From barriers to bundles: a risk-policy appraisal of alternative marine fuels

Abstract The transition to alternative marine fuels is often framed through fuel choice decisions, technical feasibility, or specific policy measures such as pricing, subsidies, standards, and training. Less attention has been given to governance at the port-shipping interface, where fuel availability, bunkering infrastructure, vessel deployment, safety readiness, investment timing, and sufficient demand must align under uncertainty. A comparative governance appraisal is therefore needed to identify which systemic risks warrant priority and which policy responses remain robust across stakeholder perspectives and transition horizons. This study addresses this need through an integrated risk-policy appraisal of the alternative-fuel transition. The analysis combines single-round structured fuzzy expert elicitation, descriptive rating-dispersion analysis, stakeholder-survey triangulation, and selected contextual indicators. Systemic risks are assessed to the year 2040, while policy instruments and 63 functionally feasible policy portfolios are evaluated for 2030 and 2040 under port-oriented and shipowner-oriented conditions. The findings suggest that transition fragility does not stem from a single hurdle but from interacting fuel supply constraints, fuel price volatility, policy instability, safety disruption, stranded asset exposure, and port–fleet misalignment. Under the salience dispersion screening rule, safety disruption and port-fleet misalignment emerge as the clearest relative fragility hotspots. A carbon levy shows the strongest robustness profile among the evaluated individual instruments, but the results do not support a pricing-only approach. Within the evaluated set, the preferred portfolio combines a carbon levy, CAPEX subsidy, standardisation/codes, and training/competence schemes. The study contributes a transparent comparative governance screening framework, linking risk salience, rating dispersion, instrument robustness, and portfolio risk coverage under uncertainty.