Hydrogen pathways

CO₂ emitted while reforming fossil fuels

Grey Hydrogen

Feedstock
Natural gas or coal

Process
SMR/ATR/partial oxidation

Cost (USD/kg)
1.0–1.5

Benefits
Cheap and widely used

Challenges
Carbon emission

CO₂ captured and stored

Blue Hydrogen

Feedstock
Natural gas or coal

Process
SMR/ATR/partial oxidation + Carbon capture

Cost (USD/kg)
1.5–2.5

Benefits
Carbon is not released

Challenges
Additional cost of carbon capture and storage

Electrolysis: No emissions of CO₂

Green Hydrogen

Feedstock
Electricity and water

Process
Electrolysis

Cost (USD/kg)
4.0–6.0

Benefits
Zero carbon if renewable power is used

Challenges
High capex, high cost of renewable energy, water intensive