An air emissions inventory (EI) represents the type and amount of air contaminants released from different sources. DEQ is responsible for developing comprehensive criteria and hazardous pollutant inventories for Idaho. EIs are used for various planning, regulatory, and reporting purposes. Our staff works closely with the regulated community and other state and federal agencies to develop and maintain high-quality and current emissions data.
Annual Point Source Emissions Inventory
Most Tier I, also known as Title V, facilities submit their criteria emissions data annually for fee registration under IDAPA 58.01.01.389 and to meet reporting requirements for EPA’s Air Emissions Reporting Requirements (AERR) in 40 CFR 51.30. DEQ has been gathering point source data online since 2002.
The annual AERR data collection follows EPA’s Emissions Inventory System (EIS) requirements for data format and proper codes. The AERR outlines the exact emissions information state agencies must deliver to EPA annually. These AERR elements include facility information such as physical location, mailing address, and point of contact. Release point and emissions unit process level data and emissions factors are also required.
Periodic Emissions Inventory
Every three years, DEQ must submit a statewide, county-level periodic emissions inventory (PEI) per the AERR. The AERR PEI requires both criteria and hazardous air pollutants (HAPS) for nonpoint, onroad, and nonroad sources. HAPS are voluntary for point sources. DEQ assists the tribes with their nonpoint, onroad, and nonroad PEI. EPA uses the PEI to build the National Emissions Inventory (NEI), a comprehensive estimate of annual air emissions in the United States.
As noted, point sources are collected annually.
Nonpoint sources are estimated as annual emissions and collectively represent sources that are individually too small in magnitude to report as point sources. The nonpoint sources inventoried include main source categories:
- Solvent use (volatile chemical products)
- Agriculture sources
- Stationary source fuel combustion
- Commercial source fuel combustion
- Gasoline storage and transport
- Industrial processes
- Crop residue burning
- Residential open burning
- Commercial cooking
- Mining and quarrying
- Windblown dust
- Waste disposal, treatment, and recovery processes
Generally, EPA estimates emissions from wildfires and prescribed burning using a satellite detection approach combined with fire models and fire information provided by state organizations. The sources noted above were identified as relevant by the Nonpoint Methods Advisory Committee (NOMAD) sponsored by EPA. Where applicable, point source activity data is subtracted from nonpoint calculations to avoid double counting.
Onroad or mobile sources include the various categories of vehicles driven on Idaho roads that use gasoline, diesel, and other fuels. These sources are calculated using the Motor Vehicle Emissions Simulator (MOVES). This model allows states to update the model input files for state-specific county data versus the EPA defaults for the model. DEQ gathers data from the statewide vehicle registration database, traffic counters, and Travel Demand Modeling in urban counties. These data are input into the model for all 44 counties using the format required by MOVES.
Nonroad sources include off-road mobile sources that use gasoline, diesel, and other fuels. The nonroad portion of the PEI is also calculated using MOVES. Inventory for the nonroad mobile sources include recreational vehicles, construction equipment, industrial and commercial equipment, lawn and garden equipment, agricultural equipment, light commercial equipment, airport service equipment, and railway maintenance equipment.