The lowly worm gets almost no respect and is synonymous with an insult. This humble creature toils tirelessly eating the garbage of life and bulldozes its way through the dirt almost blindly, with no eyes or ears to guide it.
But, as you might guess, worms have an important place in every ecosystem. These legions of tiny diggers include over 5,000 species and, according to Charles Darwin, humans wouldn’t exist without them: “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures,” he once wrote.
Why compost with worms?
The good news is that you can harness this incredibly efficient composting power for yourself and change the way your family disposes of waste, with very little investment of time and money. A homemade worm composter costs about $30 and a luxurious store-bought worm hotel usually won’t cost more than $150. If you consider the cost of purchased organic fertilizer for your garden, even the most expensive composter could pay for itself in one growing season.
Worm composting, also known as vermicomposting or vermiculture, produces natural, odor-free compost that takes about 30 minutes per week to maintain. The biggest time investment is harvesting your worm castings (the precious poop/garden fertilizer), and that happens about every 3-6 months.
Can worms truly be the panacea of stink-free composting that many people claim? Yes, if you do things the right way. The proof is in how many municipalities promote vermicomposting as a way of diverting food waste away from landfills. Worm composting is now also used widely by large commercial dairy farms as one of the most efficient ways of processing manure.
Setting up your worm composting bin
At its simplest, a worm composter is a bin with holes for ventilation and moisture. It’s almost always made with plastic and raised off the ground to allow water to drain out the bottom.
For indoor worm bins, one DIY model is a plastic storage bin or tote with a lid. Simply drill a series of holes in the sides and bottom a few inches apart. Do not drill holes in the lid. Worms don’t need light, and even though there shouldn’t be much moisture coming out the bottom, the holes are there in case it needs to drain. The side wall holes are for better air flow.
If you decide you want your worm bin outside, many people have been successful using a simple wood box with gaps between the planks (like a pallet). This is lined with a heavy-duty plastic, such as greenhouse plastic, which is punctured with holes for drainage and airflow.
Elevation and design
Both types of bins need to be raised up. A DIY plastic bin can be set inside a slightly larger second bin, and many people recommend a large tote that will completely envelope the first bin. In fact, this design often leaves out the lid on the first, inner bin and uses the large lid of the second bin for protection. In my experience, however, I have found that this closed-up environment completely counteracts the ventilation holes and makes the bin retain too much moisture.
Instead, the Environmental Protection Agency has recommended a great DIY bin design with a short bin acting as a tray to catch any drippings from the larger bin. The one thing this design doesn’t include is elevation, which can be achieved by gluing a few small plastic food containers (such as for cream cheese or sour cream) upside down on the bottom.
The pallet bin should simply have one pallet on the bottom as the floor. With any worm bin design, the goal is good ventilation, darkness, and drainage.
What type of bedding is best?
The next step is bedding for your worms. You can use:
- shredded paper
- shredded cardboard
- egg cartons
I recommend leaving out the leaves and straw if it’s an indoor bin, because these materials can introduce insects and other outdoor creatures that you might not want reproducing inside your house.
Once you’ve prepared a nice bed, add a big scoop of garden soil. You can use a big juice pitcher filled with dirt, and then use the same pitcher to pour in some water. You want the moisture level to be the same as a wet sponge – not too wet, not too dry.
If you make the bedding too wet by accident, add more dry material and/or let it drip off. Don’t get anxious and add the worms before the bedding is right. I made that mistake once, and it was very difficult to bring the moisture level down later because adding food waste raises the moisture level dramatically in the bin.
Where should you put your worm bin?
We’ve talked about both inside and outside worm bins above, but they both have their pros and cons in any climate. When your bin is outside, there are two big benefits: capacity and a lot less attention to detail. You can put your worms out there and not have to worry so much about getting it just right, because it won’t matter if it smells a little more. But if you live anywhere other than very warm climates, your worms will either die in the winter or you’ll have to bring them inside anyway.
With an inside bin you can keep worms even in an apartment, but your capacity will always be limited – you will only be able to have a certain amount of worms, which will eat only a certain amount of food, or it will get stinky and go wrong.
If you’re interested in building a larger capacity outdoor system that works well for a larger home garden or urban farm, check out this design by Nature’s Always Right, an urban farm located in Lemon Grove, California.
Buying your worms: getting what you pay for
The type of worm most commonly used for vermicomposting is the red wiggler. That’s why this method of vermicomposting is also called red worm composting. The red wiggler species (Eisenia fetida) loves living in rotting organic material and manure and is extremely efficient at breaking it down. Unlike your typical garden earthworm, they don’t mind living in a small bin and won’t try to burrow down deeper.
Red wigglers used to only be available at bait shops for fishing, but today they have become so popular, there are many companies that will ship them to you by the bag. A pound of worms will eat their half their body weight in waste every day, so if you collect your food waste and weigh it, you can see exactly how many worms you’ll need.
A pound of worms includes about 1000 worms and should be more than two large handfuls. Here’s a video of what one pound of worms should look like.
It’s important to know how many worms you should be getting, because your worm bin could fail without this information. Twice my own worm bins had a fly infestation that compromised the bin. I couldn’t figure out why. It turned out that two different companies severely shorted me on the quantity of worms, because I had no idea what a pound of worms should look like. The result was that I put in far too much food for the worms, and the waste rotted and bred flies.
What should you feed your worms?
Worms can eat almost any fruit or vegetable food waste. Don’t give them anything that comes from an animal—no fats, bones, dairy, or meat. They also have a difficult time with some stems and the outer layers of onions, and they can’t handle too much citrus. If you have a bunch of orange peels or other citrus, make sure it doesn’t make up more than 1/5 of the total waste you are adding. Never give them dog or cat feces, or any carnivore feces. But you can add coffee grounds, filters, napkins, shredded paper towels, and non-plastic teabags.
To add food to your bin, dig a hole and bury it beneath the top layer of bedding. It helps if you break up the larger pieces. You should also add a handful of shredded paper and check if there’s something left over that the worms are avoiding from previous feeds. Remove anything they won’t eat.
As mentioned before, worms will eat half their body weight every day. However, when you first get them they will be a little slow to start. Begin with small amounts of food and check to see how long it takes them to eat it. Increase the amount until you are adding the equivalent to half their weight daily.
If they seem to be leaving a lot of waste, chop up the food you’re adding into smaller pieces. You can realistically expect one pound of worms to eat at least three pounds a week and twelve pounds of waste per month.
Troubleshooting worm composting issues
Being a stickler about how much food you add to your bin will help prevent a lot of problems. Here’s how to deal with common worm bin issues:
- Your worm bin has fruit flies: If you’ve already saved compost on your kitchen counter, you know how easy it is to get a fruit fly infestation. Prevention is key. Make sure to cover the food waste well under the bedding, cut it up into little pieces, and don’t let anything sit and rot in the bin.
- Your composter stinks: If your compost starts to smell, dig through the bedding and remove any food waste that appears to be rotting. The worms should really be eating anything before it can get moldy, but they may let something sit to soften up. For example, they probably won’t eat a whole fresh banana peel until it starts to break down and softens up. Cutting up larger pieces will help them process food faster. A bad smell can also signal a moisture problem. Too much rotting waste can create a lot of humidity, which will soak the bin and make it a little too damp for the worms. Add some dry cardboard and paper bedding to help balance things out and get the bedding back to a spongy moisture level.
- Worms are crawling out of the bin: It’s normal for a few worms to come out of the bin, but if you have a lot of escapees, you probably have an environmental problem. This will include moisture, temperature, and possibly even infestations. If the bin is too dry, add some water. If it’s too wet, add more bedding. Check for insect larvae or other issues under the top layer of bedding.
- There’s an infestation: Sometimes other creates will love the moist, dark environment of the bin— even just to lay their eggs. If you notice insects, eggs, or even furry creatures, take the bin outside and harvest the castings. This is a good time to clean out the bin and remove any rotting food or old bedding. Start off fresh and put the worms back in their home. If you had a rodent invader, hold the lid down with bungee cords or rocks.
Helping your worm compost thrive: amendments
If troubleshooting fails to correct your problem, consider adjusting your worm bedding with one of the following amendments:
|Balances out nitrogen-rich materials like kitchen scraps and grass clippings, controls moisture, and improves quality of worm castings.
|Glacial rock dust
|Enhances the microbial population, increases nutrients, and improves water retention.
|Increases air circulation, prevents matting, and controls moisture.
Harvesting your finished compost: lure vs. dump methods
There are two main ways to harvest your worm compost: by dumping it out completely or by luring the worms away from the completed compost. In my experience, the dump method is easiest if you have a small homemade bin. The lure method works well if you invest in a stackable system like the Worm Factory 360 Composter or the Eartheasy dual tray model, pictured above.
Composters like the Worm Factory 360 allow you to harvest compost from your bin easily, without dumping out the worms. They also remove some of the risk of stink by having a better drainage system than a bin with holes in the bottom.
As the bins fill with compost, you add another stackable tray on top. The worms migrate upstairs to the new layer of organic waste, lured by the presence of fresh food. The finished compost is left behind in the lower trays: it’s that simple.
The Worm Factory 360 also offers a refill kit that includes coconut coir, gravel rock dust and other materials that will help keep pH levels in balance and promote stink-free, aerobic composting.
To harvest compost from your homemade bin, the easiest method is to dump the contents upside down on a tarp in the sunshine or under a bright light. The worms will travel down to the bottom of the pile, which was your top layer of bedding (and the non-composted material). You are then free to scoop off the compost from the top of the pile and from around the worms.
This is a good time to clean out any unwanted bits using a worm composting sifter and add new, fresh bedding.
Where can I use worm compost?
Worm compost can be used like any high-nutrient fertilizer: sprinkle on the surface of the soil or mix in around plants, but be careful not to add too much because it can burn tender stems.
The liquid that drains from the bottom of the bin is a highly concentrated worm compost tea (or worm leachate). This tea should be diluted at a ratio of 1 part leachate to 10 parts water to prevent any burning.
If you really want to understand how vermicompost helps suppress plant diseases and provides nutrients to plants, check out this vermicomposting research from Cornell University.
Caring for your worms
If conditions are right in your composter, your red worms will breed when they are over two months old. That means your first batch should double their population within a few months. Don’t worry about overpopulation, however. If there’s not enough food, some will die and compost into the soil, keeping the bin in balance.
Worms can live four or five years, but they probably won’t last that long inside your bin. That’s why reproduction is an essential part of keeping your bin going. You may start to see baby worms right away. A Worm Factory 360 can hold over 10,000 worms, so it will probably take a while for you to get to the point that you’ll need a second bin. This is another huge benefit of the Worm Factory: it can hold 10x as many worms in an 18” space.
Check out these other resources to get started on your worm composting adventure: