How to Prepare a Greenhouse Gas Inventory

1. What is a greenhouse gas inventory?

A greenhouse gas (GHG) inventory identifies, quantifies and reports emissions associated with an organisation's activities. It provides a basis for understanding emission sources and planning reductions.

2. Five steps in the inventory process

Step 1 — Define the boundaries

Determine the facilities, operations and reporting period included in the organisational boundary. Define the reporting scope:

• Scope 1: direct emissions from owned or controlled sources, including relevant fuel combustion.
• Scope 2: indirect emissions from purchased energy, such as electricity or steam.
• Scope 3: other relevant value-chain emissions, such as purchased materials and transport, within the selected framework.

Step 2 — Collect activity data

Gather energy, fuel, materials and other relevant operating data. Establish a consistent method using the chosen reporting framework, such as the GHG Protocol or ISO 14064-1, and applicable sector guidance.

Step 3 — Calculate emissions

Use appropriate activity data, emission factors and global-warming potentials to express emissions in tonnes of CO₂ equivalent (tCO₂e). Record units, assumptions, factor sources and quality checks. Calculation software supports the process but does not replace data review.

Potential sources include IPCC guidance, EPA resources, the GHG Protocol and relevant national emission-factor publications. Select factors appropriate to the geography, activity and reporting year; an older electricity-grid factor should not automatically be used for a newer inventory.

Step 4 — Prepare the report

Present the boundary, methods, data, results and limitations in the format required by the regulator, customer or reporting framework. Keep supporting evidence traceable to the calculations.

Step 5 — Plan reductions

Identify significant sources and assess measures such as energy efficiency, process optimisation, suitable renewable energy and lower-emission technologies.

3. Important controls

• Check the accuracy, completeness and consistency of data.
• Apply the selected framework and document methodological choices.
• Use controlled calculation tools and review changes.
• Distinguish a reporting standard from a source of emission factors.

4. Benefits

A reliable inventory supports applicable legal and customer reporting, provides clearer environmental information to stakeholders and helps identify inefficient resource use. It can also support sustainability discussions with customers, partners and investors.

5. Common challenges

Businesses may encounter incomplete records, difficult Scope 3 data collection, limited specialist capacity and resource constraints. These challenges should be reflected in the project plan and data-quality review.

6. Practical solutions

Train data owners, define clear responsibilities, use suitable tools and obtain technical support where needed. Establishing the data-collection process early makes subsequent inventories more consistent and easier to maintain.

Related ITVC resources

• GHG inventories under ISO 14064-1
• Terms and definitions
• Sectors and facilities subject to inventory requirements
• GHG inventory reporting templates
• Calculating emissions from electricity consumption
• ITVC GHG inventory services