The strong emergence of hydrogen as an alternative fuel for energy generation has gained a lot of traction recently, so much so that it is being dubbed as one of the greatest future energy generation fuels considered for large-scale uptake. The manufacturing of this fuel type varies, as it ranges from energy-intensive carbon-based methods down to those that use green energy.

The colour nomenclature that is voluntarily adopted by the global energy industry is used to distinguish the different processes that are used to manufacture hydrogen, and ranges from green to pink, differentiating the technology types used to produce hydrogen. 

The well-known colour variants of hydrogen are blue, grey, black, brown, turquoise, white, pink and green. This nomenclature is also not a standard naming convention, as it can vary between and across countries where some countries use more, and others fewer colours.

Some countries even further disaggregate a colour category, such as yellow hydrogen, which falls within the ambit of green hydrogen, categorising a particular or specific renewable energy source option.

I argue that the use of the term “green” to refer to hydrogen that uses a renewable energy source convolutes the term “green” in relation to its sustainability meaning and dumbs down the actual climate impact associated with the overall activity that produces green hydrogen as an end-product.

Blue hydrogen is the product of a process called steam reforming, where natural gas and water (which produces steam) are heated. From this process hydrogen gas is produced as the desired product, and carbon dioxide as a by-product. The process of blue hydrogen becomes unique in that the by-product is not released but is captured and stored. 

On the other hand, grey hydrogen is produced in a similar method to blue hydrogen, with the difference being that the carbon dioxide from that process is not captured and stored.

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The black, brown, pink and turquoise hydrogen variants come from environmentally insensitive processes which are also energy intensive. The black and brown variants use the gasification method, where coal as a fossil fuel is gasified to split its various chemical constituents. From this process, hydrogen can be produced in either a gaseous or liquid form, depending on the required end use. 

White hydrogen refers to the naturally occurring hydrogen that is within geologic deposits. Its extraction uses processes such as fracking, which also has its own negative impacts on the different states of the environment.

Turquoise hydrogen is produced through the pyrolysis of methane, with solid carbon coming out as a by-product non-abated. Last, pink hydrogen is derived from electrolysis powered by nuclear energy, which requires very high temperatures which ends up being excessive heat lost without further use.

Of more interest to me is green hydrogen. This is the variant that uses electricity which is regarded as “clean”, coming from sources such as solar PV and/or wind power, to electrolyse water. The electrolysers use a reaction that splits water into its components of hydrogen and oxygen and no polluting emissions are released in the process.

This form of hydrogen is, however, expensive due to the capital-intensive costs of erecting renewable energy infrastructure to power the process. It is also the least commercially available.

In order for the ‘green’ association of this variant of hydrogen to stick, greenhouse gas and/or carbon accounting on a project-by-project basis should be undertaken.

My dispute with the term “green hydrogen” is not about the process used to manufacture it, but its association with the term “green”. This term is supposed to refer to things concerned with the environment and its well-being. It’s not just a colour, but a reference to something that positively benefits the environment in its entirety. 

A major debate that is yet to be fully settled in scientific and engineering circles is about the carbon footprint of the so-called renewable energy infrastructure through its life cycle, from manufacturing to disposal.

One of the emerging issues that have been highlighted as among those which will cause problems in the near future is related to the end-of-life reuse and/or disposal of renewable energy infrastructure components (see, for example, Glaister and Mudd, 2010; Bonds and Downey, 2012; Ololade and Annegarn, 2013; Martin, 2020; Stone, 2020; Prendergast, 2020; Gordon, 2023; Paddison, 2023; Peplow, 2022). 

Back to the carbon footprint argument – components that make up the entire system that manufactures green hydrogen include platinum conductors and lithium-ion battery storage components which use materials mined from the ground, and in various parts of Africa, often through unethical means that include illegal informal artisanal mining as well as in slavery and child labour operations.

Are the steel, glass, gels and other components used all recycled and recyclable? We are yet to fully understand the real life cycle and carbon footprint of green hydrogen as an end-product besides knowing that only the energy input to its electrolysis process was from a renewable energy source. 

Checks and balances

In order for the “green” association of this variant of hydrogen to stick, greenhouse gas and/or carbon accounting on a project-by-project basis should be undertaken. The sources of materials used to manufacture the renewable energy infrastructure that powers a green hydrogen facility should also be known.

The end-of-life destination should also in some way be factored into understanding the operation’s entire life-cycle process. The entire process that produces the green hydrogen should in itself be verified as a net-zero carbon operation – only then can we comfortably associate this hydrogen type as being “green”, because it would have passed all rigorous checks and balances certifying it as being from an environmentally conscious and friendly operation from start to finish.

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If not, it should at least incorporate the necessary and adequate carbon offsetting to get it to be a net-zero carbon operation. 

We cannot accept the final output to be termed “green” if the entire process or part of the life cycle (including materials) of hydrogen production did not satisfy the requirements of a green operation.

This is because there is a very thin line between brainwashing and greenwashing, and scientists with the power of influence should desist from greenwashing and downplaying the real impacts of projects that are dubbed climate-change-response green projects.

Doing so may lead to false narratives where people will believe that as long as the output is seen as “green”, then the input and process shouldn’t matter much. This can then affect how carbon budgets and offsets are determined and deemed appropriate and/or adequate.

We should not let the interpretation of the term “green” be nonconventional or open-ended, leaving room to be either brainwashed or greenwashed. Therefore, it is imperative that we preserve the term so that it retains its strong, sustainable development-oriented meaning and is not loosely translated.

Should this term be loosely translated, it runs the risk of blurring already drawn and accepted scientific philosophical lines.

Let us advocate for formalising the hydrogen naming convention and also find a suitable reference colour for hydrogen produced using renewable energy.

The term “green” should only be used for an entirely green and net-zero carbon-emission based life-cycle process of hydrogen production. MD

Mpendulo Dlamini holds a master’s (MSc) degree specialising in climate budget tagging, climate finance, and integrated development planning from the University of Cape Town.