When most people think of vermicomposting, they think of starting up some sort of typical “worm bin” – often a fairly small system kept indoors or at least inside a garage or shed. Backyard composters aren’t often thought of as ideal vessels for the process.
In all honesty, the way many people seem to set-up and use their backyard composters, they absolutely aren’t the ideal “home” for Red Worms. Whether they’re using them as a garbage can for sod, grass clippings and/or bulky yard wastes, or simply failing to maintain them properly, the likelihood of them having any sort of composting success with these systems is pretty low, let alone being able to turn them into a lean, mean vermicomposting machine!
Well, the good news is that your typical medium-scale backyard composter – whether its an “Earth Machine”, a “Soil Saver” or really, any other commercial or DIY bin – can actually serve as a fantastic outdoor vermicomposting bin!
One caveat I should mention right off the bat though! I can’t promise that this will necessarily be the case in every location and climate! Somehow I suspect that it might be difficult to use an Earth Machine as a vermicomposting system during the summer in Texas, for example. But I think it’s safe to say there are ways to make it work pretty well anywhere in the mid-to-northern temperate zones of North America (and similar climatic regions around the world).
As you might imagine, there are some important considerations to keep in mind when planning to add Red Wigglers to a composter. Rather than obsessing over C:N and “browns” & “greens”, it’s helpful to think in terms of “habitat” and “food”. Since we are all well-versed in the fundamentals of vermicomposting (right? haha) we know that composting worms need a habitat that provides moisture, oxygen, and warmth (but not excessive heat) in order to thrive. We also know that they need to have access to lots of rich, microbially-active “waste” materials for sustenance. If we can provide all of these requirements, while avoiding some of the hazards, such as excess ammonia volatilization, we are good to go!
The beauty of these bigger outdoor systems, as compared with our run-of-the-mill “worm tub” type of systems is that they tends to have much better air flow, and a much larger “buffer zone” for the worms once you’ve established the “habitat” – so they can be a lot more forgiving. During warmer times of year these systems can produce better vermicompost faster than some of the more traditional worm composting approaches as well!
OK – let’s start talking about how we do this…
The very first step I recommend – and this one is very important in my humble opinion – is to dig a decent sized pit down below where our composter is going to sit. Make sure to keep the diameter a fair bit smaller than the lower diameter of your bin, and dig it to at least 10-12″ deep. This is basically going to be our “worm safety zone” – even if you don’t plan on actively vermicomposting, it’s beneficial to set up this zone since the native soil worms will thrive there, and you’ll leave behind a nice rich deposit of material if you decide to re-locate your composter at some point (composter rotation can be a great way to fertilize different parts of your yard).
Fill this pit solely (or at least mostly) with some sort of absorbent, neutral bedding material. My favorite choices include shredded corrugated and “egg carton” cardboard. If you soak your cardboard in a bucket of water (something you should have on hand for the set-up process anyway) it will be much easier to tear and will be nicely moistened for the worms!
This pit will serve as a cooler zone during the heat of the summer, and a warmer zone once the weather gets cold – helping to ensure that our wiggler population is able to survive in the system all year.
On top of this moist bedding zone I recommend adding some good “food” materials for your worms. In the case of this system, I added coffee grounds and a nice “homemade manure” mix I’d recently mixed up using multiple bags of frozen food waste (among numerous other things). This way you basically have an active vermicomposting pit, and the worms can choose to move upwards from there as they see fit. As such, if we are planning to add the worms the same day we set up the bin – this would be a good time to add them. I generally recommend adding the worms a week or two later though (if still hot above, you should be able to add them to the pit zone via the compost access door at the bottom).
Moving upwards from the pit, my general recommendation is to set up the bin in a typical “lasagna” fashion. Alternate thin layers of “browns”, “greens” and a sprinkling of “living” material (coarse compost, rich garden soil, well-aged manure etc), making sure to moisten each time the three have been added.
Adding moisture is very important, but so is moisture retention (more so in a vermicomposting bin than in a regular composter), so make sure you include some absorbent materials (like shredded cardboard) among your browns. Bulky browns are also really beneficial as well, though, so I recommend adding some chopped up dry plant materials – even some woody wastes if you happen to have some on hand. These types of waste are excellent for increasing air flow in the system.
Even with a basic set of hand loppers you can make short work of a heap of bulky, fibrous/woody waste material – I recommend using them for all plant materials that go into the bin! Remember – we are trying to optimize for microbial colonization, and the greater the available surface area, the faster (and in greater abundance) the microbes will set up shop. This also helps us to get much more material in the bin!
Once you are up past the soil level it will make sense to put your composter in place over top of your pit – now you’ll be able to add quite a lot more material while still keeping your layers thin!
As you continue upwards, it’s not a bad idea to periodically mix your layers a bit using a rake or garden fork. This will really help to kickstart the composting process and establish the early “heating phase”.
Again, don’t forget about that watering can! Doing all your moistening as you go will be MUCH easier (and more effective) than trying to water down a mostly-dry system once it’s set up!
How much material you add initially is up to you. If you DO have enough to fill the bin, you may want to do so – if set up the way I’ve described, over the course of the next couple of weeks the materials should settled down quite a bit anyway. I recommend topping everything off with a nice thick layer of straw or some other carbon-rich cover material (shredded newsprint for example). This will help to keep moisture in (especially important if there isn’t a lid on your particular bin) and flying pests out.
If you have a long-stemmed compost thermometer, I recommend monitoring temps during the next 1-2 weeks. As mentioned earlier, even if conditions are still pretty hot up above (35 C / 95 F +) you should be able to add composting worms via the compost door at the bottom (but do check temps in the pit just to be sure).
Once you have a nicely “pre-composted” habitat zone, the worms should start moving up and processing these materials quite readily. Moving forward – while I still recommend adding materials in the same manner as described above, if you DO decide to get a bit lazy (dumping more than a “thin layer” of grass clippings for example – haha), your worms should have a nice protective buffer zone by then that will help to prevent them from being harmed!