6.11 Gasoline Filling Station - Excess Emissions
Category 1197
6.11.1 Introduction
Category 1197 covers organic emissions (TOG and ROG) for excess emissions from gasoline dispensing nozzles at gasoline service stations. In 1995, 352 gasoline service stations in the Bay Area were equipped with vacuum-assist Phase II vapor recovery systems utilizing bootless nozzles. The bootless nozzle design typically, but not always, uses a coaxial spout design. Product flows through the inner tube, while a vacuum pump draws the vapors through the outer portion of the coaxial spout, thus keeping vapor from escaping. The recovered vapors are then sent back to underground storage tank under a slight pressure. Because of excess dispensing rates, and certain design issues, the initial bootless nozzles were more prone to spitback and spillage. The primary marketing advantage of the bootless nozzle is that it does not require the bellows necessary on balance-type nozzles. The excess emissions from gasoline dispensing nozzles at gasoline service stations are comprised of spitback, pseudo-spillage, low Air to Liquid (A/L) ratio, pressure-related fugitive emissions, idle-nozzle emissions occurring after a refueling using Emco Wheaton A4001 nozzles, and “whoosh” emissions. The “Whoosh” emissions are the emissions released when the gasoline cap on the vehicle tank is removed for fueling. Spitback, pseudo-spillage, low air to liquid ratio, and pressure-related fugitives excess emissions apply only to Phase II vapor recovery systems using “bootless” nozzles. Idle nozzle emissions apply to refueling events using Emco Wheaton A4001 balance-type nozzles. Due to EPA/CARB requirements, District regulations and the aggressive enforcement, the Spitback, pseudo-spillage, low air to liquid ratio, and idle-nozzle excess emissions are no longer applicable.
6.11.2 Methodology
The excess emissions are comprised of pressure-related fugitive emissions and “whoosh” emissions. For Pressure-Related Fugitives, many of the defects causing the low Air to Liquid (A/L) ratio at the bootless nozzle system that allows ambient air to be ingested into the underground storage tanks. This air evaporates liquid gasoline, creating an increase in the storage tank headspace pressure. Excess headspace pressure in the storage tank results in excess pressure-related fugitive emissions. The “Whoosh” emissions are the emissions released when the gasoline cap on the vehicle tank is removed for fueling.
(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 196 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
Pressure-Related Fugitives emission factor was estimated to be 3.97 lbs/1000 gallons based on the results of several tests conducted by District Source Test Engineers.
Emission factor (0.66 lbs/1000 gallons) for “whoosh” emissions was obtained from “Gasoline Service Station Industrywide Risk Assessment Guidelines” 197 prepared by the Toxics Committee of the California Air Pollution Control Officers Association (CAPCOA), December 1997.
(d) Control Factors
California Air Resources Board (CARB) adopted a series of new Enhanced Vapor Recovery (EVR) amendments to its gas station vapor recovery regulations (Phase I and Phase II) in March 2000. The adopted amendments also include mandatory In-Station-Diagnostics (ISD), which are requiring electronic monitoring of vapor recovery system operation and performance. The certification requirement of In-Station-Diagnostics was expected to be fully implemented by April 2004. In addition, CARB adopted new standards:
- to make vapor recovery system compatible with on-board vapor recovery (ORVR) systems on motor vehicles,
- to reduce gasoline spillage, liquid retain in the nozzles, and
- to pressure-related fugitive emissions.
For pressure-related fugitives, District developed two additional inspection procedures:
- a simple visual inspection procedure for both the affected industry and local inspectors to detect vapor leaks in the Phase I equipment, and
- an inspection procedure to determine compliance with the pressure integrity performance specification (0.38 CFH @ 2.0 inches water column) for drop tube based overfill protection.
These changes improve the performance of Phase I equipment in service stations and maintain the integrity of the systems between tests. The pressure-related fugitive emissions have been reduced by 95 percent.
For Whoosh emissions, some onboard refueling vapor recovery (ORVR) systems in post 2000 cars have a design which minimizes the pressure-related vehicle tank headspace losses when the fill cap is removed. It is estimated that 90 percent of these excess emissions have been reduced.
(e) Speciation
The total organic gas (TOG) emissions from gasoline dispensing nozzles at gasoline service stations are considered as all reactive organic gas (ROG). The ROG:TOG ratio is equal to 1.
6.11.3 Changes in Methodology
No major changes in methodology were made in this version of the base year emissions inventory. However, for this base year, the excess emissions category accounts for pressure-related fugitive emissions and “whoosh” emissions. Estimates of gasoline consumption for the excess emissions category were obtained from CEC.
6.11.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.11.5 Trends
(a) Historical Emissions/History
The historical excess emissions were comprised of spitback, pseudo-spillage, low air to liquid ratio, pressure-related fugitive emissions, idle-nozzle emissions occurring after a refueling using Emco Wheaton A4001 nozzles and “whoosh” emissions. The Spitback, pseudo-spillage, low air to liquid ratio, and pressure-related fugitives excess emissions apply only to Phase II vapor recovery systems using “bootless” nozzles. Idle nozzle emissions apply to refueling events using Emco Wheaton A4001 balance-type nozzles.
US EPA requirement to limit dispensing rates (10 gallons per minute or less), effective on July 1, 1996 all of the excess emissions due to spitback emissions have been eliminated.
Bay Area AQMD developed an inspection procedure, GDF-IP-04, to quantify these emissions on a per nozzle basis and limit pseudo-spillage to 3 drops per minute. Regulation 8, Rule 7 was amended to limit pseudo-spillage on all new installations.
The emissions caused by low Air to Liquid (A/L) Ratios occur both as reduced collection efficiency during the refueling event and increased pressure-related emissions caused by air ingestion through leaks in nozzles not being used during the refueling activity. The Bay Area has worked closely with CARB to have one dispenser manufacturer require retrofitting systems which had liquid traps in the vapor piping to eliminate this problem. All new and rebuilt nozzles are also now equipped with the improved spouts. The Bay Area AQMD also imposed an Abatement Order on Shell, the company which has the largest population of bootless systems. As a result, A/L tests are being conducted quarterly and equipment checks, including the “Bag Test” developed by the Bay Area AQMD are required to be conducted monthly.
For Idle Nozzle emissions, a revision to Regulation 8, Rule 7 disallowed the use of balance nozzles without an integral vapor valve (i.e. the Emco-Wheaton A4001 nozzles).
(b) Future Projections/ Growth
With the new requirements of the California Executive order198 to phase out gasoline powered cars and passenger trucks by 2035, the excess emissions from gasoline dispensing nozzles at gasoline service stations categories are expected to be further reduced in the forecasted emission years.
6.11.6 Uncertainties
The gasoline consumption estimates for Solano and Sonoma counties could also contribute to an increased uncertainty of the Bay Area gasoline consumption for base year emission inventory.
6.11.7 Contact
Author: Minh Nguyen
Reviewer: Sukarn Claire
Last Update: November 06, 2023
6.11.8 References & Footnotes
CEC. 2021. CEC 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. 1997. Gasoline Service Station Industrywide Risk Assessment Guidelines, https://ww2.arb.ca.gov/resources/documents/gasoline-service-station-industrywide-risk-assessment-guidance↩︎
CEC. 2021. 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/ ↩︎