Why Hydrogen Is Not Used as a Fuel Despite Being the Cleanest

#Obstacle 1: it has to be manufactured

There are no hydrogen wells. Free hydrogen gas is almost absent from the Earth's atmosphere because it is light enough to escape into space. All hydrogen on Earth is chemically bound — in water, in hydrocarbons, in biological matter.

Extracting it costs energy, and thermodynamics guarantees the cost exceeds the return:

Steam methane reforming (about 95% of world production):

CH4 + H2O  ->  CO + 3 H2

Cheap, mature — and it releases carbon dioxide, so the hydrogen is only as clean as its production allows.

Electrolysis of water:

2 H2O  ->  2 H2 + O2

Clean if the electricity is clean, but round-trip efficiency is poor. Electrolysis, compression, storage and reconversion in a fuel cell typically return roughly 30% of the input electricity.

This is the central point: hydrogen is an energy carrier, not an energy source. It stores energy generated elsewhere, at a loss.

#Obstacle 2: terrible volumetric density

Hydrogen is the lightest gas, which gives it the best mass-based calorific value and the worst volume-based one.

Storage form	Energy per litre (MJ)
Petrol	~32
Diesel	~36
LPG (liquid)	~25
Liquid hydrogen (−253 °C)	~8.5
Hydrogen at 700 bar	~5.6
Hydrogen at 1 bar	~0.011

At ordinary pressure, a cubic metre of hydrogen contains almost no energy. Even compressed to 700 bar — requiring heavy carbon-fibre tanks and about 10–15% of the hydrogen's own energy to compress — it stores roughly a sixth of petrol's energy per litre.

For anything carrying its own fuel, this is decisive.

#Obstacle 3: storage is hard in every direction

• Compression to 700 bar — expensive tanks, energy cost, safety engineering
• Liquefaction at −253 °C — consumes 30–40% of the hydrogen's energy content, and stored liquid hydrogen boils off continuously
• Metal hydrides and chemical carriers — safer and denser but heavy, slow to charge and discharge, still developmental

#Obstacle 4: it attacks its own containers

Hydrogen embrittlement. Hydrogen atoms are small enough to diffuse into the crystal lattice of many steels, where they accumulate at grain boundaries and make the metal brittle and prone to cracking. Ordinary steel pipelines and vessels cannot simply be repurposed; special alloys or liners are required.

Leakage. The hydrogen molecule is the smallest there is, so it escapes through seals, joints and materials that comfortably contain methane. Leaked hydrogen is also an indirect greenhouse gas, since it extends the atmospheric lifetime of methane.

#Obstacle 5: the flammability envelope

Hydrogen burns in air across an unusually wide concentration range — roughly 4% to 75%, against about 5–15% for methane. That means far more leak scenarios produce an ignitable mixture. Its ignition energy is very low, and its flame is nearly invisible in daylight, which complicates detection.

In its favour, hydrogen disperses upward extremely fast in open air, so outdoor leaks dissipate quickly. The danger is concentrated in enclosed spaces.

#Obstacle 6: no infrastructure

A century of investment built refineries, pipelines, tankers, filling stations and engines around liquid hydrocarbons. Hydrogen has a few hundred public refuelling stations worldwide against hundreds of thousands of petrol stations, and existing gas pipelines mostly cannot carry pure hydrogen without modification.

#Where hydrogen does make sense

The obstacles are logistical, not fundamental, so hydrogen wins wherever those specific constraints do not bite:

• Rocketry. Liquid hydrogen and liquid oxygen give the highest specific impulse of any practical chemical propellant. Volume is available; mass is critical.
• Industrial feedstock. Ammonia for fertiliser, refinery hydrotreating, methanol production — already the largest current uses.
• Steel making. Hydrogen can replace coking coal as the reducing agent, eliminating a large industrial carbon source.
• Heavy transport and long-duration storage. Where batteries are too heavy or too slow to recharge.

For the number that makes hydrogen look so good on paper, see which fuel has the highest calorific value. For the technology that uses hydrogen best, fuel cells explained.

#The compact answer

Hydrogen is not widely used as a fuel because it does not occur freely in nature and must be manufactured, which consumes more energy than the hydrogen releases. It has a very low energy density by volume, so it must be stored at about 700 bar or cooled to −253 °C, both of which are expensive and energy-intensive. It also causes embrittlement of metals, leaks easily, has a very wide flammability range, and lacks distribution infrastructure.