EPA Puts Forth Reconsidered Boiler MACT Rule

Rules proposed by the U.S. Environmental Protection Agency (EPA) that could require operators of new and existing boilers burning coal, oil, natural gas, and biomass to install a “maximum achievable control technology (MACT)” and limit air pollutants were revised on Friday to offer more flexibility.

More than 1.5 million boilers are operational in the U.S. Nearly 86% of these would be exempt from the rule because they burn natural gas at area source facilities and emit little pollution. For about 13% of the boilers, the EPA’s standards would “continue to rely on practical, cost-effective work practice standards to reduce emissions,” the agency said. And for the highest emitting 0.4% of all boilers in the U.S., the EPA is proposing more targeted revised emissions limits that will provide “industry practical, protective, cost-effective options to meet the standards.”

Existing boilers would have three years to comply with the standards and could obtain an extra year beyond that, if technology cannot be installed in time. But existing incinerators would need to comply no later than three years after the EPA approved a state plan or five years after the publication date, whichever is earlier.

The agency has received a hardline pushback from Republican lawmakers, the energy sector, and states on a number of final and proposed rules released this year, which they say will wreck an already ailing economy. On Friday, the EPA stressed it had “worked throughout this reconsideration process to fully consider all of the information provided to the agency. Based on its review of this information, the agency is proposing to establish standards that are achievable, protective and cost-effective.”

Among changes to the rules are that while only 2% of area source boilers will now be required to meet emissions limits, though the EPA will continue to require work-practice standards, which include maintenance and tune-ups for 98% of area source boilers. To increase flexibility for these sources, the EPA has also proposed to create additional subcategories and require initial compliance tune-ups after two years instead after the first year, to give facilities ample time to comply with the standards. Seasonal Use Area Source Units will be required to conduct tune-ups every five years instead of every other year.

Of the 14,000 major source boilers in the U.S., 88% would be required to conduct “periodic tune-ups,” and the remaining 12% will be required to take steps to meet emission standards if they do not already meet standards.

Other changes include:

  • The creation of new subcategories for light and heavy industrial liquids to reflect design differences in the boilers that burn these fuels.
  • New emissions limits for particulate matter that are different for each solid fuel subcategory (e.g., biomass, coal) to “better reflect real-world operating conditions.”
  • New emissions limits for carbon monoxide based on newly submitted data that shows CO emissions from boilers vary greatly.
  • Increased flexibility in compliance monitoring to remove continuous emissions monitoring requirements for particle pollution for biomass units and to propose carbon monoxide limits that are based on either stack testing or continuous monitoring.
  • Allowing units to continue burning “clean gases” to qualify for work practice standards instead of numeric emissions limits, maintaining flexibility and achievability.

A Reconsideration of a Final Rule
The EPA’s latest proposal is a reconsideration of the final rule that was adopted in February and published March 21, 2011—the same day the EPA pledged to reconsider the rules. The first Industrial Boiler MACT rule, adopted in 2005, was vacated by the U.S. Circuit Court of Appeals for the D.C. Circuit in 2007, leading to a re-proposal of the rule on June 4, 2010.

Industry pushback against that rule, and claims that limits set by the 2010 rule were unachievable, prompted the EPA to relax the rule. But a court-ordered consent decree required the EPA to publish the final rule at the beginning of this year, forcing the agency to sign the final rule in February. However, the EPA promised to reconsider the rules because “certain issues of central relevance” arose after the period of public comment.

Essentially, the rules are developed under sections 112 and 129 of the Clean Air Act, which require the EPA to set technology-based standards for toxic air pollutants that are reflective of levels achieved by the “best performing existing sources,” the agency added.

“EPA’s boiler proposals recognize the diverse and complex range of uses and fuels and tailors standards to reflect the real world operating conditions of specific types of boilers,” the agency said. Rules applying to commercial and industrial solid waste incinerators (CISWI) were also revised to recognize “the important relationship to the Non-Hazardous Secondary Materials (NHSM) rule, which defines solid waste for purposes of the air rules. The NHSM rule helps categorize units as either boilers or CISWI units.”

The revised rules are open for comment for 60 days after publication in the Federal Register.

Good News and Bad News
The revisions the EPA has proposed will likely “represent a mix of good and bad news for industry,” blogged Carroll "Mack" W. McGuffey III, an environmental lawyer for legal firm Troutman Sanders.

The new proposed rule contains “a new suite [of] hazardous air pollutant emission limits that is entirely different from all prior versions of the rule,” he wrote. “Still exempt from those numeric emission limits are natural gas units, units with a heat input capacity of less than 10 mmBtu/hr, and ‘limited use’ units that operate less than 876 hours per year, but all other boilers now face a new set of emissions limitations, some that became more stringent, others that became less stringent.”
The most significant change is a numeric emission limit for dioxins/furans. In the preamble to the reconsideration rule proposal, the EPA recognized that 55% of the dioxin/furan data it has obtained is below detection limits and conceded that almost all of the data is below the limit at which measurements are expected to be reliably accurate, said McGuffey. “To avoid requiring source owners to demonstrate compliance with an emission limit at a level that cannot be accurately measured with existing technology, EPA chose instead to impose work practice standards to minimize dioxin/furan emissions, which consist of a periodic tune-up to ensure good combustion is achieved and maintained.”
However, the rule continues to strictly limit four other pollutants covered by the MACT rule, including mercury, hydrogen chloride (HCl), particulate matter (PM), and carbon monoxide (CO). Mercury and HCl are “fuel-based” pollutants, he pointed out. Since the emissions of those pollutants are driven primarily by the pollutant content of the fuel, the EPA has proposed one mercury limit and one HCl limit each for solid fuels and liquid fuels, without distinguishing between boiler technologies.
“The revised emission limits EPA has proposed do not exhibit any clear trend or pattern,” McGuffey added. “The new limits are based on a different set of data than previous boiler MACT rules—EPA received additional data after the March 2011 final rule and also conducted an additional quality assurance review to eliminate poor quality data.”

The result is a completely different set of limits, “many of which are as stringent as ever,” he wrote. “For example, most of the [mercury] and CO emission limits proposed in EPA’s reconsideration rule are actually more stringent than the March 2011 version of the rule. The PM limits, on the other hand, are less stringent for most categories except some biomass stokers.”
Sources: POWERnews, EPA, Troutman Sanders

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