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U.S. EPA’s Proposed Updates to the Wood Products NESHAP

Posted: May 23rd, 2023

Authors: Amy M. 

The U.S. Environmental Protection Agency (U.S. EPA) proposed significant amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Plywood and Composite Wood Products (PCWP) on May 18, 2023.  The current NESHAP requirements focus primarily on organic hazardous air pollutant (HAP) emissions from certain types of wood products dryers and presses. The proposed amendments address the 2007 partial remand and vacatur of portions of the original 2004 PCWP NESHAP (U.S. EPA had not set any standards for several types of emissions units that had no HAP controls) and a petition for reconsideration that U.S. EPA received on the 2020 Risk and Technology Review (RTR) of the NESHAP. Basically, U.S. EPA is proposing to (1) set emission standards for several types of process units that are part of the affected source but do not currently have standards (including lumber kilns) and (2) set emission standards for several new pollutants for biomass direct-fired wood products dryers. Major proposed amendments to the rule are discussed below.

Work Practice Standards for Lumber Kilns

Lumber kilns are part of the affected source under the PCWP NESHAP but are not currently subject to any standards. U.S. EPA is proposing to establish work practice standards for lumber kilns. The proposed work practice has four elements:

  • An operation and maintenance plan for all types of kilns,
  • Annual burner tune-ups for direct-fired kilns,
  • Work practices to limit over-drying of lumber using temperature and/or moisture,
  • A definition of over-dried lumber based on the variance from the target moisture content of the lumber grade.

The third element of the work practice proposed by U.S. EPA involves the facility selecting between three options to limit HAP emissions from lumber kilns: (1) limiting the 3-hour block average temperature in the kiln based on the type of kiln being used (batch indirect fired, batch direct fired, or continuous), (2) limiting the semiannual average in-kiln moisture content of the wood being dried, or (3) establishing a site-specific plan that contains both temperature and lumber moisture content limitations, where the moisture of the lumber may be measured at a location other than in the kiln. These options are necessary because not all species of wood can be efficiently dried at the temperatures proposed in option 1 and not all facilities measure in-kiln lumber moisture per option 2. U.S. EPA proposes to require that the site-specific plan be incorporated into the facility’s Title V permit if option 3 is selected.

Additional Standards for Direct-Fired Dryers

U.S. EPA has proposed to add work practice standards for all direct-fired dryers and numeric standards for emissions of filterable particulate matter (PM), mercury, hydrochloric acid (HCl), and polycyclic aromatic hydrocarbons (PAH) from biomass direct-fired dryers. U.S. EPA proposes to define a natural gas direct-fired dryer as one where greater than 90 percent of the direct heat results from gas combustion and a biomass direct-fired dryer as one where at least 10 percent of the direct heat comes from biomass combustion.

The proposed work practice standards include annual tune-ups (similar to the Industrial Boiler NESHAP) to ensure good combustion (and limit emissions of dioxins/furans) and monitoring of bypass stack use during startup or shutdown. The proposed numeric standards for biomass direct-fired dryers are subcategorized according to dryer type (rotary strand, green rotary, dry rotary, tube, and softwood veneer) and compliance must be demonstrated via continuous monitoring and 5-year stack testing. Two options are provided for compliance with the new numeric standards: production based or concentration based.

Standards for Resinated Material Handling (RMH) Process Units

RMH process units are resin tanks, softwood and hardwood plywood presses, engineered wood products presses and curing chambers, blenders, formers, finishing saws, finishing sanders, panel trim chippers, reconstituted wood products board coolers (at existing affected sources), hardboard humidifiers, and wastewater operations. These process units handle resin or resinated wood material downstream of the point in the PCWP process where resin is applied. U.S. EPA is proposing work practice standards for these RMH process units because they do not currently have any requirements in the rule and are generally fugitive sources of organic HAP. The proposed standards are:

  • Vapor pressure limit of 5.2 kPa (0.75 psia) for resin storage tanks storing resins that do not qualify as non-HAP resins.
  • Use only a non-HAP resin OR use a resin with a maximum true vapor pressure less than or equal to 5.2 kPa (0.75 psia) OR use a combination of resins meeting the first two options.
  • Process wood material that was purchased pre-dried to a moisture content of no more than 30 weight percent, dry basis or that has been dried in a dryer located at the PCWP facility. This requirement does not apply to wet formers or wastewater operations.
  • Four options for reducing HAP emissions from wastewater operations.

A non-HAP resin is defined as resin with HAP contents below 0.1% for carcinogens and below 1.0% for non-carcinogens. Not all resins used at PCWP facilities can qualify as non-HAP resins so U.S. EPA has provided options for limiting HAP emissions from RMH process units.

Other Proposed Requirements

Other requirements U.S. EPA is proposing to add are:

  • Numeric standards for dry and green wood atmospheric refiners,
  • Work practice standards for stand-alone digesters and fiber washers,
  • Numeric standards for fiberboard mat dryers and press predryers at existing sources,
  • Work practice standards for log vats,
  • Numeric standards for process units with methylene diphenyl diisocyanate (MDI),
  • Standards for mixed process streams,
  • Repeat testing and parameter monitoring requirements for the added numeric standards.

U.S. EPA is also proposing to remove the emissions averaging provisions, update the electronic reporting template, and make various corrections/clarifications to rule text.

The Path Forward

Comments on the proposed amendments to the PCWP NESHAP are due July 3, 2023, and U.S. EPA is currently under a court-ordered deadline to sign the final rule by November 11, 2023. A 45-day comment period is not a lot of time to read and understand the proposed changes and to prepare comments providing feedback to U.S. EPA, so you will want to get started now if this rule amendment will affect you. Note that the regulatory text was not included in the Federal Register notice, but a redline/strikeout version of the rule is located in the rulemaking docket at regulations.gov for review.

U.S. EPA is proposing to give existing facilities three years to comply with the amended requirements, although any facility with a lumber kiln that chooses the site-specific work practice option will likely need to prepare the plan within 180 days of the final rule. The new standards could result in the need for process changes, so it will be important to gather data as early as possible to determine the need for any modifications to comply with the new standards. ALL4 is reviewing the proposed rule and preparing technical comments; let us know if your company requires assistance reviewing the proposed rule and preparing a compliance strategy. Feel free to reach out to Amy Marshall at amarshall@all4inc.com with questions.


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