Emission factor

The coefficient that converts an activity — a kWh, a kilogram, a tonne-kilometre — into greenhouse gas emissions.

Almost every carbon figure is activity data multiplied by an emission factor. The activity is usually well known. The factor is where the judgement is.

Factors differ by source, by geography, by year, and by boundary. A grid factor for Türkiye is not one for Germany; a 2024 factor is not a 2019 one; a cradle-to-gate cotton factor is not a cradle-to-grave one.

Choosing a factor is therefore part of the result, not an implementation detail. A figure that does not record which factor it used, from which dataset and which year, cannot be reproduced — and a number nobody can reproduce is difficult to defend.

Global warming potential (GWP) The factor that converts a greenhouse gas into an equivalent quantity of CO₂, over a given time horizon.
Product Carbon Footprint (PCF) The greenhouse gases attributable to one unit of a product across a defined part of its life cycle.
Scope 2 Indirect emissions from the electricity, heat and steam a company buys.