A greenhouse gas inventory is the process of collecting activity data and applying emission factors to calculate the total greenhouse gases (converted into tonnes of CO₂ equivalent) emitted by an organisation or facility in a year. It is a legal obligation for listed facilities under Decree 06/2022/ND-CP on greenhouse gas mitigation and ozone layer protection, and the input data for every Net Zero plan.
Key takeaways
- Seven main greenhouse gases are converted into tCO₂e: CO₂, CH₄, N₂O, HFCs, PFCs, SF₆, NF₃.
- Common standards: ISO 14064-1 and the GHG Protocol; listed facilities must follow the technical guidance of the relevant line ministry.
- Six steps: boundaries → emission sources → activity data → factors → calculation → reporting and verification.
Who must conduct a greenhouse gas inventory?
Facilities on the mandatory inventory list issued by the Prime Minister (Decision 01/2022/QD-TTg, updated by Decision 13/2024/QD-TTg) must carry out periodic facility-level inventories under Decree 06/2022/ND-CP. Beyond the mandatory group, many businesses conduct voluntary inventories because of requirements from customers, banks or CBAM.
A six-step inventory guide
Step 1: Set the boundaries
Choose the operational control or equity share approach; list the sites, factories and offices within the boundary.
Step 2: Identify emission sources
Classify them by Scopes 1, 2 and 3: fuel combustion, vehicles, industrial processes, refrigerant leaks, purchased electricity and value chain sources.
Step 3: Collect activity data
Figures on consumption of fuel, electricity, materials, waste and so on, taken from invoices, meters and stock issue slips. Keep the original evidence for verification.
Step 4: Choose emission factors
Give priority to factors published by the competent authorities (such as the national grid emission factor), then IPCC factors or verified supplier-specific factors.
Step 5: Calculate and control quality
Emissions = activity data × emission factor × global warming potential (GWP). Cross-check unusual figures and assess uncertainty.
Step 6: Report and verify
Prepare the report using the prescribed template or in line with ISO 14064-1; to meet the needs of international customers, it should be verified by a third party.
Five common mistakes
| Mistake | Consequence |
|---|---|
| Missing refrigerant leaks and backup generators | Scope 1 is understated |
| Using an outdated grid emission factor | Scope 2 is inaccurate |
| Not keeping original evidence | The inventory cannot be verified |
| Changing boundaries from year to year | Trends cannot be compared |
| Manual data entry across multiple spreadsheets | Errors and poor traceability |
Frequently asked questions
How often should a greenhouse gas inventory be carried out?
Under Decree 06/2022/ND-CP, listed facilities carry out inventories periodically according to the prescribed cycle (every two years); voluntary reporters usually conduct an inventory every year to track progress.
How does ISO 14064-1 differ from the GHG Protocol?
The two are compatible in principle; ISO 14064-1 is a certifiable international standard, while the GHG Protocol is a widely used set of guidance referenced by many reporting frameworks and customers.
Can we do the inventory ourselves?
Yes, if you have trained staff; however, for the results to be accepted by customers and banks, they should be independently verified.
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