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turning the air blue

blue hydrogen's role in the journey to net zero transport

PHC's Senior Fuels Technology Partner, Dr. John Buxton, continues his series on hydrogen as a fuel for commercial and public transport

Transport’s Road to Net Zero 

The transport sector is on a journey. It may be a cliché but it’s true - we’re on a journey to decarbonise transport operations and hydrogen is going to help. Are we there yet? No. Nowhere near. But the industry is making progress and today’s blog moves across the spectrum to “blue” hydrogen and its role in decarbonising road freight and public transport.   

Blue Hydrogen 

Why ‘Blue’? 

Perhaps because it’s next to green in the visible light spectrum and is arguably the next best hydrogen ‘type’ in terms of mitigating environmental harm. By how much, though, is a contentious question: the environmental impact of blue hydrogen is a bit more blurred than for green. The production of blue hydrogen requires methane as a feedstock (a fossil fuel, although the lowest carbon one- energy efficiency considerations come into play); carbon capture (more efficiency questions) and storage (possible, if tricky.)  

So blue hydrogen is by no means perfect, but it is a good start and it’s here, now, to help transport on its journey. While green hydrogen may be the ultimate net zero goal, it requires massive capital investment in manufacture and supply infrastructure , and won’t be deliverable at operational scale for years, perhaps even decades. Blue hydrogen would appear to have a valuable role to play in the journey to net zero transport. 

So let’s look in more detail at the four steps in the blue journey….


1 First step: natural gas 

For many advocates of net zero, this is the first bugbear – to get clean hydrogen fuel you have to start with a fossil fuel. A sleight of hand. Unclean. But purists beware: this is a journey. We have to start somewhere, and natural gas is a vector to decarbonisation - and at scale. 

Methane, the majority component of natural gas, after all, is the lowest carbon fossil fuel. So, here’s the first nuanced view – yes, blue hydrogen is derived from a fossil fuel, but it is the best one we have, is massively abundant, and environmentally better than oil and coal. It may not be the destination of net zero, but it’s on the way. 

First step on the journey. Let’s go.   

2 Energy and the big enemy - waste 

Conversion of one energy form to another always – always – consumes energy and so brings with it costs in terms of efficiency - so why bother converting natural gas to hydrogen? 

Blue hydrogen is made by the so-called ‘steam methane reforming’ (SMR) process (or using auto thermal reforming, “ATR”), in which methane and steam are mixed at very high temperatures over a catalyst. Out comes a suite of ‘reformed’ gases, minus lots of energy – hydrogen, carbon monoxide, carbon dioxide and others. 

To be called "blue", CO2 must not vented to the atmosphere (that would be "brown" hydrogen) but has to be captured and stored - to remove its agency as a greenhouse gas. So, the CO2 produced is separated and injected underground (or used in industry, for example curing concrete or in your Sodastream), and the hydrogen is purified and stored as a high-pressure gas. While energy is, for sure, consumed in this process, we gain a useful, zero-carbon energy source (hydrogen) and collect the CO2 in one place for removal. 

That’s why people go for blue: not perfect, but a firm step in the right direction.  

3 Carbon Capture 

Capture the carbon. It’s not straightforward. CO2 sometimes comes as a pure gas stream,but often it needs to be separated from other gases. As it’s an acid this is usually achieved with an alkali, most often a member of the amine family. So, the CO2-containing exhaust gas is given an amine wash to remove the CO2 which is subsequently liberated by heating, with the amines recycled and used again. The CO2 gas is then compressed for transport and pumping underground. 

SMR works fine, and has done for over a century, in providing hydrogen feedstock to industrial processes for immediate use. Still, to earn the moniker ‘blue’ the manufacturer needs to dispose of the CO2 by-product, and not exhaust it to the atmosphere. This capture process is 90-95% effective, meaning some CO2 inevitably escapes to the atmosphere - one reason why blue is often criticised. If you believe decarbonisation means zero-CO2, then blue isn’t for you. 

But if you appreciate that the manufacture of blue hydrogen is 90-95% preferable to brown hydrogen in its environmental impact, you’ll see it’s a great interim option until green hydrogen options become usefully scaled-up. 

And it’s a considerable improvement on burning diesel. 

4 Carbon Storage 

Store the carbon. Store? Yes, underground, deep underground, often in depleted reservoirs or other suitable geological features. Storage is predicted to be 99.99% reliable. Good examples come in Canada, which leads the world in blue hydrogen,and in Norway - another pioneer of blue. 

However, take-off has still been slow, mainly as a result of differing views on who should pay for it. Infrastructure investment, lack of regulatory support, uncertainty of the fate of the CO2 and environmental bodies’ reluctance to embrace it have all contributed to slow delivery. There are thousands of sealed reservoirs which have held natural gas for hundreds of millions of years, and there are other sealed geological features that can be used, where carbon dioxide will slowly turn into carbonate rock itself over time - even in as little as two years in the case of the rock used in Iceland. 

With some alignment between governments and industries, it can be done.


So that’s blue hydrogen. As we mentioned in an earlier blog, hydrogen colour is defined by its provenance. Blue is slightly more complex and depends on our ability to efficiently capture and securely store the CO2 created during production.  

Complex, yes, but ready now and ready at scale: blue hydrogen is a great leap forward on our journey to net zero transport and offers the road transport industry a relatively short-term route to cleaner operation- whatever the ultimate goal may look like. 

In our next blog, we’ll look at what needs to happen for commercial and public fleets to make the switch to hydrogen operation, and evaluate some of the alternatives available (LNG, biomethane and battery-electric vehicles). Come back to hear our thoughts.

If PHC's experienced specialists can support your organisation in decarbonising transport operations, then please get in touch with us.

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