EPA Finalizes "Boiler MACT" Hazardous Air Emissions Rules

March 11, 2011

On February 23, 2011, EPA released its final rules regulating emissions of hazardous air emissions from industrial, commercial and institutional boilers and process heaters. One of the rules sets numeric emissions limits for mercury, dioxins, particulate matter, hydrogen chloride, and carbon monoxide for 15 different subcategories of major source boilers and process heaters. A "major source" facility emits or has the potential to emit more than 10 tons per year or any single air toxic or 25 tons per year of any combination of air toxics. EPA estimates that there are 13,840 existing major source boilers and process heaters in the US, with another 47 new units anticipated to be built in the next three years.

In addition to the numeric emission limits noted above, the major source rule includes the following requirements:

  • Monitoring to assure compliance with emission limits. Continuous emissions monitoring for particulates is required for the largest major source boilers, as a surrogate for toxic metals such as lead and chromium. In addition, all units larger than 10MMBtu/hr must monitor oxygen as a measure of good combustion.
  • For all new and exiting units smaller than 10MMBtu/hr, and all new and existing natural gas and refinery gas-fired units, the rule establishes work practice standards in lieu of emissions limits, including a requirement to perform a tune-up for each unit every two years (for units under 10MMBtu/hr) or annually (for gas-fired units).
  • Existing major source facilities must conduct one-time energy assessments to identify cost-effective energy conservation measures.

In addition to the major source rule, EPA published a final rule covering "area sources"--those that emit less than 10 tons per year of any single air toxic or 25 tons per year of any combination of air toxics. The area source rule includes the following requirements:

  • New coal-fired boilers larger than 10MMBtu/hr will be subject to numeric emissions limits for mercury, particulate matter, and carbon monoxide, while existing units will be subject to limits for mercury and carbon monoxide.
  • New biomass or oil-fired units larger than 10MMBtu/hr will be subject to limits for particulate matter, while existing units will be required to employ work practices, including maintenance every two years.
  • New boilers smaller than 10MMBtu/hr will be subject to a biannual routine maintenance requirement in lieu of numeric emissions limits.

It is anticipated that the new rules will cause many facilities to switch from coal to natural gas to avoid having to install potentially costly emissions control devices. Although EPA was under a court order to finalize the rules by February 21, 2011, it also released a notice of reconsideration, stating that it will reconsider additional subcategories for large industrial boilers, establishing work practice standards for major source boilers that have limited use, revisions to the carbon monoxide monitoring requirements for both incinerators and boilers, and setting particulate matter emissions limits under less stringent, generally available control technology standards for small oil-fired boilers.