What do the different hydrogen colors mean?

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

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

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.

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