What the GHG Protocol is
The GHG Protocol (Greenhouse Gas Protocol) is a set of standards and guidance for companies and other organizations to measure and report their greenhouse gas emissions. It is the most widely used reference for corporate carbon footprints: it defines what is measured, how it is grouped and what is reported.
Who publishes it
It is developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). The standards are revised through public consultations: the scope 2 guidance, for example, had a public consultation between October 2025 and January 2026.
Which gases it covers
The Corporate Standard covers the seven Kyoto Protocol gases:
| Gas | Formula |
|---|---|
| Carbon dioxide | CO₂ |
| Methane | CH₄ |
| Nitrous oxide | N₂O |
| Hydrofluorocarbons | HFCs |
| Perfluorocarbons | PFCs |
| Sulphur hexafluoride | SF₆ |
| Nitrogen trifluoride | NF₃ |
To add them into a single figure, each gas is converted into CO₂ equivalent (CO₂e): the amount of CO₂ that would have the same warming effect.
The main standards
| Standard | Published | What it is for |
|---|---|---|
| Corporate Standard | 2004 | Building an organization's emissions inventory |
| Corporate Value Chain (Scope 3) Standard | 2011 | Measuring and reporting scope 3 across 15 categories |
| Scope 2 Guidance | 2015 | Calculating emissions from purchased energy |
The three scopes
- Scope 1: emissions from operations the company owns or controls. For example, natural gas and fuels burned at its sites and in its vehicles.
- Scope 2: emissions from generating the electricity, steam, heating or cooling the company buys and consumes.
- Scope 3: all other indirect emissions in the value chain, both upstream (suppliers) and downstream (customers). We cover it in what scope 3 is.
Which scope does it go in?
Pick the scope for each emission source. Every answer comes with an explanation.
Natural gas for heating a branch
Petrol for company cars
Diesel for the backup generator
Electricity bought for the stores
Waste collected from the offices
Flights for a business trip
Employees' daily commute
Paper and office equipment purchased
What is required and what is optional
Under the Corporate Standard, a company reporting its inventory must include all its scope 1 and scope 2 emissions. Scope 3 is optional under that standard. Those who report it can follow the Scope 3 Standard, which adds requirements to make those inventories consistent.
Scope 2: two methods for electricity
The Scope 2 Guidance defines two ways to calculate emissions from purchased electricity:
- Location-based method: reflects the average emissions intensity of the grids where energy consumption occurs.
- Market-based method: reflects emissions from the electricity the company has purposefully chosen. It uses factors from contractual instruments, such as renewable energy certificates, direct contracts or supplier-specific rates.
Companies with operations in markets where those instruments exist must report scope 2 both ways, labelling each result.
In CMT, each site's consumption is grouped into scopes 1, 2 and 3 following the GHG Protocol guidelines. See how CMT calculates the carbon footprint or continue with how to measure a company's carbon footprint.