GHG Emissions Calculation Approaches

Definition

There are a variety of possible GHG Emissions Calculation Approaches that can be used by an entity in the process of calculating GHG emissions.. Emission calculation methodologies define the calculation formulas and necessary activity data and emission factors to determine total emissions from specified activities.

• Companies should use the most accurate calculation approach available to them and that is appropriate for their reporting context.
• Cities should select the most appropriate methodologies based on the purpose of their inventory, availability of data, and consistency with their country’s national inventory and/or other measurement and reporting programs in which they participate.

Possible Approaches

The IPCC guidelines (IPCC, 1996) refer to a hierarchy of calculation approaches and techniques ranging from the application of generic emission factors to direct monitoring:

• Direct measurement of GHG emissions by monitoring concentration and flow rate.
• Emissions may be calculated based on a mass balance or stoichiometric basis specific to a facility or process.
• GHG emissions estimated through the application of documented emission factors. These factors are calculated ratios relating GHG emissions to a proxy measure of activity at an emissions source.

In many cases, particularly when direct monitoring is either unavailable or prohibitively expensive, accurate emission data can be calculated from fuel use data. Even small users usually know both the amount of fuel consumed and have access to data on the carbon content of the fuel through default carbon content coefficients or through more accurate periodic fuel sampling.