A “Meaningful” Process Change
You have an air permit to operate equipment at your facility. The equipment has flexibility in terms of what raw materials can be used (e.g., a coating line can use different coatings and does depending on the part that is being painted). You may believe that this change doesn’t require an evaluation beyond looking at your permit-to-install (PTI) and making sure that the existing emission limits are not going to be exceeded as a result of the change.
For instance, say you have a 2 pounds/hour (lbs/hr) emission limit on isopropyl alcohol in your PTI. This limit is based on the coatings that were proposed in the application that yielded the PTI way back when you were preparing the application. The new coating doesn’t have any isopropyl alcohol but does have xylene and you’d like to make the change from isopropyl alcohol emissions to xylene emissions. Can this change be made under the current PTI? How can this be determined?
The answer is found in the Rule 285(b) exemption that allows for:
“Changes in a process or process equipment which do not involve installing, constructing, or reconstructing an emission unit and which do not involve any meaningful change in the quality and nature or any meaningful increase in the quantity of the emission of an air contaminant therefrom.
Examples of such changes in a process or process equipment include, but are not limited to, the following:
Change in the supplier or formulation of similar raw materials, fuels, or paints and other coatings.”
The term meaningful change is the key and a procedure for determining meaningful change is found in a guidance document that can be found on EGLE’s webpage. The guidance document is relatively new and it’s only a matter of time before its use will be required.
First, it is necessary to understand Michigan’s Rule 225. Rule 225 requires that emissions of a specific chemical like isopropyl alcohol do not result in an unhealthy concentration in the community. To determine whether there may be an unhealthy concentration, EGLE estimates the maximum concentration of the chemical in the community and compares it to health standards for that specific chemical. These health standards are called “screening levels.” If EGLE believes a chemical concentration may exceed the screening level, they will impose an emission limit for that chemical (e.g., 2 lbs/hr of isopropyl alcohol emissions).
To determine whether the change can be made, first determine the existing hazard potential (HP) of the coating line, which is the maximum hourly emissions of the chemical (isopropyl alcohol, divided by the screening level). For the isopropyl alcohol example the screening level is 220. Therefore, the HP (existing) = 2 / 220 = 0.00909.
Then determine the HP for the proposed change. Assume the maximum xylene emission rate is 3 lbs/hr. The xylene screening level is 390. Therefore, the HP (proposed) for xylene is calculated as 3 divided by 390, which equals an HP of 0.00769.
In this instance, the HP decreased as a result of the change and the change could be allowed under Rule 285(b) and is not considered meaningful. As you may expect, there are some caveats to be aware of, but this procedure is something any environmental manager should be familiar with, especially if changes in supplier formulations are routine.
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