Using Brett to Carb Sour Beer

I'm going to be making an all-brett beer soon, so will be making a large starter. Around the same time I'm going to be bottling Six 4.5-liter (UK gallon) carboys of different sour beers.

These sours range in age from 14 months to 20 months. To ensure they carb, I'm going to add some yeast at bottling. Since I'm doing 6 small batches, trying to add a small amount of dry yeast seems difficult.

I thought I would decant about 1.5 pints of the Brett starter before the yeast settles and use that to bottle the sours with. It would be about 4 ozs of starter to 150 ozs of sour beer, or a little less than 3%

1) Is Brett fine to use to help carb the beers? I don't see any reason why it should be a problem.

2) Is this enough yeast to get the job done?

As for the exact calcuations, I can't help you there.

That being said, Brett tends to put out less co2 than Sacc. When carbonating my Orval clone I used enough priming sugar to bring it to 4 volumes (based on a calculator) and it wound up only getting to ~2 or so.

YMMV, but I'd search a bit on the subject (though I'm not sure how extensively it's been studied) before trying to pin down a certain carb level.

Maybe someone else can chime in?

I do believe White Labs has recanted their original statement that brett produces less CO2. Last I read was that if it makes less, it's negligible. So with that said, my guess is people are using priming calculators and assuming higher retained CO2 over long term aging. Often times that can make a difference. I have had no issue bottling my brett beers.

Any brett should be fine for bottle conditioning. I would hand calculate the priming sugar needed rather than use a calculator. Since I started hand calculating my sugar additions I've had much better carbonation results. http://hbd.org/brewery/library/YPrimerMH.html You'll notice on the link the highest temp accounts for .78 vol of CO2 retained in the beer. I believe Oldsock at The Mad Fermentationist figures for .4vol retained with is due to the CO2 coming out of suspension over time. I have noticed in longer term aged beers I've done that when I calculate for the retained CO2 at the temp the fermentor sits, I end up low on carbonation. Now I figure for a lower level of CO2 and have been getting better results.

I was planning on assuming the max temp was 75 F (it probably got up to 70 F, but not above), and using a calculator and priming to 3 volumes. That way I figure I'll end up somewhere between 2 and 3 volumes.

That sounds fine. Hand calculation is stupid easy though. You just have to convert the quantity of beer to be bottled into liters.