Most of the world’s trade is carried in containers on merchant ships. The issue of its environmental impact is critical for the future.
Overview of container shipping
In the 1950s, the introduction of containerization into world shipping revolutionized the sector, by standardizing the loading and unloading of vessels. Container carriers became the least risky and most economical means of transporting goods. According to the International Maritime Organization (IMO), 90% of world trade is now handled by sea in terms of volume, and 80% in terms of income.
Despite several crises since 2020 disrupting the industry, such as the Covid-19 crisis and the war between Russia and Ukraine, the phenomenon is set to continue to grow over the next few years. “We forecast that global demand for sea freight will increase by an average of 2.1% per year between 2024 and 2028”, according to Global Sovereign Advisory, a consulting firm specialized in financial and strategic issues, in a report of March 3. The United Nations makes a similar observation.
Key environmental impacts of container ships
Carrying the weight of world trade on its shoulders, and destined to continue growing, the industry cannot be held back. Yet the efficiency of container vessels comes at a particularly high environmental cost.
Air pollution: greenhouse gases, sulfur oxides, nitrogen oxides
Air quality is one of the most important environmental concerns surrounding the phenomenon. This is due to the release of various components, such as CO2, sulfur oxides and nitrogen oxides. “If shipping were a country, it would rank among the world’s top ten emitters”, recalled a number of Western governments on the opening day of COP27, the world climate conference in 2022.
In terms of CO2, global shipping accounts for 3% of global emissions every year. It is therefore responsible for over 940 million tonnes of CO2 emissions per year. According to the IMO, if nothing changes, this will rise to 17% by 2050. Container ships emit large quantities of carbon dioxide because of their size and the distances they travel. Transporting thousands of tonnes of goods over such long distances requires the use of heavy fuel oil, a particularly polluting, carbon-rich fuel.
Generally speaking, their marine engines are also very energy-hungry, and the high speeds imposed by globalization further increase their consumption. The high-temperature combustion of the fuel used also releases sulfur and nitrogen oxides. The problem is that they have a major impact on health, contributing to the build-up of both acid rain and tropospheric ozone. In Europe alone, this pollution is believed to be responsible for 50,000 deaths a year.
Water pollution: ballast water, oil spills, waste disposal
Shipping is all about water, and the environmental impact of container ships on water quality is another concern. The best-known problem is the discharge of oils and other waste into the seas and oceans. Accidental spills contaminate marine ecosystems, affecting flora and fauna. Illegal disposal of plastic, metal and even chemical waste is an equally significant concern. Today, 20% of these incidents still result from illegal discharges, despite the adoption of the International Convention for the Prevention of Pollution from Ships (MARPOL) in 1973/1978.
Less well known, ballast water also has a part to make. Used on board ships to stabilize them at sea, it is collected in a first marine environment, before being discharged at the end of the cruise, in a second environment. This system sucks in thousands of aquatic microbes, plants and small animals, carrying them all over the world. This greatly disrupts local ecosystems as a whole, notably through the introduction of invasive species.
Noise pollution: impact on marine life, underwater noise
Little known to the general public, noise pollution has a major affect on marine life. Maritime traffic generates anthropophony, a set of sounds resulting from human activity. This disturbs natural underwater sounds, known as biophony. It includes long-distance animal communication, cetacean navigation, foraging, reproduction, and even habitat preservation for corals and seabeds.
Physical impact: ship strikes, coral reef damage, coastal erosion
Finally, the physical impact of container ships also plays an important role. By 2024, collisions between small vessels and container ships are likely to be on the increase. This increases the risk of cargo loss, with the potential for containers to spill into the sea. According to ContainerZ, some 500 million containers are shipped around the world every year. This means that lost containers risk striking other vessels at sea. If it sinks, a container is almost irretrievable. They may also contain hazardous products, which are then dumped into the oceans. Every year, thousands of containers are lost, contributing to plastic pollution of the water.
When these colossal ships approach ports or operate, coral reefs can suffer considerable damage. This occurs via anchors and boat hulls. This contributes to the disappearance of entire ecosystems, which are already fragile by definition. The same applies to coastal erosion, intensified by port activities and dredging. These effects can have repercussions on other maritime sectors, such as the local fishing industry.
Solutions and strategies for reducing environmental impact
To prepare for the future, strategies are emerging to make container shipping more sustainable.
Technological innovations: alternative fuels, energy efficiency, emission reduction
In terms of innovation, the simplest short-term solution is to improve or even change the fuels used. Better-quality fuel oil would enable an initial reduction in emissions. Alternative fuels, such as liquefied natural gas (LNG), are increasingly being used. CMA CGM, for example, launched the LNG-powered container ship Jacques Saadé in 2020.
In the longer term, technological advances will enable more efficient engines, reducing fuel consumption and improving ship propulsion and aerodynamics. The Neoline project, for example, is developing a cargo ship combining sail and LNG fuel. Carbon capture and storage technologies are also being developed worldwide.
But investment and regulation must keep pace.
Operational strategies: route optimization, just-in-time arrival, cold ironing
The operational dimension has its part to play. Pollution from ships at dockside is often blamed on port structures. Electrical infrastructures can be proposed, combined with route optimization to ensure “just-in-time” arrival. This would make it possible to synchronize port operations once on site, while opting for the most fuel-efficient route. This could reduce CO2 emissions by up to 20% on certain trade routes. The Port of Rotterdam is already investing in cold ironing, encouraging ships to adopt the practice.
Environmental management systems: ISO 14001, ESI, Clean Shipping Index
International tools are available to support the cause. These include the voluntary Clean Shipping Index (CSI). It enables self-assessment of the environmental performance of ships, and encourages more sustainable shipping. Shipowners who improve their score over time benefit from economic advantages, such as reduced port charges.
In the same spirit, the Environmental Shipping Index (ESI) enables ports to distinguish ships by their environmental performance.
The international ISO 14001 standard defines the requirements for implementing an environmental management system (EMS). Since the beginning of 2024, all ships have also been required to calculate their energy efficiency index, in order to be able to declare their annual operational carbon intensity index (CII). The aim is to significantly reduce greenhouse gas (GHG) emissions. Indeed, in 2018, the IMO set an ambitious target of a 50% reduction in shipping-related GHG emissions by 2050. This refers to the MARPOL convention.
These standards and systems promote a culture of sustainability in the sector. However, in an extremely competitive sector, their implementation represents a significant cost, which slows down their adoption.
Regulations of all kinds have also been coming into force in recent years. For example, with regard to untreated ballast water, the BWM Convention, dated September 8, 2017, stipulates that all ships making international trips are required to manage their ballast water and sediments according to certain rules, in compliance with a ballast water management plan specific to them. Unfortunately, compliance with these regulations varies enormously from one geographical area to another, as well as from the shipowners in question.
Comparative analysis: container ships vs. other vessel types
Container ships generate between 10 and 32.5 g of CO2 per tonne-kilometre, posing a serious fine-particle problem. But container ships are not the only polluter of the oceans. What about other types of ships?
– The cruise liner: like a container ship, its sulfur oxide emissions could be equivalent to a million cars. What’s more, the quantity of wastewater discharged is another factor in worsening marine pollution.
– Ferries and other passenger ships: while their impact remains localized, ferries sometimes use the same fuels as container ships, raising the same challenges and issues. Their impact is less than that of a cruise ship, but far greater than that of land-based means of transport.
– Hydrogen-powered ships and other alternative fuels: still far from widespread, this developing technology has considerable potential to transform the environmental impact of the maritime industry. Autonomous ships are also part of this sustainable equation for the future.
