energy technology

The many flavours of hydrogen

Last week I introduced a new series on hydrogen. It’s a gas with all kinds of possibilities for a new energy future, because it burns clean. But it has to be made, and how you make it matters. If it’s made with renewable energy, you’ve got yourself a legitimately clean fuel. If you’re making your hydrogen plant from fossil fuels, there’s a good chance its no better than what we have already.

This is a matter of some debate, and it can get a bit confusing. To bring some clarity to proceedings, the industry has colour coded the various forms of hydrogen. Bearing in mind that it’s a colourless gas and it all looks the same in the end, here are the important ones.

Let’s start with the bad stuff.

  • Grey hydrogen refers to the common practice of extracting hydrogen from fossil fuels. Half the world’s hydrogen is made from natural gas at the moment, with 30% made from oil and 16% from coal. Coal gets its own designation as black hydrogen, the highly polluting process of coal gasification to produce hydrogen. Brown hydrogen is the same but with low quality brown coal, a resource so dirty that most people don’t want to burn it in their power stations any more. But it’s cheap and the industry is desperate to keep mining it, and so some see hydrogen production as a way to keep using those reserves. Japan and Australia have a deal to use brown coal and ship the hydrogen to Japan, using carbon capture and storage to lock the emissions away at the bottom of the sea. We’ll see if it works. If it does, it won’t be brown any more, it’ll be reclassified to blue.
  • Blue hydrogen is when you use fossil fuels in production, but use carbon capture and storage to make it zero carbon. The fossil fuel industry love it, because it gives them a huge role in an energy transition that might have sidelined them otherwise. It’s also a gift to governments in places like Russia, or indeed the UK, because they can continue to harvest the tax revenues of a thriving fossil fuel industry. Environmental groups say it’s greenwash, and that carbon capture and storage remains an unproven technology. The chair of a hydrogen trade body quit in protest recently because the British government’s hydrogen strategy has such a big role for blue hydrogen.
  • Green hydrogen is where things start to get more interesting. That’s hydrogen made with renewable energy in an electrolyser. It’s already being done in a few places, and could be most useful in places that have abundant renewable energy resources and a small population to use it. The Sahara desert and the Scottish islands, for example (two places rarely mentioned in the same sentence) could become exporters of hydrogen. This is clean production, and getting the price of electrolysers down low enough to compete with fossil fuels is one of the big priorities for those betting on green hydrogen.

Those are the important ones. There are other colours that get a mention sometimes, such as yellow (solar), dark green (biomass), turquoise (methane from waste) or variations on pink (nuclear). Some of these are more theoretical than others, and might be adding more heat than light at this point.

The main point is that grey, black or brown hydrogen shouldn’t have a big role in a clean energy future, though grey may serve as a transition fuel to help get production up to scale.

A lot of hopes are being pinned on blue hydrogen, and it’s generating a certain amount of hype in some circles. It’s not all greenwash – there are places where this could work, where they have natural storage facilities for CCS. But there are very good reasons to be sceptical, not least because it’s the fossil fuel companies telling us that this is a good idea. They haven’t proved themselves to be even remotely trustworthy on climate change.

If there’s a role for hydrogen – and I believe there is – then it has to be clean. The only guaranteed way to do that right now is with renewable energy, and so this ought to be the focus. Not to the exclusion of all else – there are other useful technologies in development. But any plan to use hydrogen more extensively has to have renewable energy at the heart of it.

In short, there’s a diversity of production methods for hydrogen. It isn’t inherently low carbon, and that’s why it needs to be treated with caution. Like bio-energy, it can be good or bad, and simple for or against positions aren’t helpful. When it comes to hydrogen, we always need to ask more questions.

Is it worth the trouble? Absolutely. There are some ingenious things we can do with hydrogen, and I’ll come onto those next.


  1. Professor Peter Edwards and his team at Oxford University have developed a process that can seperate hydrocarbons into Hydrogen and Carbon. It utalises a metal oxide catylist and low energy microwaves. There are no green house gases produced at all making it very friendly to the environment and an excellent way to produce Hydrogen, from waste plastic or methane. This is a ground breaking process and should be fully developed as soon as possible. Check it out on the internet and send the links to your MP.

  2. The transition isn’t going to be easy.
    Maybe they could add a hydrogen production facility next to a solar farm or turbine farm and use any excess power generated to create hydrogen. Then they could use that hydrogen for a turbine when the wind isn’t blowing at night.
    But there is too much variability in power generation from these sources to make the cost of building a hydrogen factory and a hydrogen-fired turbine.
    It still seems like an idea worth exploring.

    1. This is what Orsted are working on in Denmark. They’re testing a wind turbine with an electrolyser built into the tower, so that it exports hydrogen rather than electricity.

      As you say, the cost of hydrogen production is going to be the critical factor here – can the cost of electrolyers come down fast enough to make it the obvious solution for energy storage and back-up power?

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