My Foray Into Vermi-Composting

January 19, 2012 at 6:59 pm (DIY, food, Gardening, permaculture, Vancouver) (, , , , , , , )

If you read my previous post about the City of Vancouver’s various programs for handling organic waste, you’ll know that composting with worms is a great option for residents of apartments and condos because worm bins are compact and odor-free.  My family is fortunate to have found an affordable house to rent in Vancouver (what’s really rare is that we have a basement; there’s no “mortgage-helper” suite below) and we have a yard that is all ours to garden as we please.  So, I do have one of the city-subsidized black plastic compost bins in my garden, but I wanted to try out vermi-composting for myself.

A tangle of worms--are they having a party?

There are several reasons I wanted to start a worm bin; they boil down to convenience, speed, and frequency of harvest.  When it’s cold and rainy outside, it’s a pain in the neck running out behind the garden to the big black bin, so my indoor compost collection bucket started to overflow and stink; I tried keeping a larger bucket just outside the backdoor to reduce the number of trips out back, but it just served to attract raccoons and those little buggers soon found that all they had to do was roll the bucket down the stairs and it would crash open, spilling its delicious contents.  Having a worm bin in the basement is way more convenient, although I’d have to expand my vermi-composting operation by three or four times my current capacity to be able to handle all my kitchen scraps this way; for now, we still have to make trips to the backyard bin, just not as frequently.  In my experience so far, food scraps are digested much quicker in the worm bin than in the backyard composter, probably due, in part, to the steady temperature and humidity levels of the indoors compared to the wild swings in outdoor conditions.  Keeping the worm bin indoors means I can have compost year-round, unlike with the backyard bin, which all but ceases activity in the cold of winter.  Whereas the outdoor bin produces a harvest of compost once, maybe twice, a year, the worm bin yields smaller but more frequent harvests of a high-quality soil additive fine enough for seed-starting.  Aside from the foregoing reasons, I find the ecosystem of the worm bin fascinating to watch.  Give me a few more months with my worms and I might be calling them pets.

I’ve mentioned Frank before: he was the original owner of this house and lived here for over sixty years.  Well, his family didn’t do such a great job clearing out his things when they moved the old man to a seniors’ home.  Going through a garden storage space under the house, I found a large (I’d guess 15″ x 24″ x 8″) Rubbermaid storage container with a tight-fitting lid and I immediately thought of making a worm bin out of it.  I knew enough from reading up on it and I already had a source for worms, so I didn’t feel the need to spend $25 getting the bin and tutorial at the Compost Demonstration Garden.  Worms and bacteria breathe oxygen, so to ventilate the plastic bin, I drilled holes all the way around it and about two inches below the top edge.  For fear that the worms might try to escape, I used the smallest bit in my toolbox, although now I realize this was an unfounded fear: given enough oxygen and moisture inside, the worms won’t brave the dry air outside.  They also prefer the dark, and since my bin is clear plastic, I keep it covered with a towel.  Still, they congregate in the center where they’re covered with bedding and have plenty to eat.  When I first introduced the worms to their new home, I made bedding for them by shredding newspaper–and lots of it because it compacts when wet.  I got my worms from a friend (thanks Sarah!) who has the official city-subsidized worm bin that comes with Red Wigglers.  She gave them to me in a bucket of unfinished compost so I’d have plenty of bacteria and whatever other microbes are essential to the process (and because it’s impossible to really separate them).  The worms settled in nicely and within a few weeks, I could tell their numbers were increasing and they could start to handle small amounts of kitchen scraps.

When the old bedding got really mushy, I added more shredded newspaper.

It’s been three or four months since I started the worm bin and I’ve just last week applied my first harvest of vermi-compost to a soil/vermiculite mixture for starting seeds indoors (the two 2 x 4′ fluorescent tube fixtures that I use also once belonged to Frank).  I am able to feed the worms about once a week without overdoing it.  Some people say they have preferences for certain types of foods, but I haven’t really noticed.  They seem to gobble up anything remotely palatable to you or I; the one addition I’ve made to the bin that they really didn’t seem to like and took forever to digest was plant trimmings from an aquarium.  Perhaps the leaves of aquatic plants are too fibrous… Perhaps the pieces were too large… They completely devoured an addition of leftover couscous in record time (I’m talking mere days), leading me to believe that the rate at which they can break down an addition of food scraps has everything to do with particle size.  It makes sense: the smaller the pieces, the greater the total surface area exposed to air, moisture, and bacteria, which, as I understand it, have to kind of pre-digest the food before worms can handle it.  Now, before adding anything to the bin, I use my big kitchen knife and practically mince it.  I’ve even read that some people use a food processor or blender to puree food scraps before giving them to their worms, thus maximizing surface area and minimizing the time it takes for worms to break it down.  I’ll try this if the food processor is already dirty the next time I intend to make an addition to the bin; otherwise, I don’t care to wash it.

If you look closely, you may be able to see the small white ones.

In my worm bin, I actually have two different types of worms.  There are Red Wigglers, which are kind of fat, pinkish-brown in color, and about two inches long at maturity; and, there are lots of skinny white worms no more than half an inch long.  At first, I thought the white ones were just baby Red Wigglers, but I did some research and found that this is a common misconception, that they are, in fact, two distinct types of worms.  One clue: I’ve never observed an intermediary whitish-pinkish teenage worm.  What I have observed is far more interesting and offers a clue to how the worm bin ecosystem works.  The large red worms do not flock to new additions of food; they seem concentrated in older, nearly-finished material.  Presumably, bacteria and whatever other unseen microbes are in there are the first to attack new additions, priming the pump, so to speak, for the larger decomposers to do their jobs.  Then, I observe large numbers of the small white worms starting to break down scraps that are still identifiable as human food.  For sure there is some overlap in their roles, but the large red worms don’t usually seem interested until the food is partially broken down.  So, their different dietary habits are another clue that they’re not the same species of worm.

The worms loved the couscous. I separate the nearly-finished compost towards the front of the bin.

To harvest the vermi-compost, it isn’t entirely necessary to separate the worms, but if you intend to use the finished compost in your garden outdoors, any worms that go out with it may not survive depending on the climate where you live.  It is my understanding that Red Wigglers are not native to the Vancouver area and cannot survive the coldish winters here.  Besides, it is desirable to keep as many worms in the worm bin so they can continue doing the work you’re paying them for.  Separating them is fairly simple.  When I start to see a lot of finished-looking compost around the bin, I just use my trowel to push it close to the front of the bin; any scraps that are still whole and need more time in the bin, I push towards the back, piling them up with the bedding and any new food I’m adding.  I drape the towel over the back of the bin only, leaving the front exposed to the light.  The next time I check on the worms, the nearly-completed compost at the front will be almost completely devoid worms, as most of them will have moved away from the light and towards the new food in the back.  There may still be a few of the larger, red worms still working on whatever remains to be eaten in the front, but for the most part, the worms will have separated themselves from the finished product.  I imagine, they’d move out completely given enough time, but having to pick a few out and toss them back when you go to harvest the finished compost is no big deal.  A another tell-tale observation that lets me know my bin is working as it should: there is absolutely no odor emanating from the bin.  By this I am truly shocked, because you’d expect a box of decomposing food waste to have a major stink about it, but it doesn’t (a stinky worm bin, like a stinky compost heap, would be an indication of anaerobic decomposition and should be remedied with adequate ventilation).  In fact, it has the pleasant, earthy aroma of a healthy ecosystem.

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