Mini rot pot


Make your own mini bottle composter to observe the composting process first-hand.

  • Estimated time: 30 minutes
  • Location: Outdoors
  • School term: All year round
  • Level of experience: No experience needed
  • Subject(s): Science, Art&DT, Social Studies

Learning objectives

  • Understand that composting is a natural process and part of the nitrogen and carbon cycles
  • Closely observe a scientific process and make simple equipment


Walk around the school grounds and collect compostable materials, e.g. fruit and vegetable peelings, leaves, small twigs, straw or grass clippings.


  • Selection of compostable plant material
  • One non-compostable item (i.e. plastic)
  • Scissors
  • Large clear plastic bottle (one per group or per pupil if enough space)
  • Elastic band and piece of porous material to cover the top (an old sock works well)
  • Water in spray gun
  • Scoop of garden soil
  • Wipe down surface/newspaper to cover table

Step by step

  1. Discuss the word ‘compost’ and why you are doing this activity.
  2. Cut all the garden materials into small pieces.
  3. Cut the top off the plastic bottle.
  4. Add compostable ‘ingredients’ to the bottle, mixing different types together as they go in. Sprinkle a little soil through the layers. Don’t forget the plastic section.
  5. When adding the ingredients spray with water so the mixture is moist like a damp sponge.
  6. Fill to the top of the bottle and then cover with cloth secured with an elastic band.
  7. Put it in a warm place such as a sunny window ledge. Over the next six weeks empty out the contents each week, mix it all together and put back in the bottle. Ensure it is kept moist.

Hints & tips

  • Speed up the processes of composting by mixing regularly to add air, adding water to keep it moist and placing the rot pot in a sunny place.
  • Mix different plant materials together to provide nutrients such as carbon and nitrogen and add microorganisms that live in garden soil.
  • Use this activity as part of the Earth Matters class growing topic.