4. Crazy compost

4. Crazy compost

Suggested timing: January

Compost is used to enrich the soil with nutrients and moisture. It is full of minerals and organic matter made from the mulching and decomposing of other materials we no longer use.

Short film: Crazy Compost


By the end of this unit, you will enable children to:

  1. Understand the process of composting
  2. Learn about the role of microorganisms in the soil and the cycle of materials
  3. Learn to sort different materials for making compost
  4. Recycle materials for composting
  5. Collect organic waste for composting
  6. Built a compost bin

1. From rubbish to composting

Compost is a mixture of materials which have been brought together thanks to the actions of living organisms – both by physically breaking down materials, and also by triggering chemical transformations. In particular, organisms in the soil (for example worms, bacteria and fungi) break bigger molecules into smaller ones, which then pass into the soil where they can be absorbed by the plants (this is known as cycling of matter). Good and effective composting action requires:

  • Organisms in the soil
  • Water, air and sun
  • Other plants (as the roots of the plants can help too!)
Activity 1A: Investigating composting action

Cards illustrating different organisms and environmental factors can be used to help the children learn about and recognise the different factors involved. Drama-based activities can be used to illustrate the work of the organisms in the soil and the interaction between the different elements.

Useful resources

2. Is composting a bit like recycling?

Yes… and no… as not everything can be put into the mix for making compost.

  • Paper and cardboard are good. They can be shredded, and once in the soil they’re good for retaining moisture
  • Some food waste, for example egg shells, can also be used. Not general food waste though as it can attract rats (for more guidance on what to compost, or not, see Useful Resources -What can I compost?).
  • Plastic and glass should be discarded as normal in the recycling bin
Activity 2A: Sorting waste products

Pictures showing a variety of everyday waste products can be used to practice the process of ‘sorting’ waste for composting. The first step is to identify which are organic, and which are inorganic materials:

  • Organic materials come from living things, plants and animals. This includes the food we eat, and some of the clothes we wear and things we use - for example those made from leather, cotton, and wool. Organic products all contain an element called carbon which is essential for living things.  Many organic materials can be composted quite quickly, but some take a long time to break down and so can’t be used in compost - for example cotton and wool (however, they can be re-used and recycled).
  • Inorganic materials come from sources which are not living. While some of these do contain carbon, for example diamonds and plastics, they’re in a form which can’t be easily broken down and used by living things, and certainly can’t be used in compost. Many inorganic materials contain useful minerals and perhaps other elements, for example Nitrogen and Sulphur, which we can use in different ways.

The sorting activity stimulates children to consider ‘rubbish’ in greater detail – so to not think of it solely as one general category (where consideration of the origin and destiny of individual components is ignored), but instead they are guided to ‘make categories’ for practical use:

  • Brown bin: this is best used for raw waste vegetable trimmings left over from food preparation, or tough woody cuttings from the garden and other garden waste. Other organic materials such as cold ashes and tissue paper can be put in the brown bin. Most local authorities have kitchen caddy food waste collections for cooked food, although some will allow this in the brown bin.  It is best to check with your local authority what they allow and don’t allow in the brown bin
  • Recycling bins: for cardboard, plastic and glass
  • General waste: for all things that cannot be recycled
Activity 2B: Collecting suitable waste for composting

Children in the whole school can collect organic produce for composting in each of their classes – for example from fruit snacks. Classes can discuss the guidance on food waste provided by the local authority and other sources. They can then decide which materials to put into the school compost (for example apple cores and some fruit and vegetable peel), and which to put into the kitchen caddy or brown bin for council collection. Guidance for schools on reducing food waste can be found in the Useful Resources.

Activity 2C: Making a compost bin

With the help of the janitors and/or school technicians or parents, children can help build a compost bin for use in the garden.

Useful resources

You have reached the end of this unit. To assess your knowledge before starting the next unit, please complete the short quiz found at the link below.

Please note: you will have to enter your email address at the start of each unit quiz if you wish to be sent a Garden Schools Certificate of Completion once you have worked through all 8 units and quizzes.

Complete the Crazy Compost short quiz