## MEMORANDUM

To: Margaret Sheppard, U.S. EPA

CC: Chenise Farquharson, Rebecca von dem Hagen, U.S. EPA

From: Kasey Knoell, Becky Ferenchiak, Ed Carr, Mark Wagner, ICF International

Date: March 21, 2016

Re: Follow

- on Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentration s (EPA Contract Number EP

- W

- 10

- 031 Task Order 4 05 , Task 01)

In response to technical direction receiv ed from EPA, ICF ha s prepared a follow

- on to the February 2014 Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentrations [EPA

- HQ

- OAR

- 2013

- 0748

- 0003]. The February 2014 analysis examined the impacts of four different scenarios modeling the use and emissions of hydrocarbon refrigerants in various refrigeration and air conditioning (ref/AC) end

- uses. In this analysis, r efrigerant emissions were modeled for t wo additional hydrocarbon refrigerant emission scenarios from th e U.S. EPA’s Vintaging Model (VM) ( VM_IO file_ v 4 .4_ 10.13.14 ) and their impacts on ground level ozone were modeled using EPA’s Community Multi scale Air Quality (CMAQ) model ( version 5.0.2 )

. Releases of hydrocarbon refrigerants were modeled in Los Angeles, H ouston, and Atlanta

. In addition, the most conservative and most realistic scenario s from the February 2014 analysis were re

- run to reflect updated versions of the VM, CMAQ, meteorology
, and
, most importantly
, a 2040 emissions baseline

. The remainder of this memorandum summarizes the results of this assessment

. A quantitative analysis of the 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 

# Potential Impacts of Hydrocarbon Refrigerants

on Ground

- Level Ozone Concentrations

1 Executive Summary

As a follow

- on to the February 2014 Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Lev el Ozone Concentrations [EPA

- HQ

- OAR

- 2013

- 0748

- 0003], r eleases of hydrocarbon refrigerants were modeled to reflect additional U.S. EPA Significant New Alternatives Policy (SNAP) Program applications for the use of hydrocarbons in various refrigeration and air conditioning ( ref/AC ) end

- uses. Hydrocarbon refrigerants were modeled in Los Angeles, Houston, and Atlanta under two new emissions scenarios. Specifically, propylene was modeled under a more conservative emissions scenario for cold storage and multiple air

- conditioning end

- uses (Scenario 5). , and a more realistic emissions scenario was also modeled, which considered more likely transitions to a variety of hydrocarbon refrigerants (i.e., propane, R

- 441A, and R

- 443A) by end

- use within cold storage and mul tiple AC end

uses (Scenario 6). 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 Quality (CM AQ) 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 ydrocarbon refri gerant s under the most conservative scenario (Scenario 1 ) could potentially increase ground level ozone by up to 11 % compared to the national ozone standard, with increases between 4% and 6 % for the two new scenarios examined in this analysis (Scenarios 5 and 6 )

. The most realistic scenario (Scenario 4) results in a potential increase in ground level ozone of up to 4% compared to the national ozone standard. The analysis performed is based on several assumptions and projections that cannot be know n with certainty at this time. These limitations are associated with both the unknown market penetration of alternatives and future climate conditions, among other factors.



## 2 Introduction
The February 2014 Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentrations [EPA

- HQ

- OAR

- 2013

- 0748

- 0003] analyzed the potential air quality impacts from three conservative hydrocarbon emission scenarios and one more realistic scenario , as follows: 1) Scenario 1 : the entire ref/AC sect or : chillers, motor vehicle air conditioners (MVACs) (i.e., light

duty trucks and vehicles, trains, transit buses, school buses, and tour buses), residential and light3

commercial AC and heat pumps, 1 retail food, 2 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 ; 3 and 4) Scenario 4: the ref/AC sector for end

- use applications in which a SNAP submission has been received for a hydrocarbon or in which a UL Standard addressing flammable refrigerant is in place. This analysis con siders two additional scenarios that model the use of propyl ene and a mixture of hydrocarbon refrigerants and blends in various ref/AC applications (described below in Section 3.1 )

. Furthermore, emission estimates from Scenario 1 and Scenario 4 were remodeled to account for updates to the C MAQ model, improved meteorology characterization and most importantly 2040 emission projections and to enable comparison with pre vious emission scenarios.

Th e remainder of this report summarizes the methodology used and results in the following order:

 Sect ion 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



## 3 Hydrocarbon Emission Scenario s

As a follow

- on to the four scenarios modeled in the February 2014 analysis, r eleases of hydrocarbon refrigerants were modeled in Los Angeles, Houston, and Atlanta under two new emissions scenarios. Specifically, propylene was modeled under a more conservative emissions scenario for the ref/AC sector (Scenario 5)

. A more realistic emissions scenario was also modeled, which considered more likely transitions to a variety of hydrocarbon refrigerants (i.e., propane, R

- 441A, and R

- 443A ) by end

- use in the
sector (Scenario 6) . The two new emission scenarios considered as a continuation of the February 2014 analysis are as follows: 5) Scenario 5 : applications in the ref/AC sector: cold storage warehouses
, chillers, 4 a nd residential and light commercial AC and heat pumps (excluding window AC and large commercial unitary AC) 5 and

1 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.

2 The retail food end

- use includes the following applications: ice makers, small retail food systems, medium retail food systems, and large retail food systems.

3 Chillers are large

- scale air conditioning systems for large commercial and institutional buildings, such as for office buildings, hotels, hospitals, and the like.

4 Chillers are large

- scale air conditioning systems for large commercial and institutional b uildings, such as for office buildings, hotels, hospitals, and the like.

5 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 comme rcial unitary AC, packaged terminal AC and heat pumps (PTAC/PTHP), and water and ground source heat pumps.4

6) Scenario 6 : applications assumed in Scenario 5 , with the addition of window AC and large commercial unitary AC

. As mentioned above, the most conservative scenario from the February 2014 analysis (Scenario 1) and the most realistic scenario (Scenario 4) were re

- run to reflect updated modeling parameters (see discussion below)

. T o estimate their potential impact on ground

- level ozone con centration, the national scale hydrocarbon emissions from each scenario were estimated using EPA’s Vintaging Model (VM)

. 6 These national emissions were then proportional ly scaled to each urban area by population by county. For Los Angeles
, three counties w ere 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 emissi ons 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 It was assumed that the hydrocarbon refrigerants would enter the market a t a minimal level (i.e., 1%) in 2016, and reach 100% market penetrat ion by 2025. Emissions were estimated using the latest version of the VM ( VM_IO file_ v 4.4_ 10.13.14 )
, 7 which included updates to several ref/AC end

- uses, including MVACs, window AC units, ice makers, and small retail food end

- uses. 8 The year 20 4 0 was chosen as the analysis year f or all scenarios to conservatively estimate the full impact of hydrocarbons

. The equipment being modeled have longer lifetimes (i.e., 15 to 27 years ) and hydrocarbon refrigerants are not assumed to reach full penetration of new syste ms until 2025 , so emissions do not reach a roughly steady state until around 2040 (as opposed to the previous February 2014 analysis in which steady state emissions were reached in 2030) . By 2040, the hydrocarbon refrigerants have reached full market penet ration and equipment containing hydrocarbon refrigerants ha s begun to reach the end of its useful life.

To maintain comparability to th e previous February 2014 analysis, 2040 emission estimates from Scenario 1 and Scenario 4 were recalculated based on the latest ver sion of the Vintaging Model and

were analyzed. For this analysis, a 20 4 0 nationwide emission inventory was available for other emission sources and was used to estimate baseline ozone concentration s (without hydrocarbon refrigerants) ( EPA , 20 1 6 )

.
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 assumed that 11.9% of annual emissions occurred during each

6 EPA’s Vintaging Model estimates the annual chemical emissions from industry sectors that have historically used ODS, including AC, refrigeration, foams, 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 t ransition from ODS to alternatives. The model version used in this analysis is VM_IO file_V4.4_10.13.14.

7 The February 2014 analysis was based on Vintaging Model version VM_IO file_V4.4_11.6.12.

8 For the MVAC light

- duty vehicle (LDV) and light

- duty truck s (LDT) end

- uses, operational and servicing leak rates were reduced based on a review of recent literature. For the small retail food and ice makers end

- uses, revisions were made to the overall stock, growth rates, assumed transition scenarios, and lifetim es based on research on substitutes and growth in the market. For window AC , a review of air conditioner sales data from 2002 through 2012 increased the quantity of window AC equipment introduced into the market for 2002 and 2004 through 2008, while decrea sing the quantity of equipment sold into the market for 2003 and 2009 through 2012.5

month from April to August

. E missions of refrige rant are reasonably anticipated to occur primarily during the warmer s pring and s ummer months, when air conditioning equipment is increasingly used. For example, e missions d ue to servicing MVACs are expected to be higher during the spring and summer, with up 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 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 throughout the y ear

. Equipment in end

- uses with a smaller charge size (i.e., end

- uses with a charge size less than 200 kg) were assumed to have a 100% relea se of refrigerant upon disposal

. 9 D isposal release rates for equipment in end

- uses with greater charge sizes (i.e., chillers) and serv ic ing release rates for all end

- uses

were assumed to remain consistent with current VM assumptions, due to assumed regulations and financial incentives for the end

- user. This is discussed further in the February 2014 assessment. The read er is referred to Appendix A for a summary of detailed assumptions used in this analysis

. 

### 3.2 Scenario s 1 and 5 Propylene is currently being proposed for use in a variety of ref/AC end

- uses and exhibits the highest maximum incremental reactivity ( MIR ) 10 of hydrocarbons

. Scenario 1 from the February 2014 analysis evaluated t he most conservative impact that releases of hydrocarbons could have on ground

- level

ozone . This scenario assumed use and release of propylene across the entire ref/A C sector and was updated to illustrate projected 2040 emissions

. The analysis presented here also conservatively estimates the impact s of emissions in end

- uses for which propylene is mo st likely to be used (Scenario 5) and assumes complete release from sma ller end

- uses at disposal

. Table 1 presents the monthly emissions in 20 4 0 which were assumed under Scenarios 1 and 5

.

9 In April 2015, EPA published a final rule to exempt four hydrocarbon refrigerant substitutes from specific end

uses, subject to use conditions, from Clean Air Act Section 608's prohibition on venting, release, or disposal, including: (1) isobutane and R

- 441A in retail food refrigerators and freezers (stand

- alone units only); (2) propane in household refrigerators, freezers, and combination refrigerators and freezers; (3) e thane in very low temperature refrigeration equipment and equipment for non

- mechanical heat transfer; (4) R

- 441A, propane, and isobutane in vending machines; and (5) propane and R

- 441A in self

- contained room AC for residential and light commercial AC and heat pumps.

10 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

- leve l ozone formation is considered an urban issue

. Please refer to the February 2014 analysis for additional information.6 Table 1 : 20 4 0 National Refrigerant Emissions under Scenarios 1 and 5

Month Scenario 1 Emissions (MT) Scenario 5 Emissions (MT) Propylene Propylene January 10,280 4,716 February 10,280 4,716 March 10,280 4,716 April 15,127 8,576 May 15,127 8,576
June 15,127 8,576 July 15,127 8,576 August 15,127 8,576 September 10,280 4,716 October 10,280 4,716 November 10,280 4,716 December 10,280 4,716 Note: Emissions of isobutane and propylene are equivalent; s haded months indicate those used in the analysis

.

Figure 1 presents the percent contribution of propylene emissions by end

- use under Scenarios 1 and 5

. As illustrated in these charts, residential and light commercial AC end

- uses presented the most significant source of emissions across all four modeled scenarios.

Figure 1 . Percent Contribution of End

- Use to Total Emissions under Scenarios 1 and 5

Note: Emissions under the residential an d light commercial AC and heat pumps end

- use (Res and Comm AC) consists of 48 % from residential unitary AC, 4 % from window AC, 2 % from small commercial unitary AC, 0. 3 % from large commercial unitary AC, 0 .3 % from PTACs, and 0. 1 % from water and ground sourc e HPs (relative to total emissions in Scenario 1)

. Emissions under the MVAC end

- use consists of 8 % from light

- duty vehicles, 1 1 % 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 86% from residential unitary AC and 5% from small commercial unitary AC, 1 % from PTACs, and 1 % from water and groun d source HPs (relative to total emissions in Scenario 5 )

. Window AC and large commercial unitary AC were not included in this scenario. Retail Ref 5% Household Ref 1%

IPR 7%

Transport Ref 10% Dehumidif

ers <1% MVAC 19%

Chillers 2% Res and Comm AC 55% Cold

Storage 1% 

### Scenario 1 Cold Storage 3%

Chillers 5% Res and Comm AC 92% 

### Scenario 57



### 3.3 Scenario 4 Scenario 4 from the February 2014 analysis evaluated the most realistic impact that releases of hydrocarbons (i.e., propane, isobutane, or propylene) could have on ground

- level ozone . This s cenario assumed use of hydrocarbons only 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 and was updated to show 2040 emissions. Estimated emissions for this scenario are shown in Table 2

.

Table 2 : 20 4 0 National Refrigerant E missions of under Scenario 4

Month Scenario 4 Emissions (MT) (“Most Realistic Scenario”) Propane Isobutane Propylene
January 1,534 99 198 February 1,534 99 198
March 1,534 99 198 April 1,575 102 207 May 1,575 102 207

June 1,575 102 207 July 1,575 102 207 August 1,575 102 207 September 1,534 99 198
October 1,534 99 198
November 1,534 99 198
December 1,534 99 198 Note: Shaded months indicate those used in the analysis Figure 3 presents the percent contribution s of each refrigerant and each end

- use to the total emissions under Scenario 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 58% from window AC and 3 % from PTACs (relative to total emissions in the Scenario 4). Retail Food 10%

Transport Ref 25%

Household Ref 3% Res and Comm AC 62% 

### By End

- Use

Propane 84% Isobutane 5%

Propylene 11% 

### By Refrigerant8



### 3.4 Scenario 6 An additional, more realistic scenario ( Scenario 6 ) was developed to model the type of hydrocarbon or blend (i.e., R

- 441A, R

- 443A, or propane) likely to be used in ref/AC end

- uses

. The reader is referred to Appendix B for additional information regarding the assumptions us ed under this scenario. In addition, Appendix C presents the relative contribution to total emissions of each refrigerant by end

- use. Estimated e missions for this scenario are shown in Table 3

.

Table 3 : 20 4 0 National Refrigerant Emissions of under Scenario 6

Month Scenario 6 Emissions (MT)

Propane Isobutane Propylene Ethane n - Butane
January 2,157 237 2,886 5 64 February 2,157 237 2,886 5 64
March 2,157 237 2,886 5 64 April 3,667 423 5,107 6 69 May 3,667 423 5,107 6 69

June 3,667 423 5,107 6 69 July 3,667 423 5,107 6 69 August 3,667 423 5,107 6 69 September 2,157 237 2,886 5 64
October 2,157 237 2,886 5 64
November 2,157 237 2,886 5 64
December 2,157 237 2,886 5 64 Note: Shaded months indicate those used in the analysis Figure 3 presents the percent contribution s of each refrigerant and each end

- use to the total emissions under S cenario 6

. Figure 3 . Percent Contribution to Total Emissions under Sce nario 6

Note: Emissions under the residential and light commercial AC and heat pumps end

- use (Res and Comm AC) consists of 79 % from residential unitary AC, 8% from window AC, 5% from small commercial unitary AC, 0.5% from large commercial unitary AC, 1% from PTACs, and 1% from water and ground source heat pumps (relative to total emissions in the Scenario 6 ). Cold Storage 3%

Chillers 4% Res and Comm AC 93% 

### By End

- Use

Propane 40%

Isobutane 4% Propylene

55% Ethane 0%

n

- Butane 1% 

### By Refrigerant9



## 4 Impact on Ground Level Ozone Concentration s Using EPA’s CMAQ photochemical model version 5.0.2 , a simulation of the potential ground

- level oz one 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 comparison of the results to the national standar ds of ambient air quality. This methodology is consistent with the approach used in the February 2014 analysis; however, updated emission estimates and model versions were used when available.


### 4.1 Methodology

T he projected emissions of propylene under Scenari os 1 and 5 , and the mix ture of hydrocarbons under Scenarios 4 and 6 were input into the CMAQ to predict impacts on 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 1 , Table 2 , and Table 3 ) , as well as warmer air temperature and l onger period of sunlight which increase the potential for ozone creation.

The maximum increase in 8

- hr ozone concentrations w as 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 national emission estimates to estimate reasonable conservative impacts.

The CMAQ simulation was performed using 20 11 hourly meteorological data at 36

- km horizontal resolution with 14 vertical layers to identify the maximum increase in 8

- hour ground level ozone concentrations. The model used the carbon bond 05 chemical mechanism which explicitly inclu des 156 chemical reactions (EPA, 2010). T he 20 4 0 nationwide emission inventory ( EPA , 201 6 ) , as previously mentioned, was readily available and used to estimate the baseline ozone concentration ( i.e., without hydrocarbon refrigerant)

. This inventory refle cts the best estimate of nationwide 2040 hydrocarbons and NO x emissions whose ratio regulates the speed and production of ground

- level ozone formation. Split factors for use in the carbon bond 05 chemical mechanism for butane, ethane, isobut a ne, propylene , and propane were determined from the Emit Worksheet in the emitdb.xls workbook f orm

. 11 The split factors and related parameters used in processing the refrigerant emissions are presented in Table 4 below.

Table 4 : Mass Fractions of CB05 Species per gram of Emitted Compound (g/g)

Compound P araffin

(PAR) Molecular

Weight (g/mole) O lefins

(OLE) Molecular

Weight (g/mole) Ethane

(ETHA) Molecular

Weight (g/mole) Unreactiv

e (UNR) Molecular

Weigh t (g/mole)
Butane 1.0 14.53 0.0

-- 0.0

-- 0.0

-- Ethane 0.0

-- 0.0

-- 1.0 30.07 0.0

-- Isobutane 1.0 14.5 4 0.0

-- 0.0

-- 0.0

-- Propylene 0.34 14.03 0.66 28.06 0.0

-- 0.0

-- Propane 0.5 14.7 0 0.0

-- 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.

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

.10



### 4.2 CMAQ Results

Table 5 s ummarizes 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 20 4 0 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) Propylene
Scenario 1 7.80 2.13 1.14

Scenario 5 4.49 1.21 0.65 Combination of Propane, Isobutane, Propylene, Ethane, and n

- Butane
Scenario 4 2.48 0.76 0.44

Scenario 6 2.57 0.77 0.44 ppb = parts per billion; O 3 = ozone

For Los Angeles, propylene, as anticipated due to its high MIR, resulted in the most significant increases in ground

- ozone concentrations ; under Scenario 1
, results for the Los Angeles region show that the maximum increase in the 8

- hr ozone concentration is 7.80 ppb and under Scenari o 5, the maximum increase in the 8

- hr ozone concentration is 4.49 ppb

. Scenario 4 (i.e., the most realistic scenario) resulted in a maximum increase of 2.48 ppb in the 8

- hr ozone concentration. Scenario 6 resulted in a peak 8

- hr ozone increase of 2.57 ppb. This increase in ozone is estimated to be a bout 9 5% associated with the use of propylene as a refrigerant and 4 % from propane under this scenario. For all four scenarios, Los Angeles showed the largest ground

- ozone concentration increases of the three cit ies modeled

. Figure 4 shows the maximum increases and spatial extent of the 8

- hour ozone concentration increase for propylene in Scenario 1 and Scenario 5 and the hydrocarbon combination in Scenario 4 and Scenario 6 for Los Angeles

. In these figures, red, orange, and yellow represent modeled changes in ozone concentrations.11 Figure 4 . Maximum 8

- hour O zone I ncrease for Los Angeles in 20 4 0 (C lock

- wise from Left: Scenario 1 Propylene , Scenario 5 Propylene, Scenario 4 Combination, and Scenario 6 Combination )

For Houston under Scenario 1 , propylene resulted in a maximum increase in the 8

- hr ozone concentration of 2.12 ppb . For Scenario 5 , propylene results for the Houston region show that the maximum increase in the 8

- hr ozone concentration is 1.21 ppb

. Scenario 4 (i.e., the most realistic scenario) resulted in a maximum increase of 0.76 ppb in the 8

- hr ozone concentration

. Scenario 6 (i. e., t he more realistic scenario) resulted in a peak 8

- hr ozone increase of 0.77 ppb downwind of Houston. Figure 5 shows the maximum increases and spatial extent of the 8

- hour oz one concentration increase for propylene in Scenario 1 and Scenario 5 and the hydrocarbon combination in Scenario 4 and Scenario 6 for Houston. The further downwind location of the maximum increase in Scenario 4 and 6 reflects the slower reactivity of the refrigerant mixture and also o ccurs on a different day from each other as well as relative to Scenario 1 and 5. In these figures
, red , orange , and yellow shading represent modeled changes in ozone concentrations.12 Figure 5

. Maximum 8

- hour O zone Increase for Houston in 20 4 0 (Clock

- wise from Left: Scenario 1 Propylene, Scenario 5 Propylene, Scenario 4 Combination, and Scenario 6 Combination )

For Atlanta, propylene under Scenario 1 resulted in a maximum increase in the 8

- hr ozone concentration of 1.14 p pb . For Scenario 5 , results for the Atlanta region show that the maximum increase in the 8

- hr ozone concentration is 0. 65 ppb

. Scenario 4 (i.e., the most realistic scenario) resulted in a maximum increase of 0.44 ppb in the 8

- hr ozone concentration. Scenario 6 (i.e., a more realistic scenario) resulted in a peak 8

- hr ozone increase of 0.44 ppb for Atlanta. Figure 6 shows the maximum increases and spatial extent of the 8

- hour ozone concentration increase for propylene in Scenario 1 and Scenario 5 and the hydrocarbon combination in Scenario 4 and Scenario 6 for Atlanta

. The further downwind location of the maximum increase in Scenario 4 and 6 refle cts the slower reactivity of the refrigerant mixture under this scenario and also occurs on a different day. In these figures, yellow, orange, and red shading represent modeled changes in ozone concentrations.13 Figure 6

. Maximum 8

- hour O zone I ncrease for Atlanta in 20 4 0 (Clock

- wise from Left: Scenario 1 Propy lene, Scenario 5 Propylene, Scenario 4 Combination, and Scenario 6 Combination )



### 4.3 Comparison to National Ambient Air Quality Ozone Standard The current national ambient air quality 8

- hour average ozone standard (NAAQS) is 7 0 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 7 0 ppb 8

- hr N ational A mbient A ir Q uality O zone S tandard Propylene (Scenario 1) 7.8 11.1 % Propylene (Scenario 5) 4.5 6.4 % Combination (Scenario 4) 2.5 3.5%
Combination (Scenario 6 ) 2.6 3.7 % ppb = parts per billion ; O 3 = ozone


## 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 an d 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 HFC s across the ref/AC sector

. However, the introduction of additional 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 estimate s up to 2050

. However, projected estimates 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 as regulatory measures and market events , will likely impact future emissions.

 Scenarios 5 and 6 in EPA’s Vintaging Model do not account for reductions in emissions that may occur as a result of using hydrocarbons a s a replacement for HFC s

. 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.



### 5.2 Air Quality Mode ling

 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 VOC

limited 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 upon the local VOC

- to

- NO x ra tio, 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 have experienced a greater change in ozone due to increased VOCs over the course of the ozone season.15

 The changes in standards for other pollutants such as air toxics or criteria pollutants could affect the ozone precursor emissions. For example, EPA recently 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 leve l 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 reductions of ozone precursor emissions, which c ould increase the importance of hydrocarbon ref rigerants to the production rate for ozone

. 

## 6 Summary of Findings

From the analysis summarized in the previous sections of this report, it is concluded that n on

attainment resulting from hydrocarbon refrigerant emissions could be a concern for local air qua lity under the more conservative propylene scenarios. Propylene refrigerant could potentially increase ground level ozone by a maximum of 11 % on a given day in the most extreme case (Scenario 1) and up to a 6% increase for the more realistic propylene

- only scenario (Scenario 5). The more realistic Scenario 6 showed almost a 4% increase in ground level ozone. I n most cases t hese maximum level s of increase

are not likely, as most ozone nonattainment areas are not VOC

- limited (i.e., the formati on of ozone in these areas is not limited by VOC emissions , but by other compounds such as nitrogen oxides [NO x ] )

. Scenario 4, the “most realistic” scenario for hydrocarbon refrigerant emission usage, showed a maximum increase of less than 4% in ground le vel ozone. 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
precu rsors which would could increase the relative importance of the hydrocarbon refrigerants on the production of ground level ozone

.16



## 7 References
Intergovernmental Panel on Climate Change (IPCC). 2005. Safeguarding the Ozone Layer and the Global Climate Sys tem: 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.

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

— E xclusion 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.htm United States Environmental Protection Agency (E PA). 2016. Draft Final Environmental Impact Statement, Phase 2 Greenhouse Gas Emission Standards for Medium

- and Heavy

- Duty Engines and Vehicles

. Washington, D.C. ( In progress ).17



## Appendix A

Table A

- 1. Scenario 5 Propylene Modeling Assumptions

SNAP End

- Use Vintaging Model End

- Use Size Classification Annual Leak Rate Disposal Release Rate^

Chillers Centrifugal Chillers Large 2 % 10%

Screw Chillers Large 1 % 10%
Scroll Chillers Large 0.5 % 10% Reciprocating Chillers Large 1.5 % 10% Cold Storage Warehouses Cold Storage Large 8 % to 1 6 % 10%

Residential and Light Commercial Air Conditioning and Heat Pumps Residential Unitary AC Small 11 % 100%

Small Commercial Unitary AC Small 9 % 100%

Water & Ground Source HPs Small 4 % 100%

P ackaged Terminal AC/Packaged Terminal Heat Pumps (P TAC/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 la rge (i.e., a charge size larger than 200 kg) has a disposal release rate that is consistent with what is currently assumed in the Vintaging Model for HFC refrigerants.

## Appendix B

Table B

- 1: Scenario 6 Modeling Assumptions

SNAP End

- Use Vintaging Model End

- Use HC * Market Penetration** Annual Leak

Rate Disposal

Release Rate

Chillers Centrifugal Chillers Propylene 100% 2 % 10%

Screw Chillers Propylene 100% 1 % 10%
Scroll Chillers Propylene 100% 0.5 % 10% Reciprocating Chillers Propylene 100% 1.5 % 10% Cold Storage Warehouses Cold Storage Propylene 100% 8 % to 1 6 % 10%

Residential and Light Commercial Air Conditioning and Heat Pumps Window Units R

- 441A 33% 0. 65 % 100%
R

- 443A 33% 0. 65 % 100% Propane 33% 0. 65 % 100% Residential Unitary AC R

- 443A 100% 11 % 100% Small Commercial Unitary AC R

- 443A 100% 9 % 100% Large Commercial Unitary AC R

- 443A 100% 8 % 100%
Water & Ground Source HPs R

- 443A 100% 4 % 100% PTAC/PTHP R

- 443A 100% 4 % 100%
*R

- 441A is a blend consisting of propane, n

- butane, isobutane, and ethane; R

- 443A consists of propylene, propane, and isobutane. **In the absence of market penetration projections, it was assumed that the market was equally divided by the number of hydrocarbon substitutes available for each end

- use

.2



## Appendix C

Table C

- 1: Relative Contributions to Total and VOC Emissions by Refrigerant for Scenario 6

SNAP End

- Use Vintaging Model End

- Use HC Relative Contribution to Scenario 2040 Emissions

Chillers Centrifugal Chillers Propylene 1.4%

Screw Chillers Propylene 1.5%
Scroll Chillers Propylene 0.4% Reciprocating Chillers Propylene 0.0% Cold Storage Warehouses Cold Storage Propylene 1.9%

Residential and Light Commercial Air Conditioning and Heat Pumps Window Units Propane 5.1%
Isobutane 0.3% Propylene 1.4%
Ethane 0.1%

n

- Butane 0.9%

Residential Unitary AC Propane 32.3%
Isobutane 4.0% Propylene 44.5%

Small Commercial Unitary AC Propane 1.9%
Isobutane 0.2% Propylene 2.6%

Large Commercial Unitary AC Propane 0.2%
Isobutane 0.0% Propylene 0.3%

Water & Ground Source HPs Propane 0.2%
Isobutane 0.0% Propylene 0.2%

PTAC/PTHP Propane 0.2%
Isobutane 0.0% Propylene 0.3%