Turning Large Bins
Question
June 22, 2020
I have a few compost questions I was hoping the master composters could help with. I was recently charged with managing the compost bins for the community gardens at the Rio Grande Community Farm (at 87107). We currently have a three bin hot compost setup. There are more details about the setup below, but my questions are:
1) the bins are quite large — around 6’ x 6’. How do you turn hot compost piles this big? I was working with a master composter before she moved out of state, and she said you just rebuild the entire pile. But how would that work exactly? Do you try to maintain the layers with the bulking in between? Do you add anything? Is there a better way than rebuilding the piles?
2) If a pile gets cold because we were unable to turn it while it was still warm, is there any sense in still turning it? Or should we just sift it and add anything that didn’t break down into a new pile?
Our set up is three wire bins, each around 6’ x 6’. Currently they are lined with cardboard, though I’m going to experiment with lining them with plastic tarps instead. They are in the shade in the morning, but in the sun for the afternoons. All piles are covered on top with cardboard and a plastic tarp. For each bin, I’ve dug about a foot underground to help with runoff. We end up needing to water the piles once a week or so due to the afternoon sun. I am also new to hot composting, though I have a handle on the basics (and attended the basic home composting class before the pandemic).
Thanks so much for any help you can provide! We have a lot of organic waste and go through compost really quickly. Plus a lot of the gardeners are really fascinated with the compost process!
Answer(s)
Answer by JZ: Your questions will be received by a few of my colleagues, who may also respond. Great to hear that you have a fine composting setup.
1&2. Hot composting piles may be turned every 7- 14 days, if you have time to do that. If the setup is already bulked with coarse material, then more bulking does not need to be added, it will be blended in as you turn. When you turn, then the top becomes the bottom and the sides become the inside, so then as you continue the process all areas will be exposed to the core heat. You turn them with a pitch fork, flipping from the full bin to the empty bin.
Add water as necessary. If pile is below 130F, then you may add more nitrogenous material - greens which will encourage microbial growth, producing more enzymes to break up the carbohydrates thus releasing heat energy.
2. Cold composting is a useful decomposition method, high heat is not necessary for decomposition to occur as long as moisture is maintained and you bulk as you build your cold set up will decompose to humus.
3. A pile is sifted after the main portion has decomposed to humus, which looks like coffee grounds and is mostly at the bottom of the bin.
4. If you have afternoon sun, then you could double drape the whole setup with 2 layers of shade fabric, or large cuts of cardboard.
5. Wire bins may be from 1 cubic yard or bigger for hot composting, for cold composting they could be any convenient size. So you could keep your bins as they are or reduce their size to 3' x 3’x3’.
6. You elevate any bin by putting an appropriate sized palette under it. The top of pallets may be covered with weed barrier fabric, which would allow for drainage, but keep the contents from dropping thru the slots.
You are welcome to read our desert composting brochure, which I think would be helpful. See Desert Composting under Composting Info in our website menu.
I have been to your garden a few times in the past to discuss composting with volunteers. I could do that again if you are interested - outdoors, with face masks, socially distant. Hope this is helpful. Best.