Details on fermenting wood pellets

G

Garin

Chalcosoma
Hello to all of you beetle breeders that have used wood pellets to make decomposed substrate. I know there are many posts in regards to fermenting wood pellets to make substrates. I have tried to read them all as well as posts on other sites. To make sure I am doing this correctly, I made a list of steps in the ferment process. However, I had a few questions in regards to these steps. I have the questions at the end of the list. Thank you in advance for any input and answers to the questions:

1. Get Traeger Wood Pellets. I know most people use the Oak pellets but I have read that on the west coast that the ingredients are actually mostly Alder wood. However, I assume that since many on the west coast have used these pellets that Alder works fine.

2. Add very hot water and mix. Add just enough hot water to turn the pellets into sawdust but don’t make it too wet or it won’t mix well with the flour or wheat bran.

3. Add unbleached flour or wheat bran (I have read that wheat bran works better) and yeast to the sawdust. Add the flour or wheat bran in a 5 to 1 ratio. ex: if using 15lbs of pellets, add 3 lbs of wheat bran. I am not sure how much yeast to add. One tablespoon per 15lbs of pellets?

4. Mix thoroughly and let it sit in an open bucket. I assume the warmer the better but most likely you are limited to whatever the current weather conditions are. I have read that if the temps are warmer (summer months), then the fermentation process will go faster. I’m not sure if you leave it in the sun or put it in the shade or does it matter?

5. When the substrate gets warm or stinky or both, mix it every day.

6. Now the hard part, trying to figure out when it’s done. I have read that when it cools down, then it’s done. However, I also read that depending on the beetle you are raising, that you may want to ferment it again so it’s very decomposed. I am not sure how you know how decomposed the wood is. By the color? The darker the color, the more decomposed or fermented it is?

7. Do you now heat treat the substrate to kill all the bad stuff? Or is this unnecessary with wood pellets?

8. If you were to make a 50/50 mix of decomposed hardwood with Oak Leaf compost, do you mix them then heat treat or heat treat them separately?

To summarize questions:

1. Is Alder hardwood ok to use?

2. How much yeast do you add?

3. Do you put in shade or direct sun?

4. How to figure out how decomposed the wood is? I have read that Rhino beetles need very decomposed wood and stag beetles not as much. So for rhino beetles, how do you know when it’s done?

5. Do you heat treat the decomposed wood and decomposed leaves separately or after they have been mixed together?

6. After making your substrate, if you have made extra, how long can it be stored and what is the best way to store it? (sealed container in a cool place, etc.)

Sorry for so many questions but I was thinking that once we have a very detailed outline of the process, we can refer other newbies like me to it.

Thank you!!

 
I've used both oak and alder and it didn't seem to have a noticeable difference.

I don't weigh my substrate ingredients and just look at it by volume. I only add about a teaspoon of yeast to about 5 gallons of substrate. You can add more, but too much and you get so much heat and carbon dioxide build up from the start that the yeast kills itself before it has a chance to get at all the simple carbs and you'll have a greater likelihood of mold and unwanted microbial growth. Too little and there won't be enough competition to reduce the chance of unwanted mold and microbial growth. Do not forget to mix the substrate every once in a while or the yeast will die prematurely and you'll end up with a really stinky mess as other microbes take advantage of the free nutrients and lack of competition.

Don't put it under sun, it'll get too hot and you'll cook the microbes you want growing in there.

Substrate gets darker and darker the more times you ferment it as cellulose gets more and more broken down. It depends on the species you're rearing, but most rhinoceros beetles prefer a very decomposed wood substrate that's easier for them to digest to the lighter colored, cellulose- rich substrate that stag beetles would prefer. The lighter it is, the more unprocessed cellulose there is.

If you're making a mix of decomposed wood with leaf compost, both need to be heat treated. It doesn't matter if they're treated separately or not. If they're going to be mixed together anyways, so you might as well do it all at once to save time.

If you've made extra substrate, I suggest letting it dry in the sun and then storing it somewhere dry and cool--keep it sealed if you don't want other critters getting into it. If you store wet substrate, you can get issues with fungus gnats and mites and it will also continue to break down over time if it's wet.

During the process of fermenting substrate, you'll probably get lots of fungus gnats and mites if you haven't found a way to prevent them from getting into it. You'll want to heat treat your substrate before you use it to avoid an indoor infestation. If you're worried about killing off all the microbes, you could mix up frass or untreated substrate in some water and strain it through a coffee filter to exclude mites and fungus gnats and use that water to introduce it to heat treated substrate to reintroduce microbes.

 
Hi Shade,

Thanks again for all the helpful information. It is really helpful and I can't wait to give it a try. I'll update you with my progress.

That's a great idea about the coffee filter. I have friends that have had bad infestations of fungus gnats flying all over the house.

Thanks!

 
First of all, it depends on the species you're wanting to rear. Dorcus species want less fermented substrate, Cyclommatus prefer more fermented substrate, and most rhino beetles want an almost soil-like substrate. The degree of fermentation depends on the amount of wheat bran that you add and the time that the fermentation process is allowed. The more additive (wheat bran, flour, etc) that you add, the more fermented your product is going to be. The 5:1 ratio sounds like it'll give you a very fermented product suitable for rhino beetles. For stags, try a lower wheat bran to oak ratio.

Now to answer your questions,

1. Is Alder hardwood ok to use? Yes

2. How much yeast do you add? I only add a small amount, about a handful for 10 gallons of substrate. I don't think this matters too much as the yeast population will reach its optimal level on by itself.

3. Do you put in shade or direct sun? I put mind in the shade with the lid on. When it's fermenting, the substrate will heat up and if there is no lid, water evaporate quickly and you'll get a dry bucket of substrate pretty soon without enough fermentation.

4. How to figure out how decomposed the wood is? I have read that Rhino beetles need very decomposed wood and stag beetles not as much. So for rhino beetles, how do you know when its done? You can't control when the fermentation is done unless you dry the substrate out. Fermentation is naturally done when heat is no longer produced and this depends on the amount of wheat bran added. If you force the fermentation to stop, you can still get the level of fermentation you want, but as soon as you add water (when you want to raise the grubs), the substrate will start to get broken down again (not necessarily fermentation but still excessive microbial action) and the substrate will quickly become too decomposed. Therefore, the key to making substrate is adding the correct amount of wheat bran/flour and just letting the fermentation process complete itself.

5. Do you heat treat the decomposed wood and decomposed leaves separately or after they have been mixed together? I don't mix leaves so I can't comment on that, but I freeze my substrate to treat instead of heating.

6. After making your substrate, if you have made extra, how long can it be stored and what is the best way to store it? (sealed container in a cool place, etc.) I would dry it as much as possible then just store in sealed containers in a cool place. I never had "too much" substrate ?

 
I just wanted to add to my previous comment on the specific ratio. Each additive is different and the condition is different at everyone's house. You'll need to play around with it and test it out. Remember you can always ferment something again but not reverse the process.

 
Hi Miwu, thank you very much for your post and your comments. Much appreciated.

You commented that you freeze your substrate instead of using heat. How long do you freeze your substrate?

Are there any advantages to heat vs freezing?

Comments from others are welcome.

I will experiment with the different wheat bran ratios and the affect of the fermentation.

Thanks,

Garin

 
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I've heard that heat treating (specifically microwaving) the substrate causes it to lose its nutrient. Someone reported larvae not being able to reach L3 when feeding on microwaved substrate. Others said that the resulting beetles were all comparatively smaller in size. I've personally never experimented with this so this is all second hand information. I'm going to bet a lot of people have used microwaved substrate without noticeable effects. I put my substrate in gallon zip loc bags and leave them in the freezer for at least 24 hours then defrost for another 24 hours. When I can (when I'm not short on substrate like I always am), I would leave it in for four to five days just to be sure.

 
The primary difference between heating and freezing is that freezing is not an effective way of sterilizing substrate and getting rid of unwanted organisms while heating can kill everything if it's done properly. Even frozen solid, some invertebrates such as mites, different types of fungi, bacteria, and other microorganisms can return to life when thawed even after a day of freezing.

It is possible that microwaving the substrate removed some beneficial organism from the substrate that help larvae obtain the nutrients they need for development, but that should only happen if you were able to sterilize the eggs and larvae before putting them into the sterilized substrate to prevent microorganisms found on the egg surface, on the exoskeleton surface, or already existing in the larval gut from coming into contact with sterile substrate.

I suspect the idea of microwaving making substrate lose nutrients stems from the idea that microwaving destroys heat-sensitive vitamins in human foods. The problem with this idea is that the substrate itself is broken down already so should not be any free vitamins except what is being produced by the microbes in the substrate. Seeing as how it is unlikely they sterilized both substrate and animals and kept the entire thing hermetically sealed to prevent microbial recolonization, the substrate should not change in nutrient quality in the long term. You're more likely to see animals fail to thrive right from the start than towards the end if this were the case.

I personally do not use microwaves to sterilize my substrate since I don't appreciate the smell of cooking substrate in my kitchen, so I can't be certain whether or not there are issues with microwaved substrate. From my experience, heat treating substrate by mixing it with boiling water has had no noticeable affect on the development of the larvae I've kept and it hasn't deterred females from ovipositing in it. Freezing substrate for days to weeks on the other hand has led many deaths from what I suspect were entomopathogenic fungi and microbes.

 
Shade of Eclipse said:
The primary difference between heating and freezing is that freezing is not an effective way of sterilizing substrate and getting rid of unwanted organisms while heating can kill everything if it's done properly. Even frozen solid, some invertebrates such as mites, different types of fungi, bacteria, and other microorganisms can return to life when thawed even after a day of freezing.

It is possible that microwaving the substrate removed some beneficial organism from the substrate that help larvae obtain the nutrients they need for development, but that should only happen if you were able to sterilize the eggs and larvae before putting them into the sterilized substrate to prevent microorganisms found on the egg surface, on the exoskeleton surface, or already existing in the larval gut from coming into contact with sterile substrate.

I suspect the idea of microwaving making substrate lose nutrients stems from the idea that microwaving destroys heat-sensitive vitamins in human foods. The problem with this idea is that the substrate itself is broken down already so should not be any free vitamins except what is being produced by the microbes in the substrate. Seeing as how it is unlikely they sterilized both substrate and animals and kept the entire thing hermetically sealed to prevent microbial recolonization, the substrate should not change in nutrient quality in the long term. You're more likely to see animals fail to thrive right from the start than towards the end if this were the case.

I personally do not use microwaves to sterilize my substrate since I don't appreciate the smell of cooking substrate in my kitchen, so I can't be certain whether or not there are issues with microwaved substrate. From my experience, heat treating substrate by mixing it with boiling water has had no noticeable affect on the development of the larvae I've kept and it hasn't deterred females from ovipositing in it. Freezing substrate for days to weeks on the other hand has led many deaths from what I suspect were entomopathogenic fungi and microbes.
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Thank you Shade for that detailed explanation. Excellent as always.

It's funny you would mention the smell of cooking substrate in the kitchen. I was microwaving substrate in batches in our microwave at the office. The gals that work in my office were not too happy about the smell. It didn't really stink but it has some kind of odor that is hard describe but it's not pleasant. I was only cooking the decomposed wood with lots of water, so I figured it would just smell like wood but it had a little bit of an odor to it.

Thanks again for your comments.

 
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Just a quick follow up question to the fermenting of wood pellets.

About how much substrate does a 20 lb bag of wood pellets make? About a 5 gallon bucket worth of it?

I was wondering because I'm trying to figure out how many bags I will need.

Thanks again for the info.

 
A 20 pound bag of pellets should make much more than a 5 gallon bucket worth. Pellets will expand when you add water to it since they're sawdust that's been compacted together with high pressure to form pellets. Expect pellets to expand to more than twice its original volume.

 
Thanks Shade, so about two 5 gallon buckets after expansion and adding the wheat bran and yeast?

Assuming 5 to 1 ratio on the wheat bran.

Thanks.

 
Thanks Shade! Much appreciated again. Well, I'm off to hopefully find some rain beetles and will try to find you a nice plump female.

 
Sorry, I think I forgot to add a step or maybe it's not needed.

After mixing the sawdust, wheat bran and yeast, do you add water in a 10 to 1 ratio?

Or is the water that you added to the wood pellets to turn it into sawdust enough water already? I made the sawdust from the wood pellets using boiling water so it's a little moist.

Just not sure if I need to add more water.

Thanks.

 
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Thanks Ratmosphere. How is your substrate doing? Have you noticed a difference between the different batches you made with the wheat bran vs the flour?

 
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