Fermented Oak Substrate observations

[PowerHobo]

Just wanted to leave some observations here because I was pleasantly surprised by my recent results.

I just purchased a very simple 2-chamber, 36 gallon compost tumbler on Craigslist about 2 months ago, and had it cleaned out and full of a fresh batch of Traeger oak pellets within a couple hours of bringing it home. There was some speculation here about whether or not the outside temps where I live would be detrimental to the fermentation process (the concern being killing off the microbes), but it appears to have been beneficial after comparing it to my first attempt at substrate, which was done indoors on the warm side of room temp.

I will say that hand mixing isn't completely avoided with the tumbler. Every other day or so I had to reach in (which was uncomfortably hot) and scrape off the sub that was stuck to the sides. Additionally, a noticeable amount of sub leaked out of the tumbler whilst turning. @Garin had the good sense to glue weed cloth over the aeration holes in his tumbler, but I never got around to it.

Top is substrate that spent 1 month in the tumbler outdoors in temps between 100f and 110f (in the shade), being turned once per day, then 1 month in a storage bin (also outdoors in the shade) being mixed once or twice per week, with hose water introduced as needed to keep the sub from drying out too much (I live in the driest city in the US). Bottom is substrate that spent 8 months in storage bins indoors in temps between 76f and 80f, being mixed once every single day (excluding a couple lapses).

As you can see, the 2-month outdoor sub is significantly darker than the 8-month indoor sub.

I'm absolutely tickled that I have 38lbs (give or take) of beautifully dark fermented oak in just 2 months. The sub is completely cool now, with no lingering fermentation smells, and I'll be trying it out on a couple larvae at my next sub change. I'm already having good success with the indoor (lighter) sub with a group of 22 rhino beetle larvae, with a handful exhibiting somewhat drastic growth.

There was also a bit of difference in the recipe, that likely contributed. The outdoor batch was:

1. 20lbs of Traeger oak wood pellets expanded with boiling water
   
2. 1 cup of wheat bran to every 5 cups of expanded oak pellets
   
3. about 2 tablespoons of active dry yeast
   
4. about 4 cups of frass coffee (a handful of larval frass soaked in hot water until it's mostly dissolved when stirred)
   

The indoor sub was the same, but used all purpose unbleached flour (in the same amounts) when I started it. At one point about 4-6 weeks in, as some of you will surely remember, it appeared to have stalled, and I had to kickstart fermentation again by mixing in the appropriate amount of wheat bran (instead of flour), yeast, and frass coffee.

Aside from just seeming to work much better, if the wheat bran is found in grocery bulk bins it's actually cheaper than the bags of flour. The smell of the freshly fermenting sub, however, is arguably worse, though for the results it's worth it.

... and that's about all. I'm sitting on a surplus of usable sub for the first time ever, and I'm tickled pink. I also have another full batch that's just about ready to come out of the tumbler to mature in the bins. I clearly need more larvae.

 

[piggy145]

Very nice, this is amazingly fast way to create substrate and breaks down the barriers of getting into this hobby. I'll be investing in a Tumbler very soon. This is huge. 

 

[piggy145]

Very nice, this is amazingly fast way to create substrate and breaks down the barriers of getting into this hobby. I'll be investing in a Tumbler very soon. This is huge. 

Also what color was the tumbler substrate when you decided to put it in a storage bin?

 

[PowerHobo]

Also what color was the tumbler substrate when you decided to put it in a storage bin?

Maybe like milk chocolate or even a little lighter. It darkened up drastically once it was maturing in the storage bins.

It is also important to mention that I didn't have a control batch going at the same time, which is to say I didn't have another batch going using the storage bin/hand mixing method. There is every possibility that the outdoor heat is what did the trick rather than the tumbler. The only real reason I can see that the tumbler may have assisted (beyond making it a little easier to mix) is that it has so many ventilation holes that the aerobic conditions were surely better than they are in the bins.

 

[Garin]

Great job and congrats on a nice big bin of substrate! I guess you are starting to take advantage of triple digit temps. I was talking to Goliathus about substrate making and he said that the 3 most important things are temperature, aeration and mixing. He also leaves his tumbler outside during the summer in triple digit temperatures. So I think there is no doubt that the high heat really makes things break down fast. So I guess you now know the key to making your substrate. Just make sure you make enough to last you through the winter months because then it will slow the process down.

 

[Garin]

I just had one question. When you make the frass coffee and you boil the frass, doesn't that kill off the microbes in the frass and thus defeats the idea of adding frass? I think warm water or possibly hot water but boiling usually kills off all the germs, etc. But maybe I'm not understanding the idea of frass?

 

[PowerHobo]

I just had one question. When you make the frass coffee and you boil the frass, doesn't that kill off the microbes in the frass and thus defeats the idea of adding frass? I think warm water or possibly hot water but boiling usually kills off all the germs, etc. But maybe I'm not understanding the idea of frass?

Honestly, I misspoke, and will go back to correct. I don't actually boil the frass in the water, as my wife would legitimately murder me. I bring a pot of water to the heat at which I see it trying to boil (bubbles on the bottom starting to separate and rise, but certainly not a rolling boil) then take it outside, and it has a couple minutes to cool while I grab a bucket/lid from the garage, go get my frass container and dump some in, because I'm awful at preparation. A hefty handful of frass goes in the bucket, hot water goes in, lid goes on, and I just let it sit and dissolve for half hour or so. It doesn't really dissolve all the way, there are still pellets left by the time I introduce it to the new sub batches.

It may still be too hot, and be killing the microbes, honestly. It's also probably completely unnecessary considering the active dry yeast that goes in. In that case I'm just considering it to be my version of Jesse Pinkman's pinch of chili powder (Breaking Bad)  :lol:

Just make sure you make enough to last you through the winter months because then it will slow the process down.

I've got something like 85lbs of substrate once this last batch is done, so I should be ok. Despite my jokes, with as tight as money has been, I probably won't be getting any more larvae for a good while unless something irresistible comes up, or my trip to AZ (if I can make it) is particularly fruitful, in which case I'll only keep a handful of larvae from a couple species anyway.

 

[piggy145]

Hey @PowerHobo, remember when I asked you about the lids on fermenting substrate? That substrate right not is very cool brown. I think the heat has something to do with it fermenting a lot faster, I live in Arizona where we get triple digits every day this past summer and here are the results. I mixed every so often too. This batch was started on June 20th