Regional emissions report shows significant NWSA-related clean air progress

Air pollution related to Northwest Seaport Alliance operations has decreased significantly since 2005, according to a regional report released in March.

The report is the result of the 2016 Puget Sound Maritime Air Emissions Inventory, which provided an update to the 2005 baseline and 2011 inventories.

The inventory estimated greenhouse gases, diesel particulate matter and a number of other pollutants, such as sulfur dioxides and volatile organic compounds. It focused on emissions from ships, harbor vessels, cargo-handling equipment, rail, heavy-duty trucks and other fleet vehicles associated with maritime activities.

In 2015, the ports of Tacoma and Seattle launched the NWSA, a partnership to manage their marine cargo facilities and business. The report compares NWSA’s emissions from activities in 2016 to what would have been included in 2005 in both harbors if the alliance had been in place.

The Northwest Seaport Alliance maritime-related emissions within the airshed 2005-2016

Pollutant Ocean-going vessels Commercial harbor vessels Locomotives Cargo-handling equipment Trucks Overall Normalized per 10,000 tons of cargo
CO -23% 24% -30% -56% -53% -36% -34%
CO2e -27% 4% -23% -38% 9% -20% -17%
DPM -88% -26% -51% -68% -47% -81% -80%
NOx -28% -1% -54% -60% -52% -35% -33%
SO2 -97% -99% -100% -99% -88% -97% -97%
VOC -41% -1% -47% -56% -56% -45% -43%


Much of the clean air progress is due to more stringent fuel and engine standards and voluntary investments in newer, cleaner-burning equipment and vehicles, shore power for ships and efficiencies that reduce truck and train idling.

The Northwest Ports Clean Air Strategy, a ground-breaking initiative of the ports of Tacoma, Seattle and Vancouver, B.C., has helped further reduce emissions in the Puget Sound and Georgia air basins. Mandatory engine and fuel standards have also reduced emissions as older equipment, vehicles and vessels are replaced with newer models and as cleaner fuels are adopted.

The air strategy calls out two main goals by 2020 relative to the 2005 baseline:

  • For diesel particulate matter, achieve an 80 percent reduction per ton of cargo.
  • For greenhouse gases, achieve a 15 percent reduction per ton of cargo.

The seaport alliance has met the 80 percent reduction in diesel particulates and achieved a 17 percent reduction in greenhouse gases, based on the per-ton-of-cargo data in this emissions inventory.

Inventory results will help focus future efforts and investments. The NWSA is updating the Northwest Ports Clean Air Strategy goals based on the inventory results.

About the emissions inventory

The 2016, 2011 and 2005 reports were commissioned by members of the Puget Sound Maritime Air Forum, a voluntary association of private and public maritime organizations, ports, air agencies, environmental and public health advocacy groups and other parties with operational or regulatory responsibilities related to the maritime industry. Forum partners selected Starcrest Consulting Group to develop the reports.

The study area covered the U.S. portion of the Puget Sound/Georgia Basin International Airshed, an area about 140 miles long by 160 miles wide.

Find the full report at

View the Port of Seattle’s live feed of the report release on Facebook.