ABS issued a white paper analyzing the top three factors one should consider when utilizing ammonia as a marine fuel, keeping in mind that ammonia has been in the spotlight lately as an alternative fuel for the shipping industry.
- Ammonia offers ship owners and operators a zero-carbon tank-to-wake emissions profile, regardless of fuel source.
- Ammonia’s toxicity requires stringent handling measures and permissible exposure limits to be followed.
- Although there are currently no prescriptive requirements surrounding ammonia as a marine fuel, demonstrating a vessel’s capability to operate on ammonia is advantageous.
According to the guide, ammonia is a compound of nitrogen and hydrogen and at atmospheric pressure and normal temperatures is a colorless gas with a characteristic pungent smell. At higher pressures ammonia becomes a liquid, making it easier to transport and store. The typical heating value for ammonia is similar to methanol. As with most alternative fuels, it has a lower energy density than fuel oils, so producing the same energy content would require about 2.4 times more volume as compared to petroleum-based fuels.
The fuel must be placed in specific storages and specific refrigerated conditions. Thus, the requirements of ammonia gas includ low-temperature service, pressurized storage tanks, flammable gases, and working with corrosive and toxic materials is key to addressing the safety hazards of using ammonia as a marine fuel. Some of the considerations when using ammonia as fuel on a vessel are listed below:
- Corrosion
- Design
- Equipment failure
- Cascading failures
- Safety management plan
- Personnel training to reduce human error.
In addition, ABS presents the pros and cons of using ammonia. Accordingly:
| Pros | Cons |
| Carbon free – no CO2 or soot | Toxicity |
| Low flammability risk – 15.15% to 27.35% in air | Fuel infrastructure |
| Can be produced from electrical energy – renewable | Lack of regulations |
| Easily reformed to hydrogen and nitrogen | Engine development at design stage |
| Can be stored and transported as a liquid at a practical pressure and temperature | Cost |
| Established commercial product | Corrosiveness to certain materials |
| Poor combustion characteristics for IC engine application |
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| Possible need for high percentage of pilot fuel | |
| Possible increased NOx emission | |
| Possible ammonia slip |
Concluding, to learn more about the paper, click here.
