built a johnson-su composter, modelled after dan's design and with modifications of my own

Thermophilic composting is the practice of breaking down biological waste with heat-loving bacteria.
troy
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i started building a johnson-su composter, modelled after dan's design, but with a few modifications of my own... mine is about 4'x4'x4' and will have a hinged skylight as the cover. i plan to build removable slats to access compost from the front. luckily, i was able to gather enough used supplies ( wood salvaged from scaffolding, pallets, fence; skylight; 4" perforated pvc drain pipes; hinges ) to build it, otherwise it would have been a rather expensive build...

check out my youtube video below...

https://youtu.be/5poHn4Jyqn0

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finished johnson-su composting bioreactor
finished johnson-su composting bioreactor
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Last edited by troy on Tue 29-Mar-2022, 18:17, edited 18 times in total.
Danoost
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Very nice. Does yours bring in fresh air from the bottom? It's best to circulate fresh air through the pile. One of the shortcomings of mine. Will you be pulling the pipes out a few days after it's loaded?
PeasIntheRain
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It's very beautiful especially for something built from used components!

I'm curious about why it has a wooden floor (that is, a floor at all). To my understanding, the only reason to have the sides is for aesthetics and a lid is to protect the compost from the excessive rain we have in this region, which can wash away more nutrients than we'd like to lose. Did you have specific reason for not just having the compost pile on the ground, which would reduce the materials required for the bin and increase the ease of drainage, if there is excess water?
troy
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PeasIntheRain wrote: Thu 17-Mar-2022, 11:08 It's very beautiful especially for something built from used components!

I'm curious about why it has a wooden floor (that is, a floor at all). To my understanding, the only reason to have the sides is for aesthetics and a lid is to protect the compost from the excessive rain we have in this region, which can wash away more nutrients than we'd like to lose. Did you have specific reason for not just having the compost pile on the ground, which would reduce the materials required for the bin and increase the ease of drainage, if there is excess water?
thank you and great questions. i have limited space in the garden and may move it at a later time. having a floor may deter animals that could get into the bin from below, and makes it easier to move. i modelled it after dan's design, which he uses as a hotbed/mini greenhouse to facilitate seed germination. if you look behind andrew, there is a cover made from a framed sheet of glass which allows sunlight in. the boards on the bottom are loose and have space between them, which allows for drainage. after dan's comment about bringing in fresh air from the bottom, i'm thinking about cutting round holes into the floor planks for the perforated pipes to sit into.

also, i may use it as a large vermicomposter. andrew recommended a minimum 4'x4'x4' sized container to help composting worms survive our winters.

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troy
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Danoost wrote: Thu 17-Mar-2022, 09:38 Very nice. Does yours bring in fresh air from the bottom? It's best to circulate fresh air through the pile. One of the shortcomings of mine. Will you be pulling the pipes out a few days after it's loaded?
thank you dan! i am thinking about cutting 4" holes through the floor boards to allow the perforated pvc pipes to bring in fresh air from the bottom. i may drill more holes into the pipes to increase ventilation and just leave the pipes in there. what do you think?


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troy
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made a bit more progress today. i cut out holes in the floor for the 4" diameter pvc pipes and drilled more holes into the pipes for better air flow. i will use 1/4" hardware cloth at the bottom of each pipe to keep rodents out.

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troy
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built channels for slats that can be used to open and close the front of the composter, which will make it less of a hassle to harvest compost. i learned from dan's zoom webinar today that this composter is called a johnson-su composting bioreactor... thx dan!. the salvaged skylight i'm using as a lid, is rather heavy and i may have to install a couple of struts to help with lifting. so far, so good...

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troy
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mounted the hinges today and it's almost done! as you can see, there are slots which allow boards to slide in and out... accessing compost will be a breeze. i just have to rig up something to hold the heavy lid open and then it'll be done!

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troy
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installed a couple of articulating arms to keep the lid open when wanted, and lined the walls with landscape fabric. almost done!

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troy
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it's done! i added a galvanized brace with cotter pins to preserve the shape of the box while under expansive lateral loads. since i didn't have enough carbon inputs, i skimmed some woodchips from pathways. i also added grass clippings and turkey compost as my nitrogen inputs.

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Last edited by troy on Tue 29-Mar-2022, 23:18, edited 3 times in total.
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