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Compost in a bottle

Healthy soil is an important part of nature. In this science experiment, we’re going to compost food scraps to create nutrient-rich soil. It takes about 3 weeks.

For a few days before you start, collect scraps of food (apple cores, banana peels, potato skin) in your fridge.

There are two types of things you can compost:

  1. carbon rich (dry leaves, paper or newspaper) and
  2. nitrogen rich (cut grass, food scraps).

A good ratio is one part carbon rich to two parts nitrogen rich.

When you mix these with dirt, water and air it will attract bacteria and fungi, which will start to feed on the organic material. As they do this it will create heat that helps speed up the process.

Compost materials.
Compost materials.

What you’ll need:

  • Two-litre clear plastic bottle
  • Dirt from outside (not potting mix)
  • Nitrogen-rich fruit or vegetable scraps
  • Carbon-rich shredded paper or dead leaves
  • Sharp scissors or a knife (and maybe an adult’s help to use them)
  • An old plate or tray (to collect drainage)

A bottle of composted soil can help grow new plants.
A bottle of composted soil can help grow new plants.


  1. Wash and peel any labels off the bottle (so you get a good view of what’s happening inside)
  2. Cut the top off the bottle and put it aside
  3. Poke 8 to 10 small drainage holes around the sides and bottom
  4. Put some newspaper, 5 cups of dirt and food scraps into the bottle
  5. Stand it on the old plate or tray
  6. Wet the mixture
  7. Turn the bottle lid upside down and put it in the top as a funnel for adding a bit of water each day to keep it damp.
  8. Put it somewhere it will get sun and cover the top with a towel
  9. Check the compost each day and stir it around so the bacteria can find new food!
After a few weeks you’ll see the food scraps break down into soil. Now you can take this healthy soil and plant something in it!