Vermicomposting: Step-by-Step Guide

Learn how to create your own vermicomposting system at home.

Worms in a feeding tray with fresh food and bedding material in an outdoor vermicomposter.
Ashley-Belle Burns / Getty Images
Overview
  • Working Time: 2 - 6 hours
  • Total Time: 1 week, 3 days - 3 weeks
  • Yield: 2 cups of compost on average per week
  • Skill Level: Beginner
  • Estimated Cost: $20-200

Vermicomposting is another name for composting using worms that eat your food scraps and then excrete nitrogen-rich castings. Those castings make excellent fertilizer that you can add to potted plants, a container garden, or an in-ground garden.

Vermicomposting is a great alternative for people living in apartments, tiny houses, or any other space where you don't have access to a backyard to make a regular composting pile. You can keep a vermicomposting system going under your sink or in a cupboard—worms like darkness anyway. This type of composting is easy to do and a very kid-friendly activity.

There is variety in size and complexity of vermicomposting systems. Some that you buy have many trays and levels, while others are quite simple. To start vermicomposting, you don't need the bigger or more complex systems, which are most useful if you have a lot of food waste. For an average home with 1-4 people, a simple system as described below is a great place to start learning—you can always up your complexity later.

What Is the Difference Between Vermicomposting and Other Composting Methods?

The most significant difference is that instead of relying solely on bacteria and other microorganisms to break your food scraps down, vermicomposting relies on a special type of worm.

In addition, a vermicomposting system encloses those worms in a set of buckets or boxes that fit together, so it requires some specialized equipment that you can buy or make yourself (more on that below).

While vermicomposting does require a specific set-up and worms that you'll need to buy either online or at a local garden supply store, it has the advantage of being compact and really easy once you get it going.

What About the Worms?

hands holding out brown dirt and red wiggler worms for vermicomposting

Treehugger / Christian Yonkers

You can't just use any kind of worm in a vermicomposting system. While some people have reported success using earthworms, the most common are the petite redworms, also known as red wigglers.

These worms are available online and at local garden stores and they're not too expensive, about $30-$40 for a pound of worms, which is the amount most people start with. Importantly, the redworms need to be kept relatively warm but not too hot, at about 55 F to 85 F—and they need a little moisture.

These worms will reproduce quickly—every two months they'll double in number. That means you will only have to buy them once and can expand your vermicomposting system pretty easily once it gets going.


What Materials Can Be Composted?

Vermicomposting is a little different from other types of composting in terms of what materials can be processed. Because it's much smaller than a backyard composting system, you aren't going to be able to throw garden or yard waste like bags of dried leaves, branches, or other large debris into the system. Vermicomposting is more about utilizing food waste that you generate in your kitchen.

That being said, you can certainly compost some leaves or small branches that you might trim off your houseplants, but the volume needs to be quite low.

You can feed the worms fruit and vegetable scraps like potato peels, apple cores, and cooked veggies or fruits as long as they haven't been cooked with oils. Coffee grounds, tea bags, loose leaf tea, and eggshells are all also suitable. You can add some citrus fruits, but not too many as they take a lot longer to break down.

Meat, bones, dairy products, or oils (even vegetable oils) can't be digested by the worms, so keep those out of your bin.

What You'll Need

Vermicompost Container

  • Tank or plastic container (10-gallon size)
  • Plastic bag (20-gallon size) if needed for lining
  • Digital scale

Supplies

  • 3 cups potting soil
  • 50 pages newspaper (black and white only)
  • 3 tablespoons water (or more)
  • 1 pound redworms

Instructions

  1. Choose a Space

    under wooden cabinet door ajar revealing storage space for vermicomposting

    Treehugger / Christian Yonkers

    If you are vermicomposting, it is likely you have limited space. First, think about location—ideally, you want your system close to the kitchen where you produce your food scraps (aka worm food). A closet or pantry area in your kitchen could work, but perhaps a large drawer or under-sink area would have enough room.

  2. Measure Your Space

    person crouches down with tape to measure under-cabinet space for vermicomposting system

    Treehugger / Christian Yonkers

    Once you have chosen your space, take a careful measurement of the height, depth, and width of the area you have. You'll need room for at least 10 gallons of volume, or something equivalent to 16" x 24" x 8." Remember to take into consideration if a door or drawer closes over the area, as that could take some 1/2 inches away from your space.

  3. Make Your Vermicomposting System

    vermicomposting setup includes a large plastic bin, plastic liner, newspaper, and food scraps

    Treehugger / Christian Yonkers

    If you are ordering a vermicomposting system online, you just need to choose one based on the limitations you may have in terms of size and budget. Different systems can run between $150 to $300 or more.

    You can also make a vermicomposting system pretty easily using some simple plastic containers, a glass container (like an old fish tank), or even a wooden box (like an old drawer). If using wood, you'll need to line it in plastic (a thick garbage bag or old shower curtain liner can work).

  4. Order Your Worms

    Once you have the space organized and you've chosen or made your vermicomposting system, it's time to order your worms. Some online systems come with starter worms, so double-check so you don't end up with too many worms. Start with 1 pound of redworms.

  5. Start Saving Up Food Scraps

    overhead view of clear glass bowl holding food scraps and egg shells

    Treehugger / Christian Yonkers

    You'll want to have something to feed your worms as soon as they are set up in your system, so a few days before they arrive, start collecting your compost. Refer to the section at the top of the page for more details on what they can and cannot eat.

  6. Set Your Vermicomposting System Up

    hand with glass bottle sprays shredded newspaper with water in compost bin

    Treehugger / Christian Yonkers

    The day before the worms arrive: Use the newspaper you've collected to create a bedding for your worms inside your containers.

    Tear about 50 pages of newspaper into 1/2" to 1" strips and add water until it's very damp—but not dripping (like a damp sponge.)

    Your bin should be about 3/4 full of the damp newspaper and it should be fluffy, not packed down.

    Add 2-3 cups of soil (potting soil or soil from outside) to your bin, sprinkling it over the damp newspaper so it is evenly distributed. The soil contains beneficial microorganisms and grit that help the worms digest their compost food.

  7. Add Your Worms

    hand adds red wiggler worms to damp newspaper and food scraps compost pile

    Treehugger / Christian Yonkers

    Once your worms' home is all prepared, weigh or measure the volume of your worms and write it down. Then add your worms to the box or container. No need to add more newspaper—they will make their own way under the newspaper layers. (Make sure it's still damp since the worms breathe through their skin and they need moisture for that process).

  8. Feed the Worms

    You should add compost to feed your worms at least once a week. They can go as long as two weeks without fresh food if you are traveling, but that shouldn't be until they are well-established.

    Measure the compost first—worms need about 2:1 ratio of worms to food. That means if you have 1 pound of worms, they can eat 3.5 pounds of compost a week. That's what 2-3 people will generate in a week, but of course, that depends on your household. Once your system is going you won't have to measure every time, but while you are learning, try to stick to the 2:1 ratio.

    When you feed your worms, make sure the compost is broken or cut into small pieces. Open the top of your bin, and remove the bedding that's on top of the worms or push it to one side, add compost, then cover it with the bedding. Use a different location to add compost each time, rotating around the container. You will notice younger worms will gravitate to certain foods, while older worms will like others. Noticing who likes to eat what is a fun part of vermicomposting and something kids can keep track of.

    Especially at the beginning, you'll need to monitor how much compost the worms are making and if they are getting enough food and moisture.

  9. Maintain Your Vermicomposting System

    hand adds more compost to red wiggler and food scraps compost bin

    Treehugger / Christian Yonkers

    Worms don't like to be disturbed too much and like their quiet, dark space to do their work. So when you open the box to add compost, that's also a good time to check that the bedding is remaining damp enough. Keep a spray bottle nearby to quickly and easily wet down the newspaper when necessary.

    This is also a good time to fluff the newspaper to ensure that plenty of air is getting into the system. You don't want the bedding to get flattened down, as it's there to provide cover, moisture and help circulate air above the composting food and the worms eating it.

    If your worms reproduce over time, they are getting enough food. Their numbers will decrease if they are not getting enough. You can tell if worms are sick or dead by shining a bright light into their box. Healthy worms will move away from the light. If they stay on the surface after a few minutes, they are unhealthy or deceased and should be removed.

  10. Change the Bedding and Harvest Castings

    hand holds out cupful of worm casting from vermicomposting

    Treehugger / Christian Yonkers

    You can harvest castings and vermicompost as soon as you see it at the bottom of your container, which could be as fast as 7-10 days. Some people will wait until they change the bedding. Some of the bedding itself will compost over time, but some of it will turn brown and tend to get packed down. It will need to be replaced every 4-6 months. To do this, put a sheet of plastic out and dump the contents of your worm box onto it.

    Shine a light (or do this in front of a window), and the worms will tend to bundle together in the castings and whatever compost is left. Pull out the old newspaper and discard, and add new newspaper to the bin, spray it down, and add some of the soil and compost back (2-3 cups like when you initially began the bin), along with your worms. If it seems like there are many more of them than when you started, weigh them quickly and see—you might need to add more compost if your worm population has doubled.

    Harvest the castings, your compost reward, and keep it in a bag or bucket, or use it right away.

  11. Use Your Compost

    hand scoops vermicompost from blue bowl into potted plant

    Treehugger / Christian Yonkers

    Vermicompost should be added to soil or potting soil at about 10% vermicompost to 90% soil. Simply mix it into your soil when you are repotting plants, or sprinkle it into the soil and water it in if you have a container or in-ground garden.


Frequently Asked Questions

Do you have to use newspaper as bedding?

No, you can use dry leaves from your back yard, torn-up cardboard, paper bags, or a combination of all the above. All materials should be shredded and kept damp as the newspaper would be.

Do the worms sting or bite?

No, redworms don't have teeth or any way to sting or bite. Their mouth ingests food and it gets ground up in their gizzard (a type of modified stomach).

Can you do vermicomposting outdoors like on a balcony or in a garage?

Yes, you can, but only when temperatures are warmer than 40 F and don't go over 80 F. Worms definitely need to be in a shady spot and out of any direct sun.