The impact of recently released air emissions regulations has stirred heated debate about forced coal plant closures and the possibility of reduced grid reliability in some regions. Biomass power may be an unexpected beneficiary of the new rules.
On Dec. 23, 2011, the U.S. Environmental Protection Agency (EPA) released proposed changes to the Promulgated Rule of the National Emission Standards for Hazardous Air Pollutants, also referred to as Boiler MACT, for both “Major Source” and “Area Source” facilities. When Boiler MACT was promulgated on Mar. 21, 2011, the EPA recognized some provisions might be too stringent for facilities covered by the regulation. Therefore, the very same day, the agency issued a notice of its intent to reconsider certain provisions of the just-released rule. A formal extension of the effective date of Boiler MACT was announced on May 18, 2011, with a request to the public to supply data to assist the EPA in its reconsideration efforts. Affected industries still have until 2015 to comply with the rule.
The EPA next released the final Mercury and Air Toxics Standards (MATS) on Dec. 21, 2011. Proposed changes to the Cross-State Air Pollution Rule (CSAPR) were released Dec. 23, 2011, and immediately stayed by the U.S. Court of Appeals for the District of Columbia Circuit on Dec. 30, two days before the rule’s effective date.
Unfortunately, the sometimes-heated discussions of MATS and CSAPR and their impact on the reliability of the nation’s power supply have obscured the possibly positive impact of Boiler MACT on biomass plants.
Rules Benefit Biomass
It may surprise you to learn that this increased pressure from the EPA on coal-fired generators (expected to cause 40 GW to 50 GW worth of coal plant closures), coupled with the demand for renewable energy sources, is having an unexpected side effect: It’s making biomass a more attractive power generation alternative. Furthermore, the changes the EPA is expected to make to the Boiler MACT rule will favor biomass power much more than in the earlier version. Those expected improvements are discussed in greater detail later in this article.
The revised Boiler MACT regulation appears to favor biomass power in the impact it has on required emission reduction technologies. As it stands, the promulgated rule will require the addition of multiple emission reduction systems in order to meet pollutant limitations. The proposed regulation removes and reduces many of the limitations, thus the positive impact on the economics of biomass plants.
There are three categories of hazardous air pollutants (HAPs) in the promulgated Boiler MACT rule, under Major Sources, that place new limitations on pollutant emissions from both existing and new biomass facilities: hydrogen chloride, mercury, and dioxins/furans (Table 1).
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| Table 1. Summary of hazardous air pollutants and their limits in the promulgated Boiler MACT rule. Source: EPA |
Determining an uncontrolled emission rate for each of the three HAPs is a major concern with meeting these limitations. Biomass typically does not have consistent characteristics because it is not always procured from the same source. Due to sourcing inconsistencies, environmentally regulated constituents in the fuel may vary greatly. For new biomass plants, there is some consistent data for woody biomass that could be used to produce baseline emissions to estimate reduction percentages. However, for many other biofuels (including switchgrass, corn stover, and miscanthus) there is sparse, if any, information pertaining to the regulated HAPs. Even with the lack of data, control technologies will be required to meet the Boiler MACT requirements.
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