Plywood and Composite Wood Products (PCWP) NESHAP Summary

3. What Are the Compliance Options?

Thermal Oxidizer Diagram

1. Reduce THC emissions (as carbon, and minus methane if you wish to subtract methane) by 90 percent.
2. Reduce methanol emissions by 90 percent.
3. Reduce formaldehyde emissions by 90 percent.
4. Limit the concentration of THC (as carbon, and minus methane if the source wishes to subtract methane) in the outlet of the add-on control system to 20 parts per million by volume, dry basis (ppmvd).
5. Limit the concentration of methanol in the exhaust from the add-on control system to 1 ppmvd (can be used only if the concentration of methanol entering the control device is greater than or equal to 10 ppmvd).
6. Limit the concentration of formaldehyde in the exhaust from the add-on control system to 1 ppmvd (can be used only if the concentration of formaldehyde entering the control device is greater than or equal to 10 ppmvd).

Catalytic Thermal Oxidizer Diagram

In the first three options ((1) through (3)), the 90 percent control efficiency represents a total control efficiency. Total control efficiency is defined as the product of the capture efficiency and the control device efficiency. For process units such as rotary strand dryers, capture efficiency is not an issue because the rotary strand dryer has a single exhaust point which is easily captured by the control device. However, for presses and board coolers, the HAP emissions cannot be completely captured without installing an enclosure. If the enclosure meets the criteria for a wood products enclosure as defined in Sec. 63.2292 in the PCWP MACT final rule, then the source can assign the enclosure a capture efficiency of 100 percent. The facility must test other enclosures to determine capture efficiency using US EPA Test Methods 204 and 204A through 204F (as appropriate) found in 40 CFR part 51, appendix M, or the alternative tracer gas procedure in appendix A of the PCWP MACT final rule. For the three concentration options ((4) through (6)), the source must have an enclosure that either meets the criteria for a wood products enclosure or achieves a capture efficiency greater than or equal to 95 percent.

The six compliance options are equivalent ways to express the HAP control levels that represent the MACT floor. Because the compliance options are equivalent for controlling HAP emissions, the source is required to meet only one of the six compliance options for add-on control systems. However, the source must designate in their permit which one of the six options they have selected for the affected process unit. If the source plans to operate a given process unit under different conditions, they may incorporate multiple compliance options for the add-on control system into their permit, as long as each separate operating condition is identified along with the compliance option that corresponds to that operating condition.

Emissions Averaging Compliance Option
Emissions averaging is a means of achieving the required emissions reductions in a less costly way. Therefore, if the facility operates an existing affected source, for each process unit they could choose to comply with the emissions averaging provisions instead of the production-based compliance options or add-on control system compliance options.

Emissions averaging is a system of debits and credits in which the credits must equal or exceed the debits. “Debit-generating process units” are the PCWP process units that are required to meet the control requirements but that the source chooses to either not control or under-control. “Credit-generating process units” are the PCWP process units that the source chooses to control that are not required to be controlled under the standards. When determining the actual mass removal (AMR) of HAP, the source may include partial credits generated from debit-generating process units that are under-controlled (e.g., the source may receive credit for 25 percent control of a debit-generating process unit). Control devices used for credit-generating process units may not be assigned more than 90 percent control efficiency.

Under the emissions averaging provisions, the source would determine the required mass removal (RMR) of total HAP from debit-generating process units for a 6-month compliance period. Total HAP is defined in the PCWP MACT final rule to include acetaldehyde, acrolein, formaldehyde, methanol, phenol, and propionaldehyde. The RMR would be based on initial total HAP measurements for each debit-generating process unit, the process unit operating hours for a 6-month period, and the required 90 percent control system efficiency. One hundred percent of the RMR for debit-generating process units would have to be achieved or exceeded by the AMR of total HAP achieved by credit-generating process units. The AMR is determined based on initial performance tests, the total HAP removal efficiency (not to exceed 90 percent) of the control systems used to control the credit-generating process units, and the process unit operating hours over the 6-month period.

There are some restrictions on use of the emissions averaging provisions in the PCWP MAC final rule. The source must limit emissions averaging to the process units located within their affected source. Emissions averaging may not be used at new affected sources. The source may not include in an emissions average those process units that are not operating or that are shut down. Only PCWP process units using add-on control systems may be used to generate credits.


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