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 defined activities and boundaries. It helps an organisation understand its emission sources and their scale so that it can plan reductions on a sound basis.

2. Five steps in preparing a GHG inventory

The process can be organised into five main steps:

Step 1: Define the inventory boundary

• Organisational boundary: determine which entities, sites, branches and activities are included and the consolidation approach.
• Under the GHG Protocol, emissions are grouped into three scopes:
  • Scope 1: direct emissions from sources owned or controlled by the organisation, such as fuel combustion at its facilities.
  • Scope 2: indirect emissions from purchased or acquired electricity, steam, heat and cooling.
  • Scope 3: other indirect value-chain emissions, such as relevant purchased materials, transport and product-related activities.

Step 2: Collect data

• Collect relevant energy, fuel, material, process and other activity data for the reporting period.
• Select the applicable methodology and requirements, such as GHG Protocol, ISO 14064-1 and relevant IPCC or sector guidance; these have different purposes and should not be treated as interchangeable.

Step 3: Calculate emissions

• Apply appropriate emission factors and calculation methods to activity data. Convert individual gases to CO₂e using the required global warming potentials when the factors are not already expressed in CO₂e.
• Use checked calculation tools or software with documented assumptions, units and quality controls. Software alone does not ensure an accurate inventory.

Emission-factor references: choose sources appropriate to the geography, reporting year, activity and reporting method, including:

IPCC — Intergovernmental Panel on Climate Change

EPA — U.S. Environmental Protection Agency

GHG Protocol

Vietnam’s emission-factor list under Decision 2626/QĐ-BTNMT

Vietnam’s 2021 grid CO₂ emission factor — a historical-year reference

Step 4: Report the results

• Compile the inventory results and supporting methodology.
• Prepare the report in the format required by the competent authority, selected reporting framework or customer contract. See: GHG inventory report template

The percentages belong to the original illustration, whose geography and year are not stated. They are not a current global or Vietnam emissions profile and must not be used as inventory emission factors.

Step 5: Develop a reduction strategy

• Analyse the inventory to identify the most significant sources and improvement opportunities.
• Assess measures such as energy efficiency, process optimisation, suitable renewable energy and lower-emission technologies.

3. Points to check

• Data quality: inaccurate or incomplete data can distort the results and the reduction strategy.
• Method consistency: follow the selected standard and applicable legal requirements. IPCC guidance, EPA resources, the GHG Protocol and ISO 14064-1 serve different functions; naming them does not by itself establish global recognition.
• Supporting technology: suitable software can reduce repetitive work and calculation errors when inputs, formulas and outputs are reviewed.

4. Benefits of a GHG inventory

A well-prepared inventory can provide several practical benefits:

• Compliance: support applicable statutory reporting and customer requirements.
• Credibility: transparent, supported information can strengthen confidence in the organisation’s environmental responsibility.
• Operational improvement: identify avoidable consumption, losses and process-improvement opportunities.
• Investment discussions: credible sustainability information can support dialogue with investors and partners, without guaranteeing investment.

5. Common challenges

Typical difficulties include:

• Data collection, especially information from suppliers and other Scope 3 activities.
• Limited specialist capacity in GHG accounting and calculation methods.
• The financial and staff resources needed for the agreed inventory scope.

6. Ways to address the challenges

• Train personnel in boundaries, data collection, calculation methods and quality checks.
• Use appropriate tools and data controls to reduce collection and calculation errors.
• Obtain suitable specialist support for the inventory’s technical and reporting requirements.

A GHG inventory supports sustainable development when its findings lead to practical action. Measuring, reviewing and reducing emissions can contribute to environmental goals and better business decisions.

Related articles

Organisational GHG inventories under ISO 14064-1

ISO 14064-1 terminology and definitions

Sectors and facilities required to prepare GHG inventories

GHG inventory report template

ISO 14067 consultancy

Calculating GHG emissions from electricity use

Vietnam’s emission-factor list under Decision 2626/QĐ-BTNMT

Vietnam’s 2021 grid CO₂ emission factor

Vietnam’s 2020 grid CO₂ emission factor

GHG inventory at LS Vina

GHG inventory at Taya Vietnam

GHG inventory at Bumjin Electronics Vina Co., Ltd.

GHG inventory at Vinacomin Machinery Manufacturing Joint Stock Company

GHG inventory at Chin Huei Plastic Industry Joint Stock Company

References

GHG Protocol — calculation guidance