BEE Exam Prep › Paper-1 › Chapter 10

BEE Paper-1 — Chapter 10: Energy Efficiency & Climate Change

123 questions — 54 objective (1 mark), 56 short (5 marks), 13 long (10 marks). Every answer is checked against the 2014 BEE guidebook and carries its book section reference plus an explanation.
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Objective questions (1 mark) — 54

📖 §10.4 Ozone layer depletion

1. The depletion of Ozone layer is caused mainly by _________

  1. nitrous oxide
  2. carbon dioxide
  3. choloroflourocarbons
  4. methane gas
Answer: C) choloroflourocarbons
Confirmed vs Book-1 §10.4 — The book states the main chemical responsible for ozone depletion is chlorofluorocarbons (CFCs), used in refrigerators and air conditioners. UV breaks the C–Cl bond and the released chlorine atom destroys ozone; one Cl atom can destroy 10,000–100,000 ozone molecules. N2O, CO2 and CH4 are greenhouse gases, not the main ozone-depleting substances. (Book EOC Objective Q8.)
Source: 2013
📖 §10.5 Carbon sequestration

2. The process of capturing CO2 from point sources and storing them is called

  1. carbon capture and sequestration
  2. carbon sink
  3. carbon capture
  4. carbon absorption
Answer: A) carbon capture and sequestration
Confirmed vs Book-1 §10.5 — Carbon sequestration is defined as removing CO2 from large point sources (power plants, refineries, industrial processes) and storing it in geologic formations such as depleted oil/gas reservoirs, deep coal seams or saline reservoirs. A 'carbon sink' (ocean, biomass) merely absorbs CO2 naturally; 'carbon capture' alone omits the storage step. (Book EOC Objective Q10 prints the answer as 'carbon sequestration'.)
Source: 2012
📖 §10.5 Greenhouse gases

3. Which of the following is not a greenhouse gas?

  1. Water Vapour
  2. SO2
  3. CO2
  4. CH4
Answer: B) SO2
Confirmed vs Book-1 §10.5 — The greenhouse gases named in the book are water vapour, CO2, methane, nitrous oxide, ozone, CFCs/HFCs, PFCs and SF6. SO2 is an acid-rain / air-pollution gas (§10.3), not a greenhouse gas.
Source: Sep 2021
📖 §10.1 Energy and environment

4. Which one of the following is not an example of air pollution from boilers and furnaces?

  1. sulphur dioxide (SO2)
  2. chloro-fluro carbons (CFC)
  3. nitrous oxide (NOX)
  4. carbon monoxide (CO)
Answer: B) chloro-fluro carbons (CFC)
Confirmed vs Book-1 §10.1 — The principal emissions from fuel combustion in boilers and furnaces are CO2, particulate matter, SOx, NOx, hydrocarbons and CO. CFCs are man-made refrigerants/propellants (§10.5) and are not a product of combustion.
Source: Apr 2010
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

5. Select the one with the highest Global warming potential among the following gases

  1. carbon dioxide
  2. methane
  3. sulphur hexafluoride
  4. nitrous oxide
Answer: C) sulphur hexafluoride
Confirmed vs Book-1 §10.5 — The book states 'Sulfur hexafluoride is the most potent greenhouse gas'; Table 10.1 gives GWP: CO2 = 1, CH4 = 23, N2O = 300, SF6 = 22,000. SF6 therefore has the highest GWP. (Note: PFC has the LONGEST life, 50,000 yrs, but a lower GWP of 5700.)
Source: Apr 2010
📖 §10.10 Kyoto mechanisms — CDM

6. CDM stands for

  1. carbon depletion mechanism
  2. clean development mechanism
  3. clear development mechanism
  4. carbon depletion machinery
Answer: B) clean development mechanism
Confirmed vs Book-1 §10.10 — CDM = Clean Development Mechanism, one of the three Kyoto flexibility mechanisms (with Emissions Trading and Joint Implementation). It lets an Annex-I country implement an emission-reduction project in a developing country and earn CERs.
Source: Apr 2010
📖 §10.11 CDM — host country approval (DNA)

7. Which is the Designated National Agency (DNA) of India for CDM?

  1. Ministry of Environment and Forests (MoEF)
  2. Central Pollution Control Board (CPCB)
  3. State Designated Agency (SDA)
  4. Bureau of Energy Efficiency (BEE)
Answer: A) Ministry of Environment and Forests (MoEF)
Confirmed vs Book-1 §10.11 — The book states 'National CDM Authority in India is Ministry of Environment & Forest (MoE&F)'. The DNA evaluates and approves CDM projects against the host country's sustainable-development criteria and is the point of contact. BEE and CPCB have no CDM approval role.
Source: Apr 2010
📖 §10.1 Energy and environment / §10.5 CO2 from fuels

8. Changing from furnace oil firing to natural gas firing will result in

  1. increased CO2 emissions
  2. decreased SO2 emissions
  3. decreased % of wet flue gas loss
  4. none of the above
Answer: B) decreased SO2 emissions
Confirmed vs Book-1 §10.1 — SOx emissions arise mainly from the sulphur content of oil and coal; natural gas is essentially sulphur-free, so switching from furnace oil to natural gas decreases SO2. CO2 also falls (§10.5: 'for the same amount of heat released, natural gas emits the least CO2'), and wet flue gas loss actually increases with gas firing because of its higher hydrogen content.
Source: Apr 2010
📖 §10.4 Ozone layer depletion

9. The Ozone layer is found in

  1. stratosphere
  2. atmosphere
  3. ionosphere
  4. troposphere
Answer: A) stratosphere
Confirmed vs Book-1 §10.4 — 'Ozone layer is a thin layer of ozone (O3) present in stratosphere which extends from 10–50 km from the earth.' The troposphere is the lower layer where weather occurs and holds 90% of atmospheric molecules.
Source: Apr 2010
📖 §10.4 Chemistry of ozone depletion

10. Ozone depletion process is due to

  1. carbon dioxide
  2. UV light breaking the ozone
  3. nitrogen
  4. chlorine atoms destroying ozone molecules
Answer: D) chlorine atoms destroying ozone molecules
Confirmed vs Book-1 §10.4 — 'It is the chlorine and bromine atom that actually destroys ozone, not the intact ODS molecule.' UV radiation only breaks the CFC molecule apart to release the chlorine atom; the chlorine then strips an oxygen from O3, forming O2 and ClO, and is regenerated to repeat the cycle.
Source: Apr 2010
📖 §10.11 Small-scale CDM (fast track)

11. Fast track approval procedures for CDM projects are applicable to renewable energy projects with output capacity up to

  1. 5 MW
  2. 10 MW
  3. 15 MW
  4. 20 MW
Answer: C) 15 MW
Confirmed vs Book-1 §10.11 — Small-scale project Type I = renewable energy projects with a capacity of up to 15 MW; Type II = energy-efficiency projects saving up to 15 GWh/year (54 TJ); Type III = other projects emitting less than 15 kt CO2/year.
Source: Apr 2010
📖 §10.1 Energy and environment

12. Which one of the following is not an example of air pollution from furnace oil fired boilers and furnaces?

  1. sulphur dioxide (SO2)
  2. chloro-fluro carbons (CFC)
  3. nitrous oxide (NOX)
  4. carbon monoxide (CO)
Answer: B) chloro-fluro carbons (CFC)
Confirmed vs Book-1 §10.1 — Furnace-oil fired boilers emit SO2 (from fuel sulphur), NOx (from fuel and combustion air), CO (incomplete combustion) and CO2/particulates. CFCs are man-made refrigerants and propellants (§10.5) and are not combustion products.
Source: Nov 2009
📖 §10.5 CO2 avoided = energy saved × emission factor

13. How much carbon emission will be reduced per year by replacing a 60 W incandescent lamp with a 15 W CFL lamp, if emission per unit is 1 kg CO2 per kWh and annual burning is 3000 hours?

  1. 45 ton
  2. 3 ton
  3. 0.135 ton
  4. 183 ton
Answer: C) 0.135 ton
Confirmed vs Book-1 §10.5 — Power saved = 60 − 15 = 45 W = 0.045 kW. Energy saved = 0.045 × 3000 h = 135 kWh/yr. CO2 avoided = 135 kWh × 1 kg CO2/kWh = 135 kg = 0.135 tonne per year.
Source: Nov 2009
📖 §10.11 CDM — host country approval (DNA)

14. The Designated National Agency (DNA) of India for Clean Development Mechanism (CDM) is

  1. Ministry of Environment and Forests (MoEF)
  2. Bureau of Energy Efficiency (BEE)
  3. Central Electricity Authority (CEA)
  4. Central Electricity Regulatory Commission (CERC)
Answer: A) Ministry of Environment and Forests (MoEF)
Confirmed vs Book-1 §10.11 — The book states the National CDM Authority (DNA) in India is the Ministry of Environment & Forest (MoE&F). The DNA reviews and approves the PDD and confirms the project meets the host country's sustainable-development criteria.
Source: Nov 2009
📖 §10.10 Kyoto mechanisms — CDM vs JI

15. The process by which Annex 1 countries can invest in the GHG mitigation projects in developing countries is called:

  1. green trading
  2. clean development mechanism
  3. conference of parties
  4. certified emission reduction
Answer: B) clean development mechanism
Confirmed vs Book-1 §10.10 — CDM is the mechanism between one country that HAS a commitment (Annex I) and a country that does NOT (developing, non-Annex I); it earns CERs. Investment between two Annex-I countries is Joint Implementation (JI), which earns ERUs.
Source: Nov 2009
📖 §10.5 Greenhouse gases

16. Which gas has the least impact on global warming?

  1. carbon dioxide
  2. methane
  3. ozone
  4. carbon monoxide
Answer: D) carbon monoxide
Confirmed vs Book-1 §10.5 — CO2, methane and ground-level ozone are all listed by the book as greenhouse gases that absorb infrared radiation. Carbon monoxide is treated as an air pollutant from incomplete combustion (§10.1) and is not in the book's list of greenhouse gases, so it has the least global-warming impact.
Source: Nov 2009
📖 §10.10 CDM — CERs

17. One Certified Emission Reduction (CER) in equivalent of CO2 emission is

  1. 1 ton of CO2
  2. 1 kg of CO2
  3. 10 kg of CO2
  4. 10 ton of CO2
Answer: A) 1 ton of CO2
Confirmed vs Book-1 §10.10 — CDM projects earn 'saleable certified emission reduction (CER) credits, each equivalent to one tonne of CO2'. The same one-tonne unit applies to an ERU under Joint Implementation.
Source: Nov 2009
📖 §10.5 CO2 avoided = energy saved × emission factor

18. Assume CO2 equivalent emissions by the use of a 40 W fluorescent lamp are of the order of 60 g/hr. If it is replaced by a 20 W LED lamp then the equivalent CO2 emissions will be

  1. nil, as LED does not emit CO2
  2. 30 g/hr
  3. 20 g/hr
  4. 1200 g/hr
Answer: B) 30 g/hr
Confirmed vs Book-1 §10.5 — CO2 emission from lighting is proportional to the wattage drawn. 40 W → 60 g/hr, so per watt = 1.5 g/hr. A 20 W LED therefore emits 20 × 1.5 = 30 g/hr. LEDs do emit indirect CO2, because the electricity they use is generated from fossil fuel.
Source: 2019
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

19. Which of the following has highest Global Warming Potential?

  1. SF6
  2. CO2
  3. CH4
  4. N2O
Answer: A) SF6
Confirmed vs Book-1 §10.5 — 'Sulfur hexafluoride is the most potent greenhouse gas.' Table 10.1: SF6 GWP = 22,000 against CO2 = 1, CH4 = 23 and N2O = 300.
Source: 2019
📖 §10.5 Greenhouse gases / §10.6 mitigation

20. In a boiler, substitution of coal with rice husk will definitely lead to__________.

  1. energy conservation
  2. energy efficiency
  3. both energy conservation and energy efficiency
  4. GHG reduction
Answer: D) GHG reduction
Confirmed vs Book-1 §10.5 — Rice husk is biomass; the CO2 released on burning it was recently absorbed from the atmosphere, so substituting coal with rice husk definitely cuts net greenhouse-gas emissions. It does not by itself guarantee lower energy consumption (conservation) or higher boiler efficiency — biomass has a lower GCV than coal.
Source: 2019
📖 §10.4 & §10.6 — ozone hole vs global warming

21. Global warming will not result in

  1. melting of the ice caps
  2. increasing sea levels
  3. increasing the size of the hole in the ozone layer
  4. unpredictable climate patterns
Answer: C) increasing the size of the hole in the ozone layer
Confirmed vs Book-1 §10.4/§10.6 — The book lists the impacts of global warming as rising sea levels, snow/ice melting, altered rainfall, extreme weather, heat waves, loss of biodiversity, disease and water/food shortages. Ozone depletion is a separate problem caused by CFCs (Montreal Protocol), not by global warming. (Book EOC Objective Q2.)
Source: 2012
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

22. Which of the following GHGs has the longest atmospheric life time?

  1. CO2
  2. CFC
  3. Sulfur Hexafluoride (SF6)
  4. perfluorocarbon (PFC)
Answer: D) perfluorocarbon (PFC)
Confirmed vs Book-1 §10.5 — 'Perfluorcarbons is also considered as an important greenhouse gas as it has a long atmospheric life, more than several thousand years.' Table 10.1 gives PFC lifetime = 50,000 years, versus SF6 3200, N2O 114, CO2 5–200 and CFC 5–100 years. (Longest life = PFC; highest GWP = SF6.)
Source: 2017
📖 §10.5 CO2 avoided = energy saved × emission factor

23. Assume CO2 equivalent emissions by the use of a 60 W incandescent lamp are of the order of 60 g/hr. If it is replaced by a 5 W LED lamp then the equivalent CO2 emissions will be

  1. nil
  2. 5 g/hr
  3. 12 g/hr
  4. 300 g/hr
Answer: B) 5 g/hr
Confirmed vs Book-1 §10.5 — Emissions scale with the connected load: 60 W → 60 g/hr means 1 g/hr per watt. A 5 W LED therefore causes 5 g/hr of CO2 — a 55 g/hr avoidance, but not zero, since the electricity comes from fossil generation.
Source: 2017
📖 §10.5 Man-made CO2 emissions (fuel carbon content)

24. Which energy source releases the most climate-altering carbon pollution per kg?

  1. Oil
  2. Coal
  3. Rice husk
  4. Bagasse
Answer: A) Oil
Confirmed vs Book-1 §10.5 — CO2 released per kg of fuel = carbon fraction × 44/12. Oil has the highest carbon content per kg (~85%, giving ~3.1 kg CO2/kg) compared with coal (the book uses 1.53 kg CO2/kg coal in EOC S-1), while rice husk and bagasse are biomass and treated as carbon-neutral. Note the stem asks per KG of fuel; per unit of HEAT, coal is the dirtiest. Options repaired: stray leading '.' removed.
Source: 2016
📖 §10.5 The greenhouse effect

25. Greenhouse effect is caused by natural affects and anthropogenic effects. If there is no natural greenhouse effect, the Earth's average surface temperature would be around __________°C.

  1. 0
  2. 32
  3. 14
  4. - 18
Answer: D) - 18
Confirmed vs Book-1 §10.5 — 'Without naturally occurring greenhouse gases such as water vapour, carbon dioxide, methane and nitrous oxide, the earth's average surface temperature would be a cold −18°C rather than the tolerable 15°C.' The natural greenhouse effect is what makes life on Earth possible.
Source: 2016
📖 §10.2 Global environmental issues

26. Which of the following is not an environmental issue of global significance?

  1. ozone layer depletion
  2. global Warning
  3. loss of Biodiversity
  4. suspended particulate Matter
Answer: D) suspended particulate Matter
Confirmed vs Book-1 §10.2 — The book lists exactly four issues of global significance: acid rain, ozone layer depletion, global warming & climatic change, and loss of biodiversity. Suspended Particulate Matter is a LOCAL air-quality problem confined to the area around the source, so it is not global. (Book EOC Objective Q6.)
Source: 2013
📖 §10.4 Ozone layer depletion

27. The ozone layer in the stratosphere acts as an efficient filter for ____

  1. UV- B rays
  2. X-rays
  3. Gamma rays
  4. beta rays
Answer: A) UV- B rays
Confirmed vs Book-1 §10.4 — 'The ozone layer is highly beneficial to life on earth as it blocks the sun's Ultraviolet radiations (UV-B) from reaching the earth.' Depletion increases UV-B at the surface, causing skin cancer, eye disease and ecosystem damage.
Source: 2013
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

28. Which among the following has the lowest Global Warming Potential?

  1. Perflurocarbon
  2. chloroflurocarbons
  3. methane
  4. nitrous oxide
Answer: C) methane
Confirmed vs Book-1 §10.5 — Table 10.1 GWPs: methane 23, nitrous oxide 300, PFC 5700, CFCs 4000–8000. Methane therefore has the lowest GWP of the four listed (CO2 = 1 is the reference and is not an option). (Book EOC Objective Q7.)
Source: 2013
📖 §10.11 CDM — Bachat Lamp Yojana (CDM-based scheme)

29. Which of the following statements regarding BLY (Bachat Lamp Yojana) are correct? i) BLY aims at large scale replacement of all fluorescent lamps of poor lumen intensity with CFL of high lumen intensity; ii) CDM is used as a tool to recover the market price difference between the lower cost replaced incandescent lamps of 60 W and the higher cost CFLs of 11 W; iii) BLY involves public-private partnership and DISCOM partnerships; iv) DSM is used as a tool to recover the market price difference between the lower cost replaced incandescent lamps of 60 W and the higher cost CFLs of 11 W

  1. i & ii
  2. i & iii
  3. ii & iii
  4. i & iv
Answer: C) ii & iii
Confirmed vs Book-1 §10.11 — BLY replaces INCANDESCENT lamps (60 W) with CFLs (11–15 W), so statement (i), which says fluorescent lamps, is wrong. The price gap between the cheap incandescent lamp and the costlier CFL is bridged by CER revenue under the CDM — not by DSM — so (ii) is right and (iv) wrong; BLY is run as a public–private partnership with DISCOMs, so (iii) is right. Answer = ii & iii. (Question stem/options repaired: the four roman-numeral statements had collapsed into option 'a'; BLY itself is named only in the chapter's learning objectives, its mechanism is the CDM/CER route of §10.11.)
Source: 2012
📖 §10.4 Ozone layer depletion

30. The ozone layer found in the stratosphere:

  1. protects against the sun’s harmful UV rays
  2. can react with atmospheric pollutants to form smog
  3. is toxic to plants
  4. is capable of disintegrating fabric and rubber on earth
Answer: A) protects against the sun’s harmful UV rays
Confirmed vs Book-1 §10.4 — Stratospheric ozone blocks the sun's harmful UV-B radiation. Smog formation, plant toxicity and material damage are properties of GROUND-LEVEL ozone (§10.5), which is a pollutant and a greenhouse gas — the classic 'good ozone up high, bad ozone nearby' distinction. (Book EOC Objective Q3.)
Source: 2012
📖 §10.5 Carbon dioxide as the principal GHG

31. The main constituent of greenhouse gases (GHG) in atmosphere is

  1. CO2
  2. SOx
  3. nitrogen
  4. water vapor
Answer: A) CO2
Confirmed vs Book-1 §10.5 — 'Carbon dioxide is the most important of the greenhouse gases because of its abundance in the atmosphere.' It contributes about 60% of the enhanced greenhouse effect at ~397 ppm (Mauna Loa, Nov 2014). Nitrogen and SOx are not greenhouse gases; water vapour is a GHG but its amount is not changing directly because of human activity. (Book EOC Objective Q4.)
Source: 2012
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

32. The Global Warming Potential (GWP) of nitrous oxide (N2O) is

  1. 1
  2. 23
  3. 300
  4. 5700
Answer: C) 300
Confirmed vs Book-1 §10.5 — Table 10.1 gives nitrous oxide GWP = 300 with an atmospheric lifetime of 114 years (baseline 275 ppb, current 326 ppb). GWP 1 = CO2, 23 = methane, 5700 = PFC. (Book EOC Objective Q5.)
Source: 2012
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

33. The Global Warming Potential (GWP) of sulfur hexafluoride is

  1. 1
  2. 23
  3. 300
  4. 22,000
Answer: D) 22,000
Confirmed vs Book-1 §10.5 — Table 10.1 gives SF6 GWP = 22,000 with a lifetime of 3200 years; the book also calls it 'the most potent greenhouse gas'. GWP 1 = CO2, 23 = CH4, 300 = N2O. (Book EOC Objective Q1.)
Source: Guidebook
📖 §10.10 Kyoto Protocol — common but differentiated responsibilities

34. Which of the following statements regarding responsibility of climate change mitigation is correct?

  1. industrialized countries bear the sole responsibility because they are responsible for most of the GHG emitted to date due to their economic growth
  2. developing countries bear the sole responsibility as they will be responsible for most of the GHG emission increase in the future due to their population growth
  3. both industrialized and developing countries share the equal responsibility as a member of the international community
  4. both industrialized and developing countries share common responsibility but taking into account the respective capabilities towards mitigation
Answer: D) both industrialized and developing countries share common responsibility but taking into account the respective capabilities towards mitigation
Confirmed vs Book-1 §10.10 — 'Recognizing that developed countries are principally responsible for the current high levels of GHG emissions... the Protocol places a heavier responsibility on developed nations under the principle of common but differentiated responsibilities.' Responsibility is therefore shared but differentiated by capability — neither sole nor equal. (Book EOC Objective Q9.)
Source: Guidebook
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

35. Which of the following gas has high Global warming potential?

  1. Carbon dioxide
  2. Ozone
  3. Methane
  4. Nitrous oxide
Answer: D) Nitrous oxide
Confirmed vs Book-1 §10.5 — Of the four gases listed, Table 10.1 gives nitrous oxide the highest GWP at 300, against methane 23, CO2 1 and ozone (days/weeks lifetime, no GWP assigned in the table).
Source: Mar 2023
📖 §10.3 Acid rain

36. Acid rain is caused by the release of which of the following components:

  1. SOx and NOx
  2. SOx and CO2
  3. CO2 and NOx
  4. Ozone
Answer: A) SOx and NOx
Confirmed vs Book-1 §10.3 — 'Acid rain is caused by release of sulphur oxides and nitrogen oxides from combustion of fossil fuels, which then mix with water vapour in atmosphere to form sulphuric acids and nitric acids respectively.' It is a trans-boundary issue and deposits both wet (rain, snow) and dry.
Source: Jul 2022
📖 §10.4 Ozone layer depletion

37. Ozone depletion is mainly due to:

  1. Oxygen
  2. Methane
  3. Chlorofluorocarbons
  4. Carbon dioxide
Answer: C) Chlorofluorocarbons
Confirmed vs Book-1 §10.4 — The main chemical responsible is chlorofluorocarbons (CFCs) from refrigerators and air conditioners; UV frees a chlorine atom that destroys ozone catalytically. A single CFC molecule can destroy up to 100,000 ozone molecules.
Source: Sep 2025
📖 §10.5 Carbon sequestration

38. Carbon capture from point sources and storage is called:

  1. Carbon sequestration
  2. Carbon sink
  3. Carbon capture
  4. Carbon adsorption
Answer: A) Carbon sequestration
Confirmed vs Book-1 §10.5 — Carbon sequestration is the removal of CO2 from large point sources (power plants, refineries, industry) and its storage in geologic formations — depleted oil and gas reservoirs, deep coal seams or saline reservoirs. A carbon sink is a natural absorber (oceans, biomass).
Source: Sep 2025
📖 §10.13 Sustainable development

39. Which of the following are basic objectives of sustainable development?

  1. Economic security and prosperity
  2. Social development and advancement
  3. Environmental sustainability
  4. All of the above
Answer: D) All of the above
Confirmed vs Book-1 §10.13 — 'Sustainable development encompasses three basic and inter-related objectives: economic security and prosperity; social development and advancement; environmental sustainability.' All three are therefore correct. The Brundtland Commission report 'Our Common Future' (1987) gives the definition.
Source: Sep 2025
📖 §10.5 CO2 avoided = energy saved × emission factor

40. Calculate the reduction in CO2 emissions if energy efficiency measures save 1000 kWh, assuming 0.8 kg CO2/kWh.

  1. 800 kg
  2. 1250 kg
  3. 625 kg
  4. 1000 kg
Answer: A) 800 kg
Confirmed vs Book-1 §10.5 — CO2 avoided = energy saved × emission factor = 1000 kWh × 0.8 kg CO2/kWh = 800 kg. This is the standard energy-efficiency-to-emissions conversion used in CDM baseline calculations.
Source: Sep 2024
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

41. Which of the following GHG has the longest atmospheric life time?

  1. Carbon dioxide (CO2)
  2. Sulphur Hexafluoride (SF6)
  3. Chlorofluorocarbons (CFC)
  4. Perfluorocarbons (PFC)
Answer: D) Perfluorocarbons (PFC)
Confirmed vs Book-1 §10.5 — Table 10.1 lifetimes: PFC 50,000 years (the book: 'more than several thousand years'), SF6 3200 years, CFC 5–100 years, CO2 5–200 years. Longest atmospheric life = PFC; do not confuse this with highest GWP = SF6.
Source: Sep 2024
📖 §10.4 Ozone layer depletion

42. The Ozone layer in stratosphere act as an efficient filter for

  1. UV-B Rays
  2. UV-C Rays
  3. X-Ray
  4. Gamma Rays
Answer: A) UV-B Rays
Confirmed vs Book-1 §10.4 — The stratospheric ozone layer (10–50 km up) blocks the sun's UV-B radiation from reaching the earth. Its depletion raises UV-B at the surface, causing skin cancer, eye disease, reduced crop/plankton productivity and material damage.
Source: Sep 2024
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

43. Among the Kyoto greenhouse gases, which has the HIGHEST Global Warming Potential (GWP)?

  1. Methane (CH4)
  2. Nitrous oxide (N2O)
  3. Carbon dioxide (CO2)
  4. Sulphur hexafluoride (SF6)
Answer: D) Sulphur hexafluoride (SF6)
Confirmed vs Book-1 §10.5 — Table 10.1 GWP values: CO₂ = 1, CH₄ = 23, N₂O = 300, CFCs & related 4000–8000, PFC 5700, SF₆ = 22,000. SF₆ is the highest, and the text calls it ‘the most potent greenhouse gas’ (used in switchgear insulation, magnesium & semiconductor industry). Exam trap: highest GWP ≠ longest life — PFCs live longest (50,000 yr) against SF₆’s 3,200 yr.
Source: AI practice
📖 §10.5 Greenhouse gases & GWP (Table 10.1)

44. What is the Global Warming Potential (GWP) of nitrous oxide (N2O)?

  1. 1
  2. 23
  3. 300
  4. 22,000
Answer: C) 300
Confirmed vs Book-1 §10.5 — Table 10.1 row for nitrous oxide: baseline 275 ppb, current 326 ppb, GWP = 300, lifetime 114 years. Learn the ladder in order: CO₂ 1 → CH₄ 23 → N₂O 300 → PFC 5700 → SF₆ 22,000. Chapter-end objective Q.5 asks exactly this. N₂O sources: nitrogen fertiliser, manure, biomass and fossil-fuel combustion, nylon manufacture, soil bacteria disturbed by ploughing, catalytic converters.
Source: AI practice
📖 §10.10 The Kyoto Protocol — Targets (the six gases)

45. The six greenhouse gases covered under the Kyoto Protocol are:

  1. CO2, CH4, N2O, HFCs, PFCs, SF6
  2. CO2, CO, SO2, NOx, O3, CFC
  3. CO2, CH4, O3, CFC, SO2, NOx
  4. CO2, water vapour, CH4, N2O, O3, SF6
Answer: A) CO2, CH4, N2O, HFCs, PFCs, SF6
Confirmed vs Book-1 §10.10 — the Kyoto targets cover six gases: CO₂, CH₄, N₂O, HFCs, PFCs and SF₆. CFCs are deliberately NOT in the list: they are phased out under the Montreal Protocol (ozone), which this 2014 guidebook prints as signed in 1974 — write 1974 in the exam. Montreal = ozone, Kyoto = climate.
Source: AI practice
📖 §10.5 Greenhouse gases — Carbon dioxide

46. The main greenhouse gas constituent (largest contributor to the enhanced greenhouse effect) from human activity is:

  1. Carbon dioxide (CO2)
  2. Sulphur hexafluoride (SF6)
  3. Ozone (O3)
  4. Nitrous oxide (N2O)
Answer: A) Carbon dioxide (CO2)
Confirmed vs Book-1 §10.5 — ‘Carbon dioxide is the most important of the greenhouse gases because of its abundance in the atmosphere’; the rise in CO₂ has contributed about 60% of the enhanced greenhouse effect, at 397 ppm (Mauna Loa, Nov 2014) with a lifetime over 100 years. Chapter-end Q.4 has the same answer: water vapour is a greenhouse gas but its amount is not changed directly by human activity, so CO₂ is the main GHG constituent attributable to man. SF₆ is the most POTENT, not the main one.
Source: AI practice
📖 §10.4 Ozone layer depletion

47. Depletion of the ozone layer is caused mainly by:

  1. Carbon dioxide
  2. Methane
  3. Chlorofluorocarbons (CFCs)
  4. Nitrogen
Answer: C) Chlorofluorocarbons (CFCs)
Confirmed vs Book-1 §10.4 — ‘The main chemical responsible for the problem is identified as Chloro fluro carbons (CFCs) which were used in refrigerator and air conditioners.’ UV breaks the C–Cl bond and it is the free Cl (or Br) ATOM, not the intact molecule, that destroys ozone — one Cl atom destroys 10,000 to 100,000 O₃ molecules. Counter-measure = the Montreal Protocol. NOTE: this 2014 guidebook prints ‘signed at Montreal Protocol in 1974’ — write 1974 in the exam, even though the real-world date is 1987.
Source: AI practice
📖 §10.4 Ozone layer depletion — what the ozone layer is

48. The ozone layer lies in which atmospheric region and what does it protect us from?

  1. Troposphere; harmful infra-red rays
  2. Stratosphere; the sun's harmful UV (UV-B) radiation
  3. Mesosphere; cosmic rays
  4. Troposphere; acid rain
Answer: B) Stratosphere; the sun's harmful UV (UV-B) radiation
Confirmed vs Book-1 §10.4 — ‘Ozone layer is a thin layer of ozone (O₃) present in stratosphere which extends from 10-50 km from the earth… it blocks the sun’s Ultraviolet radiations (UV-B) from reaching the earth.’ Linked chapter-end Q.2: global warming will NOT increase the size of the ozone hole — ozone depletion and global warming are two separate problems. Ground-level (tropospheric) ozone is instead a greenhouse gas.
Source: AI practice
📖 §10.5 Carbon sequestration

49. Capturing CO2 from large point sources such as power plants and storing it in geologic formations is known as:

  1. Carbon sequestration
  2. Carbon trading
  3. Carbon footprinting
  4. Carbon neutrality
Answer: A) Carbon sequestration
Confirmed vs Book-1 §10.5 — ‘Carbon sequestration is the term given to the process of removing CO₂ from large point sources such as power plant, oil refineries, industrial process… then stored in geologic formations such as depleted oil and gas reservoirs, deep coal seams or saline reservoirs.’ Chapter-end Q.10 uses the same wording. Do not confuse with a carbon SINK (natural absorber: oceans hold ~50× the atmosphere’s carbon, terrestrial biomass ~3×) or with carbon TRADING (the market mechanism under Kyoto).
Source: AI practice
📖 §10.5 Carbon dioxide — fuel-carbon to CO₂ stoichiometry (see also Ch-10 Short Q S-1)

50. Burning a fuel that contains 50 kg of carbon produces approximately how much CO2? (1 kg C → 3.67 kg CO2)

  1. 13.6 kg
  2. 50 kg
  3. 183.5 kg
  4. 600 kg
Answer: C) 183.5 kg
Confirmed vs Book-1 §10.5 — CO₂ comes from oxidation of the carbon in the fuel, so mass of CO₂ = mass of C × (44/12). Working: 44/12 = 3.67 kg CO₂ per kg C; 50 kg C × 3.67 = 183.5 kg CO₂. Distractor (a) 13.6 kg is 50 ÷ 3.67 (the reverse operation); (d) 600 kg would need a factor of 12.
Source: AI practice
📖 §10.5 / Ch-10 Short Q S-1 — CO₂ avoided from fuel saved × emission factor

51. An efficiency measure saves 2000 kg of coal. If the emission factor is 1.5 kg CO2 per kg of coal, the CO2 avoided is:

  1. 1333 kg
  2. 2000 kg
  3. 3000 kg
  4. 3670 kg
Answer: C) 3000 kg
Confirmed vs Book-1 Ch-10 Short Q S-1 method — CO₂ avoided = fuel saved × emission factor. Working: 2000 kg coal × 1.5 kg CO₂/kg coal = 3000 kg CO₂. The book’s own S-1 (110 MW plant, efficiency 28% → 32%) uses an emission factor of 1.53 kg CO₂/kg coal. When an emission factor is given, use it — do NOT also apply the 3.67 carbon route.
Source: AI practice
📖 §10.2 Global environmental issues

52. Which of the following is NOT considered a GLOBAL environmental issue?

  1. Acid rain
  2. Ozone layer depletion
  3. Suspended Particulate Matter (SPM)
  4. Loss of biodiversity
Answer: C) Suspended Particulate Matter (SPM)
Confirmed vs Book-1 §10.2 — the key environmental issues of GLOBAL significance are exactly four: acid rain, ozone layer depletion, global warming & climatic change, and loss of biodiversity. Suspended Particulate Matter is a local/regional air-quality pollutant (from ash in solid fuels, §10.1), not a global issue. This is chapter-end objective Q.6 almost verbatim.
Source: AI practice
📖 §10.13 Sustainable development

53. The Brundtland Commission definition of sustainable development rests on three inter-related objectives. They are:

  1. Economic, social, and environmental
  2. Political, financial, and technical
  3. Local, national, and global
  4. Industrial, agricultural, and commercial
Answer: A) Economic, social, and environmental
Confirmed vs Book-1 §10.13 — the Bruntland Commission report ‘Our Common Future’ (1987) defines sustainable development as ‘meeting the needs of the present without compromising the ability of future generations to meet their own needs’. Its three basic and inter-related objectives are printed as: economic security and prosperity; social development and advancement; environmental sustainability.
Source: AI practice
📖 §10.10 The Kyoto Protocol Mechanisms — Clean Development Mechanism

54. Under the Clean Development Mechanism (CDM) of the Kyoto Protocol, an emission-reduction project earns credits called:

  1. Emission Reduction Units (ERUs)
  2. Certified Emission Reductions (CERs)
  3. Renewable Energy Certificates (RECs)
  4. Perform Achieve Trade (PAT) certificates
Answer: B) Certified Emission Reductions (CERs)
Confirmed vs Book-1 §10.10 — CDM lets an Annex-I country implement an emission-reduction project in a developing (non-Annex-I) country and earn saleable Certified Emission Reduction (CER) credits, ‘each equivalent to one tonne of CO₂’. Contrast Joint Implementation: a project between two countries that BOTH have commitments, earning Emission Reduction Units (ERUs), also 1 t CO₂ each. CERs carry a 2% adaptation levy. (Options tidied: the correct option was previously the only one carrying an explanatory clause, which gave it away.)
Source: AI practice

Short questions (5 marks) — 56

📖 §10.1 Energy and Environment / S-2

1. Explain the linkage between energy and environment with examples.

Model answer: Combustion of hydrocarbon (fossil) fuels in industry and power generation produces by-products that pollute the air. The principal energy-related emissions are carbon dioxide, particulate matter (dust), sulphur oxides (SOx), nitrogen oxides (NOx), hydrocarbons and carbon monoxide. Examples: SOx and NOx cause acid rain; CO results from incomplete combustion; particulate matter comes from ash in solid fuels (coal, lignite, biomass); CO2, though not a classical pollutant, is the main contributor to global warming and climate change. Thus energy use and environmental degradation are directly linked, and energy efficiency reduces these emissions.
Answer in a chain, not a list: fuel burnt -> by-product -> damage. Memory hook for the six emissions: "CO2, PM, SOx, NOx, HC, CO". The trap here is CO2: the book says it is NOT a classical pollutant, yet it is the MAIN cause of global warming - say both or you lose a mark. Always finish with the link line the examiner is looking for: less energy used = less emission, so energy efficiency is itself pollution control.
Source: 2014
📖 §10.1 Principal energy emissions

2. What are the principal air emissions due to energy use, and what is the source of each?

Model answer: The principal emissions impacting the air environment are: carbon dioxide (from oxidation of carbon in fuel; dominates total emissions); particulate matter/dust (from ash content during combustion of solid fuels such as coal, lignite, biomass); sulphur oxides SOx (from sulphur content in oil and coal); nitrogen oxides NOx (from fuel and combustion air); carbon monoxide (from incomplete combustion of fuels); and hydrocarbons. SOx and NOx are major global pollutants leading to acid rain, while CO2 is the major contributor to global warming.
Draw a two-column table (Emission | Source) - it scores faster than a paragraph. The mark is for the SOURCE, not just the name. Keep SOx and NOx apart: sulphur comes from the FUEL (oil, coal), nitrogen comes from the FUEL AND THE COMBUSTION AIR. Common mistake: writing "CO from coal" - CO comes from INCOMPLETE combustion of any fuel, and particulate matter comes from the ASH in solid fuels.
Source: 2014
📖 §10.2 Global Environmental Issues

3. What are the key environmental issues of global significance? Why are they called 'global'?

Model answer: The key environmental issues of global significance are: (1) Acid rain, (2) Ozone layer depletion, (3) Global warming and climatic change, and (4) Loss of biodiversity. They are called global because they affect all mankind on a global scale without regard to any particular country or region; the whole world is a stakeholder and they need to be addressed through international efforts. Note: Suspended Particulate Matter (SPM) is a LOCAL air-quality issue, not a global one.
Memory hook for the four: A-O-G-B (Acid rain, Ozone depletion, Global warming, Biodiversity loss). The second half of the question carries marks too - "global" means the whole world is a stakeholder, the effect ignores country borders, so only international action can fix it. Trap: SPM (dust) is a LOCAL air-quality problem, never write it in this list of four.
Source: 2014
📖 §10.2 Global vs local issues

4. Why is Suspended Particulate Matter (SPM) not classified as an environmental issue of global significance?

Model answer: The four issues of global significance are acid rain, ozone layer depletion, global warming/climate change and loss of biodiversity, because each affects all mankind on a global scale and requires international action. Suspended Particulate Matter (SPM), by contrast, is predominantly a local air-pollution problem affecting air quality and health in the immediate region where dust/ash is emitted (e.g. near a power plant or city). Its impact does not spread worldwide, so it is treated as a local rather than a global issue.
This is the examiner testing the local-vs-global line. The test is simple: does the damage cross borders? Acid rain, ozone, warming and biodiversity do; SPM settles near where it is emitted, so it hurts local air quality and health only. Say the four global issues first, then explain SPM - answering only about SPM loses the listing marks.
Source: 2014
📖 §10.3 Acid Rain

5. Write short notes on the causes of acid rain and its effects.

Model answer: Causes: Acid rain is caused by release of sulphur oxides (SOx) and nitrogen oxides (NOx) from combustion of fossil fuels, which mix with water vapour in the atmosphere to form sulphuric acid (H2SO4) and nitric acid (HNO3) respectively. It is a trans-boundary issue and deposits as wet deposition (rain, snow, sleet) and dry deposition (particulates, gases). Effects: acidification of lakes, streams and soils; direct and indirect effects (release of metals such as aluminium which wash away plant nutrients); killing of wildlife (trees, crops, aquatic plants and animals); decay of building materials, paints, statues and sculptures; and health problems (respiratory, burning skin and eyes).
Fix the two pairs: SOx + water vapour = sulphuric acid (H2SO4), NOx + water vapour = nitric acid (HNO3). Write both forms of deposition - WET (rain, snow, sleet) and DRY (particulates, gases) - many students give only wet. The word "trans-boundary" is worth writing: the acid falls in a country that did not emit it. Split your answer clearly into Causes and Effects, since the question asks for both.
Source: 2010
📖 §10.1 Environmental impacts of fossil-fuel combustion

6. What are the environmental impacts of combustion of fossil fuels?

Model answer: Combustion of fossil fuels emits carbon dioxide (CO2), sulphur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons and particulate matter. SOx and NOx mix with atmospheric water vapour to form sulphuric and nitric acids, causing acid rain (a trans-boundary issue). CO arises from incomplete combustion and is toxic. CO2 is the dominant emission and is the major contributor to global warming and climate change (the enhanced greenhouse effect). Particulate matter causes local air-quality and health problems. CFCs used in energy services (refrigeration/AC) also deplete the ozone layer.
Do not just list gases - each emission must be tied to its damage: SOx/NOx -> acid rain, CO -> toxic, incomplete combustion, particulates -> local air quality, CO2 -> enhanced greenhouse effect and climate change. Adding CFCs (refrigeration/AC) -> ozone depletion shows the full picture and usually earns the last mark.
Source: 2009
📖 §10.4 Ozone Layer Depletion

7. What is the ozone layer, where is it located, and why is it beneficial?

Model answer: The ozone layer is a thin layer of ozone (O3) present in the stratosphere, which extends about 10-50 km above the earth. It is highly beneficial to life on earth because it blocks the sun's harmful Ultraviolet (UV-B) radiation from reaching the earth's surface. Any disturbance or depletion of the ozone layer increases the harmful radiation reaching the surface, leading to dangerous consequences such as skin cancer, eye diseases and ecosystem damage. Ozone is naturally produced (oxygen absorbing UV below 240 nm) and destroyed (absorbing UV above 290 nm) in a balanced equilibrium.
Two numbers must appear: the stratosphere is about 10-50 km up, and the radiation blocked is UV-B. Trap to avoid: ozone HIGH UP in the stratosphere is our shield and is good; ozone at ground level is a pollutant and a greenhouse gas. Also mention that ozone is constantly made and destroyed naturally - depletion means this balance has been upset.
Source: 2014
📖 §10.4 CFC catalytic mechanism

8. Explain the chemistry of ozone layer depletion by CFCs.

Model answer: Chlorofluorocarbons (CFCs) emitted into the atmosphere diffuse up to the stratosphere. There, strong UV radiation strikes a CFC (CFCl3) molecule and breaks a carbon-chlorine bond, releasing a free chlorine (Cl) atom. The chlorine atom reacts with an ozone (O3) molecule, breaking it into an ordinary oxygen molecule (O2) and a chlorine monoxide (ClO) molecule. A free oxygen atom then breaks up the ClO, releasing the chlorine atom again, which is free to repeat the process. Thus one chlorine atom can destroy an estimated 10,000 to 100,000 ozone molecules. It is the released chlorine (and bromine from halons) that destroys ozone, not the intact molecule.
Write it as three steps: (1) UV splits CFCl3 and frees a Cl atom, (2) Cl + O3 -> O2 + ClO, (3) a free O atom takes the O from ClO and releases Cl again. The whole point is that chlorine acts as a CATALYST - it comes back out and repeats, which is why one Cl atom destroys 10,000 to 100,000 ozone molecules. Memorise that number; it is the marks-carrying figure. Common mistake: saying the CFC molecule itself eats ozone - it is the released chlorine (or bromine) atom.
Source: 2014
📖 §10.4 ODS and substitutes

9. Which substances cause ozone depletion, and what are the counter-measures?

Model answer: Ozone is broken down by man-made chlorine and bromine compounds. The main culprit is chlorofluorocarbons (CFCs), used in refrigerators and air conditioners; others include HCFCs, carbon tetrachloride and methyl chloroform (which release chlorine) and halons and methyl bromide (which release bromine). Strong UV in the stratosphere splits these ODS molecules and the freed chlorine/bromine atom destroys ozone. Counter-measures listed in the book: the international agreement signed at the Montreal Protocol (the guidebook prints the year as 1974 — write 1974 in the exam; the real-world date is 1987) to phase out ozone-depleting chemicals; a tax imposed on the use of ozone-depleting substances; use of ozone-friendly substitutes HCFC and HFC (lower ozone-depleting potential and shorter life); and recycling of CFCs and halons.
Split the ODS list by the atom released: chlorine from CFC, HCFC, carbon tetrachloride and methyl chloroform; bromine from halons and methyl bromide. CFC (fridges and AC) is the main culprit. For counter-measures give all four: Montreal Protocol, tax on ODS, HCFC/HFC substitutes, and recycling of CFCs and halons. Exam rule for this chapter: the 2014 guidebook prints Montreal Protocol as signed in 1974 - WRITE 1974, not 1987.
Source: 2014
📖 §10.4 Effects of ozone depletion

10. List the effects of ozone layer depletion.

Model answer: Effects of ozone layer depletion from increased UV-B penetration: (1) Human and animal health - eye diseases, skin cancer and infectious diseases. (2) Terrestrial plants - changed species composition in forests/grasslands, altered biodiversity, changes in plant form and metabolism. (3) Aquatic ecosystems - damage to phytoplankton (base of food webs) and to early stages of fish, shrimp, crab and amphibians, reducing reproduction. (4) Bio-geo-chemical cycles - altered sources and sinks of greenhouse and trace gases (CO2, CO, COS). (5) Air quality - higher photo-dissociation rates producing oxidants like hydrogen peroxide harmful to health and materials.
Answer under the five headings the book uses - health, terrestrial plants, aquatic ecosystems, bio-geo-chemical cycles, air quality - one line each; headings themselves attract marks. Remember phytoplankton, because it is the base of the ocean food chain. Common mistake: filling this answer with melting glaciers and sea-level rise - those belong to GLOBAL WARMING, not ozone depletion.
Source: 2014
📖 §10.4 & §10.10 — Montreal (ozone) vs Kyoto (climate)

11. Distinguish the ozone layer problem from global warming, and name the protocol addressing each.

Model answer: Ozone depletion and global warming are two separate problems. Ozone depletion is the thinning of the stratospheric ozone layer (10–50 km up) caused mainly by CFCs, whose chlorine/bromine atoms destroy ozone, allowing more harmful UV-B to reach the earth; it is addressed by the MONTREAL PROTOCOL (the 2014 guidebook prints this as 'signed in 1974' — reproduce the book's 1974 in the exam; the real-world date is 1987). Global warming is the rise in the earth's temperature from the enhanced greenhouse effect caused by CO2, CH4, N2O, HFCs, PFCs and SF6; it is addressed by the KYOTO PROTOCOL (1997) under the UNFCCC (1992). Global warming does NOT increase the size of the ozone hole — the two are distinct. Memory aid: 'Montreal = Ozone, Kyoto = Climate.'
This is the classic trap pair. Memory hook: "Montreal = Ozone, Kyoto = Climate" (M before K, ozone problem came first). Keep the causes apart too: CFCs and their chlorine cause ozone loss; CO2, CH4, N2O, HFC, PFC, SF6 cause warming. State plainly that global warming does not enlarge the ozone hole - examiners set this as a true/false. Dates for the exam: Montreal as printed in the book (1974), UNFCCC 1992, Kyoto 1997.
Source: 2014
📖 §10.5 Atmosphere composition

12. What is the composition of the atmosphere by volume, and which layer holds most molecules?

Model answer: The atmosphere is composed mainly of 78% Nitrogen, 21% Oxygen, about 0.04% Carbon dioxide and about 0.04% Argon by volume, with water vapour and several other gases present in very small amounts. The two most important layers are the troposphere (where weather occurs) and the stratosphere; the air gets thinner with altitude, and about 90% of all molecules in the atmosphere are in the troposphere. Although water vapour is the most abundant natural greenhouse gas, the main GHG constituent influenced by human activity is CO2.
Memorise as a quick set: N2 78%, O2 21%, CO2 about 0.04%, Argon about 0.04%. The second number is 90% of all molecules sit in the troposphere (the lowest layer, where weather happens) - the air simply gets thinner with height. Trap: water vapour is the most abundant natural greenhouse gas, but humans do not change it directly; CO2 is the one human activity raises.
Source: 2014
📖 §10.5 Natural greenhouse effect

13. Explain the natural greenhouse effect.

Model answer: The earth is surrounded by a blanket of greenhouse gases (water vapour, carbon dioxide, methane, nitrous oxide). The earth's atmosphere allows short-wave solar radiation from the sun to pass relatively unimpeded, but the long-wave infrared radiation emitted by the warm earth's surface is partially trapped and re-emitted downwards by these greenhouse gases. This blanketing keeps the surface warmer than it would otherwise be - much as glass traps heat in a greenhouse. Without naturally occurring greenhouse gases, the earth's average surface temperature would be a cold -18 degrees C instead of the tolerable +15 degrees C. The natural greenhouse effect is therefore a natural process that made life on Earth possible.
The two numbers ARE the answer: without natural greenhouse gases the earth would be -18 degrees C instead of +15 degrees C - a 33 degree difference. Explain in the short-wave/long-wave way: sunlight comes in easily as short-wave, the warm earth sends heat back as long-wave infrared, and the GHG blanket traps and re-radiates that. Say clearly that this natural effect is GOOD - it made life possible; only its intensification is the problem.
Source: 2014
📖 §10.5 Enhanced greenhouse effect

14. What is the enhanced greenhouse effect, and how does it differ from the natural greenhouse effect?

Model answer: The natural greenhouse effect keeps earth at a habitable +15 degrees C (instead of -18 degrees C). The enhanced (human/anthropogenic) greenhouse effect is its intensification caused by the increase of greenhouse gases in the atmosphere, especially CO2 from burning fossil fuels (coal, oil, gas) together with widespread deforestation over the past 50-200 years. The gases directly increased by human activity are carbon dioxide, methane, nitrous oxide, CFCs and ozone (water vapour is not changed directly by humans). This extra trapping is changing the global climate; the earth's average temperature has risen by about 0.75 degrees C since 1880. In short, the natural effect sustains life, while the enhanced effect causes harmful warming.
Answer in a contrast: natural = keeps earth at +15 degrees C instead of -18 degrees C and is essential; enhanced = extra trapping from human emissions and is harmful. Numbers to quote: the rise of about 0.75 degrees C since 1880, and the causes - fossil fuel burning plus deforestation over the last 50-200 years. Common mistake: saying humans increase water vapour - the book lists CO2, CH4, N2O, CFCs and ozone as the human-raised ones.
Source: 2014
📖 §10.5 Enhanced GH effect + lighting energy-saving calc

15. (a) Write a short note on the enhanced greenhouse effect. (b) An office replaces 10 CFLs (30 W each) with 10 LEDs (10 W each). If operation is 2000 hours per year, calculate the annual energy savings and savings in Rs at Rs.6 per kWh.

Model answer: (a) Enhanced greenhouse effect: the intensification of the natural greenhouse effect due to increased anthropogenic emissions of greenhouse gases (CO2, CH4, N2O, CFCs), which trap more of the outgoing infrared radiation and cause global warming and climate change. (b) Saving per lamp = 30 - 10 = 20 W; for 10 lamps = 200 W = 0.2 kW. Annual energy saving = 0.2 kW x 2000 h = 400 kWh/year. Cost saving = 400 x Rs.6 = Rs.2400 per year.
Part (a) is short - say the natural effect is intensified by extra man-made GHGs, quote -18 vs +15 degrees C, and stop; save time for the sum. Part (b) sequence: saving per lamp (30 - 10 = 20 W) -> total watts (x10 = 200 W) -> convert to kW (0.2 kW) -> multiply by hours (x2000 = 400 kWh) -> multiply by tariff (x6 = Rs.2400). The usual mark-loser is forgetting to divide by 1000 to get kW. Write the unit at every step.
Source: 2022
📖 §10.5 CO2 as principal GHG

16. Why is carbon dioxide considered the most important greenhouse gas?

Model answer: Carbon dioxide is the most important greenhouse gas because of its abundance in the atmosphere. Its increase has contributed about 60% of the enhanced greenhouse effect, and its concentration (about 397 ppm, Mauna Loa Nov 2014) is much higher than that of other greenhouse gases. It is also persistent, with an atmospheric lifetime of over 100 years. The major source is fossil-fuel combustion (coal, petroleum, natural gas); for the same heat released, natural gas emits the least CO2 and coal the most. Cement manufacture is a major industrial source (from both fuel combustion and calcination of limestone), and deforestation also adds CO2.
Do not confuse the two "most" questions: SF6 is the MOST POTENT gas (GWP 22,000) but CO2 is the BIGGEST CONTRIBUTOR - about 60% of the enhanced greenhouse effect - because there is so much of it. The three figures to memorise: 60%, 397 ppm (Mauna Loa, Nov 2014) and a lifetime over 100 years. Add the fuel ranking for an extra mark: for the same heat, coal emits the most CO2 and natural gas the least.
Source: 2014
📖 §10.5 Methane sources

17. What are the natural and anthropogenic sources of methane (CH4)?

Model answer: Methane is a naturally occurring inflammable gas produced by geological coal formations and by decomposition of organic matter. The main NATURAL source is wetlands; methane also forms when organic matter (food, vegetables) decomposes without oxygen - anaerobic decomposition. ANTHROPOGENIC (human) sources include leakage during coal mining, leakage from natural-gas pipelines and petroleum wells, rice cultivation, belching from cattle and other livestock (ruminants/cud-chewing animals), decay of municipal solid waste in landfills, and wood burning.
Split the answer under two headings, NATURAL and ANTHROPOGENIC - the question asks for both, and one list only gets half the marks. Natural: wetlands (the main one) and anaerobic decay of organic matter. Human: coal mining leaks, gas pipeline and oil-well leaks, paddy (rice) cultivation, cattle belching, landfill waste, wood burning. Hook: methane = "marsh gas" - anywhere organic matter rots without air. Useful extras: GWP 23, life 12 years (the shortest-lived of the main GHGs).
Source: 2014
📖 §10.5 Nitrous oxide sources

18. What are the sources of nitrous oxide (N2O) emissions associated with human activity?

Model answer: Nitrous oxide (N2O) emissions associated with human activity come from: use of nitrogen fertilizer, manure, biomass combustion, fossil-fuel combustion in power plants, and the chemical industry (for example nylon production). N2O is also contained in soil by bacteria - when farmers plough the soil and disturb the surface layer, N2O is released into the atmosphere. It is also released from catalytic converters in cars. N2O has a long atmospheric lifetime of about 120 years and a high GWP of 300.
Group the sources: farming (nitrogen fertilizer, manure, ploughing which releases N2O held by soil bacteria), burning (biomass and fossil fuel in power plants), and industry (chemical industry, e.g. nylon) plus car catalytic converters. Numbers worth adding: GWP 300 and an atmospheric life of about 120 years (the GWP table shows 114 years - either is acceptable, both come from the book). Common mistake: calling N2O an ozone-depleting substance - here it is a greenhouse gas.
Source: 2014
📖 §10.5 CFCs and substitutes

19. Describe the properties and uses of chlorofluorocarbons (CFCs) and their substitutes.

Model answer: Chlorofluorocarbons (CFCs) are man-made chemicals that vaporise just below room temperature and are non-toxic and non-flammable. They contain chlorine atoms and have been used as refrigerants, cleaning solvents, in manufacture of insulation, and as propellants in spray cans. They are chemically unreactive, so once released they remain in the atmosphere for a long time (about 100 to 200 years) before being destroyed. As an outcome of the Montreal Protocol, CFCs are being phased out and replaced by hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs); these are less destructive to ozone and have shorter life, but are still greenhouse gases.
Cover properties, uses and substitutes - all three carry marks. Properties: man-made, boil just below room temperature, non-toxic, non-flammable, chemically unreactive, so they survive 100 to 200 years in the air. That very stability is why they reach the stratosphere. Uses hook: "Refrigerant, Solvent, Insulation, Spray-can propellant". Trap: HCFC and HFC are BETTER for ozone but are STILL greenhouse gases - and HFC is one of the six Kyoto gases while CFC is dealt with under Montreal.
Source: 2014
📖 §10.5 PFCs and SF6

20. Write short notes on perfluorocarbons (PFCs) and sulphur hexafluoride (SF6) as greenhouse gases.

Model answer: Perfluorocarbons (PFCs) are important greenhouse gases with a very long atmospheric life of more than several thousand years (about 50,000 years - the longest of the GHGs), so their emissions accumulate and influence climate for thousands of years. The largest known man-made sources are primary aluminium production and semiconductor manufacture. Sulphur hexafluoride (SF6) is the MOST POTENT greenhouse gas (highest GWP, about 22,000). It is used in insulation and electric-power transmission equipment (switchgear), the magnesium industry, semiconductor manufacturing (to create circuitry patterns on silicon wafers), and as a tracer gas for leak detection.
Keep the two "records" apart - this is the standard trap. PFC = longest LIFE, about 50,000 years (GWP 5700). SF6 = highest GWP, 22,000, the most potent GHG (life 3200 years). Hook: "P for Permanent (PFC lives longest), S for Strongest (SF6 hits hardest)". Sources to quote: PFC from aluminium production and semiconductors; SF6 from switchgear/electrical insulation, magnesium industry, semiconductors and leak-detection tracer gas.
Source: 2014
📖 §10.5 GWP definition & significance

21. Define Global Warming Potential (GWP) and explain its significance.

Model answer: Global Warming Potential (GWP) is the ratio of global warming (radiative forcing/heat trapped) from one unit mass of a greenhouse gas to that from one unit mass of CO2 over a period of time (usually 100 years). CO2 is the reference, with GWP = 1. GWP takes into account both the absorption strength of the molecule and its atmospheric lifetime - the higher the GWP, the larger the infrared absorption and the longer the atmospheric lifetime. Significance: it gives a common basis (CO2-equivalent) to compare the relative climate impact of different gases, lets emissions of various gases be aggregated for inventories, targets and trading, and shows that even small amounts of high-GWP gases like SF6 (22,000) contribute significantly to warming.
Write the definition as a ratio: heat trapped by 1 unit mass of the gas divided by that of 1 unit mass of CO2, over 100 years, with CO2 = 1 by definition. Say what GWP combines - how strongly the molecule absorbs infrared AND how long it survives in the air; that is why a long-lived gas scores high. For the significance mark, the key words are "CO2-equivalent": GWP puts all gases on one scale so emissions can be added up, traded and targeted. Example that always fits: SF6 at 22,000.
Source: 2014
📖 §Table 10.1 GWP and lifetime values

22. Give the GWP values and atmospheric lifetimes of the main greenhouse gases. Which has the highest GWP and which the longest life?

Model answer: From Table 10.1: Carbon dioxide (CO2) GWP = 1 (the standard), lifetime 5-200 yrs; Methane (CH4) GWP = 23, lifetime 12 yrs; Nitrous oxide (N2O) GWP = 300, lifetime 114 yrs; CFCs GWP = 4000-8000, lifetime 5-100 yrs; Perfluorocarbons (PFCs) GWP = 5700, lifetime about 50,000 yrs; Sulphur hexafluoride (SF6) GWP = 22,000, lifetime 3200 yrs; ozone exists only days/weeks. SF6 has the HIGHEST GWP (22,000) and is the most potent. PFC has the LONGEST atmospheric lifetime (about 50,000 years). Among methane, N2O, CFC and PFC, methane (23) has the lowest GWP.
Best written as a table with three columns: Gas | GWP | Life. Learn the ladder of GWP: CO2 1, CH4 23, N2O 300, CFC 4000-8000, PFC 5700, SF6 22,000. Two facts the examiner asks in the last line: HIGHEST GWP = SF6 (22,000); LONGEST LIFE = PFC (about 50,000 years). Note the pattern break - PFC has a lower GWP than CFC's upper range but by far the longest life, so never assume high GWP means long life.
Source: 2014
📖 §10.5 The 6 Kyoto greenhouse gases

23. Name the six major greenhouse gases covered under the Kyoto Protocol.

Model answer: The six major greenhouse gases whose emissions are covered by the Kyoto Protocol targets are: (1) Carbon dioxide (CO2), (2) Methane (CH4), (3) Nitrous oxide (N2O), (4) Hydrofluorocarbons (HFCs), (5) Perfluorocarbons (PFCs), and (6) Sulphur hexafluoride (SF6). Although ozone and CFCs are also greenhouse gases, CFCs are handled under the Montreal Protocol, not Kyoto. Emissions are measured as carbon-dioxide equivalent (CO2e) using each gas's GWP.
Memory hook for the six: "C-M-N + H-P-S" - CO2, CH4, N2O, then HFC, PFC, SF6. Common mistake: writing CFC as the fourth - CFC is controlled by the MONTREAL Protocol, and it is its replacement HFC that sits in the Kyoto list. Add one line about CO2-equivalent (each gas converted using its GWP) - that is usually the extra mark.
Source: 2014
📖 §10.5 Carbon sequestration / CCS

24. Explain carbon sequestration and where the captured CO2 is stored.

Model answer: Carbon sequestration is the process of removing/capturing CO2 from large POINT SOURCES such as power plants, oil refineries and industrial processes, and then storing it so it does not reach the atmosphere. The captured CO2 is stored in geologic formations such as depleted oil and gas reservoirs, deep coal seams, or saline reservoirs. The engineered route is known as Carbon Capture and Storage (CCS), commonly using amine scrubbing to separate CO2 from flue gases. This is distinct from natural sinks: oceans and terrestrial biomass together absorb about half the excess CO2 generated by human activities.
The two words to stress are POINT SOURCE (power plant, refinery, industrial process) and STORAGE. Give the storage places by name: depleted oil and gas reservoirs, deep coal seams, saline reservoirs. Naming amine scrubbing as the separation method and CCS as the engineered route adds detail cheaply. Do not confuse this with natural sinks - oceans and biomass absorbing CO2 is a different question.
Source: 2014
📖 §10.5 Natural carbon sinks

25. What are the major natural carbon sinks, and how much CO2 do they absorb?

Model answer: Natural carbon sinks absorb atmospheric CO2. The OCEANS are a major sink, containing about 50 times more carbon than the atmosphere. Terrestrial BIOMASS, including trees and grasses, stores about three times more carbon than the atmosphere. Together, the ocean and terrestrial ecosystems absorb about half of the excess CO2 generated by human activities. (The process of capturing CO2 from point sources and storing it is separately called carbon sequestration.)
Three numbers carry the marks: oceans hold about 50 times more carbon than the atmosphere, terrestrial biomass about 3 times more, and together they absorb about HALF the excess CO2 humans produce. Hook: "50 - 3 - half". Keep it separate from carbon sequestration, which is the man-made capture-and-store route; here the sinks are natural.
Source: 2014
📖 §10.5 Global and India CO2 emissions

26. Summarise the global and India greenhouse-gas emission profile given in the guidebook.

Model answer: Since the Industrial Revolution, annual CO2 emissions from fuel combustion rose to almost 36 Giga tonnes of CO2 in 2013, with energy use being by far the largest source. CO2 from fossil fuels and cement contributes almost 70% of global GHG emissions. India contributes almost 7% of global emissions and is the third-largest CO2 emitter behind China and the USA. India emitted about 2.5 Giga tonnes of CO2 in 2013, but per-capita emissions remain low at about 1.6 tonnes per annum. Coal-based power production accounts for almost 70% of India's coal-related CO2 emissions.
This is a pure numbers answer, so learn the string: 36 Giga tonnes CO2 globally in 2013; fossil fuels + cement = almost 70% of global GHG; India about 7% of global emissions and the 3rd largest emitter (after China and the USA); India about 2.5 Giga tonnes in 2013; per capita only about 1.6 tonnes per year; coal-based power = about 70% of India's coal CO2. The point the examiner wants stated: India's TOTAL is large but its PER CAPITA is low.
Source: 2014
📖 §10.6 Impacts of global warming

27. List four impacts of global warming.

Model answer: Four impacts of global warming (from a longer list in the guidebook): (1) Increasing ocean temperature and rising sea levels - mainly from thermal expansion of warming ocean water, causing coastal flooding. (2) Snow and ice melting - mountain glaciers, ice sheets and Arctic sea ice melt, raising sea levels and disrupting water supply. (3) Altered rainfall patterns and more extreme weather events (cyclones, storms, floods, droughts) and severe heat waves. (4) Loss of biodiversity as ecosystems change and species cannot adapt. Other impacts: increased diseases (e.g. malaria spread), dwindling freshwater supply and food shortages.
The question says four - give exactly four with a one-line explanation each; a bare list of words scores poorly. Safest four: sea-level rise, ice and glacier melting, changed rainfall and extreme weather, loss of biodiversity. Common mistake: writing ozone-depletion effects (skin cancer, eye disease) here - those belong to the ozone question. Health here means things like malaria spreading.
Source: 2014
📖 §10.6 Sea-level rise / thermal expansion

28. Explain how global warming causes rising sea levels.

Model answer: During the twentieth century the average sea level increased by about 20 cm. The LARGEST contribution to this rise is thermal expansion of ocean water - as the oceans warm, the water expands and the sea level rises. In addition, melting of mountain glaciers, ice sheets (West Antarctica and Greenland) and Arctic sea ice adds water to the oceans. A further rise of 10-20 cm by 2030 and up to 1 m by 2100 is predicted. Coastal flooding will increase; people in low-lying countries (e.g. Bangladesh) and even developed countries (e.g. the Netherlands) are vulnerable, since about half the world's population lives near coastal zones.
The mark-carrying point is the CAUSE ranking: THERMAL EXPANSION of warming ocean water is the largest contributor, melting ice comes second. Many students write only "ice melts" and lose the main mark. Numbers: about 20 cm rise during the twentieth century, a further 10-20 cm by 2030 and up to 1 m by 2100. Finish with who suffers - about half the world's population lives in coastal zones (Bangladesh, the Netherlands).
Source: 2014
📖 §10.6 Biodiversity / loss of biodiversity

29. What is biodiversity, and how is it affected by global warming?

Model answer: Biodiversity (biological diversity) is the variety and variability of all living organisms - the diversity within species (genetic), between species, and of ecosystems - including plants, animals, microorganisms and the ecological complexes of which they are part. Global warming threatens biodiversity: ecosystems will change, some species moving farther north or thriving while others cannot move and may become extinct. Up to about 25% of mammals and 12% of birds may become extinct over coming decades as warmer conditions alter forests, wetlands and rangelands and human development blocks migration. Oceans are also affected - for example coral reefs, which have limited tolerance for warm water, are severely impacted.
Define biodiversity at three levels - within species (genetic), between species, and of ecosystems - not just "many plants and animals". Then link to warming: ranges shift north, species that cannot move go extinct, and human development blocks migration routes. Numbers to quote: up to about 25% of mammals and 12% of birds may be lost in coming decades. Coral reefs are the standard example, as they tolerate warm water poorly.
Source: 2014
📖 §10.7 UNFCCC

30. What is the UNFCCC, when was it signed, and what is its objective?

Model answer: The United Nations Framework Convention on Climate Change (UNFCCC) was signed by over 160 countries at the UN Conference on Environment and Development (the Earth Summit) at Rio de Janeiro in June 1992, and came into force in 1994. Its objective is to stabilise greenhouse-gas concentrations 'at a level that would prevent dangerous anthropogenic (human) interference with the climate system.' The short-term objective was that developed countries should return their GHG emissions (particularly CO2) to 1990 levels by the year 2000; the long-term objective is stabilisation within a time-frame allowing ecosystems to adapt, food production to continue and sustainable economic development. Developed countries should take the lead.
Dates first, they are the easy marks: signed June 1992 at the Rio Earth Summit by over 160 countries, in force 1994. Write the objective in the book's own words - stabilise GHG concentrations to prevent "dangerous anthropogenic interference with the climate system". Then split short-term (developed countries back to 1990 emission levels by 2000) from long-term (stabilise so ecosystems adapt, food production continues, development stays sustainable). Trap: the UNFCCC only ENCOURAGED; it is Kyoto that BINDS.
Source: 2014
📖 §10.8 IPCC

31. What is the IPCC and when and by whom was it formed?

Model answer: The IPCC, the Intergovernmental Panel on Climate Change, was formed in 1988 by the World Meteorological Organization (WMO) and the United Nations to review climatic data and periodically report on their findings. Its 1995 report concluded that the observed increase in global average temperature over the last century 'is unlikely to be entirely natural in origin' and that there is a 'discernible human influence on global climate.' The panel projected (if trends continue) an average global temperature increase of 1.4 to 5.8 degrees C in the twenty-first century, with about 75% of the warming due to CO2. The 1995 report led directly to the 1997 Kyoto Protocol.
Four facts: 1988, by the WMO and the UN, to review climate data and report periodically. Its 1995 report is the one that found a "discernible human influence on global climate", and that report led straight to the 1997 Kyoto Protocol. Projection to memorise: 1.4 to 5.8 degrees C rise in the twenty-first century, about 75% of it due to CO2. Trap: the IPCC only assesses science - it does not set emission targets; the COP/Kyoto does.
Source: 2014
📖 §10.9 Conference of Parties (COP)

32. What is the Conference of Parties (COP), and what is its purpose?

Model answer: The COP (Conference of Parties) is the 'supreme body' of the UNFCCC. The Parties to the Convention meet annually in the form of a COP, and countries that have joined the UNFCCC are referred to as 'Parties to the Convention.' The primary task of the COP is to promote and review the implementation of the Convention and any related legal instruments (such as the Kyoto Protocol). Meetings held between each COP are called Intersessional meetings. The landmark COP is COP-3, held in 1997, which resulted in the Kyoto Protocol - setting legally binding emission targets for developed (Annex I) countries for the six major greenhouse gases, to be reached over 2008-2012.
Two phrases must appear: the COP is the "supreme body" of the UNFCCC, and member countries are the "Parties to the Convention". It meets annually; meetings in between are Intersessional meetings. The mark for the landmark: COP-3 (1997) produced the Kyoto Protocol. Trap: the COP belongs to the UNFCCC, not to the IPCC - do not mix them up.
Source: 2014
📖 §10.10 Kyoto Protocol

33. What is the Kyoto Protocol and what are its main features?

Model answer: The Kyoto Protocol is an international agreement linked to the UNFCCC. Its major feature is that it sets BINDING targets for 37 industrialized countries and the European community to reduce greenhouse-gas emissions - an average of 5% against 1990 levels over the five-year period 2008-2012. The key difference from the Convention is that while the Convention only encouraged industrialized countries to stabilise emissions, the Protocol commits them to do so. Recognising that developed countries are principally responsible for current high GHG levels from over 150 years of industrial activity, it places a heavier responsibility on them under the principle of 'common but differentiated responsibilities.' It entered into force in 2005 (when Russia ratified); the USA (about 25% of global GHG) has not ratified it.
Learn the target as one sentence: 37 industrialized countries + the EU, average 5% cut against the 1990 base year, over the first commitment period 2008-2012. Three more marks: adopted 1997, entered into force 2005 (when Russia ratified), USA (about 25% of global GHG) never ratified. The one-line difference the examiner wants: the Convention only encouraged, the Protocol COMMITS. Keep 1990 (base year) and 2008-2012 (target period) apart.
Source: 2014
📖 §10.10 Common but differentiated responsibilities

34. Explain the principle of 'common but differentiated responsibilities' in climate change mitigation.

Model answer: Under this principle, both industrialized and developing countries share a COMMON responsibility to address climate change as members of the international community, but the responsibility is DIFFERENTIATED according to their respective capabilities and historical contribution. Because developed countries are principally responsible for the current high levels of GHG in the atmosphere as a result of more than 150 years of industrial activity, the Kyoto Protocol places a heavier responsibility on them and requires developed (Annex I) countries to take the lead. This is the correct view of responsibility: shared, but weighted by capability and past emissions.
Answer by splitting the phrase: COMMON because every country shares one atmosphere; DIFFERENTIATED because capability and history differ. The evidence line is the one to memorise - developed countries caused today's high GHG levels through more than 150 years of industrial activity, so Kyoto puts binding targets only on Annex I and asks them to take the lead. Common mistake: writing that developing countries have NO responsibility - the responsibility is shared, only the burden is weighted.
Source: 2014
📖 §10.10 Annex I / Annex II / Non-Annex I Parties

35. How does the Convention divide countries into groups according to their commitments?

Model answer: The Convention divides countries into three main groups: (1) Annex I Parties - the industrialized countries that were OECD members plus countries with economies in transition (EIT Parties), including the Russian Federation, Baltic States and several Central/Eastern European states; they carry the binding emission targets. (2) Annex II Parties - the OECD members of Annex I but not the EIT Parties; they must provide financial resources and promote transfer of environmentally friendly technologies to developing and EIT countries. (3) Non-Annex I Parties - mostly developing countries, recognised as especially vulnerable to climate change (e.g. low-lying coastal states, those prone to drought).
Three groups, and the mark is in what each must DO. Annex I = industrialized (OECD + economies in transition such as Russia, Baltic and East European states) - they carry the emission targets. Annex II = Annex I MINUS the EIT countries - they must provide money and technology transfer. Non-Annex I = developing countries - no targets, and recognised as most vulnerable. Hook: "Annex I owes cuts, Annex II owes cash, Non-Annex I gets help."
Source: 2014
📖 §10.10 Three Kyoto flexibility mechanisms

36. Describe the three flexibility mechanisms of the Kyoto Protocol, distinguishing CDM from Joint Implementation.

Model answer: The Kyoto Protocol offers three market-based flexibility mechanisms to help Parties meet targets economically: (1) Emissions Trading ('carbon trading') - countries with spare emission units (allowed but not used) sell this excess to countries over their targets; carbon is traded like a commodity in the 'carbon market.' (2) Clean Development Mechanism (CDM) - a country with a commitment implements an emission-reduction project in a developing country, earning saleable Certified Emission Reductions (CERs), each equal to one tonne of CO2. (3) Joint Implementation (JI) - a project between two Annex I (committed) countries, earning Emission Reduction Units (ERUs), each equal to one tonne of CO2. Key difference: CDM links a committed country with a non-committed (developing) country, whereas JI is between two committed countries.
Learn the three as name + credit + who is involved. Emissions Trading = spare units sold, the "carbon market". CDM = Annex I funds a project in a DEVELOPING (non-Annex I) country, credit = CER. JI = Annex I project in ANOTHER Annex I country, credit = ERU. Both CER and ERU equal one tonne of CO2. Hook: "CDM = Developing country, C for CER; JI = Joined by two committed countries, E for ERU." This CDM/JI mix-up is the most common mark-loser in the chapter.
Source: 2014
📖 §10.10 Clean Development Mechanism (CDM) & CER

37. What is the Clean Development Mechanism (CDM) and what are CERs?

Model answer: The Clean Development Mechanism (CDM) allows a country with an emission-reduction commitment under the Kyoto Protocol to implement an emission-reduction project in a developing (non-Annex I) country. Such projects earn saleable Certified Emission Reduction (CER) credits, each equivalent to one tonne of CO2, which can be counted towards meeting the developed country's Kyoto targets. The mechanism delivers both sustainable development in the host country and cost-effective emission reductions, while giving industrialized countries flexibility in meeting targets. The major CDM projects have come from renewable energy, followed by waste handling and disposal.
The one number to state: 1 CER = 1 tonne of CO2. Direction matters - the money and technology flow FROM the committed (Annex I) country INTO the developing (non-Annex I) host, and the credits flow back. Two benefits, one for each side: sustainable development for the host, cheap compliance for the investor. Extra mark: renewable energy is the largest CDM project category, followed by waste handling and disposal. If JI appears in the same question, keep CER with CDM and ERU with JI.
Source: 2014
📖 §10.10 Joint Implementation (JI) & ERU

38. What is Joint Implementation (JI), and how does it differ from CDM?

Model answer: Joint Implementation (JI) allows a country with an emission-reduction commitment under the Kyoto Protocol to earn Emission Reduction Units (ERUs) from an emission-reduction or emission-removal project in ANOTHER Annex I country, each ERU equivalent to one tonne of CO2, counted towards its Kyoto target. The project must provide a reduction in emissions (or enhancement of removals by sinks) additional to what would otherwise have occurred; the host Party benefits from foreign investment and technology transfer. The difference from CDM: JI projects are between two countries that BOTH have commitments, whereas CDM projects are between one country that has commitments and another (developing country) that does not.
Write ERU = 1 tonne of CO2, and stress ANOTHER Annex I country - both parties have commitments; that single word is the whole difference from CDM. Do not miss ADDITIONALITY: the reduction must be over and above what would have happened anyway - the same test applies to CDM. Answer in two parts, define JI first, then give the difference in one clean sentence, since the question asks for both.
Source: 2014
📖 §10.10 Emissions trading / carbon market

39. Explain emissions trading under the Kyoto Protocol.

Model answer: Emissions trading allows countries that have emission units to spare - emissions permitted to them but not 'used' - to sell this excess capacity to countries that are over their targets. It is also known as carbon trading, since carbon dioxide is the principal greenhouse gas. Carbon is now tracked and traded like any other commodity, in what is called the 'carbon market.' The mechanism helps stimulate green investment and lets Parties meet their emission targets economically, ensuring emissions are cut where it costs least to do so. It supplements, rather than replaces, direct national actions such as conserving fossil fuel.
The logic to write: a country under its cap has "spare units" it is allowed but has not used, and it can sell them to a country over its target. Give the alternative names - carbon trading, carbon market - because CO2 is the main gas and is traded like any commodity. The economic point earns the last mark: emissions get cut wherever it is cheapest. Common mistake: saying trading replaces domestic action - the book says it SUPPLEMENTS it.
Source: 2014
📖 §10.11 CDM project cycle (PIN, PDD, DOE, DNA, CDM-EB)

40. Describe the main stages of the CDM project cycle.

Model answer: The CDM project cycle stages are: (1) Project Preparation - identification and feasibility study, establishing the project is real, measurable and additional. (2) Development of the Project Idea Note (PIN) - about five pages giving indicative information; informs the host-country Designated National Authority (DNA) and gets feedback. (3) Development of the Project Design Document (PDD) - the key, mandatory document containing baseline methodology, monitoring plan and CER estimate. (4) Submission of PDD with host-country approval to a Designated Operational Entity (DOE) for validation (PDD made public for 30 days). (5) Validation, then registration with the CDM Executive Board (CDM-EB). (6) Implementation, yearly monitoring, verification and certification by the DOE, leading to issuance of CERs.
Answer as a numbered flow, not a paragraph: Preparation -> PIN -> PDD -> host-country approval (DNA) -> validation by DOE (PDD public for 30 days) -> registration by CDM-EB -> implementation -> monitoring -> verification/certification -> CER issued. Learn who does what: DNA approves, DOE validates and verifies, CDM-EB registers and issues. Numbers worth adding: PIN about 5 pages, PDD public for 30 days, registration final within about eight weeks.
Source: 2014
📖 §10.11 PIN and PDD documents

41. Distinguish between the Project Idea Note (PIN) and the Project Design Document (PDD) in a CDM project.

Model answer: The Project Idea Note (PIN) is about five pages giving indicative information on the type and size of the project, its location, the anticipated GHG reduction versus the 'business-as-usual' scenario, the suggested crediting lifetime, the suggested CER price (US$/tCO2e), the financial structuring, and other socio-economic/environmental benefits. The PIN is NOT required for a CDM application but helps inform the host-country DNA and gauge buyer interest. The Project Design Document (PDD) is the KEY, MANDATORY document of the CDM cycle. It contains the general project description, baseline setting, project duration/crediting period, monitoring plan, estimation of GHG emission reductions, environmental impacts and stakeholders' comments, and is submitted to a DOE for validation and to the CDM-EB for registration.
One-line difference to lead with: PIN is OPTIONAL and indicative (about 5 pages), PDD is the KEY MANDATORY document. Hook: "PIN = pitch, PDD = proof." The PDD is where baseline, crediting period, monitoring plan, emission-reduction estimate, environmental impacts and stakeholder comments live - the monitoring plan and baseline are the items most often missed. Remember the PIN goes to the host DNA and to gauge buyer interest; the PDD goes to the DOE and CDM-EB.
Source: 2014
📖 §10.11 DOE, DNA, CDM-EB roles & validation vs verification

42. Distinguish validation from verification in CDM, and state the roles of DOE, DNA and CDM-EB.

Model answer: Validation occurs at the OUTSET of a project: the Designated Operational Entity (DOE) evaluates the PDD and associated documents against CDM requirements (after making the PDD public for 30 days) to confirm the information and assumptions are accurate and reasonable. Verification is the periodic, ex-post review during the OPERATION of the project - the DOE checks that monitored GHG emission reductions actually occurred per the monitoring plan, carried out annually; verified reductions form the basis for CERs. Roles: DOE - validates and verifies; DNA (Designated National Authority) - host-country approval (in India, the Ministry of Environment & Forest, MoE&F); CDM-EB (CDM Executive Board) - formally registers the validated project (final after up to eight weeks).
Time separates the two words: VALIDATION happens at the START (is the plan sound?), VERIFICATION happens DURING operation, every year (did the reductions really happen?). Both are done by the DOE - that catches students out, they assume different bodies. Hook: "Validate the plan, Verify the performance." Roles: DNA = host-country approval (in India the Ministry of Environment & Forest), CDM-EB = registration. Numbers: PDD public for 30 days, registration final in about eight weeks.
Source: 2014
📖 §10.11 CDM small-scale fast-track types

43. What are the three small-scale CDM project types eligible for fast-track approval?

Model answer: To reduce high transaction costs for small projects, certain small-scale projects are eligible for CDM fast-track approval. The three small-scale project types are: Type I - renewable energy projects with a capacity of up to 15 MW; Type II - energy-efficiency projects which reduce energy consumption on the demand or supply side by up to 15 GWh/year (54 TJ) versus business-as-usual; Type III - other projects which reduce emissions and emit less than 15 kT CO2/year. Fast-tracking is justified because the normal CDM process is too costly for small projects, many small projects give significant local sustainable-development benefits, and small-scale technologies (solar, wind, fuel cells) are promising for the long term.
Every limit is a 15, only the unit changes - that is the whole memory trick: Type I renewable up to 15 MW, Type II energy efficiency up to 15 GWh/year (54 TJ), Type III other projects under 15 kT CO2/year. Keep the order I-II-III as renewable, efficiency, other. Add the reason for fast-tracking - normal CDM transaction costs are too high for small projects - because the question usually carries a "why" mark.
Source: 2014
📖 §10.11 CER 2% levy & crediting period

44. What is the 2% CER levy, and what are the CDM crediting-period options?

Model answer: The CERs generated by CDM projects are subject to a 2% levy, used to help particularly vulnerable developing countries adapt to the adverse effects of climate change. (Also, public funding for CDM projects must not divert official development assistance, ODA.) Regarding the crediting period - the duration for which a project generates CERs - a project can be valid either for one period of ten years only, or for up to three periods of seven years each, with revalidation of the project every seventh year. Monitoring continues for the entire crediting period (10 years, or 3x7 years).
Two separate facts, so use two headings. Levy: 2% of the CERs generated, used to help especially vulnerable developing countries ADAPT (not mitigate) - and public funding must not be diverted official development assistance (ODA). Crediting period: EITHER one fixed period of 10 years, OR up to 3 periods of 7 years each with revalidation every seventh year. Hook: "10 once, or 7 thrice." Monitoring runs for the whole crediting period.
Source: 2014
📖 §10.12 EU 20-20-20 targets

45. What are the EU '20-20-20' climate and energy targets for 2020?

Model answer: The EU 2020 Climate and Energy Package is a set of binding legislation to meet three key objectives by 2020, known as the '20-20-20' targets: (1) a 20% reduction in EU greenhouse-gas emissions from 1990 levels; (2) raising the share of EU energy consumption produced from renewable resources to 20%; and (3) a 20% improvement in the EU's energy efficiency. These represent an integrated approach to combat climate change, increase energy security and strengthen competitiveness. The targets were set by EU leaders in March 2007 and enacted through the climate and energy package in 2009.
The name gives you the answer - three 20s by 2020: emissions -20% (from 1990 levels), renewables 20% of energy consumption, energy efficiency improved 20%. The trap is the baseline: the 20% CUT is measured against 1990, while the other two are simply shares/improvements by 2020. Add that they are BINDING legislation, set by EU leaders in 2007 and enacted in 2009, and that the aim is climate + energy security + competitiveness.
Source: 2014
📖 §10.12 EU ETS cap-and-trade

46. Explain how the EU Emissions Trading System (EU ETS) 'cap and trade' works.

Model answer: The EU Emissions Trading System (EU ETS) is a policy tool to cut industrial GHG emissions cost-effectively; it covers over 11,000 power stations and industrial plants in 31 countries plus airlines. It works on the 'cap and trade' principle: a cap (limit) is set on the total amount of certain greenhouse gases that installations may emit, and the cap is reduced over time so total emissions fall. Within the cap, companies receive or buy emission allowances and can trade them with one another. Each year a company must surrender enough allowances to cover its emissions or face heavy fines; if it reduces emissions it can keep or sell spare allowances. This ensures emissions are cut where it costs least.
Explain "cap and trade" in the book's order: a cap is fixed on total emissions, the cap is LOWERED each year so emissions must fall, companies get or buy allowances within it and may trade them, and each year they must surrender enough allowances or pay heavy fines. Cut emissions and you keep or sell the spare allowances - that is the incentive. Scale figures worth quoting: over 11,000 power stations and industrial plants in 31 countries, plus airlines.
Source: 2014
📖 §10.13 Sustainable development (Brundtland 1987)

47. Define sustainable development and state its three basic objectives.

Model answer: According to the Brundtland Commission Report 'Our Common Future' (1987), sustainable development is 'meeting the needs of the present without compromising the ability of future generations to meet their own needs.' It can also be described as 'living on the Earth's income rather than eroding its capital' and keeping consumption of renewable resources within the limits of their replenishment. Sustainable development encompasses three basic and inter-related objectives (the three pillars): (1) Economic security and prosperity, (2) Social development and advancement, and (3) Environmental sustainability.
Reproduce the definition word for word - "meeting the needs of the present without compromising the ability of future generations to meet their own needs" - and attribute it: Brundtland Commission report "Our Common Future", 1987. The neat supporting line is "living on the Earth's income rather than eroding its capital". Then give the three pillars: economic security/prosperity, social development, environmental sustainability. Common mistake: writing only the environmental pillar - all three are needed.
Source: 2014
📖 §Acronym full forms

48. Give the full forms of: GWP, GHG, CFC, HFC, PFC, SF6, CCS, CDM, JI, CER, ERU, IPCC, UNFCCC, COP, DOE, DNA.

Model answer: GWP - Global Warming Potential; GHG - Greenhouse Gas; CFC - Chlorofluorocarbon; HFC - Hydrofluorocarbon; PFC - Perfluorocarbon; SF6 - Sulphur Hexafluoride; CCS - Carbon Capture and Storage; CDM - Clean Development Mechanism; JI - Joint Implementation; CER - Certified Emission Reduction; ERU - Emission Reduction Unit; IPCC - Intergovernmental Panel on Climate Change; UNFCCC - United Nations Framework Convention on Climate Change; COP - Conference of Parties; DOE - Designated Operational Entity; DNA - Designated National Authority. (Also: CDM-EB - CDM Executive Board; PIN - Project Idea Note; PDD - Project Design Document; ODS - Ozone Depleting Substances; EnMS - Energy Management System.)
Learn these in linked pairs so one recalls the other: CDM->CER and JI->ERU (both credits = 1 tonne CO2); PIN->PDD (idea note then design document); DOE->validates/verifies while DNA->host-country approval and CDM-EB->registers. Gases group as CFC/HFC/PFC/SF6. Trap in the letters: DNA here is Designated National AUTHORITY (a government body) and DOE is Designated Operational ENTITY (an auditor) - do not swap them. Write full forms only; no explanation is asked, so do not waste time.
Source: 2014
📖 §CO2 from carbon (44/12 = 3.67)

49. How much CO2 is produced from the complete combustion of 1 kg of carbon, and why?

Model answer: Complete combustion of carbon follows the reaction C + O2 = CO2. The molar mass of carbon (C) is 12 and that of carbon dioxide (CO2) is 44. Therefore 12 kg of carbon produces 44 kg of CO2, so 1 kg of carbon produces 44/12 = 3.67 kg of CO2. In general, a fuel containing C kg of carbon yields C x 3.67 kg of CO2 on complete combustion. This factor is used to estimate CO2 emissions from the carbon content of a fuel.
Start from the equation C + O2 = CO2, then the molecular weights: 12 for carbon, 44 for CO2 (12 + 16 + 16). So 12 kg carbon gives 44 kg CO2, and 1 kg gives 44/12 = 3.67 kg. Learn 3.67 as a ready factor - the examiner reuses it in numericals: CO2 = carbon in fuel x 3.67. Common mistake: multiplying the whole fuel mass by 3.67 - it applies only to the CARBON content of the fuel.
Source: 2014
📖 §S-1 CO2-avoidance calculation (110 MW R&M)

50. A renovation and modernization (R&M) of a 110 MW coal-fired thermal power plant raised efficiency from 28% to 32%. Specific coal consumption was 0.7 kg/kWh before R&M. For 7000 hours/year (coal quality unchanged), calculate (a) coal savings per year and (b) CO2 avoidance in tons/year if the emission factor is 1.53 kg CO2/kg coal.

Model answer: Annual generation = 110 MW x 1000 x 7000 h = 770 x 10^6 kWh/year. Specific coal consumption is inversely proportional to efficiency. After R&M: new SCC = 0.7 x (28/32) = 0.6125 kg/kWh. Coal saved per kWh = 0.7 - 0.6125 = 0.0875 kg/kWh. (a) Annual coal saving = 0.0875 x 770 x 10^6 = 6.7375 x 10^7 kg = approximately 67,375 tonnes/year. (b) CO2 avoided = coal saved x emission factor = 67,375,000 kg x 1.53 = 1.0308 x 10^8 kg = approximately 1,03,084 tonnes CO2/year.
The key idea is that specific coal consumption is INVERSELY proportional to efficiency, so new SCC = 0.7 x (28/32), NOT x (32/28) - flipping this ratio is the usual mistake. Work in the fixed order: generation (MW x 1000 x hours) -> SCC saved per kWh -> annual coal saved -> multiply by the emission factor. CO2 avoided = fuel saved x emission factor. Watch units: convert kg to tonnes by dividing by 1000 at the end, and write kg or tonnes at every step.
Source: 2014
📖 §S-1 variant CO2-avoidance (1 MW R&M)

51. An R&M program of a 1 MW coal-fired thermal power plant raised operating efficiency from 28% to 32%. Specific coal consumption was 0.7 kg/kWh before R&M. For 7000 hours/year (coal quality unchanged), calculate (a) coal saving per year in tonnes; (b) CO2 avoidance in tons/year if the emission factor is 1.3 kg CO2/kg coal.

Model answer: Annual generation = 1 MW × 1000 kW/MW × 7000 h = 7 × 10^6 kWh/year. Specific coal consumption varies inversely with efficiency, so after R&M: SCC = 0.7 × (28/32) = 0.6125 kg/kWh. Coal saved per kWh = 0.7 − 0.6125 = 0.0875 kg/kWh. (a) Annual coal saving = 0.0875 × 7 × 10^6 = 612,500 kg = about 612.5 tonnes/year. (b) CO2 avoided = coal saved × emission factor = 612,500 × 1.3 = 796,250 kg = about 796 tonnes CO2/year. (If the rounded SCC saving of 0.09 kg/kWh is used, the answer becomes ~630 tonnes coal and ~819 tonnes CO2 — both are accepted; show the method.)
Same method as book S-1 but plant rated 1 MW and emission factor 1.3; printed exam solution rounds SCC saving, giving about 819 T/yr.
Source: 2024
📖 §CO2 emission per kWh from coal carbon content

52. A thermal power plant uses 0.72 kg of coal to generate one kWh of electricity. If the coal contains 38% carbon by weight, calculate the CO2 emission per kWh under complete combustion.

Model answer: Carbon present in coal per kWh = 0.72 x 38/100 = 0.2736 kg. By the reaction C + O2 = CO2, 1 kg of carbon produces 44/12 kg of CO2 under complete combustion. Therefore CO2 generated per kWh = 0.2736 x 44/12 = 1.0032 kg CO2/kWh.
Two steps only: first find the carbon actually burnt (0.72 x 38/100 = 0.2736 kg), then convert carbon to CO2 with 44/12 = 3.67. Never apply 44/12 to the full 0.72 kg of coal - that is the standard mark-loser, since only the carbon fraction becomes CO2. A good sanity check: the answer per kWh should come out near 1 kg CO2/kWh for Indian coal, and it does (1.0032).
Source: 2014
📖 §10.13 Sustainable development applied to energy

53. What considerations does sustainable development apply to energy and environment?

Model answer: Applied to energy and environment, sustainable development considers: (1) Inputs - fuels, energy sources, land and raw materials that are non-renewable should be used up only as far as they can be substituted in future. (2) Where inputs are renewable, they should be used up only at a rate within which they can be renewed. (3) Outputs - in production and consumption - should not overstrain ecosystems or the assimilation capacity of the ecosphere. The aim is ways of living and working that let all people lead healthy, fulfilling, economically secure lives without destroying the environment or endangering future welfare.
Structure the answer as INPUTS then OUTPUTS - that framing itself earns marks. Inputs: non-renewables only as fast as substitutes can be found; renewables only as fast as they renew. Outputs: waste and emissions must stay within what ecosystems and the ecosphere can absorb. Close with the human aim - healthy, fulfilling, economically secure lives without destroying the environment. Do not repeat the Brundtland definition alone; this question wants it APPLIED to energy.
Source: 2014
📖 §International framework timeline

54. Outline the sequence of the international climate-change framework (IPCC, UNFCCC, COP-3/Kyoto).

Model answer: The international framework developed in sequence: (1) IPCC - Intergovernmental Panel on Climate Change, formed in 1988 by the WMO and the UN to review climate data and report findings; its 1995 report established a discernible human influence on climate. (2) UNFCCC - United Nations Framework Convention on Climate Change, signed at the Rio Earth Summit in June 1992 by over 160 countries, in force from 1994, to stabilise GHG concentrations and prevent dangerous anthropogenic interference. (3) COP - the annual Conference of Parties, the supreme body of the UNFCCC; COP-3 in 1997 produced the Kyoto Protocol with binding targets (average -5% vs 1990 levels) for Annex I countries over 2008-2012, in force from 2005.
Learn it as a date chain: 1988 IPCC (science) -> 1992 UNFCCC signed at Rio (framework, in force 1994) -> annual COPs -> COP-3 in 1997 = Kyoto Protocol (binding, in force 2005). Hook: "Science, then framework, then binding targets." Kyoto details to attach: average 5% cut against 1990 levels, Annex I countries, period 2008-2012. Common mistake: swapping 1992 (UNFCCC) with 1997 (Kyoto) - the Convention always comes before its Protocol.
Source: 2014
📖 §10.10 The Kyoto Protocol — Table 10.2 Emission targets for Annex I countries

55. What were the individual Kyoto emission targets for selected Annex I countries (vs 1990 levels)?

Model answer: Kyoto Protocol individual targets for 1990-2008/2012 (Table 10.2): EU-15 and most European states (Bulgaria, Czech Republic, Estonia, Latvia, Liechtenstein, Lithuania, Monaco, Romania, Slovakia, Slovenia, Switzerland) = -8%; United States = -7% (but the US indicated it would not ratify); Canada, Hungary, Japan, Poland = -6%; Croatia = -5%; New Zealand, Russian Federation, Ukraine = 0% (stabilise); Norway = +1%; Australia = +8%. The EU-15 redistribute their targets among themselves under a scheme called a 'bubble.' The average commitment across developed countries is about -5%.
Confirmed vs Book-1 §10.10 Table 10.2 — every figure below is checked line-by-line against the printed table; framed as an exam-style question rather than a chapter-end question, hence ai=true.
Source: AI practice
📖 §10.11 Certification & issuance of CER

56. How are CERs certified and issued, and why is current CER demand low?

Model answer: After verification, the Designated Operational Entity (operational entity) provides a certification report giving written assurance that the project achieved the verified reduction. Unless a project participant or three Executive Board members request a review within 15 days, the CERs are issued; CERs are based on actual reductions during the monitored period (usually one year). Current demand for CERs is low because a number of Annex I countries are not participating in the Kyoto Protocol or its second commitment period, and about two-thirds of the EU ETS quantitative limit for use of ERUs and CERs has already been used, so confirmed demand is far below the mechanism's supply capacity.
Answer in order: verification -> certification report (written assurance) -> 15-day review window -> CERs issued. The 15 days is the number to memorise, and note who can ask for a review - a project participant or three Executive Board members. CERs are based on ACTUAL monitored reductions, usually over one year. For the low-demand part, give both reasons: several Annex I countries are out of Kyoto/its second period, and about two-thirds of the EU ETS limit for CER/ERU use is already consumed - so supply far exceeds confirmed demand.
Source: 2014

Long questions (10 marks) — 13

📖 §BEE 2014 Guidebook, Ch-10 End Questions, Long Q L-1 (Sec 10.5, p.241-242)

1. Explain the greenhouse effect and the enhanced greenhouse effect. Distinguish between the natural and the human-enhanced process. (10 marks)

Model answer: 1. The greenhouse effect is a NATURAL process. The earth is surrounded by a blanket of gases (greenhouse gases) such as water vapour, carbon dioxide, methane and nitrous oxide. 2. The earth's atmosphere lets short-wave solar radiation from the sun pass through relatively unimpeded and reach the surface. 3. The warmed earth re-emits energy as long-wave infrared radiation. Greenhouse gases absorb this outgoing infrared and re-radiate part of it back downwards, trapping heat much as glass traps heat in a greenhouse. 4. This sets up an energy balance that keeps the earth's average surface temperature at a tolerable +15 degC. Without naturally occurring greenhouse gases the average temperature would be a cold -18 degC, and life as we know it would not be possible. 5. The ENHANCED (human) greenhouse effect is the intensification of this natural effect by the rising concentration of greenhouse gases from human activity. 6. Main causes: burning of fossil fuels (coal, oil, gas) which adds CO2, together with widespread deforestation over the past 200 years, plus methane, nitrous oxide, CFCs and ozone from industry and agriculture. 7. Water vapour, though a greenhouse gas, is not changing directly due to human activity; the gases directly increased by humans are CO2, CH4, N2O, CFCs and ozone. 8. Higher greenhouse-gas concentration means less heat escapes to space, so more heat is trapped and the atmosphere warms (global warming and climate change). 9. Evidence: the earth's average temperature has risen about 0.75 degC since 1880 due to human emissions. 10. Consequences of the enhanced effect: melting ice caps and glaciers, rising sea levels, altered rainfall, extreme weather, heat waves, loss of biodiversity and threats to food and freshwater supply.
Structure the answer as (i) natural effect = keeps earth at +15 degC vs -18 degC, mechanism of short-wave in / long-wave trapped; (ii) enhanced effect = human addition of GHGs (mainly CO2 from fossil fuels + deforestation) causing global warming. The two key temperatures (+15 and -18 degC) and the 0.75 degC rise since 1880 are high-value recall points.
Source: unknown
📖 §BEE 2014 Guidebook, Ch-10 End Questions, Long Q L-2 (Sec 10.9-10.10, p.249-251)

2. Explain the Conference of Parties (COP): its purpose and its implications for developed and developing countries. (10 marks)

Model answer: 1. COP stands for Conference of the Parties. It is the supreme body of the United Nations Framework Convention on Climate Change (UNFCCC). 2. It consists of all countries that have joined (ratified) the Convention, referred to as Parties to the Convention. 3. The COP meets ANNUALLY to promote and review the implementation of the Convention and any related legal instruments (such as the Kyoto Protocol). Meetings held between COPs are called intersessional meetings. 4. Purpose: to assess progress in dealing with climate change, negotiate and adopt commitments/protocols, and develop mechanisms (CDM, emissions trading, finance and technology transfer) to combat climate change. 5. The landmark meeting is COP-3 (1997), which produced the Kyoto Protocol, setting legally binding emission targets for developed (Annex I) countries for the six major greenhouse gases, to be met over 2008-2012. 6. The whole framework rests on the principle of COMMON BUT DIFFERENTIATED RESPONSIBILITIES, because developed countries are principally responsible for present GHG levels after 150+ years of industrial activity. 7. Implications for DEVELOPED (industrialized/Annex I) countries: they must take the lead, accept binding emission-reduction targets (Kyoto average -5% vs 1990 levels), and provide financial resources and transfer of environment-friendly technology to developing countries. 8. Implications for DEVELOPING (non-Annex I) countries: they are not bound by mandatory reduction targets but are recognized as especially vulnerable to climate impacts. 9. Developing countries participate through voluntary action and mechanisms such as the Clean Development Mechanism (CDM), hosting emission-reduction projects financed by developed countries. 10. This lets developing nations earn revenue and gain clean technology while contributing to global mitigation and sustainable development.
COP = supreme annual body of UNFCCC. Anchor the answer on COP-3 -> Kyoto Protocol and the principle of common but differentiated responsibilities. Split the 'implications' clearly: developed = lead + binding targets + finance/technology; developing = no binding target + benefit via CDM.
Source: unknown
📖 §BEE 2014 Guidebook, Ch-10 End Questions, Short Q S-1 (p.260) - full worked CO2-avoidance numerical

3. A renovation and modernization (R&M) programme of a 110 MW coal-fired thermal power plant raised the operating efficiency from 28% to 32%. The specific coal consumption before R&M was 0.7 kg/kWh. For 7000 hours of operation per year, and assuming coal quality is unchanged, calculate (a) the coal saving per year, and (b) the avoidance of CO2 emission in tonnes/year, if the emission factor is 1.53 kg CO2/kg coal. (10 marks)

Model answer: GIVEN: Capacity = 110 MW; hours = 7000 h/yr; specific coal consumption before R&M = 0.7 kg/kWh; efficiency 28% -> 32%; emission factor = 1.53 kg CO2/kg coal. Step 1 - Annual generation: = 110 MW x 1000 kW/MW x 7000 h = 770,000,000 kWh/yr = 770 x 10^6 kWh/yr. Step 2 - Coal consumption BEFORE R&M: = 770 x 10^6 kWh x 0.7 kg/kWh = 539 x 10^6 kg = 5,39,000 tonnes/yr. Step 3 - Specific coal consumption AFTER R&M: Specific coal consumption is inversely proportional to efficiency, so it falls in the ratio (old eff / new eff) = 28/32. New SCC = 0.7 x (28/32) = 0.7 x 0.875 = 0.6125 kg/kWh. Step 4 - Coal consumption AFTER R&M: = 770 x 10^6 kWh x 0.6125 kg/kWh = 471.625 x 10^6 kg = 4,71,625 tonnes/yr. (a) COAL SAVING per year: = 5,39,000 - 4,71,625 = 67,375 tonnes/yr. (b) CO2 AVOIDED per year = coal saved x emission factor: = 67,375 tonnes x 1.53 = 1,03,084 tonnes CO2/yr (approx 1.03 x 10^5 T/yr). ANSWER: (a) about 67,375 tonnes of coal saved per year; (b) about 1,03,084 tonnes of CO2 avoided per year.
Core logic: higher efficiency -> less coal per unit of electricity, so multiply the old specific coal consumption by (old efficiency / new efficiency) = 28/32. Coal saved = (SCC_before - SCC_after) x annual generation. Then CO2 avoided = coal saved x emission factor (1.53 kg CO2/kg coal). If instead carbon content were given, multiply by 44/12 = 3.67 to convert carbon to CO2.
Source: unknown
📖 §10.5 Greenhouse gases & GWP (Table 10.1) + §10.10 Kyoto targets — Book-1 pp.243–245, 251

4. Name the six major greenhouse gases covered under the Kyoto Protocol and explain the concept of Global Warming Potential (GWP), giving their relative GWP and atmospheric lifetimes. (10 marks)

Model answer: 1. The Kyoto Protocol targets cover SIX main greenhouse gases: Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6). 2. Different greenhouse gases differ widely in how long they stay in the atmosphere and how much heat they trap; some are 140 to 23,900 times more potent than CO2 over a 100-year period. 3. Global Warming Potential (GWP) is used to rank them. GWP is the ratio of the global warming (radiative forcing) caused by one unit mass of a greenhouse gas to that caused by one unit mass of CO2 over a chosen period (usually 100 years). 4. Thus GWP measures the 'potential for global warming per unit mass relative to CO2', with CO2 taken as the reference (GWP = 1). 5. GWP takes into account both the absorption strength of the molecule and its atmospheric lifetime. The higher the GWP, the larger the infrared absorption and the longer the lifetime. 6. Indicative values (Table 10.1): CO2 = 1 (life 5-200 yr); CH4 = 23 (life 12 yr); N2O = 300 (life 114 yr); CFC/HFC-type = 4000-8000 (life 5-100 yr); PFC (perfluoromethane) = 5700 (life ~50,000 yr - the longest); SF6 = 22,000 (the HIGHEST GWP; life 3200 yr). 7. Example: methane has GWP 23, meaning it is 23 times more powerful than CO2 as a greenhouse gas per unit mass. 8. SF6 is the most potent greenhouse gas (GWP 22,000) and PFCs have the longest atmospheric life (~50,000 years); ozone has the shortest (days/weeks). 9. Even though the potent gases are present in very small amounts (ppt levels), their enormous heat-holding potential makes them a serious addition to global warming. 10. CO2 remains the most important overall because of its abundance, contributing about 60% of the enhanced greenhouse effect.
Two parts: (i) list the 6 Kyoto gases - CO2, CH4, N2O, HFCs, PFCs, SF6; (ii) define GWP as radiative forcing relative to CO2 (=1) over 100 years, then quote the table. Memory hooks: SF6 = highest GWP (22,000); PFC = longest life (~50,000 yr); CH4 = 23; N2O = 300.
Source: unknown
📖 §10.4 Ozone layer depletion — chemistry of ozone depletion (Fig 10.5), Book-1 pp.238–240

5. Explain the ozone layer, the role of chlorofluorocarbons (CFCs) in its depletion, and describe step by step the catalytic mechanism by which CFCs destroy ozone. (10 marks)

Model answer: 1. The ozone layer is a thin layer of ozone (O3) in the STRATOSPHERE, extending about 10-50 km above the earth. 2. It is highly beneficial to life because it blocks the sun's harmful ultraviolet (UV-B) radiation from reaching the earth's surface. 3. Naturally, ozone is formed when oxygen absorbs UV of wavelength < 240 nm, and is destroyed when it absorbs UV of wavelength > 290 nm, giving a balanced equilibrium. 4. Depletion is caused mainly by man-made chlorine and bromine compounds - chiefly chlorofluorocarbons (CFCs) once used in refrigerators and air-conditioners, plus HCFCs, carbon tetrachloride, methyl chloroform (chlorine) and halons/methyl bromide (bromine). 5. CFCs are very unreactive, so they survive long enough to diffuse up into the stratosphere. CATALYTIC MECHANISM (step by step): 6. Step 1: Strong UV radiation strikes a CFC (CFCl3) molecule and breaks a carbon-chlorine bond, releasing a free chlorine (Cl) atom. 7. Step 2: The chlorine atom attacks an ozone (O3) molecule, breaking it apart. It takes one oxygen atom, forming chlorine monoxide (ClO) and leaving an ordinary oxygen molecule (O2). 8. Step 3: A free oxygen atom then strikes the chlorine monoxide (ClO), pulling away its oxygen to form O2 and releasing the chlorine atom again. 9. Step 4: The released (free) chlorine atom is now free to repeat the process and destroy more ozone - this is why it is called a catalytic (chain) reaction: the chlorine is regenerated, not consumed. 10. It is estimated that a single chlorine atom can destroy from 10,000 up to 100,000 ozone molecules before it is finally removed from the stratosphere. Effects include skin cancer, eye disease, damage to plants, aquatic ecosystems and materials. Counter-measure: the Montreal Protocol phases out ozone-depleting substances, taxes them, promotes HCFC/HFC substitutes and recycling of CFCs and halons. 11. Counter-measures (§10.4): the Montreal Protocol — which this 2014 guidebook states was signed in 1974 (write 1974 in the exam, not the real-world 1987) — phases out ozone-depleting substances; supported by a tax on ODS use, ozone-friendly substitutes HCFC and HFC (lower ozone-depleting potential and shorter life), and recycling of CFCs and halons.
Emphasise that it is the Cl (and Br) ATOM, not the intact CFC molecule, that destroys ozone, and that chlorine is regenerated each cycle (catalytic) so one atom destroys 10,000-100,000 O3 molecules. Sequence: UV breaks C-Cl bond -> Cl + O3 -> ClO + O2 -> ClO + O -> Cl + O2 -> repeat. Location = stratosphere; blocks UV-B; fix = Montreal Protocol.
Source: unknown
📖 §10.10 The Kyoto Protocol Mechanisms — Emissions Trading, CDM, JI (Book-1 pp.251–253)

6. Describe the three flexibility (market-based) mechanisms of the Kyoto Protocol - Emissions Trading, Clean Development Mechanism and Joint Implementation - and explain the principle of common but differentiated responsibilities. (10 marks)

Model answer: 1. Under the Kyoto Protocol, Annex I countries accepted binding targets (assigned amounts) for limiting GHG emissions over 2008-2012, to be met mainly through national measures. 2. To give flexibility in how targets are met economically, the Protocol offers THREE market-based mechanisms; they supplement, not replace, direct domestic action. 3. (i) EMISSIONS TRADING (carbon trading): a country that has spare emission units (permitted but not used) can SELL this excess capacity to a country that is over its target. 4. Carbon dioxide, the principal greenhouse gas, is thus tracked and traded like any other commodity - this is the 'carbon market'. 5. (ii) CLEAN DEVELOPMENT MECHANISM (CDM): allows an Annex I country with a commitment to implement an emission-reduction project in a DEVELOPING (non-Annex I) country. 6. Such projects earn saleable Certified Emission Reduction (CER) credits, each equal to one tonne of CO2, which count towards the developed country's Kyoto target. Most CDM projects are renewable energy, followed by waste handling. 7. CDM delivers sustainable development and emission cuts in the host country while giving industrialized countries flexibility. 8. (iii) JOINT IMPLEMENTATION (JI): allows an Annex I country to earn Emission Reduction Units (ERUs), each equal to one tonne of CO2, from an emission-reduction or removal project in ANOTHER Annex I country. 9. Key difference: JI is between two committed (Annex I) countries, whereas CDM is between one committed country and one non-committed (developing) country. JI gives the host foreign investment and technology transfer. 10. COMMON BUT DIFFERENTIATED RESPONSIBILITIES: because developed nations are principally responsible for present GHG levels after 150+ years of industrial activity, the Protocol places a heavier duty on them to reduce emissions and support developing countries, while developing countries bear no binding target.
Keep the three mechanisms crisp: Emissions Trading = sell spare units (carbon market); CDM = Annex I funds project in developing country -> earns CER (1 t CO2); JI = project between two Annex I countries -> earns ERU (1 t CO2). Nail the CDM-vs-JI distinction and close with common-but-differentiated responsibilities.
Source: unknown
📖 §10.11 CDM methodology and procedure — CDM project cycle, Fig 10.9 (Book-1 pp.253–257)

7. Describe the project cycle of the Clean Development Mechanism (CDM), explaining the roles of the PIN, PDD, DOE, DNA and CDM Executive Board. (10 marks)

Model answer: 1. Project Preparation: the first step is identification and formulation of a potential CDM project (project identification + feasibility study), comparing it against approved methodologies with UNFCCC. This establishes that the project is real, measurable and additional. 2. Project Idea Note (PIN): a short document of about five pages giving indicative information - type and size, location, anticipated GHG reduction versus business-as-usual, crediting lifetime, suggested CER price and financing. Optional, but it informs the host-country DNA and tests buyer interest. 3. Project Design Document (PDD): the KEY and MANDATORY document. It contains the general project description, the baseline methodology and baseline scenario (used to calculate the CERs), the crediting period, the monitoring plan, the estimate of GHG reductions, environmental impacts and stakeholder comments. 4. Host Country Approval - DNA: the completed PDD is submitted to the Designated National Authority (DNA) of the host country for approval. The DNA confirms the project meets the country's sustainable development criteria. In India the DNA/National CDM Authority is the Ministry of Environment & Forest (MoE&F). 5. Validation - DOE: the PDD and host-country approval are submitted to an accredited Designated Operational Entity (DOE). The DOE makes the PDD publicly available for comments for 30 days, then validates it against CDM requirements. Validation occurs at the OUTSET of a project. 6. Registration - CDM Executive Board (CDM-EB): the DOE submits the PDD, host-country approval and validation report to the CDM Executive Board, which formally registers (accepts) the project. Registration is final within about eight weeks unless a review is requested. 7. Implementation & Monitoring: once registered, the project is implemented; participants monitor performance per the validated monitoring plan for the whole crediting period, preparing a monitoring report with an estimate of CERs (watching for leakage). 8. Verification & Certification - DOE: verification is the periodic (annual) ex-post review by the DOE confirming the monitored emission reductions actually occurred. The DOE then issues a certification report. 9. Issuance of CERs: unless a participant or three EB members request a review within 15 days, the CERs (each = 1 tonne CO2) are issued. A 2% levy on CERs funds adaptation in vulnerable developing countries. 10. Crediting period: a project may be credited for one period of ten years, or three periods of seven years each (with revalidation every seven years).
Sequence to remember: Prepare -> PIN -> PDD -> DNA approval -> DOE validation (30-day public comment) -> CDM-EB registration -> implement & monitor -> DOE verification/certification -> CER issuance. Role map: PIN=~5-page idea note; PDD=key mandatory doc; DNA=host-country approval (India=MoE&F); DOE=validates + verifies; CDM-EB=registers. Validation is at start, verification is annual during operation.
Source: unknown
📖 §10.13 Sustainable development (Book-1 p.259)

8. Define sustainable development as per the Brundtland Commission and explain its three basic inter-related objectives, with its application to energy and environment. (10 marks)

Model answer: 1. According to the Brundtland Commission Report 'Our Common Future' (1987), sustainable development is 'meeting the needs of the present without compromising the ability of future generations to meet their own needs'. 2. A fuller way of putting it: sustainable development means 'living on the Earth's income rather than eroding its capital', and 'keeping the consumption of renewable natural resources within the limits of their replenishment'. 3. It recognizes the intrinsic value of the natural world, meaning we hand down to future generations not only man-made wealth (buildings, roads, railways) but also natural wealth - clean water, good arable land, wildlife and forests. 4. Sustainable development rests on THREE basic and inter-related objectives: 5. (i) Economic security and prosperity. 6. (ii) Social development and advancement. 7. (iii) Environmental sustainability. 8. Together these demand ways of living and working that let all people lead healthy, fulfilling and economically secure lives without destroying the environment or endangering the future welfare of people and the planet. 9. Applied to energy and environment: non-renewable inputs (fossil fuels, land, raw materials) should be used only as far as they can be substituted in future. 10. Renewable resources should be used at a rate within which they can be renewed, and outputs of production and consumption must not overstrain ecosystems or the assimilation capacity of the ecosphere.
Two must-have elements: (i) the exact Brundtland (1987, 'Our Common Future') definition, and (ii) the three pillars - Economic, Social, Environmental. Add the 'living on the Earth's income not its capital' catch-phrase and the energy/environment application (non-renewables only if substitutable; renewables within replenishment rate).
Source: unknown
📖 §10.5 Carbon sequestration & natural carbon sinks (Book-1 p.243)

9. Explain carbon sequestration (carbon capture and storage) and the role of natural carbon sinks in mitigating CO2 emissions. (10 marks)

Model answer: 1. Carbon sequestration is the process of REMOVING CO2 from large point sources - such as power plants, oil refineries and industrial processes - so that it is not released into the atmosphere. 2. This is the basis of Carbon Capture and Storage (CCS): the captured CO2 is compressed and stored rather than emitted. 3. The CO2 is stored in geologic formations such as depleted oil and gas reservoirs, deep coal seams, or deep saline reservoirs (aquifers). 4. Sequestration is important because CO2 is the most abundant greenhouse gas (about 60% of the enhanced greenhouse effect) and is persistent, with an atmospheric lifetime of over 100 years. 5. Besides engineered storage, nature provides carbon SINKS that absorb CO2 from the atmosphere. 6. The oceans are a major carbon sink, containing about 50 times more carbon than the atmosphere. 7. Terrestrial biomass, including trees and grasses, stores about three times more CO2 than the atmosphere. 8. Together, ocean and terrestrial ecosystems absorb roughly HALF of the excess CO2 generated by human activities. 9. This is why deforestation is doubly harmful: burning felled trees releases stored carbon as CO2, and it also leaves fewer trees to take up atmospheric CO2, weakening the land sink. 10. Thus a mitigation strategy combines capturing and storing CO2 from point sources (CCS) with protecting and enhancing natural sinks such as forests and oceans.
Define sequestration as capture of CO2 from large POINT SOURCES (power plants, refineries, industry) + storage in geologic formations (depleted oil/gas reservoirs, deep coal seams, saline aquifers) = CCS. Then cover sinks: oceans = major sink (~50x atmosphere carbon), biomass/trees ~3x; together they absorb ~half of human excess CO2. Note the deforestation link.
Source: unknown
📖 §Sep 2021 Paper-1 (21st National Certification Exam, 25.09.2021)

10. Explain how snow gets formed and how the melting of mountain glaciers can be a serious problem. (10 marks)

Model answer: 1. Snow formation: at sub-zero temperatures, water vapour in the atmosphere changes directly to ice (deposition/freezing) forming tiny ice crystals. 2. These ice crystals grow and aggregate together and, when heavy enough, fall to the ground as snow. 3. On mountains, accumulated snow compacts over years into glaciers, which act as large natural stores of fresh water. 4. Global warming is accelerating the melting of these mountain glaciers; over the past 150 years most monitored glaciers have been shrinking, and many low-latitude glaciers are disappearing. 5. SHORT-TERM problem: rapid melting swells rivers, causing flooding and disruption of normal river flows and downstream ecosystems. 6. LONG-TERM problem: as glaciers shrink, summer/dry-season water flows drop sharply because the glacier reserve that fed the rivers is gone. 7. This threatens the dry-season supply of drinking water, irrigation water and hydropower for populations that depend on mountain watersheds (e.g. Himalayan-fed rivers). 8. Melting ice caps and glaciers add water to the oceans and contribute to rising sea levels, increasing coastal flooding. 9. Fresh water from melting ice can desalinate parts of the ocean, disturbing ocean currents and ecosystems that regulate climate. 10. Loss of the white, reflective ice surface reduces the earth's ability to reflect heat back into space, further warming the planet (a positive-feedback effect).
Two parts: (i) snow forms by deposition/freezing of atmospheric water vapour into ice crystals that aggregate and fall; (ii) glacier melt is serious both short-term (flooding, disrupted flows) and long-term (loss of dry-season water for drinking/irrigation/hydropower, sea-level rise, ecosystem and albedo effects). Book support: Sec 10.6 'Snow and Ice Melting'.
Source: unknown
📖 §Paper-1 Set A, December 2009 (9th National Certification Exam, 19.12.2009)

11. A 500 MW coal plant (conventional pulverized fuel) has a gross efficiency of 38%. The coal GCV = 4000 kCal/kg with 40% carbon content. A supercritical 500 MW unit with gross efficiency 40% replaces it, using the same coal. Calculate (a) the specific coal consumption after replacement, and (b) the amount of coal and CO2 saved per year if the plant operates 8000 hours. (10 marks)

Model answer: GIVEN: 500 MW; old efficiency 38%, new (supercritical) 40%; GCV = 4000 kcal/kg; carbon = 40%; 8000 h/yr. (Heat equivalent of electricity = 860 kcal/kWh.) (a) Specific coal consumption AFTER replacement (40% efficiency): Heat rate = 860 / 0.40 = 2150 kcal/kWh. Specific coal consumption = 2150 / 4000 = 0.5375 kg/kWh. (For comparison, BEFORE: heat rate = 860 / 0.38 = 2263.16 kcal/kWh; SCC = 2263.16 / 4000 = 0.5658 kg/kWh.) (b) Coal and CO2 saved per year: Saving in specific coal consumption = 0.5658 - 0.5375 = 0.0283 kg/kWh. Annual generation = 500 MW x 1000 x 8000 h = 4 x 10^9 kWh/yr. Coal saved = 0.0283 x 4 x 10^9 = 1.132 x 10^8 kg = about 1,13,160 tonnes/yr. CO2 saved = (44/12) x coal saved x carbon fraction = 3.667 x 1,13,160 x 0.40 = about 1,65,965 tonnes CO2/yr. ANSWER: (a) specific coal consumption after replacement = 0.5375 kg/kWh; (b) coal saved ~ 1,13,160 tonnes/yr and CO2 saved ~ 1,65,965 tonnes/yr.
Use 1 kWh = 860 kcal. SCC = (860/efficiency)/GCV. Compute SCC before and after, take the difference, multiply by annual generation for coal saved. Convert coal saved to CO2 using carbon fraction and 44/12 = 3.667 (mass CO2 = mass C x 44/12). Small rounding differences are acceptable.
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📖 §Paper-1, 23rd National Certification Exam, March 2023

12. A) A 2 MW captive power plant operates at a load factor of 90% and consumes 0.8 kg of coal per kWh; the coal contains 30% carbon. 20% of the coal is replaced by sawdust generated on-site (GCV 3600 kCal/kg). Calculate the CO2 emission and the reduction in CO2 due to the fuel substitution (treating on-site sawdust/biomass CO2 as carbon-neutral). B) A roof area is 1200 sq.ft with 20% shaded; 1 kW of rooftop solar needs 10 sq.m of shadow-free area. Calculate (I) the capacity that can be installed and (II) the annual energy generated at 5.5 sun-hours/day. (10 marks)

Model answer: PART A - CO2 from coal and reduction by sawdust substitution: Step 1 - Net generation = 2 MW x 0.90 (load factor) = 1.8 MW = 1800 kW = 1800 kWh per hour. Step 2 - Baseline (100% coal): coal = 1800 x 0.8 = 1440 kg/hr. CO2 (baseline) = coal x carbon fraction x 44/12 = 1440 x 0.30 x 3.667 = 1584 kg CO2/hr. Step 3 - After substituting 20% of coal with sawdust: coal now = 0.80 x 1440 = 1152 kg/hr. CO2 (from remaining coal) = 1152 x 0.30 x 3.667 = 1267.2 kg CO2/hr. (On-site sawdust is biomass and its combustion CO2 is treated as carbon-neutral, i.e. not a net addition.) Step 4 - Reduction in CO2 = 1584 - 1267.2 = 316.8 kg CO2/hr. Annual reduction = 316.8 x 8760 h = 2,775,168 kg = about 2775 tonnes CO2/yr. PART B - Rooftop solar: Shadow-free area = 1200 - (20% x 1200) = 1200 - 240 = 960 sq.ft. Convert to sq.m: 960 / 10.764 = 89.19 sq.m (1 sq.m = 10.764 sq.ft). (I) Capacity = 89.19 / 10 sq.m per kW = 8.92 kW. (II) Annual energy = capacity x sun-hours x days = 8.92 x 5.5 x 365 = about 17,900 kWh/yr. ANSWER: A) baseline CO2 ~1584 kg/hr, reduced to ~1267 kg/hr, a reduction of ~316.8 kg/hr (~2775 T/yr) from 20% biomass substitution. B) (I) ~8.92 kW installable; (II) ~17,900 kWh/yr.
Part A is a carbon-balance: CO2 = fuel x carbon fraction x 44/12. Replacing 20% coal with carbon-neutral biomass cuts coal CO2 by 20%, giving the reduction. (Some solutions instead account for a sawdust emission factor via its GCV; the transcript's original figures are ambiguous, so the clean carbon-neutral biomass method is used here.) Part B: usable area = roof - shading; convert sq.ft to sq.m (÷10.764); capacity = area/10; energy = kW x sun-hours x 365.
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📖 §Paper-1, 25th National Certification Exam, September 2025

13. In a chemical company, Natural Gas (NG) heats 15 kl/hr of water by 15 degC. The company plans to switch to steam available from a neighbouring industry. a) Work out the feasibility for 6000 annual operating hours. NG effective heat = 8500 kcal/m3, NG rate = Rs 55/m3, NG density = 0.717 kg/m3. Steam latent heat = 540 kcal/kg, steam rate = Rs 2.2/kg. b) Calculate the tonnes of CO2 for both options, given 0.2 kg CO2/kg steam and carbon in NG = 74%. (10 marks)

Model answer: Heat required = mass x sp. heat x rise = 15000 kg/hr x 1 x 15 = 2,25,000 kcal/hr. a) FEASIBILITY (annual cost comparison at 6000 h/yr): Natural Gas: NG needed = 2,25,000 / 8500 = 26.47 m3/hr. Annual NG = 26.47 x 6000 = 1,58,824 m3/yr. Annual NG cost = 1,58,824 x 55 = Rs 87.35 lakh/yr. Steam: steam needed = 2,25,000 / 540 = 416.67 kg/hr. Annual steam = 416.67 x 6000 = 25,00,000 kg/yr. Annual steam cost = 25,00,000 x 2.2 = Rs 55.00 lakh/yr. Saving by switching to steam = 87.35 - 55.00 = Rs 32.35 lakh/yr. Hence switching to steam is FEASIBLE (annual saving ~Rs 32.35 lakh). b) CO2 EMISSIONS for both options: Steam option: CO2 = 25,00,000 kg steam x 0.2 kg CO2/kg = 5,00,000 kg = 500 tonnes CO2/yr. NG option: mass of NG = 1,58,824 m3 x 0.717 kg/m3 = 1,13,876 kg/yr. CO2 = mass x carbon fraction x 44/12 = 1,13,876 x 0.74 x 3.667 = 3,09,000 kg = about 309 tonnes CO2/yr. ANSWER: a) Steam is cheaper by about Rs 32.35 lakh/yr, so the switch is feasible. b) CO2 ~ 500 T/yr (steam) vs ~ 309 T/yr (NG).
First find heat load (m x Cp x dT = 2,25,000 kcal/hr). Fuel/steam quantity = heat / (calorific value or latent heat); annual cost = quantity x rate x hours. Steam saves ~Rs 32.35 lakh/yr. For CO2: steam uses the given factor (0.2 kg/kg); NG uses mass (volume x density) x carbon fraction x 44/12. Note the switch cuts cost but the imported-steam CO2 (500 T) exceeds the NG CO2 (309 T) on a direct-combustion basis.
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