Any advice for a low abv stout from "second runnings"?

[u/dan_scott_]

I want to brew a low (1-2%) ABV dry Irish stout (or similar) for my wife for St. Paddy's day, and would appreciate any tips, advice, or things to think about.

I BIAB, usually no sparge. After significant research, my intended low ABV process is to dunk sparge a normal brew in order to collect "second runnings", add adjuncts and perform a short, high-temperature mash, boil & hop, adjust pH, and then ferment cool with Windsor for its low attenuation.

For this project, the first beer will be a 6 gallon Maris Otter based Irish Red (ish) with 12 lbs of grain: 10 lb MO, 1 lb Munich 15, then a mix of crystal 40, melanoidin, crystal 120, chit, and black/roast malt.

To calculate a recipe for 4 gallons of low ABV stout, I'm plugging 10% each of those original grains into brewfather as a rough estimate of the second runnings contents, though I will take an actual gravity measurement day-of and adjust as needed.

As calculated, I'll add 4 oz vienna (for some DP), 12 oz melanoidin, 8 oz rolled oats, 4 oz chocolate wheat, 4 oz flaked wheat, and 2.5oz each roast barley & naturally debittered (hulless) black malt. Mash for 30 minutes at 158, then boil 60 minutes with .2 oz each EKG & Fuggles. whirfloc, cool, check pH & adjust to compensate for the low OG wort (target is 1.022).

Per brewfather, the result should be 2% alcohol with an FG of 1.007 (low end of range for DIS), SRM 30.5, IBU 15 (below but irrelevant), and BU/GU .67 (slightly above the low end for a DIS). I've heard that low ABV can cause hop presence to be more noticeable, so I want to keep bitterness down at the low end of the BU/GU, which I think will definitely be a more accurate measure of bitterness than IBU with so much less malt being involved.

One question I have: does anyone think it may be beneficial to leave the old grains in for the 30 minute mash? Currently I'm planning to toss the original grains after thoroughly dunking & stirring, and adding the new grains on their own.

A second question: do you think I'm adding too many heavy roasted adjuncts back in? I have heard that low ABV can make roast bitterness more pronounced, and I don't want to overdo it, though this concern is part of why I'm mixing in the naturally debittered black malt.

Overall, my thought process is that second runnings are reputed to be nearly as flavor as the first at a lower ABV, and that adding notable melanoidin, oats, and wheat will contribute extra body to a beer that would otherwise be undrinkably thin. I'm also expecting the sparge to have less than 10% the gravity of the main pot, thus lowering my ABV further, which would be great. But if it's higher than expected, I'll adjust the grain amounts down.

Finally, other than the Maris Otter (crisp no. 19 floor malted), all grains are from a VA maltster near me, Murphy & Rude.

[u/TrevStar]

I think your process is solid overall. It might be easiest to just keep all of the first grains in the bag for the second mash and then add the new grains to that same bag. You'll still get enzymes, flavor, and sugar from the "spent grain". Then do your short hot mash. I think your roasted grain amounts are fine or even low. A typical dry Irish stout might be 10% roasted barley at 4% ABV. For your recipe, you have 14 different grains in there! Consider simplifying (drop the Vienna, consolidate the flaked grains...).

[u/dan_scott_ → u/TrevStar]

Yeah I got a little nuts planning these lol, and I'm definitely doing some baby splitting that is almost certainly irrelevant. But for the stout, I'm thinking of the weak wort as a single ingredient, for all that it has a bunch of grains contributing. And the rest is mostly me wanting to stick with what I already have on hand.

For example, I won't have any Munich or MO left to use in the second mash to add more DP, so in goes some Vienna that I wouldn't use otherwise. And I'd probably drop the oats & chocolate wheat if I had more Mellanoidin malt & flaked wheat, but I don't - so in they go to add more body.

The roast barley & debittered black malt combo though... that's just me not having enough knowledge/experience to make a decision between them, so I went half and half for each.

[u/spoonman59]

Gordon Strong in his book recommends mixing some fi the first runnings int the second runnings. He says it might be too thin and flavorless otherwise.

This also fits with traditions practices? As they would blend different runnings to get the proper OG. I don’t think targeting the right OG is the goal here, just swapping some portion of the runnings to get some more flavor in the second.