Abstract

Objective

In this experiment you will test how biodegradable different materials are.

Introduction

Every year each household contributes waste products by using and consuming disposable products and materials. Sometimes these things are recycled, like many paper, plastic and glass products. Other times the items are re-used, like old tires that are chipped and used to build playground surfacing materials. Some people even save kitchen scraps to add to a compost pile in their yard.

Everything else ends up in a landfill, the place where the garbage man takes all of your trash. Landfills are huge piles of trash that are often buried to help the waste products break down, or decompose. Products that decompose rapidly are called "biodegradable materials." These products are good for the environment because they will break down in the landfill and will not leach harmful chemicals into the soil.

How do you know which products are biodegradable? Sometimes products that are biodegradable will say so on the package. This way a consumer can make an informed choice about which types of products to buy. In this experiment, you can conduct your own survey of selected materials to investigate if they are biodegradable or not in the soil. Which types of products are biodegradable? How does this effect your choice as a consumer?

Terms, Concepts, and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• landfill
• biodegradable
• biomass
• composting
• recycling

Bibliography

Here are some helpful web sites from the Energy Information Administration Kid's Page that discuss the use of plastics (recycling and new degradable plastic materials), landfills and biomass:

• MacIntyre, Stacy and Altman, Paula. 2005. "Conserving Energy: Recycling Plastics." Washington, D.C.: EIA Kid's Page, Energy Information Administration. [3/2/2006]
  http://www.eia.doe.gov/kids/energyfacts/saving/recycling/solidwaste/plastics.html
• MacIntyre, Stacy and Altman, Paula. 2005. "Energy & Waste: Landfilling." Washington, D.C.: EIA Kid's Page, Energy Information Administration. [3/2/2006]
  http://www.eia.doe.gov/kids/energyfacts/saving/recycling/solidwaste/plastics.html
• MacIntyre, Stacy and Altman, Paula. 2005. "Biomass: Renewable Energy from Plants and Animals." Washington, D.C.: EIA Kid's Page, Energy Information Administration. [3/2/2006]
  http://www.eia.doe.gov/kids/energyfacts/sources/renewable/biomass.html

Materials and Equipment

• shovel
• backyard or other place to bury items
• soil
• popsicle sticks
• permanent marker
• different products and materials to test:
  • diapers: cloth, Huggies, Pampers, Luv's...
  • plates and cups: paper, wax coated paper, Styrofoam, plastic...
  • paper: notebook paper, gift wrap, magazine paper, construction paper, cardboard...
  • wood: redwood, pine, bamboo, fir...
  • bags: paper bags, plastic grocery bags, garbage bags, sandwich baggies...
  • any other consumer product made by different brands or materials!

Experimental Procedure

1. First decide which types of materials you are going to test. You can use any type of disposable item that is made by different brands or with different materials. You should pick something that will have at least five different samples. For this example, I am going to use different types of disposable cups.
2. Label one popsicle stick for each item using permanent marker.
3. Find a spot to bury your items that is out of the way of traffic, like near a fence, the corner of the yard, or in the garden.
4. Get your parents permission to dig a hole there. If they say it is okay, then dig a small trench large enough to fit all of your items in a row. For example, if I am burying 5 cups, I would dig a hole about 1 foot deep, 1 foot wide and 2 feet long.
5. Line the five items in a row in the trench.
6. Bury each item, placing the matching labeled popsicle stick in the dirt to mark each item.
7. Leave the items buried for at least 3 weeks, preferably 6 weeks or more. This is the most difficult aspect of the experiment because you need to plan ahead!
8. While you are waiting, you will need to develop some kind of a way to measure how much an item has decomposed in the ground. To do this you can develop a scale to help you assign number values to your data. For example, one type of scale might rate the materials from 1 to 10 depending upon how much material was left:

   1	2	3	4	5	6	7	8	9	10
   No degradation, all material still there	Material is soft but whole	Few holes	Some holes	More holes	About half of the material is gone	Many holes	Large tears, material is falling apart	Scraps of material left	Fully degraded, no material present

9. When time is up (you will want to keep track of the time buried using a calendar), go out with your shovel to dig up your items one at a time. As you dig up each item, rate the item according to the scale you developed. Record your data in a data table:

   Number	Item Description	Rating
   1
   2
   3
   4
   5

10. When you are finished you will want to make a graph of your data. Make a bar graph by writing your scale on the left side (Y-axis) and drawing a bar for each type of material. Remember to label and color code the bars of your graph.
11. Which materials degraded the most? The least? Which materials will break down best in a landfill? Which materials do you think we should buy?

Variations

• In addition to being biodegradable, many materials are compostable. Kitchen waste, paper products, and wood products are examples of things that can be used in a compost pile to make fertile, nutrient rich soil. Do an experiment composting different materials. Compare and contrast different methods of composting: open vs. closed, covered or uncovered, with or without turning, with or without watering. You can also experiment with vermiculture, or worm composting.
• Much of the trash that ends up in a landfill falls into distinct categories. Conduct a survey of a landfill and what types of things are dumped there. You can sometimes find these statistics online from your city or county landfill. Make graphs to show the frequency and distribution of different landfill materials. Which things are the most common items in a landfill? Are there any common problem materials, like tires?

• For more science project ideas in this area of science, see Environmental Science Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Last edit date: 2006-04-20 00:46:02