GHG Protocol Explained: A Plain English Guide for Business Owners
What Is the GHG Protocol?
The GHG Protocol (Greenhouse Gas Protocol) is the most widely used international accounting framework for measuring and reporting greenhouse gas emissions. It was developed jointly by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD) and first published in 2001. It is the methodology behind almost every sustainability questionnaire, Carbon Passport, CSRD filing, and CDP disclosure you will encounter as a European supplier.
When a procurement questionnaire asks "which methodology did you use?" — the correct answer for any business using DeCarbonOPS is: "GHG Protocol Corporate Standard."
What Does the GHG Protocol Actually Define?
The GHG Protocol Corporate Standard defines:
- Three scopes — the boundary of what you report and who is responsible for which emissions
- Six greenhouse gases — which gases to include and how to convert them to CO2 equivalent
- Organisational boundary — how to account for subsidiaries, joint ventures, and leased assets
- Operational boundary — which activities fall within each scope
- Emission factors — the reference to use country or region-specific published factors (like DEFRA in the UK)
- Quality criteria — the principles of relevance, completeness, consistency, transparency, and accuracy
What Are the Three Scopes?
The three scopes are the most important concept in GHG reporting. Every questionnaire you receive will ask for figures in these three categories.
| Scope | Definition | Examples |
|---|---|---|
| Scope 1 | Direct emissions from sources you own or control | Natural gas combustion, diesel fleet, refrigerant leaks from your equipment |
| Scope 2 | Indirect emissions from purchased electricity, heat, steam, or cooling | Grid electricity at your offices, factories, or depots |
| Scope 3 | All other indirect emissions in your value chain | Business travel, employee commuting, supply chain, upstream fuel extraction, waste |
The GHG Protocol defines 15 specific Scope 3 categories. For most SME supplier questionnaires, four to five categories are material: Category 3 (well-to-tank upstream fuel), Category 5 (waste), Category 6 (business travel), and Category 7 (employee commuting).
What Are the Six Greenhouse Gases Covered?
The GHG Protocol follows the Kyoto Protocol list of greenhouse gases:
| Gas | Symbol | Global Warming Potential (100-year) | Main Business Source |
|---|---|---|---|
| Carbon dioxide | CO2 | 1 | Fuel combustion, electricity generation |
| Methane | CH4 | 28 | Natural gas (leaks), landfill waste, agriculture |
| Nitrous oxide | N2O | 273 | Combustion, fertiliser, wastewater |
| HFCs (group) | Various | 147–14,800 | Refrigerant gases in A/C and cold storage |
| PFCs (group) | Various | 7,390–12,200 | Semiconductor manufacturing, aluminium smelting |
| Sulphur hexafluoride | SF6 | 25,200 | Electrical switchgear insulation |
All are converted to CO2 equivalent using their GWP value. This is why the unit is tCO2e — see the full tCO2e explanation here.
What Is the Difference Between GHG Protocol and ISO 14064?
Both are recognised carbon accounting standards. Procurement questionnaires generally accept either.
| Feature | GHG Protocol Corporate Standard | ISO 14064-1 |
|---|---|---|
| Developer | WRI / WBCSD | ISO (international standards body) |
| Cost | Free to use | ISO certification has associated costs |
| Predominant use | Corporate disclosure, CSRD, CDP, SAP Ariba | Formal third-party verification processes |
| Scope definitions | Yes (three scopes, 15 Scope 3 categories) | Compatible with GHG Protocol, more prescriptive |
| Market acceptance | De facto global standard | Widely accepted, especially in formal audits |
For a first Carbon Passport and SME supplier questionnaires, the GHG Protocol Corporate Standard is the right choice. ISO 14064 becomes relevant if you pursue formal third-party verification.
What Is the Correct Methodology Statement When Completing a Questionnaire?
Most questionnaires include a free-text field asking you to describe your methodology. The standard statement for a DeCarbonOPS Carbon Passport is:
"GHG Protocol Corporate Standard (WRI/WBCSD). Emission factors: UK Government DEFRA Greenhouse Gas Reporting Conversion Factors 2023. Scope 1: natural gas, diesel, petrol, LPG, and refrigerant gases. Scope 2: location-based, national grid factors. Scope 3: Categories 3, 5, 6, and 7. Self-assessed."
DeCarbonOPS generates this statement automatically and includes it in your Carbon Passport. You can copy it into any questionnaire's methodology field.
How Does the GHG Protocol Relate to CSRD?
The EU's Corporate Sustainability Reporting Directive does not mandate a single accounting standard but requires reporting to be aligned with "internationally recognised" methodologies. The European Sustainability Reporting Standards (ESRS) — the technical rules under CSRD — recognise the GHG Protocol Corporate Standard as the primary accepted approach for greenhouse gas inventory.
This means: if your enterprise clients are CSRD compliant, they require GHG Protocol-compatible data from their suppliers. A Carbon Passport from DeCarbonOPS — built on GHG Protocol methodology with DEFRA 2023 factors — is exactly what they need to record in their Scope 3 supply chain inventory.
Frequently Asked Questions
What is the GHG Protocol?
The GHG Protocol (Greenhouse Gas Protocol) is the most widely used international framework for measuring and reporting greenhouse gas emissions. Developed by the World Resources Institute and World Business Council for Sustainable Development and first published in 2001, it defines the three scopes, six greenhouse gases, and calculation methodology used in virtually every supplier sustainability questionnaire, CSRD filing, and Carbon Passport.
What are the three GHG Protocol scopes?
Scope 1 covers direct emissions from sources you own or control — natural gas combustion, diesel fleet, refrigerant leaks. Scope 2 covers indirect emissions from purchased electricity, heat, or steam. Scope 3 covers all other indirect emissions in your value chain — business travel, employee commuting, upstream fuel extraction, waste, and supply chain. All three scopes must be reported on most enterprise supplier questionnaires.
What is the difference between the GHG Protocol and ISO 14064?
Both are recognised carbon accounting standards accepted by procurement questionnaires. The GHG Protocol Corporate Standard is the de facto global standard — free to use, widely understood, and the basis for CSRD, CDP, and most supplier questionnaires. ISO 14064 is an international standard body formalisation that is compatible with GHG Protocol principles and more commonly used in formal third-party verification contexts.
Which greenhouse gases does the GHG Protocol include?
The GHG Protocol covers the six Kyoto Protocol gases: carbon dioxide (CO2, GWP 1), methane (CH4, GWP 28), nitrous oxide (N2O, GWP 273), HFCs including refrigerant gases (GWP 147–14,800), PFCs (GWP 7,390–12,200), and sulphur hexafluoride SF6 (GWP 25,200). All are converted to CO2 equivalent using their 100-year Global Warming Potential values, producing the tCO2e figures that appear in every questionnaire.
How does the GHG Protocol relate to CSRD compliance?
The EU's Corporate Sustainability Reporting Directive requires large companies to report to the European Sustainability Reporting Standards (ESRS), which recognise the GHG Protocol Corporate Standard as the primary accepted methodology for greenhouse gas inventory. This means all CSRD-compliant enterprise clients require GHG Protocol-compatible data from their suppliers — exactly what a DeCarbonOPS Carbon Passport provides.
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