EPA’s Proposed Revisions to Emission Limits for Boiler MACT

On January 31, 2013, the U.S. Environmental Protection Agency (EPA) finalized amendments to the national emission standards (NESHAP) for the control of hazardous air pollutants (HAP) at major sources from new and existing industrial, commercial, and institutional (ICI) boilers and process heaters (Boiler MACT). Subsequently, the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit), in a decision issued in July 2016, remanded several of the emission standards to the EPA based on the court’s review of the EPA’s approach to setting those standards. In response to these remands, this action proposes to amend several numeric emission limits for new and existing boilers and process heaters consistent with the court’s opinion and set compliance dates for these new emission limits.

Based on all of the revisions made to address the remand related to ranking and assessing the subcategories, there are 34 different emission limits EPA proposes to change. The changes in the limits are listed in the following table:


Subcategory Pollutant Current emission limit (lb/MMBtu of heat input or ppm at 3-percent oxygen for CO) Proposed emission limit (lb/MMBtu of heat input or ppm at 3-percent oxygen for CO)
New-Solid HCl 2.2E–02 3.0E–04
New-Dry Biomass Stoker TSM8 4.0E–03 5.0E–03
New-Biomass Fluidized Bed CO 230 130
New-Biomass Fluidized Bed PM (TSM) 9.8E–03 (8.3E–05) 4.1E–03 (8.4E–06)
New-Biomass Suspension Burner CO 2,400 220
New-Biomass Suspension Burner TSM 6.5E–03 8.0E–03
New-Biomass Hybrid Suspension Grate CO 1,100 180
New-Biomass Dutch Oven/Pile Burner PM 3.2E–03 2.5E–03
New-Biomass Fuel Cell PM 2.0E–02 1.1E–02
New-Wet Biomass Stoker CO 620 590
New-Wet Biomass Stoker PM 0.03 0.013
New-Liquid HCl 4.4E–04 7.0E–05
New-Heavy Liquid PM (TSM) 1.3E–02 (7.5E–05) 1.9E–03 (6.4E–06)
New-Process Gas PM 6.7E–03 7.3E–03
Existing-Solid HCl 2.2E–02 2.0E–02
Existing-Solid Hg 5.7E–06 5.4E–06
Existing-Coal PM 4.0E–02 3.9E–02
Existing-Coal Stoker CO 160 150
Existing-Dry Biomass Stoker TSM 4.0E–03 5.0E–03
Existing-Wet Biomass Stoker CO 1,500 1,100
Existing-Wet Biomass Stoker PM (TSM) 3.7E–02 (2.4E–04) 3.4E–02 (2.0E–04)
Existing-Biomass Fluidized Bed CO 470 210
Existing-Biomass Fluidized Bed PM (TSM) 1.1E–01 (1.2E–03) 2.1E–02 (6.4E–05)
Existing-Biomass Suspension Burners PM (TSM) 5.1E–02 (6.5E–03) 4.1E–02 (8.0E–03)
Existing-Biomass Dutch Oven/Pile Burner PM 2.8E–01 1.8E–01
Existing-Liquid Hg 2.0E–06 7.3E–07
Existing-Heavy Liquid PM 6.2E–02 5.9E–02
Existing-Non-Continental Liquid PM 2.7E–01 2.2E–01
Existing-Process Gas PM 6.7E–03 7.3E–03

The EPA requests comment on the revisions to the emission limits in light of the changes the EPA has proposed in response to the remand. Broader comments with respect to the Upper Prediction Limit (UPL) calculation methodology will not be considered within the scope of this rulemaking. The EPA will only consider data that is already available in the rulemaking record. The EPA also requests comments on its determination of beyond-the-floor emission limits for certain subcategories. The emission reduction impacts associated with these changes to the MACT floor emission limits are discussed in the docketed memorandum Revised (2019) Methodology for Estimating Impacts for Industrial, Commercial, Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants. The EPA is proposing that facilities have up to 3 years after the effective date of the final rule to comply with the new emissions limits in the final rule. Before this date, facilities must continue to comply with the rule as it was finalized in 2015. This allowance is being made considering that some facilities may require additional add-on controls or monitoring equipment to be designed, purchased, and installed in order to meet the more stringent emission limits, or to modify the method of compliance based on the changes in emission limits. In addition, units will require lead time to prepare and execute their testing plans to demonstrate compliance with the updated emission limits and to update reports to incorporate the revised emission limits. The EPA requests comment on or before October 23, 2020.

The link to the Federal Register addressing the above is: https://www.govinfo.gov/content/pkg/FR-2020-08-24/pdf/2020-15121.pdf

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