What is Bunkering in Shipping & How Does it Work?

Eve Church
31 Jul, 2025
04 Mins read

a bulk carrier undergoing bunkering operations

Ever wondered what bunkering is, how it got its name and what fuels most modern commercial ships use?

Though it might not often be talked about outside of maritime circles, we’ll assume you’re curious enough to know more about bunkering to have clicked on this blog post!

Bunkering is an essential operation that ensures vessels are fueled and ready to set sail on their voyages. And for those of you asking, “What is bunkering in shipping?” you’re in luck, as in this blog post we’ll explore what bunkering is, how it works, and where it typically takes place.

What is Bunkering and Why is it Called That?

Bunkering refers to the process of supplying fuel to ships for their own use. The term originated from the days of coal-powered ships when coal was stored in bunkers on board. While the term has stuck, the fuel types and techniques have evolved dramatically.

Today, most commercial vessels are powered by liquid fuels, such as Heavy Fuel Oil (HFO), Marine Gas Oil (MGO), Marine Diesel Oil (MDO), and increasingly, Liquefied Natural Gas (LNG) and biofuels.

Bunkering is not only about pouring fuel into a ship’s tank; it involves meticulous planning, safety protocols, regulatory compliance, and logistical coordination.

What are the Different Types of Bunkering?

There are several ways to bunker a vesse l, depending on the ship’s location, the port facilities available, and the type of fuel used:

1. Ship-to-Ship (STS) Bunkering

This involves transferring fuel from one vessel (the bunker barge or tanker) directly to another vessel at anchor or while docked. It’s commonly used when port facilities are limited or when faster turnarounds are needed.

two ships involved in STS ship to ship bunkering ops

2. Truck-to-Ship Bunkering

Fuel is delivered to the dock via tanker trucks and pumped directly into the ship’s fuel tanks. This method is often seen in smaller ports or when only limited quantities of fuel are needed.

3. Pipeline-to-Ship Bunkering

At major ports with dedicated infrastructure, ships can be bunkered via pipelines that run from shore-side fuel terminals. This method is efficient and typically used for large-scale operations.

4. LNG Bunkering

As more vessels turn to LNG as a cleaner fuel alternative, specialized bunkering methods such as ship-to-ship, truck-to-ship, and terminal-based LNG fueling stations are becoming more common. All bunkering operations demand tight safety controls, but LNG bunkering in particular requires strict handling procedures due to its cryogenic nature and flammability.

What is the Bunkering Process?

Bunkering is a multi-stage operation involving careful preparation and execution to ensure safety, accuracy, and environmental compliance. Here’s how it generally works:

1. Pre-Bunkering Preparations

Fuel Ordering: The ship’s Chief Engineer communicates fuel requirements to the shipowner or operator, who places an order with a bunker supplier.
Planning and Scheduling: The supplier, port agent, and ship’s crew coordinate the delivery timing and method.
Documentation: Safety checklists, fuel quality certificates, and delivery receipts are prepared in advance.

a man working in a shore based maritime job standing on the dock with a clipboard

2. Safety Procedures

Pre-Bunkering Meeting ( Toolbox Talk): The ship’s officers and bunker supplier conduct a meeting to discuss procedures, signals, emergency stops, and communication channels.
Environmental Precautions: Drip trays, spill kits, and absorbent materials are positioned, and all valves and connections are double-checked to prevent leaks or overflows.

3. Fuel Transfer

Hoses or pipelines are connected, and the fuel flow starts at a low rate before increasing to the planned pumping speed.
Fuel is transferred under continuous supervision, with regular measurements taken using tank level indicators and sounding rods.

4. Post-Bunkering

Fuel lines are flushed to prevent contamination.
Hoses are disconnected and drip trays cleared.
Final measurements are taken and compared against delivery notes.
Both parties sign the Bunker Delivery Note (BDN), a legally required document that confirms the quantity and specifications of the fuel delivered.

a container ship bunkering in a port

What are Some Bunkering Locations: Where Does It Happen?

Bunkering can technically happen anywhere in the world, but certain ports are recognized as major bunkering hubs due to their strategic location, infrastructure, and availability of marine fuels.

Key Global Bunkering Ports:

Singapore – The largest bunkering port in the world, known for high efficiency, strict compliance standards, and availability of multiple fuel grades.
Rotterdam (Netherlands) – Europe’s largest bunkering center, offering a wide range of fuels, including LNG and biofuels.
Fujairah (UAE) – A crucial refueling stop for vessels transiting the Middle East and Indian Ocean.
Hong Kong – A major hub in Asia-Pacific for short and long-haul vessels.
Houston (USA) – The primary bunkering location for the Gulf of Mexico and U.S. East Coast trade routes.

Bunkering may also occur offshore at anchorage points or at intermediate stops during long voyages.

Are There Any Regulatory Oversight and Environmental Concerns with Bunkering?

With growing awareness of environmental impact, bunkering is subject to increasing regulation. The International Maritime Organization (IMO) has introduced several measures, including:

IMO 2020 Sulphur Cap – Limits the sulphur content in marine fuel to 0.50% globally (down from 3.5%) unless the vessel uses a scrubber. (See below.)
MARPOL Annex VI – Sets standards for emissions of nitrogen oxides (NOx), sulphur oxides (SOx), and mandates fuel quality reporting.
EU ETS & CII Ratings – Upcoming regulations will further influence fuel choice and bunkering strategies.

In response, suppliers are investing in low-sulphur fuels, alternative fuels, and digital bunkering systems to improve transparency and reduce errors.

a bulk carrier in port undergoing bunkering operations

Side Note: What is a Scrubber in Shipping?

A scrubber is a device that uses seawater to remove harmful pollutants, in particular sulfur oxides, from the exhaust gases emitted from a ship’s engine.

Final Thoughts

Bunkering is much more than simply refueling a ship: it’s a vital part of maritime logistics that requires precision, compliance, and coordination. As the shipping industry continues to decarbonize, bunkering will evolve to support new fuel types and cleaner operations.

For shipowners, operators, and charterers, understanding how bunkering works is crucial not only for cost management but also for meeting environmental standards and ensuring voyage reliability.

Whether it’s traditional fuel oil or emerging alternatives like LNG, biofuels, or even ammonia, bunkering will remain at the heart of global shipping for decades to come.