The Boxwood Vermicomposting System
Note that this article duplicates “Raising Earthworms to Feed the Flock” in the section Cultivating Decomposers as Poultry Feeds. Since the article is not restricted to worms as poultry feed, and since I have encountered nowhere the same approach to composting with earthworms that we have put in place, I present it here as a description of our basic setup and management.
Note as well that in recent years I have abandoned the vermicomposting model presented below, though I present it here because it has much to offer for producing live worms and castings at larger scale. I have included the description of my alternative basement model in the revised edition of my book The Small-Scale Poultry Flock, which I am told should be published in September 2022.
Regular visitors to this site know I am always looking for integrated patterns in which one element in the homestead, food-self-sufficiency enterprise supports and enables another; in which problems transform into benefits; and in which the homesteader finds unexpected synergies—that is, biological efficiencies that surpass in sophistication and beauty the crude “efficiencies” of machine and chemical agriculture. There is no better example of integrating efficiencies than the vermicomposting bin.
Using earthworms as our allies, we can practice responsible management of manures (from either our own livestock or that of neighbors), turning what is otherwise repellent and a potential vector for disease or parasites into “black gold” for garden fertility applications. But we can pluck one more benefit from this magic trick: We can harvest worms from a vermicomposting bin as nutrient-dense feed of the highest quality for our flocks. Let me tell you about the vermicomposting operation I’ve put into place, and how I harvest worms for poultry feed.
Vermicomposting in the Greenhouse
There are many options for setting up an effective vermicomposting operation. However, worm bins in exposed spaces are apt to stay close enough to freezing in colder climates that the worms’ activities slow down to a minimum in winter. On the other hand, bins in enclosed, heated spaces (such as the basement) are apt to be too limited in size. The great beauty of setting up the operation in a greenhouse—assuming you dig the bins into the earth for maximum protection from temperature extremes (summer or winter)—is that there is never a dormant period in the composting cycle. However hot or cold the ambient temperatures, the worms in their earth-protected bins continue to feed and reproduce.
In the Fall of 2005, I replaced the rotting foundation boards of my 20×48-ft greenhouse with 4-inch concrete block. I had been practicing vermicomposting in a 3×4-ft “trainer wheels” bin for about four years, and saw the greenhouse renovation as the ideal opportunity to step up to more serious work with worms. We dug out a space for vermibins, 16 inches deep, 4 feet wide, and 40 feet long, right down the center of the greenhouse. Since I needed that central access anyway, I didn’t lose much growing space to the new bins. (Do note the dimensions if thinking about a similar project: That’s a lot of dirt! Plan ahead for creative uses of all that fill elsewhere on your landscape. And plan on a lot of good wholesome exercise, digging and hauling.)
We lined that space with 4-inch hollow concrete block, two courses deep. Every 8 ft of the 40-ft length, we placed a cross-wall of blocks. The result was a series of five 4×8-ft bins, 16 inches deep.
We made lids for the bins from ¾-inch plywood on 2×4 framing. The lids are heavy-duty enough for the heaviest loads, and have been a great place to lay out work projects requiring a flat surface. However, a single 4×8-ft lid (i.e., one made from a single sheet of plywood) with such hefty framing would be too heavy to move conveniently. Therefore we made each lid a more manageable 4×4 (one sheet of plywood cut in half). The result was two lids over each 4×8 bin, creating for management purposes two 4×4 sections per bin, but with no partition between them. Remember that concept—it is the key to some of the management practices we’ve come up with.
Note that there is no floor in the bin other than the packed Virginia clay with which we are blessed. This is not a problem, given the species of composting worm we work with (about more of which below), and the fact that our clay soil drains well despite its compaction. Note also that our block-walled bins inside the greenhouse have had no incursions of worm-loving moles (which are sometimes a problem for worm bins outside).
In some discussions of vermicomposting, you will see a distinction between “bedding” and “feed” for the worms. In my bins there is no such distinction: With one exception (see below), I fill them with “pony poop” exclusively—pure horse manure from a neighbor who breeds and boards horses. Note that qualifier “pure”: If the manure is mixed with hay, straw, or pine shavings, it will heat up, just as in a compost heap—a disaster for the worms. Pure manure will not heat up, or only slightly so. It is an excellent medium for the worms. They live in this medium (using it as bedding) while converting it (using it as feed) into castings.
Manure of ruminants—sheep, goats, llamas—all make excellent worm feed. Cow manure should work fine as well, though its higher water content might require some changes in management. I know of one huge and quite successful vermicomposting operation in North Carolina (home of a lot of high-confinement pig operations) based on pig manure. Rabbit manure has also been used for worms, sometimes with the bins directly beneath the rabbit hutches ready to take “incoming.”
It is not impossible to use poultry manure to feed worms, but it is quite potent—high in nitrogen, and likely to heat up and generate ammonia. One could make periodic applications that are very thin, or could pre-process poultry manure in a compost heap until it is past the heating phase. Since such procedures make the operation more labor intensive, I stick with manures that are easier to use, reserving poultry manure for other fertility-recapture strategies.
Note that other materials can be used for worm bedding and/or feed: shredded newspaper or cardboard, weeds or crop residues from the garden, kitchen scraps, and vegetable trimmings, etc. I maintain one bin in which all contents are of plant origin exclusively. The worms process this material as well but take much longer to do so.
(A technical note: The worms themselves do not actually “eat” the feeds we offer them. Rather, a whole host of bacterial species “eat” the organic feeds in the bins, and the worms feed on the bacteria.)
Worm Species to Use in the Bins
If you’ve ever dug into the center of an aged heap of manure, you saw “red wrigglers” or “manure worms” at work. It is this type of worm—not the soil burrowing “night crawler” earthworm types you find when digging a garden bed, or in a bait shop—that is used in the rich, dense feeding medium typical of the vermicomposting bins. (Eisenia foetida is the species normally used.) This type of earthworm will not burrow down into the compacted soil under the bin, nor will it crawl out the top of the bin. Conditions in either direction are not as compatible, as inviting, as the rich feeding medium we establish in the bin.
Setting Up the Bins
For me, the vermicomposting process starts with hauling in pickup loads of horse manure from my neighbor’s place, and loading all five bins. (There’s plenty available in the state legislature as well, but that’s a longer haul for me.) I adjust the moisture content if necessary, using a wand on a garden hose, aiming for a medium that is neither uncomfortably dry for an animal whose entire body is covered with a wet skin; nor sopping wet, a condition that would drown the worms. Before watering, I check the deeper levels of the bin, not just the surface. Over-watering at the surface can cause a hidden accumulation of excess water deeper down, especially if drainage from the bin is poor.
After waiting a couple of days to ensure there will be no significant heating, I inoculate the bin with worms. You can easily find them for purchase online. They are expensive, but you only have to buy them once—after that, they will “be fruitful and multiply,” and you should then have enough for all future needs. Alternatively, you could visit the aforementioned aged manure heap and dig out a “seeding” of manure worms for your bins.
In either case, it will take some time before your bins are fully populated. Be patient. If you check from time to time, you will find more and more red wrigglers—and their small round yellowish egg capsules as well—signs that indeed they are achieving their and your mutual objective. I seeded my five 4×8 bins (a huge amount of material) with worms from my small “trainer wheels” bin, and it was about a year before I could start harvesting earthworms as surplus.
Managing the Bins
At the beginning, the horse manure is in the form of the “horse apples” or “horse muffins” so familiar to anyone attending a Fourth of July parade. At the end of processing, the horse manure has been converted entirely to worm manure, or castings—a fine-grained, moist, black residue that is one of the best of all-natural fertilizers (not only for its mineral components, but because it carries a huge load of beneficial microbes added in the gut of the earthworm). Unfortunately, a bin that has gone to pure castings has no living worms—no animal can live in its own wastes (as we humans are finding to our dismay).
Thus the trick is to find a way to furnish an ever-renewed source of food for the worms, while separating them from the castings. There are numerous techniques that have been used for doing so, some of them quite tedious and labor-intensive. I don’t do tedious and labor-intensive, so will tell you the alternative which works well for my needs.
First of all, as the worms work the manure, they reduce its volume. At some point, it is possible to shovel all the bedding from one half of the bin on top of the material in the other half—and still have it fit under the bin lid.
Remember how I said that having two lids allows us to manage a single 4×8 bin in effect as two 4×4 sections (but with no barrier between them)? Now we begin to see what an advantage that is: We fill the emptied half with fresh pony poop. Note that at this point it no longer matters if we have some initial heating in the new material—the worms are safe in the older, established material, and can simply wait out the heating cycle before starting to “sip” at the edges of the new bedding. As they exhaust the old material, they migrate into the fresh material, leaving behind pure castings for our use, but maintaining a thriving population in the fresh half. We have now established a sort of seesaw for managing a perpetually renewing vermicomposting cycle. Ain’t natural systems beautiful!
Harvesting for Feeding
There is a final refinement to the cycling of manure used in this system, however, and that is the point of this article: We can harvest the worms to feed chickens (and ducks, guineas, turkeys—all domestic fowl except the vegetarian geese, who are appalled). To do so, we intervene in the cycle at what I call the “halfway” point. Remember the beginning of the cycle (discrete, clumpy “horse apples”) and its ending (even textured, fine-grained castings). Midway along the spectrum is the halfway point: The worms have pulled apart the manure clumps into an even mass with plenty of fiber still in evidence. That is, the material has been broken down, and infused with castings, sufficiently to use as a potent fertilizer, but still contains plenty of worms and worm eggs. At this point, we can intervene with shovel and bucket—scoop up the fibrous bedding and feed it to the flock.
In the winter, I release my birds onto the heavily-mulched “winter feeding yard” described elsewhere on this site. Since the mulch is over one of my gardens, I simply dump the bin material with its load of worms onto the mulch (a different spot each day, in order eventually to benefit the entire area). The chickens scratch the processed manure into the mulch while dining on the worms.
Another option in the winter is to dump the bin contents onto the deep litter in my greenhouse poultry pens or in the main poultry house. Again, the birds incorporate it into the deep litter. Periodically, I remove the litter—now something like a mix between a finished compost and a mulch—and lay it down in a heavy layer in my “fertility patches” of comfrey or stinging nettle, both capable of utilizing all the fertility I can throw at them. Later in the gardening season, I could use it instead to mulch heavy feeders like corn or winter squash.
In the summer, the “halfway” bedding can feed chickens on the pasture. Sometimes I reserve the worms harvested from the worm bins to help meet the higher protein needs of the growing birds, using a shelter set up as a sort of “creep feeder” to serve the young birds while excluding the adults. Of course, I will keep the shelter moving over the pasture in order to even out the fertility application of the worm bedding.
I have a couple of times seen caveats that worms raised in animal manures can pose a threat of disease if fed to chickens. I have been unable to find any substantive discussion of this subject. For this reason—and because I know of so many real-world applications in which chickens have been successfully fed or released onto manure-fed earthworms—I am not deterred by theoretical possibilities. Vermicomposting is proving to be a source of high-quality feed for my flock, and I won’t be concerned about potential problems until and if they manifest.