LNG-powered oceangoing vessels becoming more common

Heavy fuel oil has long ruled the world's oceans. It has been mainly used by huge tankers with robust engines – and it still often powers these ships to this day. Cheap "residual fuel oil" (RFO), which is produced as a by-product in refineries, is available in different quality grades containing varying proportions of higher-quality fuel that has been left over. The sulphur content in particular varies. Purified fuel with an extremely low sulphur content is a requirement for entering an emission control area (ECA), like the North Sea, Baltic Sea, the coastlines around California and the rest of North America, as well as Puerto Rico's coastal waters. Sulphur filters, known as scrubbers, are often retrofitted to older vessels in order to purify the exhaust gases containing sulphur and nitrogen. In addition, the unwanted emissions include soot and particulate matter containing heavy metals.

Marine diesel oil (MDO), which is frequently used on smaller oceangoing vessels, produces far fewer toxic emissions. But the bottom line is that shipping remains a major cause of air pollution. The shipping sector is one of the ten biggest producers of greenhouse gases. Residents of port cities suffer due to the carcinogenic emissions in particular.

There is no disputing the fact that shipping has to end its dependency on fossil fuels sooner or later. When the MARPOL Convention was adopted back in 1973, many countries committed to protecting marine environments. This includes air. According to the "Initial IMO Strategy", by 2050 the industry aims to reduce total annual emissions by at least 50 per cent compared to 2008 levels and completely prevent greenhouse gas emissions. At the UN Climate Change Conference 2022 in Sharm el-Sheikh, the "Green Shipping Challenge" initiative reinforced the need to switch to climate-neutral propulsion. The USA was one of the countries behind this initiative. This raises hope that the USA will now also introduce national legislation for maritime traffic, creating a market for clean technologies. The EU is also currently involved in negotiations about legislation aimed at gradually limiting permissible emission quantities. The future belongs to ships powered by hydrogen or methanol, ammonia or LOHC (liquid organic hydrogen carriers) – fuels which are produced using hydrogen but are easier to transport and handle. It goes without saying that their production has to be "green", in other words climate-neutral.

But what needs to happen in the transition period up to 2050? Liquefied natural gas, known as LNG, which is mainly made up of methane, offers a possible solution here. It has been used in maritime traffic since back in the 1960s. It combusts far cleaner than marine diesel or even heavy fuel oil and contains no sulphur whatsoever. And that's not all – LNG-powered maritime engines are more efficient, improving their carbon footprint. However, methane is among the greenhouse gases with the greatest impact on the environment. This is why an LNG-powered maritime engine is only more environmentally friendly if the methane slip is under control in the upstream chain (e.g. during extraction and liquefaction) and in the maritime engine. If this is ensured, LNG can become a bridge technology. It would be possible to transition to sustainably produced bio-LNG at a later point without requiring any modifications to the vessel.

LNG carriers were the first ships to be powered at least partially by LNG. Some of the LNG produced on these vessels constantly evaporates. This boil-off gas can be used for propulsion. The world's first LNG tanker, the Methane Pioneer, was put into operation in 1958, mainly as an experimental vehicle. In its two successor ships from the same class, evaporating LNG was combusted in the ship's boiler. The steam produced was used to drive the ship's propellers via a turbine. From 2006 onwards, more and more efficient dual-fuel engines powered by methane or heavy fuel oil began to be used.

The Scandinavian countries, especially Norway, played a pioneering role in using LNG as fuel. This is where the Glutra Ferry was put into operation in 2000. This vessel is the first LNG-powered one that is not used to transport LNG. Many Scandinavian vessels have been converted since 2008. Ferries, cargo vessels and offshore supply ships are powered by LNG and bunkered at numerous small-scale stations along the Norwegian coast. In Sweden, Viking Grace, an LNG-powered, 200-metre-long ferry, has traversed the archipelago between Stockholm and the Finnish city of Turku since 2013. In the years that followed, an increasing number of LNG-powered ships were built – and their operators have had positive experiences with them, without few exceptions.

Since around 2017, an increasing number of shipyards have been building new ships with LNG propulsion or converting existing vessels. The world's first completely LNG-powered cruise ship, the AIDAnova, was put into service in 2018 to great fanfare. Other LNG-powered cruise ships have been built since then, including the AIDAcosma, the Mardi Gras from Carnival, the Costa Smeralda and the Costa Toscana, the Disney Wish and the Iona from P&O Cruises. Many others are under construction. Tui Cruises, Royal Caribbean and Princess Cruises will also commission LNG-powered cruise ships between 2023 and 2026. Some cruise operators like TUI Cruises highlight the possibility of operating their ships with environmentally friendly bio LNG or E-LNG. These companies report that their vessels will be able to run on green methanol in future. MSC Cruises is the first provider to use a combination of LNG and solid oxide fuel cells (SOFCs), which is intended to reduce greenhouse gas emissions by 30 per cent compared to the LNG engines that are usually used. The futuristic MSC World Europa was named in November 2022 in Qatar. It is currently the world's largest LNG-powered cruise ship. With the Havila Capella, an LNG-powered cruise ship that can run on battery power alone for four hours has even been in operation since 2021 (run by Norwegian company Hurtigruten).

It is more challenging to obtain an overview of the construction of LNG-powered cargo vessels. More than 640 LNG tankers alone are currently on the world's oceans. These are usually powered by boil-off gas. By 2025, the number of LNG tankers is expected to increase by around 200; they have already been ordered and are being constructed at present. Until now, Greek shipyards like Maran Gas have operated the largest fleets, but this is starting to change. Qatar, which has concluded contracts for the construction of 100 LNG carriers, will soon lead the rankings.

According to Sea-LNG, a multi-sector industry coalition dedicated to LNG, there are currently (as at the end of 2022) approximately 295 LNG-powered oceangoing vessels on the world's seas. Around another 510 had been ordered or were under construction at this point. Sea-LNG estimates that 10 to 20 per cent of newly ordered vessels are equipped with an LNG propulsion system, including bulk carriers, container ships and crude oil tankers in addition to cruise ships. CMA CGM Jacques Saadé stands out in particular, which is the first LNG-powered ship in the ULCS (ultra large container ship) class with a length of 400 m. It was launched in 2019. It was followed in 2019 and 2020 by another three ships of the same size from CMA CGM. The shipyard has a fleet of 26 LNG-powered vessels in total. At 200 m, it is not quite as big as the first car transporters, Siem Confucius and Siem Aristotle, which were put into service in 2019 and 2020, respectively.