The Environmental Impact of Shipping: Pollution, Emissions, and Sustainable Solutions

Shipping has many potential negative consequences for the marine environment, adjacent terrestrial environments, and the atmosphere. Nearly all commercial ships in operation today are powered by hydrocarbons, which contribute to atmospheric pollution and increases in GHG. Ships may intentionally (dumping) or unintentionally (accidents, antifouling hull paint) pollute (e.g., oil, garbage, cargos, emissions) the ocean, land, or atmosphere. Besides suffering detrimental effects of pollution, marine mammals are affected by shipping noise and ship strikes. Light pollution from ships may alter navigational patterns of marine birds. Ships are vectors for invasive or alien species that may reside in ballast water, on a ship’s hull, or within a ship’s piping. Recycling or disposal of retired ships often releases toxic substances into the environment.

The following sections briefly introduce the environmental impacts of shipping.

Emissions and Climate Change. Although shipping is an efficient means of moving goods over short and long distances, the burning of fossil fuels for propulsion results in emissions of sulfur dioxide (SO₂), nitrogen oxides (NOx), volatile organic compounds, particulate matter, carbon dioxide (CO₂), and other GHGs. It is estimated that globally, shipping contributes about 14 percent of the world’s total SO₂ and NOx emissions, resulting in 60,000 annual cardiopulmonary and lung cancer deaths worldwide, partially as a result of using low-grade marine fuels that contain up to 3,500 times more sulfur than road diesel. Passenger and cruise ships must also produce power when in ports (when shore power is unavailable), which results in increases in air pollution adjacent to the port.

The global shipping industry emits significant amounts of greenhouse gases. The IMO estimated that in 2014 shipping was responsible for one billion tons of CO₂ emissions, or about 3.1 percent of global emissions. If the global shipping industry were a country, it would be the sixth largest emitter of CO₂ after the United States, China, Russia, India, and Japan. Without additional regulations on CO₂ emissions or the adoption of more efficient shipping technologies, shipping emissions are forecasted to increase by a factor of two to three by 2050. On the other hand, if technical and operational improvements are implemented, they could reduce CO₂ emissions by 25 percent to 75 percent below current levels.

The IMO and other organizations have been active in reducing ship emissions. The IMO has set a GHG emissions reduction target of 15 percent by 2018. Furthermore, parts of Europe and western North America are emission control areas where low-sulfur fuels must be used when steaming in territorial waters.

The IMO has introduced new measures, which entered into force on January 1, 2013, that apply to the entire global international shipping industry and are the first example of global industry-wide CO₂ reduction measures. The Energy Efficiency Design Index for new ships mandates energy efficiency targets of 10 percent improvement for ships built between 2015 and 2019, 15 percent or 20 percent for 2020 to 2024 (depending on the type of ship), and 30 percent for ships delivered after 2024. The Ship Energy Efficiency Management Plan, required for all new and existing ships, establishes best practices for fuel efficiency and voluntary guidelines for measuring CO₂ emissions.

There are a number of ways to reduce ship emissions through either the design or operation of a vessel. Broadly, ships may improve energy efficiency (productivity); use renewable energy sources (e.g., wind, solar, biofuels); use low-carbon fuels (e.g., natural gas); and reduce emissions through chemical conversion, capture, and storage. Additional operational strategies include improving ship routing (including weather routing) and reducing vessel speeds (“slow steaming”). Roughly 67 percent of the costs of operating a commercial vessel are energy-related; therefore, there is an incentive for shippers to improve efficiency.

Between 2007 and 2012, the shift to “slow steaming” resulted in improved fuel economy for the global shipping fleet and reduced emissions. In an ironic turn of events, as the Arctic Ocean warms and sea ice retreats northward, commercial shipping may begin to use the Northwest Passage (Canada) and the Northern Sea Route (Russia) as alternatives to the Panama and Suez Canals. The Northern Sea Route is 43 percent shorter from Rotterdam (Europe) to Yokohama (Asia); thus, fuel consumption is expected to be reduced by up to 37 percent on this route.

Ship Pollution and Oil Spills. Ships may cause intentional (dumping) or unintentional (accidents and spills) impacts to the environment. Types of pollution from ships include oil, chemicals, harmful substances in packaged form, sewage, garbage, and ballast water. These substances may be released either through accident or operation of the ship.

On March 24, 1989, the Exxon Valdez tanker ran aground in the Prince William Sound, spilling eleven million gallons of crude oil into the Gulf of Alaska. The largest oil spill in US history and a major environmental disaster, the resulting slick covered more than 1,000 miles of the Alaska coastline. This photo shows a smaller ship attempting to offload the remaining oil from the Exxon Valdez (Exxon Valdez Oil Spill Trustee Council)

Approximately half of the world’s oil production (approximately 1.6 billion tons) is transported by sea. Much of this transport is over long distances in VLCC and ULCC class tankers (Table 8.1) that pass through straits and transit along coastlines. This means of transport has resulted in many serious accidents and spills over the past several decades (Table 8.2). In addition, a significant amount of oil is transported short distances by seabed pipelines from production wells to offshore or onshore facilities. Although the average number of major oil spills per year has dropped from twenty-five in the 1970s to three today, spills continue to affect fisheries, tourism, and coastal economic activities.

TABLE 8.2. Largest Marine Oil Spills from Ships, Pipelines, and Oil Production Platforms

Although ship owners, ship registries (flag states), classification societies, port states, and cargo owners all have responsibilities to avoid oil spills into the marine environment, the IMO is the primary international agency responsible for establishing the regulatory framework related to the prevention, cleanup, and compensation for oil spills from ships. MARPOL 73/78 is the primary international instrument used to prevent the introduction of pollution into the marine environment from shipping; however, the mandated standards for the construction, equipment, and operation of vessels under SOLAS may reduce the risk of oil pollution. The IMO also administers a number of oil pollution- specific conventions.

Ship Recycling. Ship recycling, also termed “ship breaking,” is the process of disassembling and disposing of ships at the end of their life. It is estimated that approximately 1,000 ships per year are recycled, and more than 40,000 ships over the next thirty years will need to be recycled. Currently, 98 percent of the world’s recycled ships (by tonnage) are recycled in Bangladesh, China, India, Pakistan, and Turkey. Around the globe, the industry provides considerable local employment and economic benefits. Nearly every part of a recycled ship can be reused. On the downside, recycling practices are often hazardous to both workers and the environment because ships—and particularly older ships—often contain hazardous materials, including asbestos, polychlorinated biphenyls, ozone-depleting substances, antifouling compounds, heavy metals, and radioactive substances.

The Convention on the Safe and Environmentally Sound Recycling of Ships (the “Hong Kong” Convention) was adopted in 2009 to ensure that the disposal and recycling of ships are executed in a way that protects human health and the environment. In addition, the convention includes provisions that apply to the construction and operation of ships in order to improve public and environmental health throughout a ship’s life cycle. The convention builds upon existing conventions related to hazardous substances, worker safety, and past work of the IMO on ship recycling.