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Modeling and Inventories

Emission Inventory Information & Preparation

An emissions inventory is a summary or forecast of the emissions produced by a group of sources in a given time period. Air pollution emission inventories are the basis for trends analysis, regional and local scale air quality modeling, regulatory impact assessments, and human exposure modeling. Information about the National Emission Inventory (NEI) and other EPA air pollution emission inventories is available here.

Inventories of air pollution from mobile sources are often produced by emissions models, currently the MOVES model for cars, trucks and other highway vehicles and the NONROAD model for most other mobile sources. EPA has specific policies and guidance for modelers producing mobile source air pollution inventories for regulatory purposes such as State Implementation Plans (SIPs) and conformity determinations.

Additional guidance on preparing mobile source inventories is available in the Procedures for Emission Inventory Preparation - Volume IV: Mobile Sources (December 1992) (from National Transportation Library of the US Department of Transportation). The procedures it describes for highway vehicles and nonroad equipment are out-of-date, but the document may still be useful for creating inventories for some aircraft, and for reference on historical procedures for other mobile source categories.

In addition to the links above, this web page provides information on preparing inventories for commercial marine vessels and for ports, and for locomotives.

NOTE: You will need Adobe Acrobat Reader, available as a free download, to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

Estimating Commercial Marine Emission Inventories and Port Emissions

EPA's previous marine inventory guidance document (Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources, EPA420-R-92-009, December 1992) used modeling techniques based on fuel consumption. Since then, we have developed new marine inventory techniques that are more similar to the techniques we use for mobile sources generally, and rely on emission factors, population estimates, and usage characteristics. States and other stakeholders are encouraged to refer to the inventories we prepared for our commercial marine diesel engine standards for use in developing their own inventories. Chapter 3 of the Final Regulatory Impact Analysis (EPA420-R-09-019, December 2009) for EPA's 2010 rule, "Control of Emissions from New Marine Compression-Ignition Engines at or Above 30 Liters per Cylinder", contains our inventory estimates and a description of how those estimates were produced for Category 3 commercial marine vessels. Chapter 3 of the Final Regulatory Impact Analysis (EPA420-R-08-001a, May 2008) for EPA's 2008 rule, "Control of Emissions of Air Pollution from Locomotives and Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder ", contains our inventory estimates and a description of how those estimates were produced for Category 1 and 2 commercial marine vessels.

The page also links to a report describing current practices for calculating emissions from mobile emission sources at ports, including oceangoing vessels, harbor craft, and cargo handling equipment, as well as other land-side mobile emission sources at ports, such as locomotives and on-highway vehicles.

Estimating Emissions from Locomotives:

EPA has prepared a fact sheet that lists emission factors for locomotives and provides instructions for preparing locomotive emission inventories based on these factors and annual fuel consumption rates.

Estimating Emissions from Aircraft:

Emissions from aircraft are usually estimated with a Federal Aviation Administration Model. Additional information on aviation emissions is available at the EPA Aviation website.

Related EPA Information:

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