UPSC Prelims 2019 Q35: Environment & Ecology – Pollution & Waste Management
- (a) 1 and 2 only
- (b) 2, 3 and 4 only
- (c) 1 and 4 only
- (d) 1, 2, 3 and 4
Answer: (d) 1, 2, 3 and 4
Explanation
Crop/Biomass Residue Burning: Emissions
| Pollutant | Released by biomass burning? | Detail |
|---|---|---|
| 1. Carbon Monoxide (CO) | YES | Incomplete combustion of biomass releases CO - a major indoor and outdoor air pollutant. |
| 2. Methane (CH4) | YES | Smouldering biomass releases CH4 as a byproduct of incomplete combustion. |
| 3. Ozone (O3) | YES | Ground-level ozone forms as a secondary pollutant from precursors (NOx, VOCs) released by biomass burning. |
| 4. Sulphur Dioxide (SO2) | YES | Biomass contains sulphur compounds (esp. crop residues from S-containing plants); combustion emits SO2 - contributes to acid deposition. |
All four pollutants are released by burning of crop/biomass residue. Answer: (d) 1, 2, 3 and 4.
Answer: (d) 1, 2, 3 and 4.
Why each option is right or wrong
- (a) Incorrect. Ozone and SO2 are also released.
- (b) Incorrect. Carbon monoxide is a major biomass-burning pollutant.
- (c) Incorrect. Methane and secondary ozone are also released.
- (d) CORRECT. Crop residue burning releases CO, CH4, O3 (as secondary), SO2 and many other pollutants (PM2.5, PM10, NOx, VOCs, black carbon).
Key point
Crop-burning cocktail: CO, CO2, CH4, N2O, NOx, VOCs, SO2, PM2.5/PM10, black carbon -> tropospheric ozone as secondary pollutant. All the standard combustion pollutants.
Remember
Burning of crop/biomass residue releases all four pollutants - carbon monoxide, methane, ozone (as a secondary pollutant from NOx+VOCs), and sulphur dioxide - along with PM2.5, PM10, black carbon and other volatile organic compounds. This is a major contributor to North India's winter air pollution.
Common mistakes
- Assuming ozone is only from urban/vehicular sources - biomass burning also creates ozone via NOx+VOCs.
- Ignoring SO2 from biomass - crop residues do contain sulphur.
- Not linking Delhi's winter smog to Punjab/Haryana stubble burning (October-November).
Exam tip
Stubble-burning consequences: (i) Direct: CO2, CH4, N2O, NOx, SO2, PM2.5, black carbon. (ii) Secondary: tropospheric ozone. (iii) Loss of soil organic carbon and microbial biodiversity. (iv) Massive contributor to North India winter air pollution.
Sources
- Central Pollution Control Board - Air pollution from biomass burning
- IPCC AR6 - Anthropogenic emissions inventory