As mentioned previously, for an annual emission report (AER), most people will simply use an emission factor when estimating emissions from their equipment.
That begs a follow-up question: Where do I find emission factors to estimate air emissions?
In our experience, the best place to find emission factors is the Environmental Protection Agency’s AP-42 database, which contains emission factors from various industries. The AP-42 database is helpful because it also gives you the background of the industry that you’re dealing with. For example, if you’re calculating emissions from an oil and gas facility, AP-42 will tell you the most common types of equipment used in the industry as well as the types of emissions that can be expected from the facility.
As we also mentioned earlier, it’s important to exercise care when using emission factors since emissions from a source can vary significantly, and in most cases, the use of emission factors can overestimate emissions. From the EPA’s website:
Emissions Factors Uncertainty: Uncertainty is dependent on the kind of emissions released, the number of tests used to determine the emissions factor, the appropriate decision level (or percentile) within the distribution range, and the number of similar emissions units within a specific area.
Nonetheless, emission factors, when used with care, are an excellent way to estimate emissions from a piece of equipment, and AP-42 is a pretty big database of these factors.
Other sources for emission factors include the websites of the different air agencies, such as the South Coast Air Quality Management District (SCAQMD).
A few valuable resources for emission factors on the SCAQMD’s website include:
- The guidance document for the AB 2588 Air Toxics “Hot Spots” Program
- The SCAQMD’s AER guidebook for criteria pollutants (PDF)
- The SCAQMD’s certified engine program (or you can read our post)
- The SCAQMD’s AER homepage
Other places to find emission factors include trade associations, equipment manufacturers, safety data sheets (SDS), etc. The EPA also has an entire page dedicated to Related Emissions Factor Documents.
Whatever the case, if you find that you’re having trouble locating an emission factor, contact us and we’ll be glad to help you out.
