Consider the following:- 1) Carbon dioxide 2) Oxides of Nitrogen 3) Oxides of Sulphur Which of the above is/are the emission/emissions from coal combustion at thermal power plants?

Coal is mostly carbon with sulphur and nitrogen compounds in it, so burning it in a thermal power plant releases all three: carbon dioxide, oxides of nitrogen and oxides of sulphur. The answer is D.

• Statement 1 (CO2): Complete oxidation of carbon gives CO2. It is the largest greenhouse gas emitted by coal plants, which is why coal is central to climate policy debates.
• Statement 2 (NOx): At the high flame temperatures in boilers, atmospheric nitrogen combines with oxygen to form NOx. Fuel-bound nitrogen adds to this.
• Statement 3 (SOx): Sulphur in coal oxidises to SO2, and sometimes SO3. This is the reason for flue gas desulphurisation (FGD) requirements under MoEFCC emission norms for thermal plants.

The core concept is combustion chemistry applied to a fuel's composition. For Mains GS-III (environment and energy), this links to the trade-off between energy security and air quality, and to the notified emission standards for power plants. Compliance timelines for those standards have been extended more than once, so check the current position before using it in an answer.

Trap: Students often assume that CO2 is not a "pollutant" in the usual sense and drop statement 1, or they think only SOx matters because it is linked to acid rain. In a statement-based question, every real combustion product of coal counts.