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Cracking the Hydrogen Colour Code

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John Armstrong's picture
Chief Operating Officer BPA

John Armstrong is an engineer whose career has spanned the extremes of the energy industry – giving him a front-row seat on the energy roller-coaster. He began his career constructing oil...

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  • Jan 27, 2021

Recently there has been more and more in the media about hydrogen as a future fuel. These discussions often talk about hydrogen using a colour coding – which has the potential to confuse an already complicated matter even further. I thought I had it nailed down for myself until I read an article about turquoise and pink hydrogen! Its more important now more than ever to be open about hydrogen and not hide carbon intensity behind an array of complex terminology. To support discussion I have pulled together a summary of here of where the colour coding is at right now. There is a pdf version to download here. Does anyone know if hydrogen produced from waste plastic has been given a colour anywhere? Please do let me know if you hear of any others and I will add them.

Hydrogen Colour Chart



Green hydrogen: Made through electrolysis using renewable electricity. Electricity is used to split water into hydrogen and oxygen.

Blue hydrogen: Grey, brown or black hydrogen bit with the carbon dioxide deep underground through carbon capture and storage.

Pink hydrogen: Similar to green hydrogen but solely using energy from nuclear power.

Yellow hydrogen: Similar to green hydrogen but solely using energy from solar power.


Turquoise hydrogen:Produced through pyrolysis. In pyrolysis instead of polluting CO2 gas a solid carbon by-product is produced. The feedstock is methane of even waste plastics. Pyrolysis works by heating products to an extremely high temperature in an inert atmosphere. The emissions relate to the fuel needed to heat the reaction.


Grey hydrogen: Hydrogen made from natural gas in a process called steam reformation. in which high temperate steam is used to split methane gas at high pressures.


Black hydrogen: Made from Coal (in a process like grey hydrogen) with no carbon capture. Even more carbon intensive than grey hydrogen.

Brown hydrogen: Made from Lignite (in a process like grey hydrogen) with no carbon capture. Even more carbon intensive than black and grey hydrogen. Lignite is compressed peat and generates a lot of carbon dioxide when combusted.

Download my pdf hydrogen colour chart here.

Matt Chester's picture
Matt Chester on Jan 27, 2021

Is there a level of oversimplification from using the color coding method? It definitely helps with short-hand and getting a point across quick, but I imagine the emissions from all green isn't completely the same, nor blue, grey, brown, etc., and the specific emissions per unit of hydrogen can and should be considered. Are those factors commonly calculated and published? 

John Armstrong's picture
John Armstrong on Jan 27, 2021


I 100% agree with you. I wanted to add indicative intensities here however the information is confused and not readily available. I hope putting it into a hierarchy was better than nothing but I think some better numbers would help.

With 95%+ oh hydrogen currently made through very carbon intensive steam reformation of coal or gas there is a risk the first decade of the hydrogen switch will actually be even worse for emissions than just sticking with current technology!

This might be a good question to the community!


Matt Chester's picture
Matt Chester on Jan 28, 2021

Thanks for the following up, and for offering it as a community question-- for any Community Members wanting to dive into this specific question, John has posted it as a Community Q&A here!

Audra Drazga's picture
Audra Drazga on Jan 28, 2021

Thanks for sharing this article.  I recently read another article on our site that discussed the trends of Hydrogen. The author referenced the different color hydrogen production methods.  I was not clear on the difference between green and blue.  Also, from our 2021 Trends and Predictions insights shared by the community, it seems Hydrogen is going to continue to be an area of focus this year - but many think still in the R&D phase.  Thoughts on this? 


John Armstrong's picture
John Armstrong on Jan 29, 2021


I think Hydrogen is really really interesting... all the technology exists (Steam Reformation, Electrolysis, Compression, Liquifaction). There are already even hydrogen pipelines in the US. It feels to me its all about economics and regulation rather than R&D....


Nadim Chaudhry's picture
Nadim Chaudhry on Jan 29, 2021

At World Hydrogen Leaders we have seen yellow used as hydrogen from nuclear power and also red which is from biogas with sequestration which would have the best emissions as it would be negative. There is a trial in Norway 


John Armstrong's picture
John Armstrong on Jan 30, 2021


That is really helpful...I think red won't be the last colour to be added!!

I will add that. Does that have the potential to be carbon negative?


Ed Dodge's picture
Ed Dodge on Jan 29, 2021

Methane, CH4, is our most plentiful and most cost-effective source of hydrogen, and natural gas pipelines provide a ready distribution system. The challenge is to move beyond conventional steam-methane reforming that produces CO2 and find another technique to split the carbon off from the hydrogen atoms in solid form as carbon black.

There are alternatives to steam-methane reforming. The Kvaerner process uses plasma to form carbon black and hydrogen from methane. 

Another option bubbles methane up through a column of hot liquid metal, the hydrogen separates off while the carbon pools and floats and is easily removed.

Capturing the carbon in solid form is better than blue hydrogen because you don't need to sequester CO2 which has major challenges of its own.

I don't understand why there has not been more interest from industry in moving beyond steam-methane reforming. Natural gas is already our primary source of hydrogen and methane is not a limited resource. Hydrogen pipelines are expensive and dangerous, but we don't need them since we have natural gas distribution already. All we need to do is improve methane reforming to capture the carbon in solid form rather than as CO2 then we can have all the hydrogen we want at much lower costs than using renewables to drive electrolysis. 


John Armstrong's picture
John Armstrong on Jan 30, 2021

I think this is a great point. Any process that gives you solid carbon is fantastic. I think the challenge is that there is already a lot of capital tied up in steam reformation plants and that technologies like these and pyrolysis still fill like they are in the R&D space.

Ned Ford's picture
Ned Ford on Jan 30, 2021

I think a lot of the confusion here has to do with people who don't yet see the shift in mission for hydrogen.  Thirty years or so Amory Lovins started a global conversation about the hydrogen economy based on thoughts about hydrogen fuel cells. 

What happened over the last decade made that at the very best a fringe application, and more likely a nothingburger.  The only role we can reasonably expect for hydrogen vehicles in the future, now that the electric car has slam-dunked the transportation issue is maybe offroad vehicles, some remote locations where for some reason a hydrogen storage facility makes more sense than electricity generation from solar or wind, and possibly some larger tranportation modes like trucks and buses.

This is simply because the modern electric car costs a small fraction of what a hydrogen vehicle can cost, and the price differential can only increase.

What hydrogen does offer though is a future in a sustainable world for the petrochemical industry, and storage.   These two functions are not easily separated because the future depends on the time when we have so much wind and solar generation that some of it is available at times when the customers aren't using electricity.  By "some" I mean enough of total generation to ensure availability of above-demand generation for at least twenty or thirty percent of the year.  

There are 8760 hours in a year.   Today we see above-peak generation potential for three or four hours per year, and ten years of anti-wind articles based on "negative pricing" as a result.  That's sort of like complaining about shock absorbers on a truck wheel because they aren't used all the time.

I've written here before about my work with MISO wind data.   When MISO gets 50% of its electricity from wind, about seven tenths of one percent will be above-demand potential.   When MISO gets 70% of its electricity from wind about 8.7% of total generation potential will be available above demand.

At eight or ten percent of the year, it begins to make sense to build a hydrogen facility to take advantage of what will inevitably be very cheap electricity.  The problem is of course that making pure hydrogen will compete with a whole lot of other processes which turn hydrogen from water into other chemicals.   Nine percent of U.S. natural gas is used to make ammonia fertilizer.   When electricity costs less than 1.5 cents per KWh it is cheaper to make it from water and air.

We already have wind farms selling electricity at less than 1.5 cents per KWh, but is anyone going to build an ammonia factory with its own dedicated wind farm, or are they going to wait for others to build the wind and solar power, and shift to solar ammonia when the above-demand resource is large enough to ensure a steady supply of cheap power?

My guess is that it doesn't matter.   What matters is building wind and solar as fast as possible, as much as possible, and doing so until we find out that there is a reason to stop.

We obviously need some large storage capacity to have 100% renewables.   Less obviously, we are unlikely to need any storage at all until wind or solar exceed the regional grid demand for a lot of hours.  I describe it as "until we have something to store".

Like most of the other uses for hydrogen, people are working on the technology today.  But hydrogen and storage won't come into their own until the cheap power emerges.   We simply won't know what makes sense at the time until the time comes.   Not because we can't make good projections.   But because it is impossible to know how all the pieces will fit together until the time arrives.

I have expectations for certain things.  I see the people who own some of those recently built combined cycle plants that barely top 50% efficiency, as having serious interests in running those plants on hydrogen, or perhaps on methane made from hydrogen stored in the existing natural gas storage network.

Maybe that sort of project will be built, and someone will pay more for the hydrogen to make ammonia out of it.   Or another hydrocarbon.  Or boat fuel.  I don't know, and I don't really care.

What I do know is that the hydrogen future can't exist in the way it promises, until we have that abundance of wind or solar generation that permits hydrogen to be cheaper than it is today.

So the colors are interesting, but none of those colors are changing the landscape by making cheap hydrogen, and only green hydrogen has a real shot at doing so.

We can assume both that people will build wind and solar for dedicated projects that need cheap electricity and that above-demand capability will emerge slowly.  Hopefully slowly is a decade or so, not two or three.  People are already building wind and solar in places with the best potential for dedicated purposes related to making stuff with hydrogen from water.

So it isn't like it won't unfold slowly over time.  There isn't a rapid tipping point.   But the time isn't here now.  All we have today is enough to see where the general direction is.

Hydrogen from reforming costs about $5.50 per kg.  We're going to see hydrogen for under $2, and perhaps closer to $1.  That is radical.  It still won't make fuel cells competitive with electric cars.  I don't know how to factor in the fact that some people still think it will.  But renewable gasoline will also be viable.  Renewable gasoline at least has a viable market for antique cars.  And maybe for a soft landing on the way to 100% renewable transportation.


Bob Meinetz's picture
Bob Meinetz on Jan 31, 2021

"What hydrogen does offer though is a future in a sustainable world for the petrochemical industry, and storage."

Ned, because 95% of hydrogen is produced by steam-reforming natural gas, we'd be better off, economically and environmentally, by skipping the carbon-intensive step of manufacturing hydrogen and powering transportation with natural gas.

We'd be even better off by skipping both renewables and gas and powering transportation with batteries charged by nuclear energy. Not "net-zero" emission electricity with an asterisk, but asterisk-free zero emission electricity.

Without any evidence hydrogen will ever be more economically produced with renewable energy, it will continue to be sustainable only in the fervent imaginations of solar and wind advocates.

John Armstrong's picture
John Armstrong on Feb 1, 2021

This is an important discussion. I do agree... green hydrogen needs green electricity. If electricity is so cheap that its worth making hydrogen with it then it will drive electrification even faster.

My gut feeling is you will need some kind of green fuel for 'heavy' applications like trucks, ships and aircraft. Most of the rest you could probably electrify. 

I think there is a risk that people switch first to electric heating/cars etc and that by the time hydrogen gets to people's houses nobody wants it anymore!

Audra Drazga's picture
Audra Drazga on Feb 2, 2021

It sounds like unfortunately the benefits of hydrogen are still dependent on the energy we use to produce it....we need somebody to figure out cold fusion (ala Elizabeth Shoe in the Saint) 😃

John Armstrong's picture
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