Supplier-Specific Method
The supplier-specific method uses greenhouse gas emissions data provided directly by individual suppliers for the specific goods or services purchased. It is the most accurate Scope 3 calculation approach and sits at the top of the GHG Protocol's data quality hierarchy.
What is Supplier-Specific Method?
The supplier-specific method is the gold standard for Scope 3 emissions calculation. Instead of relying on industry-average emission factors (spend-based or activity-based), it uses actual emissions data from the specific supplier providing the specific product or service. This means the calculation reflects that particular supplier's energy mix, production processes, transport methods, and decarbonisation efforts.
In practice, supplier-specific data can take several forms: a product carbon footprint (PCF) provided by the supplier for the exact item purchased; a cradle-to-gate emission factor from the supplier's own lifecycle assessment; an allocation of the supplier's total corporate emissions to the goods you purchased (based on revenue or physical share); or an Environmental Product Declaration (EPD) for a specific material or product category.
The GHG Protocol Corporate Value Chain Standard places supplier-specific data at the top of its data quality hierarchy. The SBTi expects organisations to increase the proportion of supplier-specific data in their Scope 3 inventories over time, particularly for Category 1 (Purchased goods and services) where it is typically the largest emission source.
The challenge is obtaining the data. Most suppliers — especially small and medium-sized enterprises — do not yet measure their own carbon footprint, let alone provide product-level emission factors to customers. This is gradually changing as supply chain carbon reporting requirements cascade from large companies (subject to CSRD, ISSB, SBTi) to their suppliers. Supplier engagement programmes — requesting emissions data through questionnaires, CDP Supply Chain, or direct dialogue — are the primary mechanism for obtaining supplier-specific data.
A common intermediate step is the hybrid approach: use supplier-specific data for the largest suppliers (by spend or emissions) and fill the remainder with activity-based or spend-based estimates. Over time, as more suppliers provide data, the proportion of supplier-specific coverage increases and the overall Scope 3 accuracy improves.
Practical Examples
A construction company obtains EPDs (Environmental Product Declarations) from its top three steel suppliers, using the specific embodied carbon figure (in kgCO₂e per tonne) rather than industry-average steel factors — revealing significant differences in carbon intensity between suppliers.
A retailer runs a CDP Supply Chain programme with its 50 largest goods suppliers, collecting product-level carbon footprint data that replaces the spend-based estimates for 60% of its Scope 3 Category 1.
A technology company receives a cradle-to-gate carbon footprint from its cloud hosting provider, showing 0.0015 kgCO₂e per server-hour — which replaces the generic EEIO factor for "data processing services" and yields a materially different (and more accurate) result.
How Climatise Helps
Climatise supports ingestion of supplier-specific emission factors and EPDs alongside standard factors. When supplier data is available, the platform uses it in preference to generic factors, automatically tracking which proportion of your Scope 3 is calculated using supplier-specific versus estimated methods — supporting your data quality improvement journey.
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