---
title: "Hydrogen fuel advantages and disadvantages"
subject: "Energy Environment and Society"
chapter: 3
key: "semester_7/energy_environment_and_society:hydrogen-fuel-adv-disadv"
source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/hydrogen-fuel-adv-disadv
site: BCT Engineering
---

# Hydrogen fuel advantages and disadvantages

Energy Environment and Society · Chapter 3: Renewable Energy Sources

- Asked in: 2074 Asoj, 1+3 marks; 2071 Chaitra, 4 marks; 2069 Chaitra, 2 marks; year not given (asked 3 times)
- Video: [The truth about hydrogen](https://www.youtube.com/watch?v=AGTjKJHu99c) — DW Planet A
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/hydrogen-fuel-adv-disadv
- Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-3

## Question

What is Hydrogen Fuel? Describe about advantages and disadvantages of Hydrogen Fuel.

## Short answer

Hydrogen fuel is H2 used as an energy carrier in combustion or fuel cells, producing only water at the point of use. Advantages include clean combustion, very high energy per kg of about 120 MJ/kg, and production from renewable electricity. Disadvantages are energy-intensive production, low volumetric density, high flammability, missing infrastructure, and low round-trip efficiency.

## Answer

**Hydrogen fuel** is hydrogen (H₂) used as an energy carrier: it is burnt in engines and turbines or used in fuel cells to produce electricity with water as the only product. Hydrogen is not found free in nature in large amounts, so it must be produced from water (electrolysis), natural gas (steam reforming), biomass or coal. It is an **energy carrier**, not a primary source.

2H₂ + O₂ → 2H₂O + energy

Calorific value: about 120–142 MJ/kg (higher than any other fuel; about 2.5 times that of petrol per kg), but its volume energy density is very low.

#### Advantages
- Burns cleanly: only water vapour, no CO₂ at the point of use (and no SO₂, soot).
- High energy per kilogram (about 120 MJ/kg).
- Can be produced from water using renewable electricity (green hydrogen), and so supports a clean energy system.
- Fuel cells have high efficiency (40–60%, up to 80% with combined heat) and quiet operation.
- Can store surplus renewable electricity, and can be used in transport, industry and power.
- Can be transported by pipelines and stored for long periods.

#### Disadvantages
- Does not exist free; production needs energy, and today most hydrogen (grey hydrogen) comes from natural gas and emits CO₂.
- Low volumetric energy density, so needs high-pressure tanks (350–700 bar), liquefaction (−253 °C) or hydrides: costly and heavy.
- Highly flammable and explosive (wide flammability range 4–75% in air), and leaks easily, so safety is a concern.
- Infrastructure (production, pipelines, filling stations) is missing and expensive.
- Fuel cells and electrolysers are costly, and round-trip efficiency is low (about 30–40%).
- Embrittlement of metals.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why is hydrogen called an energy carrier and not a primary source?
   A. It cannot be burned
   B. It does not exist free in large amounts and must be produced using energy
   C. It is found freely underground
   D. It produces CO2 when used
   Answer: B. Hydrogen has to be made from water, gas, biomass or coal, so it only carries energy. (Key point: Energy carrier)

2. Which statement about hydrogen's energy density is correct?
   A. High per kilogram but very low per unit volume
   B. Low per kilogram and low per volume
   C. Low per kilogram but high per volume
   D. High per kilogram and high per volume
   Answer: A. About 120 MJ/kg but low volumetric density, so needs high pressure, liquefaction or hydrides. (Key point: Energy density)

3. What is a main environmental drawback of today's hydrogen production?
   A. It is made only from renewable electricity
   B. It releases SO2 at point of use
   C. It always uses coal gasification
   D. Most is grey hydrogen from natural gas, which emits CO2
   Answer: D. Most hydrogen today is produced by steam reforming of natural gas, emitting CO2. (Key point: Grey hydrogen)

4. Why is hydrogen safety a concern?
   A. It is toxic at low concentration
   B. It does not burn in air
   C. Wide flammability range (4-75% in air) and easy leakage
   D. It is heavier than air and pools on the ground
   Answer: C. Hydrogen is highly flammable over a wide range and leaks easily. (Key point: Safety)

## Related in Energy Environment and Society

- [Hydrogen fuel compared with solar](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahydrogen-fuel-solar-comparison) — Energy Environment and Society, chapter 3
- [Hydrogen production and storage](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahydrogen-production-storage) — Energy Environment and Society, chapter 3
- [Fuel cell and its working](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Afuel-cell-working) — Energy Environment and Society, chapter 3, asked 2×

## Related in other subjects

- [Fuel cell voltage, efficiency and hydrogen use](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Afuel-cell-stack-numerical) — Energy Resources, chapter 6
- [Working principle and types of fuel cells](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Apem-fuel-cell-working-types) — Energy Resources, chapter 6
- [Calorific value of fuel by Dulong's formula](https://www.bctengineer.com/question.md?key=semester_6%2Finternal_combustion_engines%3Acalorific-value-dulong-formula-numerical) — Internal Combustion Engines, chapter 3