M E M O R A N D U M

TO: Gary S. Rose, Director Date Rec'd: 08/30/2011

 FROM: James Grillo, APCE

Kiernan Wholean, SAPCE

Richard A. Pirolli, Assistant Director

SUBJECT: BACT Recertification for Montville Power LLC Biomass, Permit No. 107-0056

Pursuant to Part VII.F of NSR permit number 107-0056, issued on April 6, 2010, Montville Power LLC has 

submitted a BACT recertification analysis. The NSR permit requires that BACT be recertified if the project did 

not start construction within (18) months of the permit issue date. The following is a chronological accounting of 

the BACT recertification process:

On August 30, 2011 Montville Power submitted a timely BACT analysis. 

On September 20, 2011 the Department requested additional information by electronic mail to clarify 

several items in the submitted BACT analysis. (see electronic mail from J. Grillo) 

On April 11, 2012 Montville Power submitted an analysis of fugitive GHG emissions from natural gas 

piping components and SF6 emissions from electrical equipment. (see electronic mail from C. Karlic)

On April 24, 2012 the Department notified Montville Power that a new BACT analysis was posted on 

the RBLC website and that they should include this determination in their submittal to the Department’s 

September 2011 request for additional information. (see electronic mail to C. Karlic)

On May 7, 2012 Montville Power submitted a revised BACT analysis in response to the Department’s 

previous requests for additional information.

On July 12, 2012 the Department requested additional information by electronic mail to clarify several 

items concerning the CO2 BACT analysis. (see electronic mail from J. Grillo) 

On August 1, 2012 Montville Power submitted additional information in response to the Department’s 

July request. (see electronic mail from C. Karlic)

On August 12, 2012 Montville Power submitted additional information clarifying the proposed energy 

efficiency measures for the existing boiler. (see electronic mail from C. Karlic)

On August 14, 2012 Montville Power submitted additional information supporting a higher emissions 

limit for SO2 than a recently permitted source in Wisconsin. (see electronic mail from C. Karlic)

On September 7, 2012 Montville Power submitted additional information in response to the 

Department’s requests of August 21st and 22nd, 2012. (see electronic mail from C. Karlic)

The NSR permit that was issued in April 2010 included a BACT review for the following pollutants: PM10/2.5, 

SOx, NOx, VOC, and CO. On January 28, 2011, the Department adopted new regulations concerning CO2

emissions from new sources and since Montville Power had not begun construction of the biomass project prior 

to these new regulations a complete BACT analysis of CO2 emissions is required pursuant to RCSA 22a-174-

3a(j).

The Montville project has been designed to operate with two distinct operating scenarios, one being a biomass 

only base load unit producing 42 MW (net) of electricity, the other a fossil fuel fired unit for peaking up to 82 

MW. 
Montville Power LLC BACT Recertification 2012

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Technical Analysis

A. Criteria Pollutants:

Montville Power has identified five (5) recently permitted biomass plants using the EPA RACT BACT/LAER 

Clearinghouse (RBLC) and has made the following determinations concerning their project:

Beaver Wood Energy Fair Haven, LLC – Vermont: February 10, 2012, New advanced stoker fired 34 

MW gross biomass electric generating station has not been constructed or the emissions verified by stack 

testing.

Several pollutants had slightly lower emission rates or averaging times compared to the Montville project 

and can be compared in the table below:

Pollutant Beaver Wood Montville

NOx 0.06 lbs/MMBtu (hourly)

0.03 lbs/MMBtu (12-month rolling)

0.06 lbs/MMBtu (24-hour)

CO 0.075 lb/MMBtu (24-hr block) 0.1 lbs/MMBtu (8-hr block)

VOC 0.005 lbs/MMBtu 0.01 lbs/MMBtu

While these pollutants have lower emissions rates than the Montville permit, there are significant 

differences in the projects: 

1. The Beaver Wood project is a new construction project firing biomass only where as the Montville 

project is a conversion of a existing 82 MW EGU boiler firing natural gas/No. 6 oil in addition to the 

biomass at 42 MW. This unit will use a recently new and unproven proprietary technology from 

Riley Power to control NOx, CO and VOC called a multi-pollutant catalytic reactor (MPCR). There 

were no other identified biomass units with emission rates for NOx, CO and VOC similar to the 

proposed Beaver Wood project. 

2. The Beaver Wood project is a biomass only fired boiler where as Montville will retain the ability to 

burn either natural gas or No. 2 ULSD fuel oil for peaking up to 82 MW. The emissions control 

system for the Montville project has been designed to operate with all three fuels at full load and 

achieve the permitted emission limits. There is no known facility either planned or operating that 

will be operated like the Montville project.

3. The hourly averaging time for NOx emissions compared to the 24-hour time period for Montville is 

unproven for a variable fuel source such a biomass. The much lower emission rate associated with 

the 12-month rolling average also is unproven for boilers using this type of fuel.

4. The lower CO emission is possibly achievable because the averaging time is longer than the 

Montville project, however the emission rate is still unproven at this time.

5. The VOC emission rate is lower using the new MPCR control system but it also not comparable to 

any other similar biomass plant which leads to speculation of the validity of the emissions rate and 

the ability of the unit to achieve this emissions rate.

The emissions rates and averaging times for the Beaver Wood project can be dismissed as BACT at this 

time as discussed above primarily because the Beaver Wood project has been designed as a new source to

be operated as a biomass only fired unit with a control system that appears to be unproven at this time as 

no other source has been identified to be using this control system. Additionally, the Montville project 
Montville Power LLC BACT Recertification 2012

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will be required to operate with two distinct operating scenarios, one being a biomass only base load unit

producing 42 MW of electricity, the other as 82 MW fossil fuel fired peaking unit. There are no other 

identified projects similar to the Montville project where stringent emissions rates are being proposed 

with two distinct operating scenarios.

International Paper Company, Red River Mill – Louisiana: April 5, 2011.

Modification to an existing biomass plant allowing an increase of SOx emissions up to 60 lbs/hr. The 

Montville project has a SOx emission rate of 15 lbs/hr.

Oglethorpe Power Corporation, Warren County Biomass Energy Center – Georgia: December 17, 2010. 

Planned new construction of a fluidized bubbling bed boiler. Oglethorpe Power decided not to pursue 

the project.

Georgia Power Company, Mitchell Steam Generating Plant – Georgia: December 3, 2010.

Conversion of a coal fired EGU to stoker fired biomass. None of the criteria pollutants in the Mitchell 

Steam Generating BACT determination are lower than the Montville project.

Laidlaw Berlin Biopower LLC – New Hampshire: July 26, 2010

Conversion of an existing boiler to a bubbling fluidized bed biomass boiler. Similar to the Beaver Wood 

project discussed above, the Laidlaw project has not been constructed or the emissions verified at this 

time and the emissions limitations should be not be considered as an achievable BACT and should be 

dismissed as BACT.

The Department did identify another recently permitted utility sized biomass boiler that is currently under 

construction in Wisconsin. 

WE Energies is constructing a 50 MW dual fired, natural gas and biomass, fluidized bed boiler. While 

this is not the same technology as the Montville project it is discussed below because it is actually under

construction and there is an expectation that the unit will meet the permitted emissions rate. Two 

pollutants in the Wisconsin permit have lower emission rates when compared to the Montville project 

and are listed in the table below:

Pollutant WE Energies Montville

PM10/2.5 0.024 lb/MMBtu/hr 0.026 lbs/MMBtu 

SOx 8 lb/hr 15 lb/hr

The WE Energies project is a fluidized bed boiler and it will use a fabric filter baghouse to control PM 

emissions which may allow the unit to achieve the slightly lower PM emission rate. The Montville 

project will be a stoker boiler and fabric filters were rejected as BACT in the original permitting of this 

unit because of potential baghouse fires. The Department has not identified any solid fuel stoker boilers 

using a baghouse to control PM emissions and therefore fabric filters are still considered technically 

infeasible at this time.

While the SOx emissions rate for WE Energies is half of the Montville project it is unknown where the 

emissions rate was derived from as there was no BACT analysis completed for SOx emissions. It 

appears the sulfur content of the fuel may be representative of the local biomass supply as all of the 
Montville Power LLC BACT Recertification 2012

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biomass for this unit will come from the adjacent mill. The WE Energies permit has a fuel sulfur limit of 

0.35% by weight which would not equate to their permit limit of 8 lbs/hr. Using WE Energies sulfur 

limit, firing rate and the assumption that 100% of the sulfur converts to SOx, the emissions rate would be 

about 664 lbs/hr. During the public comment period, it was noted that allowable sulfur content in the 

permit did not equate to the permit emissions limit of 8 lbs/hr and that a BACT analysis for SO2 should 

have been required. The state responded that the emissions rate was based on historic data from an 

existing biomass unit at the mill and that the project would not need a BACT analysis for SO2 since 

annual emissions would be below 40 tpy. The Montville emissions rate is based on the default AP-42 

emissions factor of 0.025 lb/MMBtu with the fuel coming from multiple sources with unknown sulfur 

contents. The WE Energies SO2 limit does not represent any other permitted biomass emissions 

limitation for SO2. Since the emissions rate for WE Energies is based on historical emissions data for 

their fuel supply a similar rate should not be considered BACT at this time for the Montville project.

The Oglethorpe, Laidlaw and WE Energies projects are new fluidized bed units and while there are some criteria 

pollutants that have been permitted with lower emissions rates than the Montville project, as discussed above, 

they should be dismissed for the following reasons. First, the Montville project is proposed as a modification to 

an existing source, where the existing boiler would be modified to allow stoker firing for biomass and 

conventional firing for fossil fuels. This modification would continue to use much of the ancillary equipment for 

the boiler. If Montville were required to install a fluidized bed fired unit to meet slightly lower emissions, the 

entire existing boiler and possibly some of the ancillary equipment would need to be removed which would 

greatly increase the cost of the project to the point where the project would not be constructed. Based on this, the 

use of a fluidized bed boiler would be technically and financially infeasible for the project.

Criteria Pollutant BACT Recommendation:

The project as proposed would reduce criteria pollutants from fossil fuel firing as compared to existing operation 

because the modification allows use of control technology installed for biomass to be used with fossil fuels and 

the modification requires switching from No. 6 fuel oil to ULSD.

Existing Emissions Rate

(lbs/MMbtu)

Post Modification Emission 

Rate (lbs/MMBtu)

Percent Reduction

Nat. Gas No. 6 oil Nat. Gas ULSD Nat. Gas ULSD 

NOx 0.20 0.25 0.06 0.06 70% 76%76

CO 0.098 0.036 0.084 0.036 14% 0%

VOC 0.0055 0.005 0.0055 0.0014 0% 72%

PM 0.10 0.14 0.0076 0.024 92% 83%

SOx 0.0006 0.33 0.0006 0.0017 0% 99%

Based on the information submitted by permittee, the Department’s review and verification, the previously 

approved BACT for the criteria pollutants in the Montville Power CP/OP permit are considered adequate at this 

time and no further modification of the permit is required for these pollutants. [RCSA 22a-174-3a(j)(5)]
Montville Power LLC BACT Recertification 2012

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B. Greenhouse Gase (CO2e):

On January 28, 2011, the Department incorporated a requirement to conduct PSD/BACT analysis for CO2e 

emissions on new sources with potential emissions greater than 100,000 tons or more per year. The project has 

potential emissions of CO2e, including fugitive emission from the natural gas lines and circuit breakers, in excess 

of 500,000 tpy. Since construction did not begin before these new regulations became effective, the permittee is 

now required to evaluate PSD/BACT for CO2e emissions from the source.

The CO2e BACT analysis submitted by the permittee is based on the March 2011 EPA guidance document for 

bioenergy production titled “Guidance for Determining Best Available Control Technology for Reducing Carbon 

Dioxide Emissions from Bioenergy Production”. This document along with the traditional 5-step top-down 

approach is the basis for this analysis.

I. BACT for fugitive Greenhouse Gas (GHG) emissions.

There are several potential sources of fugitive Greenhouse Gas (GHG) emissions outside of the combustion 

process for this source that have high global warming potentials. Sulfur hexafluouride (SF6) is used as a 

dielectric insulator and arc quenching medium in modern circuit breakers. The natural gas supply line, pumps 

and valves will also have fugitive (CH4) emissions associated with this project. The emissions from these 

compounds would be relatively small when compared to the GHG emissions resulting from the combustion 

process accounting for less than 0.003% of the total CO2e emissions for this source and should be considered de 

minimis.

Montville Power has determined that it will not need to install a new circuit breaker for the project at this time. If 

during the final design it is determined that a new circuit breaker will be installed Montville power will 

implement measures to minimize fugitive SF6 emissions by the use of a state-of-the-art enclosed pressure circuit 

breaker with leak detection to maintain SF6 emissions to less than 0.5%/year (by weight). Montville Power has 

estimated that the CO2e emissions from this type of circuit breaker to be 6 tpy.

The fugitive CH4 emissions exist for all natural gas pipelines and preventative leak detection and maintenance 

should be considered BACT for these emissions. Montville Power has an existing pipeline safety program 

consisting of visual inspections on a monthly basis and an annual leak detection analysis which is done by an 

outside vendor. The estimated fugitive CO2e emissions from the natural gas piping components are 10.9 tpy.

The fugitive emission are de minimis, approximately 0.003% of the total CO2e emissions for the project, when 

compared to the combustion greenhouse gases. The above best management practices have been determined to 

be BACT for these sources and no further analysis is required. The permit shall be revised to include these best 

management practices and all fugitive emissions will be included in an annual CO2e emissions limitation.

II. BACT for Greenhouse Gas Emissions from Combustion

1. The permittee identified three potential BACT options for CO2e emissions:

Biomass only as a renewable energy source

Energy Efficiency improvements

Carbon capture and sequestration
Montville Power LLC BACT Recertification 2012

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A. Biomass as BACT: 

On January 12, 2011 EPA announced that they were deferring GHG permitting for industries that use 

biomass as they are evaluating whether or not biomass is “carbon neutral” and how the emissions from these 

sources should be accounted for. The Connecticut regulations promulgated in January 2011 did not exempt 

biomass sources from GHG permitting. Based on the state’s current regulation requirements there is no 

presumption that biomass is “carbon neutral” or BACT for CO2e emissions and the Department therefore 

rejects biomass only as BACT.

B. Energy Efficiency Measures: 

The permittee has identified several options to increase the overall plant efficiency to include the following:

Replacement of the existing continuous fin economizer with a bare-tube in-line economizer which is 

more appropriate for biomass firing. 

Removal of a portion of the low temperature superheater (LTSH) in order to prevent overheating of the 

tubes in the LTSH, to insure proper heating of the steam for the turbine, proper cooling of the flue gas 

and to meet ASME code. 

Conversion of the existing air soot blower system to a steam soot blowing system and;

Replacement of the air heater baskets with new baskets more appropriately designed for biomass firing.

C. Carbon Capture and Sequestration: 

Using Carbon Capture and Sequestration (CCS) would actually remove the CO2 from the exhaust stream and 

transport the captured gas to be stored in underground geological formations deemed suitable to retain the 

CO2. Currently the only underground formations that have been considered to be adequate for underground 

sequestration are deep saline formations, un-mineable coal seams, oil and gas reservoirs, organic rich shale 

and basalt formations.

2. Technical feasibility of the identified options:

A. Energy Efficiency Measures

The identified energy efficiency measures are technically feasible and will increase the heat transfer 

ability for the plant and will also increase the overall plant efficiency for all modes of operation. These 

efficiency measures were incorporated into the original proposed modification but would not be 

implemented unless the project was to be constructed. The modified unit was originally designed to 

operate on biomass and fossil fuels to be as efficient as possible for each fuel. Also as noted in the 

previous section this modification results in decreased criteria pollutant emissions while firing fossil 

fuels.

B. Carbon Capture and Sequestration (CCS)

The primary technical challenges to carbon capture in a boiler with flue gas characteristics like this unit

are low CO2 concentrations and high O2 concentrations in the flue gas. There is currently limited minor 

scale carbon capture systems operating for similar plants and no known full scale carbon capture systems 

operating for biomass plants at this time. 

Even if carbon capture were technically feasible at this time, sequestration options are limited as the 

geologic conditions in New England do not allow for long term storage of CO2. The US Department of 

Energy’s 2010 Carbon Sequestration Atlas, 3rd Edition (the “Atlas”) identifies seven separate carbon 

sequestration partnerships. None of the New England states are included in any of the partnerships. The 
Montville Power LLC BACT Recertification 2012

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Atlas also estimates the sequestration potential for all of the New England states as minimal to zero or not 

having been assessed for sequestration potential.

Since there are no full scale carbon capture applications currently operating and that there is no suitable

CO2 storage sites available in the immediate area for sequestration, CCS not considered technically 

feasible at this time.

3. Ranking of the remaining control technologies:

Energy efficiency measures are the only remaining control technology and will be discussed further in Steps 

4 and 5 below.

4. Evaluation of the most effective controls:

The use of additional energy efficiency measures to increase heat transfer properties during biomass firing 

has been determined to be the most effective control for the proposed project and are discussed below:

By replacing the existing continuous fin economizer with a bare-tube in-line economizer which is more 

appropriate for biomass firing it will increase the flue gas outlet temperature for the regenerative selective 

catalytic reduction system (RSCR) operation. The flue gas must remain within a certain operating range 

to meet the NOx emissions limit in the permit. If the flue gas temperature were to drop to below the 

minimum operating temperature, additional heat would need to be added to the flue gas reducing plant 

efficiency. 

The existing LTSH is configured only for fossil fuel firing and not for biomass. Removal of a portion of 

the low temperature superheater (LTSH) will prevent overheating of the tubes in the LTSH and insure 

proper heating of the steam for the turbine, proper cooling of the flue gas and to meet ASME code. 

Conversion of the existing air soot blower system to a steam soot blowing system which will be more 

effective to remove the larger and harder to remove particulates that will be found in the fireside heat 

absorption surfaces., and;

Replacement of the air heater baskets with new baskets more appropriately designed for biomass firing to 

increase heat transfer efficiency to the combustion air used in the boiler.

The permittee detailed the above energy efficiency measures in their August 12, 2012 electronic mail to the 

Department. 

5. Permittee’s Selection of BACT:

The RACT/BACT/LAER Clearinghouse was reviewed to determine CO2 BACT decisions for similar 

projects throughout the country. Beaver Wood Energy Fair Haven LLC to be located in Rutland, VT is the 

only biomass boiler with a CO2 limitation listed in the clearinghouse. The Vermont project would be a new 

482 MMBtu/hr wood fired boiler that has not begun construction. The permittee identified several issues 

with the Vermont project when compared to their project. The differences between the projects will be 

discussed below. Given these differences the permittee has proposed a combination of energy efficiency 

measures, an enforceable numerical heat rate value and an annual limit on CO2e emissions as BACT.

A. The permittee has proposed physical modifications to the existing equipment that will increase the 

overall efficiency of the unit for all firing methods. The project has been designed to achieve the highest 

efficiency possible in order to minimize fuel use and pollutant emissions for both fossil fuel firing (82 

MW) and biomass firing (40 MW). Without these changes the efficiency of the boiler while firing 

biomass would be decreased.
Montville Power LLC BACT Recertification 2012

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B. The permittee has proposed using heat rate as the method of determining actual thermal efficiency of the 

unit expressed as BTU/kW-hr. The permittee estimated the thermal efficiency for the unit on a worst 

case basis for each fuel, Table 1 of the submitted BACT analysis, using a Thermoflex model. (see 

attachment) The actual heat input will be determined using CEMS for each fuel. There are several 

methods that can be used to determine the heat input of the biomass and the permittee has requested that 

they have the option to decide on a methodology before actual commercial operation begins.

The permittee proposed to adjust the predicted Thermoflex heat rates to account for actual design, 

construction and operation variables of the unit. A design variable of 5% was used to account for 

changes between the preliminary designing stages through actual construction of the plant. An 

operations variable of 15% was used to account for actual plant performance that will occur between 

major equipment overhauls. The operations variable also includes a correction for the CO2e emission 

rates based on the expected type of fuel versus the default biomass CO2e emission rates found in 40 CFR 

98. 

Based on the above information the permittee initially proposed the following energy efficiency and numerical 

limitations as CO2e BACT for the unit:

1. Proposed energy efficiency measures as discussed above.

2. A limit for the “allowable heat rate” to determine the plant efficiency to be calculated by the following 

equation:

The sum of [(percent biomass heat input) x (17,448 Btu/kWh)] + [(percent natural gas input) x (13,594 

Btu/kWh)] + [(percent ULSD heat input) x 12,828 Btu/kWh)]; and 

(Note: The heat rates for each fuel represent an actual measure of plant efficiency for that mode of 

operation and are to be considered an enforceable condition in the permit)

3. An annual allowable CO2e limit of 556,012 tons/yr to be calculated by the following equation:

The sum of [(biomass annual heat input) x 211.14 lb/MMBtu)] + [(natural gas annual heat input) x 117 

lb/MMbtu)] + [(ULSD annual heat input) x 163.6 lb/MMBtu)]/2000

Department’s CO2e BACT Determination

In reviewing the submitted BACT analysis the Department has determined that the Beaver Wood Energy Fair 

Haven, LLC plant in Vermont is the only similar project listed in the RACT/BACT/LAER Clearinghouse with a 

CO2 BACT limitation at this time. The Department identified one other one additional source, WE Energies 

located in Wisconsin, which has a permit limit of 3,120 lbs-CO2/MW-hr. Construction has begun and the plant is 

expected to be operational in late 2013. 

The Department requested that the permittee evaluate the Wisconsin project on July 12, 2012 and the permittee 

responded to that request on August 1, 2012.

The Department has confirmed that these are the only two comparable biomass plants with a CO2 limitation in 

their permits and they are discussed below.

 

A. The Beaver Wood permit has incorporated CO2e BACT to include the following:

Implementing energy efficiency, good operating and maintenance practices,

An emission limitation of 2,993 lb-CO2e/MW-hr on a 30-day rolling average. 

The use of a CO2 CEMS to record actual CO2 emissions. CO2e emissions will be calculated using the 
Montville Power LLC BACT Recertification 2012

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default CH4 and N2O emission factors found in 40 CFR Part 98, Subpart C, Table C-2 and the global 

warming potentials found in 40 CFR Part 98, Subpart A, Table A-1.

B. The WE Energies permit has incorporated CO2e BACT to include the following:

An emission limitation of 3,120 lb-CO2e/MW-hr over any consecutive 12-month period. 

The use of a CO2 CEMS to record actual CO2 emissions. No information on how or if CH4 and N2O 

emissions will be calculated.

It is important to note that neither of these two projects has been constructed at this time and that compliance with 

the emission limit or averaging times have not been verified. (see electronic mails from Steve Snook, Vermont 

Air Pollution Control Division concerning the Beaver Wood project, dated 04/24/12 and 07/10/12)

Montville Power has proposed energy efficiency measures and monitoring of the heat rate as a control option to 

reduce CO2 emissions. The main difference in Montville Power’s BACT proposal compared to the other two 

identified projects is that Montville has proposed a heat rate limit (Btu/kW–hr) rather than a mass emission rate 

(lb-CO2e/MW-hr) limitation. The use of heat rate as a limitation on CO2 emissions is a superior method of 

controlling emissions than using a mass emission rate because plant efficiency directly affects CO2 emissions. If 

a mass emission rate were determined to be BACT for CO2, over time the plant’s efficiency would degrade and 

the annual allowable CO2 limit would be attained at a much faster rate, limiting the plant’s ability to meet 

electrical obligations to the grid on an annual basis.

Since Montville Power did not propose a short term mass emission limitation in lb-CO2e/MW-hr their proposed 

heat rate of 17,448 Btu/kW-hr was converted to a mass emission rate and it equates to 3,792 lbs-CO2/MW-hr. 

While this is almost 27% higher than the Beaver Wood project there are significant differences in the “units of 

measure” and they are discussed below:

As discussed earlier in the criteria pollutant BACT analysis, the Beaver Wood project is a new, 

unconstructed source and not a modified existing source as the Montville Project. There are unknowns 

concerning what the actual emissions for the Montville project will be because the project entails 

modifying a conventional gas/oil fired boiler to a solid fuel stoker boiler with a net electrical output of 42 

MW, along with keeping the ability to fire limited fossil fuel at 82 MW. The current Montville NSR 

permit requires the permittee to track and evaluate the criteria and HAP emissions over the first year of 

operation and determine if revised emissions are needed for any pollutants. This analysis was required

because while BACT/PSD/LAER limits are incorporated into the permit there was and still is limited 

operational information for a unit like Montville’s project. The same methodology to track the traditional 

pollutants should be included in the permit for any CO2e limitations that are determined to be BACT for 

the project.

Another significant difference in the projects is the ability for Beaver Wood to show compliance with 

their short term CO2e emission rate and averaging time. The Beaver Wood emission rate is essentially 

based on the default emission factors found in 40 CFR Part 98 with no consideration for design 

variations or plant efficiency loss between overhauls. The plant degradation variable has been used and 

approved in recent combined cycle CO2BACT analysis and should be considered in determining BACT 

for the Montville project. 
Montville Power LLC BACT Recertification 2012

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Montville Power has identified that electrical output may vary approximately 2.5% from summer to 

winter which would affect their ability to meet a 30-day rolling average (see May7, 2012 BACT 

submittal, Table 1). Beaver Wood’s 30-day rolling average is a stringent averaging time and because 

there was no consideration for seasonal environmental conditions for their BACT determination, 

specifically ambient temperatures, a similar averaging time may not be appropriate for the Montville 

project. Many of the recent combined cycle CO2BACT analyses have set much longer averaging times 

and similar averaging times would be more applicable to Montville’s project. For these reasons, the 

Beaver Wood CO2 limitations should be dismissed as BACT.

When comparing the higher mass emission rate for Montville to the Wisconsin projects rates all of the 

parameters need to be normalized between the projects include using the same electrical output (gross vs. 

net), heat rate base on same load, moisture content of the fuel, same design variable adjustment, and 

consideration of the CO2 lb/MMBtu emission rates.

The permittee has detailed these differences in their August 1, 2012 submittal to the Department. After 

re-calculating the mass emission rates to make the two analysis equitable, the Montville project has an 

emission rate about 4% higher, 2,806 lbs/MW-hr vs. the WE Energies project emission rate of 2,700 

lbs/MW-hr. These rates are based on the following assumptions:

1. heat rate based on gross electrical output.

2. heat rate based on 100% load over any consecutive 12-month period averaging time. 

3. heat rate based on 35% moisture in the fuel

4. no design or operational variables applied to the heat rate or emission rate

5. emission rate based on 225.4 lb/MMBtu

After reviewing the above information, Montville Power revised their August 2012 CO2 BACT to include the 

following:

1. Proposed energy efficiency measures as discussed earlier.

2. A limit for the “allowable heat rate” to determine the plant efficiency to be calculated by the 

following equation:

The sum of [(percent biomass heat input) x (15,564 Btu/kWh (gross)] + [(percent natural gas input) 

x (11,963 Btu/kWh)(gross)] + [(percent ULSD heat input) x 11,769 Btu/kWh)(gross)]; and 

(Note: The heat rates for each fuel represent an actual measure of plant efficiency for that mode 

of operation and are to be considered an enforceable condition in the permit)

3. An annual allowable CO2e limit of 590,104 tons/yr to be calculated by the following equation:

The sum of [CO2 CEM data] + [(natural gas annual heat input) x 117 lb/MMbtu)] + [(ULSD 

annual heat input) x 163.6 lb/MMBtu)]/2000

Montville Power did not propose to use a CO2 CEM as was required in the other biomass projects. EPA 

has generally commented in previous combined cycle CO2 BACT reviews that a CO2 CEMS should be 

required as it is a direct measure of CO2 in the flue gas. The default emission factors found in 40 CFR 

Part 98 can then be used for CH4 and N2O to calculate the total CO2e as these emissions typically are less 

than 2% of the total emissions and can be considered de minimis. Using a CO2 CEMS will provide the 

most accurate measure of annual emissions and should be considered as a compliance method for the 

Montville project.
Montville Power LLC BACT Recertification 2012

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GHG BACT Recommendation:

Based on the information submitted by permittee, the Department’s review and verification of recent BACT 

reviews for similar biomass plants, staff recommends that the following CO2e limitations are BACT for this 

source:

The proposed energy efficiency methods discussed above, along with good operating and maintenance 

practices. Montville Energy shall submit to the Department documentation certifying that the energy 

efficiency methods have been incorporated into the plant at least 60-days prior to commencement of 

commercial operation. [Note: good operating and maintenance practices will not necessarily reduce 

CO2 emissions but will aid in the assurance that the plant is being operated properly. The current 

permit requires that the permittee develop a operating and maintenance plan (O&M) according to the 

manufacturer’s specifications and written recommendations and these practices will incorporated into 

the plan.]

An enforceable heat rate of 15,564 Btu/kW-hr (gross) with a rolling 12-month averaging period. Heat 

input will be monitored by CEMS and the methodology to be used shall be acceptable to the department

and the permittee. Gross electrical output will be the sum of the hourly data as metered by the station.

An enforceable annual CO2e limit of 590,104 tons/yr. 

Installation a CO2 CEMS to measure actual annual emissions. The default emission factors found in 40 

CFR Part 98 will be used to calculate CH4 and N2O emissions from the combustion process and then 

added to the CEMS data to calculate the total annual CO2e emissions. Included in the annual CO2e 

emission limit shall be any estimated fugitive emissions from the SF6 insulated electrical equipment and 

the natural gas piping components. Additional monitoring and record keeping shall be required for the 

fugitive GHG emissions in NSR permit. The preventive measures for any fugitive CO2e emissions shall 

be included in the facilities O&M Plan. The conditions of the O&M plan will be specified in the 

modified permit and will be considered to be an enforceable condition. The permittee will also track and 

evaluate the heat rate of the unit and CO2e emissions over the first year of operation for all modes of 

operation and evaluate the need to revise the operating limits, design/operational variables and averaging 

periods at that time. The permittee shall be required to submit a report of this data which supports their 

conclusions for further permit modification.

Montville Power shall submit a non-minor modification application for NSR permit number 107-0056 to 

incorporate the above changes into the NSR permit pursuant to RCSA Sections 22a-174-3a(a)(1)(J) and -

2a(d)(4)(A) within 60-days of receipt of this BACT approval. 

A compliance review consistent with the DEEP Environmental Compliance History Policy was performed as part 

of this BACT review. The compliance history review using the SIMS Enforcement database was conducted 

along with a review of air program compliance as reported by the Compliance and Field Operations Section of 

the Bureau of Air Management. Also, a review of the agency wide compliance information form submitted by the 

applicant was conducted in order to assess compliance with environmental laws within the past five years.

James Grillo, APCE Date

REVIEW:

 

Kiernan Wholean Richard A. Pirolli

Supervising APCE Assistant Director 

October 9, 2012

Ms. Cynthia L. Karlic

Regional Environmental Director

NRG Energy, Inc.

1866 River Road

Middletown, CT 06457

RE: BACT Recertification for Montville Power LLC

Dear Ms Karlic:

The Department of Energy and Environmental Protection ("the Department") has reviewed the Best Available 

Control Technology (BACT) recertification package, submitted by Montville Power LLC on August 30, 2011, 

May 7, 2012 and August 1, 2012 as required by New Source Review (NSR) permit number 107-0056. The 

Department has determined that the BACT analysis for the criteria pollutants is acceptable and no further action

is required by Montville Power with respect to these pollutants at this time. While the Department has 

determined the proposed limits and energy efficiency improvements are BACT for the CO2e emissions, additional 

monitoring, record keeping and reporting requirements need to be incorporated into the permit, consistent with 

the findings made in the attached technical analysis.

Montville Power LLC shall submit a non-minor permit modification for permit number 107-0056 to incorporate 

the CO2e BACT requirements in accordance with the Regulations of Connecticut State Agencies (RCSA) Section 

22a-174-2a(d) within 60-days of receipt of this letter. The Department will require a public notice of the nonminor modification to permit number 107-0056 and will take public comment only on the sections of the permit 

concerning the incorporation of the updated BACT requirements.

Pursuant to RCSA Section 22a-3a-2(e), nothing in this notice shall be deemed to preclude the Department from 

requesting additional information on any applications submitted. During technical review, it is not uncommon 

for questions to arise that require additional information to resolve. The Department will make every effort to 

work with you to resolve any such issues. Your prompt response to any requests for additional information will 

expedite the processing of your applications.

This letter in no way grants immunity from legal action resulting from the failure of this source to remain in 

compliance with existing air pollution regulations, nor does it provide an exemption from compliance with future 

Federal, State or local laws.

If you have any questions concerning this notice, please contact Mr. James Grillo at (860) 424-4152.

Sincerely,

Gary S. Rose

Director

Engineering and Enforcement Division

Bureau of Air Management

GSR:jag

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