Document ID: EPA-HQ-OAR-2009-0734-0005
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2014-02-03T05:00Z

MEMORANDUM

DATE: 	February 15, 2013

SUBJECT:	Estimated Emissions from Wood Heaters

FROM:	Jill Mozier, EC/R Inc.
      Beth Friedman, EC/R Inc.

TO:		Gil Wood, EPA/OAQPS
		David Cole, EPA/OAQPS

	The purpose of this memorandum is to present an estimate of the fine particulate matter (PM2.5), volatile organic compound (VOC) and carbon monoxide (CO) emissions from wood heater appliances based on projected sales of new units and based on emissions under the proposed NSPS, as well as under an alternative regulatory option being considered for comment.

   I. PM Methodology

      A. 	Estimating Average Emissions per Appliance	
	We used the EPA Residential Wood Combustion (RWC) emission estimation tool, which is an Access(TM) database that compiles nationwide RWC emissions using county level, process specific data and calculations.  We summed the nationwide number of appliances and total tons of wood burned for each of the relevant emission inventory categories (Table 1) in the inventory.  

               Table 1.  RWC Emission Inventory Categories Used
                                       
Woodstove: fireplace inserts; EPA certified; non-catalytic
Woodstove: fireplace inserts; EPA certified; catalytic
Woodstove: freestanding, EPA certified, non-catalytic
Woodstove: freestanding, EPA certified, catalytic
Woodstove: pellet-fired, general
Woodstove: freestanding, non-EPA certified
Hydronic heater: outdoor
Furnaces:  indoor, cordwood

	We then made some adjustments/assumptions to the baseline RWC inventory.  First, we deleted data in the RWC for non-certified stoves and inserts, as these cannot be sold.  With the exception of wood stoves, we applied the PM2.5 emission factors for each class to the total tons of wood burned and calculated an average emission rate/appliance/category.  In the case of wood stoves, the RWC used an average of all PM10 AP-42 emission factors for wood stoves. The RWC assumes that PM10 and PM2.5 factors are identical.  At a minimum, we believe that all new wood stoves meet the AP-42 PM10 emission factors for "Phase II" stoves (the current NSPS promulgated in 1988).  As described below, we went a step further and assumed that all new shipments will meet the current Washington State limits, which are approximately 40 percent less than the 1988 NSPS.

	Second, we assumed that outdoor hydronic heaters and indoor hydronic heaters have the same emission profile.

	Single burn rate stoves are not included in the RWC as separate identifiable units.  We assumed that they would have the same baseline emission factor as freestanding non-certified woodstoves, i.e., 30.6 lb/ton of wood burned.  We used the average tons burned per appliance factor as representative of these stoves as well. 
 
	Masonry heaters are not included in the RWC database.  Therefore, we were not able to estimate emissions from these appliances for the purpose of this analysis.

	We used this subset of the RWC database to calculate a baseline average emission rate/appliance (or "emission inventory category"), including an adjustment of the RWC emission factor to the current Washington State limits where warranted.  We multiplied the total tons of wood burned for the appliance by the RWC emission factor (adjusted as appropriate) to calculate the total tons of PM2.5 emissions.  We divided this value by the number of appliances in the category to calculate the baseline average PM2.5 emissions per individual appliance (Table 2).

            Table 2.  PM2.5 Tons per Appliance Estimate (Baseline)

                          Emission Inventory Category
                                   Pollutant
                       Baseline Emission factor (lb/ton)
                               Emissions (tons)
                             Tons per appliance/yr
Woodstove: fireplace inserts; EPA certified; non-catalytic
Primary PM2.5
                                     8.76
                                     5,371
                                    0.0041
Woodstove: fireplace inserts; EPA certified; catalytic
Primary PM2.5
                                     9.72
                                     2,023
                                    0.0047
Woodstove: freestanding, EPA certified, non-catalytic
Primary PM2.5
                                     8.76
                                     6,745
                                    0.0077
Woodstove: freestanding, EPA certified, catalytic
Primary PM2.5
                                     9.72
                                     3,769
                                    0.0101
Woodstove: pellet-fired, general
Primary PM2.5
                                     3.06
                                     1,798
                                    0.0021
Woodstove: freestanding, non-EPA certified*
Primary PM2.5
                                     30.6
                                    71,424
                                    0.0324
Hydronic heater: outdoor/indoor
Primary PM2.5
                                     27.6
                                    50,427
                                    0.1383
Furnace: indoor, cordwood
Primary PM2.5
                                     27.6
                                     2,471
                                    0.0582
*Non-EPA certified wood stove emission factor and tons/appliance were used to represent single burn rate stoves.	
      
      The next step was to develop emission factors representing the proposed NSPS, as well as an alternative approach considered.  The NSPS options examined in this analysis ("proposal" and "alternative") are based on phased-in compliance dates, or "steps", for subcategories of appliances.  Proposed Subpart AAA will regulate "room heaters" and includes adjustable burn rate stoves, single burn rate stoves, and pellet stoves.  Proposed Subpart QQQQ will regulate "central heaters" and includes outdoor and indoor hydronic heaters and forced air furnaces. Proposed Subpart RRRR will regulate masonry heaters.  Following is a summary of the current NSPS implementation assumptions for appliances within the subcategories under both the proposal and the alternative.  The proposal is a 2-step standard with compliance dates of 2014 and 2019.  The alternative is a 3-step standard with compliance dates of 2014, 2017, and 2022. 
       
Subpart AAA ("room heaters"):  

      * Adjustable burn rate, single burn rate, and pellet stoves:  Proposal: Step 1 limit of 4.5 g/hr upon promulgation in 2014; and Step 2 limit of 1.3 g/hr five years after promulgation in 2019.  Alternative: Step 1 limit of 4.5 g/hr upon promulgation in 2014; Step 2 limit of 2.5 g/hr three years after promulgation in 2017; and Step 3 limit of 1.3 g/hr eight years after promulgation in 2022.  Note: The Step 1 limit is the 1995 Washington State standard for non-catalytic stoves; the Alternative Step 2 limit is the 1995 Washington State standard for catalytic stoves; and the proposed Step 2 (Alternative Step 3) limit is already met by the top performing catalytic, non-catalytic and pellet stove models, according to industry data. Although previously unregulated and a less developed technology than adjustable burn rate stoves, single burn rate stove designs have been undergoing R&D in anticipation of the proposed NSPS and cleaner designs are nearly market-ready.
Subpart QQQQ ("central heaters"):

      * Hydronic heaters (both outdoor and indoor):  Proposal: Step 1 limit of 0.32 lb/mm BTU heat output upon promulgation in 2014; and Step 2 limit of 0.06 lb/mm BTU heat output five years after promulgation in 2019.  Alternative: Step 1 limit of 0.32 lb/mm BTU heat output upon promulgation in 2014; Step 2 limit of 0.15 lb/mm BTU heat output three years after promulgation in 2017; and Step 3 limit of 0.06 lb/mm BTU heat output eight years after promulgation in 2022.  Note: The Step 1 limit is the EPA "Phase 2 " voluntary program limit already met by 36 hydronic heater models (27 cord wood and 9 pellet models) built by 17 U.S. manufacturers; the Alternative Step 2 limit is already met by 11 hydronic heater models (6 cord wood and 5 pellet models) built by 6 U.S. manufacturers; and the proposed Step 2 (Alternative Step 3) limit is already met by 4 hydronic heater models (2 cord wood and 2 pellet models) built by 2 U.S. manufacturers, as well as over 100 European manufacturers per test method EN 303-05. 

      * Forced Air Furnaces:  Proposal: Step 1 limit of 0.93 lb/mm BTU heat output upon promulgation in 2014; and Step 2 limit of 0.06 lb/mm BTU heat output five years after promulgation in 2019.  Alternative: Step 1 limit of 0.93 lb/mm BTU heat output upon promulgation in 2014; Step 2 limit of 0.15 lb/mm BTU heat output three years after promulgation in 2017; and Step 3 limit of 0.06 lb/mm BTU heat output eight years after promulgation in 2022.  Note: The Step 1 limit is based on test data from development of Canadian standard B415.1-10 and conversation with industry regarding cleaner forced air furnace models currently being tested in R&D.  Forced air furnace designs able to meet the Alternative Step 2 and proposed Step 2 (Alternative Step 3) limits may be based on technology transferred from hydronic heater designs. 
Subpart RRRR including masonry heaters:

      * Masonry Heaters:  Proposal / Alternative (same): Step 1 limit of 0.32 lb/mm BTU heat output upon promulgation in 2014 for large manufacturers (defined as manufacturers constructing >= 15 masonry heaters per year), with a 5-year (2019) small volume manufacturer compliance extension (for companies constructing < 15 units/year).  No other phased-in limits are being proposed.  Note: Based on data submitted by the Masonry Heater Association, over 10 models already meet this limit.
	We developed adjusted emission factors to reflect the proposed and alternative limits discussed above, which were then used to calculate new average tons of emissions per appliance for each RWC appliance type in Tables 1 and 2.  Adjustments were assumed for NSPS emission factors (as noted below) in order to not over state emission reductions under the proposal and alternative; actual emission reductions may be greater than reductions resulting from our emission factor adjustments for the purpose of this analysis.  Following is a description of how the RWC factors were adjusted for each appliance type:

      * Woodstove: all EPA certified.  As noted above, we determined the ratio of emissions between the existing 1988 NSPS limits compared to the Washington state standards.   For both catalytic and non-catalytic devices, the Washington standard is 60% of the 1988 NSPS.  We assumed this same ratio would apply to the emission factors and multiplied the RWC emission factor by 60%.  We used these adjusted RWC emission factors (shown in Table 2) as both baseline and Step 1 emission factors for catalytic and non-catalytic stoves.  We made the assumption (in terms of estimating potential emission reductions) that the Step 1  emission factor was the same as the baseline emission factor, because nearly all current wood stove models already meet the Step 1  limit according to industry data. We also assumed that the Alternative Step 2 emission factor for catalytic stoves was the same as the baseline and Step 1 emission factor because approximately 90% of the current catalytic models already meet the Alternative Step 2 limit, according to industry data.[10] For the Alternative Step 2 emission factor for non-catalytic models, we scaled the Step 1 emission factor by the ratio of the Alternative Step 2 standard to the Step 1 standard (or 2.5/4.5 = 0.55).  Likewise, for the proposed Step 2 (Alternative Step 3) emission factor for both catalytic and non-catalytic models, we scaled the Alternative Step 2 emission factor by the ratio of the proposed Step 2 (Alternative Step 3) standard to the Alternative Step 2 standard (or 1.3/2.5 = 0.52).  For consistency with our shipment data (described in section B) and because the RWC database provides four separate emission factors for catalytic and non-catalytic, freestanding models and fireplace inserts, we used the weighted average value for all four wood stove types to represent the total population of adjustable burn rate woodstoves.  Finally, we multiplied the resulting emission factors by the total tons burned for the appliance type (provided by the RWC database) and then divided that by the appliance population (also provided by the RWC database) to derive the tons/appliance of PM2.5 emissions. The emission factors and tons/appliance are shown in the green rows in Table 3. 
      * Woodstove:  pellet fired, general. We used the RWC emission factor shown in Table 2 as both the baseline and Step 1 emission factor for pellet stoves because nearly all current pellet stove models already meet the Step 1 standard according to industry data. Furthermore, the RWC emission factor for pellet stoves is quite low compared to other appliances, which leaves little room to adjust the factor.  For the Alternative Step 2 emission factor, we reduced the Baseline/Step 1 emission factor by only 10%, based on industry data[11] that most pellet models (80%) already meet the Alternative Step 2 level.  For the proposed Step 2 (Alternative Step 3) emission factor, we scaled the Alternative Step 2 emission factor by the ratio of the proposed Step 2 (Alternative Step 3) standard to the Alternative Step 2 standard (or 1.3/2.5 = 0.52).  We multiplied the resulting emission factors by the total tons burned for pellet stoves and then divided that by the pellet stove appliance population to derive the tons/appliance of PM2.5 emissions.  The emission factors and tons/appliance are shown in the orange row in Table 3. 
      * Woodstove: freestanding, non-EPA certified (single burn rate stoves). As described above, we assumed that the freestanding non-EPA certified woodstove emission inventory category includes the population of single burn rate stoves.  We therefore used the RWC emission factor for freestanding non-EPA certified woodstoves (30.6 lb/ton) as the baseline emission factor for single burn rate stoves.  For the Step 1 emission factor, we used the same emission factor as a certified non-catalytic stove meeting the Washington state standards (i.e., 8.76 lb/ton) because the same standard is being proposed for single burn rate stoves as for adjustable burn rate stoves. Likewise, we used the same emission factors used for non-catalytic stoves for the Alternative Step 2 and proposed Step 2 (Alternative Step 3) emission factors.  We multiplied the resulting emission factors by the total tons burned for this appliance category and then divided that by the appliance population to derive the tons/appliance of PM2.5 emissions.  The emission factors and tons/appliance are shown in the grey row in Table 3. 
      * Hydronic heater:  outdoor/indoor.  As noted above, we assumed that indoor hydronic heaters (a minority of the hydronic heater population) have the same emission profile as the outdoor hydronic heater appliance category provided in the RWC.  According to the EPA voluntary hydronic heater program, the "Phase 2" heaters that are presumed to represent the Step 1 limit are 90% cleaner than older unqualified units. We assume that the majority of the existing inventory is represented by these unqualified units, and applied a 90% reduction to the RWC baseline emission factor shown in Table 2 (27.6 lb/ton) in order to derive the Step 1 emission factor (of 2.76 lb/ton).  For the Alternative Step 2 emission factor, we assumed a 50% reduction in the Step 1 emission factor since the Alternative Step 2 limit is approximately 50% of the Step 1 limit.  Likewise, for the proposed Step 2 (Alternative Step 3) emission factor, we scaled the Alternative Step 2 emission factor by the ratio of the proposed Step 2 (Alternative Step 3) standard to the Alternative Step 2 standard (or 0.06/0.15 = 0.40).  We multiplied the resulting emission factors by the total tons burned for the hydronic heater RWC appliance category and then divided that by the hydronic heater appliance population to derive the tons/appliance of PM2.5 emissions.  The emission factors and tons/appliance are shown in the blue row in Table 3. 
      * Furnace: indoor, cordwood.  We used the RWC emission factor shown in Table 2 (27.6 lb/ton) as the baseline emission factor.  For Step 1, we scaled the baseline emission factor by 75% (to 6.9 lb/ton) because background material provided in the Canadian standards review process stated that that the emission limit associated with this method would results in an approximately 75% reduction in emissions compared to a non-qualifying furnace. The Alternative Step 2 and proposed Step 2 (Alternative Step 3) limits of 0.15 lb/mmBTU and 0.06 lb/mmBTU, respectively, are the same as the hydronic heater limits.  The baseline emission factors for each appliance category are also the same.  Therefore we used the same Alternative Step 2 and proposed Step 2 (Alternative Step 3) emission factors used for hydronic heaters (1.38 lb/ton and 0.55 lb/ton, respectively).  We multiplied the emission factors by the total tons burned for the cordwood furnace RWC appliance category and then divided that by the furnace appliance population to derive the tons/appliance of PM2.5 emissions.  The emission factors and tons/appliance are shown in the lavender row in Table 3.  
      Table 3 shows the baseline, Step 1, Alternative Step 2, and proposed Step 2 (Alternative Step 3) emission factors for each appliance type resulting from our assumptions and adjustments described above.  We used the appropriate tons/appliance with annual shipment data (Section B) to estimate annual PM2.5 emissions (Section C), based on the proposed and alternative phased-in compliance dates. 

                                       
Table 3.  NSPS Adjusted Emission Factors for PM2.5  -  Baseline, Step 1, Alternative Step 2, and Step 2 (Alternative Step 3)
                                       
Emission Inventory Category
                        Baseline Emission factor lb/ton
                              Baseline Tons/appl
                         Step 1 Emission Factor lb/ton
                               Step 1 Tons/appl
                      Alt. Step 2 Emission Factor lb/ton
                             Alt. Step 2 Tons/appl
                                    Step 2
                     (Alt. Step 3) Emission Factor lb/ton
                                    Step 2
                            (Alt. Step 3) Tons/appl
Woodstove: fireplace inserts; EPA certified; non-catalytic
                                     8.76
                                    0.0041
                                     8.76
                                    0.0041
                                     4.82
                                    0.0023
                                     2.51
                                    0.0012
Woodstove: fireplace inserts; EPA certified; catalytic
                                     9.72
                                    0.0047
                                     9.72
                                    0.0047
                                     9.72
                                    0.0047
                                     5.05
                                    0.0025
Woodstove: freestanding, EPA certified, non-catalytic
                                     8.76
                                    0.0077
                                     8.76
                                    0.0077
                                     4.82
                                    0.0042
                                     2.51
                                    0.0022
Woodstove: freestanding, EPA certified, catalytic
                                     9.72
                                    0.0101
                                     9.72
                                    0.0101
                                     9.72
                                    0.0101
                                     5.05
                                    0.0052
Woodstove: pellet-fired, general
                                     3.06
                                    0.0021
                                     3.06
                                    0.0021
                                     2.75
                                    0.0019
                                     1.43
                                    0.0010
Single Burn Rate Stoves (freestanding, non-EPA certified)
                                     30.6
                                    0.0324
                                     8.76
                                    0.0093
                                     4.82
                                    0.0051
                                     2.51
                                    0.0027
Hydronic heater: outdoor
                                     27.6
                                    0.1383
                                     2.76
                                    0.0138
                                     1.38
                                    0.0069
                                     0.55
                                    0.0028
Furnace: indoor, cordwood
                                     27.6
                                    0.1032
                                      6.9
                                    0.0258
                                     1.38
                                    0.0052
                                     0.55
                                    0.0021

                                                                         0.0060
Baseline woodstove weighted average (Tons/appl)
                                                                         0.0060
Step 1 woodstove weighted average (Tons/appl)
                                                                         0.0042
Alternative Step 2 woodstove weighted average (Tons/appl)
                                                                         0.0022
Step 2 (Alternative Step 3) woodstove weighted average (Tons/appl)

      B. 
      C. 	Shipment Data	
	We used data in the Frost & Sullivan Market (F&S) report on 2008 shipments by product category, and F&S revenue forecasts which incorporated the weak economy in years 2009 and 2010, to calculate the reduced number of shipments in years 2009 and 2010. Forced air furnaces were outside the scope of the F&S report.  Instead, we used manufacturer estimates of total industry sales in 2008 and applied the F&S market factors to estimate shipments through 2010. The F&S wood stove numbers included both certified and non-certified stoves, so we estimated numbers of non-certified stove shipments out of the total reported wood stove category (i.e., 40,000 single burn rate stoves shipped in 2008).[15] These shipments were deleted from the total wood stove category shipments.  We expanded the 2008 single burn rate estimate using the F&S factors.  
      
      For years 2011 through 2038 (for the proposed NSPS) and 2011 through 2041 (for the alternative approach) estimated shipments are based on a forecasted revenue growth rate of 2.0%, in keeping with the average annual growth in real GDP predicted by the US Bureau of Economic Analysis.  There is not a perfect correlation between shipments and revenue (for example, because of their higher unit cost, pellet stoves generate more absolute revenue than wood stoves), but we think the overall trend in the projection is reasonable in the absence of specific shipment projections. 	
	
	Table 4 on the next page shows a truncated summary of the shipment data through year 2023. Our cost effectiveness analysis (CE) assumes a 20-year model design lifespan as well as a 20-year use/emitting appliance lifespan.  These assumptions were made to best characterize the actual model design and use lifespans given that many models developed for the 1988 NSPS are still being sold (after 25 years), many "new" models still have the same internal working parts with merely exterior cosmetic changes, and most stoves in consumer homes emit for at least 20 years and often much longer.  Therefore our CE analysis tracks shipments through year 2038 for the proposed NSPS and through year 2041 for the alternative approach (i.e., assuming a 20 year design life for a model meeting the Step 2 limit in year 2019 under the proposed NSPS, and for a model meeting the Alternative Step 3 limit in year 2022 under the alternative approach).  Thus Table 4 is a truncated summary of our actual shipment data which extended through years 2038 for the proposed NSPS and 2041 for the alternative approach. See the CE analysis spreadsheets[17] for the complete shipment data.

      D. 	Estimated PM2.5 Emissions from Shipments of New Appliances	
	As described above, we calculated the average emissions per appliance type using the emission factor for each category multiplied by the inventory value of total tons of wood burned divided by the number of appliances in the inventory population.  This tons/appliance value was then multiplied by the number of shipments to calculate total emissions from each appliance category per year under baseline conditions, i.e., in the absence of an NSPS.
	
	Table 5 on the next page shows a truncated summary of the estimated PM2.5 emissions (in tons) under baseline conditions through year 2023.  We then estimated emissions under the proposed NSPS (Table 6) and under the alternative approach (Table 7) based on the respective assumptions and phase-in timelines for each. Under the proposed NSPS, the Step 1 limit becomes effective in 2014 and the Step 2 limit in 2019; while under the alternative approach, the Step 1 limit becomes effective in 2014, the Step 2 limit in 2017, and the Step 3 limit in 2022. (Note that the proposed Step 2 limit is the same as the alternative Step 3 limit, although the compliance dates differ.)  The emission estimates assume that the total number of shipped units meet the standard in the year the standard is implemented.  

      Tables 5, 6, and 7 show emission estimates out to year 2023 for comparison.  Like Table 4, these are truncated summaries.  Our CE analysis tracks emission reductions out through 2057 for the proposed NSPS and through 2060 for the alternative approach, assuming a 20 year design life for a model meeting each phased-in limit, and assuming that stoves shipped in the 20[th] year of design life will be emitting in homes for another 20 years.  See the CE analysis spreadsheets[17] for all years of emission data, both baseline and under each NSPS scenario.
      
      Cumulative PM2.5 emissions are shown through year 2057 for the proposed NSPS, and through year 2060 for the alternative approach in Tables 8 through 15.  These tables show cumulative emissions under both NSPS scenarios as well as cumulative emission reductions from baseline for both.  Table 8 shows cumulative emissions and emission reductions for appliances regulated under Subpart AAA (a.k.a. "Room Heaters")  -  that is, for wood stoves, pellet stoves, and single burn rate stoves combined.  Tables 9, 10 and 11 show emissions and reductions for the individual appliances regulated under Subpart AAA.  Table 12 shows cumulative emissions and emission reductions for appliances under Subpart QQQQ (a.k.a. "Central Heaters")  -  that is, for forced air furnaces and hydronic heaters.  Tables 13 and 14 show emissions and reductions for the individual appliances regulated under Subpart QQQQ.  Finally, Table 15 shows cumulative emissions and emission reductions for Subparts AAA and QQQQ combined. 
      
      Note: No emission tables are provided for Subpart RRRR regulating masonry heaters because emission estimates are not available for these appliances as explained in Section A.

                                       
                   Table 4.  Estimated Annual Shipped Units

                                          
                                          
                                          
                                       
            Table 5. Estimated PM2.5 Emissions (Tons)  -  Baseline

                                       

                                          
                                          
                                          
                                          
                                       
                                       
                                       
Table 6. Estimated PM2.5 Emissions (Tons)  -  Proposed NSPS (Step 1 in 2014 and Step 2 in 2019)

Table 7. Estimated PM2.5 Emissions (Tons)  -  Alternative Approach (Step 1 in 2014, Step 2 in 2017, and Step 3 in 2022)

                                          
                                          
   Table 8. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                                for Subpart AAA
                                       
                                       
                                       
                                       
   Table 9. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                                for Wood Stoves
                                       
                                       
  Table 10. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                               for Pellet Stoves

                                       
  Table 11. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                          for Single Burn Rate Stoves
                                       
                                       
                                       
                                       
  Table 12. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                               for Subpart QQQQ

                                       
  Table 13. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                            for Forced Air Furnaces

                                       
  Table 14. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                             for Hydronic Heaters 

                                       
  Table 15. Estimated Cumulative PM2.5 Emissions through Appliance Lifespan 
                          for Subparts AAA & QQQQ

                                       
   II. VOC Methodology
      We used the same methodology described in Section I to develop emission estimates for VOC emissions. Using the RWC database, we developed an estimate of VOC emissions per appliance using baseline emission factors.  Then, using the same NSPS phase-in assumptions and anticipated emission reductions (i.e., that VOC reductions are comparable to PM2.5 reductions), we developed emission factors to be used in analyzing the proposed NSPS and the alternative approach. See Table 16.
      
	Next, using the same assumptions as we used for PM2.5, we calculated VOC emissions at baseline and under the proposed NSPS and alternative approach for each stepped limit.  See Tables 17  -  19.

	Finally, cumulative VOC emissions and emission reductions under both the proposed NSPS and alternative approach were calculated based on a 20-year model design lifespan for shipments, as well as a 20-year appliance use lifespan for emissions, as explained in Sections I-B and I-C.  See Tables 20  -  27.

   Note: No emission tables are provided for Subpart RRRR regulating masonry heaters because emission estimates are not available for these appliances as explained in Section A.
   
   III. CO Methodology
	We used the same methodology described in Section I to develop emission estimates for CO emissions. Using the RWC database, we developed an estimate of CO emissions per appliance using baseline emission factors.  Then, using the same NSPS stepped limit assumptions and anticipated emission reductions (i.e., that CO reductions are comparable to PM2.5 reductions), we developed emission factors to be used in analyzing the proposed NSPS and the alternative approach.  See Table 28.
      
      Next, using the same assumptions as we used for PM2.5, we calculated CO emissions at baseline and under the proposed NSPS and alternative approach for each stepped limit.  See Tables 29  -  31.
      
      Finally, cumulative CO emissions and emission reductions under both the proposed NSPS and alternative approach were calculated based on a 20-year model design lifespan for shipments, as well as a 20-year appliance use lifespan for emissions, as explained in Sections I-B and I-C. See Tables 32  -  39.
      
      Note: No emission tables are provided for Subpart RRRR regulating masonry heaters because emission estimates are not available for these appliances as explained in Section A.
Table 16.  NSPS Adjusted Emission Factors for VOC  -  Baseline, Step 1, Alternative Step 2, and Step 2 (Alternative Step 3)
                                       
Emission Inventory Category
Baseline Emission factor lb/ton
Baseline Tons/appl
Step 1 Emission Factor lb/ton
Step 1 Tons/appl
 Alt.
Step 2 Emission Factor lb/ton
Alt.
Step 2 Tons/appl
Step 2
(Alt. Step 3) Emission Factor lb/ton
Step 2 (Alt.    Step 3) Tons/appl
Woodstove: fireplace inserts; EPA certified; non-catalytic
                                      12
                                    0.0056
                                      12
                                    0.0056
                                      6.6
                                    0.0031
                                     3.432
                                    0.0016
Woodstove: fireplace inserts; EPA certified; catalytic
                                      15
                                    0.0073
                                      15
                                    0.0073
                                      15
                                    0.0073
                                     7.800
                                    0.0038
Woodstove: freestanding, EPA certified, non-catalytic
                                      12
                                    0.0106
                                      12
                                    0.0106
                                      6.6
                                    0.0058
                                     3.432
                                    0.0030
Woodstove: freestanding, EPA certified, catalytic
                                      15
                                    0.0155
                                      15
                                    0.0155
                                      15
                                    0.0155
                                     7.800
                                    0.0081
Woodstove: pellet-fired, general
                                     0.041
                                    0.00003
                                     0.041
                                    0.00003
                                     0.037
                                    0.00003
                                     0.019
                                    0.00001
Single Burn Rate Stoves (freestanding, non-EPA certified)
                                      53
                                    0.0561
                                      12
                                    0.0127
                                      6.6
                                    0.0070
                                     3.432
                                    0.0036
Hydronic heater: outdoor
                                     11.7
                                    0.0586
                                     1.17
                                    0.0059
                                     0.59
                                    0.0029
                                     0.234
                                    0.0012
Furnace: indoor, cordwood
                                     11.7
                                    0.0437
                                     2.925
                                    0.0109
                                     0.59
                                    0.0022
                                     0.234
                                    0.0009
0.0086
Baseline woodstove weighted average (Tons/appl)
0.0086
Step 1 woodstove weighted average (Tons/appl)
0.0061
Alternative Step 2 woodstove weighted average (Tons/appl)
0.0032
Step 2 (Alternative Step 3) woodstove weighted average (Tons/appl)
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
             Table 17. Estimated VOC Emissions (Tons)  -  Baseline

                                       
                                       
                                       
Table 18. Estimated VOC Emissions (Tons)  -  Proposed NSPS (Step 1 in 2014 and Step 2 in 2019)
                                       

Table 19. Estimated VOC Emissions (Tons)  -  Alternative Approach (Step 1 in 2014, Step 2 in 2017, and Step 3 in 2022)

   Table 20. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                                for Subpart AAA
                                       
                                       
   Table 21. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                                for Wood Stoves
                                       
                                       
                                       
   Table 22. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                               for Pellet Stoves

                                       
   Table 23. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                          for Single Burn Rate Stoves
                                       
                                       
                                       
   Table 24. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                               for Subpart QQQQ
                                       
                                       
   Table 25. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                            for Forced Air Furnaces

                                       
   Table 26. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                             for Hydronic Heaters

                                       
   Table 27. Estimated Cumulative VOC Emissions through Appliance Lifespan 
                          for Subparts AAA & QQQQ

                                       
                                       

Table 28.  NSPS Adjusted Emission Factors for CO  -  Baseline, Step 1, Alternative Step 2, and Step 2 (Alternative Step 3)
                                       
Emission Inventory Category
Baseline Emission factor lb/ton
Baseline Tons/appl
Step 1 Emission Factor lb/ton
Step 1 Tons/appl
 Alt.
Step 2 Emission Factor lb/ton
Alt.
Step 2 Tons/appl
Step 2
(Alt. Step 3) Emission Factor lb/ton
Step 2 (Alt.    Step 3) Tons/appl
Woodstove: fireplace inserts; EPA certified; non-catalytic
                                     140.8
                                    0.0662
                                     140.8
                                    0.0662
                                     77.4
                                    0.0364
                                    40.269
                                    0.0189
Woodstove: fireplace inserts; EPA certified; catalytic
                                     104.4
                                    0.0509
                                     104.4
                                    0.0509
                                     104.4
                                    0.0509
                                    54.288
                                    0.0264
Woodstove: freestanding, EPA certified, non-catalytic
                                     140.8
                                    0.1241
                                     140.8
                                    0.1241
                                     77.4
                                    0.0683
                                    40.269
                                    0.0355
Woodstove: freestanding, EPA certified, catalytic
                                     104.4
                                    0.1082
                                     104.4
                                    0.1082
                                     104.4
                                    0.1082
                                    54.288
                                    0.0563
Woodstove: pellet-fired, general
                                     15.9
                                    0.0110
                                     15.9
                                    0.0110
                                     14.31
                                    0.0099
                                     7.441
                                    0.0052
Single Burn Rate Stoves (freestanding, non-EPA certified)
                                     230.8
                                    0.2442
                                     140.8
                                    0.1489
                                     77.4
                                    0.0819
                                    40.269
                                    0.0426
Hydronic heater: outdoor
                                      184
                                    0.9222
                                     18.4
                                    0.0922
                                      9.2
                                    0.0461
                                     3.680
                                    0.0184
Furnace: indoor, cordwood
                                      184
                                    0.6878
                                      46
                                    0.1719
                                      9.2
                                    0.0344
                                     3.680
                                    0.0138

                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
0.0863
Baseline woodstove weighted average (Tons/appl)
0.0863
Step 1 woodstove weighted average (Tons/appl)
0.0569
Alternative Step 2 woodstove weighted average (Tons/appl)
0.0296
Step 2 (Alternative Step 3) woodstove weighted average (Tons/appl)

                                       
                                       
                                       
                                       
                                       
                                       
                                       

             Table 29. Estimated CO Emissions (Tons)  -  Baseline

                                       

Table 30. Estimated CO Emissions (Tons)  -  Proposed NSPS (Step 1 in 2014 and Step 2 in 2019)

Table 31. Estimated CO Emissions (Tons)  -  Alternative Approach (Step 1 in 2014, Step 2 in 2017, and Step 3 in 2022)

                                       
    Table 32. Estimated Cumulative CO Emissions through Appliance Lifespan 
                                for Subpart AAA
                                       
                                       
    Table 33. Estimated Cumulative CO Emissions through Appliance Lifespan 
                                for Wood Stoves
                                       
                                       
    Table 34. Estimated Cumulative CO Emissions through Appliance Lifespan 
                               for Pellet Stoves

                                       
                                       
    Table 35. Estimated Cumulative CO Emissions through Appliance Lifespan 
                          for Single Burn Rate Stoves
                                       
                                       

    Table 36. Estimated Cumulative CO Emissions through Appliance Lifespan 
                               for Subpart QQQQ

                                       
    Table 37. Estimated Cumulative CO Emissions through Appliance Lifespan 
                            for Forced Air Furnaces

                                       
    Table 38. Estimated Cumulative CO Emissions through Appliance Lifespan 
                             for Hydronic Heaters

                                       
    Table 39. Estimated Cumulative CO Emissions through Appliance Lifespan 
                          for Subparts AAA & QQQQ