Lager vs Kveik: The Test

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There's an interesting theory that yeast (ester) profiles are the result of overflow of the right kind of metabolism and yeast ester production can be controlled by the brewer manipulating the fermentation process. Rather than low gravity worts, per se, I've found promoting the wrong kind of metabolism subdues otherwise noticeable yeast profiles in low gravity English ales. But these beers are best consumed fresh, as they tend to get bland over time. Pressure, even from an airlock, risks a bland beer. So does pitching poor quality yeast, which take days for fermentation to start then proceed slowly by the skin of their teeth. Insufficient aeration. Dry yeast, too, imho. I think the idea is to promote fermentation (ester overflow) then tweak it to obtain a balanced yeast profile. At least one that the brewer likes. If it's not working, try another yeast strain. Eventually, a Yorkshire ale strain is going to be chosen for English ales 🤫
 
There's an interesting theory that yeast (ester) profiles are the result of overflow of the right kind of metabolism and yeast ester production can be controlled by the brewer manipulating the fermentation process. Rather than low gravity worts, per se, I've found promoting the wrong kind of metabolism subdues otherwise noticeable yeast profiles in low gravity English ales. But these beers are best consumed fresh, as they tend to get bland over time. Pressure, even from an airlock, risks a bland beer. So does pitching poor quality yeast, which take days for fermentation to start then proceed slowly by the skin of their teeth. Insufficient aeration. Dry yeast, too, imho. I think the idea is to promote fermentation (ester overflow) then tweak it to obtain a balanced yeast profile. At least one that the brewer likes. If it's not working, try another yeast strain. Eventually, a Yorkshire ale strain is going to be chosen for English ales 🤫
That sounds quite possible, except for air lock pressure.

We have to get rid of this myth. The pressure that is generated through a filled air lock on the yeast in suspension is the equal amount of pressure that would be generated by filling the fermenter about 2cm higher with wort (I am an hydraulic engineer so I know a bit about this topic).

Nobody would say that filling a fermenter 2cm higher results in ester surpression.

BUT, and there you are probably right, what does happen is that the unfilled air lock let's in oxygen and that little additional oxygen changes the metabolic pathways used by the yeast towards more expressive pathways.

That is probably the reason why open fermentation of English ales (at least for the first few days) leads to different results than the completely anaerobic fermentation under an air lock.

With saison yeasts this little additional oxygen seems to boost the enzyme expression used for the diastetic nature of most of these yeasts. A lack of oxygen during the first few days results with sensitive strains in a saison stall, open fermentation for the first few days seems to solve this issue plus boosts yeast expression. In my experiments, this worked out well.
 
That sounds quite possible, except for air lock pressure.

We have to get rid of this myth. The pressure that is generated through a filled air lock on the yeast in suspension is the equal amount of pressure that would be generated by filling the fermenter about 2cm higher with wort (I am an hydraulic engineer so I know a bit about this topic).

Nobody would say that filling a fermenter 2cm higher results in ester surpression.

BUT, and there you are probably right, what does happen is that the unfilled air lock let's in oxygen and that little additional oxygen changes the metabolic pathways used by the yeast towards more expressive pathways.

That is probably the reason why open fermentation of English ales (at least for the first few days) leads to different results than the completely anaerobic fermentation under an air lock.

With saison yeasts this little additional oxygen seems to boost the enzyme expression used for the diastetic nature of most of these yeasts. A lack of oxygen during the first few days results with sensitive strains in a saison stall, open fermentation for the first few days seems to solve this issue plus boosts yeast expression. In my experiments, this worked out well.
I don"t think it has much to do with oxygen whilst there's positive pressure involved, why an airlock is very useful when fermentation winds down. Even the slightest back pressure increases CO2 levels inside the FV and wort. From a yeast's perspective, it changes behaviour causing increased rates of foaming, which leads to mess and loss of yeast. Not all airlocks are equal, though. I've some BetterBottle dry airlocks that have a tiny glass sphere (weighing bugger all) that seal things and some big chunky Speidel airlocks, which I quite like, which promote more back pressure, relatively speaking, and more than enough to alter the behaviour of top-cropping yeast. Even my best lagers have been fermented 'open', without an airlock. Although foaming isn't usually a problem with lager yeast CO2 is a yeast stress factor. I suspect yeast cells monitor CO2 levels to make biological decisions that limit population growth.
 
I don"t think it has much to do with oxygen whilst there's positive pressure involved, why an airlock is very useful when fermentation winds down. Even the slightest back pressure increases CO2 levels inside the FV and wort. From a yeast's perspective, it changes behaviour causing increased rates of foaming, which leads to mess and loss of yeast. Not all airlocks are equal, though. I've some BetterBottle dry airlocks that have a tiny glass sphere (weighing bugger all) that seal things and some big chunky Speidel airlocks, which I quite like, which promote more back pressure, relatively speaking, and more than enough to alter the behaviour of top-cropping yeast. Even my best lagers have been fermented 'open', without an airlock. Although foaming isn't usually a problem with lager yeast CO2 is a yeast stress factor. I suspect yeast cells monitor CO2 levels to make biological decisions that limit population growth.
You have to believe me, as long as there's water involved, the maximum back pressure generated by an air lock is equal to the water hight in the air lock. Does not matter how it is build.

You wouldn't say that filling up your fermenter two cm higher would change ester expression, would you? That's what an air lock does, it generates additional pressure equal to the water height in itself, which is usually only one or two cm.

Positive pressure does not mean that no oxygen gets inside, the effect that Henry's law describes takes care of that.
 
You wouldn't say that filling up your fermenter two cm higher would change ester expression, would you?
It changes the behaviour of top-cropping yeast and I prefer open fermented beers. That's all I'm saying.

Positive pressure does not mean that no oxygen gets inside, the effect that Henry's law describes takes care of that.
Not all FV walls, taps and other 'sealed' openings are impermeable to O2, of course, but O2 entering via the point of off-gasing is limited by basic physics of mass movement in one direction, out of the active FV. I'm not sure if Henry covered that bit, no pun intended 😃 Fermenting wort is far from an inert, ideal solution simple to model. There's a lot of biology going on in that stuff. Letting the esters overflow isn't a bad idea 😉
 
It changes the behaviour of top-cropping yeast and I prefer open fermented beers. That's all I'm saying.


Not all FV walls, taps and other 'sealed' openings are impermeable to O2, of course, but O2 entering via the point of off-gasing is limited by basic physics of mass movement in one direction, out of the active FV. I'm not sure if Henry covered that bit, no pun intended 😃 Fermenting wort is far from an inert, ideal solution simple to model. There's a lot of biology going on in that stuff. Letting the esters overflow isn't a bad idea 😉
I understand your reasoning regarding the oxygen inflow against the off-gassing direction. However, you would be surprised how much turbulences are happening within the flow through openings, that's not a laminar structure at all. So there's always some counter direction mixing involved.

And as soon as we got a bigger opening and not only an empty air lock, the flow speed becomes so small, it doesn't make any difference any more.

If the behaviour of top cropping yeast changes, the reason is not the pressure, there must be something else. The pressure difference between air lock and no air lock is so small, it is completely neglectable (is that a word?).
 
If the behaviour of top cropping yeast changes, the reason is not the pressure, there must be something else. The pressure difference between air lock and no air lock is so small, it is completely neglectable (is that a word?).
It's most likely a pressure induced increase in CO2 levels in the fermenting wort that increases the rate of foaming. Top-cropping brewer's yeast practice CO2 powered floating to an extreme, by brewer's yeast standards. CO2 is what makes active yeast bouyant generally. Top-croppers seem to have taken it to another level. The difference in behaviour is easily observable, just remove or add an airlock. Even in a starter. The pressure difference might seem small (or negligible) to us, but, for yeast, it's enough to elicit behavioural changes.
 
I've brewed several beers with Lutra. It is quickly becoming my house ale yeast. Being an ale yeast, it does not consume the same sugars that lager yeasts do so it will never have the "crisp" flavor note of a lager. I've never had a problem with my Lutra beers dropping clear and have brewed several at room temp that dropped clear enough in ten days that I could read the paper through it.

When I brew with Lutra (or Voss), I usually pitch it at room temp (~23°C) and let it ride. Lutra has not made a disappointing beer for me yet.

All kveik strains I've brewed with require some conditioning time in the keg. Lutra less than others but still, a couple weeks.

The idea that lager crispness is because lager yeast eat sugars that ale yeasts don't is a little misleading, IMO. It may be true that "on average" lager yeasts are more attenuative, but it's not universal. I think the notion sometimes comes from the fact that lager strains can ferment raffinose and melibiose. This fact is quite true, but also not really relevant, because they are either absent from beer wort or present in only in insignificant amounts. A breakdown of what species use what sugars:

- Glucose: Ale and Lager, virtually 100% attenuation
- Fructose: Ale and Lager, virtually 100% attenuation
- Sucrose: Ale and Lager, virtually 100% attenuation
- Maltose: Ale and Lager, virtually 100% attenuation
- Maltotriose: Specific Strain dependent, but both Ale and Lager strains use it, to various extents. It's the strain and not the species per se that matters for Maltotriose, which is the big driver of attenuation differences between strains.
(- Raffinose: Lager Strains Only (but not significant in beer))
(- Melibiose: Lager Strains Only (but not significant in beer))
 
There was a more informal Bru Club article on Lutra vs 34/70. Spoiler: with a total of 51 tasters, the results were not-significant, but only 1 away (p=0.053 vs p=0.050).
https://brulosophy.com/2022/03/03/t...a-kveik-vs-saflager-w-34-70-in-a-german-pils/

"While 24 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 23 did (p=0.053), indicating participants in this xBmt were unable to reliably distinguish a German Pils fermented with Omega Yeast OYL-071 Lutra Kveik at 66°F/19°C from one fermented with Saflager W-34/70 at 52°F/11°C."

Jeez. According the the numbers, if there were no detectable difference between these beers, there was only a 5.3 percent chance that 23 or more of the tasters would make the correct choice. But they did. I'd feel pretty good about betting a paycheck on "they tasted a real difference." But "indicating participants in this xBmt were unable to reliably distinguish" fits the usual "nothing matters" narrative.
 
It's most likely a pressure induced increase in CO2 levels in the fermenting wort that increases the rate of foaming. Top-cropping brewer's yeast practice CO2 powered floating to an extreme, by brewer's yeast standards. CO2 is what makes active yeast bouyant generally. Top-croppers seem to have taken it to another level. The difference in behaviour is easily observable, just remove or add an airlock. Even in a starter. The pressure difference might seem small (or negligible) to us, but, for yeast, it's enough to elicit behavioural changes.
It might be, but I doubt it. Let's assume that the pressure somehow increases co2 levels in the liquid, this means that the off-gassing would be slowed down until the higher limit of dissolved co2 has been reached, which would be almost instantly as co2 is constantly excreted by the yeast in big amounts. Once this limit has been reached, off-gassing, ie bubbles, would form in the same manner as it would without the additional pressure of the air lock. It's a bit like a container with two openings. Through the first opening, water gets pumped in. Once it's full, through the other opening the same amount flows out that gets pumped into it. Once you increase the size of the container, it only affects the outgoing flow up until it is full again. From then, same output as before.

Or do you mean that the slightly increased co2 concentration within the liquid somehow affects the metabolism of the yeast and not the bubbles the kräusen?

If that would be the case, atmospheric pressure changes would affect the brew even stronger, these pressure differences are bigger. Or brewing at an altitude.... Mt Everest English ester bomb? Who knows :D
 
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It might be, but I doubt it. Let's assume that the pressure somehow increases co2 levels in the liquid, this means that the off-gassing would be slowed down until the higher limit of dissolved co2 has been reached, which would be almost instantly as co2 is constantly excreted by the yeast in big amounts. Once this limit has been reached, off-gassing, ie bubbles, would form in the same manner as it would without the additional pressure of the air lock. It's a bit like a container with two openings. Through the first opening, water gets pumped in. Once it's full, through the other opening the same amount flows out that gets pumped into it. Once you increase the size of the container, it only affects the outgoing flow up until it is full again. From then, same output as before.
Now you're just gasing off 😂 You've got to stop thinking like a squishy human bean and start viewing the world like a yeast.
 
The idea that lager crispness is because lager yeast eat sugars that ale yeasts don't is a little misleading, IMO. It may be true that "on average" lager yeasts are more attenuative, but it's not universal. I think the notion sometimes comes from the fact that lager strains can ferment raffinose and melibiose. This fact is quite true, but also not really relevant, because they are either absent from beer wort or present in only in insignificant amounts. A breakdown of what species use what sugars:

- Glucose: Ale and Lager, virtually 100% attenuation
- Fructose: Ale and Lager, virtually 100% attenuation
- Sucrose: Ale and Lager, virtually 100% attenuation
- Maltose: Ale and Lager, virtually 100% attenuation
- Maltotriose: Specific Strain dependent, but both Ale and Lager strains use it, to various extents. It's the strain and not the species per se that matters for Maltotriose, which is the big driver of attenuation differences between strains.
(- Raffinose: Lager Strains Only (but not significant in beer))
(- Melibiose: Lager Strains Only (but not significant in beer))
I fully agree. This is actually something this test of mine will also address - I brewed one wort, split it and fermented it with two yeasts. So the wort I fed to the two yeasts is identical in every possible way the word can be interpreted, because it's the same wort, same batch.

I still got the exact same FG from both yeasts - one being a cold lager yeast fermented at 10°C and the other being a hot ale yeast fermented at 25°C. Both started at 1.050 and ended at 1.010 for an identical attenuation of 79%. And I spent a lot of time on getting the absolute perfect hydrometer readings for both, trust me. I spend a good 20 minutes with each test tube, stirring and getting the CO2 out of there, heating it up to release more CO2 and to get the temperature to 20°C, using the same thermometer to measure both samples to the same temperature. I even had the hydrometers floating in the test tube, where I took a reading, and then I filled it up more (added little stones to boost the beer level in the tube) so I could measure on the meniscus at the top of the tube. I took pictures and between the two I can't see a realistic difference in the readings. If I had to say, I'd have to guess there's a 0.0025 difference between the two, but that can be attributed to carbonation or even temperature difference under 1°C between the two batches. Proof:

This is the Diamond Lager's FG reading at 20°C:
XaGHfWTl.jpg


This is the Omega Kveik Lutra's FG reading at 20°C:
XlU7Wiwl.jpg


So I'll have to say that if the lager batch in this test is more "crisp" than the ale yeast, there's something else at play, it's definitely not the FG making the difference here.
 
OK so the bottled beers seem to be flocculating already, so I'm guessing the carb drops have been eaten up and the yeast are settling down. I moved one into the fridge to see if it's where I want it, and if it's ready, I'll be moving all but one into the fridge as well tonight.

In 2 months' time I'll do a comparison video between the warm stored beer, and one of the cold stored beers.
 
If the intention is to compare the different yeast then all other factors need to be controlled, including condition of the yeast, to make things comparable. Otherwise it's apples and oranges for several reasons. I can see several potentially confounding factors in your comparison, which risk invalidating conclusions about any differences being due to yeast strain. Although I'm confident you'll prefer Diamond Lager yeast, regardless, if you want a lager.
 
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One thing I just thought about, flocculation and completed consumption of carbonation sugars are not connected. There can still be plenty of sugar in solution while the yeast starts to drop out already.
 
I just made a Lutra starter and as usual by the time I got from the kitchen to the basement brewery the yeast had settled. I'm brewing a spruce tip IPA for the 4th and putting it in a pin. Because of how fast this yeast settles and the beer being so clear I'm adding 3 grams of CBC along with the sugar. I'm interested in the bottle carb on those samples.
 
Alrighty, Friday afternoon I couldn't hold my anticipation for this beer and I opened one of the bottled beers. To be clear, this has been carbonating in the bottle under heat since Monday morning, giving me around 5 days of carbonation. I have done this before with other ale yeasts and typically the beers are fairly carbonated by this stage, albeit really "green".

However, this beer was almost completely flat. It had a really faint "pst" when I opened the swingtop, so there is pressure, but it was terribly low. I've read elsewhere that Lutra (or Kveik as a whole, for that matter) doesn't really like bottle conditioning after the cold crash, but I didn't ever expect it to happen to me. I've got the rest of the bottles now at room temp, and I'll take another look this coming weekend.

Has anyone else here ever had this happen?

Anyway, onto the beer, I'm not sure if this is due to the yeast used, or perhaps the carbonation drop was diluted and not properly fermented by the residual yeast, but the beer was fairly sweet. The hop character, same as with the hydrometer sample I tested, was very subdued and hidden under a fresh, soft and fruity note that I'm not at all opposed to, it just doesn't fit the beer style at all.

Overall, it's a good tasting beer, the bottled Kveik version of it, at least. Carbonation in the bottle is just an issue, which is something cool to have on hand for the future video I have planned for two of these bottles. Can't wait to see how the next few weeks work on the beers in the kegs.

That reminds me, I need new post seals before I can carbonate or tap these kegs...
 
Alrighty, Friday afternoon I couldn't hold my anticipation for this beer and I opened one of the bottled beers. To be clear, this has been carbonating in the bottle under heat since Monday morning, giving me around 5 days of carbonation. I have done this before with other ale yeasts and typically the beers are fairly carbonated by this stage, albeit really "green".

However, this beer was almost completely flat. It had a really faint "pst" when I opened the swingtop, so there is pressure, but it was terribly low. I've read elsewhere that Lutra (or Kveik as a whole, for that matter) doesn't really like bottle conditioning after the cold crash, but I didn't ever expect it to happen to me. I've got the rest of the bottles now at room temp, and I'll take another look this coming weekend.

Has anyone else here ever had this happen?

Anyway, onto the beer, I'm not sure if this is due to the yeast used, or perhaps the carbonation drop was diluted and not properly fermented by the residual yeast, but the beer was fairly sweet. The hop character, same as with the hydrometer sample I tested, was very subdued and hidden under a fresh, soft and fruity note that I'm not at all opposed to, it just doesn't fit the beer style at all.

Overall, it's a good tasting beer, the bottled Kveik version of it, at least. Carbonation in the bottle is just an issue, which is something cool to have on hand for the future video I have planned for two of these bottles. Can't wait to see how the next few weeks work on the beers in the kegs.

That reminds me, I need new post seals before I can carbonate or tap these kegs...
Kveik rule number one, don't talk about the kveik club.

Rule number two, don't cold crash!!! :D

I've had kveik behave like that... Turn some bottles upside down, shake them a bit, put them back. Repeat every day for one week. Bottles should be good bz then. The yeast just drops out of solution too quickly and wants to be agitated manually. Especiallz if the numbers are limited due to a cold crash.
 
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Kveik rule number one, don't talk about the kveik club.

Rule number two, don't cold crash!!! :D

I've had kveik behave like that... Turn some bottles upside down, shake them a bit, put them back. Repeat every day for one week. Bottles should be good bz then. The yeast just drops out of solution too quickly and wants to be agitated manually. Especiallz if the numbers are limited due to a cold crash.
Having a similar issue with a kegged beer that fermented on Lutra. It was a BIG Strong Belgian ale (OG > 1.077) that dropped like a rock, which I transferred to the keg for spunding after 5 days, SG @ 1.018. The sample was still cloyingly sweet, and hasn't dropped but a point or two since kegging. Set the keg in an ambient 68F basement with a 15 psig spund on the Gas-in post.

Two weeks have gone by. Any suggestion? Target FG was 1.010. Should have enough sugar, but the yeast appear to have given up.
 
Having a similar issue with a kegged beer that fermented on Lutra. It was a BIG Strong Belgian ale (OG > 1.077) that dropped like a rock, which I transferred to the keg for spunding after 5 days, SG @ 1.018. The sample was still cloyingly sweet, and hasn't dropped but a point or two since kegging. Set the keg in an ambient 68F basement with a 15 psig spund on the Gas-in post.

Two weeks have gone by. Any suggestion? Target FG was 1.010. Should have enough sugar, but the yeast appear to have given up.
Either pitching more lutra or doing some strong man exercises called "shake the keg".
 
Either pitching more lutra or doing some strong man exercises called "shake the keg".
I considered pitching a sachet of KV-1116 Champaign yeast. Good fermenter at room temperature, plus plays nice with high alcohol liquids. It's served me well with some wines that stalled out, later restarting and finishing in the 14~15% ABV range. Oddly, I've never repitched yeast in a stalled beer fermentation. This one had a lot of dextrose added at flameout and clearly needs to dry out. It's way too sweet as is.
 
I wouldn't pitch champagne yeast in a finished beer. It'll go past your intended FG, almost certainly.

But yeah, the Lutra not doing it's job in the bottles here is frustrating, to say the least.
 
I considered pitching a sachet of KV-1116 Champaign yeast. Good fermenter at room temperature, plus plays nice with high alcohol liquids. It's served me well with some wines that stalled out, later restarting and finishing in the 14~15% ABV range. Oddly, I've never repitched yeast in a stalled beer fermentation. This one had a lot of dextrose added at flameout and clearly needs to dry out. It's way too sweet as is.
If you add another yeast, be sure that it cannot metabolize longer sugars. For example, cbc1 would be perfect. Most Champaign yeasts actually also fall into this category, except for the ones that don't....
 
I wouldn't pitch champagne yeast in a finished beer. It'll go past your intended FG, almost certainly.

But yeah, the Lutra not doing it's job in the bottles here is frustrating, to say the least.

Unless the champagne yeast is K1V-1116, it's not going to do anything to the original beer's residual sugars, i.e. maltotriose. Wine/Champagne yeasts in general can't use it.
 
Unless the champagne yeast is K1V-1116, it's not going to do anything to the original beer's residual sugars, i.e. maltotriose. Wine/Champagne yeasts in general can't use it.
Good point. I hadn't considered targeting a specific "trose". In order to reach the OG, the recipe (scaled down from a brewery recipe) required a lot of dextrose added at flame-out. So I should probably focus on an s. Cerevisiae that is alcohol tolerant and likes simple sugars?
 
Good point. I hadn't considered targeting a specific "trose". In order to reach the OG, the recipe (scaled down from a brewery recipe) required a lot of dextrose added at flame-out. So I should probably focus on an s. Cerevisiae that is alcohol tolerant and likes simple sugars?

Well, the dextrose is long gone at this point. It would have been the first thing eaten. Your wort/beer went from 1.077 to 1.018. The remaining fermentables are maltotriose, and maybe some maltose. Yeast work from simplest to more complex sugars.
 
Well, the dextrose is long gone at this point. It would have been the first thing eaten. Your wort/beer went from 1.077 to 1.018. The remaining fermentables are maltotriose, and maybe some maltose. Yeast work from simplest to more complex sugars.
So K1V-1116 would be a good yeast to finish up the unfermented complex sugars? I also thought of dosing with amyloglucosidase, but the results would be unpredictable at best, with likely a lot of harsh alcohol notes.
 
So K1V-1116 would be a good yeast to finish up the unfermented complex sugars? I also thought of dosing with amyloglucosidase, but the results would be unpredictable at best, with likely a lot of harsh alcohol notes.

I would probably use fresh yeast of the same strain as the original, unless it is already at/near its ABV tolerance limit. You could use K1V-1116, but I don't know if you could predict that it will stop at (or get to) where the original strain should have. Every strain that uses maltotriose uses it to different degrees.
 
Perfect timing for this thread. My next brew will be fermented with Lutra or Voss depending on what I brew.
I haven't had any problems carbonating voss. But I don't cold crash. I put priming sugar per bottle. Leave at same temp as fermentation. Voss is generally carbonated after 5 days, sometimes less. Then put in fridge for minimum 2-3 days.
No experience with lutra though
 
I haven't had any problems carbonating voss. But I don't cold crash. I put priming sugar per bottle. Leave at same temp as fermentation. Voss is generally carbonated after 5 days, sometimes less. Then put in fridge for minimum 2-3 days.
No experience with lutra though


I keg, so once the beer is transferred it's going to be "cold crashing". Will that matter or should I give the beer more time before transferring to kegs? Maybe "bottle condition" in the keg before sticking it in the kegerator?
 
I pressure ferment the kveik lager, then drop the first yeast and cold crash. Drop more yeast and then add super F finings. Then closed transfer into Keg and keep it in keg fridge.
 
I keg, so once the beer is transferred it's going to be "cold crashing". Will that matter or should I give the beer more time before transferring to kegs? Maybe "bottle condition" in the keg before sticking it in the kegerator?
The main part of the batch is in a keg, after cold crashing, and I'll be force carbonating in the keg. I'm not sure why people naturally carbonate with sugar in a keg. It doesn't make sense to me. It takes longer, the beer is warm for a much longer time and you end up with more slurry in the bottom of the keg. I don't get it.
 
I'm not sure why people naturally carbonate with sugar in a keg.

A few reasons to naturally carbonate in a keg...
- All CO2 cylinders or regulators already in use
- Cost (maybe, depending on local CO2 prices)
- Cloning. For example, Saison Dupont is a very highly carbonated beer that gets a not insignificant chunk of its ABV from refermentation. You could brew it with more malt (or sugar added to the boil/primary) instead of adding sugar to carbonate, but it wouldn't be the same beer. I've done Dupont clones both ways.
 
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