How to Make Vermicompost

Before you gather your tools, watch this video and read through the instructions below. There is a lot of flexibility in this design and if you choose to make changes this will affect necessary tools/supplies. Here is what I recommend:

• Something to house the worms. There are many options. My favorite is to buy a pre-fabricated worm bag that can be stored indoors, such as this worm bag from Urban Worm Co. But you can certainly make your own or buy another option. No matter what housing you choose, the concepts listed here will apply, though perhaps in larger or smaller quantities. Scale up or down as necessary.
• A minimum of approximately 100 individual worms, ideally one pound of Red Wiggler Worms (Eisenia fetida) – I will include an option for vendors in Appendix
• Bedding/ brown material/ carbon rich material
  • Shredded newspaper
    • I recommend an electric paper shredder for the newspaper though you can also use scissors or tear the paper apart with your hands
  • Leaf mold/ old leaves
  • Cardboard (corrugated, not smooth like cereal boxes)
• Food/ green materials/ nitrogen rich material
  • Spent coffee grounds
  • Used tea bags
  • Leaf mold or old leaves
  • Vegetables
  • Fruit.
• 2 cups of forest soil of formerly inoculated compost
• Clean water
• Soil thermometer
• Spray bottle
• Measuring cup

NOTE: leaf mold can be used both as bedding and as food.

Step 1: Construct the Housing

We have experimented with various housing for the worms. After trial and error, we came to the conclusion that the prefabricated worm bags are the best, easiest option. These kits contain instructions for how to put them together. Follow the included instructions.

This may not make sense for your given needs. There are many articles and videos online showing other options. The key tenants for any housing option are that it must have air holes, must stay relatively dark, and should have a way to harvest the finished compost (worm castings). If you are short on resources, you can use a Rubbermaid bin with holes punched around the upper sides of the container. I have done this, and it works, though it is challenging to harvest the castings.

Whatever you use, make sure you can keep it safe from weather extremes. Worms can freeze in cold temperatures and overheat in hot temperatures. We once lost half of our entire vermicomposting operation when our warehouse heated up during the summer. This was a tragedy. Since then, we have kept all our vermicomposting operations in a climate-controlled room.

Step 2: Add the Bedding

The goal is to produce enough bedding to fill approximately 1/4 of whatever housing option you choose. We will add more to this as time passes. To produce the bedding, we will do the following:

First start with these materials:

• Shredded newspaper.
• Shredded leaves or leaf mold.
• 2 cups of forest soil (or compost from the Johnson-Su Bioreactor if you have made this)
• You can also use shredded corrugated cardboard if you would like, but make sure to first remove packaging tape.

These ingredients represent most of our total material. They should be pre-wetted in untreated water (or water that has been purified of chemicals - see the book for more details). You can either soak them individually or soak them as a group.

The ingredients above will be mixed with the following list of ingredients at a ratio of 50 to 1. In other words, the above materials will represent the 50 and the following list will represent the 1: coffee grounds, used tea bags, vegetable, grass clippings (must not be treated with herbicide or any chemicals), fruit, and vegetarian food scraps.

How much you need will depend on how big a container you are filling.

Mix everything together and squeeze out the excess water before adding it to your worm housing. By the time you put this into the container, there should only be a few drops of liquid coming off of them, at most. Place everything in your worm housing. Let this sit for 2 – 7 days before adding the worms.

Step 3: Add the Worms

Add 1 pound of worms. Place them directly on top of the bedding. They will burrow below the surface on their own. The worms may not acclimate at first, but over time they will. If they are hanging about near the surface, shine some light on them. Worms do not like light, and this will help drive them deeper into the pile. Over time these worms will reproduce and die and should maintain a healthy population within this environment.

Finally, I recommend adding a weather-resistant tag or label to the housing showing the date the worms were added.

Step 4: Maintain Temperature & Moisture Every Week

The temperature within the bag should be kept between 55-80°F. 70°F is optimal. This is why I prefer to keep vermicomposting operations in a climate-controlled indoor space.

Check the temperatures weekly with a soil thermometer. Keep the thermometer in place for at least 2 minutes for an accurate reading.

Moisture within the bag should be maintained at 60-70 % humidity. If you grab a bit of material from the top and squeeze it tightly, you should be able to extract only a small amount of water. The video above demonstrates how much. Any more and it is too wet. Any less and it is too dry. I would not rely on a moisture meter for these readings. I have found these tools to be inaccurate, even when properly calibrated.

If moisture is lacking, use a mist/spray bottle to soak the surface with untreated/cleaned water. If there is too much moisture, add extra bedding that hasn’t been pre-wet to absorb some of the moisture.

Step 5: Feed the Worms As Needed

When you add food, give them things like leafy greens, strawberries, bananas, melon, used tea bags, and used coffee grounds. Have some fun. Experiment. See what they do and do not eat. Worms definitely prefer some foods over others.

Some very important points to keep in mind:

• Do not feed them onion, citrus, meat, oily and greasy food, human or pet waste, poisonous plants, bones, spicy foods or peppers. These could harm or kill the worms.
• Do not feed them rotten food. Doing so is not good for them and could introduce other unwanted pathogens

I find that it is helpful to keep a log next to the housing to show what I fed to the worms on what date.

This is critical – there must not be too little food. But even worse is to have too much food present since overfeeding the worms can make the bin anaerobic by adding too much moisture. It may also begin to smell. If you do accidentally add too much food, remove the material and replace it with newspaper, cardboard, etc. (but not with coffee grounds or food waste!)

To maintain the correct ratio in your bin, add two parts brown to every one part green that you add.

We want to be right in the middle, while erring on the side of giving the worms too little food as opposed to too much (if we must err). A starving worm can survive longer than you might expect. By the way, worms also eat their bedding – this means they will not starve if you accidentally miss a feeding.

How will you know if you need to add food? Gently run your fingers through the bedding and see if you find any food. If not, add 1 cup of food scraps. This will vary based on the size and construction of your housing, the worm population, what you feed them, and so forth.

Step 6: Troubleshooting Various Issues

Here are some potential issues (and solutions) you may encounter:

• Fruit flies: Add dry bedding over the food. Do not add any more food for at least one week. Used coffee grounds will also help to dry out the bin.
• Worms are crawling up the sides of the bag: This is normal. They tend to wander at times, especially if there is condensation on the sides of the bag. Re-check what food inputs were added to make sure there was nothing harmful.
• You may find other inhabitants in the bag from time to time, such as ants, spiders, etc. This is also normal.
• Foul Smells: Too much food input will ferment and cause the bag to smell. This potentially indicates overfeeding and anaerobic conditions, which will cause harm. Add more bedding.

There will be other random issues you encounter. Do research online or in various books. Vermicomposting is well-documented and there are many professional resources available.

Step 7: Reap the Rewards!

After initially starting the bin, it may take up to 5-6 months before the first worm castings become available. After that, harvesting can happen at faster intervals, usually once per month.

Here is what to do, assuming you use the bag that I recommended above:

• To start, place a bin under the bag.
• Release the buckles and velcro, then gradually loosen the locking mechanism on the interior drawstring enclosure. This will allow the worm castings to fall into the container below the bag.
• You may find that the castings will not fall freely from the bottom of the bag. You may need to poke the outside of the bag in order to loosen the castings enough to fall into the container.
• Your harvested castings should contain few to no worms.
• Stop harvesting when you reach a layer of worms. This is how you know you have reached the end of the worm castings. Pick any worms found and place them back into the bag.
• Ditto for any larger materials, such as bedding or unprocessed material. These items should also be placed back on top of the worm bag.
• OPTIONAL: Sift your casings using a 1/4 sifter and place anything that gets caught in the sifter back in the bag or your outdoor compost piles.

I’m a fan of record-keeping, so I recommend you log the dates when you harvest castings.

The end product – the worm castings – is incredibly rich in soil microbiology and nutrients. A little will go a very long way.