6.2 Refinery and Marine Loading Operations
Categories 60, 86-91, 795-802
6.2.1 Introduction
Categories 60, 86-87, 91, and 795-802 account for fugitive organic emissions from refinery and marine loading operations.
There are many categories that make up this chapter to account for these type of emissions. They include both point and area sources as displayed below.
| Category # | Description | Classification |
|---|---|---|
| 60 | Other Marine Loading | Point |
| 86 | Lightering Ships | Area |
| 87 | Lightering Barges | Area |
| 88 | Ballasting Crude Oil | Area |
| 89 | Ballasting Gasoline | Area |
| 90 | Ballasting Other Materials | Area |
| 91 | Marine Vessel Cleaning | Area |
| 795 | Tanker Loading Cruel Oil (refinery) | Point |
| 796 | Tanker Loading Gasoline (refinery) | Point |
| 797 | Barge Loading Cruel Oil (refinery) | Point |
| 798 | Barge Loading Gasoline (refinery) | Point |
| 799 | Tanker Loading Cruel Oil (non-refinery) | Point |
| 800 | Tanker Loading Gasoline (non-refinery) | Point |
| 801 | Barge Loading Cruel Oil (non-refinery) | Point |
| 802 | Barge Loading Gasoline (non-refinery) | Point |
Category 60 includes all refinery loading operations other than tanker and barge loading. This category accounts for emissions mostly from loading racks and railroad/truck tank car loading.
The following categories include evaporation emissions due to handling of all organic products at marine loading facilities.
Categories 86 and 87 account for evaporation emissions due to the transfer of cargo (organic materials) from larger ships to smaller ships and barges. Lightering is necessary because large ships are unable to navigate the shallow waters of the San Francisco Bay. Since the mid-2000’s, there has been little or no lightering activity in the San Francisco Bay due to regulatory restrictions and the transition or increase usage of other crude oil delivery methods such as pipeline and railcars.
Categories 88-90 account for evaporation emissions due to ballasting crude oil, gasoline, and other materials, respectively. Ballasting is the process of pumping seawater into petroleum holding tanks to make a vessel more stable. When water is pumped into a tank, the contaminated vapor in the tank is displaced into the atmosphere. Emissions from ballasting have been declining because few vessels now calling on Bay Area ports ballast into cargo tanks. Older vessels are being phased out of service in response to the Oil Pollution Act of 1990. Modern vessels have segregated ballast tanks that are used only for ballast water. There are no organic emissions emitted during ballast operations with segregated ballast tanks.
Category 91 accounts for emissions from gas venting. When a tank vessel unloads its product, organic vapors are left in the compartments. Frequently, vessels vent these vapors to the atmosphere for safety reasons.
Categories 795-798 account for all evaporative emissions from loading/unloading of gasoline, crude oil and other organic products from marine vessels at the oil refineries.
Categories 799-802 account for evaporative emissions from loading/unloading of gasoline and crude oil from all non-refinery operations.
The organic emissions from these categories are reported as volatile organic compound (VOC) emissions and are considered all reactive organic gases (ROG) part of total organic gases (TOG).
6.2.2 Methodologies
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 60 and 795-802 are considered point source categories and follow the above methods for emissions estimates. To limit and reduce organic compound emissions from these categories, District’s Regulation 8, Rule 44, Marine Tank Vessel Operations Rule 161 regulates organic compound emissions into the atmosphere from marine loading operations in the Bay Area. The regulation was adopted on January 1989.
For this group of point source categories, ROG constitutes 100% of TOG. For base year 2015, the magnitude of the ROG emissions amounts to approximately 93 tons/year. The bulk of the emissions is derived from Cat 800 (tanker loading - gasoline) which comprised of approximately 88% of these group of point sources ROG emissions. Historical emission trend for these group of point sources has been declining over the years mostly as a result of the above District’s rule. It is expected that the future emission trend for refinery related storage tanks to follow data extrapolated from California Annual Operable Atmospheric Crude Oil Distillation Capacity reduction from 2010 to 2020, i.e., it’s assumed a 0.67% decrease annually from 2021 to 2040. The data used in the extrapolation is taken from US Energy Information Administration website162.
Area Sources
Categories 86 through 91 are considered an area source category since they cover facilities / emission sources that are not directly permitted by the District, and hence not systematically cataloged. Emissions for area source categories are determined using the formula:
Current Year Emissions = Base Year Emission X Growth Profile, and,
Base Year Emission = Throughput X Control Factor X Emission Factor
where,
- throughput or activity data for applicable base year(s) is determined using a top-down approach (e.g. state-, national-level data);
- emission factor is derived from general literature, specific literature and reports, and/or source testing results provided by Air District staff;
- control factor (if applicable) is determined by District and state rules and regulations in effect;
- and, historical backcasting and forecasting of emissions is based on growth profiles as outlined in the Trends section of this chapter
More details on throughput, county distribution, emission factors and controls is provided in the following subsections. Emissions from marine loading operations used in non-permitted industries are usually estimated at the unit of a geographical area, e.g., county. These area source emissions could be derived based on data obtained from point sources through District’s point source database system.
(a) Activity Data / Throughput
Point source emissions are obtained from the District’s internal permit database. The database contains information submitted by the individual refinery regarding point sources.
Area Source emissions are derived or estimated based on data from various sources. For Categories 86 and 87, the refineries data within the District were gathered via permitting process to obtain the throughputs (in 1000 gallons) transferred for a given year. The monthly variations and county distributions were also obtained from these permits. For Categories 88-90, the amount of material transferred was estimated from data found in the U.S. Army Corps of Engineers’ (USACE) 2008 Waterborne Commerce of the United States, Part 4–Waterways and Harbors-Pacific Coast, Alaska and Hawaii. 163.
For Category 91, the following assumptions were made to derive throughput data:
- The average tanker delivering crude oil to the Bay Area has a deadweight tonnage of 120,000 tons. This represents a tanker volume of approximately 32.4 million gallons, assuming a density of 7.4 lbs./gal.
- In 2008, it was estimated a total of 6,867,568 million gallons of crude was unloaded in Bay Area ports. Assuming the above tanker volume, this represents approximately 212 tanker visits.
- Purging is not done that often at Bay Area ports. In the report, Oil Tanker Purging & Gas Freeing (December 1999), it was estimated purging occurred in connection with 35 – 50 arrivals per year. In 2004, it was estimated there were 12 venting operations per year. Since 2004, most ship operators perform their venting operations outside the District boundaries.
(b) County Distribution / Fractions
For the point source categories, the county location of each company, as reported in the Data Bank, is used to distribute emissions into each county. For the area source categories, the county distribution was based on the throughputs of products unloaded at the various Bay Area ports, as reported in the U.S. Army Corps of Engineers2.
(c) Emission Factors
Emission factors for point sources are collected and used as referenced in the Methodology section of this chapter. Area source emission factors are collected through different resources. For Categories 86 and 87, emission factors were obtained from ARB’s Emission Inventory Procedural Manual which is not published online but might be available by request via CARB. Since 2005, there has been no lightering activity in the San Francisco Bay. For Categories 88-90, emission factors, ballasting amounts for the different fuels, etc. were obtained from California Air Resources Board’s Methodology Document on Marine Petroleum Unloading (October 1997) which is also not published online but might be available by request via CARB. For Category 91, the emission factor used in purging applications is the same one developed for ballasting operations for crude oil (0.9 lb. VOC/1000 gal). Although ballasting and purging are different operations, they involve displacement of vapors remaining in the tank after cargo discharge.
(d) Control Factors
District Regulation 8, Rule 441 set limitation standards on storage tanks effective from January 1978. This Rule has helped to lower VOC emissions into the atmosphere from storage tanks.
(e) Speciation
The ROG/TOG ratios applied to this group of related categories are based on an Air District internal speciation profile. Multiple data sources have been used for developing speciation profiles, such as Air District-approved source tests, TOG speciation ratios used by other regional air quality agencies, and relevant literature including latest speciation profiles developed by CARB164 and the US Environmental Protection Agency165. For this group of categories, ROG constitutes 100% of TOG. Further assessment and improvement of ROG/ TOG speciation profiles has been planned in future inventory updates.
6.2.3 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).
6.2.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.2.5 Trends
(a) Historical Emissions / History
Historical emissions for point source emissions 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.
Prior years’ growth factors for area source categories were based on historical data (i.e. from the U.S. Army Corps of Engineers’ Waterborne Commerce reports, historical point source emission growth curves from the District’s internal database , etc.) and energy reports.
(b) 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 2020. The growth profiles for the current base year inventory have been verified and updated to represent the most likely surrogate for growing emissions for a given category up to year 2040. 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.
\[ \text{PE} = \text{Gr} * \text{Ci} * \text{Ei} \]
\(PE\) = 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 projected growth for the Ballasting categories (Cat. 86-90), the Marine Vessel Cleaning & Gas Venting category (Cat. 91), and the Non-Refinery Tanker/Barge Loading categories (Cat. 799-802) were based on fuels report obtained from the California Energy Commission website166.
Projected growth for all refinery related categories was based on the even extrapolation of California Annual Operable Atmospheric Crude Oil Distillation Capacity reduction from 2010 to 2020, i.e., it’s assumed a 0.67% decrease annually from 2021 to 2040. The data used in the extrapolation is taken from EIA website 2. The decrease is primarily driven by the shift to further increase fuel efficiency of vehicles through the U.S. Department of Transportation’s National Highway Traffic Safety Administration Corporate Average Fuel Economy (CAFÉ) standards as well as steady transition to electric vehicles and other alternative fuels (hydrogen fuel cell and others) in the California market.
6.2.6 Uncertainties
Throughputs for the point source categories are reported by via the BAAQMD 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.
For both point and area source emission factors, the main uncertainty in the updated methodology arises from the use of emission factors for certain categories that remain constant over several decades although technological controls may have been applied at facilities. Additionally, the emission factors themselves are seldom verified and validated against measurements, in part due to the difficulty in measuring fugitive emissions from area sources.
6.2.7 Contact
Author: Tan Dinh
Reviewer: Abhinav Guha, Yuan Du
Last Update: November 06, 2023
6.2.8 References & Footnotes
BAAQMD. 2011. Reg 8-44. https://www.baaqmd.gov/~/media/dotgov/files/rules/refinery-rules-definitions/rg0844_20211103-pdf.pdf?la=en&rev=9e140ed9dbd64d1b9bc57b3083d52568↩︎
US Energy Information Administration. Data ; [accessed 2023 March 07]. https://www.eia.gov/dnav/pet/pet_pnp_cap1_dcu_SCA_a.htm↩︎
USACE. 2008. (https://www.iwr.usace.army.mil/About/Technical-Centers/WCSC-Waterborne-Commerce-Statistics-Center-2/WCSC-Waterborne-Commerce/)↩︎
ORGPROF. CARB 2022. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎
SPECIATE. USEPA 2022. https://www.epa.gov/air-emissions-modeling/speciate↩︎
CEC. Reports ; [accessed 2023 March 07]. https://www.energy.ca.gov/data-reports/reports↩︎