3.4 All Other Chemical Plants

Categories 21, 22, 26, and 27

3.4.1 Introduction

Emissions reported in this category are from the operations at other chemical manufacturing facilities. The emissions consist of both point (Categories 21, 22, and 26) and area (Category 27) source emissions.

Category 21 consists of emissions from sulfur recovery and sulfur storage units at refineries and chemical plants. The emissions reflected herein include all five criteria pollutants (PM, VOC, NOx, SOx, CO) with SOx being the largest emitting pollutant.

Category 22 consists of emissions from sulfuric acid storage tanks at refineries and chemical plants. The primary criteria pollutant emission from these two categories is sulfur dioxide. Abatement devices to treat tail gas at sulfur recovery units and sulfur dioxide scrubbers at sulfuric acid manufacturing plants have significantly reduced the amount of sulfur dioxide emitted.

Category 26 contains all other chemical plant point source process emissions. Sources of emissions include those from acid manufacturing plants, kiln burners, and specialty chemicals manufacturing plants. Emissions caused by the combustion of fuels at chemical plants are not accounted in this category and are accounted in other categories.

Category 27 contains fugitive emissions at chemical plants. Components such as valves, flanges, pumps, compressors, and pressure relief valves (PRVs) are potential sources of emissions due to leaks from seal failures. These emissions generally occur randomly and are difficult to predict. In addition, these emissions may be intermittent and vary in intensity over time. According to EPA report ¹⁷, 35% of the total emissions at the chemical manufacturing facilities are emitted as fugitive emissions.

3.4.2 Methodology

Point Sources

Point Sources are operations that emit air pollution into the atmosphere at a fixed location within a facility, for which the Air District has issued a permit to operate, e.g. refinery cooling towers. These could also be a collection of similar equipment / sources located across multiple facilities, e.g. reciprocating engines.

During the permit to operate (PTO) issuance process, the BAAQMD collects information from the operating facility and/or determines from published literature, e.g. EPA’s AP-42, characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. These characteristics are then stored for future use in the BAAQMD’s internal database. Facilities that hold a permit to operate are required to renew this 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 last 12 months. This throughput, in combination with the emission factors and controls factors stored in the internal database, are used to estimate annual emissions at the source level. These source level emissions are then sorted and aggregated into categories.

Further speciation and quality assurance of emissions are performed as a part of the inventory process. The BAAQMD staff also perform a systematic crosswalk between CEPAM’s source category classification (Emission Inventory Code - EICs) and the District’s source category classification (category identification number - cat_ids), which ensures consistency in the annual emissions reporting process (CEIDARS) to California Air Resources Board. The last part of the inventory development process includes forecasting and back casting, and aggregation into sub-sectors and sectors for documentation purposes. For those years where no data is available, emissions data are backcasted to year-1990, as well as forecasted to year-2040 using either interpolation or another mathematical approach (see Trends section). Finally, emissions trends spanning from year 1990-2040 for each category and pollutant are evaluated for anomalies that are then investigated and addressed.

Categories 21, 22 and 26 are considered point source categories and follow the above methodology for emissions estimates. To limit and reduce emissions from these categories, District’s Regulation 9, Rule 1, Sulfur Dioxide (SOx) Rule ¹⁸ is in place and this limits SOx emissions including those from manufacturing plants.

For category 27, which is considered an area source category, District Regulation 8, Rule 22, Valves and Flanges at Chemical Plants¹⁹, is in place. This Rule limits emissions of precursor organic compounds from valves and flanges at chemical plants.

Area Sources

Unlike categories 21, 22, and 26 (point sources) in which emissions are accounted for directly through District’s permitting processes, category 27 (area source) emission totals are estimated indirectly from the same permitting dataset. Fugitive emissions for this area source category is estimated as 35% of the total organic emissions at the chemical manufacturing facilities (Categories 21 through 26) within the District. The number of equipment components is used as throughput.

(a) Activity Data / Throughput

The number of equipment components is used as the throughput. For point sources categories 21, 22, and 26, throughputs are obtained from District’s database system. The District updates the data each year on a source-by-source basis using process material throughputs, reported annually by the chemical manufacturing companies, as inputs for calculating emissions.

(b) County Distribution / Fractions

The ratio of each county’s population is used to distribute emission into counties. For area source categories, the derive county fractions are based on data available from a handful of resources. These resources include employment- and population-based growth projections generated by the Association of Bay Area Governments²⁰, fixed-percentage growth assumptions consistent with historical emissions data trends, and specific growth profiles derived using relevant regional or sub-national data sources (e.g. county-specific wine production data from the Wine Institute for wine fermentation categories, California crude oil distillation capacity data from the Energy Information Administration for refinery categories, and California Energy Commission natural gas usage projection data for residential and commercial natural gas combustion categories).

(c) Emission Factors

Point source emission factors for category 21, 22, and 26 include source specific factors reported by the companies through source test results or applicable general factors, i.e. from the EPA. Fugitive emissions for Category 27, comprising mostly of TOG emissions, are estimated using the throughputs of District’s point source chemical manufacturing facilities (Categories 21 through 26).

(d) Control Factors

The District adopted [Reg 8-22]³ on March 5, 1980. The control afforded by this rule is estimated to be 60%, with rule effectiveness at 98% for an overall control rate of 59%. This rule only affects fugitive emissions at chemical manufacturing facilities.

[Rule 9-1]² also controls non-organic emissions from many of the manufacturing plants in these categories. The District amended this rule in 1983, 1992, and 1995 for sulfur dioxide limits at sulfur recovery systems and sulfuric acid plants. The rule also further sets limits on hydrogen sulfide, nitrogen oxides, and carbon monoxide emissions.

(e) Speciation

Some pollutants included in the current base year Emissions Inventory can be further subdivided into sub-components. Particulate matter (PM) can be represented as fractions of Total Suspended Particulates (TSP), PM10, PM2.5, Black Carbon (BC) and Organic Carbon (OC). Volatile Organic Compounds (VOCs) can be represented as Total Organic Gases (TOG), Reactive Organic Gases (ROG), and CH4 or Non-Reactive VOC component. The fractions of each of these sub-components should be listed and the source from which the relative apportionment has been derived included in the citations. It is possible that a bulk of these profiles are obtained from CARB speciation profiles. For these categories included herein, the TOG to ROG fraction is equal to a value of 1 since all organic emissions in this category are considered reactive.

3.4.3 Changes in Methodology

There are no changes in the methodology to estimate emissions in the current base year inventory compared to the previous base year inventory (year 2011).

3.4.4 Emissions

A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.

3.4.5 Trends

In general, emissions increase as throughputs increase. In addition to usage changes, new installations also increase the emissions. Overall emissions for these categories did not significantly increase in last eight years.

(a) Historical Emissions / History

Historical emissions for point source emissions (category 21, 22, and 26) are derived from source-specific throughputs provided by the permitted facility, compiled/reported emission factors, and regulation-based control factors. This information is archived in the BAAQMD’s internal database which is queried to retrieve the data for historical and current years. Interpolation techniques to account for missing data are used when necessary, this is the case for years 1991-1992.

Historical emission from area source emissions (category 27) are estimated using emissions from District’s point source chemical manufacturing facilities (Categories 21 through 26) and adjusted per EPA guidance¹ of 35% of the total emissions from District’s chemical manufacturing facilities. As previously mentioned, historical emission has significantly decreased since the adoption of District Regulation 8, Rule 22 ³, which limits organic compound emissions from pharmaceutical and cosmetic manufacturing operations.

(b) Future Projections / Growth

For a given category or a group of related categories, future emissions estimates were developed using a growth profile based on data available from a handful of resources. These resources include employment- and population-based growth projections generated by the Association of Bay Area Governments²¹, fixed-percentage growth assumptions consistent with historical emissions data trends, and specific growth profiles derived using relevant regional or sub-national data sources (e.g. county-specific wine production data from the Wine Institute for wine fermentation categories, California crude oil distillation capacity data from the Energy Information Administration for refinery categories, and California Energy Commission natural gas usage projection data for residential and commercial natural gas combustion categories).

\[ \text{PE} = \text{Gr} * \text{Ci} * \text{Ei} \] \(PE\) = projected emissions of pollutant i in a past or 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

Emissions for these four source category through the year 2040 are projected to follow various manufacturing profiles which forecast growth to be gradually decreasing over time.

3.4.6 Uncertainties

Throughputs for this category are reported via permit system requirement on a year by year basis and are assumed to reflect the most current data available at the time. Throughput data that are taken based on source test is considered the most accurate, followed by engineering calculations such as mass/material balance, and then published data via literature such as AP-42. The emission factor is estimated using historical data and could change or be improved as new data is published.

3.4.7 Contact

Author: Tan Dinh

Reviewer: Abhinav Guha, Yuan Du

Last Update: November 06, 2023

3.4.8 References & Footnotes