How to build a GHG inventory step by step

A greenhouse gas inventory is a structured list of a company's emissions for one year, organised by scope and backed by data and sources. This guide gives a practical order of work for a first inventory. Background: Scope 1, 2 and 3 emissions explained.

1. Set the boundaries

• Organisational boundary: which entities are in. Choose equity share, financial control or operational control; see organisational boundaries.
• Operational boundary: which emissions are in. Scope 1 and 2 at a minimum ("Companies shall separately account for and report on scopes 1 and 2 at a minimum"), plus the Scope 3 categories you will cover.
• Reporting year: usually your financial year.

2. Collect Scope 1 and 2 data

Guides: Scope 1 and Scope 2.

3. Screen Scope 3

The Scope 3 Standard requires companies to "account for all scope 3 emissions and disclose and justify any exclusions". Start with a rough screening of all 15 categories, then calculate the significant ones properly. See the 15 Scope 3 categories.

4. Choose emission factors

Use official factors for the country and year, matching your units and boundary. See what an emission factor is and how to choose one. Record the source, version and year of every factor.

5. Calculate and check

• Compare with last year and investigate large changes.
• Check units (kWh vs MWh, gross vs net calorific value, litres vs kg).
• Check for double counting: company cars in Scope 1 and business travel, upstream emissions inside Scope 1 factors, leased buildings in two places.
• Recalculate a sample by hand.

6. Document and report

A credible inventory states, at least:

• the organisational boundary and consolidation approach;
• Scope 1, Scope 2 (location-based and market-based if applicable) and the Scope 3 categories covered, in tonnes CO2e;
• the factor sources, GWP basis and any estimates;
• excluded sources and why;
• the base year and recalculation policy; see base year and recalculation.

7. Get it reviewed

Before publishing, have someone who did not prepare the numbers review them, and consider independent verification if customers, lenders or regulators will rely on the figures.

In LCALens

Inventories collect calculations by site and entity, track a data checklist for each category with owners and due dates, show Scope 2 both ways, and lock with a frozen snapshot once approved. Exports to PDF and Excel include the factor sources and file checksums.