Supplier engagement for Scope 3: how to collect supplier data

Supplier engagement is a structured programme for getting Scope 3 supplier data — and, over time, emission reductions — from the companies you buy from. A workable programme ranks suppliers by emissions, asks each tier for a different level of data, makes responding easy, and links good data to procurement decisions. Done this way, it replaces spend-based estimates with supplier-specific figures year by year.

What a supplier engagement programme is for

For most manufacturers, retailers and service firms, purchased goods and services (Scope 3 Category 1) and upstream transport make up a large share of the footprint. You cannot reduce those emissions yourself; your suppliers can. A supplier sustainability programme has three jobs:

• Better data: move key suppliers from spend-based estimates to their own measured emissions or product carbon footprints.
• Real reductions: encourage suppliers to set targets, switch to renewable electricity and improve processes, so your Scope 3 falls for real rather than on paper.
• Lower risk: know which suppliers are exposed to carbon pricing, CBAM or customer pressure before it becomes a sourcing problem.

A one-off spreadsheet sent to every supplier achieves none of these. A programme does, because it repeats every year, measures itself and gets better.

Step 1: prioritise by emissions, not by supplier count

Start with a hotspot view of your existing Scope 3 inventory. Rank suppliers by estimated emissions, show spend alongside, and look at which categories and countries dominate. A small group of suppliers usually accounts for most of Category 1, and they are where engagement pays off first. We cover the ranking and climate-scoring side in detail in Supplier analytics for Scope 3.

Add two further filters before you finalise the list:

• Strategic dependence — single-source or long-term suppliers where a joint project is realistic.
• Regulatory exposure — suppliers of CBAM goods (iron and steel, aluminium, cement, fertilisers, hydrogen, electricity), whose installation data you may need regardless of their share of your footprint.

Step 2: tier suppliers and set a different ask for each

Asking every supplier for everything produces low response rates and poor data. Tiering matches the ask to the supplier's importance and capacity.

Tier	Typical suppliers	What to ask for	Engagement
Tier 1	Largest emitters and strategic partners	Company Scope 1, 2 and relevant Scope 3; targets; product carbon footprints for what you buy	Named contact, joint reduction plans, regular reviews
Tier 2	Material but less critical suppliers	Company Scope 1 and 2, energy use, renewable share, revenue for allocation	Standard data request, reminders, guidance
Tier 3	Long tail	Nothing yet, or basic yes/no questions on measurement and targets	Awareness; covered by spend-based or average-data estimates

Review the tiers each year. A supplier that starts reporting well can move up; a supplier whose share of spend falls can move down.

Step 3: decide exactly what to collect

Vague requests return unusable answers. A supplier data template should ask for the number and the context needed to use it:

1. Reporting period and organisational boundary — which entities and sites the figures cover.
2. Scope 1 and Scope 2 emissions, with Scope 2 on both location-based and market-based methods where available.
3. Method and emission factors — the standard followed (GHG Protocol or ISO 14064-1) and the factor sources used.
4. Verification status — whether the figures were assured, by whom and to what level.
5. An allocation basis — total revenue or total production volume, so you can attribute a share of their emissions to your purchases.
6. Product-level data for Tier 1 — cradle-to-gate footprints per unit of the products you buy.
7. Targets and actions — reduction targets, whether they are validated, and renewable electricity plans.

Allocation deserves care. Revenue-based allocation (your spend divided by their revenue, times their emissions) is simple but blunt. Product footprints or physical allocation by tonnes are better where the supplier makes several products with very different intensities.

Step 4: use product carbon footprints and standard exchange formats

For the suppliers that matter most, company-level emissions are only a step. The goal is a product carbon footprint (PCF) for each item you buy, calculated consistently. Two references help:

• ISO 14067, the international standard for quantifying the carbon footprint of products. See our guide to product carbon footprints and ISO 14067.
• The PACT Methodology from the WBCSD-hosted Partnership for Carbon Transparency (which grew out of the earlier Pathfinder Framework). Version 3, released in April 2025, gives sector-agnostic rules for cradle-to-gate PCFs, and PACT also publishes technical specifications so footprints can be exchanged between systems in a common data format.

Asking Tier 1 suppliers for footprints that follow these rules makes their data comparable across suppliers and easier to verify. Check the PACT website for the current methodology and specification versions before you write them into a contract.

Step 5: make responding easy

Suppliers, especially smaller ones, often receive similar requests from many customers. Response rates rise when the request is short, clear and supported:

• Use one template per tier, with definitions and a worked example.
• Collect through a supplier portal rather than e-mail attachments, so submissions, files and comments stay in one place.
• Accept data the supplier has already prepared — a CDP response, a sustainability report or an existing PCF — rather than asking for it in a new format.
• Give a fixed annual window and send reminders on a calendar.
• Offer short training or office hours for suppliers measuring emissions for the first time.

Step 6: add incentives and make it part of procurement

Engagement that lives only in the sustainability team stalls. Build it into how you buy:

• Sourcing criteria: include emissions data, targets and data quality in supplier evaluation alongside price, quality and delivery.
• Contract clauses: require annual emissions data from Tier 1 and Tier 2 suppliers in new or renewed contracts.
• Recognition: preferred-supplier status, longer contracts or volume commitments for suppliers that reduce.
• Joint projects: co-funding energy audits, renewable power purchases or process changes with key suppliers.

Keep the burden proportionate. Pushing costly requirements onto small suppliers without support tends to produce poor data and resentment, not reductions.

Step 7: measure the programme itself

Track a few indicators every reporting year:

• Share of Category 1 emissions covered by supplier-specific data.
• Response rate by tier, and how many submissions passed review.
• Share of supplier emissions covered by reduction targets.
• Change in emission intensity of key suppliers against their own baselines.

The first indicator is the most telling: it shows how much of your Scope 3 now rests on real supplier data rather than averages.

How EKOTRACE helps

EKOTRACE runs supplier engagement in the same platform as your GHG inventory. You invite suppliers to a supplier portal, send tiered data requests on a collection calendar with automatic reminders, and receive company emissions, targets and product carbon footprints with supporting files attached. Each submission goes through maker-checker review before it becomes a supplier-specific factor in your Scope 3 calculation, and supplier climate scores show who is ready to partner. See Supplier engagement and GHG accounting for more.

Frequently asked questions

How do you collect emissions data from suppliers?

Prioritise suppliers by estimated emissions, send each tier a short, defined data request, and collect responses through a portal or standard template. Ask for the boundary, method, emission factors and verification status alongside the numbers, and review each submission before using it in your inventory.

Which suppliers should we engage first?

Start with the small group responsible for most of your estimated purchased-goods emissions, then add strategic suppliers and those selling goods covered by regulation such as CBAM. Spend alone is a poor guide, because emission intensity varies widely between sectors.

What if a supplier cannot provide emissions data?

Keep using spend-based or average-data estimates for that supplier and ask for simpler information this year, such as energy consumption and fuel types. Offer guidance, and raise the ask the following year.

Is supplier engagement required by regulation?

Few rules require it directly, but several frameworks ask for Scope 3 or value-chain disclosure — for example ESRS, IFRS S2 and, on a voluntary basis for India's top 250 listed companies, BRSR value-chain disclosures. Supplier engagement is how most companies make those disclosures credible.