Proposed Amendments to NESHAP EEE – Hazardous Waste Combustor MACT

The U.S. Environmental Protection Agency (U.S. EPA) proposed revisions to the National Emission Standards for Hazardous Air Pollutants (NESHAP) from Hazardous Waste Combustors (HWC MACT) (40 CFR Part 63, Subpart EEE) in the Federal Register on November 10, 2025 as a result of its risk and technology review. The HWC NESHAP regulates hazardous air pollutant (HAP) emissions from hazardous waste burning incinerators, cement kilns, lightweight aggregate kilns, solid and liquid fuel boilers, and hydrochloric acid production furnaces at both area and major sources of HAPs. Although no changes are proposed as a result of the risk and technology review, U.S. EPA has proposed to establish gap-filling standards for hydrogen fluoride (HF) and hydrogen cyanide (HCN) for certain types of units at major sources; eliminate the startup, shutdown and malfunction (SSM) exemption; add a work practice standard for periods of SSM; add electronic reporting procedures and requirements; allow states to choose to exempt area sources from certain permitting requirements; and make other clarifications and corrections.

Hydrogen Fluoride and Hydrogen Cyanide

U.S. EPA is proposing the following standards for HF and HCN at major sources. U.S. EPA is not proposing to regulate HF and HCN at area sources.

U.S. EPA is proposing that compliance with the emissions limits would be required within three years after the publication of the final rule and that demonstration through an initial compliance test would occur no later than six months after the compliance date, with subsequent compliance testing every five years. For affected facilities that commence construction or reconstruction after November 10, 2025, owners or operators would be required to comply with the new source emissions standards for HF and HCN no later than the effective date of the final rule or the date the source starts operations, whichever is later. U.S. EPA is also taking comments on whether health-based emissions limits should be established instead of the proposed numeric limits, but has not proposed a specific approach to developing such a limit.

Eliminating the SSM Exemption

After considering comments received on the July 2024 proposed rule, U.S. EPA is withdrawing the proposal to remove the malfunction exemptions. If finalized, the standards based on periods of normal operations would apply at all times. After considering comments received on the proposed removal of the malfunction exemption, U.S. EPA is withdrawing that proposal and instead proposing standards that would apply during periods of SSM, as discussed below.

Work Practice Standards for Periods of SSM

U.S. EPA is proposing work practice standards for periods of SSM. These standards would be enforceable requirements that minimize emissions of HAPs. The standards would include the following:

1. A requirement to combust only clean fuel (natural gas, propane, other Gas 1 fuels, distillate oil, syngas, ultra-low sulfur diesel, kerosene, hydrogen, refinery gas, liquefied petroleum gas, and any other fuel authorized in the SSM plan) during periods of startup and shutdown,
2. A requirement to follow an approved SSM plan during periods of SSM, and
3. The current AWFCO system requirements.

U.S. EPA is proposing that all facilities must comply with the SSM work practice standards within 180 days after promulgation of the final rule or upon initial startup, whichever is later. Facilities will need to get their SSM Plans approved to comply with these proposed provisions.

Electronic Reporting Procedures

U.S. EPA proposed some provisions for electronic reporting for the HWC NESHAP in July 2024. After considering the comments received on that proposal, U.S. EPA is reproposing the same provisions for electronic reporting in addition to proposing requirements for the use of a template for certain reports. For more information on previous proposed amendments, please see ALL4’s blog here. U.S. EPA is proposing that electronic reporting requirements take effect 90 days after the publication date of the final rule and that the new reporting templates be required within one year from the date of the final rule or the date the template becomes available on the Compliance and Emissions Data Reporting Interface (CEDRI).

Title V Permits for Area Sources

Currently, the HWC NESHAP requires that all sources subject to the rule must obtain and maintain a Title V Air Permit. Title V permits do not replace Resources Conservation and Recovery Act (RCRA) permits for HWCs, as they are required to obtain and maintain both RCRA and Title V permits. However, the Administrator has the discretion under Clean Air Act (CAA) Section 502(a) to exempt area sources from the requirements of Title V. U.S. EPA has proposed that if the state exempts an area source from the requirements to have a Title V permit, the RCRA permit would need to be modified to include air emissions requirements before the Title V permit for the area source is cancelled or allowed to expire.

Conclusion

The air quality requirements for HWC are complex but ALL4 has experience with them and we can help with permitting, monitoring, testing, and compliance. We will keep an eye out for the final rule (due to be signed by May 29, 2026) and evaluate changes between proposal and promulgation. If you have any questions on the proposed revisions or need assistance with planning for or implementing these new requirements, please reach out to either your ALL4 Project Manager or Peyton Rodgers at prodgers@all4inc.com.