Vermicomposting: A Starter’s Guide for Teachers
Recycle Your Food Waste With Worms
As a society, we look for ways to reduce, reuse, and recycle as much as we can. We can reduce the amount of products we buy to only what we will use. We can reuse an empty coffee can or donate the computer we are no longer using. Recycling can be done through home recycling services or at drop-off recycling centers.
Another way you can recycle is instead of throwing away food it can be recycled by a process called composting. An efficient and fun way to compost food is with worms. This process is known as vermicomposting. Vermicomposting is the process of worms eating food scraps. The worms used in vermicomposting break down food and, thanks in part to their digestive systems, create an enriching source of nutrients called castings. Castings are a fancy way for saying worm poop. Whether you call it compost, castings or worm poop it’s full of microbes and nutrients that can be used as a beneficial additive to your garden or potted plants.
A vermicompost bin is a small ecosystem that you can keep in your classroom and it only requires a few supplies to get started. To get started, you will need a worm bin, bedding, food and red worms. The worm bin can be used for observing, describing, asking questions, measuring and recording, life cycle studies and even writing exercises. Before starting, you will need to consider what worms need to survive. Like all animals, worms need food, water, shelter and space to survive.
For the purpose of this guide, we will start out by using inexpensive materials. The guide will cover the following:
- Resources and Activities
An inexpensive and easy to use bin for vermicomposting is a plastic storage container. The container should be dark in color and shallow. Red worms are top feeders and prefer to live/feed near the surface, so a container should be 18” high or less. A 3-gallon to 12-gallon plastic Rubbermaid storage container will be adequate.
Vermicomposting is an aerobic activity, meaning it needs oxygen. For air circulation, you can use a ¼ to ½-inch drill bit to add holes in the top or side of the container. If the lid is loose fitting and not airtight there is no need to drill holes in the container.
Red worms survive best if the temperature is kept between 55° - 77° Fahrenheit. Keep your worm bin away from vents and do not place on window sills as the temperature can fluctuate in these two areas.
- Once you become comfortable with vermicomposting, you can investigate larger worm bins.
- There are specially designed bins for vermicomposting you can find online, or
- You can build your own worm bin. Instructions are available if you are interested in building your own bin.
Bedding for your worm bin will serve several purposes. It will serve as a food source for your worms, a good medium in which to bury the food scraps and it will keep your worms comfortable and feeling safe. Using newspaper as bedding for your worm bin is inexpensive, readily available and simple to use. To use newspaper:
- Shred newspaper into one-inch strips or use a paper shredder for strips or crosscut paper.
- Soak the strips of newspaper in water for 24 hours. Add enough water so that the strips of newspaper are submerged.
- Wring out the strips of soaked newspaper so it feels like a wet sponge. Water should not be dripping from the newspaper.
- Fluff the paper so that worms can easily move throughout the paper.
- Fill the bin two-thirds full with fluffed paper.
- Add a small handful of soil or sand to the bedding (more on this under food.)
- Avoid using glossy paper or newspaper inserts.
- You only need to add bedding when you first set up the bin and after harvesting the castings.
- You can use other materials such as peat moss or coconut fiber as bedding too. Due to high acidity levels or salt levels, these items need additional attention and may need longer soak times in water than newspaper.
There are over 4,000 different species of worms. Worms may look similar but each species needs different requirements for survival. Worms that survive best in a compost bin are Eisenia fetida, also known as “red worms,” “red wigglers,” and even “manure worms.” Worms can be purchased from local growers, bait stores, pet stores or online.
Red worms can eat half their body weight in a day. If you start with a larger bin (12-gallon), you could add up to one pound of worms, which is about 1,000 worms. Or you can start out with a few hundred and they will populate the bin naturally. In four months your worm population has the potential to triple in size. The worms in your bin, also known as a worm herd, will stabilize at levels that can be supported by the food given to them and the size of the bin.
Worms are not picky eaters and will eat a variety of food scraps. Worms do not have any teeth but they do have a gizzard to aid them in food digestion. A gizzard for a worm is like a garbage disposal in a sink. Inside the gizzard are powerful muscles and small mineral particles, like soil or sand. Food enters the gizzard and then the muscles and small mineral particles pulverize food making the food small enough to pass into the worms’ intestines.
When first starting a bin keep the food choices simple. As you get familiar with vermicomposting, you can start adding a variety of foods.
Foods to add can include:
- Fruit and vegetable trimmings. (Some foods take longer to break down because they are fibrous, such as broccoli, carrots and potato peels.)
- Bread (should not have anything on it, like peanut butter, mayonnaise, butter, etc.)
- Coffee grounds and filters
- Tea leaves and tea bags
- Egg shells (washed and ground up)
Foods to avoid include:
- Oily foods
Give the worms a few days to acclimate to their new bin before you begin feeding them. When starting a new bin add a small amount of food and check on the worms every few days. You will see how quickly they are eating and adjust the food amounts visually. If you add one pound of worms to your bin, they will eat approximately 1/2 pound of food each day. Whether you add one pound of worms or just a handful to your new bin the worm to food scraps ratio is 2:1.
When your bin looks like soil and there are no more pieces of shredded paper, it is time to harvest or remove the compost from the bin. To harvest the compost you have several options:
- Migrating Method: Open your bin and gently push the compost over to one side. In the other half add new bedding and some tasty food scraps. Once the worms have migrated to the new bedding, you can remove the compost (pick out any stragglers) and add more bedding to the now empty side of the bin.
- Cone Method: This is a fun method to use with students. Lay a piece of plastic down on a table. Gently remove the compost and place into cone shaped piles on the table. Each cone shaped pile should be approximately six inches in diameter. Give the worms about ten minutes to burrow down and move away from the light. Next, take a small handful of the compost from the top of each cone and place in a separate container. Give the worms another ten minutes to burrow down again and you can repeat the process until all you have left is worms. Return the worms to the bin where you have added new bedding.
- Scoop Method: Remove the lid to your bin and give the worms about ten minutes to burrow down deeper into the compost. You can then scoop the top layer of compost out of the bin. Repeat process until all that is left is the worms and add new bedding.
- Worm compost is an excellent soil amendment or fertilizer you can add to plants, flowers and gardens.
- If adding compost to a potted plant use 1/4 compost to 3/4 potting soil. If you use too much compost, it can make the soil hard and leave plants unable to grow properly.
- You will need to harvest every 3-6 months.
Having a successful worm bin is a trial and error activity. There are a variety of bins, bedding and food that can all be used to make a successful worm bin. Some common issues with worm bins are:
- Cause: Too much food.
- Solution: Feed worms less.
- Bin too dry:
- Cause: Not enough moisture.
- Solution: Add a piece of food with high water content, such as an apple core, watermelon, or berries. You could also add newspaper that you’ve soaked and wrung out excess water.
- Bin too wet:
- Cause: Did not wring newspaper out enough.
- Solution: Add strips of dry newspaper.
- Cause: High content of water in food.
- Solution: Add less high water content foods.
- Fruit Flies:
- Cause: Food.
- Solution: Burry food under bedding.
For questions or concerns, you may have about your worm bin email IDEM at email@example.com.
Resources and Activities
- Indiana's Environment and You
- IDEM Lesson Plan, page 19
- IDEM Vermicomposting Fact Sheet
- Part of the IDEM Green Steps educational materials.
- The Worm Guide: A Vermicomposting Guide for Teachers
- California Integrated Waste Management Board
- Worm Composting Bin
- Missouri Department of Natural Resources