ISO 14064-1 GHG Inventory — Methodology and Reporting Approach
Most organisations can produce a greenhouse gas number. Far fewer can produce one that survives an audit — a number with a defined boundary, a stated quantification approach, a documented significance test, and a GWP basis a verifier can trace. ISO 14064-1 is the standard that turns a footprint into a defensible inventory. Run yours in the ISO 14064-1 Inventory Calculator.
It is the procedural backbone beneath almost every credible organisational GHG claim, including carbon neutrality and net-zero programmes that depend on it for quantification.
ISO 14064-1:2018 specifies how to design, quantify, and report an organisation’s GHG inventory. It classifies emissions into six categories, requires a significance assessment for indirect sources, and mandates a transparent GHG report. It pairs with ISO 14064-3 for verification.
ISO 14064-1:2018 — Greenhouse gases — Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals — is a procedural standard, not an emission-factor source. It does not publish factors. It specifies the design, development, management, reporting, and verification of an organisation’s GHG inventory: how to draw boundaries, how to classify emissions, how to decide which indirect sources to include, and what the resulting report must contain. This page walks the inventory lifecycle stage by stage, the decisions a practitioner makes at each one, and how the standard maps onto the GHG Protocol most teams already know.
What ISO 14064-1 Is — and Where It Sits
ISO 14064-1 sits at the methodology and accounting layer. It assumes you will calculate emissions using recognised factors — from DEFRA, the IEA, or another source — and specifies the framework those calculations must sit inside: principles, boundaries, categories, a significance test, and a report structure. It is the procedural discipline around the arithmetic, not the arithmetic itself.
A defining property: the standard is GHG-programme neutral. ISO 14064-1 layers beneath any specific programme — a regulatory scheme, a disclosure framework, or a carbon-neutrality standard such as ISO 14068-1. Where a programme applies, its requirements are additional to ISO 14064-1, never a replacement for them. This is why the standard appears as the quantification basis cited inside so many other frameworks.
The 2018 revision
The second edition (ISO 14064-1:2018) cancelled and replaced the 2006 first edition. The change that matters most to practitioners: the old three-part model gave way to six emission categories, and “operational boundaries” became “reporting boundaries”. The revision expanded the treatment of indirect emissions across the value chain, added explicit guidance on biogenic carbon and emissions related to electricity, and aligned the standard more closely with the GHG Protocol Corporate Standard. The Scope 1/2/3 vocabulary remains in widespread use alongside the six categories.
The ISO 14064 family
| Part | Level | Purpose |
|---|---|---|
| ISO 14064-1:2018 | Organisation | Quantification and reporting of an organisation’s GHG inventory |
| ISO 14064-2:2019 | Project | Quantification, monitoring, and reporting of emission reductions or removal enhancements |
| ISO 14064-3:2019 | Assertion | Validation and verification of GHG statements — the audit standard |
The Five Principles
Every requirement in ISO 14064-1 traces back to five principles. They are the test a verifier applies when a specific rule does not settle a judgement call, and they underpin a “true and fair” GHG account.
Relevance
Select the sources, sinks, reservoirs, data, and methods appropriate to the needs of the intended users of the inventory.
Completeness
Include all relevant GHG emissions and removals within the chosen boundary; justify any exclusion.
Consistency
Use methods that enable meaningful comparison of the inventory over time and against the base year.
Accuracy
Reduce bias and uncertainty as far as is practical; record the confidence level of each dataset.
Transparency
Disclose enough information for an intended user to make decisions with reasonable confidence — including exclusions and the GWP basis.
A verifier values an honestly disclosed data gap or stated uncertainty over an unexplained claim of total coverage. An inventory that documents what was estimated, what was measured, and what was excluded — and why — is more defensible than one that presents a single confident number with no provenance.
Step 1 — Set the Organizational Boundary
The organizational boundary determines which facilities and operations belong to the reporting entity. ISO 14064-1 requires the organisation to consolidate facility-level emissions and removals using one of two approaches, applied consistently and documented in the report.
| Approach | What it consolidates | When it fits |
|---|---|---|
| Control (operational or financial) | 100% of emissions from operations the organisation controls | Most common; aligns with how operational decisions are actually made. See operational control. |
| Equity share | Emissions in proportion to the organisation’s ownership interest in each operation | Where reporting should reflect economic ownership rather than control — joint ventures, partial holdings |
The consolidation approach must be the same across the whole inventory and stable across reporting periods. Switching approach between years breaks the consistency principle and triggers a base-year consideration. Mixing approaches within a single inventory — control for some sites, equity share for others — is non-conformant.
Step 2 — The Six Emission Categories
The 2018 revision classifies all organisational emissions and removals into six categories. Category 1 is direct; Categories 2 through 6 are indirect, with the 2018 edition renaming the old “other indirect” bucket and providing explicit guidance for classifying indirect emissions across the value chain.
Category 1 — Direct
Emissions and removals from sources within the organisation’s boundary: fuel combustion in boilers and owned vehicles, process emissions, fugitive releases.
Category 2 — Imported energy
Indirect emissions from imported electricity, heat, steam, and cooling consumed by the organisation but generated elsewhere.
Category 3 — Transportation
Indirect emissions from transportation: business travel, employee commuting, upstream and downstream freight.
Category 4 — Products used
Indirect emissions from products the organisation uses: purchased goods and services, capital goods, waste, and other upstream sources.
Category 5 — Products from the org
Indirect emissions associated with the use and end-of-life of products sold by the organisation — the downstream value chain.
Category 6 — Other
Indirect emissions from any source not captured in Categories 2 to 5, determined by the organisation’s own classification process.
Mapping to GHG Protocol scopes
The six categories map cleanly onto the three GHG Protocol scopes, which is why most teams report under both vocabularies at once. The mapping matters because data collected for one framework largely satisfies the other.
| ISO 14064-1 category | GHG Protocol scope | Example |
|---|---|---|
| Category 1 — Direct | Scope 1 | Natural gas combustion in an owned boiler |
| Category 2 — Imported energy | Scope 2 | Purchased grid electricity |
| Categories 3, 4, 5, 6 — Indirect | Scope 3 | Business travel, purchased goods, sold-product use, waste |
For the underlying quantification at each category, the same factor-based methods apply as elsewhere on the site — for example, the natural gas combustion methodology for a Category 1 source, or the Scope 2 electricity methodology for Category 2.
Step 3 — Reporting Boundary and the Significance Assessment
The reporting boundary is the organizational boundary plus the significant indirect emissions caused by the organisation’s activities. Category 1 and Category 2 are always included. For Categories 3 through 6, ISO 14064-1 requires a documented process to decide which indirect sources are significant enough to include — this is the assessment that prevents both arbitrary omission and uncontrolled scope creep.
Significance criteria
The organisation must define its significance criteria in advance, based on the intended use of the inventory. The standard points to a set of considerations:
- Magnitude — the estimated size of the emissions from the source.
- Influence — the organisation’s ability to reduce or affect those emissions.
- Risk and opportunity — exposure tied to the source, including regulatory and reputational risk.
- Data access and accuracy — whether the source can be quantified with acceptable confidence.
- Stakeholder and buyer requirements — what intended users and customers expect to see.
- Sector guidance — any applicable sector-specific expectations.
Justifying exclusions
If an indirect source meets the significance criteria, it must be quantified and reported. If a significant source is excluded, the exclusion must be justified in the GHG report. Defining significance criteria narrowly to engineer a smaller boundary — then not disclosing it — breaks both the completeness and transparency principles and will not survive verification.
Categories 3 to 6 also require attention to double counting: the same emission must not be reported twice across categories. The classification process and the significance assessment together fix which source sits in which category, once.
Step 4 — Quantify Emissions and Removals
Gases and GWP basis
ISO 14064-1 requires quantification of the seven Kyoto greenhouse gases — CO₂, CH₄, N₂O, NF₃, SF₆, PFCs, and HFCs — converted to a common CO₂e basis using stated global warming potential values. The standard does not mandate a specific GWP set, but it requires the source of the GWP values to be stated in the report. The current default for corporate inventories is IPCC AR6 GWP-100.
One basis governs one inventory total — AR5 and AR6 values must not be mixed within a single inventory. Where factors drawn from DEFRA carry AR5 GWP-100 internally, that basis is part of the factor’s definition and should be documented as such rather than converted. State the GWP source explicitly in the report; an unstated basis is a transparency failure.
Biogenic CO₂
A 2018-revision requirement that is frequently missed: biogenic CO₂ emissions must be quantified and reported separately from fossil emissions. The standard separates non-biogenic emissions, biogenic anthropogenic emissions, and biogenic non-anthropogenic emissions, so that land- and biomass-related flows are visible rather than folded into the fossil total. Direct removals are likewise quantified and reported in their own right.
Base year
The inventory is anchored to a base year — a defined historical period used as the reference for tracking change over time. The base year supports the consistency principle. ISO 14064-1 requires the organisation to set a policy for recalculating the base year when structural or methodological changes would otherwise make year-on-year comparison misleading.
Recalculate the base year when a change would materially distort the comparison: acquisitions or divestitures that shift the boundary, a change in consolidation approach, a change in quantification methodology or emission factors, or the discovery of significant errors. Define the recalculation threshold in advance and apply it consistently — recalculating selectively to flatter a trend is a consistency failure.
Step 5 — The GHG Report
The GHG report is the deliverable that makes the inventory usable and auditable. ISO 14064-1 specifies that reports be complete, consistent, accurate, relevant, transparent, and planned. The standard distinguishes mandatory content from recommended content.
Assembling the per-category and per-scope figures into one defensible inventory total — consistent boundaries, no double counting, and a clear audit trail — is its own procedure; the GHG inventory aggregation methodology documents that consolidation arithmetic.
| Mandatory content | Recommended content |
|---|---|
| Reporting organisation and responsible person; reporting period | GHG policies, strategies, and management procedures |
| Documentation of organizational and reporting boundaries, including significance criteria | GHG reduction initiatives and projects |
| Direct emissions (Category 1) quantified by gas; direct removals if applicable | Facility-level data and performance indicators or benchmarks |
| Indirect emissions by category, with significant sources quantified | Prior-year emissions and explanations of changes |
| Separate quantification of biogenic CO₂ | Offsets or GHG projects used outside the inventory total |
| Quantification approaches, with reasons for selection and any changes | GHG stored in reservoirs |
| GWP values used and their source; base year and recalculation policy | Uncertainty assessment detail |
| Explanation of any excluded significant source or sink | Reference to the verification statement, if verified |
If confidential data are withheld from the report, the withholding itself must be justified. A public statement claiming conformity with ISO 14064-1 commits the organisation to having met these reporting requirements.
Step 6 — Verification Under ISO 14064-3
ISO 14064-1 does not require verification — an organisation may choose it — but where a GHG statement is independently verified, the verification statement must be made available to intended users. Verification is conducted under ISO 14064-3, the family’s audit standard, by a competent and, for third-party assurance, independent verifier.
| Assurance level | What the verifier expresses | Rigour |
|---|---|---|
| Reasonable assurance | A positive opinion that the inventory is materially correct, based on a high level of evidence-gathering | Higher — more extensive testing of data and methods |
| Limited assurance | A conclusion that nothing has come to the verifier’s attention suggesting a material misstatement | Lower — narrower scope of testing |
The verifier assesses the GHG assertion — the emissions data, the quantification methodologies, the boundary and significance decisions, and the supporting evidence — against the requirements of ISO 14064-1. A material misstatement, or a significant source excluded without justification, is the kind of finding that prevents a clean statement.
ISO 14064-1 vs the GHG Protocol
The two frameworks are complementary, not competing — most organisations apply both. The distinction is one of character: the GHG Protocol is a flexible accounting framework with detailed calculation guidance; ISO 14064-1 is a procedural standard with formal conformity and verification structure.
| Dimension | ISO 14064-1:2018 | GHG Protocol Corporate Standard |
|---|---|---|
| Character | Procedural ISO standard with formal conformity | Flexible accounting framework |
| Classification | Six emission categories | Three scopes |
| Calculation guidance | Principles and requirements; programme-neutral | Detailed sector and activity calculation guidance |
| Verification | Formal pathway via ISO 14064-3 | Does not itself mandate third-party verification |
| Best for | Organisations seeking formal certification or audited conformity | Detailed corporate accounting across Scope 3 |
The data you collect under the GHG Protocol’s scope structure populates the ISO 14064-1 categories almost directly, and ISO 14064-1 supplies the conformity and verification discipline the Protocol leaves optional. Teams typically build the inventory once and report it under both vocabularies — six categories for ISO conformity, three scopes for stakeholder familiarity.
Worked Example — End-to-End Inventory
The following illustrates a complete ISO 14064-1 inventory build for a hypothetical organisation. All figures are illustrative inputs chosen to show the structure and the significance test — they are not MasterBrain values and do not represent any real entity.
| Step | Decision / input | Result |
|---|---|---|
| 1. Organizational boundary | Control approach; all operational sites consolidated | Boundary defined and documented |
| 2. Category 1 — Direct | Gas boilers + owned fleet, AR6 GWP-100 basis | 2,150 tCO₂e |
| 3. Category 2 — Imported energy | Purchased grid electricity, location-based | 1,420 tCO₂e |
| 4. Significance screen (Cat 3–6) | Criteria set in advance; sources screened by magnitude and data access | 4 significant sources identified |
| 5a. Cat 3 — Transportation | Business travel + commuting (significant) | 680 tCO₂e |
| 5b. Cat 4 — Products used | Purchased goods + waste (significant) | 3,910 tCO₂e |
| 5c. Cat 5 — Products from org | Sold-product use phase (significant) | 2,240 tCO₂e |
| 5d. Excluded source | Cat 6 minor source below significance threshold | Excluded; exclusion justified in report |
| 6. Biogenic CO₂ | Biomass heating fraction | 95 tCO₂e — reported separately |
| 7. Inventory total | Cat 1 + 2 + significant Cat 3–5 (biogenic excluded from fossil total) | 10,400 tCO₂e |
| 8. Report + verification | GHG report with mandatory content; ISO 14064-3 reasonable assurance | Conformant, verified inventory |
The total reconciles by construction: 2,150 + 1,420 + 680 + 3,910 + 2,240 = 10,400 tCO₂e across the included categories, with the 95 tCO₂e of biogenic CO₂ reported separately rather than added to the fossil total. The excluded Category 6 source is named and justified, satisfying the transparency principle even though it does not enter the number.
Edge Cases and Boundary Decisions
| Situation | Correct treatment |
|---|---|
| Leased assets | Classification depends on the consolidation approach. Under control, an asset you operate is Category 1/2; an asset you lease out is indirect. Document the logic. |
| Double counting across categories | Each emission sits in exactly one category. The classification process fixes placement once; a source cannot appear in both Cat 3 and Cat 4. |
| Biogenic vs fossil CO₂ | Quantify and report biogenic CO₂ separately from fossil. Never fold it into the fossil total — it is a distinct flow under the 2018 revision. |
| Change of consolidation approach | Triggers a base-year consideration. Re-state the base year so the comparison remains meaningful, per the recalculation policy. |
| Acquisition or divestiture mid-period | Apply the base-year recalculation policy if the structural change crosses the significance threshold; document the adjustment. |
| Market-based renewable electricity | Affects the Category 2 figure at the quantification stage. State the method (location-based vs market-based) consistently and disclose it. |
Conformity Checklist
An ISO 14064-1 inventory is conformant when every item below is satisfied and documented in the GHG report:
- The organizational boundary is defined using one consolidation approach, applied consistently.
- Category 1 and Category 2 emissions are fully quantified.
- Significance criteria for Categories 3–6 are defined in advance and documented.
- Every significant indirect source is quantified; every excluded significant source is justified.
- The seven Kyoto gases are quantified and converted to CO₂e on a single stated GWP basis.
- The GWP source is stated; AR5 and AR6 are not mixed within the total.
- Biogenic CO₂ is quantified and reported separately from fossil emissions.
- A base year is set with a documented recalculation policy.
- The GHG report contains all mandatory content and is complete, consistent, accurate, relevant, and transparent.
- If verified, the verification is conducted under ISO 14064-3 and the statement is made available to intended users.
Error Traps
| Error | Consequence | How to avoid |
|---|---|---|
| Mixing control and equity-share consolidation across sites | Non-conformant boundary; inconsistent total | Choose one approach and apply it across the whole inventory |
| Setting significance criteria after seeing the data | Criteria engineered to exclude inconvenient sources | Define significance criteria in advance, based on intended use |
| Excluding a significant indirect source without disclosure | Breaks completeness and transparency; verification finding | Quantify significant sources, or justify any exclusion in the report |
| Folding biogenic CO₂ into the fossil total | Misstates the fossil figure; 2018-revision non-conformance | Quantify and report biogenic CO₂ separately |
| Mixing AR5 and AR6 GWP values in one total | Internally inconsistent inventory | One GWP basis per total; document DEFRA-sourced AR5 line items as such |
| Not stating the GWP source | Transparency failure; total cannot be reproduced | State the IPCC assessment report used for GWPs |
| Recalculating the base year selectively | Trend distortion; consistency failure | Apply the recalculation policy and threshold uniformly |
Frequently Asked Questions
ISO 14064-1:2018 specifies the principles and requirements for quantifying and reporting an organisation’s greenhouse gas inventory: how to set boundaries, classify emissions into six categories, run a significance assessment for indirect sources, quantify the seven Kyoto gases on a stated GWP basis, and produce a transparent GHG report. It is a procedural standard — it does not publish emission factors.
Category 1 covers direct emissions and removals. Category 2 covers indirect emissions from imported energy such as purchased electricity. Categories 3 to 6 cover indirect emissions from transportation, products used by the organisation, products from the organisation, and other sources respectively. The six-category model replaced the older three-part structure in the 2018 revision, though Scope 1/2/3 terminology remains in common use alongside it.
Category 1 corresponds to Scope 1 (direct), Category 2 to Scope 2 (imported energy), and Categories 3, 4, 5, and 6 together correspond to Scope 3 (all other indirect emissions across the value chain). Because the mapping is clean, data collected under one framework largely satisfies the other, which is why organisations commonly report under both vocabularies.
No. ISO 14064-1 allows an organisation to choose whether to have its inventory verified. Where verification is carried out, it is conducted under ISO 14064-3 — at either reasonable or limited assurance — and the verification statement must be made available to intended users. Many organisations pursue independent third-party verification because it provides the credibility stakeholders increasingly expect.
The GHG Protocol Corporate Standard is a flexible accounting framework with detailed calculation guidance and a three-scope structure; ISO 14064-1 is a procedural ISO standard with six categories, formal conformity requirements, and a verification pathway via ISO 14064-3. They are complementary — most organisations build one inventory and report it under both, using the GHG Protocol for calculation detail and ISO 14064-1 for conformity and audit discipline.
Biogenic CO₂ emissions must be quantified and reported separately from fossil emissions — a requirement introduced in the 2018 revision. The standard distinguishes non-biogenic, biogenic anthropogenic, and biogenic non-anthropogenic emissions so that biomass- and land-related flows remain visible rather than being absorbed into the fossil total.