The Colors of Hydrogen

I must confess I’ve never thought of hydrogen as something that comes in several colors. My science background led me to believe that hydrogen is colorless, aromaless, and tasteless. Invisible, although powerfully explosive. I also never thought of it as a fuel until recently. More out of the box thinking in our world.

I’m currently diving deep into hydrogen research, in support of hydrogen refueling stations.

Hydrogen comes in 10 colors, but not actually, physically, different colors of hydrogen itself. The colors refer to how the hydrogen is produced, or reformed. Although hydrogen is the first element in our Periodic Table, believed to be both the most common and simplest in the Universe, it doesn’t actually often occur naturally on Earth.

Although some Hydrogen deposits have been discovered in the United States, Russia, and several other locations. Although the Hydrogen may be pure, transporting it would make developing these uncommercial.  

Most hydrogen is produced by electrolysis, applying electricity to water to split the oxygen out, leaving hydrogen. The source of the electricity provides the color notation: 

Green Hydrogen

Green Hydrogen is the preferred fuel for the up and coming hydrogen fuel cells and cylinders intended to be the new motive power for transportation of all sorts, from cars to trucks to ships, and even airplanes. Electrolysis, the process of using an electricity-powered Electrolyser to split water into hydrogen and oxygen, is used. It’s called “green” because the electricity to produce it comes from green, renewable power exclusively. That’s wind, hydro, or solar power. Green hydrogen is by far the most expensive to produce. About five times as much as the other colors, the other sources of electricity.  

Laws, at least in the United States, are being written to require Green Hydrogen, because they are written for Zero Emissions targets by date, 2035, 2050, etc. The thinking (the hope) is that a way forward will be found that can produce the Green Hydrogen more economically.

Blue and Gray Hydrogen

The other method of creating hydrogen is by “steam reforming” it. Exxon Corp. has created a large facility in Baytown, Texas to do just that. They will inject very high temperature steam into methane (natural gas), which will reform it into its two component parts of hydrogen and carbon dioxide. If they capture the separated carbon dioxide, their process includes “carbon capture,” which means the carbon dioxide will be stored and this will be Blue Hydrogen. If not, it will be noted as “Gray Hydrogen,” much less environmentally desirable because the carbon dioxide will be released directly into the atmosphere, although cheaper to produce. Either of these hydrogens are significantly more economical to produce. But neither are a true “Zero Emissions” production method.

Brown and Black Hydrogen

These are made from coal through coal gasification. Brown Hydrogen from brown coal and Black Hydrogen from black coal. This process releases the carbon dioxide directly into the atmosphere. If the process includes storage of carbon dioxide, that is “carbon capture” and the hydrogen will be noted as Blue Hydrogen, even though it comes from coal.

Other colors include Turquoise, Yellow, Purple, Pink, and White, but hydrogen is a desirable fuel to develop only when it does not generate emissions in the process of its production.

For the purposes of developing hydrogen as a fuel, green and blue are the colors of choice.

With special thanks to www.csiro.au.