LNG fuel for shipping is necessary for regulatory compliance

by Michael Hansen, Hawaii Shippers Council

A misleading October 6, 2024 letter to the editor of the Honolulu Star Advertiser, “LNG not right choice for new Matson ships,” opposes Matson’s use of Liquefied Natural Gas (LNG).

As LNG is an important fuel source to virtually eliminate most polluting emissions and significantly reduce carbon emissions, its necessary for people to properly understand its characteristics.

LNG is made by reducing the temperature of natural gas (NG) to minus 260 degrees Fahrenheit (°F) and its volume by 1/600 for efficient storage and transportation.

NG and LNG are comprised 95% of methane (CH4) with other higher alkanes (ethane (C2H6), propane (C3H8), butanes (C4H10) and pentanes (C5H12)) making-up the balance. The letter writer didn’t mention the main constituent, methane, which is a significant omission.

LNG is stored in double-lined cryogenic tanks (both onshore and aboard ship), which act like a thermos at ambient pressure without refrigeration. The LNG in storage continuously releases small amounts of NG known as “boil off gas” (BOG) as the LNG warms. The BOG must be removed to prevent pressure buildup in the tank. The letter claimed incorrectly that LNG is stored in airtight containers under pressure.

The letter asserts that LNG is too expensive, less energy efficient and dangerous, as compared to residual or heavy fuel oil (FO). While that was mostly true, it’s no longer legal for ships to burn that grade of fuel (containing 3.5% mass by mass (m/m) sulphur) due to a change in international regulations effective on January 1, 2020.

The writer did offer the caveat that the FO currently “being used is already very low in sulphur,” which is an acknowledgment of the new regulations. However, the Very Low Sulphur Fuel Oil (VLSFO) that meets the new standards is not as energy dense and economical as previous FO grades due to the additional refining required.

The new international shipping regulations, requiring a marine VLSFO with a sulphur content of 0.5% m/m or less, is known as IMO 2020. As these VLSFOs are relatively expensive and scarce, shipowners and operators have turned to alternatives by installing scrubbers (to continue burning 3.5% m/m sulphur FO) and using a distillate Marine Gas Oil (MGO) known as DMA with a sulphur content of 0.1% m/m, which are also expensive but often more readily available.

Note: Distillate MGO DMA with an IMO Sulphur content of 0.1% m/m is often confused with Ultra Low Sulphur Diesel (ULSD) with a sulphur content of 0.0015% m/m mandated for road use in North America and Europe. Often shipowners and operators must purchase ULSD rather than MGO DMA grade distillate due to availability. Refiners typically produce much more ULSD than MGO DMA to meet the land-based demand.

IMO 2020 was issued by the International Maritime Organization (IMO), an agency of the United Nations (UN). The IMO is requiring international shipping to eliminate all polluting emissions and decarbonize by 2050.

In addition, the containerships operated by Matson and Pasha in the Hawaii trade must comply with the North American Emissions Control Area (NA ECA), which extends 200 nautical miles from the Pacific and Hawaii coasts mandating a sulphur content of 0.1% m/m over roughly 20% of the voyage. At present this can only be achieved by burning MGO DMA, ULSD, LNG or methanol (an alcohol of methane).

To comply with these and future regulations shipowners worldwide are turning to alternative fuels primarily LNG to eliminate most emissions and significantly reduce greenhouse gases (GHG).

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