- What
Is Biodegradable?
- (Adapted from
Recycle Alaska Activities Handbook,
- Alaska Department
of Environmental Conservation, Juneau, AK)
-
- GRADE LEVELS: 4-6
-
- SUBJECT AREAS:
science
-
- CONCEPT:
Some materials decompose when buried; others do not. Microorganisms
play a vital role in the decomposition process.
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- OBJECTIVE:
Students will be able to differentiate between the kinds of
material that nature recycles and those it does not.
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- MATERIALS:
- ten pieces of each of the following:
- glass
paper
steel or other metal
plastic
apple, lettuce, or other fruit or vegetable
- ten containers, jars, or flower pots
soil
sterile potting mix
masking tape or labels
handout: Watching Wastes Rot: Record
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- KEYWORDS:
biodegradation, decomposition, microorganisms
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- BACKGROUND:
Decomposition occurs everywhere. If everything existed forever,
we would be buried in our waste. Our waste products are varied:
some are made of easily degradable materials while others will
last for thousands of years.
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- PROCEDURE:
- Display a piece of glass, paper, metal,
plastic, and food. Ask the class to predict which of these substances
are biodegradable (capable of rotting or decomposing)? Conduct
the following experiment to determine whether their predictions
were correct.
-
- Dig enough soil from a garden or vacant
lot to fill five containers. (One pound cottage cheese containers
would be suitable.) Fill five of the containers half fullwith
soil, and the other five half full with sterile potting mix.
Place a piece of each type of waste into each container. Continue
filling the containers with soil or sterile mix, whichever they
already contain. Add enough water to all pots so that the soil
or sterile mix is damp but not wet to the touch. Cover the containers.
Label the containers to indicate the type of waste and whether
it contains soil or sterile mix.
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- After one week, examine the waste in
each container. Which wastes are decomposing? Cover the wastes
again, and continue to check them once a week for as long as
you want. Record your observations.
-
- Check the original predictions and
draw conclusions about which substances are biodegradable and
under what conditions.
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- FOLLOW-UP:
- Explore degradable plastics. Many producers
of plastic bags are now producing plastic bags they say will
degrade.
-
- There are two types of degradable plastic
bags; photodegradable and corn starch biodegradable.
-
- Find out what makes these plastic bags
degrade and perform an experiment similar to the one above.
- Questions:
- 1. What makes these plastic bags degradable?
2. Does the whole bag degrade? Are there any waste products left
over?
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- Watching Wastes Rot: Record
-
- Name: _____________________ Date experiment
started: ________
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- Fill in the following table each time
you check your pots. Under "Waste", write the name
of the item that you buried in the pot. Under "Compost",
describe the condition of the item buried in compost each time
you check it. Include such things as how decomposed the item
looks, what color it is, whether or not you see fungi (spots
or thin strands) on it. Under "Sterile Mix", describe
in the same way the condition of the item buried in the sterile
mix.
-
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- Date: _______________ Time since waste
was buried: _____________
-
-
| Waste |
Compost |
Sterile Mix |
| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
-
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- Which items decomposed most quickly?
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- Which items didn't decompose to all?
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- In general, did items decompose more
quickly in compost or in sterile mix? Why do you think this is
true?
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