Which one of the following fuels causes minimum environmental pollution?
2016
Which one of the following fuels causes minimum environmental pollution?
- A.
Diesel
- B.
Petrol
- C.
Hydrogen
- D.
Coal
Show answer & explanation
Correct answer: C
Concept: The environmental impact of burning a fuel is governed by what its combustion produces. A fuel that contains carbon (and often sulphur or other impurities) necessarily releases carbon dioxide, carbon monoxide, unburnt hydrocarbons, oxides of sulphur, and particulate matter when it burns. A fuel containing no carbon at all cannot form any carbon-based combustion product, whatever its other combustion by-products.
Application: Comparing the combustion products of the four fuels offered:
Fuel | Main combustion products |
|---|---|
Diesel | Carbon dioxide, particulate matter (soot), and oxides of nitrogen |
Petrol | Carbon dioxide, carbon monoxide, and volatile hydrocarbons that form smog |
Coal | Carbon dioxide, sulphur dioxide, particulate matter/ash, and trace heavy metals |
Hydrogen | No carbon in the reaction 2H2 + O2 → 2H2O, so no CO2, soot, or SOx at all; any NOx that forms comes only from atmospheric nitrogen and depends on the specific combustion conditions, not on the fuel itself |
Cross-check: Diesel, petrol, and coal are all carbon-based fuels, so combustion of any of them necessarily releases carbon dioxide, confirmed by agencies such as the US EPA for vehicle and coal emissions. Hydrogen has no carbon at all, so its combustion cannot produce carbon dioxide, soot, or sulphur oxides under any conditions -- the only possible by-product beyond water is nitrogen oxide formed from atmospheric nitrogen, and that depends on the specific combustion setup rather than being intrinsic to the fuel. Separately, when hydrogen is used in a fuel cell rather than burnt -- an electrochemical process, not combustion -- India's Department of Science and Technology confirms the only product is water, with no combustion by-products of any kind. Diesel, petrol, and coal, by contrast, cannot avoid carbon dioxide however they are burnt. Hydrogen is therefore the fuel causing minimum environmental pollution among the options given.