Concerns are increasing over the potential effects of anthropogenic activities on the earth's climate. Scientific studies suggest that human activities, including aviation, contribute to increasing atmospheric concentrations of greenhouse gas (GHG) emissions, which are considered to be associated with global warming. According to the United Nations Intergovernmental Panel on Climate Change (IPCC), aviation activities affecting the atmosphere through the combustion of fuel are currently thought to contribute about 2 to 3 percent to total global GHG emission inventories and could contribute as much as 5 percent by 2050.
Noise and local air quality concerns remain the primary environmental issues facing airports in the United States today. This is in contrast with Europe, where climate and sustainability concerns increasingly drive agendas. However, concern about GHG emissions in the United States is growing and some states and municipalities are taking legislative actions and implementing controls.
While approaches for computing noise and local air quality at the airport level are generally well established, there is no specific guidance or generally applied practice for computing airport-level GHG emission inventories. Under international treaties, GHGs are addressed at a national or state level. However, responding to local political concerns, cities and counties across the country are beginning to attempt to quantify the contribution of sources within their boundaries to local and regional GHG emissions without a basic common understanding and source of reference material. As one example, in Aspen, Colorado, the city's "Canary Initiative" found aviation emissions represent over 40 percent of locally generated emissions. The state of California has estimated that aviation represents 12 percent of carbon dioxide equivalent emissions. For comparison purposes, the city of Seattle, Washington, estimates that aviation contributed 17 percent to Seattle's GHG emissions. The wide variance and levels of the estimated local aviation contributions is most likely a result of the methodology used to quantify and compare emissions rather than actual level or variance in the type of activities. For example, it is unclear from these efforts how much of the variance may be due to double counting of emissions.
Additionally, it is not clear whether all these studies employed consistent emission estimation methodology and databases. There is a growing need to provide airport operators with clear and cohesive information on the national inventory of airport-level GHG emissions. Unlike noise or local air quality emissions, GHG emissions have no local impacts; hence, the value of such reporting at the local airport level is not clear. If such reporting is done, there should be an established methodology on how to estimate carbon dioxide equivalence of non-carbon dioxide airport-related GHG emissions.
Given the rising level of interest regarding aviation's contribution to GHG emissions and ultimately to climate change, it is imperative that airports have the most up to date information necessary to address potential concerns. On a sub-regional level, many localities have begun to develop aviation-related GHG inventories using different methodologies and accounting approaches. Airport operators would benefit from a guidebook that provides uniform methods of calculating airport GHG emissions inventories.
The objective of this research is to develop a guidebook that can be used to prepare airport source-specific inventories of greenhouse gas (GHG) emissions. The guidebook shall provide methods to calculate airport GHG emissions inventories in a consistent manner and will provide information on considerations that should be taken into account when scoping and preparing such inventories. This guidebook should focus on the following six GHG emissions since they are widely recognized as relevant and quantifiable: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluoro compounds (HFC), and perfluorocarbons (PFC). Status:
The final report has been published as ACRP Report 11. The appendices are available on the TRB website as ACRP Web-Only Document 2.