Is Renewable Electrolysis Hydrogen Cleaner than LNG-Based Hydrogen with Carbon Capture and Storage (CCS)?

Is Renewable Electrolysis Hydrogen Cleaner than LNG-Based Hydrogen with Carbon Capture and Storage (CCS)?

1. Electricity Source for PV Manufacturing in China

• The global PV supply chain is highly concentrated in China (polysilicon → wafers → cells → modules).

• According to the International Energy Agency (IEA), coal accounts for the majority of electricity used in PV manufacturing worldwide—because most facilities are located in coal-dominant regions of China.

• In recent years, coal has provided ~56–60% of China’s total electricity, despite the rapid growth of renewables.

• This means the embodied carbon intensity of PV modules made in China is significantly higher compared to modules made in regions with low-carbon grids (e.g., Europe).

• Lifecycle assessments (LCA) report wide ranges: ~400–3,000 kgCO₂e/kWp, translating to several tens to hundreds of gCO₂e/kWh depending on assumptions. The trend is consistent: China-made modules carry higher embodied emissions than EU-made modules.

2. Electricity Source & Emissions in Electrolyzer Manufacturing (China vs. EU)

• Global electrolyzer manufacturing capacity is rapidly expanding, with China accounting for ~60% of new capacity in 2023.

• Chinese factories are powered mainly by China’s coal-heavy grid, whereas EU plants rely on grids with higher shares of renewables and nuclear.

• Result: electrolyzers made in China typically have higher embodied emissions than those made in the EU.

• LCA studies show the embodied CO₂ of an electrolyzer stack can be several tonnes CO₂ per large unit. Depending on lifetime output, this converts to ~0.5–1.5 kgCO₂/kg H₂. PEM stacks generally have lower embodied emissions than alkaline stacks.

• In practice, embodied electrolyzer emissions are smaller than operational emissions from electricity use—but not negligible.

3. Illustrative Quantitative Comparison (Assumptions)

• Electrolysis efficiency: 50 kWh/kg H₂.

• PV lifetime carbon intensity (LCA):

  • PV–China: 80 gCO₂e/kWh (coal-heavy manufacturing).

  • PV–EU: 25 gCO₂e/kWh (low-carbon manufacturing).

• Electrolyzer embodied emissions:

  • China: +1.2 kgCO₂e/kg H₂.

  • EU: +0.6 kgCO₂e/kg H₂.

Formula:
Lifecycle CO₂e per kg H₂ = (PV_LCA × 50 kWh)/1000 + Electrolyzer embodied emissions.

Results:

• Case A (PV China + Electrolyzer China): 4.0 + 1.2 = 5.2 kgCO₂e/kg H₂

• Case B (PV China + Electrolyzer EU): 4.0 + 0.6 = 4.6 kgCO₂e/kg H₂

• Case C (PV EU + Electrolyzer EU): 1.25 + 0.6 = 1.85 kgCO₂e/kg H₂

• Case D (PV EU + Electrolyzer China): 1.25 + 1.2 = 2.45 kgCO₂e/kg H₂

4. Reference: Blue Hydrogen (SMR + CCS)

• Without CCS: ~9–10 kgCO₂/kg H₂.

• With CCS (90% capture): residual ~1–2 kgCO₂/kg H₂.

• Methane leakage (0.2–1.5%) adds ~1–4 kgCO₂/kg H₂ (in CO₂-equivalent terms).

• Net footprint: ~2–6 kgCO₂/kg H₂, depending on leakage and CCS efficiency.

5. Comparison & Implications

• PV & electrolyzer both China (Case A, ~5.2) → higher than best-case blue H₂, similar to worst-case blue H₂.

• PV China + electrolyzer EU (Case B, ~4.6) → still above low-emission blue H₂.

• PV & electrolyzer EU (Case C, ~1.85) → clearly cleaner than blue H₂ in all scenarios.

• PV EU + electrolyzer China (Case D, ~2.45) → competitive with best-case blue H₂.

Key Takeaways:

• The origin of PV modules is the dominant factor: coal-based Chinese manufacturing can push “green hydrogen” into the same emissions range as blue hydrogen.

• Electrolyzer origin matters too, but less so than PV origin.

• To ensure hydrogen is genuinely “green,” projects must verify embodied emissions of PV and electrolyzers (through Environmental Product Declarations, low-carbon supply chains, or local manufacturing powered by renewables).