Process efficiency (HHV)

CCUS capture rate

CCUS targets combustion CO₂ too

Upstream CH₄ leakage

GWP CH₄ (100-yr)

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Grid CI

g CO₂/kWh

Aux power

kWh/kg

SMR hydrogen carbon intensity: stoichiometry, CCUS integration, upstream methane leakage (Howarth concern), and grey vs blue color classification.

Stoichiometric SMR: CH₄ + 2H₂O → CO₂ + 4H₂; 5.5 kg CO₂/kg H₂ at 100% efficiency.
Modern SMR HHV efficiency: 75-80% (legacy 65-70%).
Process/combustion CH₄ split typically 80/20.
CertifHy blue-H₂ threshold: ≤4.4 kg CO₂e/kg H₂.
Howarth (2021) showed upstream methane leak can dominate blue-H₂ CI when CCUS is high.
Standards: ISO 14687, CertifHy, IPHE, DOE H2A, IEA Future of Hydrogen.

SMR Carbon Intensity

Hydrogen LCA