There Are More Colors of Hydrogen Than Green, Blue, and Gray—Meet Brown, Turquoise, and Purple

Say hello to brown, turquoise, and purple.

Making Brown Hydrogen in 1821
Making brown hydrogen in 1821.

The Monthly Magazine, 1821 / Wikimedia Commons / CC BY-SA 4.0

Everybody is talking about hydrogen these days. I have been skeptical about it for years: In the early days of Treehugger, it was being pushed by the nuclear industry, which was going to provide the electricity to make "green" hydrogen. The nuclear shills went quiet after the 2011 Fukushima meltdowns, but then the fossil fuel industry took over with "blue" hydrogen made from natural gas. The hydrogen was going to then be pumped into fuel cells to make electricity, which basically made it a really lousy battery. Hence my negativity.

Much has changed in the last decade. Real batteries got much better and cheaper, and almost nobody is talking about hydrogen as a battery anymore. But they are talking about it being used in steelmaking and as fuel for airplanes and ships.

There is also a lot of talk about cleaning up the vast quantities of hydrogen that are now made from fossil fuels. In our previous discussion of the colors of hydrogen, we listed "gray" hydrogen—made through steam methane reformation (SMR) from natural gas and makes up about 71% of the market—but didn't mention "brown" or "black" hydrogen made from coal, which is huge at 28% of the market and is rarely talked about.

Brown Hydrogen

Manufacture of Coal gas

James Reynolds / The Board of Trustees of the Science Museum / CC BY-NC-SA 4.0

Brown hydrogen is the oldest kid on the block and seems so primitive. That's how "town gas" was made in the 19th century, right through to the middle of the 20th century when it was replaced with so-called "natural" gas.

You basically take coal and expose it to oxygen and steam under high pressure, and you get what is now called "syngas," a mix of hydrogen and carbon monoxide. That's why in old movies and novels, people got killed with gas—carbon monoxide is deadly and odorless.

Making a kilogram of brown hydrogen puts out 20 kilograms of carbon dioxide, compared to 12 kilograms of carbon dioxide per kilogram of gray hydrogen made with natural gas. And the amount of that brown gas being made is huge. According to Allied Market Research, the market is worth $30.4 billion and will grow to $40 billion by 2030, mostly from China and India and mostly going into industrial processes like making fertilizer and refining petroleum.

No word on whether there is going to be any capture and storage of the CO2 produced in that massive increase. Brown hydrogen is a huge problem that nobody seems to be talking about.

Turquoise Hydrogen

This is the new kid on the block: It treats natural gas with high-temperature plasma in an oxygen-free vessel to separate the carbon from the hydrogen in methane, which is what natural gas mostly is. Because there is no oxygen, the carbon is a solid, known as carbon black, which has industrial uses and can even be buried to enhance the soil.

According to Reuters, the German natural gas industry recently asked the new government for $902.56 million (800 million euros) to build plants to make it. "The potential of turquoise hydrogen has not been sufficiently used in the past," said Timm Kehler, chairman of the Zukunft Gas lobby, at a virtual media conference.

Turquoise hydrogen is hot right now in the United Kingdom, with one company, HiiROC, promising shipping-container-sized units that can produce hydrogen that is as cheaply as steam-methane reformation without the emissions, and a fraction of the cost of "green" hydrogen made with electrolysis.

A Canadian company, PyroGenesis, has developed a "process for producing hydrogen from methane and other light hydrocarbons using thermal plasma without generating GHGs." According to the press release:

"PyroGenesis’ technology boasts a theoretical electricity cost 3 times lower than that of water electrolysis to produce the same amount of hydrogen making it one of the most energy-efficient technologies to produce ZCE hydrogen. The technology would be easily scalable, and its capital cost per hydrogen production unit is comparable to that of steam methane reforming technology, the most established commercial technology to produce hydrogen."

Turquoise hydrogen may be cheaper than electrolysis, but it still uses natural gas as a feedstock, which many consider problematic given how much methane is leaking during its production. But the gas industry will likely be pumping for this and we will be hearing more about it.

Wait, there's more: Purple Hydrogen

Purple hydrogen is made through electrolysis using nuclear energy, and is being considered by the European Commission. According to Euroactiv, "Using nuclear power for hydrogen production is known as “purple hydrogen” and offers the benefit of low-carbon emissions compared to the sort produced from natural gas – or grey hydrogen – which is currently the most widely available." The French are pushing for this to be considered green and sustainable.

Others call this pink hydrogen. And then there is red hydrogen, made through "the high-temperature catalytic splitting of water using nuclear power thermal as an energy source."

I suspect we will be hearing a lot about turquoise and purple hydrogen in the next few years, along with some new color for brown hydrogen that has carbon capture and storage, to make it sound nicer, as the nuclear and fossil fuel industries reach out for lifelines and subsidies to stay in business. We may run out of colors.

View Article Sources
  1. "The Rise of the Hydrogen Economy." Wood Mackenzie.

  2. "Economics." SG H2 Energy.

  3. Narune, Amit, and Eswara Prasad. "Brown Hydrogen Market." Allied Market Research, 2021.