Analysis of critical operational risks and procedural requirements for safe bunkering of compressed gaseous hydrogen

Compressed gaseous hydrogen (CGH2) is increasingly recognised as a promising zero-emission marine fuel. However, its adoption introduces significant operational and safety challenges during vessel bunkering operations. Few studies have conducted risk assessments during bunkering operations and most Qualitative Risk Assessments (QRAs) primarily address the design of hydrogen-fuelled ships (Ioanna et al., 2025). This paper provides a structured analysis of critical risks and procedural requirements for safe and efficient CGH2 bunkering operations. The paper is based on research conducted through the European ZEAS (Zero-Emission Adriatic Ship) project. The aim of the project, which is co-financed under the Horizon Europe programme, is to design, develop and build a hydrogen-powered ferry. The ferry is intended to operate in the Adriatic Sea, and the research demonstrates that compressed gaseous hydrogen is a viable option for this type of ship operation (ZEAS consortium, 2024). The research used a hazard identification (HAZID) approach, applying a Risk Ranking Matrix (RAM) and guided by international standards and key regulatory frameworks, including IMO (International Maritime Organisation) and ISO (International Organization for Standardization) standards, recommendations and guidelines, to identify associated risks, procedural requirements and propose mitigation measures (International Maritime Organization, 2025). The research highlights the main operational phases of CGH2 bunkering and identifies key hazards, including hydrogen leakage, fire and explosion risks, material compatibility issues, human error, and environmental factors. Additionally, the research identified different hazards caused by the distinctive properties of CGH2, such as low ignition energy, wide flammability range, high diffusivity, and potential for asphyxiation, which require rigorous safety protocols, awareness and emergency preparedness (Cekerevac & Cekerevac, 2025). The Risk Ranking Matrix is used to systematically assess and rank these hazards within the ZEAS project tasks and requirements. The qualitative risk ranking and the use of a likelihood-severity matrix are consistent with IEC/ISO 31010:2019 recommendations for risk assessment (International Electrotechnical Commission & International Organization for Standardization, 2019). Analysis indicates that effective management of risks related to CGH2 bunkering operations requires a combination of robust technical barriers, such as redundant relief valves, automated leak detection, and emergency shutdown procedures, along with clearly defined procedural requirements, including standardised checklists, communication protocols, and designated exclusion zones around the bunkering area. Using a Risk Ranking Matrix, 10 significant risks were identified, with leakage at the hose connection and over-pressurisation in the bunkering line being the most critical. Following the risk assessment, mitigation measures were proposed to reduce these risks. Furthermore, the research identifies gaps in current regulatory frameworks, highlighting the need for implementation of site-specific operating procedures, mandatory personnel certification, continuous equipment auditing, and real-time environmental monitoring. Safe CGH2 bunkering depends not only on technical design but also on procedural discipline and organisational commitment to risk management. The methodology and findings presented in this paper offer applicable lessons for maritime stakeholders developing hydrogen bunkering infrastructure. Although lessons learned and best practices from natural gas can be applied as an initial starting point and benchmark (Leisner et al., 2024), the specific hazards of hydrogen must be considered during bunkering, and the regulatory framework needs to address these risks, primarily through IGF (International Gas Fuel Code) amendments (Georgopoulou et al., 2025). These insights support the transition toward zero-emission shipping and the advancement of coherent regulatory frameworks in this emerging sector, particularly in terms of risk management and mitigation. Complete HAZID workshops need to be conducted to fully identify and assess potential hazards for the CGH2 bunkering operation.