Statewide Emissions Inventory Program

Purpose and Method

The emissions inventory is one means used by the state to assess the level of pollutants released into the air from various sources. A group of common air pollutants regulated by the Environmental Protection Agency (EPA) are called criteria air pollutants; these pollutants were determined based on their health and/or environmental effects. The second group of pollutants included in this report are the hazardous air pollutants.

The Statewide inventories summarize emissions for the following criteria pollutants, in tons per year, reporting from point, area and mobile sources within the State of Utah:

Hazardous air pollutant emissions are reported for each county in pounds per year, listed by chemical or chemical class.

If comparing inventories, the reader should note that emission estimation methods and emission factors are continually changing and improving, which may cause emissions to appear higher or lower from one year to the next without any actual emission change. In addition, the application of new pollution controls will change emissions at a source and should be accounted for when comparing emissions from different years.

The inventory is created in conjunction with Point , Biogenic, and Mobile Sources for SIPs, Plans, and Statewide Inventories.

Point Sources

Contact: Scott Hanks (801) 536-4066

Point sources are stationary, commercial or industrial sources included in the State Implementation Plan (SIP), major sources that emit more than 100 tons/yr. of a criteria pollutant, or New Source Performance Standard (NSPS) sources. The point source annual emission inventory for criteria pollutants is collected under authority of Utah Administrative Code. The inventory information is required to track SIP progress, calculate the operating permit program emission fee, fulfill annual reporting requirements to EPA, and supply information to the general public.

Area Sources

Contact: Greg Mortensen (801) 536-4018

Area sources are stationary sources that are too small or too numerous to be treated as individual point sources. The area source inventory is determined from local demographic information, state energy and agricultural statistical data, specific information surveys, and submitted inventories. Source categories range from agricultural dust and outdoor grilling to residential wood combustion, solvent use, and oil and gas production. The oil and gas inventory is unique in the area source inventory as rather than using surrogate activity data and generic emission factors, oil and gas companies submit an inventory for their facilities.

Biogenic sources comprise the natural (non-anthropogenic, such as forests, vegetation and soils) area sources contribution to VOCs and “event” emission sources, such as wildfires, contribute various pollutants to the airshed. Both of these pollution sources are also under the purview of area sources.

Note: The area source inventory remains in development and experiences significant fluctuations. Frequently one inventory is not readily comparable to another due to changing methods and data sources.

Mobile Sources

Contact: Peter Verschoor (801) 536-4186

The mobile source inventory includes both on-road and non-road sources. Highway vehicles such as cars, light duty trucks, heavy-duty trucks and motorcycles using gasoline and diesel fuels are referred to as on-road mobile sources. Non-road mobile sources includes a wide variety of internal
combustion engines not associated with highway vehicles, such as locomotives, airplanes, and small residential, recreational, and commercial engines. The emissions are calculated from vehicles miles traveled (VMT), emission factors for highway vehicle classes obtained from EPA’s MOBILE5A model, federal models, and other EPA-derived factors.