Compost Lab: Turn Waste into Soil
Understand composting as feeding microbes: they need carbon (browns), nitrogen (greens), water and air in the right balance; get it right and the heap heats and finishes in weeks, get it wrong and it goes slimy and smells.
Before you try
What if you only put wet kitchen scraps in the bin? Why would it smell?
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What happened?
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Three scores multiplied into a daily rate with rounded ideal ranges; real heaps also depend on size, chopping and weather.
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Try these ideas
- Try the Wet kitchen scraps only preset and watch what happens.
- Find the greens-to-browns mix that gives a C:N ratio near 30:1.
- Turn the heap 3 times a week and see how many days it saves.
Why it works
Compost is made by billions of bacteria and fungi eating dead plant matter. They need carbon for energy, which comes from browns such as dry leaves, straw and paper, and nitrogen to build their bodies, from greens such as peelings, grass and dung. A mix of about 30 parts carbon to 1 of nitrogen suits them best. They also need water, about as much as a wrung-out sponge, and air, which is why a heap is turned.
When everything is right the microbes work so hard the heap heats to 50 to 65 °C, hot enough to kill weed seeds and germs, and finishes in a month or two. Too wet and airless, the oxygen-breathers die off and slow, stinking anaerobic decay takes over. The NCERT chapter on garbage recommends composting for exactly this reason: kitchen waste becomes food for the soil instead of landfill. In this lab you set the mix, the moisture and the turning and run the days.
Check your understanding
Question 1 of 4
A compost heap that smells of rotten eggs is
“Browns” such as dry leaves supply
A well-balanced heap gets hot because
Turning the heap helps by
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Start a small compost jar with peelings and dry leaves and check it weekly.
- Ask: why does a pile of wet grass cuttings get warm inside?
- Find out what your school does with its canteen waste.