Kids, what kind of trash bag breaks down fastest? As you probably know, trash is a weighty (pun intended) topic in this country. With only so much landfill space available, chemists and environmentalists are looking to other means of disposing trash. Most of the plastic bags in landfills are not environmentally friendly because they take many years to completely degrade.

 
In this experiment the biodegradability of several plastic bags, brown paper bags, and newspaper are tested in different environmental conditions: direct sunlight, a mulch pile (to simulate an ‘active’ landfill), a leaf pile (to simulate a dry landfill), in tap water (to simulate a lake), and in saltwater (to simulate an ocean). You’ll have to plan ahead because results take at least three months.  Also get an okay from your parent or guardian before starting. Trust me, adults will not be amused to come home and find that you've begun this without their knowledge. Besides you may need their help.

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

Materials:

• Ten plastic trash bags marketed as biodegradable.  Use five each of two different brands as follows.  NOTE!  If the bags contain polyethylene plastic they are not biodegradable, but rather a plastic mixed with a chemical additive that breaks the plastic molecular structure and disintegrates. This is not considered to be overall an eco-friendly process. Eco-friendly vendor certifications should be ASTM D6400 and/or DIN EN13432. If the price of the biodegradable plastic bag is close to that of plastic bags, then they probably have the additive (they may say “oxo” or “oxy” in the name). 
• 5 nonbiodegradable plastic bags
• 3 nets (plastic or cotton)
• wire or string
• 6 wooden posts
• 5 brown paper bags
• 5 pages of newspaper
• a mulch pile 4 feet (120 cm) high consisting of grass, leaves, rotting vegetables, fertilizer, and compost starter culture in a 3-foot (1 meter) diameter ring made of wire fencing
• tap water
• a leaf pile 3 feet (1 m) high
• 10 plastic containers (½ gallon (2 liters) each)
• saltwater (15% by volume)

Procedure:

1. Fold and secure the plastic bags on top of a net with wire or string and identify them. Tie a wooden post at each end of the net and place each post into the ground, leaving the plastic bags exposed to the sun. Do the same with one paper bag and a page of newspaper.
2. Repeat step 1 by placing the same types of bags in the middle of a mulch pile. Wet the pile thoroughly with water.
3. Repeat step 1 by placing the bags in the middle of the leaf pile.
4. Place the bags into five separate containers of tap water and saltwater.
5. Record the changes that occur upon removal after at least 3 months; photos are useful.

Results:

1. Did any of the materials decompose? If so, which decomposed most thoroughly?
2. Was the rate of degradation greatest in the sunlight, mulch pile, leaf pile, tap water, or saltwater environments?
3. Did the plastic bags that were advertised as biodegradable appear any different from the nonbiodegradable bags?

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
February 2012

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Resources & References: 

http://www.infoplease.com/cig/science-fair-projects/kind-trash-bag-breaks-down-fastest.html
Excerpted from The Complete Idiot's Guide to Science Fair Projects © 2003 by Nancy K. O'Leary and Susan Shelly. Alpha Books, Penguin Group (USA) Inc.

http://www.biodegradableplasticbags.org/

http://www.education.com/science-fair/article/biodegrade-plastic-paper-newspaper/