Blue hydrogen v green hydrogen

Boris Johnson when mayor of London confirmed Transport for London would run Toyota Mirari hydrogen fuel cell vehicles as part of its fleet.
Hydrogen is likely to be an important part of the next stage of the UK’s energy transition. But where will we get it from, and fast?


Radical plans to cut carbon emissions by 78 percent by 2035 have now been announced by the UK Government. This is ambitious to say the least - and will require a pretty rapid transition away from fossil fuels to cleaner alternative. 

Zero-carbon renewable electricity is obviously the preferable way to go. But it cannot yet be relied on as the sole solution due to the high cost in production and the intermittency of wind and solar power.

Therefore, we need a ‘back-up’ source - and this is where hydrogen comes into play. Hydrogen is likely to be an important part of the next stage of the UK’s energy transition. But where will we get it from - and how fast can it come online?


There is still debate over how to most effectively source and use hydrogen in the transition to carbon neutrality.

Green hydrogen is currently seen as the ‘good guy’ as it’s emission free. An electric current produced by renewable electricity is used to separate water into oxygen and hydrogen using electrolysis.

However, it’s very expensive due to high costs of supply chain logistics and electrolysers that produce hydrogen in this way, and the renewable energy required isn’t reliable enough to meet hydrogen demand. 

Blue hydrogen on the other hand is currently around half the price of green, and is made using natural gas, through separating it from the hydrocarbons that make it up through the application of heat, also known as reforming.

The theory is that most of the carbon dioxide (CO2) produced during this process could then be captured and stored permanently underground. This is what’s referred to as Carbon Capture and Storage (CCS). However, this technology has still not been deployed at any real scale, presents a lot of risk and is itself expensive.


And even in the best case scenario CCS does not stop all carbon emissions. Future CO₂-capture efficiencies are expected to reach 85-95 percent at best, which means that five to 15 percent of all CO₂ will leak. 


We also need to recognise the methane emissions involved in using natural gas, which is much more potent than CO2. CO2 monitoring, verification and certification will be needed to regulate non-captured emissions.

The consumption of green hydrogen should certainly be a long-term goal. But some argue that there should still be a role for blue hydrogen as an enabler of a future hydrogen economy.

They say the technology is already available, CO2 storage is becoming more viable and the gradual expansion of hydrogen use can allow new infrastructure to be built that can ultimately be used to enable the development of a green hydrogen business. 

It now looks likely that blue hydrogen will be a key player in the government's attempts to reach its 2030 carbon reduction goal even though this method isn’t zero-carbon. Hydrogen should only be used selectively, where it adds most value or as an alternative where electrification isn’t feasible. 


Hydrogen is more readily storable than electricity at a very large scale. This means that it has particular value as a low-carbon replacement for natural gas - and potentially oil - in applications where full electrification is complex, disruptive or expensive, such as heating, heavy-duty vehicles, shipping, industry and potentially in power to replace natural gas. 

We need to limit costs by working with what we have, as most countries won’t be able to undertake full infrastructure changes at present.

Hydrogen should therefore be used in ways that would not initially require major infrastructure changes - including use in buses, power generation, industry or blending at small proportions into the natural gas supply. Transport of hydrogen via existing and refurbished gas pipelines is also being explored. 

The hydrogen transition won’t happen overnight. The reason we aren’t already using hydrogen in abundance is because it’s expensive. Per unit of energy, hydrogen supply costs are 1.5 to 5 times those of natural gas.

We need to drive down costs through deployment at scale, and stronger financial incentives. At the moment, there isn’t sufficient consumer demand for companies to make a return on investment. We either need to raise carbon tax on methane or subsidise hydrogen. 


At present 350 million tonnes of CO2 is emitted a year in the UK. We’d need around £40 billion a year to decarbonise the economy at present, which in the grand scheme would only be one to two percent of GDP growth over 30 years, so it’s fundamentally worth the investment.  

In the short term future, BP is working on plans for a major blue hydrogen facility in Teesside, north-east England, which could generate as much as 1 gigawatt of blue hydrogen by 2030.

That in itself is up to 20 percent of the UK’s goal to have five gigawatts of low-carbon hydrogen capacity by 2030, supporting as many as 8,000 jobs. A final investment decision on the development will be taken in 2024.

Environmental experts agree that green hydrogen would ideally be the sole provider of hydrogen, and this does look promising. Electrolysers are scaling up quickly, from megawatt (MW) to gigawatt (GW) scale, as technology continues to evolve.

Electrolyser costs are projected to halve by 2040 to 2050 while renewable electricity costs will continue to fall as well. It is possible that renewable hydrogen will soon become the cheapest hydrogen supply option for many applications.

This Author

Sophie Johnson is a Zoology graduate and passionate conservation blogger from the UK.

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