GHG Protocol: the emissions inventory guide for 2026

What the GHG Protocol is, and why it matters now

The GHG Protocol is the most widely adopted standard in the world for measuring greenhouse gas emissions. Created in 2001 by WRI and WBCSD, it became the basis of practically every regulatory framework: CDP, SBTi, CSRD, CVM 193 and IFRS S2 all require or reference a GHG Protocol inventory.

It is not optional. It is infrastructure.

If your company has to report emissions to any stakeholder, an investor, a regulator, a multinational client, the starting point is the GHG Protocol Corporate Standard.

The three documents that matter

The GHG Protocol is not one document. It is three that complement each other:

1. Corporate Standard, the base document. It sets the principles, the organizational boundaries and the requirements for Scopes 1 and 2. It is the starting point for any corporate inventory.

1. Scope 2 Guidance, which details how to calculate emissions from purchased energy. It introduced the market-based and location-based methods (more on that below).

1. Scope 3 Standard, which covers the 15 categories of indirect emissions in the value chain. It is the most complex and the one that raises the most questions.

In our experience the most common mistake is starting with the Scope 3 Standard without having the Corporate Standard properly implemented. The result: fragile data, an inconsistent baseline, and rework the following year.

Scope 1, direct emissions

These are the emissions coming out of sources your company controls: boiler combustion, an owned fleet, industrial processes and refrigerant leaks.

The logic is always the same: activity data × emission factor = tCO₂e.

The data comes from fuel invoices, air-conditioning maintenance records and production reports. The hard part is not the calculation, it is the collection. Data scattered across ERPs, spreadsheets and emails is the real bottleneck.

For calculation detail by source type, see our methodology.

Scope 2, purchased energy

Indirect emissions from the electricity, steam or heat your company consumes. The Scope 2 Guidance requires two calculations:

Location-based, using the average factor of the grid in your region. It reflects the reality of the grid where you operate. In Brazil, the SIN factor varies month by month (published by MCTI).

Market-based, reflecting your energy purchasing choices. If you have a solar PPA or I-RECs, this method shows the benefit. Without a specific contract, the residual grid factor is used.

Both are mandatory. Reporting only one is non-compliance.

In practice many companies report location-based because it is simpler, and ignore market-based. If you buy renewable energy and do not calculate market-based, you are throwing away the contractual benefit in your report.

Scope 3, the value chain

This is where the complexity lives, and where most of the emissions live. For service companies, Scope 3 is usually 80-90% of the total. For industry, 50-70%.

There are 15 categories, split into upstream (suppliers) and downstream (clients):

Upstream: (1) purchased goods and services, (2) capital goods, (3) fuel and energy not included in S1/S2, (4) upstream transport, (5) waste, (6) business travel, (7) employee commuting, (8) leased assets.

Downstream: (9) downstream transport, (10) processing of sold products, (11) use of sold products, (12) end-of-life of products, (13) downstream leased assets, (14) franchises, (15) investments.

You do not have to calculate all of them. The GHG Protocol requires a materiality analysis: focus on the categories that hold the largest share of emissions and where you have influence.

For a detailed guide to the 15 categories with examples by sector, see our article Scope 3: the 15 categories in practice.

Emission factors, where to find them

The emission factor is the coefficient that converts activity data (litres of diesel, kWh of electricity) into tCO₂e. The quality of the factor determines the quality of the inventory.

Source hierarchy (best to acceptable):

1. Primary data, direct measurement or supplier data. Always preferable.
2. MCTI, the official Brazilian factors. Mandatory for operations in Brazil.
3. Defra, the British reference, updated annually. Good category coverage.
4. EPA, the American factors. Useful for US operations.
5. IPCC, generic global factors. Last resort.

The Mangue Tech platform aggregates more than 60,000 emission factors from these sources and automatically applies the most specific one available for each activity. That removes the risk of using the wrong or an outdated factor.

Baseline recalculation, when it is required

The baseline is your inventory's reference year. All reduction progress is measured against it. The GHG Protocol requires recalculation when:

• Mergers or acquisitions change the organizational perimeter
• A change of methodology or of emission factors materially affects the result
• Significant errors are found in historical data

The rule of thumb: if the change affects 5% or more of the baseline's total emissions, recalculation is mandatory. Below 5% it is recommended but not required; document the decision.

In practice, recalculation is where many companies stumble. Without version control of data and factors, recalculating becomes a project of weeks. With the right platform, it is one click.

GHG Protocol vs ISO 14064

They are complementary, not competitors:

• GHG Protocol is the *how to calculate*: accounting methodology, categories, factors.
• ISO 14064 is the *management system*: traceability, quality control, and it is certifiable by third parties.

In practice most companies use the GHG Protocol as their methodology and seek ISO 14064 verification when an auditor or regulator requires formal certification. The two work together.

Where to start

1. Define the organizational boundary (operational control or equity share)
2. Collect activity data for Scopes 1 and 2
3. Choose the emission factors (prioritise MCTI for Brazil)
4. Calculate and document
5. Screen Scope 3 by materiality
6. Go deeper in the relevant categories

An inventory done well the first time avoids rework for years. The difference between "we did an inventory" and "our inventory is auditable" is in the quality of the input data and the traceability of every figure.