations and leave the rest of the mash unrinsed. Because the
buffering power of the grains in the mashtun is continually being diluted by the sparge water, its necessary to monitor the pH
of the runoff. Too high a pH will cause the extraction of tannins and polyphenols, compromising the quality of the beer. To
counteract this, it is often necessary to acidify the sparge water to keep the pH of the runoff below 6. Because the runoff may
take an hour or more, many brewers do a mashout step in an attempt to denature the enzymes and prevent further
conversion from taking place while the sparge is happening. However, this method will usually yield the highest extraction
from the grain.
I don't have experience of 150 litre batches (do 65 litre average) but I think when you add the additional volume of sparge
water to what must be a grist of approx 30kg for an average beer, mixing that water with so much grain would be difficult.
And the whole basis of batch sparging is that each addition of sparge water must be thoroughly mixed through the grain to give
a uniform gravity for each runoff (albeit that each runoff will be of a lower gravity).
I have fly sparged and now batch sparge for the following reasons -
1. Don't have to worry about how to keep an inch or two above the grain bed while sparging
2. Don't have to measure pH of the runoff when deciding when to stop sparging
3. Don't have to acidify the sparge water
4. Don't have to worry whether my lauter tun is geometrically designed to minimise channelling
All that said, if I was to do 150 litre batches I would probably fly sparge, if only to avoid mixing 30kg+ with the sparge water.
Good topic.
Cheers,
smudge
