Carbon footprint calculation is the inventorying and reporting of an organisation's greenhouse gas emissions in line with international standards. This calculation is the common foundation of sustainability reporting, SBTi (Science Based Targets) commitments, CDP responses, EcoVadis scoring and CBAM compliance. A correct carbon inventory is "root data" that feeds multiple obligations from the same dataset. In this article, we examine the Scope 1, 2 and 3 emission categories, the calculation methodology and frequently encountered errors within the framework of the GHG Protocol and the ISO 14064-1 standard.
The Three Core Categories of a Carbon Footprint
An organisation's greenhouse gas emissions are divided into three main categories according to their level of controllability and their source. This classification was first defined by the Greenhouse Gas Protocol and was subsequently integrated into the ISO 14064-1 standard.
| Category | Definition | Example Sources |
|---|---|---|
| Scope 1 (Direct) | Direct emissions released from sources owned or controlled by the organisation | Natural gas boilers, diesel generators, company vehicles, process emissions, refrigerant gas leaks |
| Scope 2 (Indirect Energy) | Indirect emissions arising from purchased electricity, steam, heating and cooling | Grid electricity, district heating, purchased steam |
| Scope 3 (Other Indirect) | All other emissions that occur in the organisation's value chain but are not under its direct control | Purchased goods/services, logistics, business travel, product use phase, waste disposal |
Scope 1: Direct Emissions
Scope 1 covers emissions released directly from facilities, equipment and vehicles under the organisation's financial or operational control. It is the most concrete and verifiable category to calculate.
Typical Scope 1 Sources
- Stationary combustion: Natural gas boilers, fuel-oil burners, coal furnaces
- Mobile combustion: Vehicles in the company fleet, generators, forklifts, construction machinery
- Process emissions: Calcination in cement clinker production, reduction in steel production, reaction CO2 in chemical processes
- Fugitive emissions: Refrigerant gas (HFC) leaks, natural gas line leaks, SF6 from electrical equipment
Calculation Approach
The typical formula is activity data × emission factor. For example, for a consumption of 1,000,000 m³ of natural gas:
1,000,000 m³ × 1.89 kg CO2e/m³ (IPCC emission factor) = 1,890 tonnes CO2e
Emission factors are taken from the IPCC 2006 Guidelines, IEA values or installation-specific measurement data. They may vary according to fuel type, the region of production and quality.
Scope 2: Indirect Energy Emissions
Scope 2 covers emissions arising from the generation of purchased electricity, steam or heat. The emission physically occurs at another facility (for example, a thermal power plant), but the economic obligation lies with the consuming organisation.
Two Calculation Approaches: Location-Based and Market-Based
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Location-Based: The average grid emission factor of the region of consumption is used. For Türkiye, TEDAŞ and TEİAŞ data are taken as the basis; the 2023 grid emission factor is approximately 0.45 kg CO2e/kWh.
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Market-Based: The contracted source of the electricity consumed (renewable, fossil, nuclear) is taken into account. If renewable electricity with I-REC or YEK-G certification is consumed, the emission factor of this energy may be considered 0.
Most reporting standards such as CDP, GRI, ESRS and SBTi require both approaches to be reported in parallel.
Scope 3: Value Chain Emissions
Scope 3 is the broadest, most complex and usually the largest emission category. Between 60 and 80 percent of a manufacturing company's total footprint can lie in Scope 3. The GHG Protocol defines Scope 3 emissions in 15 sub-categories.
Scope 3 Upstream Categories
- Category 1: Purchased goods and services
- Category 2: Capital goods
- Category 3: Fuel- and energy-related activities (not in Scope 1-2)
- Category 4: Upstream transportation and distribution
- Category 5: Waste generated in operations
- Category 6: Business travel
- Category 7: Employee commuting
- Category 8: Upstream leased assets
Scope 3 Downstream Categories
- Category 9: Downstream transportation and distribution
- Category 10: Processing of sold products
- Category 11: Use of sold products
- Category 12: End-of-life treatment of sold products
- Category 13: Downstream leased assets
- Category 14: Franchises
- Category 15: Investments
The success of Scope 3 depends on how early the supplier data collection infrastructure is established. Moving from survey-based data to supplier-specific measurement multiplies the quality of reporting.
Setting the Inventory Boundary: Operational and Financial Control
A carbon inventory begins with a clear boundary decision on which of the organisation's assets it covers. The GHG Protocol proposes two main boundary approaches:
Financial Control Approach
It includes the emissions of assets over whose financial policies the company has control. Generally, all subsidiaries in which more than 50 percent is held are included.
Operational Control Approach
It includes the emissions of assets over whose operational policies the company has control. This approach gives more consistent results in managed joint ventures.
Equity Share Approach
A share proportional to the equity holding in each subsidiary is taken. It is preferred more in financial institutions.
Practical Inventory Preparation: 6 Steps
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Defining the organisational boundary: The financial, operational or equity share approach is chosen; this choice remains fixed for the entire reporting period.
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Drawing the operational boundary: It is determined which Scope 1 and 2 sources are mandatorily included and which Scope 3 categories are deemed material and included.
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Collecting activity data: Facility-based fuel consumption, electricity bills, supplier surveys and logistics records are compiled.
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Assigning emission factors: Using IPCC, IEA, DEFRA or national inventory sources, the appropriate factor is matched to each activity.
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Calculation and verification: The activity × factor multiplication is performed; data consistency is tested through internal control.
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Independent verification: Within the scope of ISO 14064-3, verification is carried out at reasonable or limited assurance level by a TÜRKAK-accredited independent verifier.
Common Mistakes
- Changing the boundary decision year to year: If the same organisation is reported with a different control approach in different years, comparability is lost.
- Only location-based data in Scope 2: If renewable electricity contracts exist, the market-based calculation remains incomplete and the real reduction is not reflected.
- Neglecting Scope 3: If Scope 3 is dropped on the grounds that "there is no accurate data", the total inventory is understated and is not accepted under commitments such as SBTi.
- Failing to update emission factors: When there is an update in the IPCC or national inventory, annual reports must be revised.
- Skipping refrigerant gas leaks: In industrial cooling, HFC leaks have a marked impact on the inventory due to their very high GWP values.
Frequently Asked Questions
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Is a carbon footprint reported annually?
Yes. The standard reporting period is the calendar year, and the previous year's inventory is published in parallel with financial-year reporting. For listed companies, annual reporting also runs in sync with CSRD, GRI and CDP obligations.
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Is there a difference between ISO 14064-1 and the GHG Protocol?
The two standards largely complement each other. The GHG Protocol is the most widely used reference as a methodological guide. ISO 14064-1, on the other hand, is the standard for applying this methodology within management-system discipline for a corporate inventory. Organisations wishing to obtain independent verification generally produce ISO 14064-1-compliant reporting.
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Are only Scope 1 and 2 sufficient for an SBTi commitment?
No. SBTi requires a science-based target for Scope 3 as well from companies whose Scope 3 emissions exceed 40 percent of the total footprint. The road to SBTi therefore runs through establishing a full-scope Scope 3 inventory.
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Which investment is most effective for reducing a carbon footprint?
Although it varies by sector, energy efficiency investments, renewable electricity procurement and process optimisations form the trio that provides the fastest payback. Over the longer term, product design optimisation and the shift to low-carbon raw materials create the greatest structural impact.
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What is the difference between carbon neutral and net-zero?
Carbon neutral means offsetting emissions with voluntary carbon credits. Net-zero, on the other hand, means first reducing emissions to the maximum extent possible (generally above 90 percent) and then balancing the remaining unavoidable emissions with permanent removal methods (for example, nature-based solutions or direct air capture). SBTi supports only the net-zero approach.
