The Call and Times, Column 24 – The Art and Science of Vermiculture

7 08 2015

(July 5th, 2015)

The Urban Farmer

The Art and Science of Vermiculture

It’s an understatement to say that topsoil is the glue that holds the Earth together. But how it is formed? We’ve dug deep into the mysteries of topsoil, explored natural material cycles, and discussed organic methods for soil fertility. But one aspect of this amazing substance that we haven’t really covered is the little creature responsible for making it: the humble worm.
Consider this your first and only warning – this column is about worms, and the steps that an urban farmer can take to make more of them. If you, like my grandmother, are squeamish about this topic, it’s best to put the newspaper down and go for a walk. I’m just kidding – there are dozens of them in each square foot of the ground you’d walk on, so it’s best just to continue reading.

In today’s column, I want to introduce the simple but powerful art of “vermicomposting” or “vermiculture”. This isn’t nearly as complicated as the technical names imply. Vermiculture leverages the natural tendencies of worms to create rich compost and more worms. For the urban farmer, this means putting some worms and organic material in a box, and letting nature do the rest.

The construction of a vermiculture system (a “worm bin”) is quick and inexpensive. Minimally, you need: a 10 to 20 gallon plastic tote box, preferably 12-18 inches in height, with a tight-fitting lid; a second tote or a tray that the first tote can fit into, with high enough walls to hold a few inches of drainage liquid (called “worm tea” – though I wouldn’t recommend drinking this); two bricks or wooden blocks; and a drill with a small drill bit (1/16th-1/8th inch).

To construct the bin, first drill some small holes in the bottom of the tote, separated by a few inches – 20 to 30 in total. If the tote is uneven along the bottom, make sure to drill at the lowest points. These will provide for drainage.

The lid of the bin needs to be tight-fitting, to protect the worms from bright sunlight and rain. In the lid, you need to drill around a dozen ventilation holes, a little larger than the drainage holes. Alternatively, you can cut a small (postcard sized) rectangular hole in the center of the lid using a utility knife, and attach a piece of screening (i.e. an old window screen). Glue generally doesn’t bond to this type of plastic, so my preferred method is to drill small holes along the outside of the ventilation hole and use plastic zip ties, string, or wire to tie the screening to the hole. This method is more complicated, but I believe it makes for better ventilation.

That’s basically it. You put the bricks or blocks into the tray and set the plastic tote on top of them, so it won’t be submerged in the tea. I used a second plastic bin, so the drainage holes would be protected from direct exposure. Now, it’s time to fill the bin.

First, line the bottom (of the main bin) with a few inches of high-carbon bedding material. This could be shredded paper or cardboard, peat moss, or shredded leaves – I used half newspaper and half leaves. You need to wet the bedding material enough that it absorbs water, so that it’s comfortable for the worms. On top of this, put a few shovelfuls of garden soil, just enough to cover the bedding. This introduces beneficial microbes to the bin, as well as non-biological, which aid in worm digestion. Finally, you add in your worms and some food (more on this below), and a piece of wet paper or cardboard across the top to keep the bedding and vermicompost from drying out.

Traditionally, the types of worms used in vermicomposting are red wigglers (Eisenia foetida) or red earthworms (Lumbricus rubellus), which thrive in high-organic-matter environments. It is possible to harvest these by hand, in dark, damp areas of your yard, where leaves and leaf mould cover the ground – but this is time consuming. Red wigglers can be purchased online, from many garden stores or even Amazon and EBay, or you can find a local vermicomposter in your area (Craigslist is a good place to start) who will be dividing their worm bin and would sell some to you. I got my red wigglers from a friend who vermicomposts.

Worm bins are capable of digesting most organic materials. Favorites include most vegetable and fruit wastes (with the exception of citrus and any plant in the onion family), coffee grounds with the filter, tea bags, and starchy leftovers (better used to grow the worm bin than the vermicomposter’s belly). Fat and oil, bone, dairy, and meat scraps can added as well, but should be a small portion of the total food input.

There is essentially no day-to-day maintenance of the worm bin. You should make sure the contents stay damp (not soaking, but not dry), and feed the bin only as fast as the food is digested. The first few weeks will be slow going – the worm population starts small, and it takes time for microbial populations to colonize the bin (and these are actually what the worms feed on).

The bin should be placed in a shady area – a basement, garage, or shed is good, or a cool, shady alcove outside. You don’t want it in direct sunlight, which makes the worms uncomfortable, and can heat the bin. The optimal temperature range is around 50 to 80 degrees, which means that special attention should be given on hot summer days. The worm bin must be put inside during the cold of the winter if you want the worms to survive (it doesn’t smell and is indiscriminate).

So why would an urban farmer want to go to the trouble of growing a box of worms?

Vermicomposting is faster than regular composting, and merely through their digestion, the red wigglers turn organic materials (and even ordinary topsoil) into worm castings – a valuable soil fertility amendment that is even better than compost. Castings should be extracted from the bin by moving the contents over to one side and filling the other with new bedding and feed. The worms will slowly migrate to the new organics, and the castings can be extracted.

The collected drainage (worm tea) is also a powerful liquid fertilizer that can be diluted and sprayed onto plants – this provides them with nutrients, and is known to enhance microbial activity in the topsoil.

And then, there are the worms themselves. After a few months, when the worm populations have skyrocketed, it is wise to begin extracting worms to keep their reproduction rates high (this is called maximum sustainable yield). These can be put into the garden or the compost, where they will continue to do their good.

They can also be used more directly in food production. Feeding them to backyard chickens or fish can offset feed costs, and make egg, chicken, and fish production more self-sufficient and sustainable. This is my ultimate plan for my system.

            Healthy worm bins have tens to hundreds of thousands of worms in them. Each red wiggler has around 2 Calories in it, and a laying chicken (for example) consumes around 400 Calories per day. That means that 50 worms could easily make up 25% of the hen’s diet (in addition to whatever other bugs she found herself) – if that’s not a huge step towards self-sufficiency, I don’t know what is.


My column appears every other Sunday in The Woonsocket Call and The Pawtucket Times. The above article is the property of The Woonsocket Call and The Pawtucket Times, and is reprinted here with permission from these publications. These are excellent newspapers, covering important local news topics with voices out of our own communities, and skillfully addressing statewide and national news. Click these links to subscribe to The Woonsocket Call or to The Pawtucket Times. To subscribe to the online editions, click here for The Call and here for The Times. They can also be found on Twitter, @WoonsocketCall and @Pawtuckettimes.




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