Worldwide greenhouse gas emissions of green hydrogen production and transport

Large-scale introduction of green hydrogen is envisioned to play an important role in reaching net-zero greenhouse gas emissions. The production and transport of green hydrogen itself is, however, not free from emissions. Here we assess the life-cycle greenhouse gas emissions for 1,025 planned green hydrogen facilities, covering different electrolyser technologies and renewable electricity sources in 72 countries. We demonstrate that the current exclusion of life-cycle emissions of renewables, component manufacturing and hydrogen leakage in regulations gives a false impression that green hydrogen can easily meet emission thresholds. Evaluating different hydrogen production configurations, we find median production emissions in the most optimistic configuration of 2.9 kg CO₂ equivalents (CO₂e) kg H₂⁻¹ (0.8–4.6 kgCO₂e kg H₂⁻¹, 95% confidence interval). Including 1,000 km transport via pipeline or liquid hydrogen shipping adds another 1.5 or 1.8 kgCO₂e kg H₂⁻¹, respectively. We conclude that achieving low-emission green hydrogen at scale requires well-chosen production configurations with substantial emission reductions along the supply chain.