Getty Images photo of a U.S. port

Port & Marine

Diesel engines power the trucks, trains, marine workboats, inland towboats and barges -- the tools of global commerce on the water and on land, serving the nation’s ports.

Diesel Powers America's Ports

Our global economy depends on the efficient and continuous movement of goods; supplies of raw materials and delivery of manufactured goods to market. Moving this trade through sea and river ports requires many trucks, trains, ships, cargo handling equipment, barges, and marine workboats. Diesel fuel and engines are the predominant technology used to power these vehicles and equipment due to their fuel efficiency, power, performance, durability and reliability. 

From 2016-2021, 12.5 billion tons worth of goods were sent abroad across the globe in maritime trade. Three hundred and sixty commercial sea and river ports in the US move 2 billion tons of import and export cargo each year while more than 16.9 million cruise passengers also move through a port facility. Over 95% of the cargo entering the United States arrives by ship and over 360 commercial ports nationwide help to transfer these goods to their destinations in communities across the nation. 

According to the U.S. Environmental Protection Agency 39 of the 360 commercial ports in the US are located in areas of non-attainment for one or more criteria pollutants.

Helping reduce port related emissions and achieve sustainability goals, advanced diesel technologies are increasingly deployed across the large spectrum of vehicles, vessels and equipment and are playing a daily role in improving air quality in regions surrounding America’s ports. 

Sources of Port Emissions

Emissions sources at ports vary and typically include a mix of stationary emissions and mobile sources. Stationary sources could include industrial activities located on port property because of proximity to port operations, such as chemical industries, petroleum refining and general manufacturing. 

While every port is different in terms of the mix of cargo handled, most ports have a variety of diesel-powered equipment to move freight and provide key services to the port. These include heavy-duty trucks and other vehicles, ocean going vessels, barges, trains, tugboats, material handling equipment and other yard equipment used to move freight. About 10% of the nation’s ports are located in areas classified as non-attainment for one or more pollutants including particulate matter, or soot, and ozone, or smog involving oxides of nitrogen.

Though no two ports are exactly alike, generally speaking the largest emissions contribution comes from the ocean-going vessels (OGV) such as container ships, oil and gas tankers, dry bulk carriers, and “roll-on roll-off” vessels that carry automobiles, project cargoes. Harbor work vessels including tugs, push boats, ferries, and fireboats and truck, rail, and material handling equipment are lesser sources.   

Port_PM_Emissions Port_Nox_Emissions

Source: National Port Strategy Assessment: Reducing Air Pollution and Greenhouse Gases at U.S. Ports | US EPA


Reducing Emissions

Strategies to reduce emissions from mobile sources in ports generally target three areas: reducing emissions from the trucks, trains, tugboats, and cargo handling equipment servicing the port; controlling emissions from the ocean-going vessels serving the ports; and improving operational efficiencies at the port.

Significant emission reduction benefits can be realized by the replacement of the oldest diesel engines and equipment with the newest generation of diesel power equipped with the latest near-zero emissions technologies. This new technology is available for commercial trucks, material handling equipment, as well as in the largest engines used in workboats and locomotives.

For heavy duty trucks serving the ports, new emissions requirements effective in 2007 resulted in reduced particulate matter emissions by 98% from new vehicles. In addition to particulate emissions reductions, since 2010, emissions of nitrogen oxides have also been reduced by 98% compared to pre-2000 models.  The result is that since 2010, all new diesel engines in commercial trucks have been achieving near zero emissions.  According to our latest information from IHSMarkit, 53% of commercial trucks in operation in the US are now 2011 and newer models.    

Similar progress has been made in reducing emissions from off-road engines and equipment. Since 2014, new engines and equipment for material and cargo handling and vessels used in port operations achieve similar emissions reductions as commercial trucks. The off-road engines “Tier 4” technology reduces emissions of nitrogen oxides and particulate matter by more than 80%, depending on engine horsepower ratings.

Funding for Upgrading to Advanced Diesel Technology Vehicles and Equipment

Federal and local funds are available to help owners of older vehicles and equipment upgrade and/or purchase new vehicles and equipment used in port operations. These funding sources include the Diesel Emission Reduction Act (DERA) program, managed by U.S. Environmental Protection Agency, and the Congestion Mitigation and Air Quality Program, managed by the U.S. Department of Transportation. In addition, many seaports operate independent programs using local funds to help incentivize equipment and engine upgrades. 

For example, funding made available through the federal DERA program between 2008 and 2015 provided roughly $158 million in matching funds for port related diesel emission reduction activities. Almost a quarter of port related funding, or $38 million, was made available for the purchase of new trucks or retrofit kits to significantly reduce emissions form port trucks. For example, the Port Authority of New York-New Jersey received $7 million in DERA assistance coupled with an additional $21 million in non-federal matching funds to help replace 636 older drayage trucks; trucks that move containers from the ships to receivers. Drayage trucks are typically second, third, or fourth generation used equipment owned by independent owner/operators that almost exclusively serve the port. Many states and some port authorities have assistance programs for equipment upgrade, such as no or low-interest loans other efforts, to provide equipment owners with resources to purchase more modern equipment.


Source: DERA Fourth Report to Congress: Highlights of the Diesel Emissions Reduction Program (EPA-420-R-19-005, July 2019)

Recent research confirms that repowering older engines in these applications is one of the most cost-effective ways to reduce emissions in port communities, particularly those located in air quality non-attainment areas.

Clean Diesel Success Story – The Ports of Long Beach and Los Angeles
Air quality in ports is rapidly improving thanks to the introduction of new clean diesel engines deployed in the many applications in ports, along with retrofit activities to install emission control technologies on older diesel engines. Nowhere is this more evident than in Southern California. The Port of Los Angeles estimates that between 2005 and 2015, fine particle emissions (PM) fell by 85%, or 745 tons per year, while NOx fell by 51% or 8,325 tons per year. Other ports have also reported similarly impressive emission reductions. The overwhelming majority of these clean air achievements are attributable to the introduction of clean diesel technology in ports.

Clean Diesel Technologies Deployed in Ports

Port Trucks

1 in 3 Trucks on the road are Powered with the latest Clean Diesel Technology



Railroads also play a key role moving cargo through ports. The most visible types of railroad equipment used in ports are line-haul locomotives deployed with large diesel engines typically between 3,000 and 4,000 horsepower. Smaller switcher locomotives typically 1,000-2,000hp are used to position and combine rail cars in the staging yard to make a complete train. Since 2010, EPA regulations require the use of cleaner low sulfur diesel fuel, and new engines manufactured for line-haul and switch locomotives now meet the near-zero emissions “Tier 4” standards for particulate matter and oxides of nitrogen.


In addition to new engine emissions standards, many seaports have adopted strategies to encourage more efficient operation and use of railroad equipment, such as idle reduction strategies, and the use of renewable biodiesel fuels.

Locomotives Are Getting Cleaner Too

The most cost-effective upgrades make the biggest health impact

Diesel is the technology of choice for large applications like locomotives and marine workboats because of its combination of power, performance, and durability. According to the U.S. EPA, these engines have an estimated useful life of about 70 years. Replacing the oldest engines with new advanced diesel technologies can yield immediate and substantial emission reductions often with improved fuel efficiency and lower greenhouse gas emissions.

One rail operator in the Port of Tacoma, WA received DERA funding to help replace older engines that power a single switch locomotives with a single clean diesel model. In doing so, the rail operator immediately reduced 68,000 lbs. of NOx that is roughly equivalent to the emissions reduced by taking almost 22,000 cars off the road for a year. Replacing a series of older engines with a single new clean diesel model also saved the operator 19,000 gallons of fuel each year.    



Ports use a wide variety of specialized equipment to load, unload, shuttle, stack, and sort various kinds of cargo. While much of this equipment is mobile, some is stationary, including gantry cranes that tower over container vessels and are responsible for loading and unloading containers. Cargo handling equipment typically accounts for 5 to 7% of the NOx and PM emissions, though each port is different. In recent years, considerable efforts have been made to shift the majority of material handling equipment from diesel to electrification.


A variety of regulations cover the emissions from diesel engines used in this equipment. EPA rules covering on-road engines include some trucks that are found performing cargo handling functions. Those rules, mentioned earlier, significantly reduce emissions to near zero levels beginning with model year 2010 engines. Other diesel-powered equipment, such as cranes and yard hostlers, is covered under the “Tier 4” off-road emissions rules that require significant near zero emissions of PM and NOx that started with model year 2014. 

Clean Diesel Powers Cargo Handling Equipment

Federal, state, and local port authority funds are also available to modernize and upgrade older cargo handling equipment with technologies to significantly reduce emissions. Of the roughly $158 million awarded in federal diesel emissions grant funding between 2008 and 2015 for port activities, about $25 million, or 16%, helped retrofit cargo handling equipment. As an example, the Puget Sound Clean Air Agency that encompasses the ports of Tacoma and Seattle, WA, received $850,000 in DERA assistance to retrofit 74 pieces of cargo handling equipment with diesel particulate filters and closed crankcase ventilation devices.

Emissions from cargo handling equipment in many ports has fallen as a result of the introduction of advanced diesel technology engines and equipment, retrofit activities to improve the emissions from older equipment, as well as electrifying some stationary engines. The Port of Los Angeles estimates that cargo handling emissions of PM have fallen by about 87% and emissions of NOx fell by almost 65% between 2005 and 2015. The Ports of Seattle, Vancouver, and Tacoma estimate that emissions of NOx from cargo handling equipment fell by almost 57% and emissions of PM fell by 65% between 2005 and 2016.


Seaports and river ports are home to many marine vessels as well as harbor craft that help larger vessels and cruise ships navigate narrow ship channels. Many large seaports are also home to active ferry terminals helping to transport commuters. Inland waterways and Great Lakes ports host a large population of barges and the workboats that propel these crafts. These ferries and workboats are almost exclusively powered by diesel engines. Many of these vessels will have one or more diesel engines for prime power and may also have another set of engines to provide auxiliary electrical power.

Hybrid-diesel electric and all electric passenger ferries have been introduced in the Bay Area of California and several other locations.

EPA regulations in place governing new off-road diesel engines, such as those found in cargo handling equipment and locomotives, also apply to harbor craft. Those rules require that new engines manufactured beginning in 2015 that power tugboats, towboats, Great Lake freighters and stationary or auxiliary engines, must meet “Tier 4” near zero emissions standards. According to the EPA, these Tier 4 rules will reduce PM by 90% and NOx by 80%.

Research commissioned by the Diesel Technology Forum and the Environmental Defense Fund found that, on average, replacing older engines that power marine workboats with new clean diesel models can reduce NOx emissions by 30 tons per year. That’s the equivalent of taking more than 26,000 cars off the road for a year. 

Replacing older marine engines is one of the most cost-effective investments as clean air agencies and ports consider the use of incentive funds provided by a variety of federal programs and the Volkswagen Environmental Mitigation Trust funds. A single workboat engine replacement project, while expensive, delivers many more emission reductions than other projects thereby maximizing return on clean air investments for near-port communities.Workboats Adopt Clean Diesel Technology

Tier 4 engines for tug boats reduce NOx emissions by 91%

Case Study: Replacing Propulsion and Auxiliary Engines on the Island Eagle

In 2015, the Puget Sound Clean Air Agency using additional funds from the U.S. Maritime Administration, to replace the two propulsion engines with Tier 3 models and its auxiliary engine with a Tier 4 model on the Island Eagle, a tugboat in operation in the Port of Tacoma. In doing so, the project delivered 3.2 tons of NOx emission reductions immediately to near-port communities while saving the operator 45,000 gallons of fuel each year resulting in over 1,000 tons of greenhouse gas emissions.

Ocean Going Vessels

Ocean going vessels (OGV) such as container ships are regulated by a United Nation’s treaty under the International Maritime Organization (IMO). The IMO rules establish operational, engine technology and fuel requirements.  While transiting international waters, OGVs typically use bunker fuel – a heavy petroleum product with high energy content.

The IMO rules also require that new engines installed on vessels since 2011 must meet USEPA Tier 2 emissions standards and beginning in 2016 new engines must meet cleaner Tier 3 rules. They also require the use of diesel fuel with lower sulfur content. Since January 1, 2020, the sulfur content of fuel used in ocean going vessel must not exceed .5% - a reduction from 3.5% allowed as of January 2, 2012. The IMO rules also allowed the US to establish emissions control areas (ECA) along the East, West, and Gulf Coasts, as well as in the Caribbean. During operations in the ECA (typically 200 miles from shore) vessels must switch their fuel to a cleaner-burning low sulfur diesel type fuel. 

Other initiatives are in place to reduce OGV emissions while docked, such as providing incentives or requiring the vessel to plug in and use shore-side electrical grid power for hoteling operations on instead of a practice known as cold ironing; a reference to a shipping industry term when all ships had coal fired engines. When a ship tied up at port there was no need to continue to stoke the fire and the iron engines would literally cool down, eventually going completely cold, hence the term cold ironing. The state of California also requires cargo and cruise vessels to shut down a proportion of auxiliary diesel engines while at berth and use cold-iron capabilities. Many ports also offer incentives to vessel operators to reduce speed when approaching marine terminals to help reduce emissions.