On December 23, 2011, U.S. EPA promulgated proposed amendments and revisions to the reconsidered National Emission Standards for Hazardous Air Pollutants (NESHAP) for industrial, commercial, and institutional boilers and process heaters at both major and area sources of hazardous air pollutants (HAP) emissions. EPA developed separate rules for units at major sources of HAP emissions (greater than 10 tons per year [tpy] of any single HAP and/or greater than 25 tpy of total HAP) and area sources of HAP emissions (less than 10 tpy/25 tpy). The Maximum Achievable Control Technology (MACT) standards for units at major sources are found in 40 CFR 63 Subpart DDDDD, while the Generally Available Control Technology (GACT)/MACT standards for units at area sources are found in 40 CFR 63 Subpart JJJJJJ.
These recent changes were made to final rules that were promulgated on March 21, 2011 for both source categories. Concurrent with the promulgation of the final rules, EPA published a notice of reconsideration. On May 18, 2011, EPA stayed the effective date of the major source Boiler MACT until judicial review of the rule is completed or the reconsidered rule is finalized, whichever is earlier. EPA stayed the major source Boiler MACT rule to ensure that the emission limits are based on the best available data and to ensure the public is given ample opportunity to provide additional input. EPA was aware that stakeholders wanted the opportunity to submit additional data to help EPA meet its objectives for the reconsidered rules and the December 2011 reconsidered rules incorporate this additional information. To further complicate matters, the U.S. District Court of Appeals vacated the stay on January 9, 2012. With the stay vacated, the compliance dates in the final rule promulgated in March of 2011 (i.e., March 21, 2014 for existing sources and May 20, 2011 for new or reconstructed sources) become effective pending additional litigation or action by EPA. This would significantly reduce the time for compliance for existing facilities.
This rulemaking, like previous rulemakings, was promulgated along with the Nonhazardous Secondary Material (NHSM) and Commercial and Industrial Solid Waste Incineration (CISWI) rules in EPA’s latest attempt to finalize rules for various types of combustion units. Additional articles on the two related rulemakings on CISWI and NHSM are included in this issue.
Major Source Boiler MACT
The major source rule, known as the Boiler MACT, affects boilers and process heaters that burn coal, biomass, and other non-waste solid fuels, liquid fuels, and natural gas, refinery gas, or other gaseous fuels. The affected sources for the rule continue to be the collection of existing and each new or reconstructed industrial, commercial, and institutional boilers and process heaters that do not burn solid waste at major sources of HAP emissions. The basic framework for the regulation remains the same. Departures from the March 21, 2011 rule are highlighted in the following sections.
The compliance date for new sources will be 60 days after the final rule is published in the Federal Register (expected in mid-2012), or upon startup, whichever is later. The compliance date for existing sources is three years after the date the final rule is published in the Federal Register. The date after which units are considered new or reconstructed units under the rule remains June 4, 2010. A boiler or process heater is classified as existing if it is not new or reconstructed.
The HAP categories targeted by the rule remain unchanged from the proposed rule and include mercury (Hg), non-mercury metal HAPs, non-dioxin organic HAP, non-metal inorganic HAP, and dioxin/furans. While hydrogen chloride (HCl), particulate matter (PM), and carbon monoxide (CO) remain surrogates for non-metal inorganic HAP, metal HAP, and non-dioxin organic HAP, respectively, EPA proposed total select metals (TSM) as an optional surrogate for metal HAP for solid fuel and Gas 2 units. TSM is defined as the combination of arsenic, beryllium, cadmium, chromium, lead, manganese, nickel and selenium. Emissions averaging is not a compliance option for TSM.
In the March 21, 2011 rule, EPA proposed different subcategories depending on the fuel fired and the boiler design when establishing emission limits. In contrast to the March 21, 2011 rule, EPA has designated PM as a combustion-based pollutant as a result of comments received from petitioners. The designations are contained in the proposed rule and EPA is proposing 17 subcategories. Major changes from the March 21, 2011 rule subcategories including:
- Splitting the biomass stoker subcategory into wet stoker and kiln dried subcategories
- Splitting the suspension burner and Dutch oven subcategory into separate subcategories and including pile burners in the Dutch oven subcategory
- Splitting the liquid fuel subcategory into light liquid and heavy liquid subcategories
The following revised definitions were proposed based on the new subcategories:
- Light liquid includes distillate oil, biodiesel and vegetable oil
- Heavy liquid includes residual oil and any other liquid fuel not classified as a light liquid
- Hydrogen sulfide concentration limits were removed from the definition of other Gas 1 fuel (mercury concentration limits remain)
EPA proposed an alternate emission limit for units subject to a CO emission limit that elect to install and operate a continuous emissions monitoring system (CEMS) for CO. Compliance is demonstrated using a CO CEMS based on a 10-day rolling average for solid fuel and heavy liquid-fired units. Units that burn light liquids and liquid fuel fired units in non-continental areas are subject to 1-day block and 3-hour rolling averages, respectively.
EPA incorporated additional emission information received during the comment period in developing the revised emission limits. The emission limits in the March 21, 2011 and re-proposed rules are summarized in Table 1 for new sources and Table 2 for existing sources. These emission limits apply to new and existing boilers and process heaters with heat input greater than or equal to 10 MMBtu/hr. Unlike the March 21, 2011 rule, there are no numerical emission limits for dioxins/furans in the reconsidered rule for any subcategory. In lieu of numerical limitations, EPA has proposed work practice requirements.
Similar to the March 21, 2011 rule, the standards apply at all times (i.e., including periods of malfunction). The malfunction provisions remain unchanged from the March 21, 2011 rule. In lieu of numerical emission limits, work practice standards apply during periods of startup and shutdown.
EPA included the following definitions of startup and shutdown in the proposed rule. Startup is defined as the period between the state of no combustion to the period where a unit first achieves 25% load. Shutdown is defined as the period that begins when a unit last operates at 25% load and ending with a state of no fuel. The work practice standards for startups and shutdowns are identified as the following steps:
- Employ good combustion practices and demonstrate that good combustion practices are maintained by monitoring oxygen (O2) concentrations and optimizing those concentrations as specified by the boiler manufacturer
- Ensure that boiler operators are trained in startup and shutdown procedures, including maintenance and cleaning, safety, control device startup, and procedures to minimize emissions
- Maintain records during periods of startup and shutdown and include in compliance reports the O2 conditions/data for each event, length of startup/shutdown, and reason for event.
EPA has retained the tune-up work practice standard requirements. As noted previously, the work practice standards replace dioxin/furan emission numerical limits. The frequency of tune-ups is summarized as follows (note that tune-ups can be delayed for a specified period if it would require a unit shutdown):
- Every five (5) years for a new or existing boiler or process heater with heat input capacity of less than 5 MMBtu/hr in any of the following subcategories: unit designed to burn natural gas, refinery gas or other Gas 1 fuels; unit designed to burn Gas 2 (other); or unit designed to burn light liquid
- Every other year (biennially) for: a limited use boiler or process heater; a new or existing boiler or process heater with heat input capacity of less than 10 million Btu per hour in the unit designed to burn heavy liquid or unit designed to burn solid fuel subcategories; a new or existing boiler or process heater with heat input capacity of less than 10 million Btu per hour, but equal to or greater than 5 million Btu per hour, in any of the following subcategories: unit designed to burn natural gas, refinery gas or other Gas 1 fuels; unit designed to burn Gas 2 (other); or unit designed to burn light liquid
- Annually for all other units
The proposed rule maintains the one-time energy assessment requirement for existing units that was included in the March 21, 2011 rule. The proposed rule clarifies the length and scope of the assessment, as well as specifying that the assessment must be completed before the compliance date. Notable scope clarifications include limiting the inventory of major energy systems to affected boilers and process heaters which are under control of the boiler/process heater owner operator.
In the proposed rule, EPA included additional monitoring options for several pollutants and modified the averaging periods used to demonstrate continuous compliance. Compliance with operating parameters (e.g., sorbent injection, scrubber flow rate, scrubber pH, etc.) will be demonstrated based on a 30-day rolling average value, compared to the 12-hour block average in the March 21, 2011 rule. The requirement for an oxygen CEMS in the March 21, 2011 rule was replaced with an oxygen trim system with the oxygen level set at the lowest level recorded during the performance test.
The March 21, 2011 rule had a PM CEMS requirement for coal, biomass and/or residual oil fired boilers or process heaters having an average annual heat input greater than 250 MMBtu/hr. This requirement has been replaced with a PM continuous parameter monitoring system (CPMS) for boilers and process heaters combusting solid fossil fuel and/or residual oil. Biomass is no longer included as a fuel type requiring some sort of continuous monitoring for boilers and process heaters with annual average heat input greater than 250 MMBtu/hr. The PM CPMS basis must be in-stack or extractive light scatter, light scintillation, beta attenuation, or mass accumulation detection of PM in the exhaust gas or representative exhaust gas sample. The reportable measurement output from the PM CPMS may be expressed as milliamps, stack concentration, or other raw data signal. This revision eliminates the certification requirements of CEMS for subject units.
EPA has included the option to demonstrate continuous compliance with the mercury and hydrogen chloride emission limits through the use of CEMS in lieu of fuel sampling, stack testing, and compliance with operating parameters. Compliance with the emission limits will be demonstrated using the 30-day rolling average.
EPA Comment Solicitation
EPA solicited comments on both proposed changes from the March 21, 2011 rule as well as changes that were finalized in the March 21, 2011 rule and remain unchanged in the proposed rule, but on which the public did not have the opportunity to comment. These provisions include, but are not limited to, the following:
- The proposed TSM compliance alternative for solid fuels
- Work practice standards in lieu of numerical emission limits for dioxins/furans
- Revisions to subcategories
- The basis for proposing alternate CO emission limits
- Proposed changes to monitoring requirements (e.g., PM CPMS, oxygen monitoring, CEMS for CO, Hg and HCl, averaging periods)
- Tune-up requirements
- Startup and shutdown work practice requirements
- Energy assessment scope and compliance date
Comments were due on or before February 21, 2012.
Area Source Boiler NESHAP
Although the compliance date for the area source Boiler NESHAP (also called area source Boiler MACT/GACT) was not previously stayed like the major source Boiler MACT rule, EPA proposed several changes and technical corrections to the final rule in this rulemaking. The compliance date for existing boilers (process heaters are not subject to this rule) remains March 21, 2014, as the proposed changes do not affect facilities’ ability to comply with the rule. Like the March 2011 final rule, natural gas fired boilers and hot water heaters are not subject to the proposed amendments to the area source Boiler MACT/GACT rule.
Applicability and Subcategory Clarifications
In the proposed rule, EPA included clarifications of rule applicability and subcategory revisions, which include:
- A new subcategory for seasonally operated boilers, which are boilers that undergo shutdowns for more than 7 consecutive months (or 210 consecutive days) due to seasonal conditions
- An exemption for temporary boilers, defined as any gaseous or liquid fuel boiler designed to, and is capable of, being carried or moved from one location to another by means of, for example, wheels, skids, carrying handles, dollies, trailers, or platforms and meets additional applicability criteria, similar to the major source rule
- Clarification in the definition of natural gas curtailment
Work Practice Requirements
The tune-up requirements, except for the compliance dates, remain the same as the final rule. If an existing affected boiler is subject to a work practice or management practice standard of a tune-up, the facility must comply with the work practice or management standard no later than March 21, 2013, a one-year extension of the compliance date.
In the final rule, EPA required biennial tune-ups for all liquid fired boilers. In the new proposed rule, liquid fired units less than 5 MMBtu/hr (new and existing) and all seasonally operated units (new and existing) must perform a tune-up every five years. Initial tune-ups for new units are required within 25 months or 61 months of startup for units subject to biennial and or five-year tune-ups, respectively.
Similar to the proposed major source rule, the proposed area source rule clarifies the length and scope of the energy assessment. Additionally, the energy assessment must be completed before the compliance date for existing sources (March 21, 2014).
The proposed rule revised mercury and carbon monoxide emissions limits for new and existing coal fired units of all sizes, while the remaining limits are unchanged. Emission limits in the final rule compared to the proposed rule are summarized in Table 3.
Similar to the major source Boiler MACT, the standards apply at all times, with work practice standards for startup and shutdown for new and existing coal, new biomass, and new oil units with a heat input greater than 10 MMBtu/hr. In lieu of numerical emission limits, work practice standards apply during periods of startup and shutdown. The same definitions of startup and shutdown proposed in the major source rule are proposed in the area source rule.
In the proposed area source rule, EPA included the option to install and operate a CO CEMS and continuously monitor oxygen content to demonstrate compliance with the CO emission limits. Compliance with the CO emission limit will be based on the 10-day rolling average CO emission rate. Unlike the major source rule, the same emission limit applies regardless of the compliance demonstration option selected. In the proposed rule, EPA allowed for the use of oxygen trim analyzer systems to monitor oxygen concentration in the boiler. Similar to the major source rule, continuous compliance with operating parameters will be based on a 30-day rolling average. operating parameters will be based on a 30-day rolling average.
EPA has identified several areas where comments are solicited for the area source rule, including, but not limited to:
- Applicability of Title V permitting requirements to area sources
- Establishing standards based on generally available control technology for oil and biomass boilers
- Averaging periods for continuous compliance demonstrations
- Tune-up work practice requirements
- Energy assessment requirements
- Revisions to CO emission limits and monitoring alternatives
Similar to the major source rule, comments were due on or before February 21, 2012.
The evolution of the boiler and process heater rules continues. EPA has targeted mid-2012 for promulgation of the final rules. However, with the D.C. District Court vacating the stay, the compliance dates in the final rule will become effective pending additional litigation. In the interim period, owners and operators should review how the proposed rules impact their facilities and evaluate potential opportunities for submitting comments through trade organizations or separately. Both Boiler MACT and GACT rules have a three-year compliance schedule with the potential for EPA to grant an owner/operator an additional year for compliance. This compliance schedule could be compressed for installing necessary pollution control to achieve compliance. As a result, owners and operators should now be planning for potential pollution control installation by understanding emissions relative to limits (emissions testing may be required), determining reductions needed and evaluating technically feasible control technology options. In addition, we recommend planning for the installation of continuous emission monitoring systems if required. Please contact your local Trinity office to assist in the evaluation of compliance requirements to your facility.