Category Archives: Practice

Worm Composting in Theory and Practice

One of my worms in what used to be vegetables, used teabags, eggshells...

This used to be vegetables, used teabags, eggshells…

Last year we decided to take up a hobby we had been thinking about trying since way back in my first year of grad school: vermicomposting. Back when we moved to Ithaca for my start at Cornell, we spent our first few days in Ithaca staying at the house of a graduate student in plant biology who had two trashcan sized vermicompost systems in her basement. Ithaca’s garbage pick-up incentivizes waste reduction through a system of trash tags, and so when our host pulled back the lid to show us the rather squirmy mass that consumed her kitchen scraps, we were certainly intrigued. Her advice was to take one of the classes in worm composting offered through Cornell Extension, because while worm composting is fairly simple, it can be done wrong. And besides, I would get everything I needed in the class: a bin, bedding, and a starter herd of worms.

The idea sat on the back burner for a while, and as it did plenty of compostable kitchen scraps went off to the landfill (probably about 1,700 pounds in those years…a side effect of this project is that I know how many pounds of kitchen scraps I produce in a week). This is bad because space in landfills is finite, but also because when organic materials decompose in landfills, they release greenhouse gases that contribute to global warming. Feeding my garbage to worms instead quickly transforms kitchen scraps into nutrient rich worm castings. It also eliminates the problem of wasted food.

Recently I harvested our first round of compost. We don’t have a garden, and only

Cat grass growing in compost.

Cat grass growing in compost.

a few houseplants, so we use it instead as potting soil for cat grass. A red worm composting system is an ecosystem in its own right, and as I’ve seen it evolve I’ve thought a bit a lot about the unexpected pleasures of having a box of worms cut down on trash.

Ingeborg and Babette enjoying some cat grass last Christmas.

Ingeborg and Babette enjoying some cat grass last Christmas.

The Theory

When I put my own guests in the position that my host put me in back in my first days in Ithaca, the responses are mixed. Apparently peering into a box full of worms eating trash is not everybody’s cup of tea. But the fascination for me has been in maintaining an externalized metabolic system: maybe I won’t eat that mushy apple, but they will. And it is not just them. A worm bin is an ecosystem in which other small organisms develop. Flies were a minor nuisance in the summer, although they were gone by winter. It also interesting to see the afterlife of some of my vegetables. The bell pepper seeds in particular tend to sprout; after a week the seedlings are all that is left of what didn’t go into that night’s stir fry.

Processing part of my waste in my house is the other pleasure of worm composting. In the past I would buy something appealing at the grocery store, and then whatever I didn’t consume would go into the trash, turn into a foul smelling slop, and then be out of sight and out of mind when the trash truck came. Owning at least part of my garbage is far more satisfying than banishing it to some liminal place that I never visit. And there is a fascination to the thought that I can grow something for my cats in what used to be teabags and vegetable peelings. Yes, the final link in the metabolic chain is that the worms eat what I don’t as to produce compost that I then use to produce grass to aid the cats in their own digestion.

The worm box is also a pleasant reminder of just how noisy nature is. If one stops to listen, one can easily hear their rustle.

The Practice

Worm composting can go wrong. The best species for worm composting, red wigglers or eisenia fetida, are very tolerant but will try to escape en masse from a bin where conditions have turned toxic (plenty of horror there for anyone who cares to look it up on Google). In the end we did not take a class, but there are plenty of resources on the internet that are helpful. Bentley Christie maintains this helpful website, while there are plenty of online forums and instructional videos on YouTube. While there are many good resources, there are plenty that might be wrong or cause unnecessary worry. I spent a lot of time trawling websites early on whenever I encountered a perceived problem. The rest of this post will sum up a few of the hurdles encountered along the way.

  • Bin Setup: The first decision is whether to buy a readymade system or to make your own. A readymade system costs around $100. I set up my own system with roughneck bins, which cost under $10 a piece, depending on size. I built a three tier system, with the lowest tier collecting the liquid, but there are variations. Again, plenty of instructional materials on the internet. I built something based on  this and this.
  • Buying worms. I ordered from a supplier online, but there are smaller organizations in many areas that sell. If ordering, it is best to order from someone geographically proximate. The less time the worms spend in the mail, the better.
  • The first weeks.  I ordered from a large farm, and that caused a few problems. The worms were used to a large bin, and so they wanted to explore. Red worms are photophobes, and so I kept them under constant light for the first two days in order to discourage them from exploring up and out of the bin. This trick worked.Ventilation was another problem I had in the beginning. At first I kept a lid on my bin. This trapped a lot of moisture, and that, in turn, encouraged the worms to crawl up and out. Since it was summer, too much heat and moisture might have been getting trapped inside as well. I started finding worms that were dying a most gruesome death. This is often a result of overfeeding and acidification, and I worried that I was overfeeding. But the bin was not smelling bad. It seems that this problem is common in the beginning. Worms at worm farms eat horse manure, and switching to kitchen scraps does not sit well with some of the population. I don’t know if this was the issue. I took other steps to improve the environment in the bin. For one thing, I switched to an open system. Instead of a lid, I put a thicker layer of bedding on top (a mix of shredded newspaper and cardboard) and left the lid off so that the system could breathe. In any event, the dying stopped by the third week.Pests have not been a problem. When my bin was too wet I would see a lot of mites. Mites are not bad, but their presence did tell me I needed to keep the lid off, and I stopped noticing them once I did. Fly larvae was also a problem at first, but they went away too.

    All in all, it takes the system a few weeks to sort itself out, and one has to be patient.

  • Adding garbage. In my house we produce about five pounds of compostables a week (yes, I’ve weighed it). Worms will eat most anything, but not everything that could go into other types of systems should go into the worm bin. Meat and animal waste are self-explanatory, but citrus can make the bins too acidic. Coffee grounds, I am told, also can be acidic, but those can go straight into the garden. Starch is something one should avoid, so stale bread and potato skins are still heading off to the landfill.
  • Going away. I left the bin alone for a month relatively early on. This is a long time, and I had nobody to look after it. When I got home I found that the worms were fine, and that a good layer of compost had developed. My impression was that there were fewer, and indeed their population may have gone down with the lack of feeding, but if so then they quickly bounced back.
  • Storage. In the summer I kept the bin in the basement, but when the temperatures began dropping in fall I moved them to a dark part of my apartment, where they now stay. Excessive heat and cold are obviously bad, and when I was convinced that the bin would neither stink nor attract a lot of pests, I decided it could live inside

The bottom line is that the biggest challenge starting out is to resist the worry. None of the mistakes I made early on were catastrophic, and some minor changes, such as increasing the amount of bedding and leaving the lid off helped the system to stabilize. As I said, it consumes about five pounds of compostables a week, and it could take more!