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The use of alternative fuels is a primary means for decarbonising the maritime industry. Liquefied natural gas (LNG) liquid hydrogen (LH2) and liquid ammonia (LNH3) are liquified gases among the alternative fuels. The safety risks associated with these fuels differ from traditional fuels. In addition to their low-temperature hazards the flammability of LNG and LH2 and the high toxicity of LNH3 present challenges in fuel handlings due to their high likelihood of fuel release during bunkering. This study aims at drawing extensive comparisons of the evaporation and vapour dispersion behaviours for the three fuels after release accidents during bunkering and discuss their safety issues. The study involved the release event of the three fuels on the main deck area of a reference bulk carrier with a deadweight of 208000 tonnes. Two release scenarios were considered: Scenario 1 involved a release of 0.3 m3 of fuel and Scenario 2 involved a release of 100 kg of fuel. An empirical equation was used to calculate the fuel evaporation process and the Computational Fluid Dynamic (CFD) code FDS was employed to simulate the dispersion of vapour clouds. The obtained results reveal that LH2 has the highest evaporation rate followed by LNG and LNH3. The vapour clouds of LNG and LNH3 spread along the main deck surface while the LH2 vapour cloud exhibits upward dispersion. The flammable vapour clouds of LNG and LH2 remain within the main deck area whereas the toxic gas cloud of LNH3 disperses towards the shore and spreads near the ground on the shore side. Based on the dispersion behaviours the hazards of LNG and LH2 are com parable while LNH3 poses significantly higher hazards. In terms of hazard mitigations effective water curtain systems can suppress the vapour dispersion.

Hydrogen is widely recognized as a promising clean energy carrier but its highly flammable and explosive nature presents significant safety challenges in its production storage transportation and usage. Addressing these challenges is critical for the successful integration of hydrogen into global energy systems aligning with the United Nations’ sustainable development goals to support the transition to a low-carbon future. This study aims to provide a comprehensive review of hydrogen safety through a metadata analysis framework focusing on risks challenges mitigation strategies and regulations for safe handling. Previous reviews have largely addressed general hydrogen safety concerns but none have systematically evaluated the issue from a data-driven perspective. This review fills that gap by analyzing research trends root causes of hydrogen’s unsafe handling such as its low molecular density broad flammability range and high permeability and exploring solutions such as chemical additives and gaseous inhibitors to improve safety. Utilizing bibliometric techniques and scientific mapping tools this study synthesizes extensive research spanning from 2000 to 2024 visualizing the evolution of hydrogen safety research and identifying critical areas for future inquiry. The findings contribute valuable insights into the safe deployment of hydrogen technologies offering recommendations for future research and regulatory advancements to mitigate risks and ensure hydrogen’s role in a sustainable energy future.

Hydrogen (H2) is emerging as a key alternative to fossil fuels in the global energy transition. This study presents a comparative techno-economic analysis of H2 and natural gas (NG) focusing on safety hazards energy output CO2 emissions and cost-effectiveness aspects. Our analysis showed that compared to NG and other highly flammable gases like acetylene (C2 H2) and propane (C3 H8) H2 has a higher hazard potential due to factors such as its wide flammability range low ignition energy and high flame speed. In terms of energy output 1 kg of NG produces 48.60 MJ while conversion to liquefied natural gas (LNG) grey H2 and blue H2 reduces energy output to 45.96 MJ 35.45 MJ and 31.21 MJ respectively. Similarly while unconverted NG emits 2.72 kg of CO2 per kg emissions increase to 3.12 kg for LNG and 3.32 kg for grey H2. However blue H2 significantly reduces CO2 emissions to 1.05 kg per kg due to carbon capture and storage. From an economic perspective producing 1 kg of NG yields a profit of $0.011. Converting NG to grey H2 is most profitable yielding a net profit of $0.609 per kg of NG while blue H2 despite higher production costs remains viable with a profit of $0.390 per kg of NG. LNG conversion also shows profitability with $0.061 per kg of NG. This analysis highlights the trade-offs between energy efficiency environmental impact and economic viability providing valuable insights for stakeholders formulating hydrogen and LNG implementation strategies.