Correct Option
The correct option is (c).
Explanation
Compressed Natural Gas (CNG) is a fossil fuel substitute for gasoline (petrol), diesel, and propane/LPG. It is comprised primarily of methane ($CH_4$) compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is recognized for its efficiency and lower environmental impact compared to traditional solid and liquid fuels.
Statement-wise Analysis
- Statement 1 is Correct: CNG is widely used as a fuel for automobiles, including buses, cars, and auto-rickshaws. It is favored in the transport sector because it is cost-effective and reduces engine maintenance due to cleaner combustion.
- Statement 2 is Incorrect: CNG causes less pollution than petrol and diesel. Upon combustion, it produces significantly lower levels of toxic gases such as carbon monoxide (CO), nitrogen oxides ($NO_x$), and non-methane organic gases. It also emits very little particulate matter compared to liquid fuels.
- Statement 3 is Correct: Calorific value indicates the amount of heat energy released by the complete combustion of a unit mass of fuel.
- The calorific value of CNG is approximately 50,000 kJ/kg.
- The calorific value of wood is significantly lower, typically ranging between 17,000 and 22,000 kJ/kg.
Key Takeaway
CNG is a cleaner-burning fuel primarily composed of methane. It possesses a significantly higher calorific value than solid fuels like wood and emits fewer pollutants than liquid fuels like petrol and diesel.