EMSA has published the first part of a study on the safety aspect of bunkering with biofuels, providing a comprehensive analysis of a pre-selection of biofuels in terms of safety aspects like flashpoint, toxicity, and cold-flow properties, among others.
he study looks at how those aspects can raise safety concerns during bunkering operations in a preliminary hazard identification.
EMSA identifying on the potential of biofuels in shipping, which identified a selection of biofuels as the most promising for maritime operations. These biofuels include bio-methanol, bio-FT-diesel, bio-DME, HVO, and FAME and relevant blends.
According to the report, bio-FT-diesel, HVO, and to a certain extent FAME share similarities with conventional marine distillates concerning hazardous properties relevant for bunkering. Consequently, it is rational to compare these with fossil marine diesels when identifying the risks. Bio-methanol, being chemically identical to fossil methanol, can leverage existing practices and regulations, as methanol is currently utilized as a marine fuel. Bio-DME, being gaseous under normal conditions, exhibits similarities with LPG fuels, enabling the utilization of LPG infrastructure, and opens the possibility of drawing inspiration from or aligning with established guidelines and regulations developed for LPG.
Summary of critical conditions
- Methanol has a lower flashpoint (9.7 °C) compared to traditional marine fuels (≥ 60 °C), requiring careful additional safeguards to mitigate the risk of fire and explosion hazards.
- Methanol’s normal boiling point is about 65 °C. This temperature is considered out of range for normal bunkering operations.
- Methanol can be corrosive to some materials (e.g., aluminium, copper, titanium, and polyvinyl chloride). Corrosion is prevented through the selection of materials in contact with methanol, or application of appropriate coating.
Miscibility and contaminants
- Methanol has a high solubility in water. Even solutions of methanol containing up to 74% water may be flammable.
- The Immediately Dangerous to Life or Health concentration (IDLH) of methanol is 6000 ppm. Primary risks related to methanol toxicity is through ingestion of the substance in its liquid state, but vapour inhalation and contact/absorption through the skin can also have harmful impact.
- Bio-FT-diesel may have a lower flashpoint than 60°C. As such, the IMO IGF Code could be mandatory, depending on the specified flashpoint of the bio-FT-diesel product.
- DME is a flammable gas under normal ambient conditions necessitating additional safeguards to avoid the risk of fire or explosion. The presence of surfaces above the autoignition temperature of DME (350 °C) is not considered credible during bunkering operations. However, sources of ignition still pose a risk.
- DME will liquefy if cooled (below boiling point at -24.8 °C at 1atm) or pressurized (above the vapour pressure at 5.3 bar at 20 °C).
- The freezing point of DME (-141.5 °C) is considered out of range during bunkering operations.
- If pressure drops below 5.3 bar at 20 °C, DME vaporizes, and due to the relative vapour density of DME (1.59) compared to air (1.0), becoming heavier than air and posing a risk of distant ignition or inhalation in confined spaces as it travels along the ground or water surface.
- HVO share the same flashpoint specification as distillate marine fuels (≥ 60 °C), requiring similar flammability precautions.
- Some HVO fuels, without additional cold flow processing, may exhibit poorer cold flow properties than MGO.
- Cold temperatures can cause fuel degradation, clogging and reduced flow capabilities. Cold flow properties differ among biodiesels, with the cloud point for B100, for instance, ranging from -5 to 20°C. Typically lower tolerance to cold temperatures than MGO.
- B100 flashpoint (≥ 101 °C) exceeds that of MGO (≥ 60 °C), signifying lower flammability. This temperature is not considered a credible risk during bunkering.
- FAME is more contamination-sensitive than MGO. Prevent water, oxygen, dirt, and rust introduction to maintain fuel quality. Exposure to water can facilitate for microbial growth and/or hydrolysis which may cause corrosion and formation of sediments.
- B100-compatible materials: carbon steel, aluminium, stainless steel, Teflon, Viton, Nylon, fluorocarbon, carbon filled acetal, fibreglass.
- Not recommended materials (B100): copper, bronze, brass, zinc, lead, tin, galvanized metal, nitrile rubber, butadiene, Hypalon, natural rubber, neoprene, Polypropylene, Polyurethane, Polyethylene.
Overview of Regulations & Best Practices – Safe Bunkering
The chosen biofuels vary when it comes to regulatory coverage and industry best practices in terms of their safe bunkering. Bio-methanol is the most mature, whereas HVO and FAME, exhibiting similarities in regulatory coverage, share commonalities with conventional marine diesels, potentially allowing for the leveraging of existing frameworks. Bio-DME, being gaseous and not commercially available, represents a somewhat unique position in this context and has little coverage. Among the selected biofuels, bio-FT-diesel has the least coverage.
For the safe bunkering of some of the biofuels, especially HVO, FAME, bio-DME and to some extent FT-diesel, an specific design approach as that taken by the Port of Singapore may be a valid method for ensuring safety. While bio-methanol can rely more on earlier industry experience and the specific guidelines that comes with that. A riskbased approach for their safe bunkering therefore seems the most appropriate until their use matures.
Regulations concerning the blending of these fuels have been considered and the safe bunkering of these blends should follow those guidelines. Other industries do not seem to take the same approach as the maritime sector, preferring a pure “drop-in” approach with a minimal impact to existing infrastructure and procedures for fuelling. Requiring a strict approval process for the fuel to ensure minimal operational impact to existing technologies. It should be noted that strict rules and guidelines may hinder biofuel adoption, while having a minimal positive impact on safety. Keeping the comparable risk in mind between a biofuel and a conventional fuel through a risk assessment seems an appropriate method for ensuring their safe bunkering, while promoting adoption. The following overview covers each biofuel specifically.