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It takes 5 million barrels of fuel per day to move commercial ships across the routes shown on this map. Added up over the course of a year, international shipping emits more than 800 million tons of carbon dioxide or its equivalent in other greenhouse gases—11 percent of the total emissions from the transportation sector.

More than 80 percent of global trade, by volume, floats its way from place to place. 90,000 commercial vessels—tankers, bulk dry carriers, and container ships—make the movement of goods possible, transporting more than 10 billion tons of cargo in 2015.

Shipping produces 3 percent of global greenhouse gas emissions. Forecasts predict they could be 50 percent to 250 percent higher in 2050. Because of huge shipping volumes, increasing shipping efficiency can have a sizable impact.

Efficiency begins with ship design and onboard technology. Fuel-saving innovations include:

  • flat extensions called ducktails at the rear to lower resistance; and
  • compressed air pumped through the bottom of the hull to create a layer of bubbles that “lubricate” passage through the water.

Maintenance and operations also are vital for marine fuel efficiency. Techniques like removing debris from propellers, smoothing the surface of a hull with a sharkskin-like coating, and “slow steaming”—reducing a ship’s operating speed—all lower fuel consumption.


global trade…commercial vessels…[total] cargo: UNCTAD. Review of Maritime Transport 2015. Geneva: United Nations Conference on Trade and Development Secretariat, 2015.

Ships…[vs.] plane[s]: Mathers, Jason. Smart Moves: Creative Supply Chain Strategies Are Cutting Transport Costs and Emissions. New York: Environmental Defense Fund, 2012.

Shipping…emissions: Smith, T. W. P., et al. Third IMO Greenhouse Gas Study 2014. London: International Maritime Organization, 2014.

ducktails…and compressed air: Almeida, Rob. “Part 1: How to Design a More Efficient Ship.” gCaptain. January 4, 2012. (Data from Wärtsilä.)

Energy Efficiency Design Index: ICCT. “The Energy Efficiency Design Index (EEDI) for New Ships.” Policy update from the International Council on Clean Transportation. October 3, 2011.

A-to-G Greenhouse Gas Emissions Rating: Scott, Mike. “Sustainable Shipping Is Making Waves.” The Guardian. August 1, 2014.

port authorities…discount harbor fees: RightShip. Port Incentive Programs: Rewarding Sustainable Shipping. Melbourne, London, and Sugar Land, TX: RightShip, 2016.

sharkskin-like [hull] coating: U.S. Navy. “New Hull Coatings for Navy Ships Cut Fuel Use, Protect Environment.” Washington, D.C.: Office of Naval Research, 2009.

[impact of] “slow steaming”: Wang, Haifeng, and Nic Lutsey. Long-Term Potential for Increased Shipping Efficiency through the Adoption of Industry-Leading Practices. Washington, D.C.: International Council on Clean Transportation, 2013.

industry-leading ships [vs.] laggards: Haifeng and Lutsey, Shipping Efficiency.

[potential to] reduce shipping emissions: Haifeng and Lutsey, Shipping Efficiency.

low-grade bunker fuel [vs.] diesel: Wan, Zheng, Mo Zhu, Shun Chen, and Daniel Sperling. “Pollution: Three Steps to a Green Shipping Industry.” Nature 530 (2016): 275-277.

deaths…[from] particulate matter: Corbett, James J., James J. Winebrake, Erin H. Green, Prasad Kasibhatla, Veronika Eyring, and Axel Lauer. “Mortality from Ship Emissions: A Global Assessment.” Environmental Science and Technology-Columbus 41, no. 24 (2007): 8512.

International Maritime Organization…delay [on emissions]: Harvey, Fiona. “Shipping Industry Criticised for Failure to Reach Carbon Emissions Deal.” The Guardian. October 28, 2016.

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