6.5 Non-Gasoline Terminals and Bulk Plants Storage
Category 938
6.5.1 Introduction
Category 938 accounts for the organic emissions (TOG and ROG) from the storage of organic liquids (non-gasoline) in tanks at bulk plant and terminals. The emissions are due to breathing and working losses. Breathing loss is the expulsion of vapor from tank due to vapor expansion and contraction of the liquid in the tanks. Working loss occurs when vapor is displaced during tank loading operations and when air drawn into the tank during unloading operations.
6.5.2 Methodology
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.
Category 938, Non-Gasoline Terminals and Bulk Plants Storage is considered a point source category and follows the above methodology for emissions estimates.
The sources that fall under category 938 are subject to District Rule 8-6, Terminals and Bulk Plants. This rule was adopted in March 1982 and amended 1983 and 1994. The amended rules require reducing emissions of organic liquid loaded from loading operations at terminals and bulk plants.
In 2020 and 2021, two of the five petroleum refineries in the Bay Area submitted permit applications to modify the facility operation to process alternative feedstocks with the intention of producing “renewable” products. Regulation 8, Rule 6 was passed on November 03, 2021. 174
This source category reports Total Organics Gas (TOG) emissions. The ROG: TOG ratio is equal to 1.
6.5.3 Changes in Methodology
No major changes in methodology were made in this version of the base year emissions inventory.
6.5.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.5.5 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 to 1999 Base Year source inventory, this category had been included from storage tank at bulk plants and terminals categories.
(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 reported year-to-year variation in emissions is due to changes in either the volume of materials put through the storage tank, or in the composition of the organic liquids stored. There is no data available to project emissions for this category. Therefore, projected emissions are based on the EIA statistics of California Refinery Annual Operating Atmospheric Crude Oil Distillation Capacity.
6.5.6 Uncertainties
The estimated emissions for Category 938, Gasoline Bulk Plant Storage Tanks are largely based on five petroleum refineries in the Bay Area. Any uncertainty in the emissions estimates at these facilities contribute to an increased uncertainty of the point source emissions.
6.5.7 Contact
Author: Michael Nguyen
Reviewer: Ariana Husain
Last Update: November 06, 2023
6.5.8 References & Footnotes
BAAQMD. 2021. Regulation 8, Rule 6 - Terminals and Bulk Plants, https://www.baaqmd.gov/~/media/dotgov/files/rules/refinery-rules-definitions/rg0806_20211103-pdf.pdf↩︎