Update: Due to popular demand for information about how to care for worm bins, I'm thinking about writing a small book about the subject. Please let me know if you'd be interested in having a little worm bin manual! (Yes, I know there is another such book. I'd like to do one in a slightly different style.)
Years ago, when I was poor and under-employed, I craved a worm bin (aka vermicomposter, aka worm composter), famous for the fastest compost in the West. I did research on the web, and found that commercial bins were expensive, as much as US$200 for an Australian multi-tray "worm farm", which was way too big for my apartment-dwelling self anyway.
That winter, I visited my sister in Oregon nursery country, and she had the brilliant idea to use nursery flats as trays. Guess what some of the commercial bins are made from? One U.S.-made bin got started that way, and has since done some customizing, using their own molds.
I've seen simpler versions of worm bins, a 5 gallon bucket, or a stack big Rubbermaid tubs with a lid. They probably work as well, at least until you want to harvest your worm castings, which you must sift out of the newer bedding and food scraps; not to mention fill a perfectly good tub with a ragged pattern of holes.
The tray version seen here allows you to segregate old from new, in just a few minutes. It also makes trips between "floors" much shorter for the worms. Less crawling, more eating. And pooping. Worm poop is good.
Mine has a couple of issues I have not gotten around to solving, more on that in the last couple of steps.
Update, Sept. '07: After all these years, I finally realized how easy it would be to separate the liquid from the food and castings. The castings I had been getting were thick mud.
Enter the filter! I lined the next to bottom tray with heavy shade cloth, usually used overhead for shading plants, etc. You'll see it in the shade plant section of the nursery where you go to get your flats. I'll post photos later.
Onward to the building part...
Update, : May 28, 2008 See step 7 for some info on how I harvest the castings.
Update March '09: There seems to be a steady stream of questions about how to maintain worm bins. People seem to want more detail than I have provided here, so I'm thinking about writing a small book.
Update March '12: No book has been written yet, but I'm seriously considering making an ebook/iBook. If you're interested, please let me know, it will help me determine the interest level.
Please let me know, preferably via comment or private message, what delivery method you'd prefer. Paper book?, e-book? I kind of like the image of an intrepid composter outside, muddy hands clutching a Kindle. ;-)
Step 1: Get your stuff together
A gruff old country nursery man sold me the flats for seventy-five cents each.
- 3-5 (or more if you eat a lot of vegetables) nursery flats
- a piece of heavy 3-5 mil plastic sheeting, big enough to line one tray with a couple of inches coming out over the top edge. This will be the bottom tray. Another piece to lay over the top as a lid is optional. Better yet, a piece of screen to keep pesky flies out.
- shredded or torn paper for bedding. I first used newspaper, then got a big bag of "cross-cut" shredded office paper from the Accounting dept. It works great, and I don't have to tear paper or put it through a home shredder any more.
- Alernate bedding material: Coffee Chaff! It's the outer skin on coffee beans that literally flakes off during the bean roasting process. I've been using it exclusively for over a year now, and it works great. No word from the worms as to whether or not they are getting a buzz, or having trouble sleeping.
I like this material better because it's a by-product with few "higher" uses; whereas paper can be made into more paper, rather than getting down-cycled into a soil amendment.
- 1 small stick for spreading bedding and food scraps.
- about a pound (a little less will do fine) of red wriggler worms. Start with less if you like, it will just take a little longer to develop a population large enough to fill your trays. Of course, your needs will vary depending on the volume of scraps you generate.
- optional lid to keep varmints and light out. I used a scrap of wood.
- food scraps, vegetable matter only! No fats, which can clog the breathing pores on worm bodies.
Step 2: The foundation
I folded the corners as if I was wrapping a gift box inside out. Origami folders will know exactly what to do.
The important thing is that the plastic is folded fairly neatly, so it does not bunch up and prevent the tray above from sitting down straight and comfortable.
Add shredded paper, enough to fill it about 1/4 full. If you're ready to add worms, dampen the paper lightly. Worm literature says, "like a wrung out sponge". Not soggy and dripping, yet damp enought that sensitive wormy skin is not instantly dessicated.
I usually don't put any food in the basement layer, as the worms seem to like this as their living room and bedroom. They tend to go up to higher layers to feed, and congregate in the bottom, where most of the castings (aka worm poop; compost) end up.
Step 3: Second verse, same as the first
It usually works best to put one end in first, then lay down the other. Jiggle and fiddle as necessary.
This is important, as you don't want any leaks, or fugitive worms that may meet an untimely end underfoot, in a bird's beak or squashed at the next feeding time.
This image shows the almost finished product. Note the not so carefully trimmed plastic liner obscuring the foundation tray. On the ends, you can see the ribs that hold the trays up, leaving an inch or so of space between the bottom grids. That's where the food, bedding and worms go.
Step 4: Ready for worm move-in
They are available to buy, for an equally costly ~$20 a pound. Given my Scottish ancestry and small bank account at the time, I decided to go foraging on my own. There's a horse racing track nearby, and the manager gave me permission to dig around in their old manure piles. I felt a little, er, sheepish, but swallowed my pride and commenced to digging my own pound or so of worms. That was almost ten years ago, and their descendents are happily munching away on my lettuce scraps, banana peels, and mango seeds. Yep, the seeds, which eventually soften up and become cozy little hideaways inside.
Step 5: Care and feeding
Meanwhile, if you have a good source for trays, worms or other information, please post it here.
Step 6: The Harvest
I confess to not having read this instructable recently, apologies for any redundancies.
The tray full of castings is usually the bottom one, where most of the worms stay. I usually rotate the trays, put that one on top, and move the entire bin outside.
The worms can't take being in the light, so they head downstairs, encouraged by my gentle stirring once or twice an hour, sometimes once or twice a week. Eventually, they all move lower, though it's a good idea to poke through any clumps. I suppose if you are more patient that I am, they'll all go on their own, with less work for you. I'm a little paranoid about ejecting my trusty friends from their comfy abode, so I am pretty thorough about sifting through the muck to get all the worms I can back into safer territory.
The harvest, and being able to keep the newer and older food separated are for me, the two main advantages to using the tray system rather than having one big tub.