Future fuels for shipping are dominating discussions across the busy halls at Asia’s largest maritime exhibition, Marintec China in Shanghai, this week. Gaining traction is liquefied petroleum gas (LPG), with a new study out suggesting the fuel has many advantages over LNG.
A joint study by DNV GL and MAN evaluated that LPG is at least as attractive an energy source as LNG, with shorter payback periods, lower investment costs and lower sensitivity to fuel price scenarios. Furthermore, there is considerable LPG infrastructure available around the world, including storage facilities, export terminals and coastal refineries with loading and unloading installations.
The use of LPG as a fuel will to a large degree avoid particulate matter and black carbon emissions. What is more, the combination of low production and combustion-related emissions results in an overall greenhouse gas emissions reduction of 17% compared to HFO or MGO, the study claims.
LPG is a mixture of propane and butane. Its density is higher than that of air, which means that in the event of leakage vapours will accumulate in the lower portion of the surrounding space. By contrast, natural gas boiling off LNG is lighter than air.
Therefore LPG requires a different approach to leak detection and ventilation than LNG.
Furthermore, LPG has a lower flammability range, with a lower explosion limit of 2%. On the other hand, LPG is less challenging with regard to temperatures since it has a higher boiling point and, unlike LNG, is not stored at cryogenic temperatures.
“LPG could act as a bridging fuel to ammonia since LPG installations in a ship may be suitable for ammonia, as well,” Christos Chryssakis, business development manager at DNV GL, stated. “Materials used for LPG tanks and systems will in most cases be suitable for ammonia, and the double barriers and other safety features required for LPG would be just as relevant for ammonia. Some adjustments may be necessary for an LPG-fuelled ship to convert to ammonia but may be limited in scope in many cases.”
By making appropriate arrangements when planning a newbuilding project, the need for adjustments when converting to ammonia at a later time could be minimised.
Ammonia has been making headlines at Marintec with one Chinese yard coming up with a design for a 23,000 teu ammonia-fuelled vessel.
Last month the World LPG Association issued a 73-page report on the potential for LPG bunkering around the globe. The report stated: “Today LPG is becoming a technically and economically feasible option as an alternative fuel for shipping. According to MAN, by 2028, all LPG VLGC newbuilds and about 30% of containerships newbuilds are going to use LPG as fuel.”