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The Boiler MACT rule establishes national emission standards for hazardous air pollutants (HAPs) emitted by industrial, commercial and institutional boilers and process heaters. The new standards pertain to boilers with a heat-input capacity of greater than 10 MMBTU per hour.

The Boiler MACT rule is divided into two categories: major sources and area sources. A major source is any facility that emits 10 tons per year (tpy) or more of any single HAP or 25 tpy or more of any combination of HAPs. An area source, meanwhile, is a facility that emits less.

Emission limits are based on subcategories of new or existing boilers (status), boiler types and fuel types. Emission limits are established for the following HAPs:

  • Particulate matter (PM) – surrogate for non-mercury metal HAPs
  • Carbon monoxide (CO) – surrogate for non-dioxin organic HAPs
  • Hydrogen chloride (HCl) – surrogate for acid-gas HAPs
  • Mercury (Hg)

The table below shows emission limits based on your existing boiler’s fuel subcategory and boiler type:

SUBCATEGORY: FUELPM (lb/MMBtu)HCI (lb/MMBtu)Hg (lb/MMBtu)CO (ppm @ 3% O2)
Coal Stoker 0.040 0.022 5.7E-06 160
Coal Fluidized Bed 0.040 0.022 5.7E-06 230
Pulverized Coal 0.040 0.022 5.7E-06 130
Biomass Wet Stoker 0.037 0.022 5.7E-06 1,500
Biomass Fluidized Bed 0.11 0.022 5.7E-06 470
Biomass Suspension Burner 0.051 0.022 5.7E-06 2,400
Biomass Dutch Oven 0.28 0.022 5.7E-06 1,100
Biomass Fuel Cells 0.020 0.022 5.7E-06 270
Liquid (Various Types) 0.0011–0.27 0.0009 2.0E-06 130
Gas (Other Process Gases) 0.0067 0.0017 7.9E-06 130

Visit the EPA website for more information on the Boiler MACT rules and how they pertain to your facility.