Emissions are broken down into three categories by the Greenhouse Gas Protocol to better understand and the source of CO2 and other GHG emissions. It helps to categorize, calculate and account for these emissions.
These are all direct GHG emissions. Direct GHG emissions are emissions from sources that are owned or controlled by the reporting entity like company facilities or company vehicles.
Indirect GHG emissions from consumption of purchased electricity, heat, or steam.
These are other indirect emissions, such as the extraction and production of purchased materials and fuels, transport-related activities in vehicles not owned or controlled by the reporting entity, electricity-related activities not covered in Scope 2, outsourced activities, waste disposal, etc.
Because Scope 3 emissions are so extensive, they can be complex to measure and generally account for the largest amount of GHG for a company. Scope 3 GHG emissions can vary greatly between companies. Differences in production methods are a cause of this, but because it can be complicated and costly to measure scope 3 emissions, it often differs greatly in how extensively companies measure and report their scope 3 footprints.