UPSC Prelims 2019 Q43: Science & Technology – Energy & Environment

UPSC Prelims 2019, General Studies Paper I · Science & Technology

In the context of proposals to the use of hydrogen - enriched CNG (H - CNG) as fuel for buses in public transport, consider the following statements: 1. The main advantage of the use of H - CNG is the elimination of carbon monoxide emissions. 2. H - CNG as fuel reduces carbon dioxide and hydrocarbon emissions. 3. Hydrogen up to one - fifth by volume can be blended with CNG as fuel for buses. 4. H - CNG makes the fuel less expensive than CNG. Which of the statements given above is/are correct?

(a) 1 only
(b) 2 and 3 only
(c) 4 only
(d) 1, 2, 3 and 4

Answer: (b) 2 and 3 only

Explanation

Hydrogen-Enriched CNG (H-CNG) for Buses

Statement	Claim	Verdict	Detail
1	H-CNG eliminates CO emissions	FALSE	H-CNG REDUCES CO emissions substantially but does NOT eliminate them - hydrocarbons still combust to produce some CO.
2	Reduces CO2 and hydrocarbon emissions	TRUE	Hydrogen combustion produces water (no C); adding H to CNG reduces both CO2 and unburned HC.
3	Up to one-fifth (~18-20%) by volume H2 blended	TRUE	Standard blend is 18% H2 in CNG - beyond this, engine modifications needed.
4	H-CNG is less expensive than CNG	FALSE	H-CNG is more expensive due to hydrogen production costs (electrolysis or SMR).

Only statements 2 and 3 are correct. Answer: (b) 2 and 3 only.

Answer: (b) 2 and 3 only.

Why each option is right or wrong

(a) Incorrect. Statement 1 is wrong (reduces but doesn't eliminate CO); statement 2 is correct.
(b) CORRECT. Statements 2 (reduces CO2/HC) and 3 (up to 1/5 H2 blend) are correct. Statement 1 (eliminate CO) and 4 (cheaper) are wrong.
(c) Incorrect. Statement 4 is wrong - H-CNG is more expensive.
(d) Incorrect. Statements 1 and 4 are false.

Key point

H-CNG (18% H2 in CNG): Reduces CO2/HC/CO emissions (does NOT eliminate CO). Costlier than CNG. Delhi trialed H-CNG buses via IOCL/IIT Delhi.

Remember

Only statements 2 and 3 are correct. H-CNG reduces (but does not eliminate) CO emissions; it reduces CO2 and hydrocarbon emissions; up to about one-fifth (18-20%) hydrogen can be blended with CNG without engine modification. However, H-CNG is MORE expensive than pure CNG, not less.

Common mistakes

Assuming any hydrogen fuel eliminates all carbon emissions - H-CNG still has 80% CNG, so C emissions persist.
Confusing H-CNG (blended) with pure hydrogen fuel cell buses - different technology.
Not knowing Delhi's DTC ran H-CNG bus trials in 2020-21 with IOCL as fuel supplier.

Exam tip

Hydrogen mobility spectrum: (i) H-CNG = 18% H2 in CNG (bridge tech). (ii) H2-ICE = pure hydrogen in internal combustion engine. (iii) Fuel Cell EV (FCEV) = hydrogen electrochemically produces electricity (Toyota Mirai, Hyundai Nexo). India's National Green Hydrogen Mission (2023) aims to make India a hydrogen hub.

Sources

Ministry of Petroleum & Natural Gas - H-CNG bus trials, Delhi
IIT Delhi & IOCL - H-CNG technical documentation

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