Scope 3 Emissions: How to Collect Data from Your Supply Chain

For most companies, Scope 3 emissions dwarf everything else. On average, supply chain emissions account for 70–90% of a company's total carbon footprint. Yet most sustainability reports still treat them as an afterthought.

That is changing fast. CSRD requires Scope 3 disclosure. So does the GHG Protocol's corporate standard. And your largest customers are increasingly asking for it as part of procurement qualification.

Understanding the Three Scopes

Before diving into Scope 3 specifically, it helps to be clear on what the three scopes mean:

• Scope 1 — Direct emissions from sources you own or control (your company's boilers, vehicles, on-site processes)
• Scope 2 — Indirect emissions from purchased electricity, heat, or steam
• Scope 3 — Everything else: purchased goods and services, employee commuting, business travel, product use, end-of-life treatment

Scope 3 is further split into 15 categories, ranging from upstream purchased goods (Category 1) to downstream product use (Category 11) and investments (Category 15).

The Data Problem

The challenge with Scope 3 is that the emissions happen outside your organisation. You cannot measure them directly — you need data from your suppliers, logistics providers, and customers.

The two main approaches are:

1. Spend-based estimation Use your financial spend with a supplier and multiply it by an emissions factor (kg CO₂e per £ spent in that sector). This is fast and requires no supplier data, but accuracy is low.

2. Activity-based calculation Collect actual activity data from suppliers — tonnes of materials, kilometres shipped, kilowatt-hours consumed — and apply more precise emissions factors. Higher accuracy, but requires supplier engagement.

Most companies start with spend-based, then move key suppliers to activity-based over time.

A Practical Supplier Engagement Process

Here is a workflow that works for companies with 20–500 suppliers:

Step 1: Tier your suppliers

Not all suppliers are equal. Rank them by:

• Annual spend (proxy for emission significance)
• Sector emissions intensity (manufacturing vs. services emit very differently)
• Strategic importance

Focus your engagement effort on the top 20–30 suppliers, who typically represent 80%+ of your Scope 3 emissions.

Step 2: Send a simple data request

Do not send a 40-page questionnaire. Ask for:

• Total energy consumption (kWh/year, split electricity vs. gas)
• Scope 1 and 2 emissions if already calculated
• Any existing carbon reporting (CDP, GHG Protocol, etc.)

A one-page email request with a simple spreadsheet template gets far higher response rates than complex forms.

Step 3: Use fallbacks for non-responders

For suppliers who do not respond (expect 40–60% non-response initially):

• Use industry-average emission factors from sources like the UK DESNZ factors, EXIOBASE, or EcoInvent
• Apply spend-based estimates using EEIO databases
• Flag these as estimated in your report with a note on data quality

Step 4: Improve year-on-year

The first year is always the hardest. Once you have a baseline:

• More suppliers will engage once they see the process is straightforward
• Your estimates improve as you replace spend-based with activity-based data
• You can set meaningful reduction targets with your key suppliers

How Transparabl Handles This

Transparabl includes a supplier data portal that lets you send automated data requests, track responses, and automatically apply the right calculation methodology — spend-based where you lack data, activity-based where you have it. The platform flags data quality issues and generates audit-ready documentation.

The result: a Scope 3 report that meets CSRD and GHG Protocol requirements without months of manual work.

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Want to see how Transparabl handles Scope 3 for your specific supply chain? Book a demo.