Emission Factor
An emission factor is a coefficient that converts an activity measurement — such as litres of fuel burned, kilowatt-hours of electricity consumed, or dollars spent on a commodity — into a quantity of greenhouse gas emissions, typically expressed in kilograms or tonnes of CO₂ equivalent (tCO₂e).
Emission factors are the mathematical bridge between what an organization does (activities) and the climate impact of those activities (emissions). They are published by government agencies (EPA, DEFRA, ADEME), international bodies (IPCC, IEA), and specialized databases (ecoinvent, EXIOBASE, GLEC).
There are several types of emission factors. Combustion factors convert fuel quantities (e.g., litres of diesel) into CO₂e. Grid factors convert electricity consumption (kWh) into emissions based on the regional energy mix. Spend-based factors convert monetary expenditure into emissions using economic input-output models. Product-specific factors capture lifecycle emissions for individual goods (e.g., kg CO₂e per tonne of steel).
Factor selection is one of the most consequential decisions in carbon accounting. Using a generic spend-based factor for a category that has activity-based data available can over- or under-estimate emissions by 50% or more. Good carbon accounting platforms match factors automatically based on activity type, geography, and time period, and allow auditors to inspect the matching logic.
Gravity's calculation engine maintains a curated library of emission factors and applies them through transparent, rules-based matching that creates full evidence trails linking every calculated emission to its source factor, database version, and methodology.
Frequently asked questions
What is an emission factor? +
An emission factor is a coefficient that converts an activity measurement (like litres of fuel or kWh of electricity) into greenhouse gas emissions expressed as CO₂ equivalent. Published by agencies like EPA and DEFRA, emission factors are the mathematical bridge between activities and their climate impact.
Where do emission factors come from? +
Emission factors are published by government agencies (EPA, DEFRA, ADEME), international organizations (IPCC, IEA), and lifecycle databases (ecoinvent, EXIOBASE). Some are region-specific (grid factors), while others are commodity-specific (fuel combustion factors) or economy-wide (spend-based factors).
Why does emission factor selection matter? +
Factor selection directly determines the accuracy of calculated emissions. Using a generic spend-based factor when activity-specific data is available can introduce errors of 50% or more. Transparent factor matching with auditable evidence trails ensures credible, defensible results.
Related terms
Carbon Accounting
Carbon accounting is the systematic process of measuring, recording, and reporting the greenhouse gas (GHG) emissions produced by an organization, product, or activity. It follows standardized methodologies — most commonly the GHG Protocol — to quantify emissions across Scope 1 (direct), Scope 2 (purchased energy), and Scope 3 (value chain) categories, producing an auditable inventory that underpins disclosure, reduction planning, and regulatory compliance.
tCO₂e (Tonnes of CO₂ Equivalent)
tCO₂e — tonnes of carbon dioxide equivalent — is the standard unit for expressing greenhouse gas emissions. It normalizes different greenhouse gases (methane, nitrous oxide, HFCs, etc.) to their equivalent warming impact relative to CO₂ using global warming potentials (GWPs), allowing them to be summed into a single comparable metric.
GHG Protocol
The GHG Protocol is the world's most widely used greenhouse gas accounting standard. Developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD), it provides frameworks for organizations, cities, and countries to measure and manage their emissions across three scopes.
Global Warming Potential (GWP)
Global warming potential (GWP) is a metric that compares the warming effect of a greenhouse gas relative to CO₂ over a specified time horizon, typically 100 years (GWP-100). It is published by the IPCC and used to convert different greenhouse gases into CO₂ equivalent for emissions inventories.
Spend-Based Method
The spend-based method estimates greenhouse gas emissions by multiplying procurement expenditure (in dollars or other currency) by economic emission factors that represent the average emissions intensity per unit of spend in a given sector. It is the most accessible Scope 3 estimation approach but also the least precise.