A Quantitative Risk Analysis during Truck-to-Ship Ammonia Bunkering

A primary objective for the sustainable development of the maritime sector is to transition toward carbon-neutral fuels, with the aim to reduce emissions from maritime transportation. Ammonia emerges as a promising contender for hydrogen storage, offering the potential for CO2-free energy systems in the future. Notably, ammonia presents advantageous attributes for hydrogen storage, such as its high volumetric hydrogen density, low storage pressure requirements, and long-term stability. However, it is important to acknowledge that ammonia also poses challenges due to its toxicity, flammability, and corrosive nature, presenting more serious safety concerns that need to be addressed compared with other alternative fuels. This study sought to explore the dispersion characteristics of leaked gas during truck-to-ship ammonia bunkering, providing insights into the establishment of appropriate safety zones to minimize the potential hazards associated with this process. The research encompassed parametric studies conducted under various operational and environmental conditions, including different bunkering conditions, gas leak rates, wind speeds, and ammonia toxic doses. EFFECTS, which is commercial software for consequence analysis, was utilized to analyze specific scenarios. The focus was on a hypothetical ammonia bunkering truck of 37,000 L refueling an 8973 deadweight tonnage (DWT) service vessel with a tank capacity of 7500 m3 in the area of Mokpo Port, South Korea. The study’s findings underscore that the ammonia leak rate, ambient temperature, and wind characteristics significantly impacted the determination of safety zones. Additionally, the bunkering conditions, leak hole size, and surrounding traffic also played influential roles. This study revealed that bunkering in winter resulted in a larger safety zone compared with bunkering in summer. The lethality dose of ammonia was affected by the leak hole size, time for dispersion, and the amount of ammonia released. These observed variations imply that ammonia truck-to-ship bunkering should be undertaken with carefully chosen suitable safety criteria, thereby significantly altering the scope of safety zones. Consequently, the risk assessment method outlined in this paper is expected to assist in determining the appropriate extent of safety zones and provide practical insights for port authorities and flag states contributing to the future sustainable development of the maritime industry.