9.18 Airport Ground Support Equipment

Categories 2355 - 2366

9.18.1 Introduction

Considered in these categories are criteria pollutant emissions (particulate, organic, NO_x, SO_x, and CO) from airport Ground Support Equipment (GSE) that service the aircraft while loading and unloading passengers and freights at the major airports in the San Francisco Bay Area.

Category	Description
2355	Ground Support Equipment (SFO) - Diesel
2356	Ground Support Equipment (SFO) - Gasoline
2357	Ground Support Equipment (SFO) - Natural Gas
2358	Ground Support Equipment (OAK) - Diesel
2359	Ground Support Equipment (OAK) - Gasoline
2360	Ground Support Equipment (OAK) - Natural Gas
2361	Ground Support Equipment (SJC) - Diesel
2362	Ground Support Equipment (SJC) - Gasoline
2363	Ground Support Equipment (SJC) - Natural Gas
2364	Ground Support Equipment (Travis AFB) - Diesel
2365	Ground Support Equipment (Travis AFB) - Gasoline
2366	Ground Support Equipment (Travis AFB) - Natural Gas

The three large commercial airports in the Bay Area are: San Francisco International (SFO), Oakland International (OAK), and San Jose International (SJC). The Bay Area is also home to a military airbase in Solano County, the Travis Air Force Base (AFB). Examples of the GSE include baggage/aircraft tractors and tugs, ground power units, air start units, auxiliary power units, cargo belt loaders, cargo moving equipment, fuel trucks, food service trucks, and other assorted service vehicles. Much of the equipment in use at the Bay Area commercial airports are fueled by gasoline or diesel; however, some equipment is fueled by alternative fuels such as compressed natural gas (CNG), liquefied petroleum gas (LPG), or electricity.

9.18.2 Methodology

For the airport Ground Support Equipment (GSE) categories, emissions data are derived by inventory staff of the California Air Resources Board (CARB)⁴²³. For each airport, there is a set of three categories that cover emissions by equipment and fuel type: Categories 2355, 2357, and 2357 account for emissions from San Francisco International (SFO); Categories 2358, 2359, and 2360 account for emissions from Oakland International (OAK); Categories 2361, 2362, and 2363 account for emissions from San Jose International (SJC); and Categories 2364, 2365, and 2366 account for emissions from Travis Air Force Base. The combined ground support equipment population for large Bay Area airports is estimated to be about 1100 pieces of equipment. The main fuels used for GSE are diesel, gasoline and compressed natural gas.

The CARB’s emissions dataset is published every few years and is a product of the State Implementation Plan (SIP) emissions document formally known as the California Emissions Projection Analysis Model (CEPAM) inventory⁴²⁴. For categories, such as airport ground support equipment (GSE), where independent data collection and derivation of emissions are both cost- and time-prohibitive and likely a redundant effort, BAAQMD staff imports the emissions data directly from CEPAM into the District’s Base Year inventory package. This calculation approach and collection of categories are internally termed as “CARB Source Categories”.

The CEPAM provides historical emissions as well as forecasts emissions for major emission source classifications including –

1. on-road mobile sources [from Emissions Factor (EMFAC) model]
2. off-road mobile sources (OFFROAD model)
3. stationary and areawide sources - For these major source classifications, CEPAM combines facility level /area source emissions data reported to the California Emissions Inventory Development and Reporting System (CEIDARS) for multiple years by various regional air quality agencies (including the BAAQMD).

The current base year inventory uses the 2016 CEPAMv1.05² to estimate emissions from “CARB Source Categories”. This version of the CEPAM derives emissions from a 2012 base year inventory and contains backcasts and forecasts from year-2000 to year-2035. All applicable regulatory and technological controls are assumed to be built into the CEPAM dataset during CARB staff’s inventory computation work. After the emissions data are imported, the inventory for CARB Source categories is taken through a quality assurance (QA) process.

In the QA process, BAAQMD staff 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). Based on the scope of emissions covered, individual EIC or a group of EICs are mapped to the Air District’s single cat_id. This process also addresses issues when cat_ids have no matching EICs or there are discontinued EICs that need to be investigated. Following this, emissions data are backcasted to year-1990, as well as forecasted to year-2040 using certain mathematical methods, as described in the Trends section. Finally, the emissions trends spanning from year 1990-2040 for each category and pollutant are evaluated, and CARB staff are consulted for explanation of any observed anomalies in trends.

Distribution of emissions into each county is based on Ground Support Equipment activity and population in each county.

9.18.3 Changes in Methodology

In this version of the emissions inventory (base year 2015), entire emission estimation methodology from CARB has been adopted. For previous base year inventories, emission estimates were made by the Air District staff using the CARB data, such as, emission factors, equipment population and other factors such as break horsepower (BHP), load factors, and typical hours of equipment usage etc.

9.18.4 Emissions

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

9.18.5 Trends

(a) Historical Emissions / History

Emissions growth through the years was estimated based on the number of aircraft operations at each airport.

Three different methods are used for backcasting to project historical emissions prior to year-2000 going back to year-1990, which is the starting year of the current base year inventory (referred to as BY2015). Following preliminary evaluation of the data available for initial years (post-year 2000) in the CEPAM inventory, BAAQMD staff recommends a backcasting approach. The default backcasting approach is defined by a formula here –

\[ \begin{eqnarray} \text{BY2015 emissions for year X for county Y} = \text{BY2011 total emissions for year X} \\ \\ \times \dfrac{\text{BY2015 year-2000 emissions}}{\text{ BY2011 year-2000 emissions}} \\ \\ \times \dfrac{\text{county Y fraction}}{\text{ fractional total}} \end{eqnarray} \]

This calculation is referred to as the BY2011 scaling method (based on the previous base year inventory). The second calculation approach is to derive the linear regression best fit of the year 2000-2008 CARB Sources emissions data for a category, species, and county, and extrapolate that data back in time. If this backcasting results in negative emissions prior to a certain year, the lowest positive emission value is held constant from that particular year back to year-1990. The third possible calculation approach is to use a specific growth profile for the category, provided by the in-house staff expert. These custom growth profiles are often derived from surrogate data provided by another agency or resource, or available activity data that is assumed to scale with the emissions for that specific CARB Source category.

For the airport GSE categories, the BY2011 scaling method is used to derive emissions for years 1990 through 1999.

(b) Future Projections / Growth

Projections are based on combined information of aircraft operations in accordance with FAA, the Metropolitan Traffic Commission (MTC) and the San Francisco Bay Area airports. Emissions forecasting was done by holding the year-2035 emissions data constant through and up to year-2040. For CARB Sources, emissions are forecasted by CARB staff by applying growth profiles to the base year-2012 inventory data (see above in ‘Methodology’ section).

9.18.6 Uncertainties

The CARB methodology used off-road equipment fleet surveys such as, population, engine size, load factors, hours of use, and emission factors for emission inventory development. It is assumed that these equipment fleet surveys are still applicable under current conditions. Emission estimations can be improved by conducting another equipment fleet survey that will reflect current conditions.

9.18.7 Contact

Author: Sukarn Claire

Reviewer: Ariana Husain

Last Update: November 06, 2023

9.18.8 References & Footnotes