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.

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.

Adjusting to the geopolitical situation en route to the Suez Canal will challenge the global shipping industry’s ability to play its part in global efforts to halt the climate crisis.

As a result of the substantial increase in their journey time, shipping analysts Sea-Intelligence predict an increase in CO2 emissions of between 31% and 66% for journeys from Asia to northern Europe or the Mediterranean.

Adding to this is that the diversion will also lead to an end of slow steaming. Sea-Intelligence calculates that an increase in vessels’ cruising speed of around 1 knot will add another 14% in extra emissions for both routes.

Experts expect shipping companies to raise their current speeds of typically 14 knots by 1 to 2 knots, the FT reports.

Even more drastic changes could result from shipping operators deploying smaller, less fuel-efficient vessels to boost overall shipping capacity, Sea-Intelligence has calculated. Taken together, longer journey times, faster speeds and smaller ships could increase emissions by between 260% and 354% for the Northern Europe and the Mediterranean routes, respectively.

These projections will make it harder than ever for shipping to get in line with targets to lower its greenhouse gas emissions (GHGs) over the next few decades as regulators continue to clamp down.

For instance, ocean shipping’s regulator, the International Maritime Organization (IMO) raised its targets for greenhouse gas reductions last year.

Instead of the previous goal of a 50% reduction in GHGs, the IMO has set an ambition for shipping to achieve net-zero greenhouse gas emissions around 2050, with milestone checkpoints along the way. The sector’s carbon intensity must be reduced by a minimum of 40% by 2030, supported by a switch to alternative fuels with low or no emissions.

Meanwhile, the European Union has extended its Emissions Trading System (ETS) to include shipping from 2024. From 2025, shipping companies are due to pay for 40% of their emissions reported this year, increasing to 70% in 2026 and 100% as of 2027.

The new ETS rules apply to cargo and passenger ships from 5,000 gross tonnage and cover CO2 from this year as well as methane and nitrous oxide emissions from 2026. All journeys within Europe and those starting or ending in an EU port will fall under the ETS rules. Adding to the ETS is a range of other European frameworks, including the FuelEU maritime initiative.

Alongside regulatory targets, many carriers and cargo owners have set their own ambitious targets. For example, shipping-sector members of the First Movers Coalition (FMC) – launched as a partnership between the World Economic Forum and US Special Presidential Envoy for Climate John Kerry – are aiming for at least 5% of ocean shipping and 10% of the volume of goods shipped to be powered by zero-emission fuels by 2030.

However, for an industry whose efforts to lower CO2 emissions have already been pronounced “not on track” by the IEA, the longer route via the tip of Africa will come at a significant cost. At the same time, it underlines the need for future resilient routes where South Africa has the opportunity as one of several emerging economies to lead shipping's net-zero transition.

“Ship operators’ ability to efficiently route their vessels is highly impacted by geopolitical developments that require attendance to crew and vessel safety. This has an environmental impact and further emphasizes the importance of the sector transitioning to zero-emission fuels over time and the commitments made by members of the FMC,” explains Mette Asmussen, Lead of the Forum’s Maritime Sector Initiatives.

“It also underscores the critical role of South Africa in the bunkering network for global trade routes, as was recently highlighted in an FMC workshop in Cape Town on how to progress the opportunity of producing and bunkering green fuels.”