What do the different hydrogen colors mean?

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

Hydrogen colors are used frequently when discussing various types of H2 projects, their viability, and what they can do to help in broader efforts to decarbonize.

That said, these terms are used without definition and are commonly misused, creating confusion.

To best understand what investments, projects, and opinions have to say about this alternative energy source, it’s best to know what the hydrogen colors really mean. After all, the technique used to produce the H2 is what determines how polluting it is. The use of this colorless gas (or liquid) typically results only in water vapor, without any carbon or greenhouse gas emissions. The same cannot be said about all methods of producing it.

Therefore, understanding the terms relating to how the fuel is produced will help you to know what kind of carbon footprint its use will leave behind. At the writing of this article, the most common forms are white, green, gray, blue, turquoise, brown or black, and purple or pink or red. Though this will more than likely grow as new technologies are developed, these are the terms you’re most likely to hear at the moment.

The following are the most common hydrogen colors and what they refer to.

• White – This simply refers to naturally occurring H2.
• Green – This is a form of H2 produced through water electrolysis powered by renewable energy such as wind or solar. No greenhouse gas emissions are produced when making green hydrogen.
• Gray – Gray hydrogen is made using virtually any fossil fuel except coal (see brown/black below). It uses steam methane reforming (SMR) and can produce a substantial amount of carbon dioxide and other greenhouse gases.
• Blue – Blue hydrogen is made in the same way as grey, only it uses carbon capture and storage technology to take most of the greenhouse gas from the emissions and store it underground.
• Turquoise – This hydrogen color refers to thermal splitting of methane using methane pyrolysis. This method removes carbon in the form of a solid instead of a gas and remains an experimental method of H2 production.
• Black or Brown – This H2 is made using methods powered by bituminous (black) or lignite (brown) coal. The technique used for H2 production is called coal gasification, which is highly polluting and releases copious carbon dioxide and carbon monoxide into the atmosphere, among other biproducts.
• Purple, Pink, and Red – These hydrogen colors refer to H2 produced using nuclear power plants. The purple form uses nuclear power and heat to split water via combined chemo thermal electrolysis. Pink uses the electricity produced by a nuclear plant to power water electrolysis. Red uses nuclear power thermal energy to power high-temperature catalytic water splitting.

Interested in alternative energy and how hydrogen fuel works?

Many are wondering…is hydrogen energy the future? There are many signs that point to yes…some day, the world could rely on H2 to keep the lights on  – Learn more about How efficient is a hydrogen fuel cell.  Also, why big named companies like Rolls Royce, Shell, BP and more investing into green hydrogen projects for the near future – Read more about – Who is the largest producer of green hydrogen? Also, make sure to visit our H2 Learning Center.