Reducing the environmental and climate impact of shipping propelled by liquefied natural gas (LNG) requires the introduction of alternative fuels such as liquid biogas/biomethane (LBG) (Jivén et al., 2022). Today, only a small part of the biomethane produced in Sweden is liquefied into LBG and an even smaller part is used as fuel for shipping. The price and availability of biogas is governed by supply and demand in an international market where shipping, industry and heavy trucks demand biogas. The biogas then needs to be processed into upgraded biogas (biomethane) or LBG quality in order to be transported and used in the respective sectors inside and outside of Sweden. The trend is for a larger proportion of biogas to be liquefied into LBG. The market has thus gone from a local market, where biogas was produced in the city's wastewater treatment plant and the city buses ran on biogas, to an international market where biogas often is transported in the same way as fossil gas and marketed using the fossil gas together with certificates. The project "Renewable liquid biogas (LBG) for shipping in practice" was carried out by IVL Swedish Environmental Research Institute and RISE in 2023 together with stakeholders from the shipping sector, ports and industry organizations for biogas. The project has studied the conditions required to make LBG available to shipping in practice at Swedish ports. The study shows that the major obstacles to an established use of LBG in the shipping sector in Sweden today are pricing/willingness to pay that is affected by international market prices, lack of suitable logistical solutions as well as the absence of the piece of the puzzle that is the business model and cooperation needed to make available the large volumes of biogas that shipping may demand. The stakeholders in the project estimate their total need of biogas to 3 TWh in a short term, and 10 TWh in a longer term. The project has identified a number of conclusions and recommendations for future work, including that the potential for biogas is large and untapped, but that new solutions for the distribution and logistics of LBG are needed. There is a clear interest from maritime actors as they see biogas as a strategic solution and the dialog between actors in the industry remains important. A change in the tax system could be needed so that more actors can use the green gas principle for LBG. In addition, a functioning "marketplace" is needed, which simplifies for sellers and buyers of LBG, and agreements/contracts are needed that are longterm and to a greater extent based on the costs of producing and providing LBG.

Safe large scale hydrogen bunkering - Test and validation The project investigates the use of green hydrogen as a sustainable fuel for shipping. It focuses on developing and validating a new cylinder design with built-in cooling to handle temperature increases during bunkering. The project aims to validate and analyze this new cylinder design by manufacturing a prototype equipped with heat exchangers and conducting performance tests. The project has been carried out in three stages: prototype development, pressure and safety tests, and performance tests. The prototype tank passed both pressure and performance tests without leaking or visible damage. The cylinder design with built-in heat exchanger was found to be able to limit the temperature rise during hydrogen bunkering, enabling a higher fill rate and safe use. However, there are still open questions regarding a large-scale filling that should be investigated further in future projects to further optimize the process. Among other things, this applies to the influence of a plastic liner or a thinner metal liner, a larger tank volume, larger mass flows and realistic pipe/hose lengths and dimensions between the expansion valve and the tanks on board.

 Safe Hydrogen Bunkering Compressed gaseous hydrogen (CGH2) storage and bunkering represent a viable alternative marine fuel with the potential to be entirely fossil-free. However, the adoption of CGH2 introduces unique challenges and risks that require rigorous assessment to ensure its safe and efficient use. CGH2 is favored for its sustainability potential and comparatively lower economic demands relative to liquid hydrogen. Nevertheless, its physical and chemical properties necessitate enhanced safety measures. CGH2 exhibits a broader flammability range, lower minimum ignition energy, and faster combustion rates compared to conventional fuels such as methane. Additionally, its storage under high pressures exceeding 250 bar implies that leaks may lead to hazardous phenomena, including jet flames or deflagrations (explosions). This report emphasizes the safety of personnel, including crew members, terminal workers, and passengers, while investigating the hazards associated with CGH2 bunkering. To this end, existing literature and regulations pertaining to LNG and hydrogen have been reviewed, stakeholder interviews have been conducted for a Visby case study, and a Hazard Identification (HAZID) analysis has been performed. Key hazards identified include loss of containment due to leaks, pipe, or tank ruptures. To effectively manage the risks of CGH2 bunkering, preventive and mitigative strategies must address multiple dimensions. These include operational limits, technical and physical measures, placement and design considerations, hazardous zones, safety distances, and maintenance protocols. Equally important are human factors such as access control, the establishment of clear safety protocols, well-defined roles and responsibilities, and procedural routines. The individual risk measure is used to ensure that no crew, terminal worker, or passenger is exposed to unacceptable risks. Input values for the individual risk calculation, such as limit values, failure frequencies, and consequences have been reviewed. For calculating the individual risk, uncertainty regarding modelling, input parameters and operational practices needs to be carefully managed. The high frequency of CGH2-bunkering drives the risk due to an increase in the number of transfer operations and the time for the system in operation.

Society is changing ever faster, and tunnels are complex systems where performance is affected by many different stakeholders. These conditions suggest that safety management needs to be proactive and based on a systems perspective that acknowledges socio-technical theories. Although systems thinking principles are foundational in overarching European regulations and goals, system principles generally don’t affect tunnel fire safety design principles or engineering practice. In the countries investigated in this study, tunnel fire safety management (TFSM) builds on experience-based and risk management-based principles that are optimized independently system by system. This is usually done with limited consideration of how these systems are interconnected and affect the overall tunnel system. The purpose of this paper is to investigate how systems thinking could support existing engineering practice. The work presented in this article is the outcome of a collaboration between fire safety researchers and practitioners from five countries and three continents. Through three workshops, current TFSM principles have been compiled and discussed. It is suggested that tunnel safety regulations be redesigned to strengthen the ability of engineers to work in design teams using systems thinking principles.

Vehicles that are powered by gaseous fuel, e.g., compressed natural gas (CNG) or hydrogen (H2), may, in the event of fire, result in a jet flame from a thermally activated pressure relief device (TPRD), or a pressure vessel explosion. There have been a few incidents for CNG vehicles where the TPRD was unsuccessful to prevent a pressure vessel explosion in the event of fire, both nationally in Sweden and internationally. If the pressure vessel explosion would occur inside an enclosure such as a road tunnel, the resulting consequences are even more problematic. In 2019 the authors investigated the fire safety of CNG cylinders exposed to localized fires. One purpose of the tests conducted in 2021 reported in this paper is to investigate whether extinguishment with water, e.g., from a tunnel deluge system, may compromise the safety of vehicle gas cylinders in the event of fire. Steel cylinders handles the situation with localizde fire and/or cooling with water well. Composite tanks can rupture if the fire exposure degrades the composite material strength, and the TPRD is not sufficiently heated to activate, e.g., if the fire is localized or if the TPRD is being cooled by water, which prevents its activation.

The increased use of electric vehicles has raised a concern about firefighting measures including water spray fire suppression systems (often denoted “drencher systems”) and tactics and equipment used for manual firefighting on ro-ro cargo and ro-ro passenger ships. A test series involving testing of two pairs of geometrically similar internal combustion engine vehicles (ICEV’s) and battery electric vehicles (BEV’s) under as equal test conditions as possible were conducted to investigate the performance efficiency of the drencher system. In addition, manual firefighting equipment and tactics was evaluated on three BEV fire tests. It is concluded that a fire in the two types of vehicles is different but share similarities. However, a fire in a BEV does not seem to be more challenging than a fire in an ICEV for the drencher system design given in current international recommendations. Similarly, there are common (e.g., handheld fire extinguishers and hoses) and new (e.g., fire blanket and water-cooling device) manual firefighting equipment that effectively can be used to control or limit a BEV fire.

These proceedings include papers and extended abstracts from the 7th International Conference on Fires in Vehicles – FIVE 2023, held in Stavanger, Norway, April 24-25, 2023. The proceedings include an overview of research and regulatory actions coupled to state-of-the-art knowledge on fire related issues in vehicles, such as passenger cars, buses, trucks and trains, or related infrastructure, such as car parks or vehicle transport at sea. Fires in transport systems are a challenge for fire experts. New fuels that are efficient and environmentally friendly are rapidly being introduced, with emphasis on high energy density batteries. This rapid development, however, introduces new fire risks not considered previously and we risk getting a situation where we do not have enough knowledge to tackle them. In this context FIVE represents an important forum for discussion of the fire problem and for exchange of ideas. Fire protection in road, rail, air, and sea transport is based on international regulations since vehicles cross borders and the safety requirements must be the same between countries. Therefore, understanding of safety and regulations must be developed internationally and the FIVE-conference has a significant role to play as a place to exchange knowledge. FIVE attracts researchers, operators, manufacturers, regulators, rescue services and other key stakeholders. Of particular value is the mix of expertise and the international participation in the conference. The conference is unique as it includes fires in different types of vehicles. In recognition of the fact that many of the fire problems faced by these vehicles are the same, the solutions to them can also be similar. In the proceedings you will find papers on vehicle fire development, bus fires, alternative fuel and electric vehicles, and car park fires. We are grateful to the renowned researchers and engineers presenting their work and to the keynote speakers setting the scene. We sincerely thank the scientific committee for their expert work in selecting papers for the conference.