How to do worm composting (or vermicomposting)


In the late 90’s I lived in a house with a bunch of people of different talents, skills and interests.  It was in Portland Oregon, and I learned a lot of things there, like about making a pond with a waterfall, and not to hang hammocks on branches that are grafted on, and that sand blasting a house to get 100 years worth of paint off is a huge mess.  And I learned to love Ethiopian food, and that I could make a meal out of anything in the veggie bin that other people weren’t going to eat, and they would want me to share.

I also learned a little about vermicomposting.  I mostly just call it feeding my kitchen scraps to the worms that live in a cedar box outside, but there are some rules.  I learned pretty much everything I needed to know to start out on the internets about this whole process, but I learned alot when I did it for myself so I am going to document my process.

So, it is actually really cool, I think, this idea that you don’t have to throw all this stuff away and that you can turn it into compost for the garden.

This is how we did our vermicomposting thing.  We made a box that stands about 3 feet off the ground and is about a foot and a half deep and is three feet or so long.  My husband actually made it, and he made it out of cedar, which will not rot but has a more desirable quality than plastic, which will not vent and can heat up.  We have vents at the bottom of the bin in the form of very narrow, gaps between the boards that cover the bottom of the bin that allows drippings to come out, but in our current iteration we have no way to collect the drippings. If I made another one, I would make it much larger, because in order to harvest, we have to separate the box into two parts.  Right now, my 2 adults 2 kids family is overwhelming my box.  It isn’t large enough.

I have heard that you can do the whole thing with a rubbermaid bin, but the idea of bending over a plastic tub of worms and food scraps sounds unpleasant.  The bin will be ideal if it isn’t too deep.  Large and shallow would be ideal.  Plastic can work, but it should be opaque and should not sit in direct sunlight.  It also should be vented.

We keep our box in the corner of the yard under a tree, against a fence.  Once a week or so we empty a plastic container that has a tight sealing lid (it is something they sell to keep dog food fresh) that has collected kitchen scraps.  In very wet months I put a tarp over it to keep it from getting too wet, and also because I am not sure if frosty/snowy weather would kill the worms.  They have so far survived 2 winters, one with temps down to below freezing for weeks.  Not sure how much the tarp helped.

When I say kitchen scraps, I don’t mean the stuff off your plate after dinner because there are some rules about what the worms inside the bin can eat.

I knew that I couldn’t feed them:

  • bread
  • noodles/rice (at least not at first)
  • meat
  • eggs
  • cheese or any dairy
  • grease/oil
  • no anything that had animal product in it.

And I knew I could put some unexpected things in it like coffee grounds, in fact, coffee grounds are very good.  And tea bags. Definitely I could put

  • peels of any fruit of veg
  • cores or stems
  • fruits or vegetables that were starting to turn
  • tops of strawberries, trimmings from peppers, celery, carrots, any fruit or vegetable, onion peels

And I was told I should not put in:

potato peels, or potatoes.  Not sure why.  They just don’t break down.  And I learned from experience that avocado peels don’t break down easily.

Egg shells need to be crushed.  Corn cobs will break down eventually.

And the stickers they put on things these days have to be meticulously taken off.  If not, they will make your compost look like garbage.

And I do put in saw dust (we don’t get a newspaper) from time to time, but not on a regular basis.

I have heard that there had to be specific amounts of things that had to go in, but once my worms were established, I just check in on them every week-ish and if they look too wet, and if I have time I might get them some sawdust or shavings.  Truthfully, there are so many worms I do not worry about my amounts.  For about the first year I was totally astonished by how fruitfully they proliferated.  And all my scraps would just disappear, poof!

So after the box was made, I had to not get just any kind of worms, I had to get special compost worms called Red Wigglers.  Fortunately there was a guy selling them, because there was no one I knew who had worms to give away at this time.  They cost a lot, 15 dollars for 500… the most expensive part of the whole project, really so get them from a friend if you can.  I would happily supply worms to anyone who wants them.  I have gazillions.  I’ll even put them into your container for you.

Once I had the worms (he sold them to me in a Chinese takeout container), I knew I needed something for the little buggers to get started in.  I threw some leaves from the previous fall into the compost bin, and then some ripped up paper and then I went and made dinner and buried my scraps in the bin.

It is very important to bury the scraps.  They can attract bad bugs like flies, and then you will have maggots if you don’t bury the scraps.  Plus, it makes it easier for the worms to get to the food, since they don’t like light (the bin has to have a lid).

I knew I was successful when I saw the little tiny white things, which are the evidence that the worms are reproducing.

Your vermicomposting bin should never stink.  If it is stinking bad, then something is wrong.  To keep it healthy, it is a good idea to turn the compost over (I basically do this when I dig a hole to bury my compost) every now and then.  If it is goopy gloppy wet, get yourself some newspaper and give it a break from new scraps for a little bit.  If there is something molding and rotting, get it out.  If meat or animal product or poo got in there, get it out.  The worms can’t do anything with that stuff.  I wouldn’t apply pesticides near the bin.

If your bin is attracting too many bugs (very possible in summer months) put it somewhere that the bugs won’t bother you.  It shouldn’t be attracting flies, but potato bugs, slugs, crane fly larvae I have seen in there.  A spider or two is good to have around the bin.

Harvesting the compost can happen as early as 3 or 4 weeks.  Once the material in the bin is a dark in color, moist and thick, it is worm castings.

There have been 2 methods I have heard about.  One, which seems bizarre and trouble some is to pull out all the compost you want and put it on a tarp in a pile.  Apparently the worms should crawl out, and then you have nothing but compost.

The other way is to only dump scraps on one side for a few months so the worms will mostly go to the side with the fresh food.  This is the reason why one should get a larger bin than what they think they will need, because in order to harvest, you should be able to cut it in half.

I have heard that the red worms are considered invasive and that one should avoid having any in the compost that gets pulled out and used for gardening.  I have also been told that if they don’t have any food scraps to eat that they will die.   So far this hasn’t been my experience.  I have a few of the red worms that are now in my raised beds because my level best I still wasn’t able to keep them all out of the harvesting of compost process.  It might not matter at all, but I notice they are still there.  I have no idea if it will in the least effect my garden.

Alot of people think vermicomposting is something they can do on their regular compost pile.  I am not sure about this.  Every vermicomposting thing I have read keeps the worms contained.

I stole this info from

  • Worm composting (also known as vermicomposting) involves the breakdown of organic wastes via the joint action of worms and microorganisms (although there are often other critters that lend a hand)
  • Regular (soil and garden) earthworms cannot be used for worm composting. They will die if added to an indoor worm bin.
  • Soil worms will however congregate in the lower regions of outdoor bins (if open to surrounding soil)
  • Composting worms are specialized surface dwellers (not burrowers), typically living in very rich organic matter such as manure, compost heaps or leaf litter
  • Most common variety used is Eisenia fetida (also spelled ‘foetida‘), although it’s larger cousin, Eisenia hortensis (a.k.a. the ‘European Nightcrawler’) is commonly used as well (more commonly to be sold as bait worms)
  • Common names for E. fetida include: red worm, red wiggler, brandling worm, manure worm, tiger worm
  • You won’t likely find this species on your property (unless you live on a farm, or happen to introduce them into your compost heap).
  • Lumbricus rubellus is another species (and also a small reddish worm) sometimes used for vermicomposting, but is not as effective as E. fetida
  • It is widely believed that a composting worm can process the equivalent of it’s own weight in waste each day. Under highly optimum conditions (not likely to be attained with a small home system) red worms have been found to process multiple times their own weight! This is very much dependent on the foodstock and how well managed the system is.
  • A reasonable guideline to follow is 1/4-1/2 total worm weight in waste per day. So if you have a pound of worms, they should be able to process roughly 1/4-1/2 lb of food waste per day. Keep in mind however that you may need to feed them less during the first couple months since they usually require a period of acclimation when added to a new system.
  • Red worms technically graze on the microbial community that colonizes waste materials – not really the waste itself (although they certainly ingest some of the rotting waste in the process). Some research has indicated that protozoans are the primary food source, while there is also evidence that fungi and other microbes are consumed as well.
  • There have been a number of research studies indicating that vermicomposting can significantly reduce levels of pathogens in waste materials, such as biosolids.
  • Red worms love (and can tolerate) very high levels of moisture content (80-90%), but they also require oxygen so it’s important to find the right balance
  • One lb of composting worms is estimated to consist of approximately 1000 individuals, and can cost anywhere from $15 to $40 USD
  • Surface area far more important than depth when it comes to worm bins (ie tubs work much better than buckets)
  • Regular light is harmful to worms but red light is not
  • Red worm eggs look like tiny straw-coloured lemons
  • Baby worms look like very small versions of the adults (but have less red pigmen
  • Adding crushed egg shells (or other calcium sources) can help stimulate worm reproduction
  • Happy composting!

    5 Comments Add yours

    1. Chris says:

      I think I will try the big tub as well. I agree that I should get one that’s bigger than what I currently need. It’s enjoyable to harvest, but it’s also troublesome. Maybe it’ll be easier to have the worms migrate instead.

    2. Re your question about red worms being invasive- I believe that’s mainly in a forest setting where they “could” eat all the litter layer off the forest floor leaving it depleted of surface nutrients for feeder roots. In a garden setting, that is not the case. You still have worms in your beds as there is still enough organic matter to keep them there. You would need to continue top feeding if you want to keep them there; if not, they will die or move on to find food. They will not survive in plain soil.

    3. Roch says:

      Is there a link between the moisture and the appearance of mites in the bing? My bing is quite moist and there’s white a bit of those bugs in there?

    4. Ciska says:

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