Ask the Experts:
Composting in Apartments &
Bear Country
Dear Dan,
I want to compost my kitchen food scraps, but I live in an apartment and only have a porch for outdoor space. A friend of mine lives in the mountains and is concerned about attracting bears with her backyard compost pile. Is there another composting option for us?
A: There IS another option, and it involves using little wriggly friends who will keep your compost pile compact and contained. They’re called red worms (Eisenia fetida), and they eat your leftover food and poop out a fantastic fertilizer. I think vermicomposting (composting with worms) is the best system for the majority of home composters because worms like to eat what we do, and they can be made comfortable in a wide variety of locations, such as inside the house, in the garage or onthe porch.
As an avid gardener, I vermicompost everything (including all my leaves in the fall) because of the wonderful worm castings I harvest. Worm castings (a.k.a. worm poop) make soil nutrients and beneficial microbes much more readily available to my plants than regular compost. They're the best compost in the world!
Q: Won’t the bin get smelly? And what about fruit flies? Will animals be attracted to my bin if it’s out on the porch?
A: Your compost won’t stink as long as it stays healthy. A small population of fruit flies is inevitable, so the best way to minimize this issue is to keep your bin outside. If you want to keep it indoors, choose a place where you can tolerate a few flies. You can keep their population in check by avoiding overfeeding the worms, which limits the amount of rotting material available for the flies to lay their eggs. Fruit flies also prefer a slightly acidic environment, so if you have more flies than you can tolerate, cut back on the amount of citrus, coffee grounds and other acidic foods in your bin. Or, build your own fruit fly trap.
Your worm bin is definitely a potential food source for animals like squirrels and, yes, even bears, if left outdoors. You’ll have to judge for yourself the level of bear activity where you live. If bears aren’t regular inhabitants of your neighborhood, you may be able to leave your bin outside undisturbed for much of the year and only bring it indoors in late summer and fall when bears are loading up on calories for hibernation. Squirrels are usually deterred by a good-fitting lid. Raccoons may be the most difficult to deter because they are so dexterous and persistent. If you see tooth marks on your bin or other evidence of a raccoon visit, bring your bin inside for a few weeks.
Q: How do I get started?
A: First, you need a bin. They are available online for anywhere from $50 – $200, BUT you can make your own bin for a fraction of the cost using an inexpensive plastic storage bin with a lid, like a 10-gallon Rubbermaid® Roughtote® storage box (see photo above) using these guidelines:
- You want to match the size of the bin to the amount of food scraps you generate. A typical storage box is a good fit for a two-person household. Allow 3 square feet of surface area in your bin for every pound of food scraps you generate per day, and any bin should be at least 10" deep.
- Worms require darkness, so you need a lid.
- Worms also need oxygen, so drill five holes on top and five holes in the bottom using a ¼" drill bit for every square foot of feeding surface area inside.
- The holes on the bottom will also serve to drain excess moisture (make sure they are at the low point!), so you need something under the bin to catch the leachate.
- It can be another container of the same size and shape as the bin on top.
- Don’t use treated wood or toxic finishes to build your bin.
Q: Where can I buy worms?
A: We recommend purchasing worms locally by heading up to Fort Collins to meet our local worm expert and Eco-Cycle® supplier, John Anderson (970-407-9076). A pound of worms (roughly 1,000 worms) is a good start for most households. You can also find several worm growers online if you search for “compost worms.”
Q: I have all my supplies. What’s the first step?
A: Have your bin ready before the worms arrive. Create a layer of bedding several inches thick using strips of moist newspaper. Mix in a small amount of soil or fin
ished compost for the worms to ingest into their gizzards—they need this to digest their food. Then add a small amount of food scraps and watch them go to work!
Ask the Eco-Cycle® Experts by writing to recycle@ecocycle.org with the subject line “Ask the Experts.”
© Copyright 2010 Eco-Cycle, Inc. All Rights Reserved
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Q: How do I know when it is okay to add more food? What can I do to make sure my compost stays healthy?
A: Use your nose! A healthy worm bin should smell like fertile soil. When feeding, don’t get too far ahead of the worms, especially when establishing a new worm colony. Wait until you see more castings than food at the top of your bin before you feed them again. Under good conditions, a worm can eat about half its weight per day. So, if you just bought a pound of worms, be patient and let the population grow. Worm populations can double every two months under ideal conditions.
If your bin smells overwhelmingly of rotting food, you are probably feeding your worms faster than they can eat. Remove excess food so that you don’t have more than a one-inch layer of food in your bin and keep an eye out for mold—worms won’t eat food once it spoils. The moisture level of your bin is also very important; make sure excess water is draining out of the bottom of your bin.
Maybe the best advice is to stay attentive. Don’t be afraid to gently rummage around in your bin to assess conditions. You are maintaining a whole ecosystem of critters when vermicomposting; the worms are just the most visible inhabitants. If the worms are climbing the sides of the bin in large numbers, they are trying to tell you that conditions aren’t right. Channel your “inner worm” and trust your instincts—you’ll keep everybody happy and healthy.
Q. How do I harvest the castings?
A: Worms live in the layer between finished castings (below) and food scraps (above), so unless you invest in one of the “worm condo” models that have drawers that can be removed once filled with finished castings, you will need to temporarily remove the worms and the layer of partially-digested food to get at the finished castings below. Keep in mind that worms respond to light by burrowing down (and faster than you might think), so make sure you are ready before you lift the lid. You’ll need a place to put the worm/food layer (the lid or a tarp), a container for the finished castings, a small garden fork, and a trowel.
- Remove the worm/food layer. Worms create colonies, so the less you disturb them when harvesting, the faster they can recover. Scoop out this layer as intact as possible and set it aside carefully. Do not put it directly on the floor—you’ll sacrifice too many worms trying to pick it up later. A garden fork works best to do this because it will pick up the undigested food and leave the finished castings. If you are leaving a lot of worms, go deeper. Expect to remove a layer about four inches deep.
- Remove the castings. You may want to switch to a trowel for this step. You will probably see some worms down in the castings layer, but more than 90% of them should be in the food layer.
- Put the worm/food layer back in the bin, again as intact as possible to minimize disturbance.
- If you feel that too many worms are left in the finished castings, you can recover them by piling up the castings in a conical shape. Gradually skim a layer of castings off the cone as the worms burrow away from the light. (Hint: a strong light or bright sun makes this go faster.) When you start to see worms again, back off and wait for them to burrow further. If you are patient, you will eventually end up with a small pile of worms at the very bottom and a big pile of worm-free castings. (But, don’t be TOO patient. Finish this process in a few hours at most and get the worms back in the bin.)
Q: I read that newspaper ink can be harmful to the worms. Is that true, or can I use it as bedding?
A: This was true back when newspaper ink contained lead, but newspapers these days are printed with inks that are not toxic to worms. Home vermicomposting guides commonly recommend that you use wet strips of newspaper as the initial layer of bedding for the worms when starting a new bin. This creates a stable environment that helps the worms to stay moist, move about, and begin to build their nests. Once the worm bin is established, the worms bed in the zone between the castings (below) and the food (above) and no longer need the newspaper.
Q: What can I do about fruit flies?
A: A small population of fruit flies is inevitable, so the best way to minimize this issue is to keep your worms outside. Outdoor worm bins in Colorado must be in a bottomless bin (with the ground as a floor), so the worms can move up and down to moderate their temperature. But, attached garages usually have an adequately consistent temperature to maintain a fully-contained worm bin.
If you want to keep your worms indoors, choose a place where you can tolerate a few fruit flies. You can keep their population in check by avoiding overfeeding the worms, which limits the amount of rotting material available for them to lay their eggs. Fruit flies also prefer a slightly acid environment, so if you have more flies than you can tolerate, cut back on the amount of citrus, coffee grounds and other acid foods for a while. Or, build your own fruit fly trap (link to directions).
Q: I was planning to save my food scraps in the freezer and add them weekly. Is that okay?
A: Freezing food is fine. In fact, the act of freezing and thawing “pre-digests” the food and allows the worms to eat it faster. Just be sure to gently mix the thawed food into the top inch of food scraps in your worm bin—a big glop of thawed food will spoil and your worms will avoid it.
Q: Can I feed my worms processed food? It’s not good for us, so it can’t be good for them, right?
A: Ha! Good question, and I can certainly see the logic. I don’t know if anyone has studied whether worms turn into obese couch potatoes on a steady diet of nothing but junk food, but worms and the universe of other micro and macro critters that live with them are capable of breaking down any organic matter, no matter how processed or unappealing. (Their favorite food is manure, and you wouldn’t eat that either!) It’s important to remember that worms are only the most visible part of the ecosystem in your worm bin. The microbes that live in their castings (and that we use to make our compost tea) are some of the same microbes that are now being used to clean up the most toxic sites on earth, like abandoned mines and brownfield sites with severely contaminated soils.
On the other hand, there probably is an “ideal” recipe for feeding your worm bin to maximize the casting quality, as well as worm health. I haven’t seen this quantified anywhere, but my own experience is that a consistent diet of diverse food sources works best.
Q: What kinds of foods should I vermicompost? I've heard that I should avoid putting meat and oil in my bin and that citrus, onions and bread should only be composted in moderation.
A: “Everything in moderation” should be your mantra. Worms always go through an adjustment period if you change their food, and drastic changes can actually be toxic to them, killing them or driving them out of your bin.
Two factors to keep in mind when feeding are salts and pH. You don’t want to overwhelm the worms with an unusually high dose of salt or salty food, such as the brine from a big batch of sauerkraut or the leftover crust from cooking a salt-encrusted roast. Similarly, don’t dump all the lemon rinds from a big batch of homemade lemonade into your worm bin at once. Onions by themselves are also a pH issue.
Bread and starchy foods by themselves are higher in carbon than an ideal mixture of diverse foods (too much “brown,” not enough “green”), but moderate amounts are fine, especially when chopped or shredded to reduce their size, then mixed with other stuff.
I don’t tell people to avoid any of the above foods because they might decide worms are too picky to be worthwhile, and that’s just not true. I do tell serious gardeners who process a lot of food for canning and storage to think about pH before they dump in large quantities of any one thing.
I do advise no meats or oils in an indoor bin (beyond a little oil coating leftovers such as dressing on salad or oil on a stir fry) because they are too complex to break down quickly and can definitely cause trouble in a small bin. Advanced worm ranchers with bigger bins can do meats and oils just fine.
© Copyright 2010 Eco-Cycle, Inc. All Rights Reserved
No part of this publication may be transmitted or reproduced in any form without the express permission of the publisher.
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