Hello! This is the discussion thread for December 🤩 to chat about Johnson-Su Bioreactors and big-picture concepts of “organic matter” - carbon-rich materials we use to build soil.
What questions do you have?
Have you ever made a Johnson-Su Bioreactor? Tell us about your experience!
Do you have any hesitations about building one - can I help by addressing any of your concerns?
What kind of organic matter do you use in your context?
After considering the different functions various sources of OM provide, what might you try adding or subtracting from your practice?
Reminder: If you make a pledge this December, I will send you a copy of a detailed guide I made for making a modified Johnson-Su bioreactor (a little easier than the more industrial design). And if you’ve already made a pledge, just reply to this message or comment below to let me know you’d like me to send you a copy.
Looking forward to engaging with you here!
PS: You may have to be subscribed to comment on this thread, here’s a link (it’s free).
Hi, Andie - I fell into Soil is Sexy this morning and, wow, I'm very impressed! I was interested in the Johnson-Su guidelines but I didn't understand what a person has to do to get a copy. Can you enlighten me?
I do have a quick question (and, yes, I'm not above becoming a paid member once I make sure this Stack is alive). I have a lot of heavy plastic 55 gal yard bags full of leaves I shredded last year and never got around to making my 2nd Johnson-su. So, the leaves have been in plastic bags that are not air tight but are certainly tied shut (ear to ear) I think most of them are dry but some may have gotten rain water into them. I've assumed these older leaves were fine for Johnson-su but I read something this morning that implied that if they don't have airflow when stored they may be 'too moldy' to use. I can't imagine such a thing but I sure don't want to build a SU that doesn't work! Your advice, please. THANKS!!
I totally get the confusion! The J-Su post you found is from last winter, when I offered a detailed how-to guide for a modified, DIY-friendly J-Su design for readers who made a "pledge" to Soil is Sexy. Today, that pledge is simply a paid subscription, and I’m happy to honor it in the same way. Thanks for your interest!
As for your question, your leaves should work great in the bioreactor even if they're a bit moldy! The only thing to watch for is if the material is too fine. For example, even though they're similar materials, wood chips are ideal for airflow in the pile, but sawdust could create anaerobic pockets, which would inhibit beneficial microbes. If you’re concerned your leaves might be too fine, try mixing them with chunkier leaves or some wood chips, and that should solve the issue.
I opened up this thread so we could include your queries where others can find them :) Let me know if you have more questions!
From Adam: What would you think about layering the reactor with a bit of azomite and or thunder garden soil for minerals.
My other question would be about adding 5% clay to the bioreactor which I understand is useful in making a humified compost. I’ve used red art clay for this in the past but wondered if azomite may be better for its trace minerals.
The other addition would be basalt dust. Thank you for all your work. I really enjoyed listening to some of your podcast materials.
The process taking place inside the bioreactor is largely a process of two things:
1. incubation – raising beneficial microbes
2. mineralization – the decomposition of organic matter, and release of soluble, plant-available inorganic compounds.
The finished product of a well-maintained Johnson-Su compost is a very humified material with a clay-like consistency and relatively high cation exchange capacity (CEC).
I can’t currently think of how adding any of the inputs you mentioned into the bioreactor would hurt anything, but I also don’t find them necessary for making a mineral rich johnson-su amendment.
Of course, azomite, basalt dust and other means of remineralization could further support a highly degraded soil and be used in combination with johnson-su amendments, so if you’d prefer adding them to the bioreactor itself I’d say try it in modest quantities and take a biological sample ~9 month mark to check in.
Lastly, my gut tells me * mixing * or very lightly dusting a mineral input in instead of layering would be a better approach. Layering minerals may prevent migration of microbes throughout a pile, potentially slowing the rate of decomposition & maturation of the microbial communities.
PS: thanks for listening to podcasts I've been on! Glad you've enjoyed them 😄
First, your substack is amazing and has been so helpful!
Our community garden is broke and so we’ve got to use what we already have. Also, I’d rather make it and have it not be perfect than have no compost at all. This is what I was thinking. Any ways to improve?
-Donut shaped
-We have a roll of galvanized 5’ tall hardware cloth and a bunch of rebar and t-posts. So the inner ring will be supported with 4 rebar stakes and the outer ring will be supported with 4 t-posts.
-I want to skip the pallet for 2 reasons: hardware cloth is flimsy and requires stakes for support. 1) Drilling holes in the pallet for the stakes to go through is time consuming; 2) would require buying new bits/hole saws.
-Alternative plan: we have a bunch of small logs and branches. Can we pile these up so the first few inches of the base of the bioreactor is made of logs to create a similar air gap? I would set the stakes first, then lay branches/logs down, then install the hardware cloth (so the inner ring would be about 3” taller than outer ring bc it would be resting on the branches and not the ground). Even if they partially decompose, it’s still some airflow/better than doing it on the ground??
-Burlap instead of landscape fabric because it’s free
-Fill with: leaves, old straw mulch, aged wood chips from a cedar elm, mushroom blocks
Oooh, thanks so much for sharing your plan here, and I'm so glad this substack has been helpful to you!
I tend to approach these things on a good, better, best scale and always within the limitations at hand and resources available - so I love to hear your creative approach and intentions to honor the design principles 👏
Below are some considerations.
Do you happen to know what gauge hardware cloth you have?
19-gauge or lower (i.e. thicker) should work fine without reinforcement. I agree that it's not worth the trouble of drilling holes in the pallet for the stakes, but want to check in on this point in the event you could make it work without the stakes.
I've only found the need to secure the cylinders on a few occasions:
- when building one by myself on a windy day
- for bioreactors that were going to be moved with a forklift after they were built
I recently bought fence staples (~$5) for this purpose btw, bc heavy duty staples weren't strong enough and using a screw at an angle has felt cumbersome and haphazard.
Generally though, the weight of a filled bioreactor will keep the cylinders in place (though you may need someone holding them during the first few minutes of filling to make sure they don't shift around too much)
My only concern with your alternative plan is that as that chunky base layer decomposes the contents of the bioreactor may start to put uneven pressure on the cylinders, resulting in a wonky / leaning or crumpled bioreactor, especially considering the "flimsy" hardware cloth. I think you'd probably still end up with good compost, but when airflow and waterflow are compromised it may take longer for the compost to breakdown and the microbiome to mature. Nonetheless, you may find that this is worth trying, and I'd respect that.
In case additional insights on pallets are helpful...
-Pallet: some have slats that are close together - within a quarter-inch or less - which is great because then it provides a truly supportive foundation without further modification and you shouldn't have to reinforce the cylinder with any kind of stakes. (If slats are this tightly packed I'd take a drill with just a basic thick drill bit and perforate the area of the inner cylinder to help with airflow).
For pallets with 3inch+ gaps, I like to add hardware cloth and / or landscape fabric on top of the pallet to provide some additional support to the cylinder so the compost doesn't fall out the base over time. When covering a pallet with hardware cloth I do NOT cut out a hole for the inner cylinder, but if I were to use landscape fabric I would cut a hole with scissors to improve airflow.
- Burlap: I'm trying this at a community project site this year that didn't want to use plastic (I get it, I don't like using plastic cloth either...) I suspect the burlap will degrade a bit, making moisture monitoring all the more important and not be able to be reused, but it seems a low-risk alternative option worth trying - let me know how it works out for you!
great feedstocks, btw! Let me know if anything else came up for you, I know that was a longwinded response 😅
Hi Ralph, I sent you a copy today (12/19) at 1:18pm (central) after receiving your pledge (thank you!) It was sent from hello@rhizos.science, subject line: Modified Johnson-Su Bioreactor Guide - if you can't find it in your inbox, check your spam folder, if you can't find it try messaging me at hello@rhizos.science :)
Can you recommend a specific landscape fabric to use for the Johnson-Su BioReactor? I want to make them to sell so I want something durable that will last many years.
Oh neat! I've tried a few different fabrics, I don't like the ones with any kind of soft fabric backing as they tend to fray over time and make a real mess of the finished product. Similarly, plastic woven fabric by itself can get unruly if it's too thin.
The most durable option I've experienced is a heavier weight woven plastic fabric, often measured in oz / sq yd, going forward I plan to use 5oz minimum, 8 oz. preferred and reuse it year after year (one of my clients does this and it seems to work great).
We're also trying out burlap at a community project site to see how it holds up, but my guess is it will breakdown too much to be reused; at least it's a natural material that I wouldn't mind getting into the finished compost - will report back :)
Thanks for the quick response. I will be making my version of the Johnson-Su reactor to sell locally for the folks that don't want to make them themselves. I made a small homeowner's version last year that produced high quality soil. I topped it off with worms and blended kitchen scraps throughout the winter to increase the yield when all was done. Here are some links for the different processes.
*Write-In Query From 'A'*
Hi, Andie - I fell into Soil is Sexy this morning and, wow, I'm very impressed! I was interested in the Johnson-Su guidelines but I didn't understand what a person has to do to get a copy. Can you enlighten me?
I do have a quick question (and, yes, I'm not above becoming a paid member once I make sure this Stack is alive). I have a lot of heavy plastic 55 gal yard bags full of leaves I shredded last year and never got around to making my 2nd Johnson-su. So, the leaves have been in plastic bags that are not air tight but are certainly tied shut (ear to ear) I think most of them are dry but some may have gotten rain water into them. I've assumed these older leaves were fine for Johnson-su but I read something this morning that implied that if they don't have airflow when stored they may be 'too moldy' to use. I can't imagine such a thing but I sure don't want to build a SU that doesn't work! Your advice, please. THANKS!!
Hi A,
I totally get the confusion! The J-Su post you found is from last winter, when I offered a detailed how-to guide for a modified, DIY-friendly J-Su design for readers who made a "pledge" to Soil is Sexy. Today, that pledge is simply a paid subscription, and I’m happy to honor it in the same way. Thanks for your interest!
As for your question, your leaves should work great in the bioreactor even if they're a bit moldy! The only thing to watch for is if the material is too fine. For example, even though they're similar materials, wood chips are ideal for airflow in the pile, but sawdust could create anaerobic pockets, which would inhibit beneficial microbes. If you’re concerned your leaves might be too fine, try mixing them with chunkier leaves or some wood chips, and that should solve the issue.
I opened up this thread so we could include your queries where others can find them :) Let me know if you have more questions!
From Adam: What would you think about layering the reactor with a bit of azomite and or thunder garden soil for minerals.
My other question would be about adding 5% clay to the bioreactor which I understand is useful in making a humified compost. I’ve used red art clay for this in the past but wondered if azomite may be better for its trace minerals.
The other addition would be basalt dust. Thank you for all your work. I really enjoyed listening to some of your podcast materials.
Good questions & ideas. Here’s my two-cents:
The process taking place inside the bioreactor is largely a process of two things:
1. incubation – raising beneficial microbes
2. mineralization – the decomposition of organic matter, and release of soluble, plant-available inorganic compounds.
The finished product of a well-maintained Johnson-Su compost is a very humified material with a clay-like consistency and relatively high cation exchange capacity (CEC).
I can’t currently think of how adding any of the inputs you mentioned into the bioreactor would hurt anything, but I also don’t find them necessary for making a mineral rich johnson-su amendment.
Of course, azomite, basalt dust and other means of remineralization could further support a highly degraded soil and be used in combination with johnson-su amendments, so if you’d prefer adding them to the bioreactor itself I’d say try it in modest quantities and take a biological sample ~9 month mark to check in.
Lastly, my gut tells me * mixing * or very lightly dusting a mineral input in instead of layering would be a better approach. Layering minerals may prevent migration of microbes throughout a pile, potentially slowing the rate of decomposition & maturation of the microbial communities.
PS: thanks for listening to podcasts I've been on! Glad you've enjoyed them 😄
First, your substack is amazing and has been so helpful!
Our community garden is broke and so we’ve got to use what we already have. Also, I’d rather make it and have it not be perfect than have no compost at all. This is what I was thinking. Any ways to improve?
-Donut shaped
-We have a roll of galvanized 5’ tall hardware cloth and a bunch of rebar and t-posts. So the inner ring will be supported with 4 rebar stakes and the outer ring will be supported with 4 t-posts.
-I want to skip the pallet for 2 reasons: hardware cloth is flimsy and requires stakes for support. 1) Drilling holes in the pallet for the stakes to go through is time consuming; 2) would require buying new bits/hole saws.
-Alternative plan: we have a bunch of small logs and branches. Can we pile these up so the first few inches of the base of the bioreactor is made of logs to create a similar air gap? I would set the stakes first, then lay branches/logs down, then install the hardware cloth (so the inner ring would be about 3” taller than outer ring bc it would be resting on the branches and not the ground). Even if they partially decompose, it’s still some airflow/better than doing it on the ground??
-Burlap instead of landscape fabric because it’s free
-Fill with: leaves, old straw mulch, aged wood chips from a cedar elm, mushroom blocks
Oooh, thanks so much for sharing your plan here, and I'm so glad this substack has been helpful to you!
I tend to approach these things on a good, better, best scale and always within the limitations at hand and resources available - so I love to hear your creative approach and intentions to honor the design principles 👏
Below are some considerations.
Do you happen to know what gauge hardware cloth you have?
19-gauge or lower (i.e. thicker) should work fine without reinforcement. I agree that it's not worth the trouble of drilling holes in the pallet for the stakes, but want to check in on this point in the event you could make it work without the stakes.
I've only found the need to secure the cylinders on a few occasions:
- when building one by myself on a windy day
- for bioreactors that were going to be moved with a forklift after they were built
I recently bought fence staples (~$5) for this purpose btw, bc heavy duty staples weren't strong enough and using a screw at an angle has felt cumbersome and haphazard.
Generally though, the weight of a filled bioreactor will keep the cylinders in place (though you may need someone holding them during the first few minutes of filling to make sure they don't shift around too much)
My only concern with your alternative plan is that as that chunky base layer decomposes the contents of the bioreactor may start to put uneven pressure on the cylinders, resulting in a wonky / leaning or crumpled bioreactor, especially considering the "flimsy" hardware cloth. I think you'd probably still end up with good compost, but when airflow and waterflow are compromised it may take longer for the compost to breakdown and the microbiome to mature. Nonetheless, you may find that this is worth trying, and I'd respect that.
In case additional insights on pallets are helpful...
-Pallet: some have slats that are close together - within a quarter-inch or less - which is great because then it provides a truly supportive foundation without further modification and you shouldn't have to reinforce the cylinder with any kind of stakes. (If slats are this tightly packed I'd take a drill with just a basic thick drill bit and perforate the area of the inner cylinder to help with airflow).
For pallets with 3inch+ gaps, I like to add hardware cloth and / or landscape fabric on top of the pallet to provide some additional support to the cylinder so the compost doesn't fall out the base over time. When covering a pallet with hardware cloth I do NOT cut out a hole for the inner cylinder, but if I were to use landscape fabric I would cut a hole with scissors to improve airflow.
- Burlap: I'm trying this at a community project site this year that didn't want to use plastic (I get it, I don't like using plastic cloth either...) I suspect the burlap will degrade a bit, making moisture monitoring all the more important and not be able to be reused, but it seems a low-risk alternative option worth trying - let me know how it works out for you!
great feedstocks, btw! Let me know if anything else came up for you, I know that was a longwinded response 😅
Please send needed info to build the A. M. (Andie Marsh) bio reactor to sfwschool.ralph@gmail.com
Hi Ralph, I sent you a copy today (12/19) at 1:18pm (central) after receiving your pledge (thank you!) It was sent from hello@rhizos.science, subject line: Modified Johnson-Su Bioreactor Guide - if you can't find it in your inbox, check your spam folder, if you can't find it try messaging me at hello@rhizos.science :)
Can you recommend a specific landscape fabric to use for the Johnson-Su BioReactor? I want to make them to sell so I want something durable that will last many years.
Oh neat! I've tried a few different fabrics, I don't like the ones with any kind of soft fabric backing as they tend to fray over time and make a real mess of the finished product. Similarly, plastic woven fabric by itself can get unruly if it's too thin.
The most durable option I've experienced is a heavier weight woven plastic fabric, often measured in oz / sq yd, going forward I plan to use 5oz minimum, 8 oz. preferred and reuse it year after year (one of my clients does this and it seems to work great).
We're also trying out burlap at a community project site to see how it holds up, but my guess is it will breakdown too much to be reused; at least it's a natural material that I wouldn't mind getting into the finished compost - will report back :)
Would love to stay updated on your fabric making!
Thanks for the quick response. I will be making my version of the Johnson-Su reactor to sell locally for the folks that don't want to make them themselves. I made a small homeowner's version last year that produced high quality soil. I topped it off with worms and blended kitchen scraps throughout the winter to increase the yield when all was done. Here are some links for the different processes.
https://www.youtube.com/watch?v=4zExGEm-c8I
https://www.youtube.com/watch?v=cI0DhTt8fmw
https://www.youtube.com/watch?v=qsS1JMd61gI
Very cool, love the idea of a kit or anything to make it easier on folks to make great compost and improve soil health 👏 thanks for sharing!