Hydrogen has been described as everything from the fuel of the future to the missing piece of the clean-energy transition.
It can power fuel cells, store energy, produce industrial heat and potentially help reduce emissions from industries that are extremely difficult to electrify.
It also has some major drawbacks.
Hydrogen isn’t an energy source in the same way sunlight or wind is.
It has to be produced using other forms of energy.
Producing it can consume substantial amounts of electricity, storing and transporting it can be difficult, and converting hydrogen back into useful energy creates additional losses.
Hydrogen therefore has enormous potential for some applications.
For others, using electricity directly may make far more sense.
Understanding that distinction is the key to understanding hydrogen’s likely role in a cleaner energy future.
What Is Hydrogen?
Hydrogen is the simplest and most abundant element in the universe.
But on Earth, hydrogen is usually bound to other elements rather than sitting around as a convenient fuel.
Water, for example, contains hydrogen and oxygen.
Natural gas contains hydrogen bonded with carbon.
To use hydrogen as an energy carrier, it first needs to be separated from these compounds.
That process requires energy.
This is why hydrogen is better thought of as an energy carrier rather than a primary energy source.
It is somewhat like electricity.
Energy is used to produce it, it can transport that energy somewhere else, and it can later be converted into a useful form.
Why Is Hydrogen Suddenly Getting So Much Attention?
The clean-energy transition has made enormous progress in electricity generation.
Solar and wind can generate electricity without burning fossil fuels.
Batteries can store electricity.
Electric vehicles can replace many petrol and diesel cars.
Heat pumps can replace fossil-fuel heating in many buildings.
But some parts of the economy are much harder to electrify.
Steelmaking requires enormous amounts of energy and traditionally depends heavily on coal.
Chemical industries already use large quantities of hydrogen produced from fossil fuels.
Long-distance shipping and some other forms of heavy transport are difficult to power using batteries alone.
Hydrogen could potentially help in some of these areas.
That is where much of its genuine promise lies.
Hydrogen Isn’t Automatically Clean
Hydrogen itself doesn’t contain carbon.
But that doesn’t mean all hydrogen is environmentally friendly.
The climate impact depends heavily on how it is produced.
Today, much of the world’s hydrogen is produced from fossil fuels.
That process releases greenhouse gases.
Hydrogen can also be produced using renewable electricity and water.
The final product may look identical.
Its environmental footprint can be completely different.
This is why discussions about hydrogen often use colours to describe different production methods.
What Is Grey Hydrogen?
Grey hydrogen is generally produced from natural gas using a process called steam methane reforming.
The process separates hydrogen from methane.
Carbon dioxide is produced as a result and released into the atmosphere.
Grey hydrogen has long been used in industries such as oil refining and fertiliser production.
It is relatively established and widely available.
But because its production creates substantial greenhouse gas emissions, simply replacing one fossil fuel with grey hydrogen doesn’t represent the kind of clean-energy transition often implied by the word hydrogen.
How the hydrogen was made matters.
What Is Blue Hydrogen?
Blue hydrogen is also usually produced from natural gas.
The difference is that some of the carbon dioxide produced during hydrogen manufacture is captured and stored rather than released directly into the atmosphere.
This is known as carbon capture and storage.
Supporters argue that blue hydrogen could provide lower-emission hydrogen while renewable hydrogen production expands.
Critics point to several problems.
Carbon capture doesn’t necessarily capture every emission.
Natural gas production and transport can also release methane, a powerful greenhouse gas.
The overall climate performance therefore depends on how effectively carbon is captured and how much methane escapes across the gas supply chain.
Blue hydrogen may reduce emissions compared with conventional grey hydrogen under suitable conditions.
It should not automatically be treated as emission-free.
What Is Green Hydrogen?
Green hydrogen is produced using electrolysis.
An electrolyser uses electricity to split water into hydrogen and oxygen.
When the electricity comes from renewable sources such as solar or wind, the resulting hydrogen can be produced with very low operational greenhouse gas emissions.
This is the form of hydrogen receiving much of the attention in clean-energy discussions.
It sounds almost ideal.
Take water.
Add renewable electricity.
Produce hydrogen.
The difficulty is efficiency and cost.
Why Does Green Hydrogen Need So Much Electricity?
Every energy conversion involves losses.
Imagine starting with renewable electricity.
That electricity powers an electrolyser to produce hydrogen.
The hydrogen may then need to be compressed, cooled, stored or transported.
If it is eventually used in a fuel cell, another conversion turns its chemical energy back into electricity.
Energy is lost at each stage.
If the original renewable electricity could have powered the final application directly, going through hydrogen can require considerably more electricity to achieve the same useful result.
That doesn’t make hydrogen useless.
It means we need a good reason to use it.
Direct Electricity Is Often the Simpler Option
Suppose renewable electricity can directly power an electric motor.
The energy path is relatively simple.
Electricity travels through the grid, charges a battery if necessary and powers the motor.
Using hydrogen adds extra steps.
Electricity produces hydrogen.
The hydrogen is compressed and transported.
A fuel cell converts it back into electricity.
That electricity finally powers the motor.
Every extra step adds equipment, cost and energy losses.
For many applications, direct electrification is therefore likely to be more efficient.
Hydrogen becomes particularly interesting when direct electricity is difficult to use.
Hydrogen Is Already an Important Industrial Material
One fact sometimes gets lost in futuristic discussions about hydrogen.
We already use enormous quantities of it.
Hydrogen is an important feedstock for producing ammonia, which is widely used in fertilisers.
It is also used in oil refining and chemical manufacturing.
Much of this existing hydrogen is produced from fossil fuels.
Replacing today’s fossil-derived hydrogen with lower-emission alternatives could therefore provide a substantial clean-energy opportunity before entirely new hydrogen markets are created.
Sometimes the most obvious use for green hydrogen is simply replacing dirty hydrogen.
Green Steel Could Be a Major Opportunity
Steelmaking is one of the most frequently discussed future uses for hydrogen.
Traditional steel production often uses coal both as an energy source and as part of the chemical process that turns iron ore into iron.
Hydrogen can potentially replace coal in some steelmaking processes.
Instead of producing large quantities of carbon dioxide during the chemical reaction, hydrogen can react with oxygen to produce water.
The resulting iron can then be processed into steel using electric furnaces.
This doesn’t make steel production impact-free.
Mining, transport, electricity generation and industrial infrastructure still matter.
But green hydrogen combined with renewable electricity offers a potential pathway for significantly reducing emissions from one of the world’s most important industrial materials.
Hydrogen Could Help Produce Cleaner Fertiliser
Ammonia production already consumes large quantities of hydrogen.
Ammonia is a key ingredient in many fertilisers.
Today that hydrogen commonly comes from natural gas or other fossil fuels.
Producing the hydrogen using renewable electricity instead could reduce emissions associated with fertiliser manufacturing.
This is another application where hydrogen doesn’t need to invent a completely new market.
The industry already needs hydrogen.
The challenge is producing it differently.
What About Hydrogen Cars?
Hydrogen fuel-cell vehicles have often been proposed as an alternative to battery-electric cars.
A fuel-cell vehicle carries compressed hydrogen in tanks.
The fuel cell converts the hydrogen into electricity, which powers an electric motor.
Refuelling can be relatively quick and driving ranges can be substantial.
But hydrogen passenger cars face major challenges.
Hydrogen filling stations are expensive and relatively uncommon.
Producing, compressing and transporting hydrogen consumes energy.
Battery-electric vehicles can use electricity much more directly and can often recharge at home.
For ordinary passenger cars, battery-electric technology has significant efficiency and infrastructure advantages.
Hydrogen may still have transport niches, but it isn’t automatically the best option simply because refuelling resembles today’s petrol-station model.
Could Hydrogen Power Heavy Trucks?
Heavy trucks create a more interesting debate.
Long-distance trucks need substantial energy and operate under demanding schedules.
Large batteries add weight and may require extremely powerful charging infrastructure.
Hydrogen fuel cells could potentially offer long range with relatively fast refuelling.
But battery technology and high-powered truck charging are developing rapidly too.
Which technology proves more competitive may vary by route and operation.
A truck travelling predictable distances between major depots has different requirements from one operating across remote regions.
Rather than assuming all heavy transport will use hydrogen, it makes more sense to compare technologies for specific jobs.
Shipping May Be a Stronger Candidate
Long-distance shipping is particularly difficult to electrify with batteries.
Large ocean-going ships need enormous amounts of energy for journeys lasting days or weeks.
Hydrogen itself is difficult to store compactly, but it can be converted into other fuels.
Green ammonia is one possibility.
Synthetic fuels made using renewable hydrogen are another.
These fuels involve additional conversion losses.
But shipping is one of those sectors where efficiency isn’t the only consideration.
The fuel must also carry enough energy for very long journeys.
Hydrogen-derived fuels may therefore find roles where direct battery electrification is impractical.
What About Aviation?
Aircraft present an even harder problem.
Weight is critical in aviation.
Batteries are much heavier for the amount of usable energy they contain than conventional jet fuel.
Hydrogen has high energy by weight, but storing it requires bulky tanks and potentially extremely low temperatures if used as liquid hydrogen.
Another possibility is using renewable hydrogen to manufacture synthetic aviation fuels that can work with more conventional aircraft systems.
Producing these fuels requires substantial renewable energy.
Aviation is therefore unlikely to have a simple clean-energy solution.
Hydrogen may form part of the answer, but significant technical and economic challenges remain.
Hydrogen Can Store Renewable Energy
Hydrogen can also act as energy storage.
When renewable electricity is abundant, electrolysers could produce hydrogen.
That hydrogen can be stored and used later.
Unlike many batteries, hydrogen could potentially store energy for very long periods.
This creates interest in seasonal storage.
A region might have abundant renewable generation during one season but lower production during another.
Producing hydrogen during periods of surplus electricity could theoretically preserve some of that energy for later.
But the round-trip efficiency is relatively low if the hydrogen is eventually converted back into electricity.
For daily energy shifting, batteries are generally more efficient.
Hydrogen’s advantage may be storing very large quantities for much longer periods where other options are limited.
Storing Hydrogen Isn’t Easy
Hydrogen molecules are extremely small.
The gas also has low energy density by volume under normal conditions.
To store useful quantities, hydrogen is often compressed to very high pressures or cooled until it becomes liquid.
Both approaches require energy and specialised equipment.
Hydrogen can also interact with some metals and contribute to embrittlement, which can damage infrastructure over time.
Alternative storage methods include underground salt caverns and conversion into chemicals such as ammonia.
Each approach has advantages and disadvantages.
Hydrogen storage is possible.
It simply isn’t as straightforward as filling an ordinary tank.
Transporting Hydrogen Is Another Challenge
Hydrogen can potentially be moved through pipelines.
It can also be transported in specialised tanks or converted into other substances that are easier to ship.
Existing natural-gas pipelines may sometimes be adapted or used for hydrogen blends, but compatibility varies.
Compressors, valves and other equipment may need modification.
Transporting liquid hydrogen requires extremely low temperatures.
Converting hydrogen into ammonia makes shipping easier in some respects but introduces another conversion step.
Building an international hydrogen industry would therefore require substantial new infrastructure.
Could Existing Gas Networks Carry Hydrogen to Homes?
One proposal is blending hydrogen into existing natural-gas networks or eventually converting networks to carry much higher concentrations of hydrogen.
Technically, this may be possible in some places.
But there is a bigger question.
Is hydrogen the best way to heat homes?
Heat pumps can use electricity directly and can deliver several units of heat for each unit of electricity they consume.
Producing hydrogen from electricity and then burning it in a boiler introduces significant conversion losses.
For many buildings, direct electrification through heat pumps is therefore likely to use renewable electricity more efficiently.
Hydrogen may have more value in industries where direct electrification is much harder.
Hydrogen Has Safety Considerations
All energy carriers require safe handling.
Petrol burns.
Natural gas can explode.
Lithium-ion batteries can experience thermal runaway.
Hydrogen has its own characteristics.
It is highly flammable and can ignite across a wide range of concentrations.
Because hydrogen molecules are extremely small, leaks can also be difficult to contain.
On the other hand, hydrogen is very light and disperses rapidly in open air.
Hydrogen systems can be designed and operated safely, just as other fuel systems are.
But widespread use requires appropriate standards, equipment and training.
Water Use Needs to Be Considered
Green hydrogen requires water for electrolysis.
At global scale, this raises questions about water availability, particularly in dry regions that may also have excellent solar resources.
The amount of water required for electrolysis itself can be manageable compared with many other industrial and agricultural uses, but local conditions matter.
Hydrogen projects should not compete irresponsibly with drinking water, agriculture or ecosystems.
Coastal projects may use desalinated seawater, but desalination requires additional equipment and energy.
Again, there is no universal answer.
Location matters.
Green Hydrogen Needs Enormous Amounts of Renewable Energy
A genuinely large green-hydrogen industry would require vast amounts of clean electricity.
That creates an important question.
Should renewable electricity be used to produce hydrogen while nearby electricity grids are still heavily dependent on fossil fuels?
In some cases, directly replacing fossil-fuel electricity with renewable generation may deliver greater immediate emission reductions.
As electricity systems become cleaner and renewable generation expands, more electricity may become available for hydrogen production.
Timing and location therefore matter.
Calling hydrogen “green” shouldn’t mean ignoring the opportunity cost of the renewable electricity used to make it.
What About Hydrogen Leaks?
Hydrogen itself isn’t carbon dioxide.
But releasing hydrogen into the atmosphere isn’t necessarily environmentally irrelevant.
Atmospheric hydrogen can influence chemical reactions that affect methane and other greenhouse gases.
Large-scale hydrogen systems therefore need to minimise leakage.
This is an emerging area of climate research and another reminder that no energy system should automatically be assumed to have zero environmental impact.
The objective should be to understand and manage the full system.
The Colour Labels Can Be Misleading
Green, blue, grey and other colour labels provide convenient shorthand.
But they can also oversimplify.
Two batches of “green” hydrogen could have different environmental footprints depending on how the electricity was generated and whether new renewable capacity was built for the project.
Two blue-hydrogen plants could capture very different percentages of their emissions.
The colour alone doesn’t tell us everything.
A better question is:
How much greenhouse gas was actually emitted across the entire production process?
That is ultimately more useful than the label.
Where Does Hydrogen Make the Most Sense?
Hydrogen’s strongest opportunities are likely to be applications where direct electrification is difficult.
These may include:
Producing lower-emission fertilisers and chemicals.
Replacing fossil-derived hydrogen already used by industry.
Reducing coal use in some steelmaking processes.
Producing fuels for some shipping applications.
Providing feedstock for synthetic fuels.
Potentially storing large quantities of renewable energy for long periods.
Other applications remain possible.
But hydrogen should solve a genuine problem rather than simply being used because it sounds futuristic.
Where Does Hydrogen Make Less Sense?
Applications that can easily use electricity directly often have less reason to convert that electricity into hydrogen first.
Passenger cars are a good example where battery-electric vehicles have major efficiency advantages.
Home heating is another area where heat pumps can use electricity very efficiently.
Short-duration electricity storage is generally better suited to batteries and other efficient storage systems.
This doesn’t mean hydrogen can never be used in these applications.
It means it has to compete against alternatives that may require less energy and infrastructure.
Hydrogen Is Not the New Oil
Hydrogen is sometimes discussed as though it will simply replace oil and gas across the entire economy.
That is unlikely to be the most efficient outcome.
The clean-energy transition isn’t about finding one new fuel to replace every old fuel.
It is increasingly about using different technologies for the jobs they perform best.
Solar and wind can generate electricity.
Batteries can provide short-term storage.
Heat pumps can heat buildings.
Electric motors can power cars.
Hydrogen can potentially tackle some of the difficult industrial and energy applications left over.
That may sound less revolutionary than a complete hydrogen economy.
It may also be much more realistic.
Promise Without the Hype
Hydrogen deserves an important place in discussions about clean energy.
It can potentially help decarbonise industries where batteries and direct electrification struggle.
Green hydrogen could replace fossil-derived hydrogen already used around the world.
It could help produce cleaner steel, fertiliser and industrial chemicals.
Hydrogen-derived fuels may eventually help tackle parts of shipping and aviation.
And long-term hydrogen storage could complement renewable electricity systems.
But hydrogen isn’t free energy.
It takes energy to produce.
It is difficult to store.
It requires new infrastructure.
And every conversion reduces efficiency.
Those limitations don’t make hydrogen a failure.
They simply tell us where to use it wisely.
The Hydrogen Future Will Probably Be Selective
The most successful hydrogen future may not be one where every house, car and appliance runs on hydrogen.
It may be one where hydrogen quietly solves some of the clean-energy transition’s hardest problems.
A steel plant replaces coal.
A fertiliser factory stops relying on fossil-derived hydrogen.
A ship uses a renewable hydrogen-derived fuel.
A large energy system stores renewable energy for periods when other storage options aren’t practical.
In those applications, hydrogen could be enormously valuable.
The question is therefore not whether hydrogen is the fuel of the future.
A better question is:
Which parts of our energy future genuinely need hydrogen?
Answer that carefully, and hydrogen could become an important clean-energy tool without needing to become the answer to everything.
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