Resources & Activities

Creating compost in a bag with kids

Compost in a Bag is a way for children to easily understand the decomposition process, and to learn the full cycle of an edible plant - from soil to seed to plant to table to soil.

A zip-lock bag filled with compost with a straw poking out
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Supporting children to understand the life cycle of plants (in this case edible plants) can set them up with lifetime skills for gardening and growing food. Understanding the decomposition of plant matter process is an important part of the cycle. Compost in a bag is a simple way to help children understand this process, regardless of whether you regularly compost and grow food or not. This is a great activity for children who live in urban areas and may not have access to gardens regularly. 

Materials needed

  • Ziplock plastic bag or a small plastic container
  • Paper or metal straw
  • Cardboard egg carton
  • Fruit and vegetable scraps
  • Water 

How to

  1. Fill a Ziplock bag with old food scraps 
  2. Add a shredded up egg carton or any old cardboard into the bag
  3. Place a straw in the corner of the bag and seal the bag up, leaving a small gap for air to flow through the straw
  4. Keep the compost bag watered every couple of days and mix up the contents of the bag so it can compost evenly
  5. After a couple of weeks, you should have compost ready to add to soil and to plant thriving vegetables!

Teaching Strategies

  • Revisit the bags or containers daily with children, and take photos to show the changes occurring over time
  • Ask children what they can see, smell or notice. This is a great opportunity to use and introduce new and descriptive words such as ‘decompose’, ‘decay’, and ‘rot’
  • Create a graph of the changes you notice happening
  • Ask children to feel the bag, and prompt them to share what they notice
  • Record children’s responses and capture their ideas in a display with the photos
  • Add different items (such as plastic food wrap) to different bags so children can compare what is happening. Discuss why some things rot, and others don’t
  • Experiment with larger and smaller pieces of the same fruit or vegetable and see if this impacts on the time taken to decompose. Record children’s hypotheses
  • Run some experiments - what will happen if you have two bags with identical pieces of food inside. Seal one bag completely and don’t add water or air. Compare this bag to the one with a straw in it, getting water and air. Why is this happening? What is different?
  • Discuss the food that is thrown away after eating. What happens to it?
  • Use the compost from the bag in your garden to help your plants grow. Do plants without compost grow at the same speed?

Possible learning outcomes

  • The process and stages of decomposition
  • The time taken for decomposition to occur
  • Why some foods decompose in different amounts of time
  • The conditions needed to support decomposition of food 
  • Observing differences and similarities
  • Recording and analysing data
  • Comparing, contrasting, sorting and classifying
  • Scientific concepts eg observing, making predictions, testing predictions, deciphering results, biology etc
  • A curiosity about gardening 
  • Environmental awareness
  • Research skills 
  • A responsibility for the living world


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