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Current Hydrogen Production Methods

[Mohammed bin Rashid Al Maktoum Solar Park is a solar park spread over a total area of 77 km2 in Seih Al-Dahal, about 50 kilometers south of the city of Dubai]

- Overview

Although abundant on earth as an element, hydrogen is almost always found as part of another compound, such as water (H2O) or methane (CH4), and must be separated into pure hydrogen (H2) for use in fuel cell electric vehicles. Hydrogen fuel combines with oxygen from the air through a fuel cell, creating electricity and water through an electrochemical process. 

Hydrogen can be produced using diverse, domestic resources -- including fossil fuels, such as natural gas and coal (with carbon sequestration); nuclear energy; and other renewable energy sources, such as biomass, wind, solar, geothermal, and hydro-electric power -- using a wide range of processes.

About 95% of the hydrogen produced in the United States comes from natural gas. It’s created using steam methane reforming, which basically uses high temperatures to convert steam and methane into hydrogen gas and carbon dioxide. 

The challenge is, global demand for hydrogen and its emerging applications could increase by a factor of ten, surpassing our current infrastructure for producing and delivering hydrogen.  

- Current Production Methods

Currently, commercial variants of hydrogen, such as gray hydrogen and blue hydrogen, are produced in energy-intensive processes and are powered almost entirely by fossil fuels.

Blue hydrogen, similar to gray hydrogen, is produced from natural gas through a process called steam reforming, which combines natural gas and hot water in the form of steam. Carbon dioxide is a by-product of this process. 

Hydrogen, in itself, is a clean fuel. Manufacturing hydrogen fuel, however, is energy-intensive and has carbon byproducts. What is now called brown hydrogen is created through coal gasification. The process for producing grey hydrogen from natural gas throws off carbon waste. 

Although there is no universal naming convention for hydrogen, almost everyone can agree on the fact that the majority of today’s H production is either green, blue or grey. Unlike green hydrogen production, which uses electricity from renewable sources to split water into its chemical components -- hydrogen and oxygen -- gray hydrogen is derived directly from fossil fuels, typically by splitting natural gas into its own chemical components, carbon and hydrogen. Blue hydrogen is derived from fossil fuels in a similar fashion as gray, but paired with sequestration to capture the carbon emissions this form of hydrogen production generates. 

Blue hydrogen uses carbon capture and storage for the greenhouse gases produced in the creation of grey hydrogen. Green hydrogen production -- the ultimate clean hydrogen resource -- uses renewable energy to create hydrogen fuel. For example, water electrolysis used to produce long-duration hydrogen energy storage requires a lot of energy. That energy could come from renewables.

Both grey and blue hydrogen are currently cheaper to produce than green hydrogen, so some countries, including China, are using gray hydrogen to prompt the development of hydrogen-compatible infrastructure. The line of thinking is that this approach will enable the development of pipelines and other infrastructure compatible with hydrogen, so that when green hydrogen does become more widely available, China will be ready for widespread distribution. But in environmentally-minded regions such as the EU, gray and blue hydrogen lack social acceptance.


- White (or Green) Hydrogen

White hydrogen or naturally occurring hydrogen. Also known as green hydrogen, it is produced using renewable or low-carbon energy sources, unlike "gray hydrogen," which is produced from natural gas and has carbon emissions as a by-product.

White hydrogen is gaining attention as a potential clean energy carrier for a variety of applications, including fuel cells for transportation, energy storage and industrial processes. Its production is seen as a way to reduce greenhouse gas emissions and combat climate change while promoting a sustainable energy economy.

Green or low-carbon hydrogen will become cost-competitive by 2040, given increased scale and lower costs of renewables, along with higher costs for producing brown, grey and blue hydrogen. Utilities will need to include all colors of hydrogen in their scenario planning, especially those with zero emissions commitments.


Eiffel Tower_Paris_032821A
[Eiffel Tower, Paris, France - tinkerbell]

- Beyond Blue, Green, Brown and Grey

As with many things in life, the hydrogen world is not as simple as it first appears. We also have turquoise hydrogen. Turquoise hydrogen is a by-product of methane pyrolysis, which splits methane into hydrogen gas and solid carbon. Some consider that this makes turquoise hydrogen a low-emission hydrogen choice -- but this depends on the energy-hungry thermal process being powered with renewable energy and the carbon being permanently stored. 

After this, the colours start to get a bit blurred. Pink hydrogen also finds its place in the spectrum, referring to hydrogen generated through electrolysis powered by nuclear energy. Yellow hydrogen is used by some to refer to hydrogen made through electrolysis with solar power, while confusingly, others consider it as electrolysed hydrogen made using power of mixed origin — i.e. the mix of renewable and fossil power actually flowing through the grid. 

Finally, white hydrogen is naturally-occurring geological hydrogen found in underground deposits and created through fracking, although there aren’t viable exploitation strategies.


- Solar-Powered Green Hydrogen Production

Solar energy can be used to produce green hydrogen through two processes:
  • Water electrolysis: Solar energy is converted into electricity using photovoltaic converters. The electricity powers electrolyzers, which split water into hydrogen and oxygen.
  • Direct solar water splitting: A solar hydrogen panel uses photocatalytic water splitting to produce photohydrogen directly from sunlight and water vapor.
If realized using solar energy or other renewable energy, water splitting could be a promising way of sustainably producing hydrogen (H2) on a large-scale. Most photoelectrochemical water splitting systems proposed so far, however, have been found to be either inefficient, unstable, or difficult to implement on a large-scale.

Today, hydrogen is mainly manufactured using natural gas and other fossil fuels, making the otherwise green power more of a "grey" energy source from its inception to its final usage.

[More to come ...]

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