## MEMORANDUM

To: Margaret Sheppard , U.S. EPA Cc: Yaidi Cancel, U.S.EPA From: Emily Herzog, Ed Carr, Mark Wagner, ICF International Date: May 21 , 2010 Re: Sensitivity Analysis CMAQ results on projected maximum TFA rainwater concentrations and maxim um 8 -hr ozone concentrations (Deliverable under EPA Contract Number EP -W-06 -008 Task Order 038 , Task 06) In addition to updating the baseline analysis for the Assessment of the Potential Impacts of HFO
- 1234yf and the Associated Production of TFA on Aquatic Communities and Local Air Quality, ICF conducted a sensitivity analysis based on the findings of Papasavva et al. as described in their 2009 paper Estimated 2010 Refrigerant Emissions of 2,3,3,3
- tetrafluoropropene (HFC
- 1234yf) in the United Stated Resulting from Automobile Air Conditioning. This memorandum summarizes the results from the sensitivity analysis and provides a comparison of the results with the baseline analysis as well as with the findings of Luecken et al. (2010). Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.

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# Assessment of Potent

ial HFO - 1234yf Emissions The following section describes the assumptions used to determine potential emissions of HFO - 1234yf. 

### Scenarios of HFO - 1234yf Market Penetration For the Assessment of the Potential Impacts of HFO-1234yf and the Associated Production of TFA on Aquatic Communities, Soil and Plants, and Local Air Quality, two scenarios were developed. Both scenarios assume that HFO - 1234yf is used as a drop - in replacement for H FC- 134a, 1 

### with a replacement ratio of 1:1 HFC- 134a to HFO - 1234yf. 2



###  Scenario 1: HFO - 1234yf is used in the United States as a new car refrigerant in the MVAC sector. HFO - 1234yf begins penetrating the market in 2016 reaching 100 percent market penetrati on by 2020, as described in Table 1 below.
 Scenario 2: HFO - 1234yf is used in the United States as a new car refrigerant in MVAC systems, refrigeration, and stationary AC systems. Similar to scenario 1, by 2020, HFO - 1234yf is used in all new MVAC systems. For refrigeration and stationary AC systems, HFO - 1234yf enters the market in 2010, reaches 30 percent penetration of the market in 2015, and 100 percent by 2020. The market penetration scenarios are summarized in Table 1 below. Table 1 : Summary of Assumed Penetration of HFO1234yf in Scenarios Used in Analysis*

Sectors 2010 2015 2020 Scenario 1 MVACs 0% 0 % 100% Scenario 2 MVACs 0% 0 % 100% Refrigeration 6% 30% 100% Stationary Air Conditioning 6% 30% 100% *The dates of introduction of HFO - 1234yf are consistent with the earlier analysis, conducted in 2009. 

### The specific dates of introduction are used as a demonstration of how HFO - 1234yf might be phased in; actual dates may differ by several years. Examining the period from initial introduction of the refrigerant to market saturation allows the analysis to consider potential impacts of HFO - 1234yf in the near-term (i.e., 10 - 15 years), during which t ime there are already specific State goals for ground - level ozone impacts. In addition, the analysis considers the potential longer term impacts of HFO - 1234yf after the refrigerant has saturated the market, assuming continued growth in use. 

### HFO- 1234yf Emission Assumptions For the se nsitivity analysis, emission assumptions were based on the findings of Papasavva et al. (2009) regarding the emission projections of HFO - 1234yf from the MVAC sector. In contrast, ICF assumed that

1 In all scenarios, HFO - 1234yf replaces only pure HFC- 134a, not any blends with HFC- 134a as a component. 2 The ratio of HFC - 134a to HFO - 1234yf has been estimated at 1:0.9, however a 1:1 ratio was used to provide a worst case estimate .

### 2

emissions of HFO - 1234yf will be equivalent to emissions of HFC- 134a for the baseline analysis . Emission assumptions for both the baseline analysis and the sensitivity analysis are summarized below in Table 2 . Table 2 : Refrigerant Loss Assumptions for Baseline and Sensitivity Analysis

Assumption Baseline Analysis a Sensitivity Analysis Leak Rate 8% 5.6% Servicing Leaks (annualized) 10% 3.2% End -of - life Loss Rate 42.5% 42.5% a HFC- 134a MVAC assumptions from the U.S. EPA Vintaging Model, Version V M IO File v4.4_12 - 16 -09 . 

### For both analyses, emissions of refrigerant due to servicing motor vehicle air conditioning systems were expected to be higher during the spring and summer, with up to 80% of emissions due to repairs occurring from April through August. 3 

### Furthermore, refrigerant emissions from servicing motor vehicle air conditioning systems were estimated at 47% of annual refrigerant emissions from motor vehicles. 4 

### As a result, the analysis assumes that 59.5% of annual emissions of HFO - 1234yf would occur from April through August, with 11.9% of annual emissions occurring during each of those five months. The remaining 40.5% of annual emissions was modeled to occur from September through March, with 5.8% of annual emissions occurring during eac h of those seven months. This assumption was also applied to stationary AC end uses based on the assumption that similar patterns of seasonal emissions would be attributable to this end - use. 

### Estimated Emissions of HFO - 1234yf Using EPA’s Vintaging Model, I CF estimated emissions of HFO - 1234yf for both scenarios using both sets of emission assumptions. These estimates are summarized in Table 3 while estimated monthly emission estimates of HFO - 1234yf for the year 2050 are provided in Table 4 . Complete table s with estimated annual emissions can be found in Annex A and Annex B . Table 3 : Summary of Estimated Emissions of HFO- 1234yf (MT)* Scenarios 2020 20 3 0 2040 20 50 Baseline Analysi s Scenario 1 (MVAC) 6,244 28,327 33,093 35,851 Scenario 2 (All Ref and AC) 10,501 43,296 55,070 60,616 Sensitivity Analysis Scenario 1 (MVAC) 3,053 15,349 18,841 20,411 Scenario 2 (All Ref and AC) 7,309 30,318 40,817 45,175 * ICF projected emission s of HFO - 1234yf using special scenarios designed specifically for this analysis and run on the U.S. EPA Vintaging Model, Version VM IO File v4.4_12 - 16 -09 . Table 4 : Summary of Estimated Monthly Emissions of HFO- 1234yf in 2050 (MT) Scenarios Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Baseline Analysis Scenario 1 (MVAC) 2,074 2,074 2,074 4,266 4,266 4,266 4,266 4,266 2,074 2,074 2,074 2,074 Scenario 2 (All Ref and AC) 4,025 4,025 4,025 6,489 6,489 6,489 6,489 6,489 4,025 4, 025 4,025 4,025 Sensitivity Analysis Scenario 1 (MVAC) 1,181 1,181 1,181 2,429 2,429 2,429 2,429 2,429 1,181 1,181 1,181 1,181 Scenario 2 (All Ref and AC) 3,131 3,131 3,131 4,651 4,651 4,651 4,651 4,651 3,131 3,131 3,131 3,131

3 Hoffpauir, Elvis. 2009. Email to Karen Thundiyil, 10 March. 4 U.S. EPA Vintaging Model, Ve rsion VM IO File v4.2 10 -07 -08

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Figure 1 , Figure 2 , and Figure 3 graphically depict the estimated annual HFO - 1234yf emissions for each scenario. Figure 4 graphically depicts the estimated 2050 monthly HFO - 1234yf emissions for each scenario. Figure 1 : Estimated Emission s of HFO- 1234yf by End - Use Sector under the Baseline Analysis (MT)

Figure 2 : Estimated Emissions of HFO- 1234yf by End - Use Sector under the Sensitivity Analysis (MT)

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Figure 3 : Estimated Annual Emissions of HFO- 1234yf under All Scenarios (MT)

Figure 4 : Estimated Monthly Emissions of HFO- 1234yf under All Scenarios in Year 2050 (MT)

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# Re sults of the Sensit

ivit y Analysis Using EPA’s CMAQ model version 4.7, a one -year simulation was performed using 2001 meteorological data to project maximum monthly TFA rainwater concentrations, monthly maximum dry deposition of TFA, and maximum 8 - hr ozone concentrations for the Los Angeles and Houston regions resulting from emissions of HFO - 1234yf from those regions only. These regions were chosen based on the potential presence of vernal pools, their susceptibility to high TFA deposition concentrations, and their continuing and chronic problem with high levels of ground level ozone. The model used the extended version of the carbon bond five chemical mechanism as de veloped by Luecken et al. ( 2010 ), which incorporates the gaseous and aqueous chemistry of HFO - 1234yf and its products. In ICF’s Assessment of the Potential Impacts of HFO- 1234yf and the Associated Production of TFA on Aquatic Communities, Soil and Plants, and Local Air Quality (2010) results from the baseline analysis are presented. The results for the sensitivity analysis are summarized below . 

### TFA Rainwater Concentrations Monthly maximum average TFA rainwater concentrations for each region under each scenario are summarized in Table 5 . Table 5 : Summary of Estimated Monthly Average TFA Rainwater Concentrations in 2050 ( ng/L) Region Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Sensitivity Analysis , Scenario 1 Los Angeles 59 21 109 108 497 572 363 484 107 78 128 61 Houston 12 14 21 17 26 38 54 30 28 12 10 17 Sensitivity Analysis , Scenario 2 Los Angeles 130 47 240 240 1099 1267 803 1 072 237 173 283 136 Houston 26 30 46 38 57 85 120 67 63 27 23 38 

### Under scenario 1 for the sensitivity analysis, t he results indicate that the maximum monthly average TFA rainwater concentration in the Los Angeles region in 2050 is 572 ng/L, while the ma ximum monthly average TFA rainwater concentration in the Houston region in 2050 is 54 ng/L. Under scenario 2 for the sensitivity analysis, t he results indicate that the maximum monthly average TFA rainwater concentration in the Los Angeles region in 2050 is 1,267 ng/L, while the maximum monthly average TFA rainwater concentration in the Houston region in 2050 is 120 ng/L. Similar to the baseline analysis, for Los Angeles, June represents the month with the highest projected monthly average TFA rainwater concentration, while for Houston, July represents the month with the highest projected monthly average TFA rainwater concentration. The monthly average maximum TFA rainwater concentrations for these two peak months are geographically depicted below in

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Figure 5 

### and Figure 6, for both scenarios, for Los Angeles and Houston, respectively.

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Figure 5 : June 2050 Los Angeles Sensitivity Analysis Scenario 1 and Scenario 2 Results

Figure 6 : July 2050 Houston Sensitivity Analysis Scenario 1 and Scenario 2 Results



### TFA Dry Deposition Table 6 presents the results of both the maximum annual and monthly maximum TFA deposition expressed on an annual basis . Table 6 : Summary of Estimated TFA Dry Deposition in 2050

Notes: Formula weight of TFA i s 114 g/mole. a Maximum concentration occurred in May for Los Angeles and in July for Houston. Results are expressed on annual basis using the peak monthly deposition rate times 12.

TFA Maximum Monthly Average a TFA Maximum Annual Average nmole/m 2-yr g/m2 -yr nmole/m 2-yr g/m2 -yr Sensitivity Analysis, Scenario 1 Los Angeles 8,698 323 2,188 81 Houston 1,455 54 534 20 Sensitivity Analysis, Scenario 2 Los Angeles 16,686 619 4,745 176 Houston 2,813 104 1,148 43

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### Ground Level Ozone Concentrations Under scenario 1 for the sensitivity analysis, results for the Los Angeles and Houston region s show a maximum increase in the 8- hr ozone concentration of 0.030 ppb and 0.009 ppb, respectively . Under scenario 2 for the sensitivity analysis, results for the Los Angeles and Houston region s show a maximum increase in the 8 - hr ozone concentration of 0.0 57 ppb and 0.0 16 p pb, respectively . Assuming an 8 - hr ozone standard of 75 ppb, HFO - 1234yf is projected to contribute to a maximum of roughly 0.04 – 0. 076 % of total ground - level ozone in Los Angele s and 0.012 – 0.021% and of total ground - level ozone in Houston. Maximum increases in 8 - hr ozone concentrations are geographically depicted in Figure 7

### , Figure 8

### , and Figure 9 . Figure 7 : LA May 22, 2050 Sensitivity Analysis Scenario 1 and Scenario 2 Results

Figure 8 : Houston June 11, 2050 Sensitivity Analysis Scenario 1 and Scenario 2 Results

Figure 9 : Houston August 29, 2050 Sensitivity Analysis Scenario 1 Results

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# Comparison of Results For comparison purposes, the following table summarizes results of the baseline analysis, the sensitivity analysis, and Luecken et al. (20 10 ). Table 7 : Comparison of Results for Southern California Analysis Maximum Projected TFA

Rainwater Concentration (ng/L) Maximum Estimated TFA Dry Deposition ( g/m 2)* Maximum Increase in 8- hr Ozone Formation Baseline, Scenario 1 1,11 6 143 0.07% Baseline, Scenario 2 1,700 237 0.1 1 % Sensitivity, Scenario 1 572 81 0.04% Sensitivity, Scenario 2 1,267 176 0.0 8 % Luecken et al. (20 10 ) 1,264 240 0.1% *ICF res ults represent the annual average maximum for Southern California, while Luecken’s results represent the 2.5 month spatial average. For Southern California, Luecken’s results show TFA dry deposition to be about 150 g/m 2 

### . The relationship between HFO- 1234yf emissions and projected maximum TFA rainwater concentrations for both regions are also displayed below in Figure 10 and



### Figure 11 . Figure 10 : Relationship between HFO- 1234yf emissions and maximum TFA rainwater concentrations in LA

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Figure 11 : Relationship between HFO- 1234yf emissions and maximum TFA rainwater concentrations in Houston



### As shown above , the relationship between HFO - 1234yf emis sions and TFA rainwater concentrations appears to be relatively linear . To support this relationship, the data for each region were fitted to a linear regression model . The equations for each regression model are as follows: Los Angeles TFA Rainwater Co ncentration = 51.55 + (HFO - 1234yf Emissions * 0.027 ) Houston TFA Rainwater Concentration = 4.64 + (HFO - 1234yf Emissions * 0.0026 ) The equations above can be used to estimate TFA rainwater concentration projections for other HFO 1234yf emission scenarios . However, it must be noted that th e equations assum e that the current chemical mechanism of gas- phase and aqueous chemistry of HFO - 1234yf and its products remains substantially the same in future analyses. Also, it is possible that results may differ if other meteorological datasets (e.g., 2005) or higher spatial resolutions (e.g., 12 - km) were used in the original analysis. Finally, due to localized variability in meteorology and emission distributions, these results cannot be applied to other regions of the U.S.

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## Annex A: Annual HFO - 1234yf Emissions Estimated under Each Scenario for the Baseline Analysis for Years 2010 through 2050 (MT)* Year Baseline Scenario 1 Baseline Scenario 2

MVACs MVACs Refrigeration Stationary AC TOTAL 2010 - - 39 7 46 2011 - - 111 20 132 2012 - - 218 40 258 2013 - - 361 66 426 2014 - - 541 98 640 2015 - - 762 138 900 2016 407 407 1,093 196 1,696 2017 1,229 1,229 1,541 273 3,043 2018 2,472 2,472 2,110 369 4,951 2019 4,143 4,143 2,807 485 7,435 2020 6,244 6,244 3,636 620 10,501 2021 8,332 8,332 4,487 766 13,585 2022 10,413 10,413 5,389 916 16,718 2023 12,513 12,513 6,278 1,066 19,857 2024 14,644 14,644 7,209 1,216 23,069 2025 16,812 16,812 8,128 1,367 26,307 2026 19,003 19,003 9,043 1,516 29,561 2027 21,203 21,20 3 9,953 1,678 32,834 2028 23,962 23,962 10,914 1,848 36,724 2029 26,335 26,335 11,817 2,017 40,170 2030 28,327 28,327 12,748 2,221 43,296 2031 29,926 29,926 13,591 2,412 45,929 2032 31,118 31,118 14,348 2,577 48,043 2033 31,295 31,295 14,918 2,720 48 ,932 2034 31,514 31,514 15,479 2,861 49,854 2035 31,791 31,791 15,924 3,010 50,725 2036 32,084 32,084 16,382 3,213 51,678 2037 32,374 32,374 16,824 3,408 52,606 2038 32,627 32,627 17,249 3,592 53,468 2039 32,857 32,857 17,656 3,767 54,280 2040 33,09 3 33,093 18,046 3,931 55,070 2041 33,345 33,345 18,371 4,008 55,724 2042 33,637 33,637 18,668 4,080 56,385 2043 33,906 33,906 18,921 4,151 56,977 2044 34,177 34,177 19,156 4,217 57,549 2045 34,450 34,450 19,374 4,278 58,102 2046 34,726 34,726 19,566 4,315 58,606 2047 35,004 35,004 19,756 4,351 59,110 2048 35,284 35,284 19,944 4,383 59,611 2049 35,566 35,566 20,132 4,415 60,112 2050 35,851 35,851 20,318 4,447 60,616 * 

### ICF projected emissions of HFO - 1234yf using special scenarios designed specifica lly for this analysis and run on the U.S. EPA Vintaging Model, Version VM IO file v4.4_12 - 16 -09 .

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## Annex B : Annual HFO - 1234yf Emissions Estimated under Each Scenario for the Sensitivity Analysis for Years 2010 through 2050 (MT)* Year Sensitivity Scenario 1 Sensitivity Scenario 2

MVACs MVACs Refrigeration Stationary AC TOTAL 2010 - - 39 7 46 2011 - - 111 20 132 2012 - - 218 40 258 2013 - - 361 66 426 2014 - - 541 98 640 2015 - - 762 138 900 2016 199 199 1,093 196 1,488 2017 601 601 1,541 273 2,415 2018 1,209 1,209 2,110 369 3,688 2019 2,026 2,026 2,807 485 5,317 2020 3,053 3,053 3,636 620 7,309 2021 4,073 4,073 4,487 766 9,326 2022 5,091 5,091 5,389 916 11,396 2023 6,118 6,118 6,278 1,066 13,461 2024 7,159 7,159 7,209 1,216 15,584 2025 8,219 8,219 8,128 1,367 17,714 2026 9,290 9,290 9,043 1,516 19,849 2027 10,366 10,366 9,953 1,678 21,997 2028 12,206 12,206 10,914 1,848 24,968 2029 13,868 13,868 11,817 2,017 27,702 2030 15,349 15,349 12,748 2,221 30,318 2031 16,647 16,647 13,591 2,412 32,650 2032 17,749 17,749 14,348 2,577 34,674 2033 17,819 17,819 14,918 2,720 35,456 2034 17,918 17,918 15,479 2,861 36,259 2035 18,077 18,077 15,924 3,010 37,011 2036 18,257 18,257 16,382 3,213 37,851 2037 18,444 18,444 16,824 3,408 38,675 2038 18,5 95 18,595 17,249 3,592 39,436 2039 18,718 18,718 17,656 3,767 40,141 2040 18,841 18,841 18,046 3,931 40,817 2041 18,973 18,973 18,371 4,008 41,352 2042 19,150 19,150 18,668 4,080 41,898 2043 19,303 19,303 18,921 4,151 42,375 2044 19,458 19,458 19,156 4,217 42,830 2045 19,613 19,613 19,374 4,278 43,265 2046 19,770 19,770 19,566 4,315 43,651 2047 19,928 19,928 19,756 4,351 44,035 2048 20,088 20,088 19,944 4,383 44,415 2049 20,249 20,249 20,132 4,415 44,795 2050 20,411 20,411 20,318 4,447 45,175 * ICF projected emissions of HFO - 1234yf using special scenarios designed specifically for this analysis and run on the U.S. EPA Vintaging Model, Version VM IO file v4.4_12 - 16 -09 .