Cow dung is appropriately used as

Options

A. Manure
B. Fuel
C. Medicine
D. Building material

Answer

**Step-by-Step Solution:**

1. **Identify the Use of Cow Dung**: Cow dung is commonly used in rural areas, particularly in biogas plants.

2. **Understand the Process in Biogas Plants**: In a biogas plant, cow dung is collected and subjected to anaerobic digestion. This is where specific bacteria, known as methanogens, play a crucial role.

3. **Role of Methanogens**: Methanogens are a type of bacteria that break down organic matter, including cow dung, in the absence of oxygen. Their primary function is to produce methane gas (CH4) as a byproduct of this breakdown.

4. **Byproducts of the Process**: During the anaerobic digestion of cow dung, several gases are released:
- Methane (CH4) – the main gas produced and used as fuel.
- Carbon Dioxide (CO2) – another byproduct.
- Hydrogen Sulfide (H2S) – a gas that can also be produced.

5. **Final Products**: After the biogas is collected, the leftover material from the digestion process can be used as manure, enriching the soil with nutrients.

6. **Conclusion**: The most appropriate use of cow dung in this context is as a source of fuel, specifically in the form of biogas.

**Final Answer**: Cow dung is appropriately used as fuel.

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