Subpart ZZ - Ceramics Manufacturing
This page provides resources for subpart ZZ reporters, including implementation information as well as supporting documents for relevant rulemakings.
Summary
This source category applies to any facility that uses nonmetallic, inorganic materials, many of which are clay-based, to produce ceramic products such as bricks and roof tiles, wall and floor tiles, table and ornamental ware (household ceramics), sanitary ware, refractory products, vitrified clay pipes, expanded clay products, inorganic bonded abrasives, and technical ceramics (e.g., aerospace, automotive, electronic, or biomedical applications).
The source category includes facilities that annually consume at least 2,000 tons of carbonates (CO32-), – either as raw materials or as a constituent in clay, which is heated to a temperature sufficient to allow the calcination reaction to occur, – and operate a ceramics manufacturing process unit. A ceramics manufacturing process unit is a kiln, dryer, or oven used to calcine clay or other CO32--based materials to produce a ceramics product.
Frequently Asked Questions
The source category definition in 98.520(a) refers to “2,000 tons of carbonates”. What are the units of measurement (metric tons, English tons, short tons) in this phrase, and how are “carbonates” defined? Are “carbonates” separate CO3 ions, or are they materials like limestone, which contains carbonates?
The subpart ZZ source category as defined under 98.520(a) applies to facilities that annually consume at least 2,000 tons of carbonates. For the purposes of the subpart ZZ source category definition, “tons” refers to “short tons”. For example, subpart ZZ Equation 1 in 98.523(b)(4) used to calculate CO2 process mass emissions includes a conversion factor to convert raw material usage in short tons to metric tons.
Examples of carbonates are included in Table 1 of subpart ZZ.
If my facility is covered by subpart ZZ, would I also have to report emissions under subpart C?
Ceramics facilities must report emissions in accordance with subpart C if they contain an applicable stationary fuel combustion source. Per 40 CFR 98.2(a)(2), the annual GHG report must cover stationary fuel combustion sources (subpart C), miscellaneous use of carbonates (subpart U), and all applicable source categories listed in Table A-3 and Table A-4 of subpart A.
If the facility operates a qualified continuous emissions monitoring system (CEMS), that meets the conditions specified in § 98.33(b)(4)(ii) or (b)(4)(iii), the facility must calculate and report under subpart ZZ the combined process and combustion CO2 emissions by operating and maintaining a CEMS to measure CO2 emissions according to the Tier 4 Calculation Methodology specified in § 98.33(a)(4) and all associated requirements for Tier 4 in subpart C. If CEMS is not used, then process emissions are reported under subpart ZZ and combustion emissions are reported under subpart C.
Does the 25,000 metric tons of carbon dioxide equivalent (mtCO2e) reporting threshold apply to subpart ZZ ceramics manufacturing facilities?
Yes. Per section 98.2(a)(2), the program requirements apply to facilities that emits 25,000 mtCO2e or more per year in combined emissions from stationary fuel combustion, miscellaneous uses of carbonate, and all applicable source categories that are listed in Table A-3 and Table A-4. Subpart ZZ is included in Table A-4 of subpart A. Furthermore, subpart ZZ is limited to facilities that meet the source category definition of a ceramics manufacturer in 98.520(a), such that they consume at least 2,000 tons of carbonates annually, either as raw materials or as a constituent in clay, that is heated to a temperature allowing calcination to occur.
Under 98.522(a) the regulation states to report CO2 process emissions from each process unit. Is each kiln a unit? Is this unit-by-unit reporting?
Yes, 98.522(a) states that facilities must report emissions from each ceramics process unit. A ceramics process unit is defined in 98.520(b) as a “kiln, dryer, or oven used to calcine clay or other carbonate-based materials for the production of a ceramics product.” Thus, each kiln, dryer, or oven used in this manner is a ceramics process unit, and emissions must be reported for each unit (i.e., unit-by-unit reporting).
For calculating GHG emissions, section 98.523(b)(3) states to apply the appropriate emission factor for each raw material. Does this mean you have to speciate the different carbonate-based raw materials?
Yes, speciation of each carbonate-based raw material charged to the ceramics process unit is required to calculate GHG emissions in subpart ZZ. Emission factors based on stoichiometric ratios for common carbonate-based minerals are included in Table 1 of subpart ZZ.
For calculating GHG emissions, section 98.523(b)(1) states facilities should measure the carbonate mass fraction or use the default value of 1. For some industries that use materials with very low carbonate fractions, the default value of 1 is an overestimate. Is there an alternative default value for such situations? What testing methods can be used to determine the mass fraction of a carbonate-based mineral? What about test methods that do not directly speciate?
The rule allows flexibility for facilities to determine the carbonate mass fraction for use in Equation 1 of subpart ZZ by either obtaining the carbonate mass fraction from the raw material supplier, sampling the raw material to analyze for the carbonate mass fraction, or using the default assumption of 1.0. If the reporter opts to use the default value of 1.0, then data from the raw material supplier or a chemical analysis are not required for that reporting year. Note that section 98.524(b) states that if it is determined that the mass fraction of a carbonate based raw material is below the detection limit of available industry testing standards, facilities may use a default value of 0.005. Subpart ZZ does not require facilities to assume that all carbonates listed in Table 1 to subpart ZZ are present in their raw materials.
Subpart ZZ provides flexibility in how a facility can sample the mass fraction of each carbonate-based raw mineral. Section 98.524(b) states that facilities “may conduct the sampling and chemical analysis using any x-ray fluorescence test, x-ray diffraction test, or other enhanced testing method published by an industry consensus standards organization (e.g., ASTM, ASME, API).” A facility could utilize a testing method that does not speciate in conjunction with other tests or information that results in speciated mass fractions.
Could facilities opt to estimate emissions based on the amount of product produced rather than the raw materials consumption methods in subpart ZZ?
No, facilities cannot use estimation methods that are not included in the 40 CFR Part 98 regulations. Ceramics facilities covered by subpart ZZ must use the methods specified by subpart ZZ.
Reporter Resources
Subpart ZZ Regulatory History
| Federal Register Date | Citation | Action | Description | First reporting year impacted |
|---|---|---|---|---|
| 4/25/2024 | 89 FR 31802 | Final Rule |
Updates global warming potentials (GWPs), expands the GHGRP to new source categories, and revises the requirements for certain sectors to improve the data collected and program implementation. |
2025 |