8.4 Food Processing

    Category ID Description EIC
    31 Wineries - Fermentation 19999560000000
    32 Wineries - Aging 42041060900000
    33 Other Food & Agricultural Processes Various
    1904 Wineries - Fermentation (Area) 42040860900000

    Introduction

    This document outlines the methodology used to estimate greenhouse gas (GHG) emissions from permitted food processing and baking operations in the San Francisco Bay Area (SFBA). These sources include a variety of combustion-related and biological processes that generate carbon dioxide (CO₂), biogenic carbon dioxide (CO₂_bio), methane (CH₄), and nitrous oxide (N₂O).

    GHG emissions are organized into specific categories based on the type of materials processed and the nature of the activity:

    • Food Processing (Category 33 – Other Food and Agricultural Processing):
      This category includes GHG emissions from permitted facilities engaged in the processing of various food and agricultural products for human or animal consumption. Activities within this category include coffee and cocoa bean roasting, grain feed milling and packaging, spice and flavoring handling, sugar refining, and the processing of onions, garlic, corn, and pet food. GHG emissions from these operations are generated through a mix of combustion and process-related sources:
      • CO₂ emissions primarily result from the on-site combustion of natural gas or other fuels used to power roasters, dryers, and ovens. These combustion processes are essential for drying and flavor development in coffee, cocoa, grains, and spices.
      • CH₄ emissions may arise from incomplete combustion in burners or from anaerobic decomposition of organic byproducts (e.g., food waste) in cases where on-site material handling systems are present.
      • N₂O can be produced during high-temperature combustion processes, especially from natural gas-fired equipment such as roasters and industrial dryers, due to the reaction of nitrogen and oxygen in the combustion air.
    • Bakeries (Category 28 – Large Bakeries):
      Accounts for CO₂ emissions from the combustion of ethanol in afterburners used by large commercial bread bakeries. Ethanol is produced biologically during the fermentation of dough and is captured and incinerated as part of standard emissions control. Facilities in this category typically produce more than 100,000 pounds of bread, buns, or rolls per day and are classified as point sources.

    Consistent with California Air Resources Board (CARB) guidance (CARB, 2016), CO₂ emissions from bakery fermentation are considered biogenic and are excluded from the regional anthropogenic CO₂ inventory. Several additional food processing and baking categories are not included in this methodology because they either emit only biogenic CO₂ or are considered de minimis contributors to the regional GHG inventory. These excluded categories include:

    • Small Bakeries (Category 935)
    • Winery Fermentation Area Sources (Category 1904)
    • Wineries/Breweries – Aging (Category 32)

    Descriptions of these excluded categories and the rationale for their exclusion are provided in the Appendix.

    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 (BAAQMD or the Air District) has issued a permit to operate (PTO), e.g. refinery cooling towers. 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. United States Environmental Protection Agency’s (USEPA) AP-42 (USEPA, 2024), characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. This data is then compared against the Air District’s Regulations to ensure compliance. 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 point source category is summarized below:

    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 Data source 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 the 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. 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 has been 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, 2022). 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 and corrected for any observed anomalies and addressed accordingly:

    • Historical Backcast (1990-2006): Extrapolated to 1990 using linear regression based on historical throughput trends from internal database
    • Base Years (2007-2022): District permitted data
    • Future Projection (2023-2050): Association of Bay Area Governments (ABAG) Plan Bay Area 2050 projections (ABAG, 2024)
      • Population growth (county-level) for category 28
      • Agricultural and Natural Resources job growth (county-level) for category 33

    Local Controls

    This methodology accounts for applicable regulatory controls that influence GHG emissions from permitted sources. For large commercial bakeries, the key rule governing emissions is Regulation 8, Rule 42 (BAAQMD, 1994), which addresses volatile organic compound (VOC) emissions from bread ovens.

    Effective as of January 1989, this rule establishes emission control requirements for new and modified bakery ovens at large commercial bread bakeries—specifically those producing more than 100,000 pounds of bread products per day. The rule requires the installation of capture and control systems designed to reduce VOC emissions, which include ethanol generated during the bread fermentation process.

    Under this regulation, bakery ovens must be equipped with:

    • A collection system to capture ethanol emissions from the proofing and baking phases, and
    • An abatement device, such as an afterburner, capable of achieving a minimum 90% destruction efficiency of POC emissions on a mass basis.

    The destruction of ethanol in these afterburners converts it into CO₂ through combustion. As a result, 90% of ethanol emissions that would otherwise be classified as VOC are instead reported as CO₂ emissions, assuming a 90% destruction efficiency of ethanol. Since ethanol is a biogenic compound (produced via fermentation of organic matter), its combustion results in the release of CO₂_bio.

    This regulatory control mechanism directly affects GHG emissions from large bakeries by reducing VOC emissions to the atmosphere and increasing reported biogenic CO₂ emissions due to the required incineration of captured ethanol. In keeping with CARB GHG inventory protocols, these biogenic CO₂ emissions are excluded from the anthropogenic CO₂ totals reported in the regional GHG inventory, but are still quantified and tracked for transparency.

    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

    As mentioned previously, future emissions from permitted food processing and baking facilities are projected through 2050 using growth forecasts developed by the ABAG as part of the Plan Bay Area 2050 regional planning effort (ABAG, 2024). These projections include:

    • County-level population growth, which is used as the growth driver for emissions from Category 28 – Large Bakeries, based on the assumption that demand for commercially baked goods scales with population.
    • County-level job growth in the Agricultural and Natural Resources sector, which is used as the growth driver for Category 33 – Other Food and Agricultural Processing, reflecting the anticipated expansion of employment—and by proxy, production activity—in food and agricultural manufacturing.

    Emissions

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

    ID Description Total

    Summary of Base Year 2022 Emissions

    The relative contribution of GHG emissions from food processing and bakeries to region-wide and sector-level GHG emissions totals are highlighted in the table below. Food processing GHG emissions are shown relative to the Agricultural sector, while large bakery GHG emissions are shown relative to the Commercial + Residential sector. GHG emissions from permitted food processing and baking facilities in the SFBA were relatively minor when compared to overall sector emissions. Emissions vary by category based on the specific processes and materials involved:

    • Other Food and Agricultural Processing (Category 33):
      Emissions from this category consist predominantly of CO₂ produced through fuel combustion in equipment such as roasters, dryers, and boilers. These emissions are relatively low in volume compared to other industrial or agricultural sources.
    • Large Bakeries (Category 28):
      The only GHG emitted from this category is CO₂ resulting from the combustion of ethanol captured and destroyed in afterburners as required by Regulation 8, Rule 42. Since the ethanol is generated through yeast fermentation, the resulting CO₂ is biogenic (CO₂_bio) and excluded from anthropogenic totals in accordance with CARB GHG inventory practices.
    Contribution of Food Processing Emissions by Sector
    Subsector Sector Subsector GHG Emissions (MMTCO2eq) Sector GHG Emissions (MMTCO2eq) % of Sector
    Food Processing Agriculture 0.000 1.26 0.003%

    Contribution of Food Processing Emissions to Regional Total
    Subsector Subsector GHG Emissions (MMTCO2eq) Regional Total GHG Emissions (MMTCO2eq) % of Regional Total
    Food Processing 0.000 65.68 0.000%

    Trends

    The time series chart below shows the emission trends for other food and agricultural processing (category 33) and large bakeries (category 28).

    Summary of Trends

    Emissions trends in the food processing 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.

    In general, emissions in this subsector tend to increase in proportion to production throughput, as higher volumes of food and beverage processing typically result in greater fuel use and associated emissions. However, this growth in emissions is often offset by improvements in process efficiency, equipment upgrades, and the adoption of emission control technologies.

    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: Tan Dinh

    Reviewer: Abhinav Guha

    Last Update: 08/29/2025

    References

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

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

    BAAQMD. 1994. Rule Development, Rule 8-42, Bay Area Air Quality Management District.  https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-42-large-commercial-bread-bakeries/documents/rg0842.pdf?rev=dc6d019ab886429890c67e949953879a&sc_lang=en

    CARB. 2016. California’s 2000-2014 GHG Inventory - Technical Support Document, California Air Resources Board. https://ww2.arb.ca.gov/sites/default/files/classic/cc/inventory/ghg_inventory_tsd_00-14.pdf

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

    CARB. 2022. Emission Inventory Documentation, California Air Resources Board. https://ww2.arb.ca.gov/emission-inventory-documentation. Accessed October 3, 2022. Accessed October 3, 2022.

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

    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