3.5 Industrial Manufacturing

    Category ID Description EIC
    21 Sulfur 32036420540000, 32036200100000, 43099520540000
    24 Resins Various
    25 Pharmaceuticals & Cosmetics Various
    26 Other Chemicals Mfg. Various
    34 Metallurgical (incl. Foundry/Forging Op.) Various
    35 Wood Products Mfr. Various
    43 Semiconductor Manufacturing Various
    44 Flexible & Rigid Discs Manufacturing 23023090000000
    45 Fiberglass Products Manufacturing Various
    46 Rubber Products Mfr. Various
    47 Plastic Products Manufacturing Various
    54 Other Industrial Commercial Various

    Introduction

    Greenhouse gas (GHG) emissions from the industrial manufacturing subsector arise from two primary sources:

    1. Fuel combustion, used to generate heat or power machinery and equipment; and
    2. Process-related activities, including chemical reactions and physical transformations that occur during the conversion of raw materials into finished products.

    This chapter focuses exclusively on process-related GHG emissions from permitted manufacturing point sources in the San Francisco Bay Area (SFBA). Emissions from fuel combustion at manufacturing facilities are addressed separately in the Non-Refinery Fuel Combustion chapter, while process emissions from petroleum refineries are discussed in the Petroleum Refining chapter.

    Manufacturing facilities in the SFBA are permitted and tracked as point sources by the Bay Area Air Quality Management District (Air District). They are categorized by the specific types of goods produced and the associated industrial processes (see Appendix at the end of this document). This methodology covers a diverse range of manufacturing activities, including but not limited to:

    • Chemical and material manufacturing, such as:
      • Sulfur production, used in industrial chemicals and fertilizers
      • Resins and plastics manufacturing, including adhesives, coatings, and molding resins
      • Pharmaceutical and cosmetics production, which involve specialized chemical synthesis
    • Metallurgical processes, including foundries and forging operations that rely on high-temperature metalworking
    • Wood products manufacturing, including the fabrication of materials used in construction and furniture
    • Electronics and high-tech manufacturing, including:
      • Semiconductor manufacturing, involving photolithography and etching with fluorinated gases
      • Computer disc production, covering both flexible and rigid media for data storage
    • Other materials manufacturing, including:
      • Fiberglass product manufacturing, common in insulation and construction
      • Rubber and plastic products, widely used across automotive, consumer goods, and packaging sectors
      • Miscellaneous industrial and chemical manufacturing, encompassing a range of support industries for both industrial and consumer markets

    While some permitted semiconductor manufacturing facilities are covered in this chapter, the majority of GHG emissions from the semiconductor sector—particularly those involving perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) are addressed in a dedicated Semiconductor Manufacturing write-up.

    For ease of reference, an Appendix at the end of this chapter provides additional detail on each of the manufacturing categories included in the inventory, including the processes involved and their relevance to GHG emissions.

    Methodology

    Point sources are operations that emit air pollution into the atmosphere at a fixed location within a facility, and for which the Bay Area Air Quality Management District (Air District) has issued a permit to operate (PTO), e.g. roasters, dryers, or ovens. These point sources could also be a collection of similar equipment and/or sources located across multiple facilities, e.g. reciprocating engines.

    During the PTO issuance process, the Air District collects site-specific information from the operating facility and/or determines from published literature, e.g. U.S. Environmental Protection Agency’s (EPA) AP-42 (EPA, 2024), characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. Facilities that hold a PTO are required to renew their permit periodically (this period varies based on facility and source type). Upon renewal, the facilities are requested to provide any updates to source characteristics as well as the source throughput for the past twelve months. This throughput, in combination with the emission factors and controls factors stored in the Air District’s internal database, are used to programmatically estimate annual emissions at the source level. The methodology used to calculate emissions for the base year(s) of a permitted point source is as follows:

    Base Year(s) Emissions source,pollutant =

    Activity Data source × Emission Factorpollutant × Control Factorpollutant × GWP pollutant

    Base Year(s) Emissions county = ∑ Ni=1 Emissionsi

    Where:

    • Base Year: is a year for which activity / throughput data is available from permit records.
    • Activity Datasource is the throughput or activity data for applicable base year(s) at the source/equipment level. This data is usually available from the internal permit records that are provided annually to the Air District at permit renewal by a source / facility operator.
    • Emission Factorpollutant is a factor that allocates an amount of emissions, in mass, of a particular pollutant by unit of activity data. For example, tons CO2 per gallons of gasoline burned or pounds of N2O per million standard cubic feet of natural gas combusted. Criteria pollutants (CAPs) and greenhouse gas (GHG) emissions are calculated by using specific emission factors for every source/operation for which information has been supplied by the facility (and verified/validated through source tests). If no specific emission factors are available, generalized factors developed by Air District staff are used to determine emissions. These default factors typically come from published literature such as USEPA’s AP-42 (USEPA, 2024) or California Air Resource Board’s (CARB) Mandatory Reporting Requirement (CARB, 2019) for Greenhouse Gases.
    • Control Factorpollutant is a fractional ratio (between 0 and 1) that captures the estimated reduction in emissions as a result of District rules and regulations.
    • GWP pollutant is the Global Warming Potential. 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.
    • N is the number of permitted and similar sources in a county.

    If available, a facility can provide emission factors specific to the source that are verified and validated through source tests to estimate GHG emissions. If no specific emission factors are available, general factors developed by Air District staff are used to estimate emissions. These source level emissions are then sorted and aggregated by year, county, and category.

    Further speciation and quality assurance of emissions, including those of GHGs, are performed as a part of the inventory refinement process. A systematic crosswalk was developed between CARB’s California Emissions Projection Analysis Model (CEPAM) source category classification using the primary sector emission inventory codes (EICs) and the Air District’s source category classification (category identification number - cat_ids), which ensures consistency when reporting annual emissions under the California Emissions Inventory Data Analysis and Reporting Systems (CEIDARS) to CARB (CARB, 2022a). This emissions data represents the reported base years emissions for a point source category.

    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.

    For those years where no data is available, emissions data are backcast to year 1990, as well as forecasted to year 2050 using either interpolation or another mathematical approach (see Trends section), or by applying a growth profile based on socioeconomic indicators. GHG emissions data from the years 1990 to 2050, including the projections outlined below, are analyzed for each source category and pollutant, with the trends evaluated for any observed anomalies and modified, if needed:

    • Historical Backcast (1990 – 2006): Association of Bay Area Governments (ABAG) Employment growth profiles (ABAG, 2024) and scaled District permitted data
    • Base Years (2007 – 2022): District permitted data
    • Future Projection (2023 – 2050) : CARB 2022 Scoping Plan projection profiles (CARB, 2022b)

    The emissions estimation methodology for this sub-sector has not changed since the base year 2015 GHG emissions inventory, but updates to the 2022 base year inventory have improved the representativeness of the GHG emissions data.

    Local Controls

    A review of applicable BAAQMD rules was conducted to assess the potential impact of criteria air pollutant (CAP) control rules on GHG emissions from these sources. The following rules were reviewed:

    • Regulation 8, Rule 2 – Miscellaneous Operations (BAAQMD, 2022)
    • Regulation 8, Rule 24 – Pharmaceutical and Cosmetic Manufacturing (BAAQMD, 1994)
    • Regulation 8, Rule 30 – Semiconductor Manufacturing (BAAQMD, 1998)
    • Regulation 8, Rule 36 – Resin Manufacturing (BAAQMD, 1984)
    • Regulation 8, Rule 38 – Flexible and Rigid Disk Manufacturing (BAAQMD, 1995)
    • Regulation 8, Rule 50 – Polyester Resin Operations (BAAQMD, 2009)
    • Regulation 8, Rule 52 – Coating Operations for Rubber and Plastic Products (BAAQMD, 1999)

    These rules are primarily designed to reduce precursor organic compound (POC) or volatile organic compound (VOC) emissions that contribute to ozone formation and are regulated under state and federal clean air programs. They typically require capture and control technologies or impose operational limits on VOC-emitting equipment and materials.

    These rules do not significantly impact GHG emissions, since most of the VOCs targeted by these regulations are not potent greenhouse gases. Any incidental reductions in GHGs that may occur through improved combustion or solvent substitution are either already reflected in the throughput and emission factor methodology used for permitted source calculations, or accounted for in separate GHG categories, such as the High Global Warming Potential (high-GWP) Gases or Semiconductor Manufacturing subsectors.

    As a result, no additional GHG-specific control factors need to be applied to the emissions estimates for the manufacturing categories addressed in this chapter. A summary of all relevant BAAQMD rules is provided in the appendix to this chapter.

    Historical Emissions

    Historical emissions for point sources are derived from source-specific data provided by the facility on throughputs, compiled or reported emission factors, and regulation-based control factors. This information is archived in the Air District’s internal database and is queried to retrieve the data for historical and current years. Interpolation techniques to account for missing data are used when necessary.

    In the case of GHGs, up until the year 2006, the Air District was not engaged in systematic information collection during permit renewal process. This changed when AB32 bill was passed into a statewide law in 2006, and a statewide Cap and Trade system was introduced to reduce GHG emissions from specific facilities. Hence, GHG emissions data for years 1990-2006 are derived from the historical emissions data reported in the base year 2011 GHG inventory (released in year 2012). The historic emissions dataset is scaled to sync with the data in the permit database (which started systematic GHG data accounting from year 2006 onwards), to generate a complete GHG emissions time series for each point source category from 1990 to 2050.

    Future Projections / Growth

    Forecasting of point source emissions is done based on calculations as shown in the equation below using recently updated growth profiles and a base year of 2022. The growth profiles for the current base year inventory have been verified and updated to represent the most likely surrogate for forecasting emissions for a given category up to the year 2050. Forecasting for point source emissions includes impact of in-place regulations but does not include estimation of controls that will theoretically be implemented as part of future policy emission targets or proposed regulation and legislation.

    PE = Gr × Ci × Ei

    PE = projected emissions of pollutant i in a future year

    Gr = growth rate by economic profile of industry or population

    Ci = control factor of pollutant i based on adopted rules and regulations
    Ei = base year emissions of pollutant i

    The projections for the Manufacturing point source categories are based on the California Air Resources Board (CARB) 2022 Scoping Plan's "Non-Energy Other: Industrial Fuel" growth profile (CARB, 2022b), which forecasts emissions trends by considering factors like economic growth and technological advancements in emissions reduction.

    Emissions

    The detailed breakdown of 2022 ‘Industrial Manufacturing’ subsector GHG emissions in units of metric tons of CO2 equivalents (MTCO2eq) are provided in the table below.

    ID Description CH2Cl2 CH4 CO2 CO2_bio HCFC-22 N2O SO2F2 Total
    26 Other Chemicals Mfg. 0.9 7.4 233232.7 0.0 0.0 6.5 691.8 233939.3
    54 Other Industrial Commercial 1.0 2446.9 2.2 789.0 27.9 296.6 0.0 3563.6
    47 Plastic Products Manufacturing 0.0 0.0 4.1 0.0 0.0 0.0 0.0 4.1

    Summary of Base Year 2022 Emissions

    The relative contribution of Manufacturing GHG emissions to region-wide and sector-level GHG emissions totals are highlighted in the table below. This underscores the relatively minor impact of manufacturing-related emissions compared to larger sources such as passenger cars and natural gas combustion.

    Contribution of Industrial Manufacturing Emissions by Sector
    Subsector Sector Subsector GHG Emissions (MMTCO2eq) Sector GHG Emissions (MMTCO2eq) % of Sector
    Industrial Manufacturing Industrial 0.24 17.90 1.32%

    Contribution of Industrial Manufacturing Emissions to Regional Total
    Subsector Subsector GHG Emissions (MMTCO2eq) Regional Total GHG Emissions (MMTCO2eq) % of Regional Total
    Industrial Manufacturing 0.24 65.68 0.36%

    Trends

    The time series chart below shows the emission trends for all point source categories in the Manufacturing subsector.

    Summary of Trends

    Emissions trends in the manufacturing subsector are informed by a combination of historical emissions reported by permitted facilities and regional population and agricultural employment projections provided by ABAG. These indicators are used to assess both past and future activity levels and their influence on GHG emissions.

    Activity levels and throughput within each manufacturing source category are expected to rise in response to growing product demand. However, despite this projected growth, significant increases in GHG emissions are not anticipated. According to the CARB 2022 Scoping Plan's (1) "Non-Energy Other: Industrial Fuel" growth profile (CARB, 2022b), the manufacturing sub-sector is expected to experience minimal or no growth in emissions, with levels remaining largely constant. This projection reflects the assumption that factors such as economic growth and technological advancements in emissions reduction will stabilize emissions in the sector. Despite potential fluctuations in industrial activity, ongoing improvements in efficiency, emission controls, and the transition to cleaner technologies are expected to counterbalance the impacts of increased production, resulting in little to no overall growth in emissions from the manufacturing sub-sector.

    Uncertainties

    GHG emissions estimates for point source categories rely on permitted emission calculations for individual sources, which typically use specific throughputs, emission factors, and control measures. While generally reliable, these calculations vary due to changes in data inputs, regulatory controls, or operational conditions, introducing variability and uncertainty into the emission estimates.

    As noted above, point source emissions are calculated at an individual source level. The accuracy of these calculations is limited by the accuracy of the specific emission factors applied and estimated throughput. As these emissions are aggregated to create category level summaries, it is difficult to define a quantitative error associated with the total.

    Contact

    Author: Michael Nguyen

    Reviewer: Abhinav Guha

    Last Update: 08/19/2025

    References

    ABAG. 2024. Association of Bay Area Governments. Historical Growth Profiles from Archived Internal Database. Accessed October 3, 2022.

    BAAQMD. 1995. BAAQMD Regulation 8 Rule 38 - Flexible and Rigid Disc. Available: Manufacturing, https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-38-flexible-and-rigid-disc-manufacturing/documents/rg0838.pdf?la=en&rev=a9a079aa9ba448bfae8265ac28ca9dff. Accessed October 3, 2022.

    BAAQMD. 1999. Regulation 8 Rule 52 - Polystyrene, Polypropylene and Polyethylene Foam Product Manufacturing Operations. Available: https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-52-polystyrene-polypropylene-and-polyethylene-foam-product-manufacturing-operations-adopt/documents/rg0852.pdf?la=en&rev=24382013a8c9405a94c7027907f43fb4. Accessed October 3, 2022.

    BAAQMD. 1984. Reg 8-36, Resins. Available: https://www.baaqmd.gov/rules-and-compliance/rules/reg-8-rule-36-resin-manufacturing. Accessed October 3, 2022.

    BAAQMD. 1990. District Regulation 8 Rule 24, Pharmaceuticals and Cosmetics. Available: https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-24-pharmaceutical-and-cosmetic-manufacturing-operations/documents/rg0824.pdf?rev=ffaac4364ffd48088b1defc2daa4bf9b&sc_lang=en. Accessed October 3, 2022.

    BAAQMD. 1998. Regulation 8 Rule 30 - Semiconductor Wafer Fabrication Operations. Available: https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-30-semiconductor-wafer-fabrication-operations/documents/rg0830.pdf?la=en&rev=6399035c055b4951b147495054fb5057. Accessed October 3, 2022.

    BAAQMD. 2005. Regulation 8 Rule 2 – Miscellaneous Operations (Other Chemical Manufacturing). Available: https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-2-miscellaneous-operations/documents/rg0802.pdf?la=en. Accessed October 3, 2022.

    BAAQMD. 2009. Regulation 8 Rule 50 - Polyester Resin Operations. Available:  https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-50-polyester-resin-operations/documents/rg0850.pdf?la=en&rev=ea70610abffe492baabcc431e82d71c6. Accessed October 3, 2022.

    CARB. 2019. California Air Resources Board - Regulation for the Mandatory Reporting of Greenhouse Gas Emissions. https://ww2.arb.ca.gov/sites/default/files/classic/cc/reporting/ghg-rep/regulation/mrr-2018-unofficial-2019-4-3.pdf

    CARB. 2022a. Emission Inventory Documentation. Available: https://ww2.arb.ca.gov/emission-inventory-documentation. Accessed October 3, 2022. Accessed October 3, 2022.

    CARB. 2022b. CARB 2022 Scoping Plan. Available: https://ww2.arb.ca.gov/our-work/programs/ab-32-climate-change-scoping-plan/2022-scoping-plan-documents. Accessed October 3, 2022.

    USEPA. 2024. AP-42: Compilation of Air Emissions Factors from Stationary Sources, United States Environmental Protection Agency. Available: https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors-stationary-sources. Accessed November, 2024.

    IPCC, 2014. Intergovernmental Panel on Climate Change (IPCC) Global Warming Potential AR5. https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf