CNG vs LNG vs PNG — Differences, Formation, Uses | Natural Gas Forms UPSC Prelims MCQ 2026

With reference to the various forms of Natural Gas, consider the following pairs:
1. CNG (Compressed Natural Gas) — Natural gas compressed to less than 1% of its volume at standard atmospheric pressure; primarily used as transport fuel.
2. LNG (Liquefied Natural Gas) — Natural gas cooled to approximately −162°C; primarily used for long-distance ocean transport.
3. PNG (Piped Natural Gas) — Natural gas stored in high-pressure cylinders distributed in bottles to households.
How many of the above pairs are correctly matched?

Correct Answer: Only two

Pairs 1 and 2 are correctly matched. Pair 3 is incorrect — PNG is not stored in high-pressure cylinders. It is supplied continuously at low pressure directly to homes and industries through a reticulated pipeline network (City Gas Distribution).

Pair-wise Analysis

• Pair 1 — Correct (CNG): Compressed Natural Gas (CNG) is natural gas (methane) compressed to less than 1% of its volume at standard atmospheric pressure. Its primary use is as fuel for transportation (buses, cars, autos, trucks). It is the cleanest burning transport fuel in use today.
• Pair 2 — Correct (LNG): Liquefied Natural Gas (LNG) is natural gas cooled to approximately −162°C (−260°F), turning it into a clear, colourless liquid that is about 1/600th the volume of natural gas in gaseous state. It is primarily used for long-distance transport across oceans via specialized tankers, enabling trade between countries not connected by pipelines.
• Pair 3 — Incorrect (PNG): Piped Natural Gas (PNG) is supplied at low pressure through a reticulated pipeline network (City Gas Distribution or CGD network) directly to homes, industries, and commercial establishments. It provides an uninterrupted 24/7 supply — it is never stored in cylinders. This distinguishes it fundamentally from LPG (which uses cylinders) and CNG (which uses high-pressure tanks in vehicles).

Comparative Table: CNG vs LNG vs PNG

• CNG: High pressure (~200–250 bar); gaseous state; transport fuel; lighter than air.
• LNG: Very low temperature (−162°C); liquid state; oceanic shipping; regasified before use.
• PNG: Low pressure; gaseous state; continuous pipeline supply; domestic/commercial cooking and heating.