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Hydrogen Fuel. What do the colours mean?

Hydrogen Fuel. What do the colours mean?

If you are slightly bewildered by the sudden emergence of hydrogen as a fuel - and the ensuing argument over all the colours, you aren't alone. Here's what it all means

When miner Twiggy Forrest started greening himself, realigning his call name back to Andrew Forrest and then Dr Andrew Forrest; things were getting weird. Then Forrest threw down the green gauntlet, told his brown mates that 'the party was over' and invited them to join him on the greener side of the fence.

Forrest is still a miner and has a lot to gain from controlling his own energy sources. He is also the first Australian to tackle the green hydrogen business opportunity at scale and with his escapades around the world, the conversations around hydrogen have amped up. It is Forrest who has a lot to do with the mainstreaming of the hydrogen conversation.

So what is hydrogen?

Hydrogen is the lightest gas in the world and if you remember your periodic table, the first element. Hydrogen burns easily when sparked which is why it is such an important fuel source. Of even greater interest is that it doesn't emit GHGs when it burns, like natural gas does. 

Extracting hydrogen and CO2

Hydrogen is colourless. The colours used to describe hydrogen relate to the way the gas is produced and have been assigned accordingly. That's where the bickering comes in - some methods are much cleaner than others. The process of extracting hydrogen emits CO₂ to differing degrees, and so, anything but green hydrogen is not a suitable pathway for reaching net zero emissions with hydrogen.

What is with the colours and the bickering?

The production of hydrogen uses a lot of energy and that is why the type of energy used becomes important. As the interest in hydrogen as a fuel source increases, the focus on fuel sources - defined by a colour has become important and of course 'greenness' is a central issue. There is some bickering still about both the meaning of colours and what greeen is, but we are using the World Economic Forum standard here.

This little infographic on Eco Business is pretty close to the most consistent popular labelling and I particularly like it because they've left off brown and black! One can only hope because they want this infographic to last a while and know that brown and black hydrogen are soon to be relics of the past.

Natural hydrogen

Hydrogen is the most abundant element on earth, but you can't just grab itout of the air, but needs to be separated from other elements. The most common way to separate it is to extract hydrogen from water (H2O) and that needs an electrolyser - which is powered by some form of energy - and a lot of it.  It's the fuels we use to power the extraction of hydrogen that defines the colours. 

Grey hydrogen

Grey hydrogen is the most common form of hydrogen at the moment and is derived from natural gas (methane and ethane), which is produced from fossil fuels.

Brown and Black hydrogen

While not on the little circle, there is also brown and black hydrogen. Brown hydrogen uses lignite coal (also known as brown coal) or oil. Black hydrogen is produced using bituminous coal – a tar-like substance.

Green hydrogen

Green hydrogen is the one you will have heard Andrew Forrest spruiking about as he seeks to make Fortescue one of the world’s biggest energy companies. It uses  renewable sources, such as solar or wind for the electricity to extract hydrogen.

Turquoise hydrogen

Turquoise hydrogen is still in the experimental phase and refers to a way of creating hydrogen through a process called methane (CH4) pyrolysis, which also generates solid carbon. As such, there is no need for carbon capture and storage and the carbon can be used in other applications, like tyre manufacturing or as soil improver.

Blue hydrogen

Blue hydrogen is produced using the same reforming process that is used to create grey, brown and black hydrogen, but the CO₂ that would ordinarily be released is captured and stored underground. Carbon capture and storage equipment is expensive, raising the price of the fuel, but it at least provides for low-carbon fuel production at a lower cost than green hydrogen. Blue hydrogen is still in the experimental phase.

Pink hydrogen

Similarly, to green hydrogen, pink hydrogen is created through electrolysis of water but pink hydrogen is powered by nuclear energy rather than renewables. The extreme temperatures from nuclear reactors could also be used in other forms of hydrogen production by producing steam for more efficient electrolysis, for example.

(Somewhat bizarrely, Eco Business reports that recently, Saudi Arabia’s energy minister Abdulaziz bin Salman said that female employees in the country’s energy sector are “happy” to see plans for pink hydrogen coming along. “We are very conscious of taking care of our female new recruits and new cadets, and we are becoming an extremely well-emancipated society,” the Saudi royal and politician told a World Economic Forum virtual dialogue.

Yellow hydrogen

Yellow hydrogen has varying definitions - it is either linked to solar power specifically, or to a mix of energy sources. 

Images: Richard Horvath (base image) / Infographic: Eco Business

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