The Rotten Truth
1. Ask the students to name some of the things they have thrown away over the past two days. What happens to these things? Do they disappear? Decompose? Remain in the same form forever? Record the students' ideas on the blackboard. Explain that they will conduct an experiment with the leftovers from their lunches to learn the fate of some common throw-away items.
2. Give each student a plastic zip-locked lunch bag. Explain that they will place one small piece of each item in their lunch into the bag. This includes food, peelings, a corner of the lunch bag, paper napkins, plastic bags, waxed paper, plastic utensils, paper cups, milk cartons, and straws. Have them use scissors to cut items up, if necessary. Stress that they not add any meat to their bags as potentially harmful bacteria could grow.
3. Divide The class into pairs. While one student adds items to his or her compost bag, have the other student record the exact contents. The recorder should also note his or her partners' predictions as to what will happen to each item over time. Will it rot? Smell yucky? Remain the same? Have the students switch roles and create a second compost bag with a list of contents and predictions.
4. Ask the students to add a sprinkling of soil to their bags and to lightly mist the contents with a plant mister. Have the students breathe air into the bags and carefully seal them. Explain that they will leave the bags for 2-8 weeks. You may decide to keep all the bags together, or place them in various locations with differing conditions (hanging in a sunny window, hidden inside a dark closet, in a cool entry way, etc.). Ask the students if these varying conditions might have a different effect on what occurs in the bags. (If you let the students choose their compost bag's location, be sure to have everyone register their location on a class master list or you may be unpleasantly suprised when a missing bag finally makes its presence known.)
5. Have students create compost bag journals. Ask them to observe their bags periodically and record what they see happening inside. Remind the students that they are not to open the bags until the designated time is up.
6. On the selected date, have the students bring their compost bags outdoors. Distribute rubber gloves for the students to wear while sorting through the contents of their bags with their partner. Record any items still identifiable and their present state. Are any items missing? Provide plant misters so items can be cleaned off for closer observation and identification. How did the results compare to the predictions?
7. Define and discuss the process of decomposition and decay. Explain how certain materials are broken down by microorganisms, mainly bacteria and fungi, into basic nutrients and recycled back into the soil. Talk about composting as an alternative to the garbage dump for certain items. Introduce the terms biodegradable, non-biodegradable, recyclable, and reusable (see Waste Words). Have the students sort the items in their compost bags into these categories.
a. Have the students conduct a similar experiment burying selected lunch items in clay or plastic plant pots. After 2-8 weeks, empty pots and sort through the contents. Compare and contrast decomposition times between the pots and the plastic sandwich bags.