Techno-economic analysis of hydrogen supply chains frequently yields incomparable results, hindering reliable investment decisions. This is largely due to inconsistent scope definitions, particularly for Carbon Intensity (CI) calculations, and inadequate testing of critical assumptions. This thesis presents a comprehensive methodology and an open-source, tool-based approach to enhance the completeness and critical review of hydrogen supply chain evaluations. The framework, developed using the PyPSA library, integrates capacity expansion optimization, detailed techno-economic analysis with life cycle assessment to determine the Levelized Cost of Hydrogen (LCOH) and its associated Carbon Intensity (CI). The methodology is demonstrated through two distinct case studies for supplying hydrogen to the Netherlands: (1) Offshore production via wind-powered electrolysis with transport through a repurposed subsea pipeline to the Dutch hydrogen backbone, and (2) Importation of green ammonia from Morocco with subsequent onshore cracking to produce high-purity hydrogen.