Talk It Over

One way of recycling kitchen waste is to make compost and use it in the garden. What is compost? How is it made? How does composting recycle waste?

Get

• 6 ziptop, plastic bags, sandwich size
• Labels and pen
• 6 plastic straws
• Digital instant-read thermometer*
• Scissors
• Tape
• Lettuce
• Knife
• Newspaper
• Kitchen scale
• Water
• Measuring spoons

Go

In bags 4–6, mix the lettuce and newspaper evenly inside the bag.

1. Label the bags 1, 2, 3, 4, 5, and 6.
2. Make sure the probe of the thermometer fits through the straws. Cut the straws so they are about 2 cm (1 inch) shorter than the thermometer probe, like this:
3. Tape 1 straw inside each bag, so that about 1 cm sticks out above the top of the bag, like this:
4. Ask an adult to chop the lettuce into very small pieces—the smaller, the better. Use scissors to cut the newspaper into tiny pieces.
5. On the kitchen scale, weigh lettuce and newspaper, and add them to the bags as indicated in this chart:
6. Add a tablespoon of water to each bag. Check to make sure the bottoms of the straws extend into the bag's contents but do not touch the bottom of the bag:
7. Seal the ziptop from both edges toward the straw. Tape around the outside of the straw to seal the bag shut.
8. Set the bags in a warm, dark place.
9. Every day for several days, measure and record the temperature of the air near the bags. Also record the temperature inside the bags, inserting the thermometer's probe through the straws. Also make notes about what you see in the bag.
10. When the experiment ends, throw the bags away without opening them.

Stay Safe

Don't cut the lettuce yourself. Ask an adult to do it for you. Don't open the bags once they are sealed. The contents may contain dangerous microbes. Don't try this experiment if you have mold allergies.Wash your hands before and after handling the bags.

Go Easy

Set up only bags 1–4. Ask an adult to help you with weighing and taking temperatures inside the bags.

Go Far

"Go" offers a basic procedure you can use to investigate composting. Modify it to investigate factors you think may affect the speed of the decay process. You might, for example, find out whether temperature, the size of the pieces, or light/dark conditions affect the speed of the breakdown. You might also experiment with other materials such as grass clippings, potato peels, apple cores, cardboard, wood shavings, sawdust, straw, or leaves. Or you might assess whether some of the commercial products that are sold to speed up the composting process actually work.

Show Your Results

Pick a day when you noticed temperature differences among the bags. Make a bar graph that shows the difference. In your report, explain how bag 1 serves as a control. Tell what the temperature difference in other bags reveals about the composting process

For "Go," add rows for bags 5 and 6 to your data table. Make a line graph of temperatures (on the vertical axis) by time (on the horizontal axis). Use lines of different colors to represent temperatures inside the individual bags. If you see differences in bags 4–6, what explains them? Do your results tell you anything about the best mixture of composting materials?

For "Go Far," modify the data table to fit your experimental design. Make line graphs that help you answer the question you chose to investigate.

For "Go Easy, put your data in a table like this:

Tips and Tricks

• Old, slightly stale lettuce works best.
• Don't use color print or glossy magazine sections from the newspaper. Use plain, black-and-white printed pages.
• If you don't get good results with this experiment, try again, adding more or less water. The moisture level inside the bag is important.
• Do not put meat, milk, or animal fats or foods in the bags. You won't like the results.

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