Ook’s Worm Bin: Final Report on the Vermicomposting Project

In the beginning:

The worm bin was started in the library in April 2017 with a handful of worms. Over the course of a year the worms increased and we harvested the compost several times. They were given mostly banana peels, apple cores, teabags, and old peppers and tomatoes. We used damp, shredded newspaper for bedding. The fruit and vegetable matter was always frozen for a few days first to make sure we didn’t get fruit flies in the bin. They were also given eggshells. Compost was harvested every couple of months, but the bin was never entirely cleared out; we just did partial harvests.

Worms were taken out to start four other bins for the 4-H group.

Problems we had:

We had a lot of mites in the worm bin, especially when it was wetter. Once the worms all tried to flee the bin, because we gave them crumbled-up old cake and it grew a lot of blue mould. Worms are supposed not to mind some mould, but obviously they do!

Another time the worms were given too many leftover green peas from the restaurant. A week later, the bin smelt like a pig-sty! (Have you ever smelt a pig-sty? Pig manure is very high in ammonia. It stinks!)

Solutions we tried:

In the fall of 2017 we put some dry leaves on top of the compost in the bin. We noticed that the population of mites seemed to drop. The leaves stayed dry on top while the compost underneath was moist. In the winter we started using newspaper again, and the mites reappeared.

When the worms all tried to crawl out, we picked out the mouldy cake and gave them a lot of new damp-newspaper bedding.

When we ended up with a stinky bin because of too many cooked green peas, we had to take out the peas and a lot of the newspaper, prepare new bedding and food, and air out the worm bin and the library.

The worms go home:

In April of 2018 the worm bin was taken to the library manager’s house, because the library gets very hot on sunny days in the summer. In her cellar the temperature is about 12 to 15 degrees Celsius all year round. The worms seemed happy in the cellar and didn’t try to crawl out. They were fed only about once a week, with fruit waste (frozen), eggshells, and vegetable peelings. There were still mites in the bin.

In May, after harvesting some compost, the library manager put a lot of dead leaves (mostly maple) in as bedding.

In June, the library manager noticed that there seem to be no mites in the worm bin, although underneath the surface leaves the compost is quite moist. Since last time that happened was when she put leaves in when the bin was at the library, where it is warmer, it seems likely that using dry leaves as bedding is what reduces the mite population, not the temperature or the moisture content.

There was also a small spider living in the bin, and a few sowbugs. (It’s likely that the sowbug came in with the leaves, since the cellar is fairly dry. The spider could not have eaten all the mites.)

Observations and Conclusions:

Dry leaves may be better worm bin bedding than shredded newspaper. However, if someone was going to start a worm bin from scratch, they would probably want to put a layer of damp, shredded newspaper in to get started, with some dead leaves on top. We know that good compost needs to contain a mixture of ‘brown’ and ‘green’ things — sources of carbon and sources of nitrogen. It’s possible that the newspaper doesn’t work as well for the ‘brown’, carbon-containing material as autumn leaves. Kitchen waste is mostly ‘green’ — high in nitrogen. That is why it smells bad when you get too much of it.

It does seem like the way to control mites is to use dry leaves in the bin. This would be easy to do year round if you are able to keep some bagged leaves in your garage or woodshed. If you lived in an apartment, this would be trickier. We don’t know why the leaves help with mites. The bin is quite moist underneath, so it doesn’t seem to be dampness. Perhaps the leaves change the pH and make it an environment that mites don’t do well in.

Harvesting the compost takes a long time and is very labour-intensive. The worms don’t like light but they don’t burrow far into the compost, so even when you just scrape a handful off the surface you have to pick worms and cocoons out of it.

The worm bin doesn’t produce a lot of compost; however, it is very rich. We used some as a top-dressing on the library plants and the geraniums all bloomed very well. The hibiscus began to bloom as well. We also got apple trees and tomato plants germinating in some of the library flower pots!


Harvesting Compost

Today we harvested the compost from the worm bin. We did a partial harvesting of the compost some weeks ago, but it seemed time to clean it out more thoroughly. The bin was getting too damp and there wasn’t a lot of uneaten bedding left. We scooped the compost out into a mound on a drop sheet and let it sit to give the worms time to burrow down out of the light. While we were doing this we picked out some of the old wet newspaper to go into an outdoor compost.

How we harvest our compost: a drop sheet, spoons (and hands). Worms and some of the old bedding go back into the bin with new shredded damp newspapers; compost goes onto the plants or into an outdoor compost bin to finish breaking down.

We began using our hands to carefully lift away the top layers of the compost one handful at a time. The worms only go down an inch or so to get away from the light, so there were usually several worms caught up in each handful, which had to be picked out and put back in the bin. The compost went into a pail. Slowly, slowly, we worked our way down, until at the bottom we were left with a big double-handful of wriggling Red Wigglers.

A mass of Red Wiggler worms.
The mass of worms left once most of the compost has slowly been removed. I picked a lot of worms out of the handfuls of compost I was taking off, too!

They weren’t very happy, having nothing left to hide under! We put them back in the bin with some food and some new damp newspaper. We tried to have it drier this time, because the moisture from the food will add to the dampness. We were getting a lot of compost mites and keeping it a little drier should cut down on those (we hope).

A pail half-full of worm-casting compost.
The harvested worm castings in late August 2017. There’s some bedding (shredded newspaper) that hadn’t broken down yet in there too.

August Worm Update

Our worms have multiplied! Our bin is quite well-stocked now. This has led to changes. We began to get worms crawling up the sides and around the lid, looking for greener pastures — or some place with more than a few apple-cores to go around. We solved this problem thanks to Mrs. B. of Mrs. B’s Meals to Go (across the road from us in the old Bell Inn. She finds us some leftover produce and scraps every week and keeps the worms happy.

The old Bell Inn, location of Mrs B's Meals to Go in Dorchester, NB.
The Bell Inn, home of Mrs. B's Meals to Go, across from the library. Mrs. B very kindly provides us with some produce scraps every week for our worm bin.

We’ve also been finding that the bin gets too damp during the four days the library is closed. This is probably both because it’s warmer and because there are a lot more worms and a lot more damp food in there. We’ve tried to mitigate this by cutting some square ventilation holes in the lid and taping screen over them. That helped a little. Leaving the lid off for part of the day while the worms are out in the library also helps. So does putting a sheet of dry newspaper tented over the top at night. It absorbs some of the moisture and can be thrown out in the green (compostable) garbage the next morning.

It’s getting time to change the bedding and clean out the compost again, though!

Ook’s Guide to Vermicomposting

Ook the Library Gorilla and friends did a lot of reading before setting up a worm bin. One thing we learnt is that vermicomposting can be a simple hobby, or a life’s mission. Here at the Dorchester Memorial Public Library, we look on it as a scientific exploration, a work in progress that we are always refining and tinkering with. Here’s what we started with in April 2017, though.

The Worms:
Eisenia fetida / E. foetida is the best species – one common name for them is Red Wigglers. It’s easy to give them the environment they like in a bin. (However, the earthworms you dig up in your garden or find on the road after a rain here in Atlantic Canada prefer to live deep in solitary burrows. They won’t survive in a worm bin, so leave them in the backyard!)

magnified worm
Red Wiggler worm viewed with our Merlin magnifier.

Our Bin

We used a plastic storage tub, 60x40x38 cm – ours was a cheap one, so it won’t be as durable as more expensive one might be. It needs a lid – the worms do not like light (and by ‘do not like’ we mean, it causes them stress and they’ll flee it). You’ll also want a tray under it. The tub should sit up on something as feet to keep it out of the liquid that may drain out of the compost. We just used plastic instant-coffee jar lids to set it on. We ended up buying two tubs and using the second lid as the tray (because that was much cheaper than buying a plastic boot tray), but some people use a second tub as a tray – an inner and an outer bin. If you do that, you still want coffee jar lids or something similar for feet, because you’ll need your ventilation holes in the inner bin to be up above the edge of the outer bin, and you’ll want a gap between your outer and your inner bin, of course.

Toy Gorilla (library mascot) and worm bin.
Ook the Library Gorilla, his puppy puppet, and our worm bin.

The lid and sides need ventilation holes both for oxygen and for humidity-regulation. Worms need air! We drilled small holes (about 2 mm or 1/8”) in the lid and around the sides close to the to the top. Some people make much larger holes for ventilation and tape screen over (on the outside) to keep the worms in. Since the worms don’t like light, small holes should be better if the bin is going to be sitting in a library where there are lights on all day. We didn’t screen the small holes in the side and lid. If the bedding gets too damp or they’re unhappy for some other cause (see below), the worms will scale the sides and find a way out, but we haven’t had a problem with that so far. There are larger holes in the ‘handle’ part of our box as part of its manufacture, which we covered with screen, but we taped it inside and that isn’t working – inside the box it’s too humid for duct tape to stick. However, no worms have escaped so far. We could move the screen over those holes to the outside if need be there but for now we’re not worrying about it.

Some people go without drainage, but you can get condensation building up, or get your bedding too wet, or put too much soggy food in, and that’s bad, so drainage is a good idea. We used the same small drill-bit to make clusters of holes at both ends of the tub. On the outside, we duct-taped sections of fibreglass window screen over areas where we’d drilled holes in the bottom. So far, this has kept the worms in! Any liquid that does drain can be diluted and used on plants – it’s too concentrated (too high in nitrogen, maybe?) to be poured straight onto potted plants, according to some sources. You may not have any liquid drain out. We haven’t so far.

Patches of screen covering small drainage holes.

The basic bedding is shredded newspaper, wetted to be about “as damp as a wrung-out sponge” the sources all say. What we did was cut newspaper into coarse strips with a paper-cutter and then dunk it by handfuls in a pail of water, not leaving it to soak — just in, swish, and out. If you get it too wet, add some dry stuff. You don’t fill the bin – you only want a depth of about 10 cm or so to start with. The bedding should be loose, not packed down. Torn up egg carton is good and quite small children enjoy tearing up and dipping egg carton in water. Yay! A chance to be allowed to destroy things! Apparently printer paper is bad – though nobody seems certain why. Definitely do not use receipt paper since that stuff’s coated with something unpleasant.

It’s best to introduce the worms along with some of the compost they had been living in previously. Some suppliers, such as Worm Composting Canada, ship their worms in a mix that contains compost already, but some come as worms alone, in which case, you might want to put in some compost from your home compost, but you may be getting sowbugs, (harmless) mites, springtails and other invertebrates. This isn’t necessarily bad, but you could end up with fruitflies and things too, which would be a problem in the library, or at least annoying. (More on fruitflies below.) Some sources recommend adding a handful or two of outside earth, for grit and useful microbes. Worms have a gizzard (a bit like birds) and like birds, they need to ingest some grit in order to grind what they eat.

What to feed the worms:
Kitchen waste, such as what you’d put in your outdoor compost, is what you want to feed the worms. Don’t put in anything high in protein – no dairy products, no meat or bones, of course – that sort of material will become very stinky! They also dislike citrus peel and onions, though papery onion skins are fine. Crushed egg shell is recommended in Kalman & Schaub as containing nutrients that worms need. In our library they are mostly living on apple cores and banana peels. Wilted salad, mango skins, fruit that you forgot until far too late, cooked vegetable leftovers – those are all great for your worms. Bread is good, but we’ve found you have to crumble it up fairly finely or you get a big piece of blue mould, which doesn’t seem harmful but you don’t need clouds of blue mould spores in your face when you open the bin. Eventually, the worms will eat the bedding, too, but you don’t want them to have to live entirely on damp newspaper. The popular press is probably not a healthy diet.

How to feed the worms:
Bury the food under the bedding. The worms in your bin won’t be sitting on the surface. It’s recommended that you keep track of where you’ve put the food, to keep the worms moving through the bin as well as to keep track of how much they’re eating, so that you can judge if you need to feed them more or less. If you overfeed, you’ll end up with a tub of rotting food. If that happens, take out some of the stuff that isn’t being eaten. We feed ours once a week, but we don’t have very many. (We started off with just a few dozen worms from a friend.) Some of the resources recommend chopping up the worm-food – this isn’t necessary, but it makes it break down into the rotting soft stuff that the worms can eat much faster. It’s probably a bit slower if they have whole apple cores, etc.

Eventually the bedding will all be black earthy stuff, more or less, and then you need to harvest the worm castings – your compost! We haven’t done this yet at time of writing, but you can find directions on line – you just make cone-shaped heaps on a big plastic sheet, let the worms hide from the light, and keep taking compost off the outside, picking out the worms and their egg-cocoons to go back into the freshly washed bin and the new bedding.

Potential problems:
Overfeeding! Too much food will just rot and get smelly. Also, you don’t want anaerobic composting to happen. (Bacteria of the sort that live in oxygen-starved environments are stinky! Also, they’re bad for the worms.) The bin should be damp, not soggy. It should smell kind of earthy, or like whatever you’ve just put in, apple cores or mushy overripe mango, etc. If it is stinky and unpleasant, there’s a problem that needs dealt with. If you think it’s too wet, add more dry bedding and fluff it all up. You can fluff it up if it’s getting too compacted – newspapers fusing into a lump. (Ours does this because there aren’t enough worms yet.) If it’s too dry, sprinkle it with water, or add some soaked bits of egg carton. If it’s always too wet, consider whether you’re adding too much food, too much really wet food, or whether you should add more ventilation holes.

Fruit flies and fungus gnats. These can live and thrive in worm bins. Fruit fly eggs are on much fruit, but people seem to find that freezing kills the eggs/larvae on your apples, tomatoes, bananas etc, so before you put stuff in the worm bin, freeze it. We have a plastic dish in the little library freezer compartment and put the apple cores in that and feed them (thawed) the next week. A ziplock bag would work too. No problems so far! Another thing people recommend to keep fruit flies in check is a sheet of whole newspaper laid over the bedding. Other things can also live in worm bins, but mostly the things that do are also composters and don’t do any harm.

Worms running away from home. Worms will try to escape if their environment goes bad – too wet, too little food. They will then perish horribly on the desert of the floor. They also don’t always settle in well, apparently, but some of their previous compost helps. We haven’t had any problems this way so far.

Too hot or too cold. Room temperature is a good temperature for Red Wiggler worms. Temperatures too high or too low will kill them. They’re not winter-hardy around here.

A worm cocoon. Several baby worms can hatch from each cocoon.
A worm cocoon. Several baby worms can hatch from each cocoon.

Basic Worm-Care Facts

Bedding: damp shredded paper and a bit of earth
Temperature: 13 to 25 C.
Amount to feed: According to Kalman & Schaub, each worm eats about half its body weight a day. It isn’t necessary to feed them every day – a couple of times a week will do. It’s good to know how many grams of worms you started with, so as to estimate how much kitchen waste you should be feeding them.
What to feed: Fruit leftovers, peels, cores, etc. (frozen for a day or two to reduce the chance of introducing fruit-flies to the compost bin), crushed eggshells, vegetable peelings, cooked vegetable leftovers, leaves, grass, plant trimmings, bread, coffee grounds, teabags, coffee filters, pizza crust, cake, cookies, cereals. More finely chopped up material will break down and be consumed much more quickly.
When to harvest the compost and renew the bedding: Every two to three months (Kalman & Schaub).

A worm in the compost.

Recommended Reading and links to some useful vermicomposting resources

Kalman, Bobbie & Janine Schaub. Squirmy Wormy Composters. New York: Crabtree, 1992. (Unfortunately, this excellent resource for classroom/library vermicomposting is o.p.)

Lewis, Suzanne. Composting for Canada. Edmonton: Lone Pine, 2010. (This is mostly on outdoor composting but has one chapter on vermicomposting.)

Woolnough, Mike. Worms and Wormeries: Composting Your Kitchen Waste … and More. Preston: Good Life Press, 2010.

Worm Composting Canada
One of the best resources we found – they are also a supplier of composting worms and are recommended by the Royal Botanical Gardens in Hamilton as a source of worms for classroom compost projects. Take some time to explore their website.

A Vermicomposting fact sheet from the Oklahoma Agricultural Extension Office:

A guide intended for classroom worm composting:

From the Worm Composting Canada site, a video on other creatures you might find living in your compost. (You’ll want to watch it full-screen in order to be able to read the captions.)

Worm Art, grade 3/4

Today our worms had a visit from Ms. Tingley’s grade 3/4 class to learn about composting. Here’s a gallery of some of the art they produced, including a book by Ricky!