Two studies into the safety of alternative low-emission marine fuels highlight some alarming high-risk results for ammonia.
A Bureau Veritas report in collaboration with TotalEnergies aimed at derisking the use of ammonia, with a specific focus on leak mitigation and treatment, pointed to its toxicity posing several challenges.
And a Together in Safety report, distributed by Lloyd’s Register, evaluating the potential operational risks of LNG, methanol, hydrogen and ammonia, found that although ammonia scored “broadly acceptable” risk as a potential source of ignition, some of its risks were classified as high or “intolerable”.
Bureau Veritas said: “Ammonia presents several safety challenges, which must be addressed before it can be used on board ships,” citing its toxicity to humans.
The Together in Safety study, a collaboration between Lloyd’s Register, APM Terminals, Carnival Corp, Chevron, Euronav, AP Moller-Maersk, MSC Ship Management, the Oil Companies International Marine Forum and Shell, found methanol posed the least overall risk.
It was followed by LNG, hydrogen and ammonia, with the first two scoring nearly identical risk rankings mainly considered tolerable.
Ammonia’s high or intolerable risks included navigation scenarios such as grounding or collision leading to a hull breach, cargo operations in case of damage to equipment or vent mast, and leaks or loss of containment during bunkering, Lloyd’s Register said on behalf of Together in Safety.
Bureau Veritas said exposure to ammonia beyond certain levels and durations can have serious health consequences for crew members and other people on board.
“For shipowners and designers, therefore, a key challenge is to prevent accidental ammonia leaks during ship operations and bunkering,” it added.
Bureau Veritas and TotalEnergies compared the concentrations of ammonia in the air that would be problematic with those of LNG.
They found LNG becomes dangerous at around 50,000 parts per million (ppm), while ammonia starts to have health effects above 30 ppm when permanently exposed or around 300 ppm when exposed for one hour.
Modifications to design and safety distances should be much greater for ammonia than for LNG, they concluded. More stringent leak management on board and vapour gas processing is needed to avoid even small leaks reaching manned areas.
The Together in Safety consortium also found that LNG fared better than hydrogen in a vessel abandonment scenario due to loss of tank pressure control, tank breach or loss of propulsion.
Nick Brown, chief executive of Lloyd’s Register, said the Together in Safety report showed “how detailed and holistic risk assessments can identify and focus attention on the solutions needed for the safe use of alternative fuels”.
Bud Darr, MSC Group executive vice president, maritime policy, said that only by identifying and properly addressing safety issues would shipping reach its needed end state by which safety and net-zero greenhouse gas operations go hand-in-hand.
Laurent Leblanc, senior vice president, technical & operations, at Bureau Veritas Marine & Offshore, said further experiments and analysis are required to reach definitive conclusions.
“This preliminary study helped identify future areas to explore for derisking ammonia as fuel,” Leblanc said.
Additional tests could be performed for leak design scenarios, bunkering safety zones, bunkering arrangements and the effect of weather conditions, he added.
