Information Sources
Emissions and Generation Resource Integrated Database
The United States air pollution data for CO2, NOx, SO2, CH4, N2O and Hg were obtained from the United States EPA emissions and Generation Resource Integrated Database (eGRID2007). The eGRID2007 is a broad inventory of environmental features for all the electricity generating plants that provide power to the electric grid and report data to the United States government.
The eGRID2007 data are collected from a variety of federal sources, including various reports and databases compiled by the United States Environmental Protection Agency (EPA) (e.g., the EPA Emissions Tracking System/Continuous Emissions Monitoring, and the EPA Inventory of US Greenhouse Gas Emissions and Sinks: 1990–2005); reports by the Energy Information Administration (EIA) (e.g., the Annual Electric Generator Report, form EIA-860), as well as monthly reports published by the Federal Energy Regulatory Commission (FERC) (e.g., the Monthly Report of Cost and Quality of Fuels for Electric Plants, FERC-423).
The power plant operational data obtained for this report from the eGRID2007 database include: the annual fossil fuel consumption as heat input, annual electricity generation, plant capacity factor, nameplate generation capacity, and type of fossil fuel burned at the power plant (including the relative proportion of the fuel mixture if more than one type of fuel was burned). Data about the combustion technology (boiler type) and the air pollution control techniques used to reduce emissions were also used, when available.
The 2,834 facilities registered under NAICS code 221112 in the eGRID were considered for this report, but 105 of them reported a zero or negative net electricity generation; thus, a total of 2,728 facilities were included. It should be pointed out that all 2,728 facilities reported emissions of NOx and CO2; however, not all of them reported emissions of the other pollutants examined in this report.
National Emissions Inventory (NEI)
Data on PM2.5 and PM10 for a number of facilities were obtained from the 2005 National Emissions Inventory (NEI, version 2), an inventory created by the EPA’s Emission Inventory and Analysis Group (EIAG) and covering all criteria air pollutants and hazardous air pollutants for every area of the United States. The criteria air pollutant emissions data for the NEI are collected under the Consolidated Emissions Reporting Rule (CERR) (40 CFR Part 51) by each state. The EIAG prepared 2005 emissions data for Electric Generating Units (EGUs) using data obtained from the Department of Energy’s EIA, EPA’s Emission Tracking System/Continuous Emissions Monitoring (ETS/CEM), and the data reported by state air pollution control agencies under the CERR.
The NEI included data on releases of PM10 and PM2.5 for 1,182 of the facilities in the eGRID database; hence, the subsequent analysis is only partial and cannot be considered fully representative of the electricity generation sector in the US. However, it is important to note that these facilities accounted for 75% of the total electricity generation: 85% of that was generated from coal [which is the fuel that generates the largest (uncontrolled) PM emissions]; 51% was generated from oil; and 55% from natural gas.