GATE Energy, Environment & Agri-energy Transitions: practice questions

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 papers

10worked here, free

44written to this exam in this subject

8syllabus units

What this subject covers

Energy systems and their environmental footprints, and the transition in agriculture: fossil and renewable sources, energy-environment nexus, energy efficiency and auditing, and agri-energy options. Solar, wind and bioenergy engineering is in the Agricultural Engineering track (renewable-energy-sources, bioenergy-systems); this subject covers the environmental assessment and policy.

In the exams: GATE ES Section 9 (energy and environment); ICAR AICE subject 71 Unit 6 (whole unit); UGC NET Unit 5; BEE energy auditor exam

Global energy resources and reserves
Renewable and non-renewable sources and their impacts
The energy-environment nexus
Energy use in agriculture and food systems
Energy efficiency and energy auditing
Agrivoltaics and land competition
Bioenergy sustainability: land use, food-versus-fuel, carbon debt
Nuclear, geothermal and tidal energy: environmental issues
Electrification and decarbonisation pathways for farms
Just transition in energy

What GATE asks from it

GATE — Environmental Science and Engineering, Section 9 (energy and environment)

Energy resources and reserves, conventional and non-conventional sources, environmental impacts of energy generation, life-cycle emissions, energy calculations (capacity factor, efficiency, emission intensity) and energy–environment linkages.

Where the 44 questions fall

How our questions for GATE spread across the units of Energy, Environment & Agri-energy Transitions. Difficulty: 12 easy, 23 medium, 9 hard.

Global energy resources and reserves	8
Nuclear, geothermal and tidal energy: environmental issues	8
Renewable and non-renewable sources and their impacts	7
Bioenergy sustainability: land use, food-versus-fuel, carbon debt	7
The energy-environment nexus	5
Energy use in agriculture and food systems	4
Agrivoltaics and land competition	4
Electrification and decarbonisation pathways for farms	1

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Global energy resources and reserves · easy

Roughly what share of global primary energy has been supplied by fossil fuels for decades?

About 30 per cent
About 98 per cent
About 50 per cent
About 80 per cent

Answer and working

D. About 80 per cent

Fossil fuels have supplied around 80% of primary energy for decades, though renewables are growing quickly.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

2 · Renewable and non-renewable sources and their impacts · hard

Using AR5 median life-cycle intensities of 820 g CO₂-e/kWh for coal and 48 g for utility solar, how much CO₂-e does 17,520 MWh of solar generation avoid if it displaces coal power?

13,525 t CO₂-e
14,366 t CO₂-e
841 t CO₂-e
13,525,440 t CO₂-e

Answer and working

A. 13,525 t CO₂-e

Avoided = 17,520 MWh × (820 − 48) kg/MWh = 13,525 t. 14,366 ignores solar's own life-cycle emissions; 841 is solar's emissions; 13,525,440 forgets to convert kg to tonnes.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

3 · Renewable and non-renewable sources and their impacts · medium

Why is fly ash management a particularly large issue for coal power in India?

Fly ash is radioactive waste that must be sent to geological repositories
Fly ash is produced only by gas-fired plants, which dominate Indian power
Indian coal contains no ash, so plants must import ash for cement making
Indian coal has high ash content, so plants produce very large volumes of ash

Answer and working

D. Indian coal has high ash content, so plants produce very large volumes of ash

High-ash domestic coal produces large ash volumes; utilisation in cement, bricks and road fill is promoted. Fly ash comes from coal, not gas, and is not handled as high-level radioactive waste.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

4 · Renewable and non-renewable sources and their impacts · hard

Why do capacity factors matter when comparing the annual output of a solar plant with that of a nuclear plant of the same capacity?

Capacity factor measures only efficiency of conversion, not hours of operation
Nuclear plants have lower capacity factors than solar because they refuel daily
Solar's capacity factor is far lower than nuclear's, so output differs
Capacity factors are identical for all technologies, so equal capacity gives equal output

Answer and working

C. Solar's capacity factor is far lower than nuclear's, so output differs

Capacity factor is actual output ÷ maximum possible output; variable solar has a much lower factor than baseload nuclear, so the same MW yields far fewer MWh. It is not conversion efficiency, and nuclear refuels every 1–2 years.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

5 · The energy-environment nexus · easy

Which cooling system for thermal power plants withdraws the most water?

Dry (air) cooling
Recirculating cooling towers
Once-through cooling
Hybrid wet–dry cooling

Answer and working

C. Once-through cooling

Once-through systems withdraw large volumes and return warmed water; recirculating systems withdraw less but evaporate more; dry cooling uses little water at an efficiency cost.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

6 · Agrivoltaics and land competition · easy

Roughly how much land does a ground-mounted utility solar PV plant occupy per megawatt?

Of the order of 100 hectares
Of the order of 50 hectares
Of the order of 1–2 hectares
Of the order of 0.01 hectare

Answer and working

C. Of the order of 1–2 hectares

Ground-mounted PV needs roughly 1–2 ha per MW depending on efficiency, spacing, tracking and latitude.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

7 · Bioenergy sustainability: land use, food-versus-fuel, carbon debt · easy

Which bioenergy option is often among the most sustainable because it uses wastes and reduces methane?

Charcoal from clear-felled natural forest
Palm-oil biodiesel from converted peatland
Biogas from anaerobic digestion of manure
Maize ethanol from newly irrigated land

Answer and working

C. Biogas from anaerobic digestion of manure

Biogas from manure and wastes provides energy and fertiliser and cuts manure methane. The other options carry carbon debt or deforestation.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

8 · Bioenergy sustainability: land use, food-versus-fuel, carbon debt · hard

Why does large-scale BECCS in mitigation pathways raise sustainability concerns?

It needs vast land and water, competing with food and biodiversity
It can be deployed only in the Arctic, where no crops grow
It is banned under the Paris Agreement as a form of geoengineering
It releases more CO₂ than it captures in every possible configuration

Answer and working

A. It needs vast land and water, competing with food and biodiversity

BECCS at the scale in some pathways would require land areas comparable to large shares of cropland, with water and biodiversity trade-offs. It can be net negative if well designed, is not region-limited, and is not banned.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

9 · Bioenergy sustainability: land use, food-versus-fuel, carbon debt · medium

Why was the expansion of crop-based biofuels linked to the 2007–2008 food price spikes?

Biofuels replaced all food exports from major producing countries
Biofuel refineries released pollutants that destroyed crops over large areas
Biofuels lowered oil prices, which reduced farm incomes and output
Diverting crops to fuel tightened food markets, among other factors

Answer and working

D. Diverting crops to fuel tightened food markets, among other factors

Biofuel demand added to pressures from oil prices, weather and export bans; the size of its contribution is debated. It did not destroy crops, replace all exports or lower oil prices.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

10 · Nuclear, geothermal and tidal energy: environmental issues · medium

Which is the world's largest tidal barrage power station?

Three Gorges, China, 22,500 MW
Itaipu, Brazil–Paraguay, 14,000 MW
Sihwa Lake, South Korea, 254 MW
La Rance, France, 240 MW

Answer and working

C. Sihwa Lake, South Korea, 254 MW

Sihwa Lake (254 MW) is the largest tidal plant; La Rance (240 MW, 1966) the oldest large one. Three Gorges and Itaipu are river hydropower dams.

Further reading: See the manual sources: IPCC AR5/AR6 WGIII energy chapters, IEA, FAO (2011), BEE guide books and the studies named in the explanation

Ten here, 44 in the app. The Laisha app has every practice question we have written to GATE in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.

Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.

Practise the full set in Laisha →