Green hydrogen is hydrogen gas produced by splitting water using electrolysis powered entirely by renewable electricity. It is important because it provides a clean fuel option for industries that are very difficult to decarbonise using other methods. Sectors such as steel, cement, glass, and chemicals require extremely high temperatures (1,000–1,600°C), which are hard to achieve reliably or cheaply with electricity alone, so they still rely heavily on fossil fuels.

In this work, the researchers examined whether using green hydrogen actually reduces emissions across different sectors, comparing it not only with fossil fuels but also with other low‑emission alternatives such as heat pumps, electric vehicles, and biofuels. They carried out a prospective life cycle assessment covering all stages of hydrogen (production, transport, and use) using projected 2030 conditions that include cleaner electricity grids, improved electrolyser efficiency, updated industrial processes, and expected hydrogen transport methods. They then compared green hydrogen to alternative technologies across eight applications: producing methanol, ammonia, steel, and aviation fuels; powering fuel‑cell passenger cars; providing low‑temperature domestic heat; supplying high‑temperature industrial heat; and balancing the electricity grid over long periods.

Across all eight applications, green hydrogen produced fewer emissions than fossil fuels, although often only marginally. However, when compared to other low‑emission technologies, green hydrogen often performed similarly or worse. This is because producing and transporting hydrogen still generates emissions, especially when the electricity used is not extremely low‑carbon, and because electrolysis itself is relatively inefficient. Green hydrogen only outperforms other clean options when it is produced using very low‑carbon electricity (such as wind power) and used on‑site without transport. Under these ideal conditions, it becomes the preferred option for ammonia and steel production, industrial and domestic heating, and long‑term grid balancing.

To maximise hydrogen’s climate benefit, emissions must be reduced across the entire supply chain, and hydrogen should be prioritised only in applications where it genuinely outperforms other clean alternatives. The authors propose a climate ladder to help rank and prioritise hydrogen use across sectors, guiding smarter policy and investment decisions.

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Research and development of hydrogen carrier based solutions for hydrogen compression and storage Martin Dornheim et al. (2022)