6.8 Gasoline Filling Station Spillage
Category 66
6.8.1 Introduction
Category 66 covers organic emissions (TOG and ROG) from Gasoline filling station spillage. Gasoline spillage occurs during filling such as pre-fill and post-fill nozzle drip and overflow from the vehicle’s fuel tank at service stations. The amount of spillage loss can depend on the service station business characteristics and nozzle types (conventional nozzle or vapor recovery nozzle).
6.8.2 Methodology
This category is considered an area source category since it covers 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.
(a) Activity Data / Throughput
The estimates of gasoline consumption in the Bay Area were obtained from California Energy Commission (CEC) , California Annual Retail Fuel Outlet Report Results 181 report.
(b) County Distribution / Fractions
County annual gasoline fuel consumption distributed into the Bay Area counties were based on CEC California Annual Retail Fuel Outlet Report County breakdown. The gasoline consumption throughput for Solano and Sonoma counties is apportioned based upon CEC’s throughput and CARB’s county estimated emissions.
(c) Emission Factors
The uncontrolled emission factor for GDF Spillage was based on EPA’s Transportation And Marketing Of Petroleum Liquids methodology. The uncontrolled TOG emission factor was 1.34 lbs per 1000 gallons prior to Base Year 1981. This uncontrolled emission factor was adjusted to 0.70 lbs per 1000 gallons to be consistent with EPA’s AP-42 methodology.
(d) Control Factors
There are no specific CARB regulations or District rules that apply to this category. However, the improvement of the vapor recovery nozzle technology has reduced spillage at vehicle filling services stations. GDF Spillage control factors are based on the nozzle improvement required by Phase II GDFs and CARB’s lowering of the allowable spillage limit (0.24 lbs/1000 gal).
(e) Speciation
The total organic gas (TOG) emissions from the Gasoline spillage category are considered all reactive organic gas (ROG). The ROG:TOG ratio is equal to 1.
6.8.3 Changes in Methodology
No major changes in methodology were made in this version of the base year emissions inventory. The base year estimates of gasoline consumption (Annual throughput) for these Gasoline Truck Transport categories were obtained from CEC.
6.8.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.8.5 Trends
(a) Historical Emissions/History
Prior to Base Year 1999, taxable gasoline sales for California obtained from the Board of Equalization were assumed to distribute to all gasoline filling stations. Gasoline consumption in 2007 reached record levels. However, the gasoline consumption decreased slightly during the economic recession in 2008-2010. Base Year 2011 gasoline consumption in the Bay Area is based on the California State Board of Equalization, Fuel Taxes Statistics & Reports and Caltrans Transportation Planning Support Information System (TPSIS). These estimates were made by adjustments of Gasoline Dispensing Facility sales, population, number of registered vehicles, and the number of drivers’ license. In 2012, California Air Resources Board (CARB) updated the emission factors for gasoline storage, transfer operations from cargo tank trucks, fuel containers, and gasoline-powered equipment.
(b) Future Projections/ Growth
Projections are based on CARB’s Emission Factor (EMFAC) model, EMFAC2021 182, which includes estimates of gasoline consumption in the Bay Area. Due to the coronavirus pandemic impact on the economy, gasoline consumption dropped significantly in 2020. With the new requirements of the California Executive order 183 to phase out gasoline powered cars and passenger trucks by 2035, the GDF categories’ emissions are expected to be further reduced for forecasted emission years.
6.8.6 Uncertainties
There were uncertainties associated with emission factor estimates of test data locations in which the temperature is not comparable to Bay Area temperature data. The gasoline consumption estimates for Solano and Sonoma counties could also contribute to an increased uncertainty of the Bay Area gasoline consumption for the base year emission inventory.
6.8.7 Contact
Author: Michael Nguyen
Reviewer: Ariana Husain
Last Update: November 06, 2023
6.8.8 References & Footnotes
CEC. 2021. California Annual Retail Fuel Outlet Report Results (CEC-A15) https://www.energy.ca.gov/data-reports/energy-almanac/transportation-energy/california-retail-fuel-outlet-annual-reporting↩︎
CARB. 2022. EMFAC2021 emissions inventories of onroad mobile sources in California: https://arb.ca.gov/emfac/↩︎
CA Executive order. 2020. Governor Newsom Announces California Will Phase Out Gasoline-Powered Cars & Drastically Reduce Demand for Fossil Fuel in California’s Fight Against Climate Change, https://www.gov.ca.gov/2020/09/23/governor-newsom-announces-california-will-phase-out-gasoline-powered-cars-drastically-reduce-demand-for-fossil-fuel-in-californias-fight-against-climate-change/ ↩︎