On July 8, 2020, EPA pre-published a proposed rule to amend the NESHAP for Industrial, Commercial, and Institutional Boilers and Process Heaters (Boiler MACT) in response to three remands issued by the D.C. Circuit—two in 2016 in U.S. Sugar Corp. v. EPA, 830 F.3d 579 (D.C. Cir. 2016) and one in 2018 in Sierra Club, et al. v. EPA, 884 F.3d 1185 (D.C. Cir. 2018). Based on the proposal, EPA’s effort to comply with those decisions will make 28 emission limits more stringent than they were before, many only marginally so, but some by more than an order of magnitude.

In the first remand in U.S. Sugar Corp., the court found that EPA’s January 2013 final rule amendments improperly excluded certain sources from its MACT floor emission limits calculations. The court held that if a source is included in a subcategory, then EPA must consider that source in establishing the MACT floor. Specifically, EPA used a threshold of 10 percent to define its fuel-based subcategories, but then only considered facilities using 90 percent of each fuel to establish the standards. That approach left sources using less than 90 percent of a fuel out of the standard-setting calculation, but nevertheless covered by the standard subcategory-defining fuel to define each subcategory, the MACT floor analysis used a 90-percent fuel threshold.

As a result of the court’s finding, EPA is now proposing to revise the MACT floor emission limits for certain subcategories. Specifically, the rule proposes to revise 34 of 90 emission limits for particular types of new and existing boilers and process heaters—making 28 more stringent, while six would become less stringent. A summary of the affected subcategory, pollutant, and proposed emission limit changes are provided in Table 6 at page 59 of the pre-published rule. Facilities will have up to three years after the effective date of the rule to demonstrate compliance with the new emission limits and, in the meantime, must continue to comply with the 2015 rule. EPA stated that it is proposing the three-year allowance to allow facilities time to install additional controls or monitoring equipment to meet the more stringent emission limits, or modify the method of compliance.

In U.S. Sugar Corp., the court also remanded for further explanation EPA’s use of CO as a surrogate for non-dioxin organic HAP to address the potential availability of post-combustion control technologies. In the proposed rule, EPA explains that between combustion devices and recovery technologies, the former are the more commonly applied control device because of its high removal efficiencies of most types of organic vapor HAPs, and its effectiveness does not depend on the organic HAP stream makeup or the organic HAP concentration. Additionally, in Sierra Club, the court remanded to EPA for further explanation of its decision to set a CO limit of 130 ppm as a minimum standard representing MACT for organic HAPs for certain subcategories. The proposed rule explains that in addition to the data used in the 2013 rule to establish the 130 ppm threshold, two other studies, including an EPA MATS study, provide additional support for the 130 ppm minimum standard.

The proposed rule is expected to result in nationwide emission reductions of selected HAPs (i.e., HCl, hydrogen fluoride, Hg, metals) by an additional 37.35 tpy as compared with the current rule. Additionally, the total annualized capital costs of the proposed amendments is $22 million in 2016 dollars, which include costs for control devices, monitoring and testing associated with the proposed changes to the emission limits.

Source categories potentially affected by the propose rule include, but are not limited to, boilers or process heaters used in:

  • Extractors of crude petroleum and natural gas;
  • Manufacturers of lumber and wood products;
  • Pulp and paper mills;
  • Chemical manufacturers;
  • Petroleum refineries, and manufacturers of coal products;
  • Manufacturers of rubber and miscellaneous plastic products;
  • Steel works and blast furnaces;
  • Electroplating, plating, polishing, anodizing, and coloring;
  • Manufacturers of motor vehicle parts and accessories;
  • Electric, gas, and sanitary services;
  • Health services; and
  • Educational services.

EPA will receive comments on the proposed rule for 60 days after publication in the Federal Register.