Where are Trace's emissions factors ('EFs') sourced from?
Trace has a database of thousands of emissions factors that cover both activity data inputs (kWh, Mwh, units, litres, km, kg etc) and spend data inputs.
Types of Emissions Factors
Emissions factors are used to convert your company's activities into greenhouse gas emissions. The two most common approaches are activity based and spend based emissions factors. Both are valid, but they serve different purposes and have different strengths and limitations.
-
Activity based emissions factors are more accurate but require better data
-
Spend based emissions factors are broader estimates that enable Scope 3 coverage
-
Both approaches are accepted under the GHG Protocol when used appropriately
-
Moving from spend based to activity based data is a normal part of improving your carbon inventory over time
Here is a side by side comparison of each type:
| Aspect | Activity based emissions factors | Spend based emissions factors |
|---|---|---|
| What they are based on | Physical measures of activity such as kWh of electricity, litres of fuel, kilometres travelled, tonnes of waste | Financial spend, typically dollars spent in a given category and year |
| Typical calculation | Activity data × emissions factor | Spend × emissions factor |
| Common examples | Electricity consumption, natural gas use, fuel combustion, distance based travel, waste by weight | Accommodation, professional services, general procurement, taxis, marketing spend |
| Where they are used | Scope 1, Scope 2, and parts of Scope 3 where quantity data exists | Mainly Scope 3 where activity data is not available |
| Raw data source | Metering, invoices, operational systems, supplier reports | Finance systems, general ledger, expense data |
| Accuracy | Generally higher and more representative of actual emissions | Lower and more variable, based on sector averages |
| Sensitivity to price changes | Not affected by inflation or price movements | Affected by inflation, exchange rates, and market prices |
| Stability over time | Typically more stable year to year | Can change noticeably when factors or economic datasets are updated |
| Audit and assurance | Easier to explain, test, and assure | More challenging to assure due to averaging and modelling assumptions |
| Best use case | Tracking performance, setting targets, demonstrating reductions | Scope 3 data where supplier data is unknown or impractical to source, filling data gaps |
| Improvement pathway | Remains preferred as data quality improves | Often replaced with activity based data over time |
Trace EF Sources
For activity data emissions factors, Trace prioritises reputable public sources such as government publications and academic studies. Very commonly we refer to the National Greenhouse Account Factors (Australian Government) and the Department for Environment, Food and Rural Affairs (UK Government) and the US Environmental Protective Agency (EPA).
Spend-based, Scope 3 emissions factors come from a mix of sources:
Australia
Australian factors are sourced from our data partner, Footprint Lab, under a license agreement. Footprint Lab's database is developed in partnership with the University of Sydney and UNSW, powered by cutting-edge computational models, including a proprietary version of the Environmentally Extended Input-Output (EEIO) analysis model.
Using data from the IELab system, Footprint Lab traces the environmental flows—such as energy use, emissions, and material waste—from production through to consumption, covering 506 ANZSIC classes and 164 countries. This approach enables them to offer detailed, science-driven environmental metrics for any product, service, or industry. IELab’s data production methodology is described in the peer-reviewed articles by Lenzen et al: (2017a), (2017b), (2014) (2013).
You can read Footprint Lab's FAQs here.
UK and USA
Spend based factors for the UK are sourced from DEFRA and US factors are from EPA.
Rest of World
When a location specific spend based emissions factor is not available, a proxy factor is used to ensure emissions are still estimated in a complete and consistent way. We choose proxy factors from a country with a similar energy and economic structure. This is common and expected in spend based carbon accounting and the GHG Protocol allows the use of proxies when primary data is unavailable.
Factor Selection by country
Emissions factors are selected based on relevance, quality, and availability. Where possible, Trace always uses local emissions factors. In some cases, particularly for Scope 3, suitable local data does not exist at the required level of detail.
To read more about our Geographical selection of EFs please read this article.
Record keeping and Audit trail
To learn more about our process for maintaining and updating our EF database, please read this article.
On our Pro and Enterprise Software plans, you'll be able to see where we sourced the emissions factors for your calculations in the Measure Dashboard. You can also download a full Audit Report showing the EF value, source and date.
To understand why emissions factors change and how that might affect your inventory, please read this article.