Final Amendments to National Emission Standards for Hazardous Air Pollutants: Rubber Tire Manufacturing

The U.S. Environmental Protection Agency (U.S. EPA) has published final amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Rubber Tire Manufacturing (40 CFR 63, Subpart XXXX) to establish emissions standards for the rubber processing subcategory. The proposed rule was initially published last year on November 16, 2023 and the final rule was published on November 29, 2024.

The Final Amendments

This rule applies to rubber tire manufacturing plants that are major sources of hazardous air pollutants (HAPs), and the changes establish new requirements for the “rubber processing” subcategory, which is defined as “the collection of all rubber mixing processes (e.g., banburys and associated drop mills) that either mix compounds or warm a rubber compound before the compound is processed into components of rubber tires” (89 FR 94886 Section V.A). Simply put, any rubber mixer at your HAP major source facility will be affected by the rule. Any existing source at the time of the proposed rule (i.e., sources that commenced construction or reconstruction on or before November 16, 2023) is required to comply with the new standards by November 29, 2027. Any source that commenced construction or reconstruction after November 16, 2023 must comply with the new standards by November 29, 2024 or upon startup, whichever is later.

Emissions Standards

The U.S. EPA has set limits on total hydrocarbons (THC) and filterable particulate matter (fPM) (or alternatively metal HAPs) to regulate HAP emissions from rubber processing. THC is being used as a surrogate for organic HAP and fPM is being used as a surrogate for metal HAPs. U.S. EPA has set the THC standard for both new and existing sources at 64 grams (g)/megagram (Mg) of rubber processed (1.3×10^5 pound (lb)/million ton (Mton) of rubber processed) which is equivalent to three times the representative detection level (3XRDL). Sources must comply with this limit on a 15-day rolling average basis.

Sources may comply with either an fPM limit as a surrogate for metal HAPs or a metal HAP limit. The standard for metal HAPs is 5.4×10^-2 g/Mg of rubber processed (110 lb/Mton of rubber processed) and the standard for fPM is 3.0 g/Mg of rubber processed (6.0×10³ lb/Mton of rubber processed).

Initial and Continuous Compliance Requirements

Initial compliance with the new emissions limits is to be demonstrated via performance testing within 180 days of startup for new sources and by November 29, 2027 for existing sources. Sources are required to conduct subsequent performance tests every five years. Additionally, U.S. EPA is requiring that a THC continuous emissions monitoring system (CEMS) must be installed at each control device or uncontrolled mixer exit to continuously monitor THC emissions using a monitor that is set with a range of 0 to 50 parts per million by volume (ppmv). Exhaust flow rate measured during the performance test would be used to convert ppmv THC to mass of THC. Sources must also continuously monitor the daily mass of the mixed rubber compound in each mixer. Sources can demonstrate compliance with the 15-day rolling average THC standard in one of three ways:

• For each mixer separately;
• For a group of mixers routed to the same control device or stack; or
• On a facility-wide average basis.

U.S. EPA is also requiring that facilities install and operate a bag leak detection system (BLDS) on any fabric filters used to control fPM/metal HAP emissions from rubber mixing. Additionally, each emissions capture system or enclosure and closed vent system on each rubber processing mixer must be inspected annually to ensure that each system or enclosure vents capture emissions through a closed vent system, except that dilution air may be added to emissions streams for temperature control in a fabric filter. Compliance reports and notifications will be submitted electronically through U.S. EPA’s Compliance and Emissions Data Reporting Interface (CEDRI).

What’s Different from the Proposed Amendments?

Several things have changed between the proposed and final rule, including emissions averaging across mixers, subcategories, and reporting requirements.

Emissions averaging across mixers was introduced in the final rule to account for various mixer and thermal oxidizer configurations. If a facility routes multiple mixers to the same stack or RTO, this newly allowed emissions averaging will help simplify the compliance demonstration.

The standards did change as a result of U.S. EPA’s consideration of additional data. Specifically, the subcategories for silica and non-silica THC standards have been removed and the standards are now equivalent for new sources and existing sources. The THC limit has been raised to 64 g/Mg for all sources from 9.4 g/Mg for existing silica sources, 45.4 g/Mg existing non-silica sources, 2.1 g/Mg new silica sources, and 17.2 g/Mg new non-silica sources. The metal HAP standard dropped from 0.37 g/Mg to 5.4×10^-2 g/Mg and fPM rose from 1.70 g/Mg to 3.0 g/Mg.

The requirement to continuously monitor the firebox temperature and maintain the temperature above the level established during the performance test on a daily average basis for facilities that use a thermal oxidizer was removed from the final rule by U.S. EPA.

U.S. EPA also updated the electronic reporting requirement at 40 CFR §63.6009(k) and §63.6010(g) and (h) to provide an email address to which sources can electronically transmit confidential business information (CBI) to U.S. EPA when submitting compliance reports.

Conclusion

Each HAP major source facility with rubber mixers will need to determine what new standards and requirements apply and develop a compliance plan. Because the standards are quite low, facilities are likely to need additional controls for organic HAP emissions and may need upgraded fabric filters for PM control. ALL4 can assist facilities with understanding these new regulatory requirements, planning for compliance, preparing emissions test plans, reviewing emissions test data, obtaining vendor quotes for new emissions control or monitoring systems, setting up new monitoring systems, establishing electronic compliance systems, and compliance reporting. If you have any questions, feel free to reach out to me at bjohnson@all4inc.com or (502) 874-4500 or to Philip Crawford at pcrawford@all4inc.com or (984) 777-3119.