Pollution & waste

Answer: (d) Waste-to-energy technologies

Pyrolysis and plasma gasification are waste-to-energy technologies: they treat waste (such as plastics and municipal solid waste) at high temperature and turn it into fuel oil or syngas that can generate power.

• ✓ (d) In pyrolysis, waste is heated (400-600°C) without oxygen to give pyrolysis oil and gas. In plasma gasification, a plasma arc above 3000°C turns waste into syngas, which can run gas engines to make electricity.
• ✗ (a) Rare earth elements are recovered from ores by mining and chemical processing, not by these thermal waste treatments.
• ✗ (b) Natural gas extraction uses drilling and hydraulic fracturing; neither term belongs there.
• ✗ (c) Hydrogen vehicles run on fuel cells or hydrogen engines; pyrolysis and gasification are not vehicle technologies.

Remember · Pyrolysis (heating waste without oxygen) and plasma gasification (waste to syngas in a plasma arc above 3000°C) are waste-to-energy routes for plastics and solid waste.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) They are considered harmful to marine ecosystems.

Microbeads are tiny plastic beads put into cleansers and toothpastes as exfoliants; they slip through water filters, end up in oceans and lakes, and threaten aquatic life.

• ✓ (a) Microbeads are a type of microplastic. They pass easily through water treatment systems into the sea, where marine animals can swallow them and toxins can collect on them, so they are a threat to marine ecosystems.
• ✗ (b) Microbeads are rinsed off the skin and the worry about them is environmental pollution; skin cancer in children is not the reason for the concern.
• ✗ (c) Plastic beads are not taken up into crop plants through their roots; this is not the reason for concern.
• ✗ (d) Microbeads are used in personal care products, not as food additives or adulterants.

Remember · Microbeads are tiny plastic exfoliant beads in cosmetics and toothpaste that escape water treatment and pollute oceans, harming aquatic life.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (d) 1, 2, 3 and 4

Why not the tempting option · UPSC's key counts ozone among the gases released due to crop-residue burning. Ozone is a secondary pollutant that forms in the air from the nitrogen oxides and volatile organic compounds in the smoke, but the question says 'due to the burning', which covers that. The doubt does not change the answer: carbon monoxide, methane and sulphur dioxide are certainly emitted, and (d) is the only option that contains all three. In the exam, settle the sure statements first and let the option grid decide the rest.

UPSC counts all four. Burning crop residue puts carbon monoxide, methane and sulphur dioxide straight into the air, and the smoke's nitrogen oxides and volatile organic compounds go on to form ground-level ozone. Since 1, 2 and 4 are certain, only option (d) can be right.

• ✓ 1. Burning rice straw releases carbon monoxide; about 7% of the carbon in the straw leaves as CO.
• ✓ 2. Methane is also released; about 0.66% of the carbon in burnt rice straw is emitted as CH4.
• ✓ 3. Ozone is not emitted as such; it forms in the air from the nitrogen oxides and volatile organic compounds in stubble smoke, so it is released into the atmosphere 'due to' the burning. In any case CO, CH4 and SO2 are certain, and (d) is the only option that contains all three.
• ✓ 4. Stubble burning emits sulphur dioxide along with carbon monoxide, nitrogen oxides, methane and fine particles.

Remember · Crop-residue burning gives CO, CO2, CH4, N2O, NOx, SO2 and particulates; the smoke's VOCs and NOx then form ground-level ozone.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (a) pesticides in agriculture

Carbofuran, methyl parathion, phorate and triazophos are toxic insecticides used on crops. They feature in the Government of India's lists of pesticides that are banned or restricted because of their harm to health and to birds, fish and bees.

• ✓ (a) All four names appear in the Ministry of Agriculture's list of banned and restricted pesticides. Methyl parathion was banned by an August 2018 order, and phorate and triazophos were barred from manufacture and import from 1 January 2019, with use to end by 31 December 2020.
• ✗ (b) Food preservatives are additives regulated under food-safety rules; none of these four is a preservative.
• ✗ (c) Fruit ripening is done with ethylene-releasing agents or, illegally, calcium carbide. These chemicals are insecticides, not ripening agents.
• ✗ (d) Moisturisers in cosmetics are humectants and emollients; these four are toxic to humans and have no cosmetic use.
• • Since then The Government's list of pesticides banned for manufacture, import and use, updated to 1 October 2022, includes methyl parathion, phorate and triazophos; carbofuran appears as a banned 50% SP formulation.

Remember · Carbofuran, methyl parathion, phorate and triazophos are hazardous agricultural insecticides, banned or being phased out in India.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (d) 1, 2 and 3

All three statements are correct, because farming is a major source of reactive nitrogen. Fertilised soils release nitrous oxide, and manure and urine from cattle and poultry give off ammonia.

• ✓ 1. When reactive nitrogen such as fertiliser reaches the soil, microbes convert part of it into nitrous oxide, an oxide of nitrogen and a greenhouse gas.
• ✓ 2. Much of the protein that cattle eat is lost in manure and urine, and this nitrogen escapes as ammonia and other nitrogenous gases.
• ✓ 3. Poultry waste is rich in nitrogen, and under aerobic conditions it can evaporate as ammonia, which is a reactive nitrogen compound.

Remember · Agriculture is a big source of reactive nitrogen: soils give nitrous oxide, while cattle and poultry manure gives ammonia.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

Statements 2 and 3 are correct. Blending hydrogen, which has no carbon, into CNG lowers carbon dioxide and hydrocarbon emissions, and India's trials and rules use a blend of about 18% hydrogen by volume, which is within one-fifth. H-CNG does not eliminate carbon monoxide and is not cheaper than plain CNG.

• ✗ 1. H-CNG is still mostly natural gas, a carbon fuel, so it can lower carbon monoxide but cannot eliminate it. Official pages describe the benefit as emissions reduction, not elimination.
• ✓ 2. Part of the fuel is carbon-free hydrogen, so less carbon is burnt per unit of energy and the blend gives lower carbon dioxide and hydrocarbon emissions; the Petroleum Ministry calls H-CNG an interim technology for emissions reduction.
• ✓ 3. The Road Transport Ministry allowed H-CNG with an 18% hydrogen mix in CNG engines, which is under one-fifth (20%) by volume; the Delhi bus trials also used 18%.
• ✗ 4. Making the blend is costly: the Petroleum Ministry notes that the high cost of producing and blending hydrogen offsets the fuel-economy savings over plain CNG, and its Secretary called commercial viability the main challenge.
• • Since then After the exam year, the Road Transport Ministry notified (GSR 585(E), 25 September 2020) H-CNG with an 18% hydrogen mix as an automotive fuel.

Remember · H-CNG is CNG blended with up to about 18% hydrogen by volume: it lowers emissions but does not remove them, and it is costlier than plain CNG.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) The Rules provide for exact and elaborate criteria for the identification of sites for landfills and waste processing facilities.

Option (c) is correct because Schedule I of the Solid Waste Management Rules, 2016 gives detailed site-selection criteria for sanitary landfills, such as minimum distances from rivers, ponds, highways, habitations and airports. The other three options misstate the rules.

• ✗ (a) Rule 4 asks every waste generator to segregate waste into three streams: bio-degradable, non bio-degradable and domestic hazardous waste. There is no five-way split.
• ✗ (b) Rule 2 applies the Rules far more widely than 'only' urban local bodies, notified towns and industrial townships. It also covers census towns, outgrowths of urban agglomerations, railways, airports, ports, defence establishments, SEZs and more.
• ✓ (c) Schedule I lays down criteria such as a landfill 100 metres from a river, 200 metres from a pond, highways, habitations, public parks and water supply wells, and 20 km from airports.
• ✗ (d) The Rules contain no ban on moving waste between districts. They say the State Pollution Control Board regulates inter-State movement of waste.
• • Since then The Solid Waste Management Rules, 2016 have since been superseded by the Solid Waste Management Rules, 2026, notified in January 2026 and in force from 1 April 2026. The new Rules make four-stream segregation (wet, dry, sanitary and special care waste) mandatory (PIB).

Remember · Under the 2016 Rules, waste is segregated into three streams and Schedule I fixes landfill siting distances; the 2026 Rules replaced these with four-stream segregation.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) The e-Waste (Management and Handling) Rules, 2011

India's e-Waste (Management and Handling) Rules, 2011 introduced extended producer responsibility (EPR), which makes the producer of electrical and electronic equipment answerable for the product until its safe disposal after use. The rules were notified in May 2011 and came into force on 1 May 2012.

• ✓ (c) The official guidelines on these rules say they place the main responsibility for e-waste on producers of electrical and electronic equipment by introducing the concept of extended producer responsibility.
• ✗ (a) The 1998 bio-medical waste rules pre-date the e-waste rules and are not the ones credited with bringing in EPR.
• ✗ (b) The 1999 recycled plastics rules likewise pre-date the 2011 e-waste rules, which are the ones that introduced EPR in India.
• ✗ (d) The Food Safety and Standards Regulations, 2011 deal with food safety, not with waste, so producer responsibility for end-of-life products is not their feature.

Remember · EPR = the producer stays responsible for a product until its safe disposal. In India it came with the e-Waste Rules, 2011 (in force 1 May 2012).

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error