Bury Your Trash Experiment

Waste management engineers use the process of biodegredation to minimize the amount of space that landfills take up. Civil and agricultural engineers take advantage of the biodegradation process in designing waste and water treatment facilities, and making soil improvements to improve crop production.

After this activity, students should be able to:

• Explain what the term "biodegrade" means, and generally describe how the process works with respect to the various items of buried trash.
• List what objects do and do not biodegrade (roughly) by explaining the difference between organic and inorganic materials.
• Explain how engineers apply what they know to facilitate waste management.

What items decompose when buried?CopyrightCopyright 2012 Denise W. Carlson, ITL Program, College of Engineering, University of Colorado Boulder

Now that we have talked about what biodegradation is and everyone has collected some trash from lunch, let's go outside. Bring with you what you saved from lunch.

In this patch of land, we will bury individual pieces of trash in a grid pattern. That way, when we dig it up in three months, we can learn what happened to each type of material. Let's use multiplication to figure out how many spots on the grid are available to bury the individual items.

Now, I want everyone to get together to decide which pieces we will bury. Remember, we want to put as many different materials under the soil, so we can determine which materials biodegrade and which ones do not. Try to avoid burying the same type of garbage twice.

Before the Activity

• Identify a small area of earthy ground that is located away from foot traffic and obtain permission to be able to dig up and use the area for the next three months.
• Using a sturdy shovel, dig in the soil to turn it over and mix in any grass or plants). Attempt to create a square of churned-up soil approximately 6 inches deep. Use the string to create a grid over the soil with 1 ft x 1 ft squares, by cutting 8 lengths of 5-ft-long string, laying 4 horizontally and equally spaced, and laying 4 vertically in the same manner.

With the Students

Students document the items they bury.CopyrightCopyright 2012 Denise W. Carlson, ITL Program, College of Engineering, University of Colorado Boulder

1. Instruct students to each save a piece of trash or two from his/her lunch, including sandwich crusts, apple cores, etc. Essentially, tell them they to save whatever is leftover once they have eaten everything they wanted.
2. After lunch and in the classroom, give students gloves and have them sort their various pieces of trash into one long row of items, putting like items together. For example, put paper wrappers, foil wrappers, Styrofoam, cardboard each in their own piles.
3. On a poster board, draw a table with three columns and these row headers: type of garbage, prediction, result. Record the type of each trash pile its own row. Ask students as a group to predict, for each trash type, whether or not they think that material type will biodegrade over the next three months. Record their predictions.
4. Lead the class outside to the prepared soil area. Have students bring pieces of trash they would like to bury. Bring as many different types of trash as possible. As each student buries his or her piece of trash, ask one student draw a grid diagram on another poster board and record where each item is buried in the plot.
5. Two to three months later, or longer if the experiment is performed during the winter months, bring the poster boards, shovel and gloves and go outside with the class and dig up the plot. As each plot is dug up, try to identify what is uncovered. Have the students use descriptive words to explain what the piece of trash now looks like, how it changed, and record the results for each piece of trash.
6. Conclude with a class discussion, asking students the Investigating Questions.

Quiz: Ask students some questions to gauge their comprehension of the subject matter. Have students individually write their answers on paper to be handed in for grading.

• Write out the definition of the term "biodegradable."
• Describe a dump.
• Describe a compost pile.
• Describe what happens to your household garbage after it is "thrown away."
• List the types of materials that are biodegradable and those that are not.
• (Show students a number of new items of trash.) Identify each item as either biodegradable or not biodegradable.

• Handling garbage is unsanitary so make sure that the children wear gloves and wash their hands after they move their trash from the cafeteria to the mock landfill.
• Remind students to be careful when handling the small shovels. If they do not know already, instruct them in the correct way to dig up small amounts of soil at a time.

It helps to dig up the soil in the grid area before the children dig their own holes. Locating the test plot in a garden area may make moving the soil easier.

Bury as many different types of trash (different materials) as possible, including a lot of organic items that will readily decompose.

Doing this experiment in the warmer months helps the organic objects decay much faster, and reduces the three-month waiting period a good deal.

An example backyard compost pile.CopyrightCopyright 2012 Denise W. Carlson, ITL Program, College of Engineering, University of Colorado Boulder

Create a class compost pile, beginning with the dug-up trash remnants that were found to be biodegradable. This reinforces the concepts covered and provides another hands-on experience.

Bagchi, Amalendu. Design of landfills and integrated solid waste management, University of Wisconsin Press. 2004.

57 Ways - 31. Create a Compost Pile. 1995. University of Illinois Extension. Accessed 4/27/07. http://www.thisland.uiuc.edu/57ways/57ways_31.html

Compost. Modified April 23, 2007. Wikipedia. Accessed 4/27/07. http://en.wikipedia.org/wiki/Compost

Organic Material. Modified April 16, 2007. Wikipedia. Accessed 4/27/07. http://en.wikipedia.org/wiki/Organic_material

Biodegradable. Modified April 23, 2007. Wikipedia. Accessed 4/27/07. http://en.wikipedia.org/wiki/Biodegradable