An emissions inventory estimates the amount of air pollutant or greenhouse gases (GHG) emitted from a source or operation, using globally recognized methods. An emissions source might include the combustion of a liquid fuel used by a vehicle or combustion of fuel used to generate energy used to power buildings. The U.S. Ports in the NWPCAS (Port of Seattle, Port of Tacoma, and Northwest Seaport Alliance) measure emissions from air pollutant and GHG emissions every five years through the Puget Sound Maritime Air Emissions Inventory (PSEI). The PSEI quantifies emissions for air pollutants and GHG emissions based on vessel or equipment details and operational profiles or activity data for each sector.
The Port of Seattle also conducts annual GHG emissions inventories. GHG emissions are not detectable directly from an emissions source, so a GHG emissions inventory estimates the amount of GHGs emitted by multiplying a known activity level of a source - such as power load or gallons of fuel used - by a source-specific emission factor. All Port of Seattle emissions inventories follow the Greenhouse Gas Protocol Corporate Accounting and Reporting Standard.
