1.2 What is included in this documentation?

This technical support document (TSD) provides a reference for the release of the 2023 NEI in September 2026.

The primary purpose of this document is to explain the sources of information included in the NEI. This includes showing the sources of data and types of emissions sources that are included in each source category and then providing more information about the EPA-created components of the data. After the introductory material included in this section, Section 2 provides an overview of the contents of the NEI and some high-level summary comparisons to the 2020 NEI, as well as a summary on the mercury emissions. Section 3 provides documentation on the point sources. Sections 4 and 5 provide documentation for the nonroad mobile and onroad mobile data categories, respectively. Sections 6 and beyond discuss the nonpoint data category, including Fires (wild, prescribed, and agricultural field burning), and EPA methods for computing many nonpoint source categories. Examples of key nonpoint categories with EPA methods include: biogenics, oil and gas production, residential wood combustion, nonpoint industrial and commercial/institutional fuel combustion, solvents utilization, commercial cooking, open burning, agricultural livestock waste and fertilizer application, and fugitive dust sources.

1.2.1 Greenhouse gases reported in the NEI

The 2023 NEI does not include estimates of greenhouse gas (GHG) emissions; however, several components of the 2023 NEI such as landfills and oil and gas processes utilize the “Greenhouse Gas Reporting Program” for activity data from which emissions for CAP and HAP are estimated. GHGs that S/L/Ts included in their 2023 submittals are stored in the Emissions Inventory System (EIS) but are not included as pollutants in the 2023 NEI release.