1.2 What is included in this documentation?

This technical support document (TSD) provides a reference for the complete release of the 2020 NEI in March 2023, superseding the January 2023 release documenting the availability of the Point, Onroad, and Nonroad data categories of the 2020 NEI.

The primary purpose of this document is to explain the sources of information included in the inventory. This includes showing the sources of data and types of sources that are used for each data 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 inventory and some high-level summaries comparisons to the 2017 NEI, as well as a summary on the mercury emissions. Section 3 provides an overview of point sources. Sections 4 and 5 provide information 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 several nonpoint source categories, including but not limited to: 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 NEI includes estimates of greenhouse gases (GHGs), due to availability of these data when modeling CAP/HAP. EPA’s “Inventory of U.S. Greenhouse Gas Emissions and Sinks” provides official data on national greenhouse gas emissions and sinks, including GHGs from the transportation sector. The US greenhouse gas inventory (GHGI) uses internationally accepted methods outlined in Intergovernmental Panel on Climate Change (IPCC) guidance and United Nations Framework Convention on Climate Change (UNFCCC) reporting guidelines to comprehensively estimate and report national GHG emissions from the U.S. transportation sector, including highway and nonroad mobile sources, using fuel consumption data from EIA’s national-level energy statistics. Recently, the EPA has also used peer-reviewed methods to further downscale the national GHGI by state and provide state-level GHG estimates. These are further described in the methodology report underlying those estimates and are available on the “State GHG Emissions and Removals” page to the GHG Emissions Removals home page.