Timeline for Decomposition

Sort your garbage on a timeline to better understand decomposition.


To understand the differences between the different types of garbage and how long they remain in the environment


  • Long piece of string
  • Index cards
  • Marker
  • Garbage items (e.g., paper, cardboard, fruit scraps, rubber, plastic, tin, glass)
  • Or printed images of garbage items: Leave No Trace Activity [PDF]


30 minutes


Before the activity, lay out the string and mark time intervals on it using the marker, trying to space them according to the time scale. Points in the line include 1 week, 2 weeks, 3 weeks, 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 1 year, 2 years, 5 years, 10 years, 20 years, 50 years, 100 years, 200 years, 300 years, 400 years, and 500 years. Label the points using index cards.

Now, give each kid a piece of garbage and ask them to place their item at the place on the timeline that indicates how long they think it takes to decompose in the environment.

Once they have done this, reveal the actual decomposition times to the group, using the decomposition table. Follow up by asking the kids if anything surprised them about the decomposition times. Ask them why they think some substances take longer than others to decompose.

Discuss the difference between organic and inorganic waste. Ask the kids how they feel about this information and about trash, and whether they might want to do something to improve the situation in the community.

Garbage and Decomposition Times

(Note: Though the figures below come from authoritative sources, these are best-guess estimates. No one has been around for 1 million years to prove that this is the time required for glass bottles to disintegrate! Furthermore, decomposition times vary according to temperature, rainfall, soil conditions, and other environmental and climatic factors. Decomposition occurs much more rapidly in a tropical rain forest than in the Sahara or Atacama Desert or in the high Himalayas.)

• Paper towel (2–4 weeks)
• Orange peel (2–5 weeks)
• Cotton cloth/rag (1–5 months)
• Milk carton (3 months)
• Aluminum can (80–200 years)
• Plastic bottle (450 years)
• Glass bottle (1 million years)

This lesson plan is an activity from the Environmental Activities for Youth Clubs and Camps, a resource developed by the Peace Corps Office of Overseas Programming and Training (OPATS). It was contributed by Peace Corps/Paraguay, Peace Corps/Mexico, and Peace Corps/Armenia.

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