Lesson Plan

Composting and Decomposition

Subject: Science
Duration: Two 45 minute sessions within a month of each other

This month-long activity shows kids how organic wastes dramatically transform into valuable compost.


To see what composting can do with organic waste


  • Large plastic bag
  • Soil
  • Materials to decompose
  • Index card or paper
  • Tape
  • Screen or netting if available
  • White poster board or butcher paper (desirable)


Day 1:
  • Begin by telling the group that you have the ingredients for a recipe. Ask them if you always know what the results will be when you mix ingredients together, and to share any examples they know of to support their thoughts. Now, ask the kids to guess what will happen when you mix the compostable materials together.
  • Take the large plastic bag and put a gallon of damp soil in it. Add the materials you want to compost (food scraps, paper, wood chips, grass, leaves, etc.). Mix all the ingredients well into the wet soil so they are distributed throughout the bag. Blow the bag up with air and then close it tightly. Record on a card what was put in the bag and the date it was sealed up; tape it to the bag. Hang a sign on the bag that says: “What’s going on in here?” Put the bag out of the way. Ask the kids what they think will happen, and write down their responses (or ask them to write down their predictions in journals or draw what they think the contents will look like in a month).
Day 2:
  • After a month, ask the kids to read the list of materials that were put in the bag. Ingredient by ingredient, ask them to hypothesize what happened to each. Now, open the compost bag outside and pass the contents through a screen or netting, if available. Sprinkling the contents on white poster board or butcher paper will enable the kids to see them more clearly.
  • o follow up, discuss decomposition, decay, and nutrient recycling. Introduce composting as a way to put nutrients back into the soil using natural decomposition. Explain that composting takes nature’s process of recycling nutrients and accelerates it. A well-made compost heap creates an environment in which bacteria, fungi, and other organisms can live, feasting on the organic matter and converting fresh manure, food scraps, leaves, seeds, wood ashes, sawdust, and other compostable materials into dark humus. All healthy compost piles need an equal mass of nitrogen-rich materials, such as food scraps and manure, and carbon-rich materials, such as dry grass, wood chips, and paper products, as well as air and water to keep the aerobic bacteria happy.

Assessment & Evaluation

After month-long decomposition, have the kids observe the condition of the ingredients, refer back to their original predictions, and draw conclusions. What changes occurred?


You can also do this decomposing activity with plastic to show that it decomposes very slowly. This can lead into a discussion of waste pollution.