Lime Manufacturing NESHAP Supplemental Proposal Issued

A supplemental notice of proposed rulemaking to the 40 CFR Part 63, Subpart AAAAA (National Emission Standards for Hazardous Air Pollutants for Lime Manufacturing Plants [Lime Manufacturing NESHAP]) was published in the February 9, 2024 Federal Register. The U.S. Environmental Protection Agency (U.S. EPA) is proposing to revise the proposed hydrogen chloride (HCl), mercury, organic hazardous air pollutant (HAP), and dioxin/furans (D/F) emissions limits. Comments on this supplemental proposal are due March 11, 2024.

Background

To supplement the U.S. EPA’s 2020 residual risk and technology review (RTR) and as a result of a D.C. Circuit Court decision, the U.S. EPA proposed maximum achievable control technology (MACT) standards for the following previously unregulated HAPs on January 5, 2023: HCl as a surrogate for acid gas HAPs, mercury, total hydrocarbon (THC) as a surrogate for organic HAP, and D/F. This supplemental proposal addresses concerns related to economic impacts of the 2023 proposal on small businesses and data quality issues identified during the comment period.

Updates to Proposed Emission Standards

HCl – Dolomitic lime (DL) and dead burned dolomitic lime (DB) subcategories were added for vertical kilns and the proposed numerical limits for several subcategories were updated (see Tables 2 and 3 of the preamble to compare both sets of limits). Corrections were made to the kiln type subcategorization used in the calculations to establish the proposed limits.

The Clean Air Act (CAA) allows the U.S. EPA to consider a health-based emission limit (HBEL) for a HAP with an established health threshold. A D.C. Circuit Court decision related to the Brick NESHAP found that the U.S. EPA had not sufficiently supported its determination that HCl has an established health threshold. Scientific evidence and discussion on whether or not HCl has a health threshold is provided in the preamble and docket for this rulemaking. Thus, U.S. EPA is proposing an HBEL for HCl of 300 tons per year (tpy), with short-term emissions not to exceed 685 pounds per hour (lb/hr). The U.S. EPA is requesting comment on an appropriate structure for incorporating the HBEL for HCL in the rule text. This is the first time in any recent rulemaking that U.S. EPA has proposed to incorporate an HBEL and will be of interest to other industries where NESHAP are being revised to fill regulatory gaps.

Mercury – As part of the January 5, 2023 proposed rulemaking, the U.S. EPA evaluated the use of an intra-quarry variability (IQV) factor to account for the naturally occurring variability of mercury content of the raw materials. The U.S. EPA concluded that they did not have sufficient data to apply an IQV factor at that time. The lime industry provided clarification and additional information concerning storage pile homogenization and quarry sampling during the comment period, and the U.S. EPA has applied an IQV factor in this update. The originally proposed mercury emission limit for new and existing quick lime (QL) and DL sources increased from 24.9 pounds per million tons of lime produced (lb/MMton) for both new and existing sources to 27 lb/MMton for new sources, and 34 lb/MMton for existing sources in the QL subcategory (see Tables 2 and 4 of the preamble to compare all mercury limit changes).

Subcategories were removed for new and existing sources because the U.S. EPA determined there were minimal differences in emissions across kiln types and that residence time has little impact on mercury emissions.

THC as a surrogate for organic HAP – The U.S. EPA is proposing to change the format of the standard for organic HAP emissions from THC as a surrogate to an aggregated emission standard comprised of the eight organic HAP consistently identified in the data analysis (formaldehyde, acetaldehyde, toluene, benzene, xylenes [m, o, and p isomers], styrene, ethylbenzene, and naphthalene). The proposed emission limit is equivalent to the sum of three times the representative detection level (3xRDL) of the test method for each of the eight organic HAPs (1.7 ppmvd at 7 percent oxygen versus the originally proposed THC limit of 0.86 ppmvd as propane at 7 percent oxygen).

D/F – The U.S. EPA is proposing to update the proposed D/F numerical limits for new and existing sources based on a change to the sample collection volume used in the 3xRDL calculations. This change results in a slightly higher emissions limit (0.037 ng/dscm (TEQ) at 7 percent oxygen versus the originally proposed 0.028 ng/dscm (TEQ) at 7 percent oxygen).  As with the original proposal, the limits for new and existing sources are the same. The U.S. EPA is requesting any additional D/F stack test data comprised of at least three test runs to supplement its data set.

Other Proposed Changes

• Definitions of new and existing source will be based on the January 5, 2023, proposal date.
• Existing sources will have three years from the effective date of the final amendments to comply with the new emissions limits, subject to certain exemptions.
• The U.S. EPA is proposing a definition of “stone produced” used in the units of measure for the HCl and Hg emissions limits to indicate it refers to the production of lime.
• The U.S. EPA is proposing to add emissions averaging which provides compliance demonstration flexibility. The emissions averaging alternative is for HCl and mercury emissions across existing kilns in the same subcategory located at the same facility. A 10 percent adjustment factor will be incorporated into the emissions averaging approach lowering the proposed averaging limit (e.g., alternative mercury averaging 31 lb/MMton stone produced versus 34 lb/MMton stone produced with no averaging).

Implications of the Proposal

There are 34 major sources subject to the Lime Manufacturing NESHAP. The final rule will include first-time emissions limits for these facilities, which will come with new requirements for emissions testing, monitoring, reporting, and (in some cases) additional controls. While the re-proposal lessens the potential burden at a facility somewhat, the U.S. EPA estimates the average annual cost per facility to comply with these new requirements will be more than $5 million. The U.S. EPA is seeking comments on all aspects of the proposal, particularly the proposed HBEL for HCl, and is requesting additional D/F stack test data.

If your facility is impacted by this rule, ALL4 can help you develop comments, collect and submit data, develop a compliance strategy, design a stack testing program, and improve your monitoring and data collection systems. Please reach out to your ALL4 Project Manager or JP Kleinle for more information on how we can help. We’ll be tracking the final rule requirements, which are due to be signed on June 30, 2024.