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[Display omitted] • Simulations provide reliable hydrogen production data for estimation of key indicators. • Hydrogen produced by electrolysis has larger EROEI than natural gas-based routes. • Green hydrogen appears the best solution in terms of LCOH for small-scale local production. • Green hydrogen performs better in terms of GWP, while other impacts should be improved. • TCO of hydrogen-fuelled vehicles is larger than diesel ones mainly due to purchase cost. Hydrogen is a versatile energy carrier and storage medium that may be employed in a variety of applications. According to the industrial processes used for its production, hydrogen may be labelled using different colours: (i) grey hydrogen, produced from natural gas using steam methane reforming (SMR), (ii) blue hydrogen, like the grey one, but with carbon capture and storage (CCS), (iii) green hydrogen, produced by water electrolysis using electricity from renewable sources only, (iv) "grid" hydrogen, produced by electrolysis using grid electricity. In this study, process simulation is used to solve material and energy balances, as well as to estimate capital and maintenance costs for each technology investigated. Then, process simulation outcomes are used to estimate three key performance indicators focusing on sustainability issues: the Energy Return on Energy Invested (EROEI), the Levelized Cost of Hydrogen (LCOH) and the Life Cycle Assessment (LCA). With reference to the case study of the Trieste port in Italy, the potential of synthesizing and utilizing hydrogen to fuel transportation activities within a port is examined. Based on the daily hydrogen consumption in fuel cells installed on locomotors and trucks, the design of the different processes considered is carried out, as well as their comparison in terms of EROEI, LCOH, and LCA. Furthermore, LCA and Total Cost of Ownership (TCO) evaluations for various hydrogen-fueled vehicles within the port are presented and compared to diesel-fueled ones to determine the impact of fuel-cell vehicles during operations. Results show that EROEI of hydrogen produced by electrolysis is larger than that produced by SMR with or without CCS. The LCOH for grey hydrogen is of the same order of magnitude of that of green or grid ones. The hydrogen compression step to 300 bar impacts on both energetic and economic performances. LCA indicates that the Global Warming Potential (GWP) of green hydrogen is at least half with respect to blue hydrogen, however other impact categories are less favourable. On the other hand, the TCO of hydrogen-fueled vehicles is higher than that of diesel-fueled ones, mainly because of the higher purchase costs. It is concluded that the methodology proposed in this paper, based on the evaluation of indicators at the design stage, is suitable for comparing hydrogen production processes. In addition, it is a powerful tool for policy decision-makers in defining the strategies for the development of hydrogen-based transport systems in port operations. [ABSTRACT FROM AUTHOR]