Marine Fuels 101: What Powers the Global Fleet?

Posted on Dec 27, 2024 at 08:12 PM

Because they power the ships that carry products across the world's oceans, marine fuels are essential to international trade and all its customers. However, these fuels are often overlooked by most stakeholders today. Should they be? Let's take a look at the past, present, and future of the most relevant marine fuels today and how they play a role in ocean industries

What are marine fuels?

Marine fuels, often known as bunker fuels, are global energy sources made especially for ships. Why? Because marine engines require a more potent, long-lasting fuel supply, these fuels are usually heavier than those used in automobiles or planes. Depending on the kind of vessels and the particular environmental standards it must follow, various marine fuels have different compositions. 

The term marine fuels, according to eionet, is defined as any petroleum-derived liquid fuel intended for use or in use on board a vessel, including those fuels defined in ISO 8217.

What's the difference between marine fuel and regular fuel?

So we know marine fuels are different than other fossil fuel products, how does that difference in specifications manifest?

The most noticeable difference is that marine fuels are often less refined and heavier. Marine engines employ thick, unrefined fuels like Heavy Fuel Oil (HFO), whereas automobile and jet engines use highly processed, cleaner-burning fuels like gasoline or jet fuel.

 This is because ships that operate for lengthy periods of time and across great distances have enormous energy requirements and therefore, vessels need fuel distillates that provide enough energy that are suited for the intensity and high demand of shipping transport.

The sulfur content is another important distinction. Historically, marine fuels, especially conventional ones like HFO, have had far greater sulfur contents than aviation or automobile fuels. The substantial air pollution caused by these high sulphur levels has led to new rules intended to lower emissions from the marine sector. In contrast, regular fuels used in cars must comply with stringent limits on sulfur to reduce their environmental footprint.

What is the most common marine fuel?

There's a wide range of fuel types in the market, including LSFO, HFO and more, each of these is intended to service a certain type of engine. Today, the most relevant types of petroleum a ship uses are divided into these five classes based on distillation, performance, quality and other properties. These marine fuels include:

• Heavy Fuel Oil (HFO): Historically the most common marine fuel, HFO is cost-effective but has a high sulfur content, contributing significantly to environmental pollution. However, it’s still widely used in international shipping.
• Ultra Low Sulfur Fuel Oil (ULSFO) or VLSFO, has become one of the most trusted options due to its compliance with the International Maritime Organization’s (IMO) 2020 sulfur regulations. It contains less than 0.5% sulfur, making it a clean option worldwide.
• Liquefied Natural Gas (LNG): LNG is a cleaner-burning alternative that reduces sulfur oxides, nitrogen oxides, and carbon dioxide emissions. Its adoption is growing, although it requires specific infrastructure for storage and use.
• Methanol: This alternative fuel emits fewer pollutants than conventional marine fuels and is compatible with existing marine engines with minor modifications.
• Biofuels: Derived from renewable resources like vegetable oils and animal fats, biofuels offer a sustainable option for the future. They reduce greenhouse gas (GHG) emissions, though their usage is still in the early stages.

Marine fuels: Past Vs Future

Currently, fossil fuels such as marine diesel oil (MDO), intermediate fuel oil (IFO) used in autonomous ships, and marine gas oil (MGO) power the vast majority of engines that power conventional commercial ships across the world. In 2021, these fuels powered almost 93% of all ships at sea (by tonnage).

However, in an effort for lowering the amount of ammonia emission produced by bunkering worldwide, the IMO has dedicated plenty of resources to transition from traditional marine fuels to better, more environmentally friendly solutions.

As we look into the future, the challenges of creating more sustainable maritime fuel options that meet the global standards are becoming increasingly apparent, with an emphasis of the impact of the maritime business of nature and global protection. The future of marine fuels is a balance between innovation and practicality, requiring the shipping sector to embrace new technologies and regulatory frameworks.

How to choose the best marine fuel?

Viscosity plays a key role in choosing the right marine fuel, and here’s why it's a part of all Maritime engineering courses. Viscosity is essentially how thick or thin a fuel is, which affects how it flows and behaves inside a ship's engine. 

Viscosity is often measured in a benchmark called centistokes (cSt), which is a standard unit for fuel oils in the US. When talking about marine fuels, understanding how viscosity is measured helps ensure the right fuel is chosen for the engine's needs. For instance, a fuel's viscosity is sometimes expressed in mm²/s, which is the same as cSt at specific temperatures.

For marine fuels like Heavy Fuel Oil (HFO), viscosity is typically measured at 50°C because these fuels are thicker and require heating to flow. High-viscosity fuels can have values between 180 and 380 cSt, while lighter fuels like Marine Gas Oil (MGO), which doesn’t require heating, usually have a lower viscosity around 2 to 11 cSt at 40°C.

In conclusion, marine fuels are undergoing significant changes as the industry adapts to evolving environmental standards and technological advancements. Ultimately, the transition to greener marine fuels is not just about compliance with regulations—it's about protecting our oceans and ensuring a more sustainable future for global shipping.