Maintaining a Worm Bin

worm bin 1

This image might represent a new low in aesthetics from the Root Simple Photo Department. And that’s saying something.

I freshened up our big worm bin today and I thought I’d report on what I did because I get a lot of questions about worm bin maintenance.

First, I want to say this is just how I go about it. Other people will have different methods and habits. Worms are forgiving and reasonably adaptable, so you have a whole lot of leeway in keeping a bin. As long as you don’t let the worms dehydrate, drown, bake, or utterly starve, you’re going to be okay.

Our worm bin is pretty big (5 feet long), and made of pine boards.  It bears an unfortunate resemblance to a coffin, but it works wonderfully. I used plastic storage totes for my worm bins before we built this, and while those worked fine, I really like my big bin for two main reasons. The first is the size. It can take whatever I throw at it. It takes all my kitchen scraps, except for the really choice stuff that goes to the chickens. The second selling point is that the wood breathes, and that seems to make the worms happy.

Maintaining the Bin

The Conceptual Divide

I divide my bin into two areas, left and right. There’s no physical barrier between the sides, just a conceptual distinction. Usually one side is working and the other side is resting. This division is easy to make in a long, skinny bin like mine, but can be managed in a smaller bin as well.

Basically, once you’ve got a worm bin going, there will come a time when you’ll need to harvest some of the castings. Those castings are valuable in the garden, and the worms don’t want to live in their own waste. You’ll know its getting close to harvest time when you see pockets of scraps here and there, but mostly the texture of the contents looks like soil or coffee grounds. Or maybe fudge, if it’s more wet and compact. Fudge is a less than ideal environment for worms.

In the picture at the top you’ll see my most recent working side. There’s a lot going on in there still, some big food pockets, wood shavings everywhere, but the texture is becoming too black and dense overall. Compost worms like a little air, a little “wiggle room” and a diversity of habitat. It was past time to change this working side to a resting side.

Resting comes before harvest. This is where dividing the bin in two comes into play. Resting means no more feeding, so that the worms will finish up whatever bits of food are left around. But of course you can’t starve out your worms, so you only rest half of the bin at a time.  To do this, you put your food scraps on one side only. The worms on the resting side will finish up whatever food pockets remain and then migrate over to the active side for the fresh grub.

This doesn’t happen quickly. I’ve never made note of how long migration takes–it will vary, depending on many factors. I just poke around in the resting side whenever I happen to think about it. If I don’t see anything recognizable beyond non-digestibles, like avocado pits, fruit stones and egg shell shards, and I know it’s ready for harvest.

There will also be a few worms left, no matter how long you wait. More on them later. If your bin is outdoors, other insects like sow bugs might be in there too, but are harmless.

This is the process in a nutshell:

When your bin is looking mostly done, ie full of castings, rest one side of it. This means you feed only on the opposite side. When all the recognizable scraps are gone from the resting side, you harvest the castings. Then you can put fresh bedding in the empty space, and start encouraging the worms to move to that side.  Soon, you will be able to rest the opposite side of the bin, and eventually harvest it. And so it goes, back and forth.

Below is the resting side of the bin. I put a layer straw on top for a little insulation.

Again, nothing goes into the resting side while it’s resting, unless it needs water to keep it from drying out.

worm bin2

Below is how it looks with the hay scraped off. See? Nice and dark

worm bin 3

And here it is close up.

worm castings

The pale things are mostly eggshells, along with a few wood shavings that drifted over from the working side. There’s a soldier fly carapace on the far left, dead center. I ignore those.

Eggshells never really break down in a worm bin, but I don’t mind them ending up in the garden along with the castings. If I wanted pretty worm castings–say if I were selling them–I wouldn’t put eggshells or fruit pits or pumpkin seeds into my bin at all. These things just linger and are hard to sift out.

Harvesting the Castings

Harvesting castings is the only hard part about keeping a bin–and it’s not even hard, it’s just somewhat less than convenient. No matter how long you rest one side of the bin, there will always be a few confused worms living in the finished castings. If you bag them up with the castings, they’ll die.

So you have to sort out your feelings and responsibilities vis-a-vis the worms. I won’t blame anyone for letting the strays perish (they had warning, after all) but I have guilt, so I do my best to sort them out.

However, hypocrite that I am, as I do so, I entertain myself by trying to envision some system where I could enlist the chickens to do the job for me. They’d be great at it, of course, and the worms would give them a good protein hit, but they’d toss the castings everywhere in the process, and add their own fertilizer to the mix. Yet, some sort of containment system might work…

Daydreaming aside, until I invent that Chicken Powered Terror Dome for Worms, I have to sort the worms myself. There are various tricks for this. None are foolproof. I believe I’ve blogged about them before.

After trial and error I’ve come to the conclusion that it’s just as easy to pick them out by hand as to do anything else. The pyramid system and the like work, but are not any faster. Worm sorting would be most fun with someone else–sort of like shelling peas–but today I listened to an audiobook while I worked, and that was good. too.

Harvest is simply reaching into the finished side, gathering up a handful of castings, and dropping them into a five gallon bucket. At every handful I pull out any worms I see and toss them into the working side of the bin. Sometimes I find a bit of paper, like a coffee filter that is not quite finished. That also goes back into the working side. (Note: If I were to start to find food scraps, though, I’d stop and let the bin rest some more.)

Any fruit stones or avocado pits or sticks, things that will never break down go into a smaller bucket for later disposal in some remote corner of the yard. The process actually goes pretty fast. I harvested 5 gallons of castings in less than an hour. You could go through a plastic tote-type bin much faster.

Making a New Working Side

After harvest you’ll have empty space–and that space will become the new working side, which means you need fresh bedding for the worms. I usually start by robbing some of that from the other side of the bin. Anything that’s big enough to notice, like a corn husk or a coffee filter or a handful of straw, I’ll grab. Today, I scraped the top layer of my working side into the empty part of the bin.

Worms like materials that provide some fluff or air to the texture of the bin. I like to use a combination of materials, whatever I have on hand. Shredded newspaper is a standard bedding material, but we don’t take a paper. Today I used rotted straw, wet pieces of cardboard, lots of dead leaves, a few wood shavings and a little bit of garden dirt for grit.

Note regarding paper: I wouldn’t use anything bleached or anything printed with shiny inks. Plain corrugated cardboard is great, as is brown paper.

I also mixed in some well composted cat litter into the mix, but that’s eccentric, and possibly dangerous, and another story for another day.

As you collect your materials, wet them down. They should be moist, not soggy. I dip everything I use in a bucket of water before introducing it to a bin. Worms don’t want to wiggle through dry, scratchy stuff, but they’ll also drown in puddles.

worm bin 4

Above you can see the left side of the bin, the new working side, full of fluffy, moist, leafy material. On the right is the new resting side.

The worms are going to be much happier with all the breathing room in the new space. I’ll start adding food on left side–a bit more conservatively than usual, since there isn’t a big worm population over there yet. The worms living on the right side will start moving over pretty soon, leaving the pure castings for the next harvest.

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    • I just keep them in a bucket until I need them. A lid is handy. If you leave the bucket out in sunlight, seeds which never decomposed may sprout–usually tomatoes and squashes in our case. We’ve replanted the tomato seedlings!

  1. Where did you get your initial worms? Did you buy them? Or did they come from your yard?

    Also, how do your worms cope with heat? I tried keeping a wormbin outside in the shade, and they still died even though they weren’t dried out. Possibly it was because I bought the worms from a bait store and they weren’t right for this climate? I’m not sure.

    • I bought my first batch of worms at a farmers market long, long ago–and ended up putting them in the compost pile when I gave up on the project the first time. My second batch came from another worm bin. They actually come from the bins that were (still are?) at an art space here called Farm Lab/The Metabolic Studio. Fancy art worms! (I knew someone who was working on the bins, and she gave me a scoopful.) It’s funny where you can get worms.

      It doesn’t take many to get a bin going, so you certainly could collect them from your yard. And you don’t need to collect a pound, or whatever the books suggest you need. A handful will do. If they’re happy, they’ll breed and fill up the bin eventually.

      Re: the heat. Yeah, an outdoor bin can be tricky. I believe the size of my bin is mostly what saves the worms from the extreme heat. They can migrate to the center where it’s coolest–that way they have a several inches of insulation on all sides. If they were in a smaller bin, they might not be able to escape the heat. I think I may have had some losses in our recent heat wave, actually, now that I think about it. It’s just not as busy in there as usual. But there are plenty of survivors, so it will be fine.

      I also hose down the exterior of the bin on hot days. I figure there will be some cooling as the water evaporates off the wood. I also like to put a layer of straw on the top surface to provide even more insulation. And finally, where it’s positioned, the bin only gets the last sun of the day.

  2. You put diapers on the chickens and put a window screen box over the worm bin to catch what they kick about. That would be easy pickings for chickens.

    Or, you could get the worms out by worm grunting aka worm charming aka worm calling like these guys.

    If you know the eggs shells won’t compost, why don’t you give them to your hens?

    • Feeding egg shells to hens is something Erik and I bicker about. He’s afraid of turning the hens into eggs eaters. The safest way to give shells to hens is to dry them and crush them beyond recognition. I’ve tried that, and it’s a pain. Its so easy to end up with stinky shells, and where do you keep them? etc. So they go into the worm bin. They could go in the compost pile, but the bin is closer. Really, it’s all about my own laziness.

  3. Thank you so much for this post. I just got my bin started[3 months old] and had all theses questions and you just answered all of them, so again thank you.

  4. Very interesting and informative post – and ‘Chicken Powered Terror Dome for Worms’ was the cherry on top.

  5. Funny. I was just beginning to re-build my worm bin and took a break. I was also thinking about how to compost dog manure earlier… tinker on, I will. 🙂

    • Try black soldier flies for animal and human waste – they apparently power through poo and the like very quickly and the resulting larvae are great for chickens! I haven’t been able to keep them alive up here in Seattle, but I will continue to tinker on, as well…! 🙂

    • We’ve long been intrigued with soldier flies, but haven’t yet got up the energy to build some sort of …system? Hatchery? They do find their way into the worm bin, though.

    • I remember reading about this cat in Texas that hangs rotting meat above his fish tanks in his outdoor aquaponics system. The BSFs just devour the meat and then quite a few maggots and some overfed flies drop right into the tank. Just add duckweed.

      @ Lindsey -I’m across the state in Spokane and was wondering myself if they’d be able to over-winter somehow. I guess if I ever hunker down and build that bio-shelter I’ll have it made. Until that day when I find extra time and materials…

      @ Mrs. Homegrown -I’m sure we’d all be interested in your cat poo composting system. My cat poo composts itself in the potato patch, the irises, etc. 😉 My dog poo however is always found on the patio and I feel irresponsible trashing it.

      @Sara -Thanks for the link!

  6. This is very interesting – I have read many times about people having worm bins but this is the first time I have ever read about how to harvest the castings. I figured you just keep dumping scraps on and then dump the whole thing – worms and all – on the garden. That being said, it still seems like too much trouble for me. I throw scraps directly onto an unused portion of my garden – so I could say that I have a rather giant worm bin.

  7. How do you use the worm castings? I’ve got a tiered worm bin that produces, but I’m never sure on how to effectivley use the castings?

    • You should use your castings! They’re not called “black gold” for nothing. Castings are an excellent plant tonic. Unlike fertilizers, you can’t “burn” the plants by applying castings around the base of plants. So that’s what I do– I sprinkle it around. A handful can give a boost to potted plants and house plants. It can be “side dressed” in the veg. garden (basically sprinkled or lightly raked in around the plants), or it can be spread along with other soil amendments when you’re prepping a new bed. A bit can be added to potting soil to give it a boost. People make tea of it too, but I never do that, because I’m too lazy.

  8. You will not create chickens who eat eggs. When I was little, Mama always put the eggs into the oven after cooking something there. The idea is to just brown the eggs. The eggs are then indistinguishable as eggs to chickens or dogs. We fed some of the eggshells to the dogs.

    Eggshells contain calcium. The slime left in the eggs is protein. Most people wash the shells before baking. Why? it’s a waste of protein. You could even use a solar oven or your oven outdoors, the one Eric built.

    You do not have to crush them beyond recognition. You can put them in a coffee can or something to store in the refrigerator. However, there should not be many to store if you use them for part of the hens’ calcium intake every week, at least.

    Hens need protein to make eggs. The calcium in the shells makes their next shells hard. I never have used any chicken feed for my hens, but they do get plenty of food with nutrients they need.

    When I drop and egg, the hens are on it like white on rice. I tried to stop them so they would not eat their own eggs. It was hard to stop four determined hens. After eating their own eggs I broke, they did not turn to eating their own eggs.

    Egg shells are good for tomatoes, preventing blossom end rot. Of course, watering the tomatoes so they can access the calcium is the key.

    By the way, last week I found under the sink a coffee container of eggshells from two years ago that had been browned and crushed. They had a smell that was not at all foul or fowl. I did not toss them, just determined to use the lost eggshells.

  9. I’ve got a big old coffin-like bin, too, and I LOVE it. I also have the tower and smaller plastic bins, but the coffin is absolute tops for making vast quantities of castings. You guys are lucky it doesn’t get so chilly down there in the winter – every Halloween I’m outside shoring up the coffin with straw bales and this and that. It’s hilarious.

    I love your system – so simple and elegant, just like the worms themselves. My downfall is not segregating the sides well enough (working vs resting) and becoming engrossed in other activities and forgetting about the bin for a while. Which I guess is a positive, huh? Worms wait very patiently.

    Also, I bake my egg shells at 250 for a while until they are brown and then just crush them up with a gloved hand. I keep all the shards in a giant Tupperware and periodically just throw a giant handful to my hens or throw some in the garden or whatever. Works great! No smell!

    • Yes, there’s really something to be said for a big worm bin–and for wood. I don’t think I’d trade what I have now for anything, not even the fancy stacking kind.

      Good tip about baking the egg shells–that bypasses the stink problem nicely.

  10. Love the simplicity of the worm bin.

    With regards to egg shells, I dry them (along with banana peels) and then use my coffee grinder to reduce shells/peels to a powder. I add the mixture to my tomato plants–good source of calcium/potassium that is more readily available to the plants in powder form.

    Diane L./Bloomington,IN.

    • What a great idea! How do you dry out your banana peels so thoroughly? You have a dehydrator?

  11. I have a very old pilot-lit gas oven that is perpetually warm. I use it to dry out egg shells, the banana peels, make yogurt, and make raisins from some over-ripe/too sweet/squishy grapes. The idea for using egg shells & dried banana peels (ground up in my coffee grinder) came from a YOUTUBE video of a man who gardens.

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    • It depends. It’s important to keep the entire contents of the bin moist, but not soggy, like a wrung out sponge. If it seems to be drying out, yes, add a little water (maybe with a spray bottle or a hose set on sprinkle, so you can control the wetness, or better, add bedding material which you’ve soaked and wrung out.

      Likewise, if it seems to be soggy, add dry bedding material to sop it up.

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