In a statement, the classification society notes that apart from LNG (liquefied natural gas), all gases and low-flashpoint fuels are currently subject to the ‘alternative design approach’, meaning that “they may be used if their safety, reliability and dependability of the systems can be shown to be equivalent to those achieved by new and comparable conventionally fueled main and auxiliary machinery.”

It is further stressed that this development can take a lot of time and account to huge amounts of money as well as impede the uptake and expansion of lower emission alternative fuels.

Geir Dugstad, Director of Ship Classification & Technical Director at DNV GL – Maritime commented that “with the new rules and class notation, we want to offer owners interested in LPG a straightforward path towards compliance with the alternative design approach mandated by the IGF Code,” adding that

as the fuel environment within the maritime industry becomes more diverse, it is essential that we continue to broaden the enabling rules and regulation to support these new choices.

In July, DNV GL published the revised 'Assessment of selected alternative fuels and technologies in shipping', to provide decision support for investments in ships, for the following five to ten-year period.

The published paper provides an insight to technical parameters and limitations, subtracting accounting for local market conditions, considerations and incentive schemes which may have a significant impact on competitiveness and the uptake of alternative fuels and technologies.

DNV GL has noted that selected alternative ship fuels are

  1. LNG
  2. LPG
  3. Methanol
  4. Biofuel
  5. Hydrogen

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In particular, the rules and notation are based on DNV GL’s rules for ships using LNG as fuel but account for the differences in properties and phases between LPG and LNG, covering internal combustion engines, boilers and gas turbines for both gas-only and dual-fuel operations, as well as requirements for the ship’s fuel supply, considering all aspects of the installation from the bunkering connection up to and including the LPG consumers.

LPG as a fuel can lower a vessel’s emissions to air, both in terms of greenhouse gases as well as other pollutants. It virtually eliminates sulphur emissions and reduces GHG output by approximately 17% compared to burning HFO or MGO.

Moreover, LPG may act as a bridging fuel to ammonia, as the materials used for LPG tanks and systems is, in most cases, suitable for ammonia. With advanced planning, the adjustments needed for a switch to ammonia from LPG could also be minimized.

The World LPG Association (WLPGA) issued a Guide for LPG Marine Fuel Supply recently, which is dedicated to the use of LPG in the marine sector and its benefits. The report,  presents an overview of key LPG bunkering developments and how this potential infrastructure relates to major global shipping routes.

It was said that five are the main factors that make LPG appear an attractive alternative:

  • Compliance with emissions regulations: LPG enables vessels to meet MARPOL Annex VI requirements for both worldwide trades and operation in ECAs as its sulphur content that is well below the requirements for ECAs. LPG also reduces NOx emissions to levels that will meet MARPOL Annex VI without need for after treatment;
  • Economic and cost drivers: LPG has lower price than HSFO on a heating value basis. The main drawback of LPG are the uncertainties in future LPG price levels;
  • Share of operation time of the vessel spent inside ECAs;
  • Price difference between LPG and HFO, LSFO, MGO;
  • Investment costs for LPG tank and fuel system.