8.1 High-GWP Gases

    Category ID Description EIC
    937 Soil Vapor Extraction & Air Stripping Various
    2289 Commercial - Aerosols - HFC-134a 49999531620000
    2290 Commercial - Aerosols - HFC-152a 49999531620000
    2291 Commercial - Fire Protection - CF4 (PFC-14) 49999531620000
    2292 Commercial - Fire Protection - HFC-125 49999531620000
    2293 Commercial - Fire Protection - HFC-236fa 49999531620000
    2294 Commercial - Fire Protection - HFC-227ea 49999531620000
    2295 Commercial - Foams - HFC-134a 49999531620000
    2296 Commercial - Foams - HFC-245fa 49999531620000
    2297 Commercial - - HFC-125 49999531620000
    2298 Commercial - Refrigeration and Air Conditioning - HFC-134a 49999531620000
    2299 Commercial - Refrigeration and Air Conditioning - HFC-143a 49999531620000
    2300 Commercial - Refrigeration and Air Conditioning - HFC-236fa 49999531620000
    2301 Commercial - Refrigeration and Air Conditioning - HFC-32 49999531620000
    2302 Commercial - Refrigeration and Air Conditioning - HFC-152a 49999531620000
    2303 Industrial - Aerosols - HFC-134a 49999531620000
    2304 Industrial - Aerosols - HFC-152a 49999531620000
    2305 Industrial - Fire Protection - CF4 (PFC-14) 49999531620000
    2306 Industrial - Fire Protection - HFC-125 49999531620000
    2307 Industrial - Fire Protection - HFC-236fa 49999531620000
    2308 Industrial - Fire Protection - HFC-227ea 49999531620000
    2309 Industrial - Foams - HFC-134a 49999531620000
    2310 Industrial - Foams - HFC-245fa 49999531620000
    2311 Industrial - Refrigeration and Air Conditioning - HFC-125 49999531620000
    2312 Industrial - Refrigeration and Air Conditioning - HFC-134a 49999531620000
    2313 Industrial - Refrigeration and Air Conditioning - HFC-143a 49999531620000
    2314 Industrial - Refrigeration and Air Conditioning - HFC-236fa 49999531620000
    2315 Industrial - Refrigeration and Air Conditioning - HFC-32 49999531620000
    2316 Industrial - Refrigeration and Air Conditioning - HFC-152a 49999531620000
    2317 Industrial - Solvents - CF4 (PFC-14) 49999531620000
    2318 Industrial - Solvents - HFC-245fa 49999531620000
    2319 Residential - Aerosols - HFC-134a 49999531620000
    2320 Residential - Aerosols - HFC-152a 49999531620000
    2321 Residential - Foams - HFC-134a 49999531620000
    2322 Residential - Foams - HFC-245fa 49999531620000
    2323 Residential - Refrigeration and Air Conditioning - HFC-125 49999531620000
    2324 Residential - Refrigeration and Air Conditioning - HFC-134a 49999531620000
    2325 Residential - Refrigeration and Air Conditioning - HFC-32 49999531620000
    2326 Transportation - Aerosols - HFC-134a 49999531620000
    2329 Transportation - Refrigeration and Air Conditioning - HFC-125 49999531620000
    2330 Transportation - Refrigeration and Air Conditioning - HFC-134a 49999531620000
    2331 Transportation - Refrigeration and Air Conditioning - HFC-143a 49999531620000
    2332 Transportation - Refrigeration and Air Conditioning - HFC-32 49999531620000
    2531 Industrial - Solvents - HFC-365mfc 49999531620000
    2532 Industrial - Solvents - HFC-43-10mee 49999531620000
    2533 Industrial - Solvents - Other PFC and PFE 49999531620000
    2534 Residential - Aerosols - HFC-227ea 49999531620000
    2556 Commercial - Aerosols - HFC-43-10mee 49999531620000
    2557 Industrial - Aerosols - HFC-43-10mee 49999531620000
    2558 Residential - Aerosols - HFC-43-10mee 49999531620000
    2562 Non- Agri./Consumer Pesticides - Pesticides - SO2F2 53054057100000

    Introduction

    This document describes the methodology used to estimate greenhouse gas (GHG) emissions from high-global warming potential (high-GWP) gases.

    The use of these gases was adopted to replace and phase out ozone-depleting substances that were depleting the stratospheric ozone layer, under the 1987 Montreal Protocol and 1990 Clean Air Act Amendments. These replacement gases, including hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), though not harmful to the ozone layer contribute significantly to global warming due to their high heat trapping ability and long persistence in the environment. Owing to these characteristics, these gases are classified as GHGs with high global warming potential (GWPs). The San Francisco Bay Area (SFBA) GHG inventory for high-GWP emissions is derived from the California Air Resources Board’s (CARB) statewide GHG emissions inventory, and the SFBA inventory assigns these emissions by source categories (category numbers 2289-2332, 2531-34, 2556-58) based on specific gases and their use across the Commercial, Residential, Industrial, and Transportation sectors. Processes in which these fluorine-bearing gaseous compounds (F-gases) are primarily used are refrigerants in air conditioning and refrigeration systems, blowing agents in foams, fire suppressants, aerosol propellants, and solvents for cleaning supplies. All the high-GWP gases included in this inventory are listed in the Trends section.

    Although high GWP gases are used in various industries and processes, their emissions calculation methodology relies on statewide emissions from CARB that are then apportioned to the Bay Area counties as described in this chapter with two exceptions, semiconductor manufacturing (category numbers # 2560-61 and 2622-26) and SF6 gases used in high-voltage switchgear which have their own methodology chapters.

    Methodology

    The high-GWP source categories are considered area sources as they account for fugitive emissions from distributed devices that are not typically permitted by the Air District and hence are not systematically or annually catalogued. The inventory development for these categories uses an area source calculation approach, since the process-level fugitive emissions are widely distributed across thousands of emission release points and not necessarily measured directly.

    The emissions data for these high-GWP gases come directly from CARB’s Greenhouse Gas Inventory (CARB, 2023; latest data for year 2021) following the same source category classification used by CARB. The general methodology used by CARB to calculate emissions for the base year for these categories is as follows:

    Base Year Emissionscounty,pollutant =

    Emissionsstate;national,pollutant × Control Factorpollutant × Fractioncounty × Fractionin District × GWPpollutant

    Where:

    • Base Years: are years for which activity / throughput data are available in order to calculate emissions.
    • Emissionsstate;national,pollutant: is the amount of emissions from a larger area (e.g., state or national level) to be allocated to a smaller regional area based on a proportional measure, such as the ratio of county to state population.
    • Emission Factorpollutant: is a factor that allocates a mass amount of emissions of a particular pollutant per unit of activity.
    • Control Factorpollutant: is a fractional ratio (between 0 and 1) that estimates reductions in emissions from adopted rules and regulations.
    • Fractioncounty: is the fraction of total regional emissions (between 0 and 1) estimated to be allocated to a particular county.
    • Fractionin District: The Air District jurisdiction covers only a portion of Solano and Sonoma County and, therefore, an additional allocation is applied to these counties that proportions each county’s emissions that are within Air District’s boundary.
    • GWPpollutant: is the Global Warming Potential of a particular GHG pollutant. The current version of the GHG emissions inventory incorporates the global warming potential (GWP) reported in the Fifth Assessment report of the Intergovernmental Panel for Climate Change (IPCC, 2014). The GWPs for the three principal GHGs are 1 for carbon dioxide (CO2), 34 for methane (CH4), and 298 for nitrous oxide (N2O), when calculated on a 100-year basis with climate-carbon feedback included.

    This approach allows derivation of emissions data for the years 2000-2021. Once base year emissions are determined, historical backcasting and forecasting of emissions relative to the base year emissions are estimated using growth profiles as follows:

    Current Year Emissionscounty = Base Year(s) Emissioncounty x Growth Factor

    Where:

    • Growth Factor: is a scaling factor that is used to derive historical emissions estimates for years for which activity data and/or emissions are not available, and to forecast emissions for future years, using surrogates that are assumed to be representative of activity and/or emissions trends.

    More details on the county distribution of emissions, emission factors and controls are provided in the following subsections:

    County Fractions

    As previously stated, the emission inventory for high GWP gases is based on a statewide inventory developed by CARB, which is then apportioned to the Bay Area. County level distribution factors are estimated from various sources including the California American Community Survey (ACS, 2024), CARB on-road emissions model EMFAC2021, and the Association of Bay Area Governments (ABAG) Plan Bay Area 2050 data to obtain metrics by county and state that are reflective of the sector assigned to each source category, in which the high GWP-gas emissions take place (see table below). For example, to estimate the fraction of high GWP used for air conditioning and refrigeration units, the Air District used average total households from ABAG. The distribution factor, a ratio of the county metric divided by the state metric, is then multiplied by the statewide total emissions to obtain county level emissions.

    Subsector

    County Fraction Data Source

    Residential

    ABAG Total Households averages for 2015-2020 (ABAG, 2021)

    Commercial

    California Employment Development Department: Service Providing Employment (EDD, 2024)

    Industrial

    California Employment Development Department: Goods Producing Employment (EDD, 2024)

    Transportation

    California EMFAC2021 model for Vehicle Miles Traveled for each county (CARB, 2024)

    ID Description ALA CC MAR NAP SF SM SNC SOL SON
    2289 Commercial - Aerosols - HFC-134a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2290 Commercial - Aerosols - HFC-152a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2291 Commercial - Fire Protection - CF4 (PFC-14) 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2292 Commercial - Fire Protection - HFC-125 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2293 Commercial - Fire Protection - HFC-236fa 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2294 Commercial - Fire Protection - HFC-227ea 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2295 Commercial - Foams - HFC-134a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2296 Commercial - Foams - HFC-245fa 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2297 Commercial - - HFC-125 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2298 Commercial - Refrigeration and Air Conditioning - HFC-134a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2299 Commercial - Refrigeration and Air Conditioning - HFC-143a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2300 Commercial - Refrigeration and Air Conditioning - HFC-236fa 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2301 Commercial - Refrigeration and Air Conditioning - HFC-32 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2302 Commercial - Refrigeration and Air Conditioning - HFC-152a 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2303 Industrial - Aerosols - HFC-134a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2304 Industrial - Aerosols - HFC-152a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2305 Industrial - Fire Protection - CF4 (PFC-14) 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2306 Industrial - Fire Protection - HFC-125 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2307 Industrial - Fire Protection - HFC-236fa 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2308 Industrial - Fire Protection - HFC-227ea 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2309 Industrial - Foams - HFC-134a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2310 Industrial - Foams - HFC-245fa 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2311 Industrial - Refrigeration and Air Conditioning - HFC-125 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2312 Industrial - Refrigeration and Air Conditioning - HFC-134a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2313 Industrial - Refrigeration and Air Conditioning - HFC-143a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2314 Industrial - Refrigeration and Air Conditioning - HFC-236fa 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2315 Industrial - Refrigeration and Air Conditioning - HFC-32 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2316 Industrial - Refrigeration and Air Conditioning - HFC-152a 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2317 Industrial - Solvents - CF4 (PFC-14) 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2318 Industrial - Solvents - HFC-245fa 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2319 Residential - Aerosols - HFC-134a 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2320 Residential - Aerosols - HFC-152a 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2321 Residential - Foams - HFC-134a 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2322 Residential - Foams - HFC-245fa 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2323 Residential - Refrigeration and Air Conditioning - HFC-125 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2324 Residential - Refrigeration and Air Conditioning - HFC-134a 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2325 Residential - Refrigeration and Air Conditioning - HFC-32 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2326 Transportation - Aerosols - HFC-134a 0.24 0.16 0.05 0.02 0.05 0.10 0.26 0.05 0.06
    2329 Transportation - Refrigeration and Air Conditioning - HFC-125 0.24 0.16 0.05 0.02 0.05 0.10 0.26 0.05 0.06
    2330 Transportation - Refrigeration and Air Conditioning - HFC-134a 0.24 0.16 0.05 0.02 0.05 0.10 0.26 0.05 0.06
    2331 Transportation - Refrigeration and Air Conditioning - HFC-143a 0.24 0.16 0.05 0.02 0.05 0.10 0.26 0.05 0.06
    2332 Transportation - Refrigeration and Air Conditioning - HFC-32 0.24 0.16 0.05 0.02 0.05 0.10 0.26 0.05 0.06
    2531 Industrial - Solvents - HFC-365mfc 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2532 Industrial - Solvents - HFC-43-10mee 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2533 Industrial - Solvents - Other PFC and PFE 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2534 Residential - Aerosols - HFC-227ea 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05
    2556 Commercial - Aerosols - HFC-43-10mee 0.20 0.10 0.03 0.02 0.21 0.11 0.27 0.02 0.04
    2557 Industrial - Aerosols - HFC-43-10mee 0.25 0.07 0.02 0.03 0.06 0.08 0.39 0.03 0.06
    2558 Residential - Aerosols - HFC-43-10mee 0.04 0.22 0.14 0.02 0.14 0.10 0.26 0.03 0.05

    BAAQMD Jurisdiction Fraction

    A second apportionment is applied to account for emissions that occur in the portion of Solano and Sonoma counties that are within the Air District’s jurisdiction. The remaining areas in these counties are covered by other Air Districts. The Solano and Sonoma fraction are developed specifically to the sector assigned to each source category, in which the high GWP-gas emissions take place.

    For all Residential categories, ABAG’s population data based on their Plan Bay Area 2050 was used to develop the percentage of Solano and Sonoma County populations within the Air District boundary. (ABAG, 2021). ABAG summarizes population into Travel Analysis Zone (TAZ) such that county totals are estimated by summing the population by TAZ within the Bay Area’s jurisdiction and divided by the total county-wide population to estimate the percentage of population within the SFBA for Solano and Sonoma counties. These proportions are shown below:

    County

    % of Population within the District’s jurisdiction

    Solano

    0.70

    Sonoma

    0.86

    The data source for obtaining the fractional portion of Solano and Sonoma counties for all four sectors is summarized below:

    Subsector

    Air District Jurisdictional Fraction Data Source (Solano and Sonoma Counties)

    Residential

    ABAG Total Households averages for 2015-2020 (ABAG, 2021) – constant, as in the table above

    Commercial

    California Employment Development Department: Service Providing Employment (EDD, 2024) – use Santa Rosa Metropolitan Statistical Areas (MSA)

    Industrial

    California Employment Development Department: Goods Producing Employment (EDD, 2024) – use Vallejo-Fairfield MSA

    Transportation

    California EMFAC2021 model for Vehicle Miles Traveled for each air basin (CARB, 2024)

    Emission Factors, GWP Scaling and Local Controls

    The emissions data are sourced directly from CARB’s statewide GHG inventory which is based on the GWPs from IPCC’s Fourth Assessment Report (AR4; IPCC, 2007). These emissions were subsequently adjusted using GWPs from the more recent IPCC Fifth Assessment Report (AR5; IPCC, 2014). The adjustment was applied by multiplying each pollutant’s emissions by the ratio of its GWPs from 5th report by its AR5 GWP100-year to its AR4 GWP100-year.

    No controls have been added to these emissions as the Air District does not currently regulate emissions from these sources. However, state regulation, including those mandated by California Senate Bill 1206 (SB1206, 2022) requiring the phased reduction of these gases are incorporated in CARB’s forecast from 2022 to 2050.

    Historical Emissions

    Historical emissions for years 1990-1999 are calculated by extrapolating a linear regression using 2000-2004 statewide CARB emissions as the basis. The backcast emissions are set to zero for any years in which the extrapolated line cross the zero axis (simulating the emergence of ozone depleting substance substitutes in the early 1990s).

    Future Projections

    Future projection forecasts are determined using a model in CARB’s 2022 Scoping Plan developed by Energy and Environmental Economics (E3) called California PATHWAYS Non-Energy GHGs Detailed HFCs Business as Usual (BAU) Reference Scenario (CARB, 2022). This modeled growth curve does not include aspirational targets but actual adopted regulations and developed policies that are being implemented. Since CARB’s modeling analysis stops at year 2045, the year 2045 emissions are held constant for 2045-2050 for all source categories.

    Assessment of Methodology

    The general methodology for determining emissions for these categories has not changed from the previous inventories, although all of the data inputs have been updated.

    Year

    Revision

    Reference

    2022

    1. Use years of 2000-2021 from CARB’s Statewide GHG inventory.
    2. Assume 2022 emissions to be the same as those in 2021, from the 2022 Scoping Plan modeling for the High-GWP sector.
    3. Update county proportions using fractions from various sources depending on the sector to which the high GWP source categories are assigned
    4. Backcast is based on linear regression using CARB’s GHG emissions for the years 2000-2004. Any years for which the extrapolated emissions crossed the zero axis are set to zero.
    5. Forecast is based on CARB’s 2022 Scoping Plan Update’s BAU Reference Scenario from E3’s PATHWAYS modeling for Non-Energy GHGs HFCs.
    6. Update Sonoma/Solano County proportions as described in the BAAQMD Jurisdiction Fraction section
    7. No local controls are implemented. Statewide controls are included in the CARB BAU reference scenario
    8. Updated the GWP using IPCC Assessment Report 5
    1. CARB, 2023
    2. CARB, 2022
    3. ABAG, 2021; EDD, 2024; CARB, 2024
    4. Calculation using CARB, 2023 data
    5. CARB, 2022
    6. ABAG, 2021; EDD, 2024; CARB, 2024
    7. SB1206, 2022
    8. IPCC, 2014

    2015

    1. Used CARB’s GHG Statewide inventory to dis-aggregate emissions into the current categories by process, subsector/use, and sector (49 categories)

    2. Used CARB’s GHG inventory for 2000-2017 as base years

    3. Backcast to 1990 using linear regression of emissions from CARB’s GHG Inventory from years 2000-200. Emissions were set to zero for any years that crossed the zero axis.

    4. Forecast using linear regression on GHG data from CARB for years 2014-2017 to extrapolate emissions to 20505.

    5. No controls were implemented either by the Air District or by CARB through legislature.

    6. Updated the GWP using IPCC Assessment Report 5

    1. CARB, 2019
    2. CARB, 2019
    3. Calculation using CARB, 2019 data
    4. Calculation using CARB, 2019 data
    5. Assumption
    6. IPCC, 2014

    2011

    1. The Air District’s high GWP gases inventory included grouping emissions into eight categories (for unique HFCs and PFCs) that did not split emissions across sectors or sub-sector/use.
    2. Used GWP from IPCC Assessment Report 4
    1. BAAQMD, 2015
    2. IPCC, 2007

    Sample Calculations

    An example calculation for San Francisco County for HFC-143c emissions in units of million metric tons of CO2 equivalents (MMTCO2eq) for year 2022 (Category 2330; assigned to Transportation sector) is shown below:

    Step 1

    Obtain 2021 statewide emissions from CARB’s GHG inventory for Category 2330 which is under CARB Sector activity code 99-99-99-25-200 for Transportation 🡪 Refrigeration🡪 HFC-134c pollutant (CARB, 2023)

    3.39 MMTCO2eq

    Step 2

    Estimate the adjustment factor for converting GWP for HFC-143c from AR4 to AR5 (GWP100(AR5)/GWP100(AR4)); GWP100(AR5) = 1300

    GWP100(AR4) = 1430

    = 1300/1430

    = 0.9091

    Step 3

    Apply ratio to adjust the statewide GHG emissions to reflect the latest GWP

    3.39 MMTCO2eq

    × 0.9091

    = 3.08 MMTCO2eq

    Step 4

    Estimate the fraction of VMT/yr for the Bay Area relative to the State for 2022 (CARB, 2024)

    Bay Area VMT = 5.945 × 1010 miles

    California VMT = 3.784 × 1011 miles

    = 5.945 × 1010

    ÷ 3.784 × 1011

    = 0.157

    Step 5

    Estimate the HFC-143c emissions for the Bay Area by multiplying the VMT fraction by the statewide GHG emissions

    = 3.08 MMTCO2eq

    × 0.157

    = 0.484 MMTCO2eq

    Step 6

    Apply growth factor from CARB Scoping Plan E3 forecasts to estimate 2022 emissions based on CARB’s 2021 GHG emissions inventory (CARB, 2022)

    = 0.484 MMTCO2eq

    × 1

    = 0.484 MMTCO2eq

    Step 7

    Estimate the fraction of VMT/yr for San Francisco county relative to the Bay Area for 2022 (CARB, 2024)

    San Francisco County VMT = 3.258 × 109 miles

    = 3.258 × 109

    ÷ 5.945 × 1010

    = 0.0548

    Step 8

    Calculate 2022 HFC-143c emissions for San Francisco by multiplying the Bay Area HFC-143C emissions by fraction of the VMT/yr associated with San Francisco relative to the Bay Area

    = 0.484 MMTCO2eq

    × 0.0548

    = 0.0265 MMTCO2eq

    Emissions

    The table below summarizes greenhouse gas emissions for the base year 2022 in metric tons of CO2 equivalents (MTCO2eq).

    ID Description HFC+PFC Other PFC PFC-14 Total
    2297 Commercial - - HFC-125 873544.1 0.0 0.0 873544.1
    2323 Residential - Refrigeration and Air Conditioning - HFC-125 600569.7 0.0 0.0 600569.7
    2330 Transportation - Refrigeration and Air Conditioning - HFC-134a 483497.7 0.0 0.0 483497.7
    2299 Commercial - Refrigeration and Air Conditioning - HFC-143a 457735.6 0.0 0.0 457735.6
    2298 Commercial - Refrigeration and Air Conditioning - HFC-134a 440566.4 0.0 0.0 440566.4
    2312 Industrial - Refrigeration and Air Conditioning - HFC-134a 223830.9 0.0 0.0 223830.9
    2311 Industrial - Refrigeration and Air Conditioning - HFC-125 132432.4 0.0 0.0 132432.4
    2325 Residential - Refrigeration and Air Conditioning - HFC-32 127914.0 0.0 0.0 127914.0
    2301 Commercial - Refrigeration and Air Conditioning - HFC-32 113628.7 0.0 0.0 113628.7
    2310 Industrial - Foams - HFC-245fa 84526.4 0.0 0.0 84526.4
    2313 Industrial - Refrigeration and Air Conditioning - HFC-143a 82322.5 0.0 0.0 82322.5
    2320 Residential - Aerosols - HFC-152a 45924.2 0.0 0.0 45924.2
    2318 Industrial - Solvents - HFC-245fa 41489.3 0.0 0.0 41489.3
    2331 Transportation - Refrigeration and Air Conditioning - HFC-143a 40623.0 0.0 0.0 40623.0
    2309 Industrial - Foams - HFC-134a 39587.3 0.0 0.0 39587.3
    2319 Residential - Aerosols - HFC-134a 38649.6 0.0 0.0 38649.6
    2329 Transportation - Refrigeration and Air Conditioning - HFC-125 22937.9 0.0 0.0 22937.9
    2324 Residential - Refrigeration and Air Conditioning - HFC-134a 21207.5 0.0 0.0 21207.5
    2322 Residential - Foams - HFC-245fa 18807.3 0.0 0.0 18807.3
    2296 Commercial - Foams - HFC-245fa 17955.5 0.0 0.0 17955.5
    2315 Industrial - Refrigeration and Air Conditioning - HFC-32 14757.5 0.0 0.0 14757.5
    2321 Residential - Foams - HFC-134a 12436.0 0.0 0.0 12436.0
    2300 Commercial - Refrigeration and Air Conditioning - HFC-236fa 8984.6 0.0 0.0 8984.6
    2289 Commercial - Aerosols - HFC-134a 8813.4 0.0 0.0 8813.4
    2326 Transportation - Aerosols - HFC-134a 8605.8 0.0 0.0 8605.8
    2290 Commercial - Aerosols - HFC-152a 8154.7 0.0 0.0 8154.7
    2534 Residential - Aerosols - HFC-227ea 6513.4 0.0 0.0 6513.4
    2295 Commercial - Foams - HFC-134a 5964.9 0.0 0.0 5964.9
    2294 Commercial - Fire Protection - HFC-227ea 5061.3 0.0 0.0 5061.3
    2314 Industrial - Refrigeration and Air Conditioning - HFC-236fa 3109.9 0.0 0.0 3109.9
    2304 Industrial - Aerosols - HFC-152a 2907.7 0.0 0.0 2907.7
    2532 Industrial - Solvents - HFC-43-10mee 1846.9 0.0 0.0 1846.9
    2308 Industrial - Fire Protection - HFC-227ea 1466.2 0.0 0.0 1466.2
    2303 Industrial - Aerosols - HFC-134a 1392.7 0.0 0.0 1392.7
    2533 Industrial - Solvents - Other PFC and PFE 0.0 634.2 0.0 634.2
    2558 Residential - Aerosols - HFC-43-10mee 550.6 0.0 0.0 550.6
    2292 Commercial - Fire Protection - HFC-125 533.4 0.0 0.0 533.4
    2317 Industrial - Solvents - CF4 (PFC-14) 0.0 0.0 452.0 452.0
    2293 Commercial - Fire Protection - HFC-236fa 324.0 0.0 0.0 324.0
    2306 Industrial - Fire Protection - HFC-125 154.6 0.0 0.0 154.6
    2556 Commercial - Aerosols - HFC-43-10mee 97.7 0.0 0.0 97.7
    2307 Industrial - Fire Protection - HFC-236fa 93.9 0.0 0.0 93.9
    2531 Industrial - Solvents - HFC-365mfc 91.4 0.0 0.0 91.4
    2557 Industrial - Aerosols - HFC-43-10mee 34.8 0.0 0.0 34.8
    2332 Transportation - Refrigeration and Air Conditioning - HFC-32 29.2 0.0 0.0 29.2
    2291 Commercial - Fire Protection - CF4 (PFC-14) 0.0 0.0 25.7 25.7
    2305 Industrial - Fire Protection - CF4 (PFC-14) 0.0 0.0 7.5 7.5
    2302 Commercial - Refrigeration and Air Conditioning - HFC-152a 3.8 0.0 0.0 3.8
    2316 Industrial - Refrigeration and Air Conditioning - HFC-152a 2.9 0.0 0.0 2.9

    Summary of Base Year 2022 Emissions

    The high-GWP gases contribute 6.1% of emissions (4.00 MMTCO2eq) to the 2022 base year Bay Area regional GHG emissions inventory (65.341 MMTCO2eq). The table below shows the contributions of high-GWP gases by economic sector. The Commercial sector accounts for the highest emissions – nearly equal to the combined total from the Residential, Industrial, and Transportation sectors.

    Sector

    Emissions (MMTCO2eq)

    Emissions (% of High-GWP Gases)

    Commercial

    1.94

    48.50

    Residential

    0.87

    21.75

    Industrial

    0.63

    15.75

    Transportation

    0.56

    14.00

    The overwhelming majority (91%) of the high-GWP gas emissions originate from refrigeration and air conditioning units. The primary gases responsible are HFC-125, HFC-134a, and HFC-143a, which are predominantly used in refrigeration and air conditioning systems. Additionally, HFC-125 is used to a lesser extent as a fire suppression agent, while HFC-134a also sees minor use in aerosols and foam products. Detailed breakdowns are provided in the tables below:

    Activity

    Emissions (MMTCO2eq)

    Emissions (% of high-GWP gases)

    Refrigeration & Air Conditioning

    3.65

    91.2

    Foams

    0.18

    4.5

    Aerosols

    0.12

    3.0

    Solvents

    0.20

    1.1

    Fire Protection

    0.01

    0.2

    High-GWP species

    Emissions (MMTCO2eq)

    Emissions (% of high-GWP gases)

    HFC-125

    1.63

    40.6

    HFC-134a

    1.25

    32.1

    HFC-143a

    0.58

    14.5

    HFC-32

    0.26

    6.4

    HFC-245f

    0.16

    4.1

    HFC-152

    0.06

    1.4

    HFC-227ea

    0.013

    0.3

    HFC-236fa

    0.013

    0.3

    HFC-43-10mee

    0.003

    0.06

    Other PFC and PFE

    0.0006

    0.02

    CF4

    0.0005

    0.01

    HFC-365mfc

    0.00009

    0.002

    Contribution of High-GWP Gases Emissions by Sector
    Subsector Sector Subsector GHG Emissions (MMTCO2eq) Sector GHG Emissions (MMTCO2eq) % of Sector
    High-GWP Gases Commercial + Residential 2.81 12.85 21.90%
    High-GWP Gases Industrial 0.63 17.90 3.53%
    High-GWP Gases Transportation 0.56 22.60 2.46%

    Contribution of High-GWP Gases Emissions to Regional Total
    Subsector Subsector GHG Emissions (MMTCO2eq) Regional Total GHG Emissions (MMTCO2eq) % of Regional Total
    High-GWP Gases 4.00 65.68 6.09%

    Trends

    The time series chart below shows the emission trends for all high-GWP gases by source category.

    Summary of Trends

    Historical trends of high-GWP gas emissions for the Bay Area show a steady increase from near zero in 1990 to a peak in 2020. Before the Montreal Protocol was signed in 1987, chlorofluorcarbons (CFCs, e.g., R-11, R-12, R-123, R-502) dominated the refrigerant market (Wikipedia, 2025). Following their phase-out, the use of ozone depleting substances alternatives such as high-GWP hydrofluorocarbons increased. The Air District no longer reports CFCs emissions, as they have been largely phased out over the past three decades.

    The future trend shows significant decline in high-GWP gas emissions due to regulatory limits on the use of these compounds as refrigerants, as mandated by SB 1206. Under this legislation, CARB will prohibit the sale of new or virgin bulk HFCs, according to the following schedule:

    • HFCs with GWP > 2,200 prohibited starting January 1, 2025
    • HFCs with GWP > 1,500 prohibited starting January 1, 2030
    • HFCs with GWP > 750 prohibited starting January 1, 2033

    SB 1206 does permit the continued sale and use of reclaimed HFCs (SB 1206, 2022).

    Uncertainties

    The primary sources of uncertainties in this methodology stem from the accuracy of the emissions data collected statewide and assumed leakage rates used in developing CARB’s GHG inventory (CARB, 2022). Detailed discussions regarding the uncertainties for specific high-GWP gases can be found in CARB’s published study (Gallagher et al., 2014). Uncertainty levels for inventory-based emission estimates vary from 15% to 25% for the major high-GWP gases.

    Additional uncertainty is introduced when scaling state-level inventory to produce Bay Area county specific emissions, primarily due to using scaling factors based on surrogate parameters representing each of the four sectors

    CARB updates its GHG inventory annually, incorporating new data and occasionally revising past estimates. Therefore, the base year inventory data may change year to year. In future inventories, the current assumption that 2022 emissions are identical to those in 2021 will be replaced with actual 2022 data when CARB publishes the next inventory update.

    Contact

    Author: Sally Newman

    Reviewer: Abhinav Guha

    Last Update: 08/19/2025

    References

    ABAG. 2021. Plan Bay Area 2050, Association of Bay Area Governments. https://planbayarea.org/finalplan2050

    ACS. 2024. American Community Survey: https://data.census.gov/table

    BAAQMD. 2015. Bay Area Emissions Inventory Summary Report: Greenhouse Gases. Base Year 2011, Bay Area Air Quality Management District. http://www.baaqmd.gov/~/media/Files/Planning%20and%20Research/Emission%20In ventory/BY2011_GHGSummary.ashx?la=en

    CARB. 2019. Greenhouse Gas Inventory 2019 Edition: Years 2000-2017 (AR4 GWPs), California Air Resources Board. https://ww2.arb.ca.gov/ghg-inventory-archive

    CARB. 2022. 2022 Scoping Plan. 2022 Scoping Plan for Achieving Carbon Neutrality, California Air Resources Board. https://ww2.arb.ca.gov/our-work/programs/ab-32-climate-change-scoping-plan/2022-scoping-plan-documents

    CARB. 2023. Greenhouse Gas Inventory 2023 Edition: Years 2000-2021 (AR4 GWPs), California Air Resources Board.

    https://ww2.arb.ca.gov/ghg-inventory-archive

    CARB. 2024. EMFAC2021 model tool, California Air Resources Board. https://arb.ca.gov/emfac/emissions-inventory/6b8231e6a6c91a2d12eb772d3e28c74042588dd5

    EDD. 2024. Industry Employment data search tool, California Employment Development Department. https://labormarketinfo.edd.ca.gov/cgi/dataanalysis/areaselection.asp?tablename=ces

    EDD. 2025. Definition of MSAs, California Employment Development Department. https://labormarketinfo.edd.ca.gov/definitions/metropolitan-areas.html#MSA

    Gallagher, G.; Zhan, T.; Hsu, Y-K.; Gupta, P.; Pederson, J.; Croes, B.; Blake, D. R.; Barletta, B.; Meinardi, S.; Ashford, P.; Vetter, A.; Saba, S.; Slim, R.; Palandre, L.; Clodic, D.; Mathis, P.; Wagner, M.; Forgie, J.; Dwyer, H.; Wolf, K. 2014: High-global Warming Potential F-gas Emissions in California: Comparison of ambient-based versus inventory-based emission estimates, and implications of refined estimates. Environ Sci. Technol. 48, 1084-1093. (See Supporting Information). http://pubs.acs.org/doi/suppl/10.1021/es403447v

    IPCC. 2007. Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Intergovernmental Panel for Climate Change, 106 pp. Available here: https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chapter2-1.pdf

    IPCC. 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II, and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyers (eds.)]. Intergovernmental Panel for Climate Change, Geneva, Switzerland, 151 pp. Available here: https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf

    SB 1206. 2022. Senate Bill No. 1206. Skinner. Hydrofluorocarbon gases: sale or distribution. https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202120220SB1206

    Wikipedia. 2024. Refrigerant. Available here. https://en.wikipedia.org/wiki/Refrigerant#:~:text=Phasing%20out%20of%20CFCs,-See%20also:%20Montreal&text=The%20adoption%20of%20HCFCs%20such,to%20their%20eventual%20phase%2Dout.