Question

Process of conversion of dead vegetation into coal is called

• A. Hydrogenation
• B. Calcination
• C. Carbonisation
• D. Oxidation

Hint:

Remember: Carbonisation = conversion of organic matter (dead plants) to coal (rich in carbon) under heat and pressure over geological time. The stages of coal formation in order of increasing carbon content are: Peat $\rightarrow$ Lignite $\rightarrow$ Bituminous coal $\rightarrow$ Anthracite. Anthracite has the highest carbon content ($\approx$92--98%) and highest calorific value.

Answer 1

The Correct Option is C

Concept:
Coal is formed from the remains of dead plants and vegetation that lived millions of years ago. The process by which dead organic matter (vegetation) is gradually transformed into coal under conditions of heat, pressure, and absence of air over geological time periods is known as

carbonisation (also called coalification or the process of coal formation).

Step 1: Detailed explanation of Carbonisation.
Carbonisation (or carbonization) is the process in which organic material is converted to carbon or a carbon-containing residue through

pyrolysis (thermal decomposition in the absence or limited presence of oxygen). In the geological context:

• Dead vegetation (plants, trees) accumulated in swampy areas over millions of years.

• These were buried under layers of sediment (sand, mud, rock).

• Over millions of years, increasing pressure and temperature drove off volatile components (water, hydrogen, oxygen, nitrogen).

• The remaining material became progressively richer in

carbon.

• The stages are: peat $\rightarrow$ lignite (brown coal) $\rightarrow$ bituminous coal $\rightarrow$ anthracite.

Step 2: Analyse wrong options.

• (A) Hydrogenation: This is the addition of hydrogen to a molecule (e.g., converting unsaturated fats to saturated fats, or making margarine from vegetable oils). It has nothing to do with coal formation.

• (B) Calcination: This is the thermal treatment of a solid mineral (usually with limited air) to cause thermal decomposition, phase transition, or removal of a volatile fraction. It is used in cement making (heating limestone to form lime: CaCO$_3$ $\rightarrow$ CaO + CO$_2$). Not related to coal formation.

• (D) Oxidation: Oxidation involves the loss of electrons or addition of oxygen. If vegetation were oxidized, it would combust or decompose aerobically --- not form coal. Coal formation requires the exclusion of oxygen.

Step 3: Coal as a fossil fuel.
Coal is a fossil fuel because it is derived from ancient living organisms (vegetation). The energy stored in coal originally came from sunlight captured by photosynthesis millions of years ago. When we burn coal, we are releasing this ancient solar energy.