Green hydrogen is expected to play a crucial role in decarbonizing the energy system. Hydrogen refuelling stations are one of the key elements in the large-scale deployment of green hydrogen. However, the decarbonization strategy is usually only evaluated in the usage phase of green hydrogen. To investigate the climate change impact and mitigation potential of the deployment of green hydrogen in the sector of transport, life cycle assessment (LCA) is introduced in this book. Firstly, this chapter illustrates the framework of LCA, covering its concept, targets, and categories of life cycle impact, as well as its methods (assessment procedure, databases, software, etc.). Secondly, the system of the hydrogen refuelling station is analysed and examples of the inventories of key components of the hydrogen refuelling station are displayed. Thirdly, a case study of LCA for the EU deployment of green hydrogen in transport towards 2050 is demonstrated. Process-based LCA is conducted within four designed scenarios (with green hydrogen, with blue hydrogen, without green hydrogen, and baseline). The analysis shows that green hydrogen wins on the climate impact compared to the other two decarbonization scenarios and baseline by 45–86% climate mitigation potential. Finally, a future framework for assessment of green hydrogen deployment is proposed, which includes LCA other assessments such as non-climate impacts, hydrogen leakage, risk analysis, and integrating with multi-dimension sustainability analysis.