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Zero Emissions Shipping: Tackling Climate Change in the Maritime and Offshore Sectors

Global warming is an existential issue for the world. The international shipping industry is one of the leading causes of carbon emissions and fuel-related pollution in the world. Are there earth-friendly alternatives?

Data released by the maritime industry shows that a mere 15 of the world’s largest ships are equal in polluting effects all the cars on earth. Low-grade diesel used by the industry has 2000 times the sulphur content of diesel cars in the US and Europe. Shipping accounts for 3% of the globe’s CO2 emissions and one-quarter of emissions from global transportation, according to the International Maritime Organization (IMO).

Before 2018, the polluting effects of shipping had been ignored because there was no easy way to regulate a global, complex industry via national governments. However, in 2018, delegates to the IMO agreed to a 50% emissions cut from 2008 levels by 2050.

We need, however, to balance human consumption needs with the planet’s survival. Eighty percent of imports and exports by volume from the European Union, one of the world’s largest trading areas, are transported by cargo ship, and 11 billion tonnes of goods are transported worldwide each year.

We are dependent on shipping when it comes to feeding and catering for the human population. But is there a way of tackling CO2 emissions and fuel-related pollution in offshore shipping by using cleaner alternatives?

In this article, we consider the options currently on the horizon for zero emissions shipping.

Liquified natural gas (LNG)

LNG is a relatively available, cleaner and cheap fuel for shipping, emitting less carbon dioxide, nitrogen dioxides and sulphur oxides than diesel. It is the most widely used alternative to diesel in the industry, with plenty of investment in the pipeline, although it only accounts for 3% of ship fuel consumption.

However, recent studies, for example by the International Council on Clean Transportation (ICCT), showed that methane – the main component of natural gas – is 30 times a more potent greenhouse gas than carbon dioxide, and ships regularly emit around 3.7% of unburned fuel into the atmosphere. While it is popular with fossil fuel companies, it doesn’t appear to be a truly green alternative. Indeed, Nigel Topping, the UK’s High-Level Climate Action Champion on behalf of the UN climate conference COP26, called LNG a ‘dead-end’ fuel and said ammonia and hydrogen (see next sections) were the “most promising fuels.” Liquid petroleum gas (LPG), which combines butane and propane, doesn’t have the same emissions problems as LNG.


The ICCT has estimated that 99% of containerships crossing the Pacific could be powered by liquid hydrogen. To be considered green or clean, hydrogen has to be produced by electrolysis (using an electric current to split water molecules), though blue hydrogen – created from steam reforming – also has some green credentials. The first ship to use hydrogen as a hybrid fuel was Hydroville, a Belgium Kruibeke to Antwerp ferry.

Hydrogen is perhaps the easiest fuel to install, requiring the retrofitting of ships with hydrogen fuel cells. There is also a hydrogen-producing infrastructure – 70 million tonnes are produced for industrial use every year. It has been estimated to have at least 60% efficiency as a fuel. The technology is quiet and can be scaled for larger ships, and it only releases water vapour and oxygen, reducing airborne pollution.

The downsides are flammability (though storage solutions can offset this), the space needed for the fuel cells, and the cost of producing green hydrogen. The ICCT argues that government funding is necessary to help the transition towards zero emissions shipping and fund R&D.

According to a Global Maritime Forum study, out of 106 clean fuel projects for zero emissions shipping, nearly half were focusing on hydrogen.


Another option on the table is ammonia. It emits no carbon dioxide and has widespread availability, but it can also be made using renewable energy. It can be used by fuel cells and internal combustion engines, doesn’t need the high-pressure tanks or cryogenic dewars that hydrogen requires, and is potentially low-cost once ships have been converted. Remarkably, ammonia has ten times the energy capacity of a lithium-ion battery.

For these reasons, ammonia has generated a lot of interest in the shipping industry. However, as yet, no vessels are equipped to use ammonia, and there has no large-scale infrastructure to produce it in a carbon-neutral way. It’s been estimated it will cost £1.5 trillion to achieve the IMO’s emissions target.

However, there are a few projects underway. For example, in 2024, a ship called Viking Energy, owned by the Norwegian company Equinor, will be the first to be powered by green ammonia. Global consultancy DNV predicts that ammonia could account for 25% of maritime fuel by 2050.


Just as electric cars are becoming more mainstream, there is an option for ships to run on electric batteries solely or in a hybrid form. A report by Infineon says that 80% of ocean-going vessels have been using a diesel-electric transmission system to enable more efficient use of diesel. And the possibilities exist to use batteries in a hybrid system. Rolls Royce, for example, has launched a new and scalable ‘SAVe Energy’ lithium-ion battery for ships that can be combined with LNG or diesel.

However, the challenges are scalability, capacity and infrastructure. Batteries still have too low an energy density for the scale and distance needed by ships, and shoreside recharging points are still rare. China launched the first fully electric container ship for inland waterways, which only has enough charge for up to 80km.

For smaller vessels, solar power is also an option. The Tûranor PlanetSolar was one of the first solar-powered boats to sail around the world in 2012.


Biofuels are another alternative, also being investigated for on-land industry and as a replacement for coal without significant retrofitting. Biofuels are made from plant material and waste, are low sulphur, and, in theory, are capable of replacing fossil fuels for zero emissions shipping. However, retrofitting is needed. Biofuels are expensive, and, as yet, there is little capacity for producing replacement fuels for the entire shipping fleet. While there are concerns that the biofuels compete with food production, which would be environmentally and socially detrimental, new methods are emerging which avoid this conundrum, such as ‘solid state fermentation’.

A report by the European Technology and Innovation Platform said that, because of its limitations, the “market entry for biofuels in the marine sector is, therefore, most favourable onboard smaller vessels for coastal waters or use as auxiliary ultra-low sulphur fuel in ports.”

In 2019, a large A.P. Moller – Maersk Triple-E vessel sailed 25,000 nautical miles on a 20% biofuel blend from used cooking oil in a pilot supported by Dutch multinationals Friesland Campina, Heineken, Philips, DSM, Shell and Unilever. The companies revealed that the pilot was a success, accounting for 1500 tonnes reduction in carbon emissions and a 20-tonne reduction in sulphur emissions.

As one of the world’s major carbon emitters, shipping needs to find clean fuels to meet, or even better, exceed the IMO target. We’ve shown that there a range of viable alternative fuel options. Now we need the energy and will to tackle climate change and fight for a better, greener future.

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