The hidden hazard of green shipping: risk transfer in maritime decarbonisation

Experts predominantly evaluate maritime decarbonisation using carbon metrics, yet the shift from heavy fuel oil to alternative fuels could systematically transfer environmental and operational risks across hazard categories, life-cycle stages, and affected communities. This paper addresses the analytical gap in multidimensional risk governance. The Maritime Decarbonisation Risk Transfer Matrix (MDRTM) is constructed using a hybrid risk-transfer modelling approach. Key fuel pathways like heavy fuel oil, liquefied natural gas, methanol, biofuels, ammonia, hydrogen, and battery-electric are evaluated across six risk dimensions: carbon dioxide emissions, acute toxicity, fire and explosion hazard, aquatic toxicity, waste generation, and feedstock sustainability. Toxicological benchmarks, accident-frequency data, and regulatory thresholds calibrate the ordinal scores (1–5). Sensitivity analysis confirmed the ranking stability under plausible scoring variability. Carbon metrics alone prove insufficient for fuel pathway evaluation. Decarbonisation redistributes rather than eliminates risk: ammonia introduces critical acute toxicity, hydrogen presents critical explosion hazards, battery-electric systems generate critical end-of-life waste burdens, and first-generation biofuels transfer risk upstream to feedstock sustainability. Pathway rankings remain stable under sensitivity perturbations. The MDRTM offers a replicable screening decision-support tool integrating risk transfer theory, life-cycle staging, and comparative hazard quantification, enabling regulators and fleet operators to identify transferred risks for prioritisation in parallel with carbon reduction targets. It is not a substitute for detailed probabilistic risk assessment but a structured filter to flag pathways and dimensions requiring deeper investigation.