Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat?
Summary
This project is based on a DragonflyTV episode.
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Abstract
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.
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.
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 |
|
Time it takes for the food to disappear in farms 1, 2, 3, and 4. |
| Amount of organic food consumed |
|
Time it takes for the food to disappear. |
| Type of organic food consumed |
|
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. |
|
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. |
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.
Bibliography
In this video, you can learn how to build and test a worm farm:
- Twin Cities Public Television, Inc. (2006). Worm Farm by Kevin. DragonflyTV, Twin Cities Public Television. Retrieved May 25, 2010.
This source describes ways in which different countries handle organic waste:
- Practical Action. (n.d.). Recycling Organic Waste. Retrieved May 27, 2010.
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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