On April 29, 2010, EPA issued its long-awaited proposal for a new Maximum Achievable Control Technology (MACT) standard for industrial boilers.  The rule, if finalized as proposed, will impose stringent emission limits and monitoring requirements on over 10,000 existing fossil fuel-fired and biomass-fired boilers by the end of 2013, and on any new boilers constructed after the rule becomes final.

The proposed rule is intended to replace the rule vacated in 2007 by the U.S. Court of Appeals for the D.C. Circuit.  The D.C. Circuit vacated EPA’s original 2004 industrial boiler MACT because it failed to properly distinguish “industrial boilers” from “solid waste incinerators,” which must be regulated under separate sections of the Clean Air Act.  To address the court’s concern, EPA actually issued three proposed rules: (1) a new MACT for “industrial commercial and institutional boilers and process heaters” (ICI Boilers); (2) a revised MACT for “commercial and industrial solid waste incinerators” (CISWIs); and (3) a revision to the definition of the term “solid waste” to help distinguish between the two.

The definition of “solid waste” is critical to the distinction between an ICI Boiler and a CISWI because the Clean Air Act requires EPA to regulate as an incinerator “any facility which combusts any solid waste.”  The relevant definition of “solid waste” is actually found in the Resource Conservation and Recovery Act (RCRA), not the Clean Air Act, and as currently written covers “any discarded material.”  EPA’s proposal seeks to clarify whether “solid waste” includes certain non-hazardous “secondary materials” – materials that are not the primary product of a manufacturing or commercial process that may be discarded at some point but later reused as fuel or ingredients in another process.  EPA’s proposed rule would exclude “secondary materials” from the definition of “solid waste” if they are either combusted by the generator, used as ingredients in another manufacturing process, or “processed” into a fuel or an ingredient.  The materials must also either meet certain “legitimacy criteria” that confirm that the use of the material is not a “sham” for disposal, or submit a petition to EPA for a “non-waste determination.”

Perhaps just as important as the specific exemptions in the proposed rule are the statements in EPA’s preamble that confirm “traditional fuels” are not solid waste.  According to EPA, “traditional fuels” include not only fossil fuels, but also “clean cellulosic biomass,” which EPA described as “materials that have not been altered (either chemically or through some type of production process), such that it contains contaminants at concentrations normally associated with virgin biomass materials.”  EPA provided a long list of such “clean cellulosic biomass” that would qualify as a “traditional fuel” instead of solid waste, including:

[F]orest-derived biomass (e.g., green wood, forest thinnings, clean and unadulterated bark, sawdust, trim, and tree harvesting residuals from logging and sawmill materials), corn stover and other biomass crops used specifically for energy production (e.g., energy cane, other fast growing grasses), bagasse and other crop residues (e.g., peanut shells), wood collected from forest fire clearance activities, trees and clean wood found in disaster debris, and clean biomass from land clearing operations.

With these statements, EPA confirmed that boilers that combust clean, unaltered biomass should be treated as an ICI Boiler, not as a CISWI, essentially achieving the same result that EPA initially sought in its original 2004 industrial boiler MACT rule.

The ICI Boiler MACT itself applies to all boilers that are a major source of hazardous air pollutant (HAP) emissions (greater than 10 tons per year of one, or greater than 25 tons per year of all HAPs) and establishes very stringent emissions standards for eleven subcategories of boilers based on fuel and process type.  The rule addresses HAPs emissions by imposing limits on five “surrogate” pollutants, namely mercury (Hg), hydrogen chloride (HCl), particulate matter (PM), carbon monoxide (CO), and dioxins/furans (D/F).  According to EPA, controlling these five pollutants will ensure that emissions of all HAPs are minimized.  Sources above a certain size must install continuous emission monitors for both PM and CO to demonstrate compliance with the PM and CO limits, but compliance with the other emission limits may be demonstrated through fuel analyses, performance tests, and parametric monitoring.

For existing units, the limits are based on the average emission rate of the top 12 percent of the best performing boilers, based on data EPA recently collected from numerous boiler owners.  Existing facilities must meet the limits within three years, and may do so with any combination of controls, but EPA expects that most facilities will likely need to install baghouses, carbon injection systems, scrubbers, oxidation catalysts, and new burners to comply.  New sources will be required to comply with even more stringent emission requirements, given that the Clean Air Act requires new HAP sources to match the emission levels of the single best performing source in the country. 

Boilers that continue to combust “any solid waste,” even under EPA’s new definition of “solid waste,” will be regulated as a CISWI under Section 129 of the Clean Air Act.  That section requires EPA to adopt emission limits not only for the five pollutants listed above, but also for sulfur dioxide, nitrogen oxides, lead, and cadmium.  EPA first promulgated a CISWI MACT in 2000 and revised that standard in 2005 with a new definitions section.  The D.C. Circuit vacated the 2005 revision along with the ICI Boiler MACT, but the court did not vacate the entire CISWI MACT itself.  As a result, the CISWI MACT still remains in effect, and EPA’s proposed rule primarily seeks to address the portion of the rule that was vacated by the D.C. Circuit.  However, the proposal also subcategorizes CISWIs into five categories and lowers the required emission limits for some of them.   

EPA will accept comments on these three proposals for 45 days following the publication of them in the Federal Register, which is expected in the next few days, and EPA plans to issue the final rules on December 16, 2010.