Question

Biochar produced by incomplete combustion of biological materials is rich in

• A. Nitrogen
• B. Sulphur
• C. Phosphorus
• D. Carbon

Hint:

Think about what element survives when biomass is charred instead of fully burned.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Biochar is the solid material left over when plant or animal biomass is burned with a limited air supply, a process called pyrolysis or incomplete combustion. This question asks what element makes up most of that leftover material.

Step 2: Key Formula or Approach:
When organic material burns fully in plenty of oxygen, carbon mostly escapes as carbon dioxide gas. Under incomplete combustion, with restricted oxygen, much of that carbon does not burn away completely and instead stays behind as a stable, blackened solid.

Step 3: Detailed Explanation:
Nitrogen, sulphur and phosphorus are present in the original biomass only in small amounts compared with carbon, and a good part of the nitrogen is actually lost as gas during heating. Carbon, on the other hand, is the main building block of plant tissue, cellulose, lignin and other carbon compounds, and under incomplete combustion this carbon skeleton survives largely intact as charcoal-like biochar. This is why biochar is valued as a soil amendment, it adds a stable, long lasting form of carbon to soil, improving carbon storage and soil structure.

Step 4: Final Answer:
Biochar from incomplete combustion is rich in carbon, so option 4 is correct.