Scope 3 Primary Data Collection in Practice: What to Gather from Suppliers and How

According to SBTi, Scope 3 emissions reach an average of 11.4 times Scope 1 and 2 (own operations and purchased electricity) (CDP 2022 Global Supply Chain Report). For most companies, indirect emissions spread across the value chain represent the majority of total emissions, and reducing Scope 1 and 2 alone falls far short of achieving decarbonization targets. Yet few companies have a clear answer to the practical question of what to collect from suppliers and how. This article organizes the practical steps for primary data collection, drawing on GHG Protocol and Ministry of Environment guidance.

Why Primary Data Is Required

In December 2022, the GHG Protocol issued specialized guidance for collecting GHG data from suppliers when companies build Scope 3 GHG inventories. That guidance covers not only Scope 3 inventories based on the Corporate Value Chain (Scope 3) Accounting and Reporting Standard, but also product lifecycle GHG inventories, systematizing primary data collection procedures that avoid reliance on industry averages and estimates.

Scope 3 calculations using secondary data (industry averages and emission factors) are convenient in terms of cost and time, but have inherent accuracy limitations. The GHG Protocol's accounting and reporting standard requires data quality to be assessed against five indicators — technological representativeness, temporal representativeness, geographical representativeness, completeness, and reliability — and common emission factor databases cannot be said to satisfy all of these. Primary data collection matters not only to meet this quality requirement, but also because it makes a decisive difference in whether reduction efforts are reflected in calculated values. Even if a supplier genuinely improves energy efficiency, that achievement will not appear in the company's Scope 3 figures as long as secondary data continues to be used.

On the regulatory disclosure side, the importance of primary data collection is growing year by year. The TCFD and ISSB (International Sustainability Standards Board) have moved to require Scope 3 disclosure, rapidly accelerating demands for emissions data sharing across supply chains. In Japan, the SSBJ (Sustainability Standards Board of Japan) published Japan's sustainability disclosure standards aligned with ISSB on March 5, 2025, bringing mandatory Scope 3 disclosure for listed companies into view. The GHG Protocol standard requires companies to disclose the proportion of emissions calculated using data obtained from suppliers and others, creating a structure where the share of primary data collection directly determines disclosure quality.

Who to Collect From — The Principle of Top Concentration

Requiring the same level of primary data from all suppliers is neither realistic nor efficient. The GHG Protocol's accounting guidance cites the example of coffee bean procurement — "10 out of 100 suppliers account for 85% of purchase volume" — and explains that collecting primary data from these top 10 suppliers can achieve an 85% improvement in accuracy on a purchase volume basis. The remaining 90 suppliers can be supplemented with secondary data and industry averages. By concentrating on a small number of high-impact suppliers, overall calculation accuracy can be significantly improved.

AstraZeneca is a leading example of translating this principle into actual procurement strategy. The company requires suppliers covering 95% of spend across Purchased Goods and Services and Capital Goods to set SBTs (Science-Based Targets) by FY2025. For upstream transportation and business travel suppliers, the target is 50% of spend, and as of end-2023, the company had already conducted decarbonization engagement with 85% of top suppliers (approximately 3,500 companies). The framework AstraZeneca uses for prioritization is a matrix of spend and emission category, concentrating limited resources by engaging suppliers in high-spend, high-emission categories first.

Companies considering SBTi target submission must include Scope 3 reductions in near- and mid-term science-based targets when Scope 3 represents 40% or more of total emissions. Furthermore, supplier engagement targets must be achieved within five years of the submission date, making engagement design that accounts for target submission timing essential.

What to Collect — Data Items by Category

Scope 3 consists of 15 categories, but for manufacturers, Category 1 (Purchased Goods and Services) and Category 4 (Upstream Transportation and Distribution) carry particularly high priority.

The minimum accounting boundary for Category 1 is cradle-to-gate emissions — all upstream emissions from extraction, manufacturing, and transportation of purchased goods and services. The ideal data to request from suppliers is product-level GHG emission intensity (tCO2e per product or tCO2e/kg), but when this is difficult to obtain, it can be calculated from actual fuel consumption, electricity consumption, and production volume during the manufacturing stage. The seven target gases are CO2, CH4, N2O, HFCs, PFCs, SF6, and NF3; collecting emissions unified in tCO2e (tonnes of CO2 equivalent) facilitates internal aggregation and disclosure compliance.

For Category 4 upstream transportation, when fuel consumption data is available from transport operators, the fuel-based method is preferred. The GHG Protocol explicitly states that the fuel-based method provides higher CO2 calculation accuracy than the distance-based method, because there is a direct correspondence between fuel consumption and emissions. When fuel data is unavailable, the distance-based method — estimated from the product of transport distance and load factor — is used.

How Deep to Go — Tier Structure and Cascade Design

The Ministry of Environment's "Guide to Calculating Supply Chain Emissions Using Primary Data (v1.0)" prescribes a multi-level cascade structure: Tier 1 → Tier 2 → Tier 3. Tier 1 is defined as direct trading partners, Tier 2 as Tier 1's procurement partners, and Tier 3 as further upstream, with each layer collecting data from its direct trading partners and transmitting it upstream. Filling the entire value chain with primary data up to the furthest upstream is the ideal, but building all layers at once is not realistic.

The practical starting point is standardizing the request format for all Tier 1 suppliers. A standardized format makes it easier for Tier 1 to roll out the same template to Tier 2. This naturally facilitates cascading collection, and building out Tier 2 and Tier 3 spreads autonomously as a de facto obligation arising from transactions with large companies.

The GHG Protocol standard requires disclosure of the proportion of emissions calculated using data obtained from suppliers and others. Recording and managing collection rates alongside data quality scores is key to determining the accuracy of future disclosure compliance.

Handling SME Suppliers

Many SMEs in the value chain are either unaware of the need for GHG calculation or lack the expertise to carry it out. When large companies advance Scope 3 calculations, such unawareness among supply chain SMEs represents a practical barrier, and the Ministry of Environment guide identifies determining the appropriate level of data requests as a major challenge in supply chain compliance.

While Scope 3 disclosure carries few direct legal obligations for SMEs, it is increasingly required as a trading condition by large companies, and situations where it is closely tied to continuing business relationships are beginning to emerge. Guiding SMEs toward calculation tools and free resources is an effective countermeasure. The Ministry of Environment's calculation tool (v1.0) is available to suppliers and comes in a format that can be handed over directly as a request template. SBTi also provides a simplified validation route for SMEs, and directing suppliers to the free tools from the SME Climate Hub for setting targets based on Scope 1 and 2 alone can significantly lower the barrier to getting started.

Note that suppliers included in SBTi's supplier engagement targets are required to set science-based targets for at minimum Scope 1 and 2, and if a supplier's Scope 3 accounts for 40% or more of total emissions, additional Scope 3 target setting is required. Communicating this requirement at the request stage prevents rework in later processes. An approach that provides calculation support and demonstrates the mutual benefits of joint reduction — rather than applying pressure through trading conditions — encourages voluntary participation from suppliers.

Implications for Corporate Planning and Procurement

Start by creating a matrix of top annual procurement spend overlaid with Scope 3 categories (particularly Categories 1 and 4), and identify the top 20% of suppliers with high spend and high emissions. Next, design the request format while referencing GHG Protocol's supplier engagement guidance and the Ministry of Environment guide (v1.0). The four basic request items are fuel consumption, electricity consumption, production volume, and transportation fuel volume (or transport distance); product-level GHG emission intensity is prioritized when available.

Companies considering SBTi target submission must achieve supplier engagement targets within five years of the submission date. Incorporating SBTi requirements into the engagement design phase reduces the workload for future disclosure compliance.

Reference Fact Cards