What is the difference between grey, blue and green hydrogen?

Hydrogen has no color. The color of the hydrogen refers to its production process.

• Grey hydrogen is produced using natural gas, releasing CO₂ into the air through the chimney.
• Blue hydrogen is produced in the same way as grey hydrogen (using natural gas), but here the CO₂ produced is stored underground instead of in the air.
• If the hydrogen is produced by green electricity through an electrolysis process, the hydrogen is referred to as ‘green’.