Green Hydrogen Comes With its Own Challenges and Risks

GLOBAL HYDROGEN DEMAND reached 94 million tonnes in 2021, and contained energy equal to about 2,5% of global final energy consumption. Only about 0,1% of current global hydrogen production is green, but big expansions are planned.

New applications for green hydrogen are also envisaged.

Since the objective of using green hydrogen is really to reduce carbon dioxide, the applications to target first should be those that will yield the largest reductions in emissions.

Green hydrogen currently costs much more to make than less clean types of hydrogen.

Using it to produce the 180 million tonnes a year of ammonia required globally for fertiliser production would have a severe knock-on effect on food prices.

So it is difficult to see how this transition is going to occur.

HOW IS IT MADE?

Green hydrogen is made from water. Using renewable (‘green’) electricity, equipment called electrolysers separates the hydrogen from oxygen in water (H2O). The process is called electrolysis.

Green hydrogen production emits no carbon dioxide, but the construction of renewable electricity infrastructure currently uses fossil fuels, which do emit carbon dioxide.

Hydrogen has traditionally been made from non-renewable energy sources like coal (‘black hydrogen’) and natural gas (‘grey hydrogen’).

When these methods are combined with carbon capture and storage, the hydrogen produced is known as ‘blue hydrogen’.

THE CHALLENGES

Although the costs of renewable power generation have been coming down, the cost of electrolysis is still not commercially competitive.

Today, green hydrogen has an estimated energy equivalent cost of between US$250 and US$400 per barrel of oil at the factory gate, according to the International Renewable Energy Agency.

Future cost reductions are forecast but these are uncertain. Current oil prices are around US$100 a barrel – much less than it would cost to use green hydrogen instead of conventional petroleum products.

The costs of transporting hydrogen must be taken into account too.

Unfortunately, the physics of hydrogen is against low-cost hydrogen transport.

It is much more challenging than oil-based liquid fuels, liquefied petroleum gas or liquefied natural gas.

Ocean transport of hydrogen has to be at very low temperatures (-253ºC). Petrol or diesel doesn’t need costly refrigeration: It is transported at ambient air temperature.

And hydrogen carries only 25% of the energy that a litre of petrol does, making it much more expensive to transport and store the same amount of energy.

Alternative ways to transport hydrogen have been investigated. Because ammonia (NH3) is much easier and cheaper to transport than hydrogen, the International Renewable Energy Agency has recommended “storing” hydrogen in ammonia for shipping.

But that requires additional equipment to put the hydrogen into ammonia and strip it out at its destination.

These processes add costs of about US$2,50-US$4,20/kg (equivalent to US$123-US$207 per barrel of oil) according to the agency.

DIFFICULT TO HANDLE

Hydrogen is more difficult to handle than conventional fossil fuels. It is a colourless, odourless and tasteless gas, unlike conventional hydrocarbons. This makes leak detection more difficult and increases the risk of fire or explosion. Hydrogen fires are invisible to the human eye.

The widespread introduction of hydrogen into society will require new measures and skills, including insurance, materials handling, firefighting and disaster management.

PIONEERING PROJECTS

Where are the first hydrogen mega projects likely to be built?

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