GHG Protocol: Greenhouse Gas Protocol

What It Is

The Greenhouse Gas Protocol (GHG Protocol) is the world's most widely used set of standards for measuring and managing greenhouse gas emissions. Developed through a partnership between the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD), the GHG Protocol provides the accounting framework that underpins virtually every other climate disclosure standard, target-setting initiative, and regulatory requirement.

The GHG Protocol includes several standards:

Corporate Standard (revised 2004) — the foundational standard for corporate-level GHG accounting, establishing the Scope 1, 2, and 3 framework. It covers how to set organizational boundaries, identify emission sources, collect data, calculate emissions, and report results.

Scope 2 Guidance (2015) — provides detailed methodology for accounting for indirect emissions from purchased electricity, including the dual-reporting requirement for both location-based and market-based methods.

Corporate Value Chain (Scope 3) Standard (2011) — extends the corporate standard to cover indirect emissions across the full value chain, organized into 15 upstream and downstream categories.

GHG Protocol for Cities — applies the same principles to city-level emissions accounting.

Product Standard — provides guidance for product-level lifecycle GHG accounting.

The GHG Protocol covers seven greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). Emissions are expressed in metric tons of CO2 equivalent (tCO2e) using global warming potentials.

Who Uses It

Essentially every organization that measures greenhouse gas emissions uses the GHG Protocol — either directly or through standards that reference it:

• Companies reporting under CSRD/ESRS — ESRS E1 references GHG Protocol methodology
• Companies setting SBTi targets — SBTi requires GHG Protocol-compliant inventories
• CDP respondents — CDP's questionnaire is structured around GHG Protocol scopes
• Companies subject to EPA GHG Reporting in the United States
• Companies reporting under SEC climate rules — the SEC rule references GHG Protocol
• ISSB reporters — IFRS S2 references GHG Protocol for emissions measurement
• Over 90% of Fortune 500 companies that report GHG emissions use GHG Protocol

Key Requirements

Scope 1 — Direct Emissions: Emissions from sources owned or controlled by the company: combustion of fuels in boilers, furnaces, and vehicles; process emissions from chemical or physical processing; fugitive emissions from refrigerant leaks, methane from coal mines, etc.

Scope 2 — Indirect Energy Emissions: Emissions from purchased electricity, steam, heating, and cooling consumed by the company. Must be reported using both location-based method (grid average factors) and market-based method (contractual instruments like RECs, PPAs, green tariffs).

Scope 3 — Value Chain Emissions (15 categories): Upstream: purchased goods and services, capital goods, fuel- and energy-related activities, upstream transportation, waste, business travel, employee commuting, upstream leased assets. Downstream: downstream transportation, processing of sold products, use of sold products, end-of-life treatment, downstream leased assets, franchises, investments.

Five Accounting Principles: Relevance, completeness, consistency, transparency, and accuracy. These principles require that the inventory provides a faithful representation of the company's GHG emissions.

How to Implement

Phase 1: Organizational Boundary (1-2 weeks) Choose the consolidation approach — equity share (report based on ownership percentage) or control (report 100% of emissions from controlled operations). Most companies use operational control.

Phase 2: Scope 1 and 2 (1-3 months) Identify all direct emission sources. Collect activity data (fuel consumption, electricity bills, refrigerant purchases). Apply appropriate emission factors (EPA, DEFRA, IEA, or local grid factors). Calculate both location-based and market-based Scope 2.

Phase 3: Scope 3 Screening (1-2 months) Screen all 15 categories for relevance. Use spend-based estimates for initial screening to identify material categories. Prioritize categories that are large (>5% of total), have reduction potential, or are required by stakeholders.

Phase 4: Scope 3 Detailed Calculation (2-6 months) For material categories, improve data quality — move from spend-based estimates toward activity-based or supplier-specific data. The GHG Protocol provides a data quality hierarchy and methodological options for each category.

Phase 5: Quality Management and Reporting Implement data quality procedures. Establish base year and recalculation policy. Report following GHG Protocol reporting requirements. Consider third-party verification.

Relationship to Other Frameworks

GHG Protocol is the foundation on which other frameworks build:

• SBTi requires GHG Protocol-compliant inventories for target validation
• CDP structures its questionnaire around GHG Protocol scopes
• ISSB IFRS S2 references GHG Protocol for emissions measurement
• ESRS E1 references GHG Protocol methodology
• ISO 14064 provides a conformance-oriented alternative to GHG Protocol, with substantial alignment
• TCFD Metrics & Targets pillar requires Scope 1, 2, and 3 disclosure per GHG Protocol

Why It Matters

GHG Protocol is the common language of corporate climate measurement. Without it, the entire architecture of climate disclosure — TCFD, ISSB, CSRD, CDP, SBTi — would lack a consistent measurement foundation. When a company reports Scope 1 emissions of 50,000 tCO2e, GHG Protocol is what makes that number comparable to another company's disclosure.

For companies, GHG Protocol is not optional — it's prerequisite. Every major climate disclosure standard and target-setting initiative either requires or references it. Building a robust, GHG Protocol-compliant emissions inventory is the first step in any climate strategy, and the quality of that inventory determines the credibility of everything that follows.

The current update process (GHG Protocol is considering revisions to the Corporate Standard and Scope 3 guidance) will address longstanding challenges including Scope 3 data quality, market-based accounting for grid decarbonization, and carbon removal accounting. Companies should monitor these developments as they may affect future inventory requirements.