Final Lime Manufacturing NESHAP – U.S. EPA decides against HBEL

The final amendments to 40 CFR Part 63, Subpart AAAAA (National Emission Standards for Hazardous Air Pollutants for Lime Manufacturing [Lime Manufacturing NESHAP]) were signed on June 28, 2024 and were published in the July 16, 2024 Federal Register. With this final rulemaking, the United States Environmental Protection Agency (U.S. EPA) is setting maximum achievable control technology (MACT) emissions standards for previously unregulated hazardous air pollutants (HAP):

• hydrogen chloride (HCl);
• mercury (Hg);
• organic HAP (as the sum of formaldehyde, acetaldehyde, toluene, benzene, xylenes (mixed isomer), styrene, ethyl benzene, and naphthalene); and
• dioxin/furans (D/F).

Background

The Lime Manufacturing NESHAP regulates HAP emissions from new and existing major source plants that use a lime kiln to produce lime product from limestone or other calcareous material by calcination. Lime kilns at pulp and paper mills and a few other specific types of units are not subject to the Lime Manufacturing NESHAP.

In its 2020 residual risk and technology review (RTR) for the Lime Manufacturing NESHAP, U.S. EPA found that the current rule provided an ample margin of safety to protect public health. However, in light of the Louisiana Environmental Action Network v. EPA, 955 F.3d 1088 (D.C. Cir. 2020) (LEAN) decision, U.S. EPA proposed revisions to the Lime Manufacturing NESHAP on January 5, 2023 and included emissions standards for the unregulated HAP. U.S. EPA published a supplemental proposal on February 9, 2024 that addressed economic impact concerns expressed in public comments. See ALL4’s blog covering the February 9, 2024 supplemental proposal for more details.

Final Emissions Standards

The following table summarizes the final emissions standards for the previously unregulated HAP by lime kiln type and type of lime produced. The limits are largely consistent with those proposed in the February 9, 2024 supplemental proposal, with the exception of the organic HAP limit. U.S. EPA agreed with public commenters on adjustments to how U.S EPA calculates the 3x representative detection limit (RDL) they are finalizing as the MACT floor, which resulted in a higher emissions limit than what was originally included in the supplemental proposal.

^ADolomitic lime (DL), quick lime (QL), dead burned dolomitic lime (DB).

^BOrganic HAP is an aggregated emission limit for formaldehyde, acetaldehyde, toluene, benzene, xylenes (mixed isomer), styrene, ethyl benzene, and naphthalene as a surrogate for total organic HAP.

Notably, U.S. EPA decided not to promulgate a health-based emission limit (HBEL) for HCl. Clean Air Act (CAA) section 112(d)(4) grants U.S. EPA the flexibility to set a less stringent emission limit for a HAP based on an established health threshold with an ample margin of safety than would otherwise be required using the technology-based method of setting MACT standards. In the February 9, 2024 supplemental proposal, U.S. EPA asked for public comment on the use of an HBEL for HCl, as opposed to a MACT standard, because the 2020 RTR demonstrated very low risk to public health from HCl emissions from the source category. However, in this final rulemaking, U.S. EPA abandoned its proposed HBEL and decided to set a MACT standard for HCl, which will certainly be of interest to other industries. The February 9, 2024 supplemental proposal was one of the few times that U.S. EPA has proposed to set an HBEL, and its exclusion from the final rule sets a potential precedent as other NESHAP are revised to cover low-risk, yet previously unregulated HAP pursuant to the LEAN decision.

The final rule includes an emissions averaging compliance alterative that allows facilities to comply with the applicable HCl and Hg limits by averaging emissions across multiple existing kilns in the same subcategory located at the same facility, at the cost of having to meet alternative emission limits that are 10% more stringent. Facilities that intend to use the emissions averaging compliance alternative must develop an emissions averaging plan detailing the affected units, control technologies installed, parametric monitoring, and HAP test plan.

Timing and Impacts

Although the pre-publication version of the rule had set the effective date 60 days from Federal Register publication, the revisions became effective as of July 16, 2024. The compliance date for existing affected sources is July 16, 2027. The final rule includes first-time emissions limits for the 34 major sources subject to the Lime Manufacturing NESHAP, as well as performance testing, monitoring, recordkeeping, and reporting requirements. Facilities may need to install additional controls to meet the new MACT standards. U.S. EPA in this rulemaking estimates the average capital investment per facility will be more than $14 million and the average annual cost per facility to comply with the requirements will be approximately $5 million.

Summary

The revised rules will add a substantial compliance burden on the affected facilities and will require many to consider a permitting and compliance strategy that involves additional controls to meet the standards. It remains to be seen whether transitioning from major to area source status will be a viable option for facilities to avoid these standards because U.S. EPA is contemplating changes to the “Major MACT to Area” provisions and rethinking the prior “Once In, Always In” policy. If you have questions on the revised rules or need assistance with planning for and implementing these new requirements, ALL4 can help you develop and implement a compliance strategy, design a stack testing program, and collect and submit data and reports. Reach out to either your ALL4 Project Manager or Caleb Fetner at cfetner@all4inc.com for assistance with these new requirements.