Last updated: May 30, 2026. The Greenhouse Gas Protocol, usually called the GHG Protocol, is the main global framework companies use to measure and report greenhouse gas emissions. It is not one single checklist. It is a suite of standards and guidance covering corporate inventories, Scope 2 purchased energy, Scope 3 value-chain emissions, products, projects, cities, policies, and now land-sector emissions and removals.
Short answer: most companies starting a greenhouse gas inventory should begin with the Corporate Accounting and Reporting Standard, apply the Scope 2 Guidance for purchased electricity, steam, heat, and cooling, and then decide which Scope 3 categories are relevant. The existing standards remain in effect while GHG Protocol updates its corporate suite. In January 2026, GHG Protocol also published the Land Sector and Removals Standard, which takes effect on January 1, 2027 for companies with land-sector emissions or removals to account for.
What is the GHG Protocol?
The GHG Protocol provides standards and guidance for measuring greenhouse gas emissions. It is used by companies, governments, cities, financial institutions, reporting programs, and climate-disclosure frameworks because it gives a common accounting language for emissions.
For companies, the most important starting point is usually the Corporate Accounting and Reporting Standard. That standard provides requirements and guidance for preparing a corporate-level GHG inventory. The Corporate Standard covers the seven greenhouse gases under the Kyoto Protocol: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulphur hexafluoride, and nitrogen trifluoride.
The Corporate Standard is designed to help companies prepare a true and fair account of emissions, simplify inventory preparation, support emissions-management strategy, and improve consistency and transparency. It is program-neutral, meaning it can support many reporting frameworks, but it does not itself require companies to submit data to WRI or WBCSD.
Why companies use the GHG Protocol
Companies usually use the GHG Protocol because someone needs credible emissions data. The trigger might be a regulation, a customer request, a Microsoft or other supplier sustainability request, an investor questionnaire, a bank request, a sustainability report, a CSRD or ISSB-aligned disclosure, a target-setting exercise, or an internal decarbonization project.
The protocol matters because emissions calculations are easy to make look precise while still being weak. A useful inventory needs boundaries, activity data, emission factors, assumptions, units, source documents, review steps, and consistent methods year after year. Without that structure, the company may produce a number, but not one that finance, customers, auditors, or procurement teams can rely on.
The main GHG Protocol standards companies should know
The GHG Protocol suite includes several standards and guidance documents. The right one depends on the question being answered.
Corporate Standard
The Corporate Standard is for a company-level GHG inventory. It helps define organizational boundaries, operational boundaries, base year, emissions scopes, calculation methods, and reporting principles. This is the backbone for most corporate emissions work.
Scope 2 Guidance
The Scope 2 Guidance standardizes how companies report emissions from purchased or acquired electricity, steam, heat, and cooling. It introduced important rules for market-based reporting and the use of energy contracts and instruments such as renewable energy certificates.
Companies following the Scope 2 Guidance often need to understand both location-based and market-based approaches, the quality of any contractual instruments, and how energy purchases should be disclosed transparently. GHG Protocol held a public consultation on Scope 2 Guidance updates from October 20, 2025 to January 31, 2026, but until GHG Protocol says otherwise, the existing standards and guidance remain in effect.
Corporate Value Chain (Scope 3) Standard
The Scope 3 Standard helps companies account for emissions outside their own operations, both upstream and downstream. It covers 15 categories of Scope 3 emissions, including purchased goods and services, capital goods, fuel-and-energy-related activities, transportation, waste, business travel, employee commuting, leased assets, use of sold products, end-of-life treatment, franchises, and investments.
Scope 3 is often where supplier requests become difficult. A company may need data from suppliers to prepare its own Scope 3 inventory, while a supplier may need to calculate emissions to answer a customer questionnaire or service-level request. The right answer is rarely just a generic emissions total; it depends on the category, boundary, data quality, and customer requirement.
Product Standard and Project Protocol
The Product Standard is used to understand life-cycle emissions for a product or service. The Project Protocol is used for quantifying emissions reductions from mitigation projects. These are different from a corporate inventory. A company should not use a corporate footprint method as if it automatically proves product-level or project-level emissions claims.
Land Sector and Removals Standard
In January 2026, GHG Protocol published the Land Sector and Removals Standard. It is designed for companies that need to account for land management, land-use change, carbon removals with storage in land or geologic carbon pools, biogenic products, and technological carbon dioxide removals. It takes effect on January 1, 2027, and the accompanying guidance is expected in 2026.
This will matter most for agriculture, forestry, food, apparel, bioenergy, land-intensive value chains, and companies making removals-related claims. For many service businesses, it may not be central, but it is still worth knowing that the GHG Protocol suite is expanding beyond the older corporate inventory documents.
How scopes 1, 2, and 3 work
The GHG Protocol organizes corporate emissions into three scopes:
- Scope 1: direct emissions from sources owned or controlled by the company, such as company vehicles, boilers, generators, process emissions, or refrigerant leaks.
- Scope 2: indirect emissions from purchased or acquired electricity, steam, heat, or cooling consumed by the company.
- Scope 3: other indirect emissions in the value chain, both upstream and downstream.
For many companies, Scope 1 and Scope 2 can be calculated relatively quickly if utility bills, fuel records, vehicle data, and facility information are available. Scope 3 is usually more judgement-heavy because the company may need procurement data, supplier information, travel records, spend data, logistics records, product-use assumptions, waste data, or investment data.
If you want a deeper explanation of the scopes themselves, see Keslio's guide to Scope 1, Scope 2, and Scope 3 emissions.
How to prepare a GHG Protocol inventory
A practical GHG Protocol project should be built around decisions and evidence, not only spreadsheet formulas. A typical process includes:
- confirming why the inventory is being prepared, such as reporting, customer response, target-setting, or internal management;
- choosing the organizational boundary, such as operational control, financial control, or equity share;
- defining the operational boundary across Scope 1, Scope 2, and Scope 3;
- setting the reporting period and base year;
- mapping facilities, entities, leased assets, vehicles, operations, products, and services;
- collecting activity data, such as kWh, fuel litres, refrigerant quantities, spend, travel distance, waste volumes, or supplier data;
- selecting emission factors from credible sources;
- documenting assumptions, exclusions, estimation methods, and data quality limitations;
- calculating emissions in carbon dioxide equivalent using appropriate global warming potentials;
- reviewing results for completeness, reasonableness, and consistency with prior years; and
- preparing a methodology note and evidence file that can support reporting, customer review, or assurance.
Why the inventory purpose matters
The same company may need different levels of detail depending on the use case. A first internal footprint might be enough to identify hotspots. A customer request may require a specific response template, service-level allocation, consultant letter, or supporting documentation. A formal disclosure may need stronger controls, audit trail, director review, and consistency with financial reporting.
This is especially important for supplier requests. If a customer asks for company-level Scope 1, Scope 2, and Scope 3 data, the supplier should not automatically build a product carbon footprint. If the customer asks for service-level accounting, the supplier may need allocation logic that links the corporate inventory to the service delivered to that customer. If the customer asks for independent assurance, advisory calculation support is not the same thing as assurance.
That is why Keslio usually starts by reviewing the requirement before quoting the calculation project. A focused supplier request support project can be narrower and faster than a broad ESG program.
What is changing in the GHG Protocol?
GHG Protocol is updating its corporate suite because corporate emissions reporting has changed significantly since the Corporate Standard, Scope 3 Standard, Scope 3 Calculation Guidance, and Scope 2 Guidance were published. The update process covers the Corporate Standard, Scope 2 Guidance, Scope 3 Standard, and supporting documents. It is intended to align the standards with current best practice, mandatory climate disclosure, science-based targets, net-zero commitments, and the need for clearer Scope 1, Scope 2, and Scope 3 accounting.
The important practical point is not to pause all emissions work until the updates are done. GHG Protocol states that the existing standards and guidance stay in effect until it communicates otherwise. Companies preparing inventories now should use the current standards, track the update process, and document choices clearly so future recalculations or method changes can be handled cleanly.
Common mistakes to avoid
- Starting with a final emissions number before defining the organizational and operational boundaries.
- Using spend data everywhere when better activity data is available.
- Mixing entities, facilities, or reporting periods without documenting the boundary.
- Reporting Scope 2 without understanding location-based and market-based methods.
- Ignoring Scope 3 because the data is harder to collect.
- Using emission factors without recording source, geography, year, unit, or version.
- Making product, service, or customer-specific claims from a corporate inventory without allocation logic.
- Treating offsets, avoided emissions, or removals as if they reduce the gross inventory without checking the relevant guidance.
- Changing methods year to year without considering base-year recalculation or disclosure.
- Assuming GHG Protocol is a verification standard. It supports a verifiable inventory, but verification or assurance is a separate engagement.
What Keslio can help with
Keslio supports companies that need practical GHG emissions calculations, methodology documentation, and customer-ready emissions responses. That can include Scope 1 and Scope 2 calculations, Scope 3 screening, supplier data requests, service-level accounting, evidence packs, annual refreshes, and reporting support.
For suppliers responding to Microsoft or another buyer, the first step is to understand the actual wording of the request. A Microsoft supplier request, for example, may ask for total-company emissions, service-level accounting, Scope 3 categories, methodology documentation, a consultant letter, or an independent assurance route. Keslio can review that type of request through its Microsoft supplier GHG reporting support.
Need help applying the GHG Protocol?
If your team needs to calculate emissions for a sustainability report, customer request, supplier questionnaire, or internal climate plan, Keslio can help turn the GHG Protocol into a clear data request, calculation workbook, methodology note, and practical next-step plan.
