Compost Cups Science Project

Compost Cups Science Project at The Happy Housewife

By contributing writer Marci

As we walked through the autumn forest and noticed the falling leaves, I asked the kids what happened to the piles of leaves we walked through last year. That started a conversation about decomposition.

Decomposition and Composting

Decomposition is the process in which organic material is broken down into simpler forms of matter (according to Wikipedia). It’s natural recycling!

When leaves fall and plants and animals die, they start this process of breaking down or decay. Insects, bacteria, and fungus all carry out decomposition. In the end, dead matter decays and is turned back into soil. That’s what happened to the piles of leaves from last fall.

You might have a compost bin or pile at your house where your yard, garden, and kitchen waste are decomposed to create nutrient rich soil that can be put back into the garden.

Make Your Own Compost Cups

To study composting up close, we decided to create our own mini compost bins in cups, so we could see decomposition in action. You can make your own compost cups science project with these easy steps.

Supplies Needed

  • 16 ounce plastic cup
  • Organic items such as grass clippings, kitchen scraps (no meat or dairy), leaves, coffee grinds, bark, etc.
  • Plastic wrap
  • 1 tablespoon water
  • 1/4 cup dirt
  • Rubber band or tape


1. Place organic material, dirt, and water in the plastic cup.

Compost Cups Science Project at The Happy Housewife

2. Cover the cup with plastic wrap and seal with a rubber band or tape. Give it a good shake and place it in a warm, sunny place like a window or safe spot outside where it won’t be disturbed.

Compost Cups Science Project at The Happy Housewife

3. Every couple of days add another tablespoon of water and give it a shake. Note what is happening to the organic matter.

What Happens?

The warm environment of the cup increases the activity of the microbes inside. These bacteria and fungus go to work breaking down the organic matter in the cup. The added water and oxygen from the shaking keep the process going.

Within a day or two you can see this happening. Given enough time, you’ll be able to see the organic matter turn into dark, nutrient rich compost that can be added to garden soil.

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