The Potential of Shore Power to Mitigate Air Pollution in Seaports: A Case Study of the Port of Bremerhaven Based on Vessel OPS Capability

When a massive ship sits at a dock, it does not simply rest; it hums with the constant, noisy work of keeping its lights on, its refrigeration running, and its crew comfortable. For decades, the standard way to power these systems has been to keep the ship's own diesel engines running, burning fuel right next to the city. This practice, known as "hotelling," pumps a steady stream of smoke and fumes into the air surrounding the port, contributing to local health problems and climate change. The solution proposed by engineers and environmentalists is surprisingly simple: plug the ship into the land. By connecting to the electrical grid on the shore, a vessel can shut down its dirty engines and draw clean electricity instead. This technology, called onshore power supply, exists and works, but its adoption has been slow, caught between the high cost of building the connections and the uncertainty of whether it is truly cheaper or cleaner than burning fuel.

Researchers at the Institute for Maritime Economics and Logistics and Heriot-Watt University decided to cut through this uncertainty by looking at a real, working port: Bremerhaven in Germany. Rather than guessing at future possibilities, they examined the actual movements of thousands of ships that visited the port in 2024. They focused on three specific types of vessels that dominate the harbor: the boxy container ships that carry global goods, the massive cruise liners that bring tourists, and the car carriers that transport automobiles. The team gathered detailed records of every time these ships arrived and left, calculating exactly how long they sat at the dock and how much power they would have needed to keep their systems running. They then built a computer model to simulate three different futures for the port. In the first scenario, they looked at the reality of today, where no ships use shore power. In the second, they imagined a middle ground where only the ships already equipped to plug in would do so. In the third, they envisioned a complete transformation where every single eligible ship plugged in for the entire duration of its stay.

The results of this simulation reveal a stark contrast between the current situation and what is possible. In the baseline scenario, where ships continue to burn fuel, the port sees a massive bill for the damage caused to human health and the climate. The researchers calculated that the air pollution and greenhouse gases released by these ships cost society nearly 97 million euros a year in health damages and climate effects, a figure that is actually higher than the cost of the fuel itself. This hidden cost represents the price of respiratory illnesses and environmental degradation that the port community pays without seeing it on a fuel invoice. However, when the researchers switched the model to the scenario where only the ships currently capable of using shore power actually did so, the picture changed dramatically. Even this partial switch, involving just a fraction of the total fleet, slashed the total external costs by nearly a quarter, saving over 22 million euros annually. The most significant improvements came from container ships, simply because there are so many of them, but the reduction in harmful pollutants like nitrogen oxides and particulate matter was felt across all vessel types.

The most striking finding emerged when the team modeled a future where every ship that could use shore power actually did so. In this full adoption scenario, the operational costs for the port and the shipping companies dropped by 80 percent. The reason for this dramatic saving lies in the price of energy. In Germany, the government offers a special tax rate on electricity used for this specific purpose, making it significantly cheaper than buying marine fuel. Under these conditions, the cost of running the ships on electricity is far lower than the cost of burning diesel. Furthermore, the environmental benefits were nearly total, with external costs falling by more than 97 percent. The air around the port would become almost entirely free of the fumes that currently drift from the ships' stacks. The researchers noted that the only remaining fuel use would be for the brief moments when a ship is connecting or disconnecting the cable, or for very short visits where plugging in is not practical.

Yet, the study also offers a sobering reminder that technology alone is not a magic wand. The researchers pointed out that the cleanliness of the shore power depends entirely on how that electricity is generated. If the power grid is still burning coal or gas to meet the new demand, the pollution simply moves from the ship's chimney to the power plant's smokestack, and the climate benefits shrink. Additionally, the study highlighted a growing complication with liquefied natural gas, or LNG, a fuel that many new ships are switching to. While LNG is cleaner than diesel, ships using it often still need to burn off excess gas while docked, and many of these vessels are not yet designed to plug into the shore power system. This creates a mismatch where the newest, "cleaner" ships might not be able to use the cleanest solution available. The researchers also noted that the financial success of this plan relies heavily on the current tax breaks for electricity; without them, the cost advantage would disappear, and the transition would stall.

Ultimately, the study concludes that onshore power supply is a powerful tool, but it requires a coordinated effort to work. It is not enough for a port to build the cables; the ships must be retrofitted to accept them, and the electricity must come from a clean grid. The data from Bremerhaven shows that the potential for saving money and improving public health is enormous, but it is conditional. The transition requires ports, shipping companies, and governments to work together to ensure that the electricity is affordable, the infrastructure is ready, and the ships are compatible. For the Port of Bremerhaven, and potentially for ports around the world, the path forward is clear: plug the ships in, but only if the rest of the system is ready to support the change. The technology is there, the economic case is strong under the right rules, and the environmental payoff is immediate, but it demands a holistic approach that goes beyond simply installing a socket.