On this page
- What Scope 1, 2 and 3 emissions mean
- The six ISO 14064-1 categories
- Mapping table between ISO categories and GHG Protocol scopes
- Where the two systems differ in practice
- A worked example for a Turkish manufacturer
- Reporting one inventory in both formats
- What changes with the joint ISO and GHG Protocol standard
Scope 1, 2 and 3 are the GHG Protocol's way of grouping a company's emissions. ISO 14064-1:2018 groups the same emissions into six categories instead. This article explains both systems, gives a line-by-line mapping table between ISO categories and the 15 Scope 3 categories, and shows how one inventory can be reported in both formats without double work.
What Scope 1, 2 and 3 emissions mean
Scope 1 emissions are direct emissions from sources a company owns or controls, such as boilers, furnaces, vehicles and refrigerant leaks. Scope 2 emissions come from the generation of purchased electricity, steam, heat and cooling. Scope 3 covers all other indirect emissions in the value chain, upstream and downstream, split into 15 categories.
The GHG Protocol Corporate Standard requires Scopes 1 and 2. The Scope 3 Standard, published in 2011, sets the rules for the value chain and asks companies to report all relevant categories and justify exclusions. Scope 2 is reported twice under the 2015 Scope 2 Guidance, once with the location-based method (average grid factors) and once with the market-based method (contracts, guarantees of origin and supplier factors).
The six ISO 14064-1 categories
The 2018 revision of ISO 14064-1 replaced the 2006 edition's split into direct, energy indirect and other indirect emissions with six categories. The aim was to make indirect emissions easier to classify by the type of activity behind them.
- Category 1. Direct GHG emissions and removals.
- Category 2. Indirect GHG emissions from imported energy.
- Category 3. Indirect GHG emissions from transportation.
- Category 4. Indirect GHG emissions from products used by the organisation.
- Category 5. Indirect GHG emissions associated with the use of products from the organisation.
- Category 6. Indirect GHG emissions from other sources.
Categories 1 and 2 must always be quantified. For categories 3 to 6, the organisation sets criteria for significance (for example size, influence, access to data and accuracy), quantifies the significant sources and explains what it left out. Annex B of the standard gives examples of what belongs in each category.
Mapping table between ISO categories and GHG Protocol scopes
The two standards bodies have not published an official crosswalk. The table below reflects the examples in ISO 14064-1 Annex B and the way verifiers commonly accept the mapping. Where practice varies, we say so.
| GHG Protocol scope or Scope 3 category | ISO 14064-1:2018 category | Notes |
|---|---|---|
| Scope 1, direct emissions | Category 1 | ISO also includes removals in category 1 |
| Scope 2, purchased electricity, steam, heat, cooling | Category 2 | Covers combustion at the generator only |
| Scope 3 cat. 1, purchased goods and services | Category 4 | Services such as cleaning or consulting also sit here |
| Scope 3 cat. 2, capital goods | Category 4 | |
| Scope 3 cat. 3, fuel and energy related activities | Category 4 | Upstream fuel supply chains and grid losses, some organisations show grid losses under category 2 |
| Scope 3 cat. 4, upstream transportation and distribution | Category 3 | |
| Scope 3 cat. 5, waste generated in operations | Category 4 | ISO treats waste disposal as a service the organisation uses |
| Scope 3 cat. 6, business travel | Category 3 | Hotel stays are sometimes placed in category 4 |
| Scope 3 cat. 7, employee commuting | Category 3 | |
| Scope 3 cat. 8, upstream leased assets | Category 4 | |
| Scope 3 cat. 9, downstream transportation and distribution | Category 3 | |
| Scope 3 cat. 10, processing of sold products | Category 5 | |
| Scope 3 cat. 11, use of sold products | Category 5 | Often the largest category for energy-using products |
| Scope 3 cat. 12, end-of-life treatment of sold products | Category 5 | |
| Scope 3 cat. 13, downstream leased assets | Category 5 | |
| Scope 3 cat. 14, franchises | Category 5 or 6 | Practice varies, state your choice |
| Scope 3 cat. 15, investments | Category 5 or 6 | Practice varies, state your choice |
| No direct equivalent | Category 3 | Client and visitor transport, which ISO lists explicitly |
The pattern is easy to remember. Category 3 collects every kind of transport. Category 4 collects what you buy and use, including energy supply chains and waste services. Category 5 collects what happens to what you sell.
Where the two systems differ in practice
What is mandatory
Under the GHG Protocol, Scopes 1 and 2 are required and Scope 3 is formally optional in the Corporate Standard, though most buyers, SBTi and CSRD now expect it. ISO 14064-1 requires categories 1 and 2 and every significant indirect source in categories 3 to 6. In effect, both push you to cover the material value chain emissions, but ISO makes the significance assessment an explicit, documented step that a verifier will test.
Electricity
The GHG Protocol requires dual reporting of Scope 2. ISO 14064-1 deals with electricity in a dedicated annex and allows contractual instruments when they meet quality conditions. If you hold YEK-G guarantees of origin in Turkey or I-RECs, show the location-based figure and the market-based figure side by side and state which one feeds your total. The GHG Protocol is revising its Scope 2 rules (a public consultation closed on 31 January 2026), so the quality criteria for certificates may change.
Removals and biogenic carbon
ISO 14064-1 quantifies removals within category 1, for example carbon stored in owned forests. The 2004 Corporate Standard does not include removals in the scopes, and the GHG Protocol handles them in separate land sector and removals guidance. Both standards ask you to report biogenic CO2 from burning biomass separately from fossil emissions.
Gas-level detail
ISO 14064-1 asks for direct emissions to be reported by gas (CO2, CH4, N2O, NF3, SF6 and the HFC and PFC groups) in tCO2e. The GHG Protocol asks for the same seven gases. Keeping gas-level data in your workbook from the start avoids rework when a verifier or customer asks for it.
A worked example for a Turkish manufacturer
The figures below are hypothetical, for a mid-sized metal products plant with one site, to show how the same numbers appear in each format. Electricity uses the location-based method.
| Source | tCO2e | GHG Protocol | ISO 14064-1 |
|---|---|---|---|
| Natural gas in furnaces and boilers | 8,400 | Scope 1 | Category 1 |
| Diesel in forklifts and refrigerant leaks | 200 | Scope 1 | Category 1 |
| Grid electricity | 6,200 | Scope 2 | Category 2 |
| Purchased steel coil and coatings | 41,000 | Scope 3 cat. 1 | Category 4 |
| New press line | 1,800 | Scope 3 cat. 2 | Category 4 |
| Upstream fuel and grid losses | 2,900 | Scope 3 cat. 3 | Category 4 |
| Waste to recovery and landfill | 400 | Scope 3 cat. 5 | Category 4 |
| Inbound road freight | 3,100 | Scope 3 cat. 4 | Category 3 |
| Business travel and employee commuting | 770 | Scope 3 cat. 6 and 7 | Category 3 |
| Outbound freight to EU customers | 2,300 | Scope 3 cat. 9 | Category 3 |
| End of life of sold products | 1,700 | Scope 3 cat. 12 | Category 5 |
In GHG Protocol terms the plant reports Scope 1 of 8,600 t, Scope 2 of 6,200 t and Scope 3 of 53,970 t, a total of 68,770 tCO2e. In ISO terms it reports category 1 at 8,600 t, category 2 at 6,200 t, category 3 at 6,170 t, category 4 at 46,100 t and category 5 at 1,700 t. The total is identical. Only the grouping changes.
The example also shows why Scope 3 matters for a supplier. Purchased steel is about 60% of the total. An EU customer asking for this plant's data will care far more about the steel supplier's footprint than about the forklifts.
Reporting one inventory in both formats
The practical answer is to tag each emission source twice in the calculation workbook, once with its ISO category and once with its scope and Scope 3 category. Totals are then a pivot, not a second calculation.
- Build the source list at the level of fuel, meter, material or route, not at the level of scope.
- Assign each source an ISO category and a GHG Protocol scope and category, using a mapping you document once.
- Record the significance decision for each indirect source, which ISO requires and which also serves as your Scope 3 relevance test.
- Produce the ISO 14064-1 GHG report for verification and a GHG Protocol summary for customers, CDP and CSRD data requests.
This is how we set up inventories in our corporate carbon footprint and ISO 14064-1 consultancy work. Suppliers facing value chain requests from EU companies may also find our note on what suppliers must report after the CSRD Omnibus useful.
What changes with the joint ISO and GHG Protocol standard
In September 2025, ISO and the GHG Protocol announced a partnership to harmonise their GHG accounting standards. The plan published in July 2026 merges the Corporate Standard, Scope 2 Guidance and Scope 3 Standard with ISO 14064-1 into one consolidated corporate standard. A public consultation is planned for the second quarter of 2027 and publication for the fourth quarter of 2028.
Until then, the current editions apply. ISO 14064-1:2018 remains the basis for verification, and the 2004, 2011 and 2015 GHG Protocol documents remain the basis for scope reporting. An inventory that keeps source-level data, documents its mapping and records every factor and GWP version will be straightforward to restate when the new standard arrives. For the broader service, including product footprints, see our carbon footprint consulting page.
Ekol Çevre engineering team
Environmental engineers and consultants based in İzmir, Ankara and Kocaeli.