Airport Greenhouse Gas Emissions Inventory: A Primer (2024)
Chapter: 1. Select and Apply GHG Protocols and Guidance Documents
1. Select and Apply GHG Protocols and Guidance Documents
1.1 Greenhouse Gas Protocol-Aligned Guidance
The GHG accounting methodology and management outlined in this primer is developed in line with the GHG Protocol Corporate Accounting and Reporting Standard (GHG Corporate Standard). The GHG Corporate Standard is one of the most widely used GHG accounting standards in the world. Although airports are public entities, their organizational structure is often similar to private companies for GHG accounting purposes, thus this Guidance is modeled after the GHG Corporate Standard. The GHG Corporate Standard is also used by the Airport Carbon Accreditation (ACA) Program.
The GHG Corporate Standard and this Guidance employ five principles to guide high-quality GHG accounting and reporting:
Relevance – GHG inventories should reflect the emissions of the airport and serve as a decision-making tool for internal and external stakeholders.
Completeness – GHG inventories should account for and report all emissions from sources within the airport’s selected inventory boundary.
Consistency – GHG inventories should use consistent methodologies to compare emissions over time and transparently document any methodological changes over time.
Transparency – GHG inventories should clearly address any issues with the inventory and document any assumptions, references, and methodologies used in the accounting process.
Accuracy – GHG inventories should ensure that emissions calculations are as accurate as reasonably possible by reducing uncertainties so that they are effective decision-making tools. In addition to the GHG Corporate Standard, this primer was also developed in line with the GHG Protocol Scope 2 Guidance, the Corporate Value Chain (Scope 3) Accounting and Reporting Standard (GHG Scope 3 Standard), and the Technical Guidance for Calculating Scope 3 Emissions. These guidance documents complement the GHG Corporate Standard by providing best practices for gathering data and calculating emissions for Scope 2 and Scope 3 emission sources.
Why Follow the GHG Corporate Standard?
The vast majority of airports in the U.S. are owned and operated by government entities, such as state and local governments. Public ownership allows airports to have a unique position as critical transportation hubs and fulfill public service responsibilities. However, although airports are typically owned by public agencies, they exhibit characteristics of corporations and adopt business-like practices. For example, airports generate revenue, allowing them to cover their operational costs, meet financial goals, and invest in airport development. Airports also participate in market competition—competing for airline and passenger traffic by offering attractive services, incentives, and facilities to appeal to their customers. In many cases, private sector entities are deployed to run airport operations in part or in full. Because of these functional similarities, airports often find that the GHG Corporate Standard is an effective reference standard for preparing airport GHG emission inventories.
1.2 Airport Emissions in the Context of City Emissions
As mentioned, airports are typically public entities, but can be thought of as commercial entities for the purposes of GHG accounting. However, an airport’s GHG inventory may be incorporated into a city-scale GHG inventory as they can make up a significant portion of a city’s transportation sector emissions.
The Global Protocol for Community-Scale Greenhouse Gas Inventories directs cities to account for emissions from airport energy use and aviation trips within the boundary of a city under the city’s Scope 1 emissions, emissions from electricity use, either from airports or vehicles charging using electricity at airports, under Scope 2, and emissions from all departing flights under Scope 3.
Because the inventory boundaries for cities and airports are different, you should ensure that emissions from different airport and airport tenant activities can be easily disaggregated so as to assist your city in its own GHG emissions consolidation and inventory preparation.
