Scope 3 supplier engagement: collecting primary carbon data
Your guide to unlocking supplier carbon data, from a GHGP-certified expert
Effective scope 3 supplier engagement comes down to three priorities: identifying the right suppliers, framing your request around your own sustainability goals, and making it a procurement function, not a sustainability side project. This guide covers the three-phase strategy Normative’s Climate Strategy Advisors use across customer programs, what to actually ask for, and what 90% scope 3 coverage looks like in practice.
If you are still working out which scope 3 categories are material for your company, start with our complete guide to Scope 3 emissions before returning here.
Primary vs. secondary data: why the distinction matters
The Greenhouse Gas Protocol (GHG Protocol) distinguishes two types of scope 3 data:
- Primary data: obtained directly from your value chain. This could be via a supplier’s own scope 1, 2 and 3 emissions from their sustainability report; a product carbon footprint (PCF) supported by a life cycle assessment (LCA); an Environmental Product Declaration (EPD); or material weight and transport data from invoices.
- Secondary data: spend-based estimates using industry-average emission factors (from databases like Exiobase) that are applied to your procurement spend. This is a valid starting point but not a sustainable long-term strategy for organizations.
Under the Corporate Sustainability Reporting Directive (CSRD), specifically European Sustainability Reporting Standard E1 (ESRS E1), in-scope companies must disclose what proportion of their scope 3 inventory is primary versus secondary. Meanwhile, the Science Based Targets initiative (SBTi) expects clear plans for how an organization intends to improve data quality over successive reporting cycles. Both frameworks push in the same direction: away from averages, towards supplier-specific data.
Why your scope 3 supply chain data lives within other companies
Your scope 3 supply chain data lives in other companies because, on average, 75% of most companies’ emissions are generated by suppliers, logistics partners, and customers, not by your own operations. In sectors like financial services and capital goods, that figure regularly exceeds 90%, according to CDP.
That means the data you need to make meaningful progress is not in your systems. It is in your suppliers’ manufacturing records, annual reports, logistics systems, and invoice data. The good news: you do not need data from every supplier. Focused engagement with your highest-impact suppliers will move the needle faster than broad, low-effort outreach to your entire supply base.
Why suppliers resist sharing carbon data
Suppliers resist sharing carbon data for a number of reasons: many haven’t measured their emissions at all, some worry about competitive exposure, and others are fielding the same request from dozens of trading partners and have deprioritized it.
As a result, when talking with our customers about the challenges they face in their supply chain engagement programs, we often hear that suppliers either do not engage, want to charge for information, or simply do not collect the data being requested. For companies purchasing thousands of unique product types, the challenge compounds, as there is also the issue of handling categorization, not just supplier engagement.
Smaller suppliers present a specific difficulty. They often lack the resources, tools, or expertise to measure and report emissions at all. Obtaining reliable data from them, particularly for service categories, is consistently cited as the primary barrier in structured supplier engagement programmes.
There is also a systemic friction that is easy to overlook: many suppliers are already being asked for the same environmental data by multiple trading partners. That reporting fatigue reduces their likelihood of responding to your request, regardless of how reasonable it is. Reducing the burden, through shared platforms, standardized formats, or consolidated supplier emissions surveys, directly improves response rates.
A three-phase scope 3 supplier engagement strategy
Increasing visibility and data quality throughout your supply chain does not happen overnight. There are key stages that businesses must focus on in order to build a resilient, effective approach for engaging suppliers. The most systematic approach across customer programmes follows three phases, moving from supplier prioritization through to structured outreach and leverage mechanisms. Here’s what you need to know about each phase.
Phase 1: Segmentation
Before any outreach, rank your suppliers by two dimensions:
- Their contribution to your emissions footprint
- Their strategic importance to your operations
If you have already run a spend-based scope 3 assessment, that baseline identifies the high-impact partners you should start with.
One useful lens at this stage is shadow carbon pricing. Applying a notional carbon price, for example £100 per tonne of CO2e, to your procurement spend changes the relative cost of suppliers dramatically. A supplier with a higher emissions rate becomes materially more expensive on a carbon-adjusted basis than a lower-carbon alternative, even if their invoice price is lower. That reframes supplier engagement as a financial risk conversation – this is what tends to get internal stakeholders to stand up and take notice.
Phase 2: Tiered engagement
Match your data request to the supplier’s materiality and their reporting capability:
- Top emitters and strategic suppliers: request entity-level scope 1, 2 and 3 data from their sustainability report, or a certified PCF/LCA
- Mid-tier suppliers: request activity data such as, material weights, transport distances, energy volumes
- Long tail: retain spend-based estimates and redirect effort to the tiers above
This is not meant to act as a permanent hierarchy. The goal is to move suppliers up the chain over successive reporting cycles as their capability and your relationship develops.
Phase 3: Create leverage
Three mechanisms consistently move suppliers from optional to engaged:
- Structured supplier emissions surveys and questionnaires that reduce the reporting burden
- Environmental, Social and Governance (ESG) requirements embedded in procurement contracts
- Internal carbon pricing that signals to your supply chain that carbon performance influences your sourcing decisions
Let’s take a look at some practical steps your business can take, within each of these key phases of improving engagement throughout its supply chain.
Six tips for scope 3 supplier engagement that actually work
These six approaches consistently produce results across supplier engagement programs at different stages of maturity, and are drawn from direct experience across our team of Climate Strategy Advisors at Normative.
1. Clearly articulate “why” and make it specific. Generic data requests get ignored. So frame your outreach around your organization’s sustainability targets, not regulatory compliance. Something like: “We’re committed to reducing our footprint by X% by X year. A significant portion of our scope 3 emissions comes from our supply chain, and to achieve that goal we need to understand the emissions associated with what we purchase from you.”
Specific, goal-connected requests like this get responses. As a by-product, some suppliers will even use the opportunity to proactively highlight lower-carbon alternatives you were not previously aware of.
2. Start small and test your approach. Engaging 10-20 high-impact suppliers first lets you refine your process – the outreach format, the data request, the follow-up cadence – before scaling to your wider supply base. This will allow you to identify roadblocks early, while they are still manageable.
3. Define your qualifying criteria before you collect anything. Decide in advance what data quality you will accept into your emissions inventory. Options include: alignment with the GHG Protocol, third-party verification of calculations, transparent methodology, scope 1 and 2 only as a starting point (the most reliable tier), or product-level data for specific categories.
Note: overly strict criteria will limit how much supplier data you can actually use. Make sure you balance this with your organization’s risk tolerance and reporting requirements.
Two red flags to watch out for in any supplier submission: zero emissions reported in a category that is typically material for that supplier type, and no disclosed calculation methodology. Both are signs the data will not survive audit scrutiny.
4. Meet low-maturity suppliers where they are. If a supplier has not measured their emissions, treat that as information, not failure. It tells you something important about where they are on their sustainability journey. Direct them to accessible tools and resources rather than demanding a PCF they cannot yet produce. As a guiding principle: “No data is a data point in itself.”
5. Use procurement policy as a signal. Give preference to suppliers who measure and disclose their emissions. Even communicating that carbon performance is a factor in sourcing decisions changes behaviour. The effectiveness scales with your purchasing power: a large buyer can make this a formal procurement condition; a smaller buyer can still signal that it matters.
6. Delegate to people who own the relationships. Supplier engagement programmes that produce results assign responsibility to category managers with existing supplier relationships, not a single sustainability team member. Some organizations even embed supplier carbon data collection into category managers’ quarterly or annual performance targets, which converts it from an optional task into an owned one.
What to actually ask suppliers for
The data type you request should match the supplier’s tier and what they can realistically provide.
| Supplier type | Ask for | Why it matters |
| Major raw material suppliers | PCF or LCA (certified) | Replaces spend-based calculation entirely; highest accuracy |
| Manufacturing partners | Entity-level scope 1, 2, 3 from sustainability report | Links their decarbonization progress directly to your calculations |
| Construction/materials suppliers | Environmental Product Declarations (EPDs) | Industry standard for concrete, steel, glass |
| Logistics partners | Mode of transport + tonne-kilometre data | Significant accuracy improvement for Category 4 |
| All invoiced suppliers | Material weight/volume | Material weight/volume |
As a practical timeline benchmark: if your near-term reduction target is 2030, your top 50 suppliers, typically covering more than half of Category 1 spend, should be providing verified data by 2027, allowing two reporting cycles to refine and validate before your target year.
Tools that remove the bottleneck
The most time-consuming part of supplier engagement is not the outreach, it is manually collecting, formatting, and importing what suppliers send back. Two integrations in Normative’s supply chain engagement platform remove that bottleneck.
Carbon Network allows suppliers to input PCF and EPD data directly into the Normative platform, removing the company as data middleman and eliminating the spreadsheet-and-email loop that stalls most programmes.
EcoVadis, for companies whose suppliers already report through EcoVadis, feeds verified supplier intensity data directly into Normative Scope 3 calculations, without requiring those suppliers to do additional reporting work.
Both are supported by Normative’s named Climate Strategy Advisors, who help customers define qualifying criteria, prioritize outreach, and interpret incoming supplier carbon data within their broader reporting context.
What it looks like in practice: Hitachi Rail
Hitachi Rail came to Normative with over 10,000 active suppliers and reported scope 3 figures of 10-13% of their actual emissions footprint. The two core challenges were managing transactional data at scale and ensuring accurate emission factor mapping across a highly complex, global supply chain.
By working with Normative’s platform and advisory team, they calculated scope 3 to account for over 90% of their total emissions, giving them, for the first time, a comprehensive picture of supplier-related emissions and the data needed to build targeted decarbonization strategies by supplier category.
The starting point was not perfect data. It was the decision to start.
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FAQs
Start with your highest-impact suppliers by spend and emissions exposure, frame the request around your own sustainability targets rather than regulatory requirements, and keep the initial ask specific and manageable. A category manager making a direct request through an existing relationship will consistently outperform an automated survey from an unfamiliar platform. Where resources allow, a short supplier workshop explaining what data you need, why, and how to collect it, yields significantly higher response rates than email alone.
No. According to the SBTi Corporate Near-Term Criteria, your scope 3 targets must collectively cover at least 67% of total scope 3 emissions. That threshold can be met through a combination of emission reduction targets and supplier or customer engagement targets. You can use spend-based estimates underpinned by secondary emission factors to quantify the emissions in scope of that target. Primary activity data from suppliers improves accuracy, but it is not a condition of target approval. CSRD requires disclosure of what proportion of your scope 3 is primary versus secondary data, not that you have achieved 100% primary coverage.
A product carbon footprint (PCF) quantifies the lifecycle greenhouse gas emissions of a specific product, typically supported by a third-party life cycle assessment (LCA). An Environmental Product Declaration (EPD) is a standardized document format for communicating that data, most common in construction and building materials such as concrete, steel, and glass. Both represent Tier 1, product-level data in the GHG Protocol hierarchy, and both are accepted by the Normative platform.
It happens, particularly from larger suppliers who treat LCA or PCF data as proprietary. For high-emitting strategic suppliers, the cost may be justified by the accuracy improvement it delivers. For others, check whether their published sustainability report contains entity-level scope 1, 2 and 3 data you can use instead. This is publicly available and sufficient for Tier 2 calculations.
Moving your top 10-20 suppliers from spend-based to activity or supplier-specific data is typically a one-to-two reporting cycle effort. In year one you can: identify priority suppliers, make contact, collect what they can provide. In year two you can move on to: incorporate into calculations, track whether their emission intensity is improving year-on-year, and deepen engagement with willing suppliers before scaling further.
Because spend-based estimates apply industry averages, and for certain categories, actual emissions are higher than the average suggests. When one of our customers switched to more accurate supplier activity data for Category 1, total reported emissions increased from 41,496 to 65,734 tonnes of CO2e. That is not a worsening performance; it is better accounting.
