Life-cycle assessment of hydrogen systems: A systematic review and meta-regression analysis

The high expectations placed on hydrogen as a clean fuel have led to a growing amount of life-cycle assessment (LCA) studies of hydrogen-related systems. The multiple methodological choices and diverse technical characteristics contribute to a broad set of practices, resulting in significant variability even among similar systems. This study sets the basis for the development of harmonised guidelines for LCA of fuel cells and hydrogen (FCH) systems by analysing current LCA practices. The reviewed literature suggests that previous efforts on harmonisation of LCA methodological choices have led to common practices for certain choices, e.g. functional unit. However, an incomplete definition of some parameters hinders the interpretability of LCA results and hides the potential sources of variability in terms of LCA estimates. In this work, in addition to a systematic literature review of LCA of FCH systems to identify current practices and gaps, sources of variability were investigated for the life-cycle greenhouse gas emissions of hydrogen production systems through a meta-regression analysis (MRA). The MRA results show that the variability of LCA estimates in the literature can be explained by a limited set of qualitative (e.g. implementation of CO2 capture, among other technological choices) and quantitative (e.g. electricity consumption for hydrogen processing) variables. Although a certain progress towards common methodological choices in LCA of FCH systems was identified, further work is still needed to harmonise practices, as well as to extend the application of the proposed MRA approach to other life-cycle indicators for both identification of main drivers and harmonisation of LCA impact scores.