Impact factors translate a unit of economic activity into an environmental impact (such as greenhouse gas emissions, fresh water consumption, etc).

Activities can be economic processes (such as steel manufacturing), products or product categories (such as footwear).

A note on Scopes

Scope 1, 2, and 3 emissions are categories defined by the Greenhouse Gas Protocol to help organizations account for their carbon footprint:

• Scope 1 emissions are direct emissions from sources an organization owns or controls (e.g. fuel burned on-site, company vehicles).
• Scope 2 emissions are indirect emissions from the generation of purchased electricity, steam, heating, or cooling.
• Scope 3 emissions are all other indirect emissions in a company’s value chain (e.g. emissions from suppliers, product use, travel, waste).

In industrial ecology we distinguish between direct and indirect multipliers:

• A direct multiplier captures the immediate emissions per unit of output for a given sector.
• An indirect multiplier accounts for upstream emissions from all inputs required to produce that output.

Conceptually, Scope 1 emissions are equivalent to the direct multiplier associated with the greenhouse gas emissions for a given activity. The indirect multiplier corresponds to the sum of the scope 2 & 3 emissions.