This database focuses on state regulatory programs potentially applicable to small on-site electric generators. The key federal requirements that may apply in addition to these state programs are described here. Click on the program name for additional detail.

National Ambient Air Quality Standards (NAAQS) – Issued by EPA for six criteria pollutants (carbon monoxide, lead, ozone, nitrogen dioxide, sulfur dioxide and particulate matter) to protect public health and the natural environment. Counties are designated as “attainment” or “nonattainment” based on whether they exceed these air quality standards or contribute to nearby violations. States are required to submit State Implementation Plans (SIPs) to EPA detailing how they will maintain or meet these standards.

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 federal program is typically administered by individual states with EPA oversight.

Title V - Requires states to issue a separate federal operating permit for sources that exceed certain air pollutant emission thresholds. This is also a federal program typically administered by individual states. The operating permit does not set new control requirements, but rather consolidates all the air requirements applicable to a facility under one regulatory document and establishes the monitoring and reporting requirements necessary to demonstrate compliance with the permit.

Maximum Achievable Control Technology (MACT) - Sets limits for sources emitting hazardous air pollutants. In general, only impacts "major" hazardous polluters, although EPA has established MACT standards for certain larger engines at “minor” sources.

New Source Performance Standards (NSPS) - Impose specific performance standards on a variety of specific technologies. The requirements likely to impact small electric generating units are limits on NOx and SO2 emissions from turbines and NOx, VOC, and CO emissions from engines.

National Ambient Air Quality Standards (NAAQS)

EPA issues National Ambient Air Quality Standards (NAAQS) for six criteria pollutants (carbon monoxide, lead, ozone, nitrogen dioxide, sulfur dioxide and particulate matter) to protect public health and the natural environment, as in the case of visibility. Counties are designated as “attainment” or “nonattainment” based on whether they exceed these air quality standards or contribute to nearby violations. The designation status is important in that it informs the public about whether the air quality of a particulate area is healthy and in turn it affects the type of air permitting programs that facilities must navigate to install new units. Once areas are designated as “nonattainment,” states generally have three years to develop implementation plans detailing how they will meet the standards and come into “attainment.”

Recently, two of the NAAQS standards were revised: the fine particulate standard (PM 2.5) and the 8-hour ozone standard.

PM2.5

EPA first issued standards for particulate matter in 1971 and revised the standards in 1987 and 1997. On September 21, 2006 EPA revised these for particles less than 2.5 micrometers in diameter (known as "fine" particles). Fine particles have significant health impacts such as increased respiratory symptoms, including decreased lung function, asthma and bronchitis because they are easily inhaled deeply into the lungs. There are standards to be met on a 24 hour basis and on an annual basis, based on health effects and visibility studies. EPA strengthened the 24-hour PM 2.5 standard from the 1997 level of 65 micrograms per cubic meter (μg/m3) to 35μg/m3, and retained the current annual fine particle standard at 15μg/m3. (The Agency also retained the existing national 24-hour PM10 standard of 150μg/m3 and revoked the annual PM10 standard, as available evidence does not suggest a link between long-term exposure to current levels of coarse particles and health.) The more stringent particulate standards affect small electric generators in that they drive the development of new or tighter standards for new units through New Source Performance Standards (NSPS) and for new and existing units through technology control standards (“RACT” standards). Also, as individual states are responsible for meeting these standards, some will reduce the air quality modeling “increment” available to facilities for permitting certain new projects. More information on PM 2.5 can be found at http://www.epa.gov/oar/particlepollution/standards.html.

8-hour Ozone

The 8-hour ozone NAAQS was promulgated by EPA in 1997 and challenged by a number of industry groups. The subsequent legal review delayed the process of designating the attainment status of areas. Ozone per se is not controlled; rather its precursors – NOx and volatile organic compounds (VOCs) are regulated to reduce the formation of ground level ozone.

Subpart 1

As part of the transition from the 1-hour ozone standard to the 8-hour standard, areas that were previously in attainment with the 1-hour standard but which are not in attainment with the 8-hour standard are classified with the designation “Subpart 1” (referring to Subpart 1 of Part D of Subchapter I of the Clean Air Act). Areas with Subpart 1 designation have less severe requirements for air quality improvement measures to be included in their State Implementation Plans and may request extra time to meet the 8-hour ozone standard.

Most recently, on May 31, 2007, PEA announced its final decisions with respect to certain provisions in the 8-hour ozone implementation rule related to how electric generating units (EGUs) meet the standards and how emissions reductions may be used for LAER (lowest achievable emission rate limitations that apply in nonattainment areas) and permitting emissions “offsets.” (The rule is not yet final as of September 2008.) EPA issued decisions on two issues:

1. Compliance with the Clean Air Interstate Rule (CAIR) satisfies the NOx RACT requirements for EGUs in areas where EPA believes CAIR achieves greater emissions reductions than application of reasonably available control technology (RACT) standards to individual units. States not included in EPA’s analysis are allowed to adopt the same presumption rather than developing and implementing RACT rules through air permitting.
2. EPA extended the deadline for states in the CAIR region to submit their plans for NOx standards for EGUs.

CAIR has since been vacated by the courts, throwing this determination into question. More information on the 8-hour ozone standard is available at http://www.epa.gov/ozonedesignations/basicinfo.htm.

 

New Source Review (NSR)

The national clean air strategy is based on the requirement that all geographic areas meet the National Ambient Air Quality Standards (NAAQS) established in 1977.

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 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 both 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.

Prevention of Significant Deterioration
In attainment areas, the new source requirements are addressed by the PSD program. PSD review is triggered by the construction of a "major" source of emissions or a modification of an existing major source that causes a "significant" increase in emissions. "Major" for new PSD of NOx sources means 250 tpy except for the sources listed in the table below, for which the threshold is 100 tpy. An individual turbine or engine, by itself, may not have high enough emissions to trigger PSD, but a specific project or construction of a whole facility could. The measure of emissions is based on potential to emit at full output and utilization - emissions at full output for an entire year.

PSD Source Categories with 100 TPY Major Source Thresholds

Fossil fuel-fired steam electric power plants > 250 MMBtu/hr input
Fossil fuel boilers (or combinations) total > 250 MMBtu/hr heat input	Petroleum storage and transfer units > 300,000 bbl storage capacity
Municipal incinerators > 250 tons/day refuse	Coal cleaning plants
Portland cement plants	Primary zinc smelters
Iron and steel mill plants	Primary aluminum ore reduction plants
Primary copper smelters	Hydrofluoric acid plants
Sulfuric acid plants	Nitric acid plants
Kraft pulp mills	Petroleum refineries
Lime plants	Carbon black plants/TD>
Primary lead smelters	Phosphate rock processing plants
Coke oven batteries	Sintering plants
Fuel conversion plants	Secondary metal production plants
Charcoal production plants	Glass Fiber processing plants
Taconite ore processing plants	Secondary metal production plants

The PSD threshold for modifications is an emissions increase of 40 tpy. This is important in the common case where a DG unit is added to an existing facility. If the facility is already a major source, the major modification trigger would be 40 tpy, rather than 100 or 250 tpy. This would make a significant difference in the potential for triggering PSD review.

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 emissions 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.

Nonattainment Classification	New Source	Modified Source	Offset Ratio
Attainment Area	100/250 tpy	40 tpy	N/A
Ozone Transport Region	50 tpy	40 tpy	1.15:1
Moderate	100 tpy	40 tpy	1.15:1
Serious	50 tpy	25 tpy	1.2:1
Severe	25 tpy	25 tpy	1.3:1
Extreme	10 tpy	25 tpy	1.5:1

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.

Major Source Thresholds for Criteria Pollutants in Nonattainment Areas
(tons per year)

Pollutant	New Source in a Moderate Nonattainment Area	New Source in a Serious Nonattainment Area	New Source in Severe/ Extreme Nonattainment Area	Modified Source
Lead	100 tpy	100 tpy		0.6 tpy
SO2	100 tpy	100 tpy		40 tpy
NOx	100 tpy	50 tpy	25 tpy/10 tpy	40 tpy
PM-10	100 tpy	70 tpy		15 tpy
CO	100 tpy	50 tpy		100 tpy
Ozone	100 tpy (50 tpy in Ozone Transport Region)	50 tpy	25 tpy/10 tpy	40 tpy

 

Nonattainment Area Maps

Nonattainment Area Maps by pollutant can be viewed at http://www.epa.gov/air/data/nonat.html?us~USA~United%20States.

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 new source major thresholds (see the previous section on NSR).

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 permit 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 and may need to be opened in between renewals if new requirements (such as MACT) need to be incorporated into the permit.

MACT

EPA has recently undertaken several regulatory efforts to control hazardous air pollutant emissions from new or reconstructed stationary internal combustion engines and combustion turbines. The new standards put limits on the amount of emissions that a major source and certain area (minor) sources 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. Sources that emit less than major source thresholds of HAPs are referred to as “area sources” and also often as “minor sources” in air permitting context.

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 HAP emissions can be problematic and complicated for many units. EPA is alternately offering the option of directly measuring and reducing formaldehyde emissions. The required reductions are listed below.

Numerous MACT and related NSPS rulemakings make sorting out the requirements for new engines and turbines a bit confusing. Initially, MACT standards were promulgated for internal combustion engines larger than 500 brake horse-power at locations that are major sources of HAPs; recently additional standards have been enacted for units less than 500 BHP at major sources and units larger than 500 BHP at area sources. Also, the initial turbine MACT published in March 2004 identified eight subcategories of turbines; a subsequent Federal Register notice in April 2004 deleted four of the subcategories. Following are summaries of the key standards from these MACT requirements.

Reciprocating Internal Combustion Engines (RICE)

In June 2004, EPA published the RICE MACT standard (40 CFR 63 Subpart ZZZZ) requiring all RICE rated above 500 BHP located at major sources to meet HAP emissions standards. In January 2008, EPA published an additional MACT RICE addressing engines larger than 500 BHP at area (minor) sources and engines smaller than 500 BHP at major sources. At the same time, EPA published additional NSPS standards for new spark ignition internal combustion engines. The rules are interrelated as most of the sources subject to MACT in the January 2008 rulemaking automatically ”meet” the MACT by complying with the NSPS standards.

RICE MACT applies to all stationary reciprocating internal combustion engines at major sources in five categories. “New” or “reconstructed” RICE larger than 500 BHP at major sources are those built on or after December 19, 2002; “existing” units were built before that date.

1. 500 BHP or less – these units are not subject to the initial RICE MACT from June 2004; they were addressed in the January 2008 MACT/NSPS rulemaking.
2. Emergency use – there are no requirements for existing units; new and reconstructed units must complete the initial notification requirement.
3. Limited use – there are no requirements for existing units; new and reconstructed units must complete the initial notification requirement.
4. Units that combust landfill or digester gas for more than 10% of their heat input - there are no requirements for existing units; new and reconstructed units must complete the initial notification requirement.
5. Other – the standards for these four categories are described in the table below.
1. 2 Stroke Lean Burn
2. 4 Stroke Lean Burn
3. Compression ignition
4. 4 Stroke Rich Burn
 

MACT Formaldehyde Emission Limits for IC Engines (RICE)

(Note that engines can meet either the emissions level OR the technology limit)

Technology	Maximum Formaldehyde Emissions Level	Control Technology Limits
Spark ignition 4-stroke rich burn (existing, new, and reconstructed)	350 ppb	NSCR* to a reduction of 76% of formaldehyde or more; catalyst pressure drop cannot change more than 2” of water from performance test; catalyst inlet temperature >= 750 oF and =< 1250 oF.
Spark ignition 2-stroke lean burn (new and reconstructed)	12 ppm @ 15% O 2	CO Catalytic oxidation system to a reduction of 60% of CO or more; if using NSCR, catalyst pressure drop cannot change more than 2” of water from performance test; catalyst inlet temperature >= 450 oF and =< 1350 oF.
Spark ignition 4-stroke lean burn (new and reconstructed)	14 ppm @ 15% O 2	CO Catalytic oxidation system to a reduction of 93% of CO or more; if using NSCR, catalyst pressure drop cannot change more than 2” of water from performance test; catalyst inlet temperature >= 450 oF and =< 1350 oF.
Compression ignition (new and reconstructed)	580 ppb @ 15%O 2	CO Catalytic oxidation system to a reduction of 70% or CO or more; if using NSCR, catalyst pressure drop cannot change more than 2” of water from performance test; catalyst inlet temperature >= 450 oF and =< 1350 oF.

*An add-on catalytic NOx control device that, in a two-step reaction, promotes the conversion of excess oxygen, NOx, CO, VOCs into CO2, nitrogen, and water.

Units that choose to comply with the MACT through reduction of CO and which don’t use a CEMS (continuous emissions monitoring system) along with units that choose to comply with MACT by reducing formaldehyde must conduct semi-annual performance tests, which are reduced in frequency to annual if the testing of the units meets appropriate limits. The units listed in the table also must follow the initial compliance, testing, recordkeeping, and semi-annual compliance reporting requirements detailed in the MACT rule. Also, area sources that become major must meet RICE MACT requirements immediately upon crossing that determination threshold.

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 emissions limits.

“New” or “reconstructed” RICE larger than 500 BHP at area sources or smaller than 500 BHP at major sources are those built on or after June 12, 2006; existing were built before that date.

Combustion Turbines
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 stationary combustion turbine MACT (40 CFR 63 Subpart YYYY) applies only to units located at a major source of HAP emissions, not to units located at area (minor) sources. As described under the RICE MACT, at oil and gas production facilities, owners count HAPs emissions by areas called surface sites, which include glycol dehydrators, tanks with the potential for flash emissions, RICE, and combustion turbines. Combustion turbines located at surface site groups with HAPs emissions larger than 10 tpy of any one HAP or 25 tpy of a combination of HAPs are subject to turbine MACT.

The initial turbine MACT published in March 2004 identified eight subcategories of turbines; a subsequent Federal Register notice in April 2004 deleted four of the subcategories. The delisted categories include:

• Emergency stationary combustion turbines (this does not include stationary combustion turbines used as peaking units at electric utilities or stationary combustion turbines at industrial facilities that typically operate at low capacity factors).
• Lean pre-mix gas turbines (less than 1000 hours/year fired with oil)
• Stationary diffusion flame gas turbines (less than 1000 hours/year fired with oil)
• Combustion turbines on the North Slope of Alaska

The remaining categories of combustion turbines subject to MACT are

• Stationary combustion turbines that burn landfill gas for more than 10% of their gross heat input – initial notification required only for new/rebuilt
• Stationary combustion turbines rated less than 1 MW peak power output - no initial notification required for existing or new
• Lean pre-mix oil-fired turbines (more than 1000 hours/year fired with oil)
• Stationary diffusion flame oil-fired turbines (more than 1000 hours/year fired with oil)

New or reconstructed combustion turbines are those built after January 14, 2003; existing on or before that date. (Existing turbines had up to three years to comply with the new standards.)

 

MACT Standards: Stationary Combustion Turbines

 

Combustion Turbines Subject to MACT Standards	Notifications, Testing, Recordkeeping	Emissions Limitation	Operating Limitation
Lean-premix oil-fired stationary combustion turbine Diffusion flame oil-fired stationary combustion turbine	Initial notification, notification of compliance status, and semi-annual reports along with associated recordkeeping	Limit concentration of formaldehyde to 91 ppbvd or less at 15% O2	If a catalyst is used to achieve compliance with the emissions limit, maintain the 4-hour rolling average inlet temperature within manufacturer’s suggested range.
Stationary combustion turbines rated less than 1 MW peak power output Stationary combustion turbines that burn landfill gas for more than 10% gross heat input.	No requirements for existing turbines; new landfill gas turbines must submit an initial notification.	None	None

 

Potential Future Actions: Existing Diesel Engines

In January 2008 EPA published an Advanced Notice of Proposed Rulemaking (ANPR) to solicit input on the inclusion of stationary diesel engines, existing locations, usages, characterization of size and other technical parameters, potential emissions reductions control technologies and their associated costs, as well as health concerns related to diesel exhaust. EPA has undertaken several actions recently to reduce diesel exhaust emissions, which consist primarily of fine particulate (less than 2.5 microns diameter or less). Because these particles have a large surface area, they are effective at absorbing organic and inorganic HAPs, which pose numerous health risks. In addition, the fine particle size makes them readily inhaled deeply into the lungs. EPA received comments through February 25, 2008 and may explore options to achieve further reductions from existing stationary diesel engines in the future.

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.

Combustion Turbines
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, in July 2006, EPA published new standards in 40 CFR 60 Subpart KKKK that 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; a summary of the key emissions limits for new turbines are here.

 

NSPS NO x Emission Standards for Combustion Turbines

 

Turbine Technology	Heat Input, Peak Load (HHV)	NOx Emission Standard (See the Federal Register Notice for standards in units of lb/MWh)
Natural gas, electric generating	<= 50 MMBtu/hr	42 ppm @15%O 2
Natural gas, mechanical drive	<= 50 MMBtu/hr	100 ppm @15%O 2
Other turbine, natural gas	> 50 and <= 850 MMBtu/hr	25 ppm @15%O 2
Fuels other than natural gas, electric generating	<= 50 MMBtu/hr	96 ppm @15%O 2
Fuels other than natural gas, mechanical drive	<= 50 MMBtu/hr	150 ppm @15%O 2
Other turbine, fuels other than natural gas	> 50 and <= 850 MMBtu/hr	74 ppm @15%O 2
Heat recovery units operating independent of the combustion turbine	All sizes	74 ppm @15%O 2
For modified and reconstructed turbines and turbines north of the Arctic Circle, see the Federal Register Notice.

Use of water or steam injection technology to control NOx emissions requires the use of a CEMS (continuous emissions monitoring system) device. Initial performance testing is required to demonstrate compliance with the NOx emissions standards. If a CEMS device is not used, annual stack testing for NOx is required.

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/hr 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/hr. These units must meet an emission limit of 15 ppm at 15% oxygen. The 850 MMBtu/hr 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/hr. 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 oF .

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 sets 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 SO2 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.

NSPS SO 2 Emission Standards for Combustion Turbines

Turbine Technology	Heat Input, Peak Load (HHV)	SO2 Emission Standard
All	All	0.90 lb/MWh for continental areas; 6.2 lb/MWh for noncontinental areas

 

Internal Combustion Engines

Compression Ignition (CI)
In July 2006, the EPA finalized NSPS for stationary compression ignition (CI) internal combustion engines (ICE). This rule became effective in September 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 this Federal Register Notice.

Spark Ignition (SI)

In January 2008, the EPA finalized NSPS for stationary spark ignition (SI) internal combustion engines (ICE) in conjunction with promulgating MACT for new and reconstructed RICE addressing engines larger than 500 BHP at area (non-major) sources and engines smaller than 500 BHP at major sources. The rules are interrelated as most of the sources subject to MACT in the January 2008 rulemaking automatically ”meet” the MACT by complying with the NSPS standards. This rule became effective March 18, 2008. An SI engine is either a gasoline-fueled engine or and engine with a sparking type device and operation similar to the Otto combustion cycle. For SI ICE, affected sources are any SI ICE whose manufacture or modification commenced after July 1, 2007; standards for different size and fuel-type are listed by future manufacture dates. As with the CI ICE standards, 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)). 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 this Federal Register Notice; a summary of the key standards are presented here.

 

NSPS for Stationary SI engines <= 19 kW (25 hp) manufactured

after July 1, 2008

Engine class	Emis Stds in g/kW-hr (g/HP-hr)
	HC + NOx	NMHC + NOx	CO
I – displacement between 100 cc and 225 cc	16.1 (12.0)	14.8 (11.0)	610 (455)
I-A – displacement less than 66 cc	50 (37)	__
I-B – displacement between 66 cc and 100 cc	40 (30)	37 (27.6)
II – displacement > 225 cc	12.1 (9.0)	11.3 (8.4)

 

 

NSPS for Stationary SI engines > 19 kW (25 hp)

Max Engine Power	Type of Engine	Date of Manufacture	Emis Stds in g/kW-hr (g/HP-hr)
			HC + NOx	CO
25 < HP < 500	Non-emergency gasoline and rich-burn LPG Severe duty	July 1, 2008	2.7 (2.0)	4.4 (3.3) 130 (97.0)
HP >= 500	Non-emergency gasoline and rich-burn LPG Severe duty	July 1, 2007	2.7 (2.0)	4.4 (3.3) 130 (97.0)
25 < HP < 100	Non-emergency natural gas and lean-burn LPG Severe duty	July 1, 2008	3.8 (2.8)	6.5 (4.8) 200 (149.2)

 

 

NSPS for Stationary Engines >= 100 HP and Emergency Engines > 25 HP

Type of Engine	Max Engine Power	Date of Manufacture	NOx	CO	VOC	NOx	CO	VOC
Non-emergency natural gas and lean burn LPG	100 <=HP < 500	7/1/2008	2.0	4.0	1.0	160	540	86
Non-emergency natural gas and lean burn LPG	500 >= HP< 1350	1/1/2011	1.0	2.0	0.7	82	270	60
		1/1/2008	2.0	4.0	1.0	160	540	86
Non-emergency lean burn natural gas and non-emergency LPG (except lean burn 500 HP 1350)	HP >=500	7/1/2010	1.0	2.0	0.7	82	270	60
		7/1/2007	2.0	4.0	1.0	160	540	86
Landfill/ digester (except lean burn)	HP > = 500	7/1/2010	1.0	2.0	0.7	82	270	60
	HP <500	7/1/2008	3.0	5.0	1.0	220	610	80
	HP >=500	1/1/2011	2.0	5.0	1.0	150	610	80
		7/1/2007	3.0	5.0	1.0	220	610	80
		7/1/2010	2.0	5.0	1.0	150	610	80
Landfill/ digester lean burn	500 >= HP <1350	1/1/2008	3.0	5.0	1.0	220	610	80
		7/1/2010	2.0	5.0	1.0	150	610	80
Emergency	25 > HP <130	1/1/2009	10	387	N/A	N/A	N/A	N/A
	HP >=130	1/1/2009	2.0	4.0	1.0	160	540	86