GATE — Environmental Science and Engineering (ES) · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersCounting greenhouse gases for nations, organisations, farms and products: IPCC inventory guidelines, the GHG Protocol corporate and Scope 3 standards, land-sector guidance, ISO 14064, emission factors and tiers, and science-based targets.
In the exams: GARP SCR 'Transition Planning and Carbon Reporting'; ISO 14064 verifier courses; sustainability reporting roles; GATE ES Section 9
GATE -- Environmental Science and Engineering (ES)
Section 8 (GHGs, GWP, climate change) and Section 9 (environmental management, ISO 14000 family, LCA): GWP-weighted CO2e conversion, C-to-CO2 arithmetic, ISO 14064 parts and their purposes, and simple Tier 1 calculations, often as numerical-answer items.
How our questions for GATE spread across the units of Carbon Accounting & Greenhouse Gas Inventories. Difficulty: 8 easy, 8 medium, 4 hard.
| Tier 1, 2 and 3 methods and emission factors | 5 | |
| Why and how GHGs are accounted; CO2-equivalence | 3 | |
| ISO 14064 parts 1–3: quantification and verification | 3 | |
| IPCC Guidelines for National GHG Inventories and the AFOLU volume | 2 | |
| Data quality, uncertainty and materiality | 2 | |
| Scope 3 categories and supply-chain emissions | 1 | |
| Land-sector and removals accounting for companies | 1 | |
| Farm-level carbon calculators | 1 | |
| Base years, recalculation and targets | 1 | |
| Verification and assurance of GHG statements | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A farm emits 50 t CO2, 10 t CH4 and 2 t N2O in a year. Using AR5 100-year GWPs without climate-carbon feedbacks (CH4 28, N2O 265), what is its total in t CO2e?
C. 860 t CO2e
CO2e = 50 + 10 x 28 + 2 x 265 = 50 + 280 + 530 = 860 t. 896 uses the AR4 values (25 and 298), 866 uses AR6 non-fossil values (27 and 273), and 62 simply adds masses without weighting.
Convert 5 t of N2O to CO2e using the AR6 100-year GWP for N2O of 273.
B. 1,365 t CO2e
5 x 273 = 1,365 t CO2e. 1,325 uses the AR5 value (265), 1,490 the AR4 value (298) and 1,550 the SAR value (310); the stem fixes AR6.
In the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, which volume covers agriculture, forestry and other land use?
A. Volume 4
The five volumes are 1 General Guidance and Reporting, 2 Energy, 3 Industrial Processes and Product Use, 4 AFOLU and 5 Waste. Volume 2 is Energy, where farm fuel use goes; Volume 5 is Waste, where landfill and wastewater go.
A cow's gross energy intake is 300 MJ/day and the methane conversion factor Ym is 6.5%. Using the IPCC Tier 2 equation EF = GE x (Ym/100) x 365 / 55.65, what is her enteric emission factor?
D. 127.9 kg CH4/head/yr
EF = 300 x 0.065 x 365 / 55.65 = 127.9 kg CH4/yr. 142.3 uses 50 MJ/kg instead of 55.65; 0.35 is a daily figure (no x365); 12,790 forgets to divide Ym by 100.
A farm applies 50 t of urea. Using the IPCC default of 0.20 t C per t urea, what CO2 emission is reported from urea application?
C. 36.7 t CO2
C = 50 x 0.20 = 10 t; CO2 = 10 x 44/12 = 36.7 t. 10.0 stops at carbon; 183.3 skips the 0.20 carbon fraction; 2.7 inverts 44/12.
A farm applies 20,000 kg synthetic N. Taking Frac_GASF = 0.1 (fraction volatilised as NH3 and NOx) and EF4 = 0.01 kg N2O-N per kg N volatilised and redeposited, what is the indirect N2O from atmospheric deposition?
B. 31.4 kg N2O
N volatilised = 20,000 x 0.1 = 2,000 kg; N2O-N = 2,000 x 0.01 = 20 kg; N2O = 20 x 44/28 = 31.4 kg. 20.0 stops at N2O-N; 314.3 skips Frac_GASF; 3,142.9 skips EF4.
A miller pays a haulier to bring 500 t of wheat 800 km by truck. The transport factor is 0.10 kg CO2e per tonne-km. What are the category 4 emissions?
D. 40 t CO2e
Tonne-km = 500 x 800 = 400,000; x 0.1 = 40,000 kg = 40 t. 40,000 forgets kg-to-t; 0.08 is per tonne of wheat; 50 drops the distance.
Which is the FAO's public tool for estimating the ex-ante carbon balance of agriculture and land-use projects and policies?
A. EX-ACT
EX-ACT is FAO's ex-ante carbon-balance tool for projects and policies. GLEAM-i is FAO's livestock environmental assessment model interface, COMET-Farm is a USDA farm tool, and CROPWAT is FAO's irrigation water-requirement model, unrelated to carbon.
A biogas project on a pig farm wants to quantify the emission reductions it achieves against a baseline scenario. Which standard is designed for this?
A. ISO 14064-2
ISO 14064-2 covers GHG projects: baseline scenario, quantification, monitoring and reporting of reductions or removal enhancements. ISO 14064-1 is organisation-level, ISO 14067 is product carbon footprint, and ISO 14001 is environmental management systems.
Why might a farm business choose an average of three years as its base year?
A. Weather and yield vary strongly between years, so an average avoids an unrepresentative single year
An average smooths unusual years (drought, flooding), which is allowed if explained. The GHG Protocol does not require it, averaging does not allow dropping years, and an average base year is still recalculated under the same triggers.
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