Primary Data vs. Secondary Data: Definition, Differences and When Each Is Required in PCF Calculations

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Every Product Carbon Footprint (PCF) and Life Cycle Assessment (LCA) is built from two types of data: primary data — collected directly from actual production processes, facilities, or suppliers — and secondary data — drawn from verified databases, published emission factors, and industry averages. The balance between the two, and the quality of each, is one of the most consequential decisions in PCF methodology, affecting the accuracy, comparability, and regulatory defensibility of the result.

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Both ISO 14067 and the GHG Protocol Product Standard set explicit data quality requirements covering both primary and secondary data — making the choice not just a technical decision, but a compliance consideration for audit-ready CSRD and CBAM reporting.

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What is primary data?

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Primary data (also called foreground data or activity-specific data) is information collected directly from the specific processes, facilities, or supply chain partners being assessed. It represents actual, measured values for the system being modeled — not averages or estimates. In a PCF context, primary data includes:

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• Supplier-measured material emission factors: a steel supplier's actual CO₂e per tonne, based on their specific energy mix, production route, and raw material inputs — rather than an industry average
• Site-specific energy consumption: actual electricity and heat consumed per production run at a specific facility, based on metered data
• Process-specific waste and loss data: actual scrap rates and material losses in a specific production process
• Supplier-provided transport data: actual shipment distances, weights, and transport modes from a specific logistics partner

Primary data produces the most accurate PCF results because it reflects the actual conditions of the product's supply chain — not a statistical average that may or may not represent the real situation.

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What is secondary data?

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Secondary data (also called background data) is drawn from published sources — life cycle databases, verified industry emission factor libraries, national statistics, and scientific literature — rather than from direct measurement. It represents typical or average conditions for a given material, process, or activity and is used to fill gaps where primary data is not available.

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Common secondary data sources include life cycle databases such as ecoinvent, the European Life Cycle Database (ELCD), and commercially verified databases such as the sustamize CO₂e database. The key quality criteria for secondary data — as specified by ISO 14067 and the GHG Protocol — are accuracy, geographic and technological representativeness, completeness, timeliness, and transparency of the source.

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Primary vs. secondary data: key differences

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The main difference between primary and secondary data lies in their source, accuracy, collection effort, and scalability. Both play an important role in carbon footprint calculations and sustainability reporting, but they serve different purposes.

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Primary data is collected directly through measurements, production processes, or supplier-reported information. It reflects actual operating conditions and therefore offers the highest level of accuracy and specificity. However, collecting primary data can be time-consuming and resource-intensive, as it often requires direct supplier engagement or on-site measurements. This also limits its scalability, particularly when assessing large product portfolios or complex supply chains.

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Secondary data, on the other hand, comes from existing databases, published emission factors, and industry averages. While its accuracy depends on the quality, relevance, and representativeness of the underlying sources, secondary data is generally easier to access and significantly more scalable. It enables companies to assess thousands of materials and processes without collecting individual measurements for every data point.

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When it comes to regulatory compliance and audit readiness, both data types have distinct advantages. Under the Carbon Border Adjustment Mechanism (CBAM), verified actual emissions data can help companies avoid relying on potentially less favorable default values. Secondary data can support calculations where primary information is unavailable, subject to the applicable regulatory requirements.

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For audits and verification, primary data generally provides the strongest evidence when properly documented and verified. However, high-quality secondary data from reliable, transparent, and well-documented sources can also support credible and auditable carbon footprint calculations.

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Ultimately, combining primary and secondary data allows companies to balance accuracy, efficiency, and scalability while improving the reliability of their sustainability assessments.

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When primary data is required — and when secondary is sufficient

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For most cradle-to-gate PCF calculations and Scope 3 Category 1 inventories, a mix of primary and secondary data is both expected and acceptable. ISO 14067 and the GHG Protocol do not require primary data for every single input — they require that the overall data quality is sufficient for the intended purpose, with primary data prioritized where it materially affects the result.

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In practice, primary data is most critical for:

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• CBAM: using default (secondary) emission values is legally permitted but typically results in significantly higher certificate costs, since defaults are set conservatively. Verified actual (primary) emissions from the non-EU producer almost always produce lower embedded emission values.
• EU Battery Regulation: PCF declarations must be supported by verified data, with third-party verification. While secondary data can be used, critical inputs — cathode materials, cell energy consumption — benefit strongly from primary data.
• CSRD external assurance: auditors will scrutinize the data quality of Scope 3 Category 1 calculations; primary data from major suppliers significantly strengthens the audit trail.
• High-impact BoM positions: where a single material or component represents a large share of the total PCF, primary data from that supplier is disproportionately important for accuracy.

For lower-impact positions, secondary data from a verified, well-documented CO₂e database is an efficient and fully acceptable approach.

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Primary data collection in practice

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For procurement teams building Scope 3 supplier data programs, primary data collection typically involves structured data requests to key suppliers — asking for verified PCF values aligned with ISO 14067 or GHG Protocol methodology, supported by documentation of the calculation approach. The sustamizer® supports this workflow: suppliers can provide product-level CO₂e data that integrates directly with the buyer's PCF calculation, replacing secondary background data with verified primary values where they are available.

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Want to build PCFs that combine verified secondary data with primary supplier inputs?

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Explore our CO₂e database and PCF calculation tools, or contact our team to access the sustamizer® and manage primary and secondary data in one audit-ready workflow.

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