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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Box 7-A Environmental Challenges Associated With Marine Transportation

Wednesday, February 22, 2017

According to the Freight Analysis Framework, the water mode moved more than 1 billion tons of goods valued at $831 billion in 2015, accounting for 5.7 percent of the weight and 4.3 percent of the value of all domestic freight shipments [USDOT FHWA and BTS 2016]. Marine transport of this large volume of goods accounted for about 3 percent of transportation sector energy use, which is expected to double by 2040. [USDOE EIA 2015]. The use of petroleum-based fuels in marine transport and port operations produces air pollutants that impact air quality and also result in unintended oil and fuel spills that negatively affect our Nation’s waterways.

Emissions Associated With Marine Transport

U.S. marine vessels contributed approximately 24 million metric tons of CO2 to our atmosphere in 2014, which is less than half of what it was in 2000 [USEPA 2016a]. Commercial marine transportation contributes approximately 44,000 tons of particulate matter (PM-10) emissions annually, accounting for nearly 24 percent of the 185,600 tons attributed to freight-related transportation, second only to heavy-duty trucks. This level of emissions is projected to remain constant through 2020, while both truck and rail emissions are expected to decrease [USDOT FHWA 2011]. In 2010 the International Maritime Organization’s Marine Environment Protection Committee adopted a North American Emission Control Area that created new limits on emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter within 230 miles of U.S. or Canadian coasts [FMC 2016]. These emissions limits are to be attained through new engine standards for vessels, which include advancements in exhaust gas cleaning technology and use of low-sulfur fuel [USEPA 2016b].

The 360 commercial ports in the United States generate emissions in concentrated areas. In addition to emission-generating cranes, drayage trucks, and other dedicated equipment, ports also serve as a multimodal hub, with heavy-duty trucks moving cargo in and out of the ports. Clean diesel fuel (discussed earlier in this chapter) is one means of reducing port-related emissions. Alternate marine power (AMP), sometimes called cold ironing, is another means of reducing emissions while ships are docked for loading or unloading. AMP provides shore-side power for basic ship functions, such as lights and air- conditioning, reducing the need to run the ships’ diesel engines [MARINE INSIGHT 2016].

Climatic Change Considerations for Marine Transport

Climate change has the potential to impact marine transportation. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change, published in 2014, predicts frequent and longer heat waves (which may lead to more drought periods), intensified and frequent precipitation events in some regions, and additional rise of mean sea levels [IPCC 2014]. While these are global, model-based predictions, recent U.S. climate history supports these forecasts.

The 2012 upper mid-west drought affected crop production as well as the transport of crops and other goods to market. Barges had to reduce load sizes to navigate lower water levels in the Mississippi River and other waterways. Energy production also heavily relies on barge transport of coal to power plants across the eastern and middle United States [National Geographic 2013]. Flooding can also affect barge movements on the inland waterway system, necessitating reduced tow sizes as well as restrictions on night- time navigation due to fast-moving currents.

While sea level rise is anticipated, the Atlantic and Gulf coasts are already experiencing some impacts and have seen approximately one inch per decade increases in the 20th century. Efforts are underway at many ports to assess and prepare for climate change by constructing protective infrastructure, developing reinforcement mechanisms, elevating infrastructure, and creating more robust plans for normal and emergency operations.


Federal Maritime Commission (FMC). 2016. IMO Approval of North American Emission Control Area. Available at as of July 2016.

Intergovernmental Panel on Climate Change (IPCC). 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.

Marine Insight. 2016. What is Alternate Marine Power (AMP) or Cold Ironing? Available at as of July 2016.

National Geographic. 2013. How Drought on the Mississippi River Impacts You. February 1, 2013. Available at http://news. as of July 2016.

U.S. Department of Energy (USDOE), Energy Information Administration (EIA). 2015. Annual Energy Outlook 2015. Available at http://www. as of July 2016.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), Office of Freight Management and Operations. 2011. Freight Facts and Figures. Available at as of July 2016.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), Office of Freight Management and Operations. 2016. Freight Analysis Framework version 4. Available at as of July 2016.

U.S. Environmental Protection Agency (USEPA):

—2016a. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014, EPA 430- R-15-004 (Washington, DC: April 15, 2016). Available at as of May 2016.

—2016b. Ocean Vessels and Large Ships. Avail- able at as of July 2016.