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π¬ Think about it
Fallen leaves and fruit peels pile up everywhere, yet the Earth is not buried under them. Something quietly clears them away. What is it? Let's find out.
What is decomposition?
Decomposition
de–
to break down
composition
complex, built-up matter
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Decomposition is the breaking down of complex waste into simpler, nutrient-rich substances.
- It is the breaking down of dead plant and animal matter.
- Microbes turn it into simpler, nutrient-rich substances.
- These nutrients go back into the soil.
How do microbes help farmers and nature?
What happens to plant waste in the soil?
Dead matter and waste
Leaves, peels, dead bodies
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Microbes decompose it
Fungi and bacteria break it down
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Nutrient-rich manure returns to the soil
- They break waste into manure that makes soil fertile.
- They recycle nutrients back to nature.
- They also decompose dead animal bodies.
How do microbes also give us biogas?
How do microbes give us biogas?
Plant and animal waste
Or household wastewater
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Bacteria without oxygen
They decompose the waste
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Biogas is released
Mostly methane, with carbon dioxide
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A fuel for cooking, heating, electricity and vehicles
- Some bacteria break down waste without oxygen.
- This releases biogas, mostly methane and carbon dioxide.
- Biogas is used for cooking, heating, electricity, and even vehicles.
π±
Activity 2.7 — Let us do
How do peels turn into manure?
Half-fill a container with garden soil
An empty container is enough
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Add fruit and vegetable peels
Then put a layer of soil on top
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Leave it aside for 2–3 weeks
Do not disturb it
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Open it and look
The peels are gone
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Fungi and bacteria have broken the peels down into dark, nutrient-rich manure
In this Activity, we will bury fruit and vegetable peels in soil and watch what the microbes turn them into.
Materials needed
Fruit and vegetable peels, a pit or a pot of soil, and some water.
Procedure
1. Collect fruit and vegetable peels from the kitchen.
2. Dig a small pit, or take a pot filled with soil.
3. Bury the peels under the soil.
4. Sprinkle a little water to keep the soil slightly moist.
5. Leave it and check the peels after 2–3 weeks.
2. Dig a small pit, or take a pot filled with soil.
3. Bury the peels under the soil.
4. Sprinkle a little water to keep the soil slightly moist.
5. Leave it and check the peels after 2–3 weeks.
Observation
The peels turn into dark, crumbly manure.
Explanation
Fungi and bacteria broke down the peels, showing that microbes clean the environment and enrich the soil.
Fungi and bacteria break peels down into dark, nutrient-rich manure.
β Summary
- Buried peels are decomposed
- Microbes turn them into manure
- Shows microbes recycle waste
Important Points
- Microbes recycle waste and return nutrients to nature.
- Manure forms best at the right temperature and moisture.
π Our scientific heritage
- Ancient Indian texts like the Vedas and Atharvaveda mention "Krimi".
- Krimi means tiny entities, both visible (Drishya) and invisible (Adrishya).
- These texts describe their helpful and harmful effects.
π¬ Be a scientist
- In 1971, Ananda Mohan Chakrabarty developed a special bacterium.
- It could break down oil spills and clean the environment.
- His discovery earned a patent in 1980.
- His work showed microbes can help solve pollution problems.
Important Definitions
- Decomposition — Breaking down of dead matter by microbes into simpler, nutrient-rich substances.
- Manure — Nutrient-rich material formed when microbes break down plant and animal waste.
- Biogas — A fuel gas (mainly methane) released when microbes decompose waste without oxygen.
π NCERT Question 4 — Snehal dug two pits
Snehal dug two pits, A and B, in her garden. In pit A, she put fruit and vegetable peels and mixed it with dried leaves. In pit B, she dumped the same kind of waste without mixing it with dried leaves. She covered both the pits with soil and observed after 3 weeks. What is she trying to test?
View Answer →
π NCERT Question 7 — Take 2 slices of bread
Take 2 slices of bread. Place one slice in a plate near the sink. Place the other slice in the refrigerator. Compare after three days. Note your observations. Give reasons for your observations.
View Answer →
π A step further
Microbes as a source of biogas
- Many microbes, like bacteria and fungi, live in an oxygen-free environment.
- Some of these bacteria break down plant and animal waste, or household wastewater.
- During this they release a mixture of gases called biogas .
- Biogas is mainly carbon dioxide plus a high proportion of methane .
- It is used as fuel for cooking, heating, generating electricity, and even to run vehicles.
