In a very real way, worms and other soil life are the only animals some people will interact with on a small urban scale. This is changing, albeit slowly, with limited pilot projects springing up even here in Toronto for things like backyard
chickens. Still, in my opinion, worms, and in a larger sense, soil life farming is the most solid base for any scale venture.
For situations where my space is not connected with the soil, I would also use a top-feeding system, probably with a few different sizes of screen between sections, allowing the wigglers to move up and down the column, with an exclusionary (for adults, anyway) bottom screen above a drawer for finished worm castings, sloped towards a drain.
I think, especially in the event I had some backyard hens, that I would incorporate black soldier fly larvae into a topmost bin, with a feeder tube leading to the
chickens' coop, or to a live storage trap for later feeding. While they don't like to be in the same soil, it appears that red worms like the enzymes left behind by black soldier fly larvae. This would solve the problem of food rotting away, and would likely facilitate the worms' feeding and digestion, accelerating the process and likely increasing the healthy stocking rate within the same space.
I also think that, in a space with size limitations, especially with the practical consideration in mind that, of all the other small-scale animals available, the
chicken will likely be the first choice for most who will keep urban livestock, other organic matter upcycling techniques might be considered.
There are at least two more insect options here, creating a high-protein foodsource from foodscraps, those being mealworms and crickets. The idea here is essentially to create a setup where scrap organics are fed to either mealworms, crickets, or black soldier fly larvae and then worms, creating worm castings and frozen whole insects suitable for grinding into meal for human entomophagy (not my personal favourite) or for feeding fish and chickens.
I think the best use of resources in an urban environment for a backyard farmer is to set up an insect-based organic scrap conversion system, preferably soil-linked, and then mine the urban waste resources, preferably making arrangements with
local grocers and
coffee shops/houses, and microbreweries for their spent grains, if you can get them, rather than dumpster-diving, with the end stage for all waste before the garden being vermiculture.
In what I have just laid out are the kernels for several waste-stream-based revenue streams for urban backyard farmers, and the work involved would be no more, really, than what a backyard hen keeper might go through for their chooks.
I have to agree that vermiculture is an integral component in any soil farming endeavour, but I think that, in terms of delivery, oxygenated compost extracts tailored to the specific crops being grown might be a tool integral to the priming of soil for vibrant vermicultural health. Worm castings would definitely play a large role in my extract recipe, but I would probably also add fresh rabbit droppings (I have a rabbit) for the bacterial content,
mushroom slurry, and tailor the rest of the recipe to aim for a balanced bacterial/fungal balance in the soil, barring some specific need for a skew one way or the other.
I think an intensive, multi-layered system on a backyard scale would ideally feature chickens, to take direct advantage of the BSFL stage before the worm bins. They would fertilise as they went, providing more food for the worms in the soil.
Lastly, worm castings are a great component of soil, but I think that for the soil to truly be improved, you need to have living
root systems running through it, with a complete soil food web.
I think the best way to go for home gardens and small urban farms is a comprehensive, inclusive system that uses as many of the tools and techniques mentioned above, and likely dozens I haven't mentioned, suited to individual circumstance, but generally upcycling urban food waste to animal and human food, and to food for soil life to make more soil life.
-CK