Environmental impact of shipping

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A cargo ship discharging ballast water into the sea.

The environmental impact of shipping includes greenhouse gas emissions, acoustic, and oil pollution. The International Maritime Organization (IMO) estimates that Carbon dioxide emissions from shipping were equal to 2.2% of the global human-made emissions in 2012[1] and expects them to rise by as much as 2 to 3 times by 2050 if no action is taken.[2]

The First Intersessional Meeting of the IMO Working Group on Greenhouse Gas Emissions[3] from Ships took place in Oslo, Norway on 23–27 June 2008. It was tasked with developing the technical basis for the reduction mechanisms that may form part of a future IMO regime to control greenhouse gas emissions from international shipping, and a draft of the actual reduction mechanisms themselves, for further consideration by IMO’s Marine Environment Protection Committee (MEPC).[4]

Ballast water[edit]

Ballast water discharges by ships can have a negative impact on the marine environment.

Cruise ships, large tankers, and bulk cargo carriers use a huge amount of ballast water, which is often taken on in the coastal waters in one region after ships discharge wastewater or unload cargo, and discharged at the next port of call, wherever more cargo is loaded. Ballast water discharge typically contains a variety of biological materials, including plants, animals, viruses, and bacteria. These materials often include non-native, nuisance, invasive, exotic species that can cause extensive ecological and economic damage to aquatic ecosystems along with serious human health problems.

Sound pollution[edit]

Noise pollution caused by shipping and other human enterprises has increased in recent history.[5] The noise produced by ships can travel long distances, and marine species who may rely on sound for their orientation, communication, and feeding, can be harmed by this sound pollution[6][7]

The Convention on the Conservation of Migratory Species has identified ocean noise as a potential threat to marine life.[8] The disruption of whales' ability to communicate with one another is an extreme threat and is affecting their ability to survive. According to Discovery Channel's article on Sonic Sea Journeys Deep Into the Ocean,[9] over the last century, extremely loud noise from commercial ships, oil and gas exploration, naval sonar exercises and other sources has transformed the ocean’s delicate acoustic habitat, challenging the ability of whales and other marine life to prosper and ultimately to survive. Whales are starting to react to this in ways that are life threatening. Kenneth C. Balcomb, a whale researcher and a former U.S Navy officer,[10] states that the day March 15, 2000, is the day of infamy. As Discovery says,[11] where him and his crew discovered whales swimming dangerously close to the shore. They’re supposed to be in deep water. So I pushed it back out to sea, says Balcomb.[12] Although sonar helps to protect us, it is destroying marine life. According to IFAW Animal Rescue Program Director Katie Moore,[13] There’s different ways that sounds can affect animals. There’s that underlying ambient noise level that’s rising, and rising, and rising that interferes with communication and their movement patterns. And then there’s the more acute kind of traumatic impact of sound, that’s causing physical damage or a really strong behavioral response. It’s fight or flight.

Wildlife collisions[edit]

Marine mammals, such as whales and manatees, risk being struck by ships, causing injury and death. For example, if a ship is traveling at a speed of only 15 knots, there is a 79 percent chance of a collision being lethal to a whale.[14]

One notable example of the impact of ship collisions is the endangered North Atlantic right whale, of which 400 or less remain. The greatest danger to the North Atlantic right whale is injury sustained from ship strikes.[14] Between 1970 and 1999, 35.5 percent of recorded deaths were attributed to collisions.[15] During 1999 to 2003, incidents of mortality and serious injury attributed to ship strikes averaged one per year. In 2004 to 2006, that number increased to 2.6.[16] Deaths from collisions has become an extinction threat.[17]

Atmospheric pollution[edit]

Exhaust gases from ships are considered to be a significant source of air pollution, both for conventional pollutants and greenhouse gases.

There is a perception that cargo transport by ship is low in air pollutants, because for equal weight and distance it is the most efficient transport method, according to shipping researcher Amy Bows-Larkin.[18] This is particularly true in comparison to air freight; however, because sea shipment accounts for far more annual tonnage and the distances are often large, shipping's emissions are globally substantial.[18] A difficulty is that the year-on-year increasing amount shipping overwhelms gains in efficiency, such as from slow-steaming or the use of kites. The growth in tonne-kilometers of sea shipment has averaged 4 percent yearly since the 1990s.[19] And it has grown by a factor of 5 since the 1970s.[18] There are now over 100,000 transport ships at sea, of which about 6,000 are large container ships.[18]

Conventional pollutants[edit]

Air pollution from cruise ships is generated by diesel engines that burn high sulfur content fuel oil, also known as bunker oil, producing sulfur dioxide, nitrogen oxide and particulate, in addition to carbon monoxide, carbon dioxide, and hydrocarbons. Diesel exhaust has been classified by EPA as a likely human carcinogen. EPA recognizes that these emissions from marine diesel engines contribute to ozone and carbon monoxide non-attainment (i.e., failure to meet air quality standards), as well as adverse health effects associated with ambient concentrations of particulate matter and visibility, haze, acid deposition, and eutrophication and nitrification of water.[20] EPA estimates that large marine diesel engines accounted for about 1.6 percent of mobile source nitrogen oxide emissions and 2.8 percent of mobile source particulate emissions in the United States in 2000. Contributions of marine diesel engines can be higher on a port-specific basis. Ultra-low sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents. As of 2006, almost all of the petroleum-based diesel fuel available in Europe and North America is of a ULSD type.

Of total global air emissions, shipping accounts for 18 to 30 percent of the nitrogen oxide and 9 percent of the sulphur oxides.[21] [22] Sulfur in the air creates acid rain which damages crops and buildings. When inhaled, sulfur is known to cause respiratory problems and even increases the risk of a heart attack.[23] According to Irene Blooming, a spokeswoman for the European environmental coalition Seas at Risk, the fuel used in oil tankers and container ships is high in sulfur and cheaper to buy compared to the fuel used for domestic land use. "A ship lets out around 50 times more sulfur than a lorry per metric tonne of cargo carried."[23] Cities in the U.S. like Long Beach, Los Angeles, Houston, Galveston, and Pittsburgh see some of the heaviest shipping traffic in the nation and have left local officials desperately trying to clean up the air.[24] Increasing trade between the U.S. and China is helping to increase the number of vessels navigating the Pacific and exacerbating many of the environmental problems. To maintain the level of growth China is experiencing, large amounts of grain are being shipped to China by the boat load. The number of voyages are expected to continue increasing.[25]

Greenhouse gas pollutants[edit]

3.5 to 4 percent of all climate change emissions are caused by shipping, primarily carbon dioxide.[22]

As one way to reduce the impact of greenhouse gas emissions from shipping, vetting agency RightShip developed an online "Greenhouse Gas (GHG) Emissions Rating" as a systematic way for the industry to compare a ship’s CO2 emissions with peer vessels of a similar size and type. Based on the International Maritime Organisation's (IMO) Energy Efficiency Design Index (EEDI) that applies to ships built from 2013, RightShip's GHG Rating can also be applied to vessels built prior to 2013, allowing for effective vessel comparison across the world's fleet. The GHG Rating utilises an A to G scale, where A represents the most efficient ships. It measures the theoretical amount of carbon dioxide emitted per tonne nautical mile travelled, based on the design characteristics of the ship at time of build such as cargo carrying capacity, engine power and fuel consumption. Higher rated ships can deliver significantly lower CO2 emissions across the voyage length, which means they also use less fuel and are cheaper to run.

Cruise ship haze over Juneau, Alaska

Stress for improvement[edit]

One source of environmental stresses on maritime vessels recently has come from states and localities, as they assess the contribution of commercial marine vessels to regional air quality problems when ships are docked at port.[26] For instance, large marine diesel engines are believed to contribute 7 percent of mobile source nitrogen oxide emissions in Baton Rouge/New Orleans. Ships can also have a significant impact in areas without large commercial ports: they contribute about 37 percent of total area nitrogen oxide emissions in the Santa Barbara area, and that percentage is expected to increase to 61 percent by 2015.[20] Again, there is little cruise-industry specific data on this issue. They comprise only a small fraction of the world shipping fleet, but cruise ship emissions may exert significant impacts on a local scale in specific coastal areas that are visited repeatedly. Shipboard incinerators also burn large volumes of garbage, plastics, and other waste, producing ash that must be disposed of. Incinerators may release toxic emissions as well.

In 2005, MARPOL Annex VI came into force to combat this problem. As such cruise ships now employ CCTV monitoring on the smokestacks as well as recorded measuring via opacity meter while some are also using clean burning gas turbines for electrical loads and propulsion in sensitive areas.

Oil spills[edit]

Most commonly associated with ship pollution are oil spills. While less frequent than the pollution that occurs from daily operations, oil spills have devastating effects. While being toxic to marine life, polycyclic aromatic hydrocarbons (PAHs), the components in crude oil, are very difficult to clean up, and last for years in the sediment and marine environment.[27] Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles. One of the more widely known spills was the Exxon Valdez incident in Alaska. The ship ran aground and dumped a massive amount of oil into the ocean in March 1989. Despite efforts of scientists, managers and volunteers, over 400,000 seabirds, about 1,000 sea otters, and immense numbers of fish were killed.[27]

International regulation[edit]

Some of the major international efforts in the form of treaties are the Marine Pollution Treaty, Honolulu, which deals with regulating marine pollution from ships, and the UN Convention on Law of the Sea, which deals with marine species and pollution.[28] While plenty of local and international regulations have been introduced throughout maritime history, much of the current regulations are considered inadequate. "In general, the treaties tend to emphasize the technical features of safety and pollution control measures without going to the root causes of sub-standard shipping, the absence of incentives for compliance and the lack of enforceability of measures."[29] The most common problems encountered with international shipping arise from paperwork errors and customs brokers not having the proper information about your items.[30] Cruise ships, for example, are exempt from regulation under the US discharge permit system (NPDES, under the Clean Water Act) that requires compliance with technology-based standards.[27] In the Caribbean, many ports lack proper waste disposal facilities, and many ships dump their waste at sea.[31]


Carcass of a whale on a shore in Iceland.

The cruise line industry dumps 255,000 US gallons (970 m3) of greywater and 30,000 US gallons (110 m3) of blackwater into the sea every day. Blackwater is sewage, wastewater from toilets and medical facilities, which can contain harmful bacteria, pathogens, viruses, intestinal parasites, and harmful nutrients. Discharges of untreated or inadequately treated sewage can cause bacterial and viral contamination of fisheries and shellfish beds, producing risks to public health. Nutrients in sewage, such as nitrogen and phosphorus, promote excessive algal blooms, which consumes oxygen in the water and can lead to fish kills and destruction of other aquatic life. A large cruise ship (3,000 passengers and crew) generates an estimated 55,000 to 110,000 liters per day of blackwater waste.[32]

Due to the environmental impact of shipping, and sewage in particular marpol annex IV was brought into force September 2003 strictly limiting untreated waste discharge. Modern cruise ships are most commonly installed with a membrane bioreactor type treatment plant for all blackwater and greywater, such as (http://www.gertsen-olufsen.com/Ship-Offshore/Products/G-O_Brands/G-O_Bioreactor.aspx) , Zenon or Rochem which produce near drinkable quality effluent to be re-used in the machinery spaces as technical water.


Greywater is wastewater from the sinks, showers, galleys, laundry, and cleaning activities aboard a ship. It can contain a variety of pollutant substances, including fecal coliforms, detergents, oil and grease, metals, organic compounds, petroleum hydrocarbons, nutrients, food waste, medical and dental waste. Sampling done by the EPA and the state of Alaska found that untreated greywater from cruise ships can contain pollutants at variable strengths and that it can contain levels of fecal coliform bacteria several times greater than is typically found in untreated domestic wastewater.[33] Greywater has potential to cause adverse environmental effects because of concentrations of nutrients and other oxygen-demanding materials, in particular. Greywater is typically the largest source of liquid waste generated by cruise ships (90 to 95 percent of the total). Estimates of greywater range from 110 to 320 liters per day per person, or 330,000 to 960,000 liters per day for a 3,000-person cruise ship.[34]

Solid waste[edit]

Solid waste generated on a ship includes glass, paper, cardboard, aluminium and steel cans, and plastics. It can be either non-hazardous or hazardous in nature. Solid waste that enters the ocean may become marine debris, and can then pose a threat to marine organisms, humans, coastal communities, and industries that utilize marine waters. Cruise ships typically manage solid waste by a combination of source reduction, waste minimization, and recycling. However, as much as 75 percent of solid waste is incinerated on board, and the ash typically is discharged at sea, although some is landed ashore for disposal or recycling. Marine mammals, fish, sea turtles, and birds can be injured or killed from entanglement with plastics and other solid waste that may be released or disposed off of cruise ships. On average, each cruise ship passenger generates at least two pounds of non-hazardous solid waste per day.[35] With large cruise ships carrying several thousand passengers, the amount of waste generated in a day can be massive. For a large cruise ship, about 8 tons of solid waste are generated during a one-week cruise.[36] It has been estimated that 24 percent of the solid waste generated by vessels worldwide (by weight) comes from cruise ships.[37] Most cruise ship garbage is treated on board (incinerated, pulped, or ground up) for discharge overboard. When garbage must be off-loaded (for example, because glass and aluminium cannot be incinerated), cruise ships can put a strain on port reception facilities, which are rarely adequate to the task of serving a large passenger vessel.[38]

Bilge water[edit]

On a ship, oil often leaks from engine and machinery spaces or from engine maintenance activities and mixes with water in the bilge, the lowest part of the hull of the ship, but there is a filter to clean bilge water before being discharged. Oil, gasoline, and by-products from the biological breakdown of petroleum products can harm fish and wildlife and pose threats to human health if ingested. Oil in even minute concentrations can kill fish or have various sub-lethal chronic effects. Bilge water also may contain solid wastes and pollutants containing high levels of oxygen-demanding material, oil and other chemicals. A typically large cruise ship will generate an average of 8 metric tons of oily bilge water for each 24 hours of operation.[39] To maintain ship stability and eliminate potentially hazardous conditions from oil vapors in these areas, the bilge spaces need to be flushed and periodically pumped dry. However, before a bilge can be cleared out and the water discharged, the oil that has been accumulated needs to be extracted from the bilge water, after which the extracted oil can be reused, incinerated, and/or offloaded in port. If a separator, which is normally used to extract the oil, is faulty or is deliberately bypassed, untreated oily bilge water could be discharged directly into the ocean, where it can damage marine life. A number of cruise lines have been charged with environmental violations related to this issue in recent years.[40][41]

Issues by region[edit]


United Kingdom[edit]

United States[edit]

It is expected that, (from 2004) "...shipping traffic to and from the USA is projected to double by 2020."[24]

International regulation[edit]

See also[edit]


  1. ^ Third IMO GHG Study 2014 (PDF), International Maritime Organization 
  2. ^ Second IMO GHG Study 2009, International Maritime Organization 
  3. ^ International Maritime Organization, London (2008). "Working Group Oslo June 2008."
  4. ^ SustainableShipping.com (2008). "IMO targets greenhouse gas emissions." (London: Petromedia Group). 2008-06-17.
  5. ^ "Noise could sound the death knell of ocean fish". The Hindu (London). 15 August 2010. Retrieved 2011-03-06. 
  6. ^ Human Noise Pollution in Ocean Can Lead Fish Away from Good Habitats and Off to Their Death, University of Bristol, 13 August 2010, retrieved 2011-03-06 
  7. ^ Simpson, Stephen D.; Mark G. Meekan; Nicholas J. Larsen; Robert D. McCauley; Andrew Jeffs (2010). "Behavioral plasticity in larval reef fish: orientation is influenced by recent acoustic experiences". Behavioral Ecology 21 (5). doi:10.1093/beheco/arq117. 
  8. ^ Noise Pollution and Ship-Strikes (PDF), UN Environment Programme-Convention on Migratory Species, retrieved 2011-03-06 
  9. ^ Discovery Channel's article on Sonic Sea Journeys Deep Into the Ocean
  10. ^ Kenneth C. Balcomb, a whale researcher and a former U.S Navy officer
  11. ^ Discovery says
  12. ^ says Balcomb
  13. ^ IFAW Animal Rescue Program Director Katie Moore
  14. ^ a b Vanderlaan & Taggart (2007). "Vessel collisions with whales: the probability of lethal injury based on vessel speed" (PDF). Mar Mam. Sci. Retrieved 2008-05-10. 
  15. ^ Ward-Geiger, L.I.; Silber, G.K.; Baumstark, R.D.; Pulfer, T.L. (3 March 2005). "Characterization of Ship Traffic in Right Whale Critical Habitat" (PDF). Taylor & Francis Inc. doi:10.1080/08920750590951965. ISSN 0892-0753. Retrieved 22 August 2009. 
  17. ^ "Shipping threat to endangered whale". BBC News Online (BBC). 28 August 2001. 
  18. ^ a b c d Shipping contributes up to 3 percent of worldwide CO2 emissions, says study, Voice of Russia UK. 27 June 2014.
  19. ^ High Seas, High Stakes, Final Report. Tyndall Centre for Climate Change Research, Univ. of Manchester, UK. 2014.
  20. ^ a b US Environmental Protection Agency (EPA), Washington, DC. "Control of Emissions From New Marine Compression-Ignition Engines at or Above 30 Liters Per Cylinder." Final rule. Federal Register, 68 FR 9751, 2003-02-28.
  22. ^ a b Vidal, John (2009-04-09). "Health risks of shipping pollution have been 'underestimated'". The Guardian. Retrieved 2009-07-03. 
  23. ^ a b Harrabin, R. (25 June 2003). "EU faces ship clean-up call." BBC News. Retrieved 1 November 2006, from http://news.bbc.co.uk/2/hi/europe/3019686.stm
  24. ^ a b Watson, T. (30 August 2004). Ship pollution clouds USA's skies. USA Today. Retrieved 1 November 2006, from http://www.usatoday.com/news/nation/2004-08-30-ship-pollution_x.htm
  25. ^ Schmidt, C., & Olicker, J. (20 April 2004). World in the Balance: China Revs Up [Transcript]. PBS: NOVA. Retrieved 26 November 2006, from http://www.pbs.org/wgbh/nova/transcripts/3109_worldbal.html
  27. ^ a b c Panetta, L. E. (Chair) (2003). "America's living oceans: charting a course for sea change." Electronic Version, CD. Pew Oceans Commission.
  28. ^ Steger, M. B. (2003). Globalization: A Very Short Introduction. Oxford University Press Inc. New York.
  29. ^ Khee-Jin Tan, A. (2006). Vessel-source marine pollution: the law and politics of international regulation. Cambridge: Cambridge University Press
  30. ^ http://www.clxlogistics.com/top-4-challenges-you-need-to-master-for-international-shipping/
  31. ^ United Nations Environment Programme in collaboration with GEF, the University of Kalmar, and the Municipality of Kalmar, Sweden, & the Governments of Sweden, Finland and Norway. (2006). Challenges to international waters: regional assessments in a global perspective [Electronic Version]. Nairobi, Kenya: United Nations Environment Programme. Retrieved 5 January 2010, from http://www.unep.org/dewa/giwa/publications/finalreport/
  32. ^ The Ocean Conservancy, "Cruise Control, A Report on How Cruise Ships Affect the Marine Environment," May 2002, p. 13. - PDF [1]
  33. ^ EPA Draft Discharge Assessment Report, pp. 3-5 - 3-6.
  34. ^ Cruise Control, p. 15.
  35. ^ The Center for Environmental Leadership in Business, "A Shifting Tide, Environmental Challenges and Cruise Industry Responses," p. 14.
  36. ^ Bluewater Network, "Cruising for Trouble: Stemming the Tide of Cruise Ship Pollution," March 2000, p. 5. A report prepared for an industry group estimated that a 3,000-person cruise ship generates 1.1 million US gallons (4,200 m3) of graywater during a seven-day cruise. Don K. Kim, "Cruise Ship Waste Dispersion Analysis Report on the Analysis of Graywater Discharge," presented to the International Council of Cruise Lines, 14 September 2000.
  37. ^ National Research Council, Committee on Shipboard Wastes, Clean Ships, Clean Ports, Clean Oceans: Controlling Garbage and Plastic Wastes at Sea (National Academy Press, 1995), Table 2-3, pp. 38-39.
  39. ^ "Shifting Tide," p. 16.
  40. ^ Adams, Marilyn (2002-11-07). "Cruise ship pollution fine draws criticism". USA Today. 
  41. ^ Huettel, Steve (2004-04-14). "Liner may have dumped oily water, reports say". St. Petersburg Times. 

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