This study applies a robust techno-economic framework to explore four key decarbonisation pathways – unabated steam methane reforming (SMR), SMR with carbon capture and storage (CCS), biomass-based hydrogen (BIOH₂), and renewable hydrogen via alkaline electrolyser cells (AEC) – across 52 existing ammonia production locations in Europe from 2030 to 2040. These pathways are examined under various policy settings, including RED III, CBAM, RFNBO, and Low-Carbon Fuels directives.