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Jun 08, 2022 View:

Shelf Life of Spent Grain

Hey all -

After some trial and error, we have finally been able to strain/separate our spent mash.  We ferment and distill on the grain with the grain milled to a fine flour.  I have attached an image of what the spent mash looked like after one day.  It ended up being somewhere between a batter and jello in consistency.  Unfortunately after a weekend of sitting in the distillery there was noticeable mold growing on the top surface of the mash.  Our farmer is (not surprisingly) concerned about the mold as are we.  It seems pigs are much more sensitive to mold than dairy cows.  Our hope was just do do one weekly delivery/pickup of grain meaning that at least a part of the mash would sit from Monday to Friday.

I am just curious what everyone else's experience is with spent grain shelf life?

I assume if we cover the mash it will last longer?
Does the fact that we are using flour and not a coarse grind make it mold faster?
Are there preservatives anyone is using the prevent mold/bacteria growth?
How much do your farmers care about freshness/mold?  Is there an acceptable level? 

Input/suggestions would be greatly appreciated!


Winter is much more forgiving, especially if you can keep your spent grains cold, frozen even.

Summer is brutal, shelf life is awful.  Realistically?  3 days, beyond that you push it.  We schedule grain pickups based on our distillation schedule.

We store spent grains in 25-30g snap top drums.  We do this because it makes it easy to trade drums and grain with our farmer, and most people can handle a 30g grain drum without much struggle.  One 530g batch is 9-10 drums depending on the grain and grind.  Once the warm weather comes around, we actually sanitize our drums and tops, and once we fill them, we don't open them back up.  I think this extends shelf-life a bit.

Also, we dewater near boiling - so the grain coming off is probably 180f and above.  Going into sanitized drums within a few minutes.

With more production volume, we're going to switch to Rubbermaid commercial garbage cans, because they are larger, easier to handle (with handles), and you can nest them together.


Spent grain is tasty food for everything, insects, animals, bacteria, mold, fungus, etc.  Consider that spent grain handling would probably benefit from the same sanitation and handling techniques as pre-distillation materials.  Putting spent grain into a dirty container (one that held moldy grain) is going to cause spoilage to happen much faster, the warmer the faster.

All that said, our farmer drives his bucket loader up to his pickup and dumps all the drums into the bucket.  How we wants to handle it is his prerogative, but we really don't want to be responsible for making an animal sick, so we'll take the extra care.


We treat our spent grain in almost the same sanitary manner as mash.  I want to give the farmer the best product possible, and I don't want anything growing that shouldn't be growing.

We dewater it slightly, but he's got his own separator. We pump it straight from the still into sanitized 275 gallon totes which he takes within a day or two.


A little off topic but how are you seperating the grain? 

Reply:6 hours ago, Urrazeb said:
Reply:20 hours ago, HedgeBird said:

Wire mesh works great if you trade efficiency for ease of separation.  If you keep your corn coarse and roller mill your malt, it's much easier to separate after distillation, especially when it's near boiling.


in some dairy farms, I have seen farmers put spent soya in drums with 2 inches of rock salt on top to slow down spoliage of the spent soya. Will this work with spent grain? How long do you think the spent grain will last in this scenario? Thanks