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Maryland Would Add Flexible NOx Option for Plants
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Under draft regulations approved by the Maryland Department of the Environment's Air Quality Control Advisory Council August 5, coal-fired power plants used during periods of peak demand would be offered an additional option for reducing nitrogen oxide (NOx) emissions.  The rules would give power plants the option of meeting a NOx emissions rate of 0.13 pound per million British thermal units (Btu) beginning June 1, 2020, as determined on a 24-hour systemwide block average, or a systemwide NOx tonnage cap of 21 tons per day during the ozone season.


The latest iteration of the draft regulations provides power plant operators more flexibility than a prior proposal that would have stipulated that the units install selective catalytic reduction (SCR) technology, switch from coal to natural gas or retire.  The prior rule would have required the coal units to meet a monthly limit of 0.09 pound of NOx per million Btu consistent with installation of SCR.  Gov. Larry Hogan (R) moved quickly on his first day in office to put those prior requirements on hold pending further review of the rules intended to reduce ground-level ozone.  In the interim, Hogan's administration adopted emergency regulations that required the affected plants to optimize the use of existing pollution control equipment during each ozone season, from May 1 to September 30, while the rest of the rule was reexamined. 


Facilities that would be subject to the new rules are those at which controls weren't installed under Maryland's Healthy Air Act of 2006, which required coal-fired plants to make significant cuts in emissions of NOx and other pollutants, but owners were allowed to average emissions across all units.  As a result, more costly controls were installed at key operating units, while less efficient technology often was used for units needed only during peak demand.  The current rulemaking places the focus on those peak-demand units, which are owned by two companies: the former Raven Power, now part of Talen Energy, and NRG Energy.


The text of the proposed regulations is attached to the August 5 meeting agenda of MDE's Air Quality Control Advisory Council at

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