Safe horizons: A critical review of the human, technical, and regulatory challenges/opportunities for ammonia as a marine fuel

This review provides an integrative synthesis of technical safety, human factors, and regulatory frameworks for marine ammonia fuel applications, addressing the fragmented study of safety in current research. As the maritime sector moves toward the IMO’s 2050 net-zero mandate, ammonia ( NH 3 ) has emerged as a cornerstone of the future deep-sea energy mix. However, its adoption introduces challenges and opportunities dominated by acute toxicity, requiring an enhancement of conventional safety practices mainly designed for flammability. This review analyzes state-of-the-art knowledge of ammonia as a marine fuel, framing loss prevention through four interconnected pillars: intrinsic hazards, process risks across the onboard lifecycle, engineering safeguards, and human factors. It identifies regulatory aspects to be considered including the need of a harmonized international code and mandatory crew competency standards under the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW) to complement the provisional IMO guidelines. Achieving tolerable risk levels does not only hinge on technical solutions, but also on the adoption of advanced safety paradigms, addressing both organizational resilience and systemic control, supported by human-centric design, specialized training, and a transparent "just culture”. The synthesized evidence indicates that the viability of a safe transition is significantly contingent upon positioning the seafarer as a key adaptive safety asset, a factor identified as critical for the systematic implementation of NH 3 within the emerging energy transition.