Landfill Decomposition
Introduction
As more and more people populate the planet, the amount of trash we create dramatically
increases. How should this trash be disposed of? Should all garbage be treated in the same
manner? In this activity, simulated landfills will be set up and the effectiveness of each will
be tested using various test items.
Background
Each year, Americans generate nearly 210 million tons of trash. That equates to an
average of four pounds of trash per person per day! Where exactly does all of this garbage
go and what happens to all of this trash?
Some of the trash is recycled or incinerated, however, the majority of the trash is
placed into landfills. A landfill is a structure that is built on top of or into the ground that
helps isolate trash. There are two basic types of landfills: open-air landfills and sanitary
landfills. Open-air landfills, more commonly known as dumps, are nothing more than an
open hole in the ground where trash is placed and sometimes covered with a layer of soil.
Most of the waste in open-air dumps is left in piles that are open to rain, wind and
scavenging animals. Open-air dumps are the most predominant method of waste disposal
worldwide. However, in the United States, most open-air landfills have been eliminated
and replaced by sanitary landfills.
Sanitary landfills utilize clay or plastic liners to separate and isolate trash from the
surrounding environment. Most sanitary landfills cover their trash with compacted soil
daily. This helps cut down on the overall smell of the trash, the amount of litter, and the
amount of pests. When a section of a sanitary landfill is completely full, a plastic cap or
liner is placed on the landfill. This liner is then covered with another thick layer of soil.
Although sanitary landfills have solved some of the problems associated with open-air
landfills, many materials in sanitary landfills are not biodegradable. Non-biodegradable
objects, such as most plastics and synthetic materials, do not decay. Biodegradable
materials such as food wastes and paper also do not decompose rapidly. Once the trash in
sanitary landfills is covered with compacted soil and capped with a plastic liner, very little
water and oxygen are present. Both oxygen and water are required for most organisms
that aid in decomposition.
The most common decomposers in nature are bacteria, molds, fungi and yeast.
Decomposers release enzymes that digest and break down materials into simpler
compounds. The decomposers absorb the digested materials and recycle the material back
in to the environment in useful forms. Certain decomposers, known as anaerobic
decomposers, thrive in environments that are void of oxygen. The small amount of
decomposition that does occur in sanitary landfills is anaerobic. The major byproduct of
anaerobic decomposition is landfill gas. Landfill gas is basically a 50:5 0 mixture of
methane and carbon dioxide gas. This is a very flammable and explosive gas that must be
removed from landfills. To accomplish this, a series of pipes are embedded in sanitary
landfills that collect the gas. The gas is lead through the pipes to the surface on the landfill
where the gas is usually burned.
The ability of an item to decompose depends on factors such as the chemical make
up of the material and the type of environment the material is placed in. In this activity,
various items will be placed into three simulated landfill situations. The items will then be
observed over an extended time period to see if any decomposition occurs
Materials
3 metal strips
3 paper strips
3 wood pieces
Organic Soil Mixture
16 marker sticks (popsicle
3 Cornstarch peanuts
3 pieces of processed food
3 Styrofoam peanuts
Sand
sticks)
3 pieces of synthetic string
3 pieces of cotton string
Plastic bag
3 Landfill containers
Sharpie
Procedure
Initial Setup (Day 1)
1. Obtain 3 landfill containers. Using a marker, write your group’s initials on the
bottom of each container.
2. Place organic soil into two of the landfill containers. Fill the containers three
quarters of the way full with organic soil.
3. Place the sand into the other landfill container. Fill the container three quarters of
the way full with the sand.
4. Place one of each of the objects into the small plastic bag.
5. Place the bag 1” below the soil in one of the organic soil landfill containers. This will
represent sanitary landfill conditions.
6. Label the container “Sanitary”.
7. Place one of each of the items into the other organic soil containers. Place the
objects roughly 1” under the surface of the soil. Label a marker stick for each item
and place the marker near the object in the soil.
8. This landfill represents an organic open-air landfill.
9. Place one of each of the items into the sandy soil container. Label a marker stick for
each item and place the marker near the object in the soil. Place the objects roughly
1” under the surface of the sand.
10. This landfill will represent a sandy soil open-air landfill.
11. Place water into all three of the landfill containers until the soils are moist but not
thoroughly soaked.
12. Place containers on windowsill.
13. Go to the predictions section and complete the prediction questions.
Every few days (maintenance)
14. Add water to the trays every few days as needed to maintain moist soil.
Once per week for 6-8 weeks (observations)
15. Dig up and observe the appearance of the materials in each type of landfill situation
once a week over the next six or eight weeks. Record the observations using the
following symbols in Data Table #1 of the Landfill Decomposition Worksheet. Place
the items back in the soil after observations have been recorded.
No degradation
+ Beginning stages of degradation
+++ Large amount of degradation
-
After last observation
16. Answer the questions in the Landfill Decomposition Worksheet after the experiment
has been completed.
*Lab modified from Landfill Decomposition lab by Flinn Scientific.
Name___________________________________ Date
Period__________
Predictions
1. A. You are modeling 3 different types of landfills (Sanitary, Open Air Organic soil,
Open Air Sand). List the 3 types of landfills in the order where you expect to see the
most amount of decomposition to the least amount of decomposition.
B. Do you expect at least some decomposition in all of the landfills”. Explain.
2. A. Within each of the “landifils” you have placed 8 items (Cornstarch peanut paper,
cotton string, Styrofoam peanut, foodstuff, synthetic string, metal and wood). List
these 8 items in order from the most decomposition to the least decomposition.
B. Do you expect any of the items to completely decompose over the 6-8 week time
frame? Explain.
C. Do you expect any of these items to show no decomposition over the 6-8 week
time frame? Why or Why not?
D. Ifyou answered yes to C, if this experiment was carried out longer do you think
that you would eventually see decomposition? Explain.
____
____
____
____
____
___
Name:
Landfill Decomposition Worksheet
Week
1
2
3
4
5
6
7
8
cornstarch peanut
paper
cotton string
Styrofoam peanut
c.
foodstuff
synthetic string
metal
wood
cornstarch peanut
paper
cotton string
c
Styrofoam peanut
foodstuff
synthetic string
metal
wood
—3—
© 2002 Flinn Scientific. Inc. All Rights Reserved.
1N10476
Reproduction permission is granted only to
science
Inc. No part of this material may be reproduced
or transmitted in any form or by any means. electronicteachers who have purchased Landfill Decomposition. Catalog No. FB0425, from Flints Scientific,
retrieval synem, without pecusiasion in writing from
or mechanical, including, but not limited to photocopy.
Flints Scientific, Inc.
tecording, or any information storage and
___________
______
Name:
Landfill Decomposition Worksheet, Continued
Week
1
2
3
4
5
6
7
8
cornstarch peanut
paper
cotton string
Styrofoam peanut
c
foodstuff
synthetic string
metal
wood
—4—
1N10476
2002 Flinn Scientific, Inc. All Rights Reserved. Reproduction permission is granted only to science teachers who have purchased Landflfl
Decomposition, Cataloa No P130425, from Flian Scientific,
In,. “,opot f tins toateew may be reproduced or transmitted in any torm or by any means, electronic or mechanscal, including.
but not hunted to photocopy recording, or any information storage and
retrieval system, withont permission in writing from Fliun Scientific, Inc.
_____________________________
Name:
Post-Lab Questions
1.
Describe what happened to the materials in the organic soil. What materials were biodegradabl
e in the organic soil?
2.
Describe what happened to the materials in the sand. Were any materials biodegradable in
the sand?
3. Did
any of the materials degrade in the sanitary landfill? Why or why not?
4.
What material degraded the most rapidly?
5.
Given your results, what soil type would you use to cover waste in a landfill?
6.
What are the advantages and disadvantages of both sanitary and open-air landfills?
7.
What steps can you take to reduce the amount of trash being placed into landfills?
—5—
1N10476
© 2002 Flinn Scientific, Inc. All Rights Reserved. Reproduction pennission is granted only to science
teachers who have purchased Landfill Decomposition, Catalog No. P130425, from Flinn
Scientific,
Inc No part of this matenal may be reproduced or transmitted m any form or Lw any mean pI’rtnn.
o,. mechamcal mc udng but not onited to photoi.opy recordmg or any mformation storage and
retrieval system, without permission in writing from Plinn Scientific, Inc.