Energy and transportation are fundamental building blocks of today's society and industry. Due to the depletion of fossil resources, we are faced with a large-scale shift toward alternative energy carriers. Hydrogen has exhibited great potential as a sustainable energy carrier. The question remains, however: How truly sustainable are hydrogen technologies? Life Cycle Assessment (LCA) can answer this question of sustainability based on a comprehensive evaluation of hydrogen production and the resources used. A key aspect of any LCA study is the definition of methodological choices during the goal and scope phases (e.g. allocation, system boundary, modelling, etc.). These choices demand a comprehensive knowledge of LCA and of the hydrogen production system. This book offers assistance by defining some of these choices. Furthermore, it instructs the reader on what other system-specific factors to consider in the study. This guidance document is structured according to the way LCA is performed and gives extensive information for those not familiar with LCA. Each chapter also contains a short summary with easy to understand provisions summarizing the choices and instructions.