Luis Alfonso Díaz-Secades

Bioethanol is evaluated as a retrofit marine fuel candidate through a comparative assessment against liquefied natural gas (LNG) and methanol (MeOH) under the Energy Efficiency Existing Ship Index (EEXI), Carbon Intensity Indicator (CII), and Greenhouse Gas Fuel Intensity (GFI) frameworks. Fuel consumption profiles are derived from a multi-year empirical dataset using a dual-fuel (DF) engine retrofit, and lifecycle emissions are quantified across corn, sugarcane, and green algae feedstocks under IMO lifecycle guidelines. All DF configurations achieve EEXI compliance, whereas very-low-sulphur fuel oil (VLSFO) fails. A structural divergence emerges between regulatory metrics: under the tank-to-wake CII framework, MeOH and ethanol degrade to a marginal ‘D’ rating by 2027, while under the well-to-wake GFI framework the same configurations generate compliance surpluses from 2028 onward. Feedstock selection proves as consequential as fuel type, with bioethanol GFI ranging from 7.5 gCO₂eq/MJ for green algae to 56.4 gCO₂eq/MJ for corn. Cumulative surpluses reach 70,556 t CO₂eq for electro-fuels and 30,952 t CO₂eq for green algae bioethanol, whereas grey MeOH and VLSFO incur remedial costs of USD 3.91 million and USD 2.61 million, respectively. Despite a favourable price ceiling of 557.06 to 615.03 USD/t, the most favourable bioethanol pathway remains above this threshold. Ethanol therefore emerges as significant but not yet commercially viable.

The maritime industry is experiencing a critical shortage of qualified officers, partly associated with the demanding psychosocial conditions of seafaring. While Maritime Education and Training (MET) has traditionally emphasized technical competencies, psychological preparedness has received comparatively less attention in maritime curricula. This study presents a multi-cohort evaluation integrating the assessment of personality, mental health, workload, and fatigue in maritime students with the design and evaluation of psychoeducational interventions embedded in MET. Using a sequential cross-sectional mixed-methods design across three consecutive academic years, successive student cohorts were assessed using validated instruments, including the 16PF-5, GAD-7, PHQ-9, WHO-5, NASA-TLX, and SOFI-SM. Students generally showed adaptive psychological profiles, although a meaningful minority reported moderate-to-severe anxiety or depressive symptoms. Perceived workload and fatigue differed significantly across academic activities, with lower levels during practical sessions; shorter sleep duration was associated with greater perceived strain. Psychoeducational activities, including seminars, workshops, and conferences on maritime psychology, were positively evaluated by participants and perceived as relevant to their professional development. These findings support the feasibility and educational value of integrating structured psychoeducation, fatigue awareness, and mental health promotion into MET curricula, contributing evidence relevant to ongoing discussions surrounding the revision of the STCW Convention.

Maritime transport remains a significant source of air pollution and greenhouse gas emissions, while existing vessels face increasing pressure to comply with both local pollutant limits and emerging carbon intensity constraints. This study presents a sustainability-oriented techno-economic assessment of alternative sulphur compliance strategies using real operational data from a 1998-built cruise vessel. Three scenarios were evaluated: a counterfactual heavy fuel oil baseline, heavy fuel oil operation with open-loop scrubbers, and full switching to marine diesel oil. Pollutant emissions were estimated using a Tier 3-oriented approach, while fuel-related Tank-to-Wake greenhouse gas intensity, prospective carbon cost exposure, total cost, break-even fuel price spread and sensitivity analyses were integrated into a decision support framework. Results show that scrubbers reduce SO_x emissions by 96.9%, but increase fuel consumption, CO₂ emissions and NO_x emissions by approximately 3.6%. Marine diesel oil switching reduces SO_x by more than 99%, particulate matter by 88.8% and CO₂ by 4.6%, while also lowering prospective carbon cost exposure. However, under base case fuel price assumptions, heavy fuel oil operation with scrubbers remains the lower cost strategy, with a 2035 cost advantage of 4.03 to 5.30 million USD/year, depending on the carbon cost scenario. The findings show that the contribution of sulphur compliance strategies to sustainable maritime operation depends strongly on fuel price spreads, carbon cost exposure and remaining vessel lifetime under evolving regulatory conditions. By quantifying the trade-offs between local air pollution reduction, fuel-related carbon exposure and economic viability, this study contributes to sustainable maritime decision-making for aging vessels and supports compliance planning under regulatory uncertainty.

The increasing regulatory pressure on the maritime sector to decarbonize, driven in part by market-based mechanisms at the European level, is accelerating the development of onboard carbon management and energy-efficiency solutions. In this context, this study evaluates an integrated architecture that combines a CO₂ liquefaction system with organic Rankine cycles. The system captures 66% of the total CO₂ emitted by ship engines and is capable of recovering up to 2600.8 kW of energy from onboard hot and cold sources. To identify the most suitable working fluids, an extensive screening of 208 low-GWP zeotropic mixtures is conducted, assessing their thermophysical behavior and energy recovery performance. A detailed thermo-economic assessment is undertaken, including the calculation of CO₂-equivalent savings, GHG abatement cost, and payback periods. To account for fuel price variability, probabilistic modelling based on Monte Carlo sampling is applied to estimate the distribution of discounted payback outcomes. The results demonstrate that Novec 649-based zeotropic mixtures combined with the proposed architecture reduce fuel consumption and enhance onboard CO₂ management while remaining safe and economically viable across a wide range of operating scenarios.