What is ‘slow steaming’ and why is the Red Sea crisis affecting shipping emissions?

Emissions from container ships transporting goods from Asia to Europe could increase substantially in light of the Red Sea conflict. This is because shipping lines are rerouting their vessels around the Cape of Good Hope instead of using the Suez Canal. To make up for the extra distance, they are also increasing their cruising speed. Doing so can put an end to nearly a decade of “slow steaming” – a strategy employed to save on both fuel costs and lower CO2 emissions, the Financial Times (FT) reports.

What is slow steaming?

In the 2000s, when bunker prices were rising fast, shipping lines implemented slow steaming by reducing their vessels’ commercial speeds from 22-33 knots to 18 knots or less (also known as “super slow steaming”). Since then, the strategy has evolved from a pure cost-reduction measure into a solution for absorbing overcapacity and reducing ships’ emissions.

International shipping generated 2% of global CO2 emissions in 2022, according to the International Energy Agency (IEA) – but with an upward trend. Bulk carriers, oil carriers and container ships are responsible for the large majority of these.

Slow steaming has been advocated as one way of reducing emissions, with supporting calculations showing that a 10% reduction in speed could result in a 27% drop in a ship’s emissions.

Although the size of slow steaming’s impact on emissions has been questioned recently, it remains a vital strategy for shipping lines in the face of growing regulatory pressures.