GHG Inventories: Systematic Way of Accounting Greenhouse Emissions

Greenhouse gas (GHG) inventory, also known as carbon footprint assessment, is the process of calculating and documenting the emissions associated with the various activities of corporates, entities or even nations. The inventory takes in consideration the main seven greenhouse gasses which are: Carbon Dioxide, Methane, Nitrous Oxide, Hydrofluorocarbons, Perfluorocarbons, Sulfur Hexafluoride, and Nitrogen Trifluoride. 

It provides an accurate indicator in evaluating how green an entity is as well as measuring the progressions and the impacts of actions done toward managing the overall emissions. The GHG inventory is conducting for diverse reasons including but not limited to:

1. Managing GHG risks and identifying reduction opportunities.
2. Identifying the largest GHG emitters within a boundary.
3. Tracking GHG performance over time.
4. Creating a plan to reduce emissions.

Inventories Methodologies

There are several methodologies for conducting a GHG inventory, these methodologies provide the guidance and standards for identifying the boundaries of the inventory, the scopes which the emissions are classified based on, the methods by which the data shall be collected, and the reporting and verification details, both the ISO 14064 and the GHG Protocol provide the discussed aspects of the GHG inventories. 

Based on the chosen methodology, the Organizational boundary of the inventory shall be determined, this boundary sets the approach which governs the path by which the emissions will be accounted for by the entities. Moreover, the Operational boundary which classifies the emissions into multiple scopes in order to ensure the highest levels of consistency and transparency.

ABCs of the GHG Inventories

The GHG inventory starts by identifying the organizational boundaries of the entity; this boundary utilizes two different approaches to deal with consolidated GHG emissions; the equity-share and the control approach. These approaches clarify the possible misconception that could easily occur when accounting emissions for diverse entities, beside organizational boundaries, the operational boundaries are identified by the GHG inventory. The emissions are classified by the operational boundaries into 3 different categories or as if they are commonly known “Scopes”, these scopes are listed as follows:

Scope 1: Direct GHG emissions, this scope contains four main categories with in, including:

• Stationary Combustion Emissions, which are the emissions produced from a direct combustion process of the various fuels used in the industries such as: Oil, gasoline, diesel, etc (biomass fuels are not included in scope, they are reported separately). The unique property of this category is that the combustion process is a stationary process, which means that the location of the process is fixed.
• Mobile Combustion Emissions, is the emissions that are associated with engines including internal and external combustion engines which are used in and not limited to: cars, buses, boats, ships, aircrafts, etc. The common thing between the emission sources within this category is that the combustion process is mobile which intensifies their impacts on nature.
• Fugitive Emissions, emissions resulting from intentional or unintentional releases of gasses from industrial activities, such gasses may escape from the joint points or weak spots of any system. Equipment leaks, venting, flaring, and evaporation losses are all considered as fugitive emissions under scope 1. 
• Process Emissions, which are the emissions released from physical or chemical processes during production activities. The main activities which are considered under the process emissions are: chemical production, cement production, metal production, waste treatment, etc.

Scope 2: Indirect GHG emissions, which are the emissions produced by the entity’s activities. However, the sources of these emissions are not owned nor controlled by the entity. Under scope 2 there are two main categories; Purchased Electricity and Purchased Steam (Heating), as stated before purchasing electricity and heating are associated with the activities conducted by any entity, yet the entity itself doesn’t own the electricity nor the steam generators, still they are responsible for the consuming behavior. So, scope 2 was created to measure the indirect emissions produced. 

Scope 3: Other indirect GHG emissions, this scope consists of 15 different categories that are associated with classifying and accounting the emissions sources outside the chain of value of any entity. 

Every-single category within these scopes has a unique emission accounting methodology which requires a certain kind of data that needs to be collected overtime, once the data is gathered the calculate the exact quantities of each one of the GHGs produced by the entity can be conducted and the carbon footprint of the entity can be obtained. 

Conclusion

A Greenhouse Gas (GHG) inventory is a comprehensive tool for calculating and documenting emissions associated with various activities of organizations, entities, or nations. By providing a clear picture of GHG emissions across different scopes, the inventory helps identify reduction opportunities, manage risks, and track performance over time. With methodologies such as ISO 14064 and the GHG Protocol offering structured guidelines, GHG inventories ensure consistency, transparency, and accuracy in emissions reporting, making them essential for any entity committed to sustainability and reducing its carbon footprint.