Related DOT Programs

Aviation and Emissions Reductions

Introduction

In recent years, an increasing awareness has built of the environmental impacts of air travel. Although much of the focus has been on noise, aircraft emissions have become a topic of concern as well. Aircraft produce the same types of emissions as cars and trucks. In particular, aircraft jet engines produce carbon dioxide (CO2), water vapor (H2O), nitrogen oxides (NOx), carbon monoxide (CO), oxides of sulfur (SOx), unburned or partially combusted hydrocarbons (also known as volatile organic compounds, or VOCs), particulates, and other trace compounds. Aircraft engine emissions are roughly composed of about 70 percent CO2, a little less than 30 percent H2O, and less than 1 percent each of NOx, CO, SOx, VOC, particulates, and other trace components.¹

Relationship to Climate Change

As with surface vehicles, aircraft produce carbon dioxide through combustion of petroleum-based fuel. In addition, aircraft can have complex effects on climate through contrail formation and by emitting water vapor into the dry stratosphere. Aviation accounts for about 10 percent of greenhouse gas emissions from transportation in the U.S., or about 2.7 percent of total national greenhouse gas emissions. Air travel has grown significantly in the past decade, and is expected to continue to do so in the coming years.

However, there are many strategies targeted to improving the efficiency of our nation's air travel system that also have ancillary benefits related to the reduction of greenhouse gas emissions. Aircraft fuel efficiency has historically increased at about 1% per year, and research continues in engine efficiency, airframe aerodynamics, and the use of lighter materials. Changes in a variety of other factors such as operating procedures, aircraft routing, and load factors can also have significant impacts on greenhouse gas emissions per passenger mile.

DOT's Role

The Federal Aviation Administration of the DOT is involved with several different projects that could help promote reductions in greenhouse gas emissions from aircraft. These include initiatives in operations and research, and collaborations at the national and international levels:

Operations Initiatives:

New technologies to improve air traffic management will help reduce emissions. For instance, full implementation of Reduced Vertical Separation Minimums (RVSM), which have been used for transatlantic flights since 1997 and became standard in U.S. airspace in January 2005, may reduce fuel use by approximately 500 million gallons each year. Similarly, the implementation of Required Navigation Performance (RNP) integration into the U.S. national airspace system provides benefits from reduced fuel burn. Better meteorological information and yield management tools are improving the efficiency of the entire aviation network. Finally, the FAA Low-Emission Airport Vehicle (ILEAV) Pilot Program and the Voluntary Airport Low Emissions (VALE) Program assist in deploying low emissions technology to airport operations. While primarily focused on local air quality emissions, they also contribute to reduced greenhouse gas emissions.

Research initiatives:

The FAA has developed and continues to refine a unique capability to estimate aircraft emissions ranging from a single flight to regional and worldwide scales, called the System for Assessing Aviation's Global Emissions (SAGE). This model is used to generate aviation emission inventories for baseline conditions, forecasted technology and operational improvements, and market-based measures to reduce fuel usage. SAGE is used to calculate the aviation fuel efficiency goal as well as to assess and manage efforts to reduce aviation greenhouse gas emissions. SAGE has been used to support United Nations Framework Convention on Climate Change (UNFCCC) efforts.

The FAA is also engaged in a research activity to develop a robust new comprehensive framework of aviation environmental analytical tools and methodologies to assess interdependencies between noise and emissions and analyze the cost/benefit of proposed actions to mitigate these impacts. This framework of tools will allow optimizing activities to reduce aviation's environmental impact, including greenhouse gases. They include:

1. Environmental Design Space (EDS), which will provide integrated analysis of noise and emissions at the aircraft level.
2. Aviation Environmental Design Tool (AEDT), which is comprised of EDS integrated with existing or new aviation noise and emissions analytical modules to provide an integrated capability of assessing interrelationships between noise and emissions and amongst emissions at the local and global levels.
3. Aviation Environmental Portfolio Management Tool (APMT), which interacts with AEDT, EDS and economic modules to provide the common, transparent cost/benefit methodology, needed to optimize aviation policy in harmony with environmental policy.

In addition, the FAA, NASA and Transport Canada are jointly sponsoring research through the Partnership for Air Transportation Noise and Emissions Reduction (PARTNER) Center of Excellence to reduce uncertainties associated with the impact of non-CO2 (e.g., contrails, oxides of nitrogen, and particulates that induce cirrus clouds) aviation emissions on climate. The goal is to reduce uncertainties to levels that enable appropriate action.

National Collaborative Activities:

The Next Generation Air Transportation System (NGATS) is a multi-agency integrated effort (with the National Aeronautics and Space Agency (NASA), Department of Defense, Department of Commerce, Department of Homeland Security, and the Office of Science and Technology Policy) to ensure that the future air transportation system meets air transportation security, mobility and capacity needs while reducing environmental impacts. The NGATS plan includes an environmental objective to produce absolute reductions in aviation's significant environmental impacts so as to foster sustained aviation growth. The Environmental Integrated Product Team (EIPT) is addressing a number of strategies to achieve this objective that will also improve fuel efficiency, including research on new engines, enhanced engine cycles, more efficient aircraft aerodynamics, and reduced weight. It is also pursuing science activities to reduce uncertainties in understanding aviation's atmospheric impacts to levels that enable appropriate action.

International Collaborative Activities:

The International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP) adopted 3 environmental goals for the organization in October 2004- to limit or reduce noise exposure, local air quality emissions, and greenhouse gas emissions. The FAA leads U.S. participation in CAEP and is supporting work programs to make progress on achieving these goals. On greenhouse gas emissions, the FAA is working with its counterpart authorities through ICAO to explore the use of voluntary agreements to deal with this issue. FAA was also instrumental in the development of ICAO guidance in the area of best operational practice to reduce fuel usage.

The FAA also supports other United Nation's activities, including taking a leadership role in drafting the aviation chapter of the Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines for Greenhouse Emissions. These guidelines will be used by nations worldwide to track progress in reducing greenhouse gases.

Additional Information

Aviation and Emissions, A Primer

Aircraft and Contrails Fact Sheet

¹ Federal Aviation Administration, Office of Environment and Energy, "Aviation & Emissions: A Primer," January 2005.