October 13, 2023

NSPS Updates for Electric Arc Furnaces

On August 25, 2023, EPA finalized a three-part rule updating the new source performance standards for electric arc furnaces and argon-oxygen decarburization vessels. [88 FR 58442]The rule provides minor updates for sources subject to Part 60, Subparts AA and AAa, while creating a new Subpart AAb for sources that commenced construction, reconstruction, or modification after May 16, 2022. These rules, which control particulate matter (PM) emissions from affected facilities and set opacity limits, are part of the agency’s standard periodic NSPS review efforts. In total, 88 electric arc furnaces throughout the United States are expected to be impacted by this rule.

Changes to Subparts AA and AAa

Subpart AA applies to electric arc furnaces and dust-handling systems that commenced construction, modification, or reconstruction after October 21, 1974, and on or before August 17, 1983 in steel plants that produce carbon, alloy, or specialty steels. Subpart AAa is similar but also regulates argon-oxygen decarburization vessels at steel plants, and the applicability date range is from August 17, 1983 through May 16, 2022. Changes to these standards are limited to added definitions, specified performance test methods, slightly more stringent monitoring requirements, and removing an inclement weather provision tied to performance testing. As with most of the agency’s technical updates to the stationary source programs, electronic reporting is now required through the Compliance and Emissions Data Reporting Interface (CEDRI) accessible via EPA’s Central Data Exchange. The startup, shutdown, and malfunction exemption of §60.11(c) has not been removed and is still available to sources.

New Subpart AAb

New Subpart AAb reflects the best system of emission reduction for a PM capture system, setting the emission rate at 79 mg/kg steel produced rather than the old 12 mg/dry standard cubic meter. The opacity limit has been reduced from 6% to 0% during melting and refining operations, and the 20%/40% opacity allowances during charging/tapping operations have been removed. Compliance testing every five years has been added along with electronic reporting requirements. Unlike Subparts AA and AAa, Subpart AAb does not have the startup, shutdown, and malfunction exemption in light of Sierra Club vs. EPA (U.S. Court of Appeals, D.C. Circuit; Docket No. 02-1135; December 19, 2008).

Compliance dates

This final rule is effective August 25, 2023. Affected sources that commence construction, reconstruction, or modification after May 16, 2022, must comply with all Subpart AAb requirements no later than August 25, 2023, or upon startup, whichever is later. Affected sources subject to Subparts AA or AAa must comply with the new changes by February 21, 2024.


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This document addresses issues of a general nature related to the federal environmental regulations. Persons evaluating specific circumstances dealing with the environmental regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.