Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
Organic gardening is very popular and with it, compost. But multiple, large compost bins are not an option for apartment dwellers or people living in communities with strict HOA rules. Vermicomposting, which is composting indoors with worms, is a good option. It’s not as icky as it sounds, and you may never have to actually touch a worm!
What is Vermicomposting?
Vermicomposting is a way of producing compost from vegetative matter using worms. The worms, bedding material and vegetative matter are housed in shallow bins that are kept covered because worms avoid light. The worms produce compost by digesting the bedding material and vegetable matter that is added regularly to the bin and excreting it as worm castings. After a few months, the resulting compost is removed and new bedding material and vegetable scraps are added for the worms to work on. A byproduct of the process is a dark liquid that can be used in the place of compost tea.
What Kind of Worms are Used in Vermicomposting?
The most commonly used worms in vermicomposters are red wiggler worms, the ones sold by bait shops. Red worms are also sold by online retailers and nursery suppliers.
More rarely, European nightcrawlers are used. In warmer climates, blueworms are used. Any kind of worm that lives close to the surface of the soil is suitable for vermicomposting.
Why You Can't Use Earthworms You Find in Your Yard
Earthworms commonly found in your yard and garden are hard workers. They also make compost by digesting vegetative materials found in your garden. They transport this compost from the surface by burrowing deep in the soil where they excrete their castings. The nutrients contained in the castings become available to plant roots. But that is exactly why they can’t be used in vermicomposters. Earthworms need deep soil. Vermicomposters are very shallow so worms that burrow shallowly in the soil work best.
How to Make a Vermicomposter
Vermicomposters can be purchased from Amazon and other online retailers as well as some local nurseries. If you are a DIY person, they are easy to make.
You can use almost any material to make your bin. Just bear in mind that metal will eventually rust and wood will decay. Some kinds of wood such as cedar and redwood have resins that harm the worms. Most people opt for plastic. An old Rubbermaid-type bin works fine.
The size of your bin is determined by the amount of vegetable waste your family produces in a week’s time. The best way to find out how much that is, is to collect a week’s worth of food waste and then weigh it. You will need to provide one square foot of surface area per pound of waste. A one or two person household produces an average of 4 pounds of food waste each week. An 8”x2’x2’ bin is the perfect size for a small household. For larger families, a 1’x2’x3’ bin will accommodate up to 6 ½ pounds of waste.
When constructing your bin, it is important that provide adequate ventilation so that the worms are not smothered. You will need ventilation holes in both the top and the sides of the bin. You should also have drainage holes in the bottom of your bin to collect that all-important “tea” that will form in the bottom of the bin. If the liquid is left in the bin, the compost and bedding will rot. Let it drain into a drip tray that you place under the bin specifically to collect the liquid.
What to Use For Bedding Material
You will need to provide bedding material for your worms. In nature, this is provided by leaves and leaf mold. You can bring some inside if you wish. Most people substitute shredded cardboard or newspaper. You can use anything as long as it can be moistened and remain fairly unmatted. Peat moss can be added to the bedding material to help with water retention and to prevent the bedding from getting matted. Moisture is critical because worms are 75% to 90% water. They will dry up and die in a dry environment. Keep their bedding wet to keep them alive. After you have wetted your bedding, throw in a couple of handfuls of soil and mix well. The soil provides grit that worms need for their digestion.
How Many Worms do You Need?
No one wants to count worms! Fortunately, they are sold by the pound. Remember that garbage that you weighed to determine how large your bin should be? It can also tell you how many worms to buy. One pound of worms can consume up to 3 ½ pounds of food waste per week.
Once you have your bin set up, dump your worms on top of the bedding, spreading them evenly over the top. Worms don’t like the light, so they will burrow into the bedding to get away from it. Once all of the worms have disappeared from the top of the bedding, it’s time to add your food waste.
What Can You Put in a Vermicomposter?
Basically anything biodegradeable can be put in your bin. Most people avoid meat, fat and bones because they are harder for the worms to digest and can develop bad odors while the worms are working on them. Kitchen vegetable scraps such as peels and cores are good. Eggshells are fine. Breads and crackers can be added. Even coffee grounds can be used.
Simply make a hole in the bedding and add your waste. Cover it with the bedding and then cover your bin. The worms will immediately get to work. You don’t need to do anything except resist the urge to check on them or stir their bedding. They work best if left alone except for your weekly additions of food waste.
How do You Harvest Your Compost?
After about a month or 6 weeks, you will notice that the bedding is brown and the worms aren’t converting garbage to compost as quickly. It’s time to collect your compost!
Here’s where it can get a little icky. There’s a hard way to do this and an easy way to do it.
The Hard Way
Spread a large (6’x6’) piece of plastic on the floor and shine a bright light on it. Remove the contents of your bin and make nine piles. There will be worms all through the piles but don’t worry. They hate light and will quickly burrow into the middle of the piles. When you don’t see any worms, carefully remove the surface of each pile, exposing the worms again. Place your newly collected compost in a plastic bag and wait for the worms to disappear again. Remove a second layer from each pile exposing the worms again. Keep doing this until all the compost is gone and only worms are left. Collect all the worms and weigh them. Because worms do die off and become compost you may have fewer and need to get some more. In some cases, the worms may have reproduced so you may have more worms than you started with. Place fresh bedding in your bin. Mix in some soil. Replace the worms. Add food waste. Continue adding waste weekly for another month to six weeks until you have to do this again.
The Easy Way
Instead of removing the used bedding and compost from the bin, simply push it all over to one side of the bin. On the other side, place fresh bedding and waste and cover your bin. In about a month, the worms will have all migrated to the new bedding and you can simply remove the finished compost from the bin. Easy peasy and you don’t have to touch any worms!
Vermicomposting indoors is a good substitute for composting outdoors. Using a small bin, some newspaper or cardboard, red wiggler worms and little patience, you can make nutritious compost for your garden.
Questions & Answers
Question: Is there any downside to vermicomposting outside?
Answer: Yes! The reason why vermicomposting is done indoors is that the worms will die in the winter outdoors both from the cold and because the food scraps you put in will freeze and the worms won't be able to eat them resulting in death from starvation.
Question: Why do some people think vermicompost is better than other types of compost?
Answer: As far as I know, people with no space for a composter prefer vermicomposting. Most people with space prefer composters although some of them use a vermicomposter instead. Some gardeners even use both.
© 2018 Caren White
Caren White (author) on February 23, 2018:
Natalie, I agree! thanks for reading and commenting.
Natalie Frank from Chicago, IL on February 23, 2018:
Not sure if I'm brave enough to try this. The thought of having a bunch of worms in my kitchen gives me the heebie jeebies! I'm such a girl! Thanks for the info though. I've been thinking of composting but live in an apartment. This gives me something to think about.