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Recommended grade level: 3 – 5
Presentation time: 50 minutes
Composting with worms introduces students to the rapid process of decomposition that occurs in a confined area. During this presentation, students can see how their leftover cafeteria food can become fertilizer for their classroom plants or outside garden. Through a presentation and hands-on digging in a vermicomposting bin, students are exposed to the tiny creatures that are a terrific basis for science experiments.
- Vermicomposting bin
- Sample of dried castings
- Pie trays, plastic utensils and magnifying glasses (kids can share)
Questions for students:
- What is decomposition and why is it important?
- What is composting? Briefly describe composting and the action of decomposers.
- What are some examples of decomposers?
- How might composting be useful?
What is Vermicomposting?
Composting with worms; organic material breaks down in the same way as in composting but the environment is controlled and the type of organisms are limited. The humus contains a greater proportion of worm castings than ordinary compost. Castings have the same mineral rich properties as compost, however, vermicomposting produces a more uniform, fine-grained and darker product. The amount of time that it takes to turn food and bedding into castings depends on the number of worms; 6-8 weeks is a good estimate.
Components of Successful Vermicomposting
- Physical Structure (Bin) – must be dark, closed but allow aeration
- Biological Organisms – worms or other organisms that appear
- Controlled Environment – moderate temperature, humid and moist. A good way to tell if the temperature is okay is that it would probably be comfortable for you and maybe a little cool (between 59-77 degrees).
- Amount of Worms – the size of your bin is determined by the amount of food waste you want to vermicompost. Worms can eat one half their body weight each day. For example: The Smith family weighed all of their suitable food scraps for a week. The total was 7 lbs. Their worm bin should contain 2 lbs. of worms. Worms require about 3 sq. ft. for each 1 – 1 and 1/2 lbs. of worms. The Smith’s worm bin should have an area of 6 sq. ft.
- Bedding Requirements – newspaper, paper, leaves, or peat-moss are some examples. A handful of soil will act as grit in worms’ gizzards. The most important ingredient is water. A worm bin that is too wet or too dry can slow decomposition and even kill your worms. The squeeze test is a good way to check the moisture level in your bin. The amount of water you will need to use varies with the type of bedding material you choose. If you choose newspaper the ratio by weight is 1:3; one part newspaper to three parts water.
- Feeding – Food scraps except anything that has fats and oils. No dairy products or meat should be placed in the worm bin. Worms do not seem to care for grapefruit rinds (who would?). Compost them in an outdoor heap. Rotate the location for burying food in your bin. Make sure that you cover the scraps completely so that the bin does not become infested with flies.
- Maintenance/Harvesting – Worm bins require very little maintenance. Check the moisture level by doing the squeeze test. Worms can live for months without being fed because they will eat the bedding and their own castings. These castings are then called vermicastings. They are more uniform in appearance and are more concentrated than vermicompost. For the best results, they should be mixed with potting soil and perlite or other materials before adding to plants.
*Fruit flies are sometimes a problem. Make sure that you bury food completely. If flies appear do not feed or open the bin for two (2) weeks. In the winter it may be possible to freeze the flies out by leaving the bin open outside in cold for about 15 minutes to kill fly eggs. Be careful; remember that your worms can freeze, too!
Large scale and commercial vermicomposting works the same way!