The fuel colour spectrum

Hydrogen itself has no color. However, we hear about blue or brown hydrogen. Similarly, methanol is colorless, but we hear about grey or green methanol. Same thing about ammonia. So, what’s the color spectrum of fuels?

Several types of technology are used to produce each fuel color and synthesize the rainbow of fuel.

Let’s explore the different meanings of these colors.

Green: Green Fuel = Produced by Renewable energy

  • Water electrolysis using renewable electricity forms green hydrogen.
  • Renewable and carbon-free processes make green ammonia.
  • Green methanol can be made by biological (anaerobic digestion), thermochemical (gasification), or electro fuel (power to gas) pathways.

Blue: Blue fuel = Natural gas + Carbon capture and storage (CCS)

  • Natural gas coupled with CO2 capture generates blue hydrogen. The process includes using steam reforming that combines natural gas and steam water to create hydrogen output and carbon dioxide as a by-product. This process involves the carbon capture and storage (CCS) necessary to trap and store carbon dioxide.
  • Steam methane reformation can create blue ammonia by combining the hydrogen output derived from the process with nitrogen. Like the above, the process involves capturing the carbon dioxide by-product.
  • Blue hydrogen with carbon capture technology can create blue methanol.

Grey: Grey fuel = Natural gas or methane + Steam methane reforming, No CCS

  • Grey hydrogen is made from natural gas or methane using steam methane reforming. However, this process does not include capturing the produced greenhouse gases.
  • Grey ammonia is produced from natural gas and is used as fertilizer. The process involves combining nitrogen extracted from the air with hydrogen.

Black: Black fuel = Fuel produced by black coal

  • Black hydrogen is the opposite of green since it is produced by black coal in the hydrogen-making process.

Brown: Brown fuel = Fuel produced by lignite

  • Brown hydrogen is made by lignite (brown coal) in the hydrogen-making process by gasification.

Turquoise: Turquoise fuel = fuel produced by methane pyrolysis

  • Methane pyrolysis produces solid carbon and hydrogen, known as turquoise hydrogen.
  • Turquoise ammonia is produced by pyrolysis, which converts methane into pure carbon and hydrogen and reacts with nitrogen to make ammonia. The turquoise is somewhere between green and blue.

Pink/purple/red: Pink fuel = Electrolysis + Nuclear energy

  • Pink hydrogen is produced through Electrolysis generated by nuclear energy and is referred to as purple or red hydrogen.

Yellow: Yellow fuel = Electrolysis + Solar power

  • Yellow hydrogen is made through Electrolysis using solar power.

White: White fuel = Natural geological process

  • White hydrogen is a naturally occurring geological hydrogen found in underground deposits.