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Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat?

308 reviews


Areas of Science
Time Required
Long (2-4 weeks)
Material Availability
Composting worms will need to be ordered online or bought in a local gardening store. A worm farm can be constructed or purchased.
Average ($50 - $100)
No issues
Sabine De Brabandere, PhD, Science Buddies
Kristin Strong, Science Buddies Alumni

This project is based on a DragonflyTV episode.

*Note: For this science project you will need to develop your own experimental procedure. Use the information in the summary tab as a starting place. If you would like to discuss your ideas or need help troubleshooting, use the Ask An Expert forum. Our Experts won't do the work for you, but they will make suggestions and offer guidance if you come to them with specific questions.

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What happens to the food leftovers in your home? Do they go in the trash? Down the garbage disposal? Or get gobbled up by the family dog? Food leftovers are a type of organic waste, a waste that comes from a plant or animal. Organic waste—like table scraps, agricultural waste, and human and animal waste—is biodegradable. This means, it can be chemically broken down by bacteria, fungi, or other living organisms into very small parts.

Photo of decaying fruits and vegetables
Figure 1. This photo shows examples of organic waste. (City of Davis, California; 2010.)

Although organic waste is biodegradable, it can cause environmental problems if it is dumped on a landfill. If it decomposes in the absence of air, it produces biogas (mostly methane), which, when released in the atmosphere, contributes to the greenhouse effect. It can also lead to groundwater pollution. Despite the difficulties in its disposal, organic waste is a highly valuable resource. It is energy-rich and full of nutrients. When processed properly, it can greatly enrich soils or run biogas generators to produce electricity.

In this environmental science project, you will explore how composting worms, called red wigglers or Eisenia fetida, can be used to break down organic waste, like food leftovers.

Photo of a red wiggler, a type of worm
Figure 2. This photo shows a red wiggler, a special type of worm used in composting. (Wikipedia Commons, 2006.)

With your background research as a guide, you will build worm farms, and then test how much organic waste your worms can process, and how fast they can do it. The amount of organic waste can be quantified by its mass. The time will be measured as the number of days it takes for the food to disappear. The rate can then be calculated by dividing the amount of organic waste by the time it took for the food to disappear (like 500 grams [g] in 10 days.).

Several variables influence the rate at which red worms compost organic matter, like the number and health condition of the worms in the farm, the type and amount of organic waste fed, the bedding used for the worms in the farm, the temperature in the farm, the acidity (pH) of the material in the farm, etcetera. You will choose one variable to study and do your best to keep all others constant.

Making several farms will give you a better grip on variables like the number of worms in the farm and their health, the acidity or composition of the material in the farm, etcetera. Having several farms can also drastically reduce the time over which you do your experiments. Science project Feeding Earthworms: Do Different Diets Affect Them and the Soil They Enrich? can teach you how to create inexpensive, identical worm farms.

Some examples of studies you can do with your farms are listed in Table 1. These all assume you create four identical farms, numbering them 1–4 for easy reference.

Variable You Will Change How You Can Set up the Test Measurement Options
Number of worms in the farm
  • Host 0, 20, 40, and 60 worms in farm 1, 2, 3, and 4.
  • Feed the worms in the farms an identical type and amount of organic food.
  • Place the farms in identical environments.
Time it takes for the food to disappear in farms 1, 2, 3, and 4.
Amount of organic food consumed
  • Host equal numbers of worms in the farms.
  • Feed the farms different amounts of identical organic food, like 200 g, 400 g, 600 g, and 800 g of cut-up melon rinds.
  • Place the farms in identical environments.
Time it takes for the food to disappear.
Type of organic food consumed
  • Host equal numbers of worms in the farms.
  • Feed the worms in the farms the same amount of different types of organic food, like 200 g of cut-up fruit leftovers, 200 g of coffee grinds, 200 g of cooked rice, and 200 g of dead leaves.
  • Place the farms in identical environments.
Time it takes for the food to disappear in farms 1, 2, 3, and 4.

Temperature in the farm.

Composition of the compost produced.
Temperature in the farms.

Do not forget to measure the ambient temperature in the farms, as this can be different from the ambient temperature of the farms' surroundings.
  • Equal number of worms, fed the same type and amount of organic waste.
  • Place the bins in different locations, like a shaded spot outside, the attic, the basement etcetera. You can also insulate a farm by adding cardboard or other insulating material around it. Check the temperature in the farm regularly and make sure it does not drop below 4° Celsius (40° Fahrenheit) or rise above 30° Celsius (85° Fahrenheit).
Time it takes for the food to disappear in farms 1, 2, 3, and 4.

Health of worm population in farms 1, 2, 3, and 4.
Table 1. Table of studies you can perform on worm farms. It lists the variable you will change, how you will set up the study so you can keep other parameters constant, and what you will measure.

You will need to perform at least three repetitions of the same test to produce reliable conclusions. You can average your measurements over the three tests. You can then create a bar chart, graphing the variable you changed on the x-axis (horizontal axis), and the number of days it took for each sample to decompose on the y-axis (vertical axis). You can also graph the rate on the y-axis.

If you are interested in how the worm compost or worm urine impacts plants, you can collect and measure "worm urine" from the bottom of your worm farm, or collect worm castings from the top. Worm castings are a mass of soil, mud, or sand that is thrown up by the worm, on the surface, after passing through the worm's body. The Science Buddies project Earthworm Castings — The Ideal Proportion in Soil for Young Garden Plants can provide ideas on how to do the study.


In this video, you can learn how to build and test a worm farm:

Update second bullet to https://practicalaction.org/knowledge-centre/resources/recycling-of-organic-waste/ Update third bullet to https://www.lsuagcenter.com/portals/communications/publications/publications_catalog/lawn%20and%20garden/backyard%20composting/worm-composting-bin

This source describes ways in which different countries handle organic waste:

This source provides information about making your own worm farm:

  • Carney, W. (2010, March 1). Worm Composting Bin.LSU College of Agriculture. Retrieved July 18, 2018.
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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

De Brabandere, Sabine, and Kristin Strong. "Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat?" Science Buddies, 17 May 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p055/environmental-science/how-much-organic-waste-can-composting-worms-eat. Accessed 27 Sep. 2023.

APA Style

De Brabandere, S., & Strong, K. (2023, May 17). Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat? Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/EnvSci_p055/environmental-science/how-much-organic-waste-can-composting-worms-eat

Last edit date: 2023-05-17
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