New boiler MACT and affiliated rules proposed


Courtesy of Trinity Consultants

EPA proposed three related rules (with final rules expected by December 16, 2010), intended to reduce the emission of hazardous air pollutants (HAPs) from industrial, commercial, and institutional boilers and process heaters as well as commercial and industrial solid waste incinerators. Simultaneously, it also proposed a definition of solid waste that could potentially affect some units currently considered boilers, by moving them into the category of solid waste incinerators. These actions replace the national emission standards for new and existing boilers and process heaters that was previously promulgated in 2004 and vacated by the court in 2007. The newly proposed rules include:
  • National Emission Standards for Hazardous Air Pollutants for Major Sources: Industrial, Commercial, and Institutional Boilers and Process Heaters (Boiler MACT)
  • National Emission Standards for Hazardous Air Pollutants for Area Sources: Industrial, Commercial, and Institutional Boilers and Process Heaters (Area Source Boiler MACT)
  • Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Commercial and Industrial Solid Waste Incineration Units (CISWI Rule)

Major Source Boiler MACT

The major source Boiler MACT, which targets numerous HAPs including mercury, other metals, and organic air toxics, affects boilers that burn natural gas, fuel oil, coal, biomass, refinery gas, or other gas, as well as process heaters, for a total of 11 subcategories. New and existing natural gas- and refinery gas-fired units > 10 MMBtu/hr would be subject to a work practice standard consisting of annual tune-ups. Existing units with a heat input capacity < 10 MMBtu/hr, would be subject to a work practice standard consisting of tune-ups every two years. Other affected sources would be subject to emission limits for mercury, dioxin, particulate matter, hydrogen chloride (as a surrogate for acid gases), and carbon monoxide (as a surrogate for non-dioxin organic air toxics). EPA estimates that 13,555 boilers and process heaters at major sources and 46 new units would be affected over the next three years. Key aspects of the rule are summarized below.


  • Emission limits apply at all times (no startup or shutdown exclusions)
  • Emissions standards for dioxins/furans have been proposed and the total select metals (TSM) compliance alternative (in the original MACT standards) would not be available
  • Emissions standards have been proposed for existing liquid-fired boilers of 10 mmBtu/hr or greater

Compliance / Notification

  • Compliance date for existing sources is three years after publication of the final rule in the Federal Register
  • Notification of Compliance Status is required 180 days after rule compliance date and performance tests are required 60 days following test


  • Site-specific monitoring plans are required
  • Work practice standards, rather than emissions standards, would apply to natural gas/refinery gas units
  • A one-time energy assessment of cost-effective energy conservation measures would be required for affected units
  • Annual stack testing is required for each regulated pollutant (except for hydrogen chloride and/or mercury if the fuel analysis option is utilized)
  • Stack testing can be reduced to once every three years if test results for three consecutive years show emissions at less than 75% of standard; does not apply to dioxin/furan testing
  • Reporting of annual stack test results would be required using an EPA web-based electronic reporting tool (ERT)
  • Continuous emissions monitoring systems (CEMS) would be required for CO for units > 100 MMBtu/hr and for particulate matter for units > 250 MMBtu/hr

Area Source Boiler MACT

The newly proposed Area Source Boiler MACT, affecting facilities with the potential to emit < 10 tons per year (tpy) of any single air toxic and < 25 tpy of combined air toxics, will affect boilers that burn coal, oil, or biomass, or non-waste materials, but not solid waste. It includes standards to limit emissions of mercury, particulate matter (as a surrogate for non-mercury metals) and carbon monoxide (as a surrogate for organic air toxics), depending on new/existing status and fuel type. Existing small boilers would not be subject to emission limits but would be required to perform a boiler tune-up every two years. EPA estimates that approximate 183,000 existing area source boilers at 92,000 U.S. facilities and approximately 6,800 new areas source boilers over the next three years would be affected.


Under the proposed CISWI Rule, five subcategories of devices that burn solid waste at a commercial or industrial facility (other than municipal solid waste incinerators) will be subject to emission limits for nine pollutants—mercury, lead, cadmium, HCl, PM, CO, dioxins/furans, nitrogen oxides, and sulfur dioxides—unless using an alternative waste disposal option. In addition to emission limits, an estimated 176 existing affected sources could be subject to stack testing, monitoring, annual inspections, visible emissions testing,and test data handling requirements. Under the proposed solid waste definition, EPA expects that some sources previously subject to the Boiler MACT would now come under the CISWI Rule.

EPA will accept comments on the proposed rules for 45 days after their publication in the Federal Register. Sources subject to these rules will need to address notification requirements, work practice standards, permitting issues, and the development of required plans.

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