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

Difficulty
Time Required Long (2-4 weeks)
Prerequisites None
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.
Cost Average ($50 - $100)
Safety No issues
*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.

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.

Environmental Science science  project <B>Figure 1.</B> This photo shows examples of organic waste. (City of Davis, California; 2010.)
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.

Enviromental Science science project <B>Figure 2.</B> This photo shows a red wiggler, a special type of worm used in composting. (Wikipedia Commons, 2006.)
Figure 2. This photo shows a red wiggler, a special type of worm used in composting. (Wikipedia Commons, 2006.)

Watch DragonflyTV wormfarm video
Click the image to watch this DragonflyTV episode as Kevin uses food leftovers to build a worm farm. This video was produced by DragonflyTV and is presented by pbskidsgo.org.
Click the image to watch this DragonflyTV episode as Kevin uses food leftovers to build a worm farm. This video was produced by DragonflyTV and is presented by pbskidsgo.org. http://pbskids.org/dragonflytv/show/wormfarm.html

With your background research and the DragonflyTV video 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.

Credits

Sabine De Brabandere, PhD, Science Buddies
Kristin Strong, Science Buddies Alumni

This science project was inspired by the following DragonflyTV Episode:

Cite This Page

MLA Style

De Brabandere, Sabine, and Kristin Strong. "Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat?" Science Buddies. Science Buddies, 6 Nov. 2015. Web. 12 Feb. 2016 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/EnvSci_p055.shtml?from=Blog>

APA Style

De Brabandere, S., & Strong, K. (2015, November 6). Get Rid of Those Leftovers: How Much Organic Waste Can Composting Worms Eat?. Retrieved February 12, 2016 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/EnvSci_p055.shtml?from=Blog

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Last edit date: 2015-11-06

Bibliography

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

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

This source provides information about making your own worm farm:

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