Potential-To-Emit – The Determinate Of Air Permitting Levels

Nothing has been more misunderstood in the environmental compliance world than the term “Potential-To-Emit” (PTE). The EPA and state regulators put definitions in the Code of Federal Registers and state regulations, respectively. They even put out guidance documents. However, so many companies get tripped up in determining their PTE.

The good news is that 99% of the time, all businesses are measured by the same criteria pollutants and objective criteria no matter what state you’re in. EPA Region V makes sure that Indiana, Michigan, Wisconsin, Ohio, Illinois, and Minnesota do this process universally. It is a worst-case potential emission total of criteria pollutants and hazardous air pollutants that your location could emit over 24 hours per day, 365 days per year (8760 hours).

While concepts like PTE ‘Prior-To-Control’ and ‘After Control’ are easy to understand, sometimes regulators determine that emissions controls are ‘integral’ to your process meaning that you can’t run your operations without those controls. Therefore, your PTE Prior to Control is actually the emissions that exhaust after they are captured and controlled by emissions control equipment, like a baghouse or thermal oxidizer. The State of Indiana does this for woodworking operations due to the judgment from the 1993 case filed by Kimball Hospitality Furniture Inc., where the judge determined that their controls were necessary to operate. So, all woodworking operations since also share this integral determination.

Other key concepts of ‘Bottlenecking’ and ‘Debottlenecking’ are not easily understood. Here’s a ‘Bottlenecking’ example. If your operations follow a specific path to completion (i.e, A—B—C—D), it is important to know how each process affects the others. If Process A can produce 1000 units per hour, but Process D can only produce 300 per hour and all processes are in sequence, it is incorrect to base your emissions off of Process A’s maximum throughput. Ultimately, Process A will only produce 300 units per hour averaged over the course of a year. So, whatever materials, fuels, or equipment that you use that can produce those 300 units that emit listed pollutants, those determine your PTE.

For Debottlenecking, here’s an example. You want to replace Process D’s equipment or materials and it would allow you to produce 500 units per hour. Not only do you have an increase in Process D’s throughput (300à500) and emissions (assuming it’s an emission unit), but you have now increased your throughput and emissions in the remaining processes (also assuming those are emission units).

Companies can also limit their PTE. With use of a control device or throughput limitations to be ‘federally enforceable’, this ‘synthetic minor’ permit limitation can prove helpful as an avoidance limit.

There are other concepts to explore in determining your PTE, but hopefully, I have provided insight into the process.