Vermicomposting

Make sure you’ve read PART ONE of this series, where we discuss what goes into the compost. And check out PART TWO too to learn about backyard composting methods.

Vermicomposting is the process of using specific worms to compost kitchen waste in a designated container. Worm bins can be kept inside or outside (with a little protection). You can even have a designated worm bin for pet waste - but you shouldn’t use the castings on edible plants.

Vermicomposting is one of my all time favorite ways to compost. Worm castings (read:poop) are absolutely AMAZING for your garden. And they require very little time commitment to create.

There are a few ways to have worms at home. You can build a box out of plastic storage boxes or purchase a premade system like the Worm Factory 360. The important thing is that the container allows air flow, is dark, has a good amount of surface area, and can be easily washed.

Set Up

1. Once you have bought or put together your worm bin, cut, tear or shred newsprint or cardboard into 1” or smaller pieces or strips. You’ll need to fill about 3/4 of the bin with the paper material.

   NOTE: You should only use matte newsprint or cardboard as they are printed with a soy based ink. Shiny paper can have chemicals that would be harmful to the worms or your garden. You can also use egg cartons, grocery bags, toilet paper rolls etc. You CAN use leaves, straw, and other outdoor carbon material but it can introduce pests into your bin. If you plan to use the bin inside, I recommend only using paper/cardboard.

2. Moisten the paper material to be damp but not wet. Like outdoor compost, it should be no more wet than a wrung out sponge.

3. Mix the paper with a handful or two of potting soil. This is necessary when starting a bin to ensure you have grit for the worms to digest food and have introduced the beneficial microorganisms into the bin.

4. Add worms. The amount will depend on how much waste you want to convert and the size of your bin. Generally you’ll need 1/4-1/2 lb of worms per square foot of surface area. I like to err on the smaller amount since worms will multiply quickly when they are happy in the bin. Worms can eat 1/2 their weight in a single day so if you have a lot of waste to process, you’ll likely need a large bin.

5. Wait a couple days to let the worms acclimate to their new environment

6. Add food scraps! Bury the scraps under the paper to keep smells at a minimum.

   1. Like outdoor composting you don’t want to add anything that will be stinky. No meat, bones, greasy foods, or dairy.

   2. I’ve found that worms don’t particularly like potatoes, too much citrus or onion. They love avocado but the peels take a VERY long time to break down.

   3. Worms ABSOLUTELY LOVE melon, pumpkin and other winter squash, banana peels, and coffee grounds.

   4. The smaller the food pieces, the faster they will eat it.

7. Cover your bin. You can place a layer of cardboard or paper on top to help keep the worms and moisture in. Then cover with the lid to the box.

Rubbermaid System

Use one or more dark storage containers. Drill many holes into top and bottom for airflow and drainage.

Stacking System

Stacking systems like the Worm Factory 360 have a small footprint. They stack 3-6 trays high.

Set up

You can line the bottom of your trays with any compostable material. This helps soak up excess moisture and helps keep the worms contained.

Set Up

Use paper, cardboard, or other compostable browns to set up the bedding for the worms. It should be moist but not too wet. When you squeeze it, water should not come out.

Set Up

Fill your bin 3/4 full with the moist paper. Sprinkle on some potting soil and ground up eggshells to aid in digestion.

Feed

Choose a corner to start in and feed in a circular direction. The food in the first location should be indistinguishable by the time you feed there again.

Feed

If you have a lot of worms, you can also mix in a larger quantity of food into the bedding. Feed again once most of the food is indistinguishable.

Feed

Make sure to top any food material with more browns. You can also use a folded newspaper or other compostable packing material to cover the whole bin.

Happy Worms

Worms will form a worm ball when they find something they really like to eat like melon and pumpkin.

Harvest

When your castings look more like soil than objects, it’s time to harvest. Stop feeding the worms or push all of the finished material to the side.

Harvest

Once the castings are done, create small cone shaped piles to separate the worms.

Harvest

Place your castings in a bright area so the worms migrate down as you remove the top layer.

Harvest

You can lay your castings out to dry or use them wet the sift them through a 1/2” or 1/4” sifter. Castings should have no identifiable food in them. Using castings outside without separating the worms is ok too.

Harvest

It’s ok if the castings are wet, but they shouldn’t be dripping. When you squeeze them in your hand they should hold their shape.

Troubleshooting

Worms love to climb on anything wet. It’s totally normal for them to climb on the walls. If they are leaving the bin, you may not have hospitable conditions. Check if it is too wet or too dry.

Feeding

You can feed your worms in a couple of ways.

1. This is the best way to feed your worms in a new bin. Start in one corner of your bin and bury a small amount of scraps. Continue feeding in a circular pattern burying the scraps one corner at a time. Continue adding dry bedding (carbon) on top of each feeding location. By the time you get to your starting position, the food should be gone. If it is not, wait until it is mostly unrecognizable and then continue feeding.

2. This one works if you have a lot of worms. Collect a semi large quantity of food scraps. Mix it into your bin with dry bedding then cover with dry bedding. Wait a few weeks for the food to become mostly unrecognizable and then repeat.

Harvesting

You’ll know it’s time to harvest when your bin looks primarily like rich, dark soil. This usually takes between 3 and 6 months.

If you have a single bin system:

1. Push all of your material to one side of the bin. Fill the rest of the bin with fresh bedding and food.

2. After 2-4 weeks, remove all of the finished compost from the bin.

3. Stack the compost into 4-6 cone shaped piles somewhere bright.

4. Remove the top layer of compost picking out any unfinished pieces and worms.

5. Let the pile sit for 2-5 minutes while the worms migrate down.

6. Repeat the process until you are finished separating the compost.

If you have a multi bin system:

1. Once your bottom bin is full, place your second bin on top.

2. Fill the second bin with bedding and feed it as you normally would.

3. The worms migrate up through the system and start feeding and living in the new bin.

4. As the bottom bin finishes, continue feeding and stacking bins.

5. When your top bin is close to being finished, put all of your castings into a container with a loosely fitted lid.

6. If desired stack the compost into piles to separate the worms.

Troubleshooting

Sometimes issues arise when you have worms in the house. Below are a few things that could happen, and what to do when/if they do.

Using Castings

Make sure to check out our blog post on fertilizing your garden with worm castings!

WHEW!!! That was a lot!

Questions? We’re always around to help out.