Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
8 Understanding airport air quality requires understanding airport emissions and their impact on people and the environment. The first step in understanding airport emissions is identifying all emission sources. Primary emission sources at airports are aircraft, cars, trucks, and other vehicles operating at the airport that create emissions as a result of fuel combustion. This includes aircraft operations on the ground and in the air, vehicle traffic to and from the airport, shuttle buses and vans serving passengers, and GSE that services aircraft. Other common emissions sources at the airport include aircraft auxil- iary power units (APUs), equipment providing electricity and air conditioning to aircraft parked at airport terminal gates, and stationary airport power sources and emergency generators. Firefighter training is also a source of fuel combustion emissions at airports. While not part of routine airport operations, construction projects are a significant source of airport emissions. It is important to identify emissions from specific types of equipment as well as the impact of construction activity generally. Additionally, some emissions result from fuel or chemical evaporation. Fuel farm operations and aircraft fueling, aircraft deicing, and maintenance operations like solvent cleaning and paint- ing are sources of evaporative emissions. Finally, some pollutants result from wind-blown dirt, salt, or sand from materials stored in piles in the open. Once identified, quantifying emissions from these many sources over a common time period generates an emissions inventory. To develop an emissions inventory, it is useful to categorize sources with common characteristics. EPA categorizes emissions sources as mobile and stationary sources. In airport terms, mobile sources include aircraft, APUs, GSE, cars, trucks, and other ground vehicles. Regulatory standards or permits for mobile sources are applied to the manufacturer. Stationary sources can be point, area, or volume sources. Point sources include boilers and emergency generators. Area sources are groupings of many smaller sources that emit pollutants over a wide area. Parking lots and paint booths are examples of area sources found at airports. Volume sources are groupings of many smaller sources that emit pollutants over a large volume. Fuel tanks are examples of volume sources found at airports. Stationary sources are permitted by the airport to the extent permits are needed (see Section 6: Air Environmental Regulations Applicable to Airports). Construction emissions are predominantly from mobile sources mixed with area sources (emissions from earth moving and similar actions). S E C T I O N 3 Airport Emissions and Sources Primary Airport Emission Sources ⢠Aircraft ⢠GSE ⢠Maintenance activity ⢠Airport support facilities ⢠Heat and power generation ⢠Cars and other vehicles ⢠Construction activity
Airport Emissions and Sources 9 3.1 Mobile Sources 3.1.1 Aircraft Most aircraft emissions come from the main engines of aircraft operating at the airport. This includes commercial (air carrier and cargo), air taxi, general aviation (GA), military aircraft, and helicopters. Aircraft main engines propel aircraft forward and are gen- erally classified as either (1) gas turbine turbofan, turbojet, or turboprop engines and fueled with aviation kerosene (i.e., jet fuel or Jet A) or (2) internal combustion piston engines fueled with aviation gasoline (commonly known as âavgasâ or 100 octane low-lead â100LLâ). Aircraft engines produce emis- sions from the combustion of fuel, which varies depending on aircraft engine type, fuel type, and number and size of engines, engine power settings, amount of fuel burned, and other vari- ables (e.g., temperature, altitude, etc.). 3.1.2 APUs APUs are smaller turbine engines that provide power to an aircraft during approach, while taxiing, or when positioned at the terminal gate. APUs power the aircraftâs instruments, lights, heat and air conditioning, and other equipment and are used for starting the main aircraft engines. APUs burn jet fuel and are common on both large commercial and military aircraft and some air taxi and GA aircraft. APUs remain in use while the aircraft is parked and ser- viced at the gate, unless an alternative source of electricity and preconditioned air is made available. In such cases, APUs are reactivated several minutes before the aircraft leaves the gate or parking space. Normally, APUs are turned off after the main engines have been started, prior to takeoff. 3.1.3 GSE GSE is the equipment that services aircraft while passengers and freight are being loaded and unloaded at an airport. The types of GSE and their use depend on the aircraft type and the designated category of an aircraft operation (e.g., passenger, cargo, etc.). GSE consists of baggage tugs, belt loaders, cargo loaders, aircraft tugs, air start units, air-conditioning units, ground power units (GPUs), fuel or hydrant trucks, cater- ing trucks, cabin trucks, deicer trucks, water trucks, lavatory trucks, forklifts, and tractors, among others. Air emissions resulting from the operation of GSE vary depending on the number and type of equipment used to
10 Airport Air Quality Management 101 service each aircraft, along with the duration of equipment operation per aircraft landing and takeoff cycle (LTO) and the fuel type (e.g., gasoline, diesel, propane, electric, etc.). 3.1.4 Ground Access Vehicles Ground access vehicles encompass motor vehicles traveling along on- and off-airport roadways and idling along terminal curbsides. These include airport passenger vehicles (e.g., private autos, taxis/limousines, shuttles, vans, buses, rental cars, etc.), vehicles transporting airport and tenant employees, and vehicles transporting cargo to and from the airport. Air emissions associated with these vehicles are a function of traffic volumes and speeds, distances traveled, vehicle operat- ing characteristics, fuel type, and ambient conditions. 3.2 Stationary Sources Stationary sources of air emissions at airports consist of both fuel combustion and non-combustion sources. Typical stationary sources include central utility plants, power gen- eration facilities, boilers, heaters, generators, snow melters, incinerators, fire-training facilities, aircraft engine testing, fuel storage tanks, cooling towers, coating and painting oper- ations, de-icing and anti-icing operations, solvent degreasers, and sand/salt piles. Air emissions associated with fuel combustion are a func- tion of equipment type, equipment size, fuel type, combustion processes and air emission control measures. Non-combustion sources typically emit evaporative emissions (e.g., fuel storage tanks) and/or fugitive dust emissions (e.g., sand and salt piles). 3.3 Construction Construction activities are temporary and variable depend- ing on location, duration, and level of activity and are generally confined to a construction site and access roadways. Con- struction emissions occur predominantly from mobile sources such as the operation of heavy construction equipment (e.g., backhoes, bulldozers, pavers), on- and off-road vehicles used for the transport and delivery of supplies and material (e.g., cement trucks, dump trucks), and on-road vehicles used by construction workers getting to and from a construction site (e.g., cars, pickup trucks). Construction emissions also include fugitive dust produced from construction materials staging, demolition, and earth moving activities, as well as evaporative emissions from asphalt paving.
Airport Emissions and Sources 11 An important challenge in calculating construction emissions is determining construction equipment activity. It is one of the two components (emission factor and activity data) necessary to create an emissions inventory (see Section 4: Air Quality Analysis). Activity data represent the amount of time that individual types of equipment are being used on a specific project. Computing emissions from construction projects typically takes a lot of experience. It is impor- tant to understand the activity types and/or phases that constitute a project and the specific equipment and time of use during each activity type. To simplify this process, ACRP conducted a project (ACRP Project 02-33) to define the equipment types and activity data needed for various projects that are typical for an airport. The results of that project were published in ACRP Report 102: Guidance for Estimating Airport Construction Emissions. Also developed under ACRP Project 02-33 was the Airport Construction Emissions Inventory Tool (ACEIT), which provides users with default information about the construction process for typical airport projects and calculated emissions from construction projects. A video providing instructions for using ACEIT can be found in the companion product to ACRP Research Report 185, the Airport Air Quality Resource Library. Essential References for Section 3: Airport Emissions and Sources ⢠Aviation Emissions, Impacts & Mitigation: A Primer, U.S. FAA Office of Environment & Energy, 2015 ⢠Aviation Emissions and Air Quality Handbook, Version 3, Update 1, FAA Office of Environment & Energy, January 2015 ⢠Airport Air Quality Manual, International Civil Aviation Organization, 2011 ⢠ACRP Report 102: Guidance for Estimating Airport Construction Emissions, Transportation Research Board, 2014 (includes ACEIT and instructional video)
