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Background on Federal Air Emissions Regulations

While this database focuses on state programs, there are federal requirements that may apply in addition to these state programs. Click on the program name for additional detail.

New Source Performance Standards (NSPS) - Impose specific performance standards on a variety of specific technologies. The only likely requirement to impact small electric generating units is a limit on NOx emissions from turbines.

New Source Review (NSR) - Case by case permitting and emission control requirements triggered by new construction or modification. Requirements vary depending on the location and air quality attainment status of a region. Imposes control requirements called BACT or LAER. This program is a federal program that is administered by the states with EPA oversight.

Title V - Requires states to issue a separate federal operating permit for sources that exceed certain emission thresholds. This is also a federal program administered by the state. The operating permit does not set control requirements, but does triggers monitoring and reporting requirements. However, some states use the Title V thresholds as triggers for other control requirements.

MACT - Sets limits for sources emitting hazardous air pollutants. Only impacts "major" hazardous polluters.

New Source Performance Standards (NSPS)
The 1970 Clean Air Act called for the EPA to establish minimum federal standards of air pollution control for new equipment in a variety of industries. These New Source Performance Standards (NSPS) were developed mainly in the 1970s and 1980s for over 70 different source types, ranging from power plants to dry cleaners. The standards are supposed to be reviewed and updated periodically but that process has been spotty.

Any new plant equipment that fits the description of an NSPS source type is required to meet the NSPS emission limits and perform additional monitoring, testing, recordkeeping, and other requirements listed in the NSPS for that source type. The NSPS also applies to modifications of existing sources that result in an increase in emissions rate or emissions of a new pollutant. Due to the specific wording of the language on modifications, NSPS is almost never triggered by a modification. The result is that equipment installed since the implementation of the rule meets NSPS standards but older equipment often does not.

In 1979, EPA promulgated an NSPS for stationary gas turbines. The details of this NSPS are given in 40 CFR 60 Subpart GG. The rule has been amended multiple times over the past few years. Most of the amendments are related to monitoring and testing requirements. However, the EPA did set new emission limits for stationary combustion turbines in July 2006. The revised NSPS regulations released this summer apply to stationary combustion turbines with a heat input at peak load equal to or greater than 10 MMBtu per hour that commence construction, modification, or reconstruction after February 18, 2005. Turbine owners or operators can meet concentration-based or output-based standards. The standards can be found in this Federal Register Notice.

New turbines firing natural gas, for electric generation, with a heat input at peak load of less than or equal to 50 MMBtu/hr must meet a NOx emission standard of 42 ppm at 15% oxygen. The 50 MMBtu/h category peak heat input is based on the fuel input to a 23% efficient 3.5 MW combustion turbine. The lowest NOx emission standard under the revised regulations is for new, modified, or reconstructed turbines firing natural gas, with a heat input at peak load greater than 850 MMBtu/h. These units must meet an emission limit of 15 ppm at 15% oxygen. The 850 MMBtu/h category peak heat input is based on the fuel input to a 44% efficient 110 MW combustion turbine. The highest NOx emission standard under the modified regulations is 150 ppm and applies to new turbines firing fuels other than natural gas used for mechanical drive and modified or reconstructed turbines, both categories must have a heat input at peak load less than or equal to 50 MMBtu/h. The 150 ppm NOx limit also applies to the following turbines with a peak load heat input of less than or equal to 30 MW of output: turbines located North of the Artic Circle, operating at less than 75% of peak load, modified and reconstructed offshore turbines, and turbines operating at temperatures less than 0 degrees Fahrenheit.

Most turbines available today can achieve NOx emissions of 25-42 ppm or less without add-on controls. Thus the NSPS is not typically a controlling regulation for turbines. The NSPS also set forth conditions to limit emissions of sulfur dioxide. The emission standard for SO2 is the same for all turbines regardless of fuel usage or size. Units cannot emit into the air any gases which contain SO2 in excess of 110 ng/J (0.90 lb/MWh) gross energy output for turbines located in continental areas and 780 ng/J (6.2lb/MWh gross energy output for non-continental areas. Turbines can either meet the SO2 limit or a limit on the sulfur content of the fuel. The fuel sulfur content limit is 26 ng SO2/J (0.060 lbSO2/MMBtu) heat input in continental areas and 180 ng SO2/J (0.42 lb SO2/MMBtu) heat input in non-continental areas.

In addition to the emission limits in the NSPS for gas turbines, there are requirements for initial testing of NOx and sulfur dioxide emissions, monitoring requirements if water injection is used for NOx control, and guidelines for reporting of any noncompliance with emission limits.The NSPS was supposed to be updated every 8 years, but the NSPS for gas turbines had not been modified since 1982 before it was modified in 2006.

In 2006, the EPA also finalized NSPS for stationary compression ignition (CI) internal combustion engines (ICE), this rule became effective in September of 2006. For CI ICE, Affected sources are any CI ICE whose construction or modification commenced after July 11, 2005. The format of the final standard is an output-based emission standard for PM, NOX, CO, and NMHC in units of emissions mass per unit work performed (grams per kilowatt-hour (g/ KW-hr)) and smoke standards as a percentage. The standards are modeled after the EPA’s standards for nonroad and marine diesel engines. Emission limits are designated by pre-2007 model year engine standards and model year 2007 and later standards. Engines based on their size and model year typically do not have to meet emission limits for every regulated pollutant: PM, CO, NOx, and NMHC. Emission limits can be found in the Federal Register Notice.

New Source Review
The national clean air strategy is based on the requirement that all geographic areas meet the National Ambient Air Quality Standards (NAAQS). NAAQS were established in 1977 for six criteria pollutants, which include:

· Lead
· Nitrogen dioxide (NO2)
· Particulate matter (PM)
· Sulfur dioxide (SO2)
· Carbon monoxide (CO)
· Ground level ozone (O3)

One of the most important tools used to insure that the NAAQS are met is the requirement for pre-construction permitting of new stationary sources that emit the criteria pollutants or their precursors. Construction or modification of an emission source may trigger the requirement for a preconstruction review by an air pollution control agency under the federal or state New Source Review (NSR) program. Technically the new source permitting program comprises the prevention of significant deterioration (PSD) and the nonattainment new source review programs however, the entire program is generically referred to as NSR. The permitting process determines what pollution controls will be required.

NSR Major Source Thresholds for NOx

BACT
If a source triggers PSD, then the owner must identify the appropriate level of emission controls. In attainment areas, the standard is Best Available Control Technology (BACT). BACT means the control technology that achieves the greatest emission reduction within a preset cost per ton of reduction criterion. As a result of its structure, BACT is a changing standard, which becomes more stringent over time as new, more effective and lower cost control technologies become available. BACT for a specific application can be defined only in the context of current demonstrated technology and for a specific application. Because BACT determinations are completely site-specific, one cannot cite general BACT requirements. However, there have been BACT determinations as low as 2 to 5 ppm NOx for turbines (larger than 25 MW) and as low as 0.07 g NOx/hp-hr for engines. A sample of BACT requirements can be viewed at the EPA's website at: http://cfpub1.epa.gov/rblc/htm/bl02.cfm

Nonattainment New Source Review
The table below shows the major source thresholds for nonattainment areas, which are more stringent than in attainment areas. The NSR program requires that major new or modified emission sources located in nonattainment areas offset potential increases in NOx emissions. Offsets are required of new sources as a means of reducing their direct impact on air quality. An offset is a reduction in another facility's actual air emissions in exchange for pollution that would be created by a new source. A new source offset is called an emissions reduction credit (ERC) and is usually expressed in tons per year. ERCs can be bought or sold to meet offset requirements for a facility's expansion in nonattainment areas.

LAER
Sources that trigger NSR in nonattainment areas must meet a more stringent level of control called Lowest Achievable Emissions Reductions (LAER). LAER is defined as the most effective control technology demonstrated in practice, without regard to cost. Like BACT, LAER is a moving target that becomes more stringent over time and must be evaluated and negotiated on a case-by-case basis.

In both the NSR and PSD programs there is a strong incentive to minimize emissions to stay below the major source threshold. This can be done through a choice of technology, limits on system size or hours of operation, or voluntary use of add-on control technology. For example, a voluntary limit on hours of operation would proportionally increase the size unit that would fit within the major source threshold. A source would need to take an enforceable limit on operating hours in its permit to qualify. This is known as a "synthetic minor." In some cases, this may not be consistent with the desired utilization of the equipment and may not be an option for the owner.

Pollutant	New Source in a Moderate Nonattainment Area	New Source in a Serious or Worse Nonattainment Area	Modified Source
Lead	100 tpy	100 tpy	0.6 tpy
SO2	100 tpy	100 tpy	40 tpy
NOx	100 tpy	100 tpy	40 tpy
PM	100 tpy	70 tpy	14 tpy
CO	100 tpy	50 tpy	100 tpy

Major Source Thresholds for Criteria Pollutants in Nonattainment Areas

Title V
Title V of the 1990 Clean Air Act Amendments requires all major sources and some minor sources of air pollution to obtain an operating permit. A Title V permit grants a source permission to operate. The permit includes all air pollution requirements that apply to the source, including emissions limits and monitoring, record keeping, and reporting requirements. It also requires that the source report its compliance status with respect to permit conditions to the permitting authority.

A Title V permit is also referred to as a federal operating permit. Part 70 is the section in the Code of Federal Regulations where Title V is detailed. "Title V Permit" and "Part 70 Permit" are used interchangeably. Title V is largely an administrative program designed to ensure that the requirements of other regulatory programs are met. This program is different from the state pre-construction permitting program, which sets emission control and compliance requirements. The operating permit program is a federal program administered by the states, but it does not set its own compliance requirements.

A facility needs a Title V Permit if its potential to emit (PTE) air pollutants when it is operating at its maximum capacity is over the below thresholds:

Pollutant	PTE Tons per Year
VOC	100
CO	100
NOx	100
SO2	100
PM-10	100
Individual Hazardous Air Pollutants (HAPs)	10
Combined HAPs	25
Lead	10

The primary concern with triggering Title V is the administrative burdens that may be imposed in applying for and receiving an additional permit and continuing monitoring and reporting requirements. Thresholds for triggering Title V vary based on the attainment status of the geographic region. Sources that trigger these thresholds are considered significant sources. In the operating permits program, significant sources include those that have a potential to emit 100 tons per year of a criteria pollutant. Sources that have the potential to emit lesser amounts of air pollutants are also included, if they are located in areas not meeting the National Ambient Air Quality Standards for a particular pollutant. Some states also use the Title V threshold as a trigger for state emission control requirements. A Title V permit needs to be renewed every five (5) years.

MACT
EPA has recently proposed several new MACT standards, among them are standards for turbines and internal combustion engines. The new standards would put limits on the amount of emissions that a major source can release and are aimed at reducing formaldehyde, acrolein, methanol and acetaldehyde emissions. A major source is one that emits more than 10 tons per year of a single hazardous air pollutant (HAP) or 25 tons per year of a combination of HAPs.

Emission limitations for engines and turbines are listed as formaldehyde and carbon monoxide (CO) limits. The EPA is suggesting that technologies aimed at reducing CO will concurrently reduce other hazardous pollutants to appropriate levels. This method is suggested, in part, because measuring hazardous emissions can be problematic and complicated for many units. The assumption that CO control technology will automatically result in control of other hazardous emissions is likely to be controversial, particularly among industry representatives. EPA is alternately offering the option of reducing formaldehyde emissions. The required reductions are listed below.

Internal Combustion Engines
The standards would apply to new, reconstructed and some existing stationary IC engines greater than 500 hp and located at a major source of air toxins. Emission limits are listed for formaldehyde and carbon monoxide only. The proposed emission limits are as follows:

Engines operating for emergencies, limited use or burning landfill or digester gas are exempt from the emission limits. In addition, existing sources are exempted with the exception of spark ignition 4-stroke rich burn engines, which will have three years to comply with the new standards. The rule is expected to be finalized sometime in 2003. EPA anticipates that 20,300 new engines will be installed by the end of the fifth year of the program. In addition, 4,600 existing engines may be subject to the rule. However, EPA estimates that only 40% of new and existing engines are located at major source of air toxics (and therefore subject to the MACT rule).

Combustion Turbines
The standards would apply to all new stationary combustion turbines at a major source and existing lean premix combustion turbines at a major source. Existing turbines would have up to three years to comply with the new standards. Sources may opt to comply with new requirements by installing carbon monoxide catalytic oxidation systems for a reduction of CO emissions by 95%. Sources may also opt to reduce formaldehyde emissions to 43 ppb. Combustion turbines that are smaller than 1 MW, burn landfill or digester gas, are considered "limited use" or are used for emergencies only are exempt from this requirement. The EPA estimates that 160 existing turbines and 155 new turbines per year (for the following five years) will be subject to the requirements. The EPA plans to finalize the rule in 2003.