Early in August I put together a podcast (and written version) featuring my response to “Tim S.”, who had written in with lots of interesting questions about the potential for setting up a worm farm and castings operation on a 2 acre plot of land.
You can find that blog post here: “2 Acre Low-Maintenance Castings & Bait Worm Operation?” (and I recommend going through it before proceeding with this post)
Well, it seems Tim really appreciated the response…but found that it led to even MORE questions about all of this!
I decided I should post the follow-up responses here as well. Below you will find Tim’s additional questions (in bold) along with my answers directly below each of them.
1. First, does your advice to steer clear of casting and bait production change when I tell you I can get a Patz vertical feed mixer, and 200+ tons a month each of cardboard and purina dog food waste (dog food paste, high in both C and N) from the local factory? I could mix these with leaves, lake weeds, and woodchips to form windrows and feed them once or twice a week. I also have an ample water supply, and compostex covers.
Wow Tim – sounds like this has the potential to be a very serious project!
I guess my response now would be my tried and true “it depends”!
Again, I would strongly urge you to start by looking into local regulations about this sort of thing. Starting a little eco-farm is one thing – but once you’re dealing with many 100’s of tons of waste materials (especially stuff like dog food waste), it’s a whole other ball game.
Assuming you were licensed (etc) to work with all those wastes, my suggestion would be to create very serious hot composting windrows first. Either fully compost the wastes (thermophilically) and simply market the finished product, or “precompost” your mixture (maybe for a few weeks) and then feed it to composting worms for final processing.
With a material like dog food waste, hot composting would be critical since there would be a very high potential for heating, ammonia release, and fly infestation.
Environmental factors would still be a major consideration – especially with castings production. If you were able to at least erect some form of shelters over the windrows that could help a lot. And my hunch is that by law you’d probably be required to do the composting on concrete pads, which would also make a big difference.
2. Is there a problem with my feedstocks? Will it be hard to screen out the castings? I know that many successful operations have very uniform inputs (manure, peat, etc)
Uniform feedstocks definitely help a lot, but I don’t see why you couldn’t just screen the bulky stuff (assuming you can keep everything from getting drenched – again the shelters would help with this) and just recycle it back through the windrows.
3. If Im feeding the windrows in thin layers on a weekly or biweekly basis, should I be concerned about fresh materials heating up? Is precomposting absolutely necessary if I keep the C to N above say 30:1?
Again, with a material like dog food waste I would say that, yes, precomposting would be needed for sure. Even if you’re not using the dog food waste, precomposting would probably help a lot, since it should make the mixture a bit more “worm-ready”. And yes, there is also the heating issue to consider – even large heaps of high C:N wastes tend to go through some form of heating phase.
You should be fine to layer your precomposted stuff on the vermicomposting windrows without the risk of any further (serious) heating taking place.
4. Could I harvest the entire windrow and screen the material out, or would you suggest using a wedge (walking windrow) method?
I really like the wedge concept – at least as far as your vermicomposting windrows go. This way the worms have a safe habitat zone regardless of what’s happening in the wedge zone. Plus it’s more of a “continuous” method so once you’re able to do your first harvest, you should be able to then continue harvesting more frequently.
That being said, harvesting entire windrows can work well too. It would probably leave you with a larger batch of vermicompost that’s more uniform in consistency – and you’d also be able to harvest more worms at once. But it would require more patience (waiting until entire row is finished), and you’d need to stagger the start up of your windrows if you’re after a continuous supply of worms/castings.
5. If you were planting on the side of the windrows would you plant into, or next to the material? And would you till the soil first?
I would plant in the soil right next to the windrow. It’s better if the plants have a sort of “safe” zone for their roots that they can then expand out from. Since roots WILL eventually grow right into the windrow, you probably don’t have to worry too much about tilling the soil.
Hope this helps!