The colors of hydrogen – types of H2

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From green H2 to grey, blue, pink and turquoise, these shades represent the production method used.

Hydrogen colors are frequently used when discussing various types of H2 projects, their feasibility, and what they can do to help decarbonization efforts.

However, these terms are used without definition and are sometimes misused, creating some confusion.

To better understand what we are talking about in relation to this alternative energy source, it is better to know what the colors of hydrogen actually mean. After all, the technique used to produce H2 is what determines its degree of contamination.

The use of this colorless gas (or liquid) generally produces only water vapor, without any carbon or greenhouse gas emissions. But the same cannot be said of all production methods.

Therefore, understanding terms related to how fuel is produced will help you know what kind of carbon footprint its use will leave.

Currently, the most common shapes are white, green, gray, blue, turquoise, brown or black and purple or pink or red. Although this is more than likely increasing as new technologies are developed, these are the terms you are most likely to hear right now.

Here are the most common colors of hydrogen:

  • White: Simply denotes natural H2.
  • Green: It is a form of H2 produced by the electrolysis of water powered by renewable energies such as wind or solar. No greenhouse gas emissions are produced during the production of green hydrogen.
  • Gray: Gray hydrogen is produced from virtually any fossil fuel except coal. It uses steam methane reforming (SMR) and can produce a considerable amount of carbon dioxide and other greenhouse gases.
  • Blue: Blue hydrogen is made the same way as gray hydrogen, except it uses carbon capture and storage technology to capture most of the greenhouse gases in emissions and store them underground.
  • Turquoise: This color of hydrogen refers to the thermal separation of methane by pyrolysis of it. This method removes carbon in solid rather than gaseous form and remains an experimental method of H2 production.
  • black or brown: This hydrogen is produced using processes fueled by bituminous coal (black) or lignite (brown). The technique used for the production of H2 is called coal gasification, which is highly polluting and releases carbon dioxide and carbon monoxide in abundance into the atmosphere, among other by-products.
  • purple, pink and red: These hydrogen colors refer to the H2 produced by nuclear power plants. The purple form uses nuclear energy and heat to separate water by combined electrolysis. Pink uses electricity generated by a nuclear power plant to power water electrolysis. Red uses thermal energy from a nuclear power plant to power high temperature catalytic water separation.

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