Thermal Power Generation Emissions - National Guidelines for New Stationary Sources Discussion Document

December 2001

The revised Guidelines will be an important part of the federal contribution to meeting the Canada-Wide Standards for PM and Ozone agreed to by federal, provincial and territorial environment ministers in June, 2000. Under this agreement, Ministers committed to "ensuring that new facilities and activities incorporate best available economically feasible technologies to reduce PM and ozone levels" as part of their agreement of "keeping clean areas clean".

The Guidelines were originally published in 1981 under the Clean Air Act. They are intended to provide national emission standards for application by provinces to new coal, oil and gas-fired steam-electric power plants. The Guidelines include emission limits for sulphur dioxide (SO₂), nitrogen oxides (NO_x), total particulate matter (PM), stack opacity and provisions for continuous emissions monitoring (CEM). The NOx emissions limits in the Guidelines were revised in 1993, based on a recommendation in the 1990 Canadian Council of Ministers of the Environment (CCME) NOx/VOC Management Plan. In 1998, the Federal Action Plan to Reduce Toxic Emissions from Electric Power Plants was announced based on extensive consultations under the CEPA Strategic Options Process. This Action Plan recommended that more stringent PM limits be incorporated into the Guidelines.

Over the past two decades, the Guidelines have provided an important reference point for industry proposals and provincial decisions with respect to new power plants. However, the Guidelines are out of date with respect to improvements in technologies to reduce SOx, NOx and PM from fossil-fuel fired power plants over the past decade or more. In the U.S., new plants are built with major improvements in environmental performance based on U.S. national emission standards and state-level evaluation of best available control technologies.

This discussion document presents concise information illustrative of the performance of best available technologies (BAT) that are economically feasible. The information focuses on emission performance levels that are thoroughly demonstrated to be economically feasible through their successful application in the U.S. and other jurisdictions. (For additional information, including detailed descriptions of the technologies themselves, the reader is referred to the literature sources referenced in the Bibliography.) Based on this information, an illustrative range for proposed emission limits is developed. The discussion paper also indicates where more stringent emission limits may be appropriate. The key objective for the consultations on the Guideline revisions will be selecting discrete emission limits for the revised Guidelines considering information such as that provided in this discussion document.

• 1. Proposed Revisions
  • 1.1 General
  • 1.2 Output Basis
  • 1.3 SO2
    • 1.3.1 U.S. National New Source Performance Standards (NSPS)
    • 1.3.2 U.S. Plant-Specific Best Available Control Technology (BACT) Requirements
    • 1.3.3 Canadian Experience
    • 1.3.4 Proposed SO2 Emission Limits for Revision of the CEPA Guidelines
  • 1.4 NOx
    • 1.4.1 U.S. National New Source Performance Standards (NSPS)
    • 1.4.2 U.S. plant-specific Best Available Control Technology (BACT) Requirements
    • 1.4.3 Other U.S. NOx Requirements
    • 1.4.4 NOx requirements in European Nations
    • 1.4.5 Canadian Experience
    • 1.4.6 Proposed NOx Emission Limits for Revision of the CEPA Guidelines
  • 1.5 Particulate Matter
    • 1.5.1 U.S. National New Source Performance Standards (NSPS)
    • 1.5.2 U.S. plant-specific Best Available Control Technology (BACT) Requirements
    • 1.5.3 Canadian Experience
    • 1.5.4 Proposed Particulate Matter Emission Limits for Revision of the CEPA Guidelines
• 2. Future Revisions to the CEPA Guidelines
• 3. References
• 4. Appendices
• 5. Bibliography

The proposed revisions to the CEPA Guidelines will incorporate emission limits for SO₂, NO_x and PM based on information from the United States, Germany and other western European nations on emission requirements being applied to power plants and on the demonstrated performance capabilities of best available technologies (BAT) that are economically feasible in these jurisdictions. In particular, the proposed revisions will align with U.S. national standards and state-level determinations of Best Available Control Technology (BACT) for the permitting of new plants.

Differing emission requirements among jurisdictions result from varying interpretations of what is BAT as well as the attempt to account for differences in fuel quality. For the revisions to the CEPA Guidelines, a range of possible emission limits is proposed that reflects the ranges seen in other jurisdictions. The key objective of consultations on the revisions to the CEPA Guidelines will be to select appropriate emission limits from within the ranges proposed, or from more stringent emission limits if appropriate.

Table 1.1-1 indicates the emission limits in the existing CEPA Guidelines and the ranges of proposed emission limits for the revised Guidelines. The emission limits for the proposed revision of the CEPA Guidelines will be in the form of kilograms of pollutant per megawatt-hour of net electricity output (kg/MWh). The equivalent limit, in the form of nanograms per joule of energy input (ng/J) is indicated for ease of comparison.

The SO₂ emission limits for the proposed revision of the CEPA Guidelines are similar to the United States National New Source Performance Standards (NSPS) which are the minimum mandatory requirements for all new plants. These emission limits account for varying fuel characteristics, including sulphur content, by requiring percent reductions from uncontrolled emissions. It is proposed that the revised Guidelines contain similar provisions but that greater percent reductions and more stringent maximum and minimum emission levels should be considered, based on requirements for recently permitted new plants in the U.S. and the emissions performance of current Best Available Technologies.

For the NO_x and particulate matter emission limits, the high end of the range represents alignment with United States National New Source Performance Standards (NSPS) which are the minimum mandatory requirements for all new plants. The low end of the range represents the performance requirements for recently permitted new plants in the U.S. based on more up-to-date, site-specific assessments of Best Available Control Technology (BACT) as determined through state-level permitting processes. Still lower emission limits should be considered based on the emissions performance of current Best Available Technologies.

Note:
1. Similar to the U.S. NSPS, the proposed revision of the SO₂ emission limits will require the equivalent of a 70 to 95 percent reduction from uncontrolled emissions and a maximum equivalent emission of 520 ng/J. Where equivalent emissions are less than 50 ng/J no reduction will be required.

The proposed emission limits for the revised Guidelines are applicable to all fuels. This will expand the control options available by making the use of cleaner fuels count toward meeting emission limits. Generally, the use of cleaner fuels will result in reduced emissions of all pollutants, including toxic substances and carbon dioxide (for which there are no specific emission limits in the Guidelines). This is consistent with the concept of pollution prevention.

It is intended that the CEPA Guidelines will be updated more frequently in the future to reflect developments in new environmental initiatives or as advances in technology help redefine the concept of BAT. In Canada, jurisdictions are currently working together under the CCME Canada Wide Standards process to determine appropriate emission standards for mercury from coal-fired power plants. Meanwhile, in the U.S. the regulatory agencies are also working to develop emission limits for mercury. Therefore, while mercury emission limits for the electric power generation sector have not yet been established, the proposed revisions to the Guidelines will include a "notice of intent" to continually update the Guideline.

The emission limits in the existing CEPA Guidelines and, until recently, those in the U.S. NSPS have been specified as input-based limits. That is, the limits are expressed as allowable emissions per unit of heat input (nanograms per joule of heat input, ng/J, in the metric system of units or pounds per million British thermal units of heat input, lbs/million Btu, in the English system of units). In 1998, the U.S. NSPS NO_x limits were changed to the output-based format to promote energy efficiency and pollution prevention. At the same time the emission limit was revised to be more stringent.

The use of input-based emission limits does not encourage energy efficiency. For example, a less efficient plant requires more heat input to achieve the same level of electricity output as a more efficient plant. This greater energy input will result in higher allowable emissions for the less efficient plant than for the more efficient plant under the same input-based limit.

The proposed revisions to the Guideline will change the form of the emission limits from input-based limits to output-based limits. This will provide incentives for more efficient generation technology and operations by making efficiency count towards meeting emission limits. A benefit of more efficient technology will be a lowering of consumption of fuels together with the attendant lowering of emissions of all pollutants including greenhouse gases.

To understand the development of output-based limits it is important to understand the concept of the system "heat rate". "Heat rate" is defined as the amount of energy (heat, expressed in gigajoules) input to the system to produce a unit quantity of electrical energy output (megawatt-hour, MWh). The heat rate (gigajoules per megawatt-hour, GJ/MWh) is therefore a measure of the efficiency of the system.

The proposed output-based emission limits for the revised Guidelines are based on the demonstrated performance of best available economically feasible technologies. This emissions performance, expressed in the format of grams of pollutant emitted per gigajoule of heat input (g/GJ, which is equivalent to nanograms per joule, ng/J), is converted to output-based limits by multiplying by a net heat rate 9.4 gigajoules per megawatt-hour (GJ/MWh), representative of current economically achievable, high efficiency pulverized coal-fired power plants.

Output-based limit (kg/MWh) = emissions (g/GJ) x 9.4 GJ/MWh x 1000 g/kg

The proposed SO₂ emission limits for the revision of the CEPA Guidelines are similar to the United States National New Source Performance Standards (NSPS) developed under Title 1 of the Clean Air Act (CAA) for new electric utility steam generating units. These are the minimum mandatory requirements for all new plants in the U.S.

For SO₂, the NSPS emission limits are classified according to fuel type.

For solid fuels, the emission limit is less than either:

520 ng/J of heat input and 10% of the potential combustion concentration (90% reduction),
or
260 ng/J of heat input and 30% of the potential combustion concentration (70% reduction).

For liquid or gaseous fuel, the emission limit is less than either:

340 ng/J of heat input and 90% reduction from uncontrolled levels,
or
86 ng/J of heat input.

To illustrate this standard for coal-fired boilers and oil-fired boilers, emission limits for various uncontrolled emission rates (potential combustion concentrations) are indicated in Tables 1.3-1 and 1.3-2.

Table 1.3-3 illustrates the implications of the U.S. NSPS requirements in the Canadian context by indicating the NSPS emission limits that would apply to new plants burning the approximate range of coals used in power plants in Canada

As indicated, the NSPS are the minimum mandatory requirements for all new plants in the U.S. Under the New Source Review (NSR) provisions of the U.S. Clean Air Act, the permitting of all new plants requires, as a minimum, the application of emission limits determined in accordance with a plant-specific assessment of Best Available Control Technologies (BACT). This process generally involves the so-called "top-down" BACT assessment, whereby the most stringent emission performance demonstrated on a similar plant becomes the required performance level required for the proposed plant unless it can be shown that there are reasons, including economic factors, that make this not feasible. If the plant is to be built in an area not in compliance with ambient air quality standards more stringent permitting requirements apply. Experience with permitting under the NSR provisions indicates that emission performance requirements are commonly more stringent than the NSPS levels.

Table 1.3-4 provides information on SO₂ emission limits for recently permitted power plants in the United States. This information was obtained from a U.S. data base on facilities permitted under the NSR provisions (RACT/BACT/LAER Clearinghouse (RBLC)). The information indicates that in all cases the permitted SO₂ emission limits are much lower than the limits that would have resulted from application of the NSPS (NSPS emission limits estimated by Environment Canada).

Notes:
1. Calculated by Environment Canada based on RBLC data.
2. LSD = Lime Spray Dryer
SDA = Spray Dry Absorber
FGD = Flue Gas Desulphurization

The Belledune generating station in New Brunswick (operating since 1993) was designed to burn coal with an average sulphur content of 3.9%. This would result in uncontrolled SO₂ emissions of 2,600 ng/J of heat input. A wet flue gas desulphurization (FGD) unit is incorporated into the plant to achieve 90% sulphur removal for a controlled emission rate of 260 ng/J.

At the recent Alberta Energy and Utilities Board (EUB) hearings for the proposal by EPCOR to add a third coal-fired unit to the Genesee power plant, EPCOR committed to target - on a voluntary basis - SO₂ emissions of 78 ng/J. Depending on the sulphur content of the coal being burned at the time, this would be an emission reduction of approximately 70%. The control technology to be used would be a spray drier flue gas desulphurization (FGD) unit.

It is proposed that the revised SO₂ emission limits be at least as stringent as the U.S. NSPS for solid fuels, but that they apply to all fuels. Considering the very low emissions possible with some clean fuels, a lower threshold is proposed below which no further emission reduction is required.

Based on the emission limits being applied through site-specific BACT determinations in the U.S., consideration should also be given to an SO2 emission limits more stringent than the U.S. NSPS. This is reflected in the range of values bracketed below. Thus, the proposed SO₂ emission limits are:

For sulphur dioxide: All generating units should meet an emission limit in the form of kilograms per megawatt-hour net energy output (kg/MWh), calculated by multiplying a reference emission rate, in nanograms per joule of energy input (ng/J), by the reference net heat rate of 9.4 gigajoules per megawatt-hour (GJ/MWh)

The reference emission rate determined for each plant should be equal to or less than:

1. [400-520] ng/J of heat input and [5-10] percent of the uncontrolled emission rate ([90-95] percent reduction), or
2. [200-260] ng/J of heat input and [20-30] percent of the uncontrolled emission rate ([70-80] percent reduction), or
3. 50 nanograms per joule

The uncontrolled emission rate of sulphur dioxide should be calculated by dividing the sulphur concentration of the fuel (%S) by the higher heating value of the fuel (megajoules per kilogram, MJ/kg) and by the ratio of molecular weights of sulphur dioxide and sulphur (SO₂/S = 64/32 = 2).

Example: for a fuel with 2% S and a higher heating value of 25 MJ/kg, the uncontrolled emission rate is calculated as:

(0.02) / (25 MJ/kg) x (2SO₂/1S) x (1 MJ/10⁶ J) x (10¹² ng/kg) = 1600 ng/J

Table 1.3-5 illustrates the implications of the proposed new SO₂ emission limits versus the existing SO₂ emission limits in Guidelines, with respect to energy input-based emission rates, for new plants burning the approximate range of coals used in power plants in Canada. This table indicates that the main impacts of the proposed new SO₂ emission limits are that emissions will be capped at [400-520] ng/J for very high sulphur fuels, and that for emissions above 50 ng/J a new minimum [70-80]% reduction will be applied.

The United States NSPS for NO_x was revised in 1998, and is equivalent to 65 ng/J of heat input for the combustion of solid, liquid or gaseous fuel. Within the regulation, the standard is actually expressed on a heat output basis to account for energy efficiency: 1.6 lb/MWh of gross energy output. This is the minimum mandatory requirement for all new plants in the U.S.

As indicated, the NSPS are the minimum mandatory requirements for all new plants in the U.S. Under the New Source Review (NSR) provisions of the U.S. Clean Air Act, the permitting of all new plants requires, as a minimum, the application of emission limits determined in accordance with a plant-specific assessment of Best Available Control Technologies (BACT). This process generally involves the so-called "top-down" BACT assessment, whereby the most stringent emission performance demonstrated on a similar plant becomes the required performance level required for the proposed plant unless it can be shown that there are reasons, including economic factors, that make this not feasible. If the plant is to be built in an area not in compliance with ambient air quality standards more stringent permitting requirements apply. Experience with permitting under the NSR provisions indicates that emission performance requirements are commonly more stringent than the NSPS levels.

Table 1.4-1 provides information on NO_x emission limits for recently permitted power plants in the United States. This information was obtained from a U.S. data base on facilities permitted under the NSR provisions (RACT/BACT/LAER Clearinghouse (RBLC)). The information indicates that the permitted NO_x emission limits are equivalent to or lower than the NSPS NO_x limits

Note:
1. SCR = Selective Catalytic Reduction
LNB = Low NOx Burner

The range of emission performance indicated in Table 1.4-1 is likely conservative with respect to the potential of BAT because it is based on recent plant permits. Discussions with state environmental officials indicates that the actual performance of recent plants, and in some cases the performance proposed by recent plant proponents, is much better than that required in recent permits. Based on this, it is unlikely that any new plant would be permitted at NO_x levels above 43 ng/J.

In the United States, there are a total of 130 existing units committed to retrofitting SCR to meet requirements of the NO_x SIP Call. This is a total of 74,713 MW_electric, representing 78% of units within the NO_x SIP Call region, approximately 80% of which are coal-fired. These units are expected to achieve NO_x emission rates close to or less than 65ng/J of heat input (Bradley and Assoc., 2001).

NO_x emission limits for several western European nations are presented in Table 3.4-2 (Task Force on the Assessment ABATement of Options/Techniques for Nitrogen Oxides, 1999). These limits apply to new large boilers within the energy sector. The limits within the regulations are often expressed as mg NO_x/Nm³. These have been converted to ng/J heat input for ease of comparison. In Germany there are now more than 140 installations of Selective Catalytic Reduction (SCR) technology on utility boilers to meet the national emission performance levels.

Notes:
1. DBB = Dry Bottom Boiler
2. Dependent upon temperature of heat carrier fluid.
3. Conversion calculations in Appendix A.

Ontario Power Generation (OPG) intends to retrofit SCR on 2 units at its existing Nanticoke generating station and on 2 units at its existing Lambton generating station. These installations are intended to enable OPG to meet provincial NO_x emission caps and are not associated with specific emission rate limits.

A range of proposed NO_x emission limits for revision of the CEPA Guidelines is indicated in Table 3.4-3. The range accounts for differing interpretations of BAT. The high end of the range represents approximate alignment with United States National NSPS. The data presented above indicates that this emission limit is conservative in the sense that it is becoming a common standard of performance for retrofitted units, which represent a greater challenge than new units. Also, recently permitted new units in the U.S. are being required to meet more stringent limits. The low end of the range represents the performance requirements for recently permitted new plants in the U.S. based on BACT. However, it is noted that future new plants in the U.S. are likely to be permitted at NO_x emission levels even more stringent than the low end of the range.

The United States NSPS for particulate matter is 13 ng/J of heat input for the combustion of solid, liquid or gaseous fuel. This is the minimum mandatory requirement for all new plants in the U.S.

As indicated, the NSPS are the minimum mandatory requirements for all new plants in the U.S. Under the New Source Review (NSR) provisions of the U.S. Clean Air Act, the permitting of all new plants requires, as a minimum, the application of emission limits determined in accordance with a plant-specific assessment of Best Available Control Technologies (BACT). This process generally involves the so-called "top-down" BACT assessment, whereby the most stringent emission performance demonstrated on a similar plant becomes the required performance level required for the proposed plant unless it can be shown that there are reasons, including economic factors, that make this not feasible. If the plant is to be built in an area not in compliance with ambient air quality standards more stringent permitting requirements apply. Experience with permitting under the NSR provisions indicates that emission performance requirements are commonly more stringent than the NSPS levels.

Table 1.5-1 provides information on particulate matter (PM) emission limits for recently permitted power plants in the United States. This information was obtained from a U.S. data base on facilities permitted under the NSR provisions (RACT/BACT/LAER Clearinghouse (RBLC)). The information indicates that the permitted PM emission limits are in all cases lower than the NSPS PM limits.

Note:
1. ESP = Electrostatic Precipitator

Particulate emission performance proposed by the proponents for the three new coal-fired units undergoing approvals in Alberta are presented in Table 1.5-2. Fabric filters were chosen for all three units as the control technology to achieve these levels.

A range of proposed PM emission limits for revision of the CEPA Guidelines is indicated in Table 1.5-3. The range accounts for differing interpretations of BAT. The high end of the range represents alignment with United States National NSPS and the low end represents the performance requirements for recently permitted new plants in the U.S. based on BACT.

Table 1.5-3: Proposed particulate matter emission Limits for revision of the CEPA Guidelines

The wide range of substances emitted from fossil fuel-fired electric power generation can be major contributors to the issues of smog, acid rain, air toxics and climate change. In the recent past, advancements in the science relating to these issues has been accompanied by a rapid and marked increase in awareness of the importance of preventing and controlling emissions from the electric power sector. This has in turn been accompanied by improvements in the efficiency, and reductions In the costs, of technology to prevent and control emissions. It has long been recognized that preventing pollution by building new facilities clean is less costly than retrofitting existing facilities.

All of these factors underscore the importance of continually updating the CEPA Emission Guidelines as developments in new environmental initiatives or advances in technology help redefine the concept of BAT. For example, Canadian jurisdictions are currently working together under the CCME Canada Wide Standards process to determine appropriate standards for mercury from coal-fired power plants. Meanwhile, in the U.S. the regulatory agencies are also working to develop emission limits for mercury. When these mercury emission limits are established for the electric power generation sector, it will be advantageous to incorporate limits into the CEPA Emission Guidelines to provide a more complete, integrated and up-to-date picture of multi-pollutant emission limits for new plants.

It is important that all parties recognize that the CEPA Guidelines are not static, and take this into account in planning for new facilities. Therefore, it is proposed that the revisions to the CEPA Emission Guidelines incorporate a "notice of intent" to continually update the Guidelines.

Bradley, M.J. and Associates, personal communication, October 2001.

EPCOR. Genesee Generating Station, Phase 3, EUB/Alberta Environmental Application, June 2001.

Golder Associates. Screening document for the Installation of Selective Catalytic Reduction System for NO_x Control at Lambton and Nanticoke Generating Stations, Ontario Power Generation, November 2000

Ontario Power Generation, personal communication, September 2001.

RACT/BACT/LAER Clearinghounse (RBLC). http://www.epa.gov/ttn/catc/rblc/htm/welcome.html.

Staudt, J.E. Status Report on NO_x control Technologies and cost Effectiveness for Utility Boilers. Northeast States for Coordinated Air Use Management (NESCAUM) and Mid-Atlantic Regional Air Management Association (MARAMA), 1998.

Task Force on the Assessment of ABATement Options/Techniques for Nitrogen Oxides, Draft Background Document: Limit Values for NO_x Emissions. French- German Institute for Environmental Research, University of Karlsruhe, Germany, May 31, 1999.

Appendix A - Conversion of Emission Limit from mg/Nm³ to ng/J heat input

where E = Emission Limit (ng/J heat input)
C_d=dry-basis concentration of pollutant (mg/Nm³, dry)
F_d=F-factor (Nm³/MJ, dry), dependent on fuel (Table A - 1)
O_2,d=Concentration of O₂ (%, v/v, dry)

Table A - 1

F-factors for Selected Fuels

Alberta Research Council (ARC). 2001. Technical Advice on Air Pollution Control

Technologies for Coal-Fired Power Plants. Climate Change Technologies, Alberta

Research Council, Inc. (http:\\www3.gov.ab.ca/env/air/reports/ARC_Report.pdf)

AMEC. 2001. Annotated Survey of Selected Cost Estimates for Multi-Pollutant

Emissions Reductions Options for the Electricity Sector in Canada. Environment

Canada, Hull, Quebec.

EPA. 1997. Performance of Selective Catalytic Reduction on Coal-Fired Steam Generating Units, Final report. Office of Air and Radiation.

Folsom, B., Hartsock, D., Latham, C., Payne, R., Sommer, T. and Scaccia, M. 2001.

Reburn Scale-up Experience. The US EPAIDOEIEPRI Combined Power Plant Air

Pollutant control Symposium: The Mega Symposium. Air and Waste Management

Association, August 20-23, Chicago, IL.

Levelton Engineering Ltd. 2000. Review of Emission Levels and Technology for the Proposed fording River Power Plant. Fording Coal Ltd, Calgary, AB.

Payne, R., Sommer, T., Melick, T. and Johnson, R. 2001. Combustion Modification

NO_x control - New Results. The US EPAIDOE/EPRI Combined Power Plant Air

Pollutant control Symposium: The Mega Symposium. Air and Waste Management

Association, August 20-23, Chicago, IL.

Staudt, J.E. 1998. Status Report on NO_x Control Technologies and Cost

Effectiveness for Utility Boilers. Northeast States for Coordinated Air Use

Management (NESCAUM) and Mid-Atlantic Regional Air Management Association

(MARAMA).