## MEMORANDUM

**To:** Margaret Sheppard, U.S. EPA **CC:** Rachel Schwartz, Sally Hamlin, Rebecca von dem Hagen, Bella Maranion, Cindy Newberg, U.S.

EPA **From:** Kasey Knoell, Becky Ferenchiak, Jenny Tanphanich, Ed Carr, Mark Wagner, ICF International **Date:** February 24, 201 4 **Re:** Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentration s (EPA Contract Number EP -W- 10 -031 Task Order 3 05 , Task 01) In response to technical direction received from EPA, ICF has prepared an assessment of the potential impact on ground level ozone concentrations caused by release of hydrocarbon refrigerants across refrigeration and air conditioning end uses. Refrigerant emissions were modeled from the U.S. EPA’s Vintaging Model ( VM_IO file_V4.4_11.6.12 ) and their impacts on ground level ozone were modeled using the CMAQ model (version 4.7 .1 ) . Releases of isobutane and propylene were modeled in Los Angeles, Houston, and At lanta under t hree emissions scenarios: 1) all refrigeration and air conditioning (ref/AC) end
- uses, 2) ref/AC excluding motor vehicle air
- conditio ners (MVACs) , and 3) ref/AC excluding MVACs and chillers . A final scenario was modeled , in which limitations o n the properties of hydrocarbons (e.g., flammability) are considered to determine which end - uses were likely to transition to hydrocarbon refrigerants. The remainder of this memorandum summarizes the results of this assessment . A quantitative analysis of t he uncertainty levels can also be performed by undertaking add itional CMAQ simulations if requested by the EPA TOCOR. Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.2 

# Po te ntial	Impacts	of	Hydrocarbon	Refrigerants on Ground - Leve l	Ozone Concentrations **1 Executive	Summary**  Hydrocarbons are increasingly being considered for use in a number of refrigeration and air- conditioning (ref/AC) end - uses. Although hydrocarbons have a low global warming potential (GWP) and are thus desirable alternative s to commonly used hydrofluorocarbons (HFCs), there is concern that use of hydrocarbons could negatively impact local air quality due to their high maximum incremental reactivity (MIR) values . In order to evaluate their potential impact, thre e conservative hydrocarbon emission scenarios and one more realistic scenario were analyzed . The first three evaluate emissions of propylene and isobutane first from the entire refrigeration and air conditioning sector, second excluding motor vehicle air c onditioning, and third excluding motor vehicle air conditioning and chillers. A fourth scenario, evaluating emissions of a mix of propylene, isobutane, and propane, was developed based on SNAP hydrocarbon applications and UL Standards and represents a more realistic transition to hydrocarbons . The hydrocarbon emissions from these scenarios were estimated based on U.S. EPA’s Vintaging Model, and their potential contributions to ozone concentrations were assessed using U.S. EPA’s Community Multi scale Air Qua lity (CMAQ) model . C MAQ modeling was performed for April through the end of September, as these months presented the largest releases of hydrocarbon refrigerant as well a s weather conditions favorable for ozone formation . The ozone concentrations were estimated for the Atlanta, Houston and Los Angeles regions, due to their distinctive geographic setting and c hronic high levels of ground level ozone, and then scaled for n ational emission estimates . The results of the CMAQ modeling indicated that h ydrocar bon refrigerants under the most conservative scenario could potentially increase ground level ozone by up to 9% compared to the national ozone standard, but less than a 0.2% increase under the most realistic scenario. The analysis performed is based on several assumptions and projections that cannot be known with certainty at this time. These limitations are associated with both the unknown market penetration of alternatives and climate conditions, among other factors. 

## 2 **Introduction** Ozone - depleting subst ances (ODS) such as CFC- 12 , R-502 , and HCFC- 22 were h istorically used across the refrigeration and air- conditioning sector . Since identif ying the damaging nature of CFCs and HCFCs, EPA moved swiftly to transition to alternatives . The phaseout of CFCs in 1996 and continued phasedown of HCFCs, has led the U.S. EPA Significant New Alternatives Policy (SNAP) program to review and approve a number of potential substitutes to these ODS . In particular, hydrocarbon refrigerants, which ha ve zero ODP and low GWP, have already been recently approved for smaller refrigeration applications (e.g., domestic refrigeration, small retail food refrigeration , and vending machines ) and have the potential to be used more broadly across the refrigeratio n and air-conditioning sector . Compared to the HFCs and HCFCs currently in use , which have high GWPs, h ydrocarbons have the potential to significantly reduce climate impacts from the refrigeration and air conditioni ng sector. Although the use of hydrocarbo ns could potentially mitigate greenhouse gas (GHG) emissions, it could also potentially contribute to increased levels of ground level ozone. Hydrocarbons have high MIR3

values, and may influence local air quality if emitted in sufficient ly high quantities . Table 1 provides a summary of the propensity of these refrigerants to form tropospheric ozone. 1

**Table 1**  **: Propensity of Refrigerants to**  **F orm**  **Tropospheric Ozone Compound**  **North America Maximum Incremental Reactivity (MIR) Scale**  **(g -** **O 3** **/g -** **substance) Europe POCP Scale**  a **(Relative Units)** HCFC- 22 <0.1 0.1 HFC- 134a <0.1 0.1 Propylene 11.57 112 Ethane a 0.28 12 Isobutane 1.34 31 Propane 0.56 18 Ethylene 9.07 100 Source: IPCC 2005 aThe POCP value is the ozone creating potential of a compound relative to ethylene (eth e ne), expressed as an index where ethylene = 100. b EPA uses the reactivity of ethane as the threshold for determining whether a compound has negligible reactivity. Compounds that are less reactive than, or equally reactive to, ethane under certain assumed conditions may be deemed negligibly reactive and th erefore suitable for exemption from the definition of a VOC (EPA 2012) . It should be noted that EPA is currently considering exempting certain hydrocarbons in certain end - uses from the ban on venting of refrigerant under §608 of the Clean Air Act . In orde r to evaluate the potential impact of the release of hydrocarbons during disposal , ICF modeled conservative and realistic hydrocarbon emission scenarios from the refrigeration/AC sector and assessed their impacts on ground level ozone, taking into consideration this revision to the end - of- life management requirement . Th e remainder of this report summarizes the methodology used and results in the following order:

 Section 3: Hydrocarbon Emission Scenarios  Section 4: Impact on Ground - Level Ozone Concentrations  Section 5 : Analysis Limitations  Section 6: S ummary of F indings  Section 7: References

1 R eactivity scales rank the propensity of organic compounds to form ozone . The MIR scale assesses the ir contributions to the photochemical ozone formation in urban plumes and is reflective of its use in North America, where ground - level ozone formation is considered an urban issue . I n contrast, the POCP scale addresses long range trans- boundary formation a nd transport of ozone and was developed for use in Europe, where ground - level ozone formation occurs on the regiona l scale in multi - day episodes ( IPCC 2005) . As the MIR scale is more applicable to conditions within the United States, the remainder of this report references the MIR scale.4



## 3 **Hydrocarbon	Emission Scenario**  **s** Under this analysis, isobutane and propylene were each modeled under t hree conservative emissions scenarios for the refrigeration and air conditioning sector. A fourth, more realistic emissions scenario was also modeled, which considered more likely transitions to a variety of hydrocarbon refrigerants (i.e., isobutane, propylene, and propane ) by end - use in the sector . The four emission scenarios considered are as follows: 1) **Scenario 1:** the **entire ref/AC sector** : chillers, motor vehicle air conditioners (M VACs) (i.e., lightduty trucks and vehicles, trains, transit buses, school buses, and tour buses), residential and light commercial AC and heat pumps, 2 retail food, 3 cold storage warehouses, industrial process refrigeration , refrigerated transport, and household refrigeration and freezers ; 2) **Scenario 2:** the ref/AC sector **excluding MVACs**; 3) **Scenario 3:** the ref/AC sector **excluding MVACs and chillers ;**  **4** and 4) **Scenario 4:** the ref/AC sector for end - use application s in which a SNAP submission has been received for a hydrocarbon or in which a UL Standard addressing flammable refrigerant is in place. See Appendix B for more information on the end uses included in this scenario. In order to estimate their potential impact on ground - level ozone concentration, the national scale hydrocarbon emissions from each scenario were estimated using EPA’s Vintagin g Model (VM) . 5 These national emissions were then proportional ly scaled to each urban area by population by county. For Los Angeles, three counties were used representing about 4.4% of the U.S. population ; for Houston , eight counties representing about 2.0% of the U.S. population were used; and for Atlanta , ten counties representing about 1. 4% of the U.S. population were used . The se county level emissions were then spatially allocated to each emission grid cell based on population density. The remainder of this section provides a summary of the methodology used to estimate the national inventory of hydrocarbon emissions, as well as a description of each scenario considered. 

### 3.1 **Methodology	for	Emissions	Estimates** The year 2030 was chosen as the analysis year for all scenarios, in order to conservatively estimate the impact of hydrocarbons . T he majority of non - hydrocarbon equipment will have been retired by the year, due to the lifetimes of equipment (i.e., 5 to 27 years). In addition, a 2030 nationwide emission inventory was available for other emission sources and was used to estimate the baseline ozone concentration (without hydrocarbon refrigerants). I t was assumed that the hydrocarbon refrigerants would enter the market in 2012, and reach 100% market penetration in 2030 . Output from the VM is provided on an annual basis; for the purposes of this analysis, the annual data was weighted on a monthly basis, and

2 The residential and light commercial AC and heat pumps end - use includes the following applications: window AC units, residential unitary AC, small commercial unitary AC, large commercial unitary AC, packaged terminal AC and heat pumps (PTAC/PTHP), and wat er and ground source heat pumps. 3 The retail food end - use includes the following applications: ice makers, small retail food systems, medium retail food systems, and large retail food systems. 4 Chillers are large - scale air conditioning systems for larg e commercial and institutional buildings, such as for office buildings, hotels, hospitals, and the like. 5 EPA’s Vintaging Model estimates the annual chemical emissions from industry sectors that have historically used ODS, including AC, refrigeration, foa ms, solvents, aerosols, and fire protection. Within these industry sectors, there are over 60 independently modeled end - uses. The model uses information on the market size and growth for each end - use, as well as a history and projections of the market tran sition from ODS to alternatives. The model version used in this analysis is VM_IO file_V4.4_11.6.12.5

assumed that 11.9% of annual emissions occurred during each month from April to August . E missions of refrigerant are reasonably anticipated to occur primarily during the warmer s pring and s ummer months, when air conditioning equipment is increasingly used. Emissions d ue to servicing MVACs are also expected to be higher during the spring and summer, with u p to 80% of emissions due to repairs occurring April through August ( MACS 2009 ). Furthermore, refrigerant emissions from servicing motor vehicle air conditioning systems were estimated at 47% of annual refrigerant emissions from motor vehicles ( EPA 2008) . This assumption was also applied for all scenarios to all stationary AC end - uses based on the assumption that seasonal emissions would follow similar patterns. Emissions of refrigerant from refrigeration equipment were assumed to occur equally year- round. S maller end - uses (i.e., end - uses with a charge size less than 200 kg) were assumed to have a 100% relea se of refrigerant upon disposal . D isposal release rates for larger end - uses (i.e., chillers, industrial process refrigeration systems, and large retail food systems) and serv ic ing release rates for all end - uses were assumed to remain consistent with current VM assumptions, due to the assumed regulations and financial incentives for the end - user. E ach state implements individual emission and VOC regulatio ns that inhibit venting. For example, Regulation 7:27 - 16.1a for New Jersey (which is a nonattainment area) requires the use of reasonably available control technology for equipment. Venting would violate this regulation. Maryland implements a regulation th at states that a person may not cause or permit the discharge of VOC from any installation constructed on or after November 15, 1992 in excess of 20 pounds (9.07 kilograms) per day unless the discharge is reduced by 85 percent or more overall. In addition to state regulations, industry standards also restrict venting. Under OSHA regulations, facilities are required to demonstrate that 25 percent of the lower flammability limit ( LFL ) would not be exceeded at any point during venting of hydrocarbon refrigeran ts . Chillers and other large charge size commercial refrigeration systems do not currently implement the proper engineering controls that would be needed to allow for safe venting. The use of flares, stacks, or rapid emission controls may likely be require d to meet these industry standards . Equipment would have to be modified to incorporate these controls, or venting would not be allowed. Furthermore, a ssuming 100% is vented during servicing of equipment is unrealistic from an economic perspective. Even wi th a low cost refrigerant, such as propane or isobutane, venting a c harge size of over 1,000 grams still represents a significant cost and provides an incentive to collect refrigerant, which also is in keeping with good maintenance and technician practices . The reader is referred to Appendix A for a summary of detailed assumptions used in this analysis . 

### 3.2 **Conservative Emissions	Scenario**  **s** Hydrocarbons are currently being proposed for use in a wide range of ref/AC end
- uses. To estimate th e most conservative impact that releases of hydrocarbons could have on ground - level ozone, the first scenario considered under this analysis assumes release from the entire ref/AC sector. However, due to the characteristics associated with hydrocarbon s (e. g., flammability), this may not be realistic. To assess more realistic, but still conservative scenarios, two additional scenarios were considered. All three scenarios assume that the end - uses would be replaced with either propylene or isobutane . Propylen e exhibits the highest MIR of hydrocarbons, and therefore represent s the mo st conservative estimates . Propylene is also a proxy for the hydrocarbon blend R -443A, a substitute refrigerant under evaluation for use in residential air conditioning, because that blend contains more than 50% propylene. Isobutane has the highest MIR of the saturated hydrocarbons under evaluation and was used as a conservative proxy for iso butane, propane, and the hydrocarbon blend R -441A. R-441A contains more than 50% propane, as well as isobutane and other saturated hydrocarbons .6

Table 2 presents the monthly emissions in 2030 which were assumed under Scenarios 1, 2, and 3. Under each scenario, 100% of the emissions were assumed to occur from either isobutane or propylene. In other words, the impact on local ozone concentrations were evaluated for six total CMAQ modeling scenarios. **Table 2**  **: 2030**  **National Refrigerant**  **Emissions under**  **Scenarios 1 , 2, and**  **3 Month**  **Scenario 1**  **Emissions (MT)**

**(All Ref /** **AC) Scenario**  **2 Emissions (MT)** 

**(No M V** **AC) Scenario**  **3 Emissions (MT)**  **(No M V** **AC or Chillers) Isobutane or Propylene**  **Isobutane or Propylene Isobutane or**  **Propylene** January 8,06 5 5,894 5,793 February 8,06 5 5,894 5,793 March 8,06 5 5,894 5,793 April 13,404 9,35 6 9,140 May 13,404 9,356 9,140 June 13,404 9,356 9,140 July 13,404 9,356 9,140 August 13,404 9,356 9,140 September 8,06 5 5,894 5,793 October 8,065 5,894 5,793 November 8,065 5,894 5,793 December 8,065 5,894 5,793 Note: Emissions of isobutane and propylene are equivalent; s haded months indicate those used in the analysis .7

**Figure 1**  presents the percent contribution of isobutane and propylene emissions by end - use under Scenarios 1 through 3. As illustrated in these charts, residential AC end - uses presented the most signi ficant source of emissions across all three scenarios.

**Figure 1**  **. Percent Contribution of End**  **- Use to Total**  **Emissions under Scenarios 1**  **- 3** 

Note: Emissions under the residential and light commercial AC and heat pumps end - use (Res and Comm AC) consists of 43 % from residential unitary AC, 4% from window AC, 2 % from small commercial unitary AC, 0. 2 % from large commercial unitary AC, 0 .2 % from PTACs, and 0. 1 % from water and ground source HPs (relative to total emissions in Scenario 1) . Emissions under the MVAC end - use consists of 15% from light- duty vehicles, 14% from light- duty trucks, 0.3% from school and tour buses, 0.1% from transit buses, and 0.1% from trains (relative to total emissions in Scenario 1). Note: Emissions under the residential and light commercial AC and heat pumps end - use (Res and Comm AC) consists of 61 % from residential unitary AC, 6 % from window AC, 3 % from small commercial un itary AC, 0. 3 % from large commercial unitary AC, 0 .3 % from PTACs, and 0. 2 % from water and ground source HPs (relative to total emissions in Scenario 2) . Retail Ref 4%
Household Ref 1% IPR 4% Transport Ref 9% Dehumidif ers 0% MVAC 30% Chillers 2% Res and

Comm AC 50% Cold

Storage 0% **Scenario 1** Retail Ref 5% Household Ref 1% IPR 6% Transport Ref 13% Dehumidif ers 0% Chillers 2% Res and Comm AC 72% Cold

Storage 1% **Scenario 2**8 Note: Emissions under the residential and light commercial AC and heat pumps end - use (Res and Comm AC) consists of 63 % from residential unitary AC, 6% from window AC, 3 % from small commercial unitary AC, 0. 4% from large commercial unitary AC, 0 .3 % from PTACs, and 0. 2 % from water and ground source HPs (relative to total emissions in Scenario 3) . 

### 3.3 **Realistic	Emissions	Scenario** In addition to the three end - use scenarios, a fourth more realistic scenario (i.e., Scenario 4 ) was developed in which hydrocarbons were only modeled in refrigeration and air conditioning equipment for which a SNAP submission was received or for which there is a UL Standard in place regulating flammable refrigerants. Furthermore, the type of hydrocar bon (i.e., isobutane, propylene, or propane) or blend likely to be used in each end - use was also considered . The reader is referred to Appendix B for additional information regarding the assumptions us ed under this scenario. Estimate d e missions for the most realistic scenario are shown in Table 3 .

**Table 3**  **: 2030**  **National Refrigerant**  **Emissions of under**  **Scenario 4 Month**  **Scenario 4 Emissions (MT)**  **(“ Most**  **Realistic Scenario”) Propane**  **Isobutane Propylene**  January 1,266 78 183 February 1,266 78 183 March 1,266 78 183 April 1,37 3 84 207 May 1,373 84 207 June 1,373 84 207 July 1,373 84 207 August 1,373 84 207 September 1,266 78 183 October 1,266 78 183 November 1,266 78 183 December 1,266 78 183 Note: Shaded months indicate those used in the analysis Retail Ref 5% Household Ref 1% IPR 7% Transport Ref 13% Dehumidif

ers 0% Res and Comm AC 73% Cold Storage 1% **Scenario 3**9

Figure 2 presents the percent contribution s of each refrigerant and each end - use to the total emissions under the S cenario 4 .

**Figure 2**  **. Percent Contribution**  **to Total Emissions under Scenario 4** 

Note: Emissions under the residential and light commercial AC and heat pumps end - use (Res and Comm AC) consists of 67% from window AC and 3 % from PTACs (relative to total emissions in the Scenario 4 ). 

## 4 **Impact on**  **Ground	Level	Ozone	Concentration s**  Using EPA’s CMAQ photochemical model version 4.7.1 , a simulation of the potential ground - level ozone impacts under the hydrocarbon emission scenarios summarized in the previous section was performed. The remainder of this section describes the methodology and results of the CMAQ modeling, followed by a compar ison of the results to the national standards of ambient air quality. 

### 4.1 **Methodology** T he projected emissions of isobutane and propylene under Scenarios 1, 2, and 3, and the mix of isobutane, propylene, and propane under Scenario 4 described in Section 3 were input into the CMAQ to predict impacts on the local air quality. Concentrations were only modeled from April through the end of September, as these months presented the largest releases of hydrocarbon refrigerant ( see Table 2 and Table 3 ) , as well as warmer a ir temperature and longer period of sunlight which increase the potential for ozone creation. The maximum increase in 8 - hr ozone concentrations were estimated for the Atlanta, Houston and Los Angeles regions . These three cities were chosen based on their distinctive geographic setting and continuin g and chronic problem with high levels of ground level ozone . Local refrigerant emissions were scaled from the n ational emission estimates to estimate reasonable conservative impacts. The simulation was performed using 200 5 hourly meteorological data at 36 - km horizontal resolution with 14 vertical layers t o model the maximum increase in 8 - hour ground level ozone concentrations. The model used the carbon bond 05 chemical mechanism which explicitly includes 156 chemical reactions (EPA, 2010). T he 2030 nationwide emission inventory (NHTSA, 2012) , as previously mentioned, was readily available and used to estimate the baseline ozone concentration ( i.e., without hydrocarbon refrigerant) . Retail Food 6% Transport Ref 22%
Househol d Ref 2% Res and Comm AC 70% **By End**  **- Use** 

Propane 83% Isobutan e 5% Propylen e 12% **By Refrigerant** 10

Split factors for use in the carbon bond 05 chemical mechanism for isobut a ne, propylene, and propane were determined from the Emit Worksheet in the emitdb.xls workbook form . 6 The split factors and related parameters used in processing the refrigerant emissions are presented in Table 4 below.

**Table 4. Mass F**  **ractions of CB05 S**  **pecies per gram of E**  **mitted C** **ompound (g/g) Compound**  **P ar** **a ffin** 

**(PAR) Molecular** 

**Weight (g/mole) O**  **lefins**

**(OLE) Molecular** 

**Weight (g/mole)**  **Unreactive**

**(UNR) Molecular** 

**Weight (g/mole)**  Isobutane 1.0 14.5 4 0.0 -- 0.0 -- Propylene 0.34 14.03 0.668 28.06 0.0 -- Propane 0.5 14.7 0 0.0 -- 0.5 14.7 Note: Paraffin compounds are saturated hydrocarbons. Paraffinic compounds consist only of hydrogen and carbon atoms; all bonds are single bonds, and the carbon atoms are not joined in cyclic structures, but instead form an open chain. Olefins are unsaturated che mical compounds containing at least one carbon - carbon double bond.



### 4.2 **CMAQ	Results** Table summarizes the m aximum i ncrease in 8 - hour ground - level ozone from the four scenarios for the Los Angeles, Houston, and Atlanta regions . **Table 5**  **. Maximum Increase in**  **the Daily 8** **- hour**  **G round**  **L evel**  **O zone from**  **Hydrocarbon R** **efrigerant s**  **in 2030 for**  **T hree US cities**  **Refrigerant Type and Use Scenario**  **Cities Los Angeles**  **8 -**  **hr O 3**  **M aximum**  **C hange**  **(ppb) Houston** 

**8 -**  **hr O 3**  **M aximum**  **C hange**  **(ppb) Atlanta** 

**8 -**  **hr O 3**  **M aximum**  **C hange**  **(ppb) Isobutane**  Scenario 1 0.72 0.15 0.05 Scenario 2 0.50 0.10 0.03 Scenario 3 0.49 0.10 0.03 **Propylene** Scenario 1 6.61 0.96 0.56 Scenario 2 4.47 0.67 0.39 Scenario 3 4.37 0.66 0.38 **Combination of Isobutane, P**  **ropylene and P**  **ropane ( Scenario 4** **)** Scenario 4 0.15 0.03 0.01 ppb = parts per billion ; O 3 = ozone In **Los Angeles,** i sobutane under Scenario 1 resulted in a maximum increase in the 8 - hr ozone concentration of 0.72 ppb . Propylene, as anticipated due to its high MIR, resulted in the most significant increases of ground - ozone concentrations ; under Scenario 1 , results for the Los Angeles region show

6 The Emit Worksheet in the emitdb.xls form is available at: http://www.engr.ucr.edu/~carter/emitdb/ .11

that the maxi mum increase in the 8 - hr ozone concentration is 6.61 ppb. Releases of isobutane and propylene under Scenarios 2 and 3 each show similar patterns to Scenario 1 , but with smaller increases . Scenario 4 (i.e., t he “ most realistic” scenario) resulted in a peak 8 - hr ozone increase of just 0.15 ppb for Los Angeles. These relatively small increases in ozone are about 75% associated with the use of propylene as a refrigerant and 21% from propane under this scenario (this is true of Scenario 4 under all locations) . F or all four scenarios, Los Angeles showed the largest ground - ozone concentration increases of all three cities. Figure 3 shows the maximum increases and spatial extent of the 8 - hour ozone concentration increase for isobutane Scenario 1 , propylene Scenario 1, and Scenario 4 for Los Angeles . In these figures, yel low, orange, and red shading represent modeled changes in ozone concentrations.

**Figure 3**  **. Maximum 8 -**  **hour O** **zone I**  **ncrease for Los Angeles in 2030**  **(Clock -** **wise from Left: Scenario**  **1 Isobutane, Scenario 1 Propylene, and Scenario 4)** 12

**In Houston,**  **i sobutane**  **under Scenario 1**  **resulted in a**  **maximum increase in the 8 -**  **hr ozone concentration**  **of 0.15 ppb**  **. For the propylene Scenario 1, results for the**  **Houston region show**  **that the maximum increase in the 8** **- hr ozone concentration**  **is 0.**  **96 ppb**  **. Releases of**  **isobutane and propylene under**  **Scenarios 2 and 3 each**  **show similar patterns to Scenario 1, but with smaller increases.**  **Scenario 4**  **(i. e., t**  **he “**  **most realistic” scenario)**  **resulted in a peak 8 -**  **hr ozone increase of just 0.03 ppb**  **for Houston.**  Figure 4 shows the maximum increases and spatial extent of the 8 - hour ozone concentration increase for the isobutane Scenario 1, the propylene Scenario 1, and Scenario 4 for Houston. In these figures, yellow, orange, and red shading represent modeled changes in ozone concentrations.

**Figure 4**  **. Maximum 8** **- hour**  **O zone Increase**  **for Houston in 2030**  **(Clock -** **wise from Left: Scenario 1 Isobutane, Scenario 1 Propylene, and Scenario 4)**13

**In Atlanta,**  **i sobutane under**  **Scenario 1 resulted in a**  **maximum increase in the 8 -**  **hr ozone concentration**  **of 0.05 ppb**  **. For the propylene Scenario 1, results for the**  **Atlanta region show**  **that the maximum increase in the 8** **- hr ozone concentration**  **is 0.**  **56 ppb**  **. Releases of isobutane and**  **propylene under Scenarios 2 and 3 each show similar patterns to Scenario 1** **, but with smaller increases. Scenario**  **4 (i.e., t**  **he “**  **most realistic” scenario)**  **resulted in a peak 8 -**  **hr ozone increase of just 0.01**  **ppb for**  **Atlanta.** Figure 5 shows the maximum increases and spatial extent of the 8 - hour ozone concentration increase for the isobutane Scenario 1 , the propylene Scenario 1, and Scenario 4 for Los Angeles. In these fig ures, yellow, orange, and red shading represent modeled changes in ozone concentrations.

**Figure 5**  **. Maximum 8** **- hour**  **O zone**  **I ncrease**  **for Atlanta in 2030**  **(Clock -** **wise from Left: Scenario**  **1 Isobutane, Scenario 1 Propylene, and Scenario 4)** 



### 4.3 **Comparison	to	National	Ambient	Air Quality	Ozone	Standard**  The current national ambient air quality 8 - hour average ozone standard (NAAQS) is 75 ppb. The maximum change in ozone concentrations caused by each refrigerant across all scenarios and locations, and comparison to the national standard, is summarized in Table 6 .14

**Table 6**  **. Comparison of Maximum Increase**  **in 8 -**  **hour O** **zone C** **oncentration R** **elative to the NAAQS Refrigerant Type**  **(Scenario) Maximum**  **8 -**  **hr O 3**  **I ncrease**  **(ppb) Percent Increase over**  **75 ppb 8 -**  **hr N**  **ational A** **mbient A** **ir Q** **uality O** **zone S** **tandard** Isobutane (Scenario 1) 0.72 1% Propylene (Scenario 1) 6.61 9% Most Realistic Mix (Scenario 4) 0.15 0.2% ppb = parts per billion ; O 3 = ozone With the exception of Los Angeles, all of the three regions are forecast to be in attainment of the current 8 - hr 75 ppb ozone standard by 2030. Currently, the South Coast is demonstrating attainment by 2023 for the 1997 8 - hr standard of 85 ppb. The deadlin e for demonstrating attainment of the 75 ppb standard is December 2015 and regions must show compliance by 2032. 

## 5 **Limitations	of	this	Analysis** The analysis described above is based on numerous assumptions and projections that cannot be known with certainty at this time. The following discussion recognizes these uncertainties and indicates various factors that have potential to impact and change the results of this analysis. 

### 5.1 **Market	Model l**  **ing**  The market penetration assumptions used for this analysis assume hydrocarbons will be the sole replacement for HFCs across the refrigeration and air-conditioning sector . However, the introduction of addition al substitutes could potentially lower the penetration of hydrocarbons into the market, thus decreasing the emissions and ground level ozone impacts of hydrocarbons .  EPA’s Vintaging Model provides emissions estimates up to 2050 . However, projected estimat es are based on assumptions developed using current data and expert opinion regarding the near future, and cannot be reasonably expected to reflect future emissions with 100% accuracy . C hanges that may occur in the distant future ( i.e., post- 2020) , such a s regulatory measures and market events, will likely impact future emissions.
 Scenarios 1 through 3 in EPA’s Vintaging Model does not account for reductions in emissions that may occur as a result of using hydrocarbons as a replacement for HFCs . Factors such as refrigerant price, charge size restrictions, and advancements in leak-tightness of ref/AC systems are not adjusted for in the modeling. Consequently, hydrocarbon emission projections are considered to be conservative.
 Although 2030 was chosen at the analysis year for this assessment because the hydrocarbon refrigerants were assumed to reach maximum market penetration by this time, some larger pieces of equipment with long lifetimes (i.e., lifetimes larger than 18 years) would not yet have reached end -of- life by 2030. Therefore, the effects of the disposal emissions from these pieces of equipment are not factored into this analysis . It should also be noted, however, that the remaining refrigerant charge in these large pieces of equipment are also mo re likely to be recovered given its economic value. 

### 5.2 **Air	Quality Modelling** 15

 The air quality modeling used in this study was at 36 - km resolution , as used in the Corporate Average Fuel Economy Standards, Passenger Cars and Light Trucks, Model Years 2017–2025, Final Environmental Impact Statement (NHTSA, 2012). In Appendix E: Air Quality Modeling and Health Impacts Assessment for Proposed Corporate A verage Fuel Economy Standards for Passenger Cars and Light Trucks: Model Years 2017 –2025, the model performance evaluation is discussed stating that, " EPA evaluated CMAQ model performance for the 2005 base year as part of the air quality modeling analysis to support the rulemaking for light- duty vehicle greenhouse gas emissions standards for MYs 2012 - 2016 (EPA, 2010). Overall, the performance for the 2005 modeling platform was similar to that for other national - and regional -scale applications, and the mod el was able to reproduce historical concentrations of ozone and PM2.5 with low bias and error results. " All meteorological and emission inventory files were taken directly from the NHTSA study . The only modification was to include the emission changes due to refrigerants, as discussed in Section 2. Higher grid resolution ( i.e., smaller grid cell) may potentially show higher ozone concentrations due to the mixing of air at the coarser resolution, however most refrigerant emissions are widely dispersed over a grid cell , so th e effect of this limitation on the overall modeling results is likely minim al .  Further climate change impacts will result in region -specific changes that may impact ozone production rates. F or example, increase (or decrease) in local cloud cover would lead to decrease (increase) local photolysis rates, resulting in reduced (increased) ozone production.
 It is possible that larger impacts of VOC concentrations could have been noted if additional VOClimited areas in the U.S. were modeled (e.g., Chicago) . However, it is very unlikely that impacts for those areas would exceed that for Los Angeles . While t he higher ozone concentrations observed in Los Angeles (8 - hour ozone [2008] design value is 112 ppb; Chicago is 77 ppb) depends upo n the local VOC-to - NO x ratio, it tend s to be more sensitive to a given change in VOC. Therefore, while it is possible that a higher ozone value may have occurred in Chicago than Los Angeles on a given day, i t is more likely that the Los Angeles area will h ave experienced a greater change in ozone due to increased VOCs over the course of the ozone season.
 The changes in standards for other pollutants such as air toxics or criteria pollutants could affect the ozone precursor emissions. For example, EPA rece ntly lowered the 1 - hour NO 2 standard to 100 ppb and could potentially lower this value again in the future to 80 ppb as initially proposed. In order to meet this standard, significant NO x emission reductions may be required, thus impacting the potential production of ground level ozone. The ozone air quality standard may be lowered in the future (historically the standard has been lowered a number of times) and would require additional red uctions of ozone precursor emissions, which c ould increase the importance of hydrocarbon refrigerants to the production rate for ozone . 7 

## 6 **Summary	of	Findings** From the analysis summarized in the previous sections of this report, it is concluded that n on att ainment resulting from hydrocarbon refrigerant emissions is not likely to be a major concern for local air quality. Hydrocarbon refrigerants could potentially increase ground level ozone by less than 1%

7 In August 2012, EPA published their first external draft policy assessment for the review of the ozone standard which suggested some potential lowering of the ozone standard ; however no final action has occurred on a new primary ozone standard.16

under Scenario 4, but up to a 9% increase on a given day for the most reactive hydrocarbons (propylene) in the most extreme case. However, in most cases this upper bound level of increase is not likely, as most ozone nonattainment areas are not VOC- limited (i.e., the formation of ozone in these areas a re not by limited by VOC emissions, but by other compounds such as nitrogen oxides [NO x] ) . In fact, Scenario 4, the “ most realistic” scenario for hydrocarbon refrigerant emission usage , showed a less than 0.2% increase in ground level ozone for the most extreme case. Future changes that could alter these findings include: changes in cloud cover from global warming which could increase or decrease ground level ozone production; and future emission reduction measures that may be required to reduce ozone precursors which would could increase the relative importance of the hydrocarbon refrigerants on the production of ground level ozone . 

## 7 **References** Intergovernmental Panel on Climate Change (IPCC). 2005. Safeguarding the Ozone Layer and the Global Climate System : Issues Related to Hydrofluorocarbons and Perfluorocarbons. Available at: http://www.ipcc.ch/publications_and_data/_safeguarding_the_ozone_layer.htm . MACS. 2009. Email communication between Elvis Hoffpauir, MACS and Karen Thundiyil, EPA. 10 March. National Highway Traffic Safety Administration (NHTSA), 2012. Final Environmental Impact Statement, Corporate Average Fuel Economy Standards, Passenger Cars and Light Tr ucks, Model Years 2017–2025, Appendix E: Air Quality Modeling and Health Impacts Assessment. NHTSA, July 2012. United States Environmental Protection Agency (EPA). 2008. Vintaging Model, Version VM IO File v4.2 10-07 -08. United States Environmental Protection Agency (EPA). 2010. Operational Guidance Document CMAQ 4.7.1 Available at www.cmascenter.org . United States Environmental Protection Agency (EPA). 2012. “Air Quality: Revision to Definition of Volatile Organic Compounds — Exclusion of trans - 1,3,3,3 -tetrafluoropropene .” Final Rule. 40 CFR Part 51. EPA- HQ- OAR- 2010-0605; FRL-9679 - 2. June 22, 2012. Available online at: http://www.gpo.gov/fdsys/pkg/FR
- 2012 -06 - 22/html/2012
- 15347.htm17



## Appendix	A

**Table A -**  **1. Scenarios 1, 2, and 3**  **Isobutane and Propylene Modeling Assumptions SNAP End**  **- Use**  **Vintaging Model End**  **- Use**  **Size Classification Annual**  **Leak Rate Disposal Release**  **Rate^** Motor Vehicle Air Conditioning (MVAC) MVAC L ight - duty Vehicle* Small 18 % 100%

MVAC L ight - duty T rucks* Small 1 8% 100% School & Tour Buses * Small 10% 100% Transit Buses * Small 10% 100% Trains * Small 2 % 100%

Chillers Centrifugal Chillers ** Large 2 % 10%

Positive Displacement Chillers ** Large 1 .5 % to 2 .5% 10% Screw Chillers ** Large 1 % 10% Scroll Chillers ** Large 0.5 % 10% Reciprocating Chillers ** Large 1.5 % 10% Industrial Process Refrigeration Systems Industrial Process

Refrigeration Large 3 % to 7.5 % 10% to 20% Cold Storage Warehouses Cold Storage Large 8 % to 1 6 % 10% Retail Food Refrigeration Large Retail Food Large 14% to 2 8 % 10%

Medium Retail Food Small 8 % to 1 5 % 100% Small Retail Food Small 1% 100% Ice Makers Small 5 % 100% Refrigerated Transport Refrigerated Transport Small 15 % to 20 % 100% Household Refrigerators and Freezers Refrigerated Appliances Small 1 % 100% Residential Dehumidifiers Dehumidifiers Small 0.50% 100%

Residential and Light Commercial Air Conditioning and Heat Pumps Window Units Small 0. 65 % 100%

Residential Unitary AC Small 11 % 100% Small Commercial Unitary AC Small 9 % 100% Large Commercial Unitary AC Small 8 % 100% Water & Ground Source HPs Small 4% 100% P ackaged Terminal AC/Packaged Terminal Heat Pumps (PTAC/PTHP ) Small 4% 100% ^The assumed disposal release rates are dependent upon the size of the equipment. Equipment that is considered small (i.e., with a charge size less than 200 kg) are assumed to have a 100% release of the charge upon disposal. Equipment that is considered large (i.e., a charge size large r than 200 kg) has a disposal release rate that is consistent with what is currently assumed in the Vintaging Model for HFC refrigerants. *Excluded from Scenario 1 and Scenario 2 **Excluded from Scenario 2

## Appendix **B**

**Table B** **- 1:**  **Scenario 4 Modeling Assumptions**  **SNAP End -**  **Use Vintaging** 

**Model End**   ** Use** **HC** ***** **Market Penetration** ** **Charge Size Annual**  **Leak Rate**  **Disposal**

**Release Rate** 
Retail Food Refrigeration Medium

Retail Food Propane 100% 1,500 to 12,500 g 8 % to 1 5 % 100% Small Retail Food*** Propane 33% 150 g 1% 100%

R-441A 33% 150 g 1% 100% Isobutane 33% 150 g 1% 100% Ice Makers Propane 100% 50 g 5 % 100% Refrigerated Transport Refrigerated

Transport R-441A 100% 2,130 g 15 % to 20% 100% Household Refrigerators and Freezers Refrigerated

Appliances Isobutane 33% 50 g 1 % 100%

Propane 33% 50 g 1 % 100% R-441A 33% 50 g 1 % 100% Residential Dehumidifiers Dehumidifiers None None None 0.50% 100%

Residential and Light Commercial Air Conditioning and Heat P umps Window

Units R-441A 33% 1 kg 0. 65 % 100%

R-443A 33% 1 kg 0. 65 % 100% Propane 33% 1 kg 0. 65 % 100% Water & Ground Source HPs R-443A 33% 1 kg 4% 100%

Propane 33% 1 kg 4% 100% R-441A 33% 1 kg 4% 100% PTAC/PTHP R-443A 33% 1 kg 4% 100%

R-441A 33% 1 kg 4% 100% Propane 33% 1 kg 4% 100% *R -441A is a blend consisting of propane, n - butane, isobutane, and ethane; R -443A consists of propylene, propane, and isobutane. For purposes of this assessment, both R -441A and R -443A were considered to only contain the components included in this analysis, propane, isobutane, and propylene. **In the absence of market penetration projections, it was assumed that the market was equally divided by the number of hydrocarbon substitu tes available for each end - use . ***Water coolers and vending machines were assumed to be included under small retail food .