Publications

Hydrogen (H₂) is increasingly valued as a carbon-free energy carrier, however, the environmental impact of the different methods for hydrogen production are sometimes overlooked. This article provides a comprehensive overview of the environmental impacts and costs of a diverse range of methods for producing hydrogen. Ninety-nine life cycle assessments (LCAs) published between 2015 and 2022 are categorised by geography, production method, energy source, goal and scope, and compared by data sources and methodology. A meta-analysis of methodological choices is used to identify a subset of mutually comparable studies whose results are then compared, initially by global warming potential (GWP), then low-GWP scenarios are compared by other indicators. The results show that the lowest GWP is achieved by methods that are currently more expensive (∼US $4–9/kg H₂) compared to the dominant methods of producing hydrogen from fossil fuels (∼US $1–2/kg H₂). The research finds that data are currently limited for comparing environmental indicators other than GWP, such as terrestrial acidification or freshwater eutrophication. Recommendations are made for future LCAs of hydrogen production.