Scope 3 Category 1: How to Estimate Purchased Goods and Services Emissions
What Is Scope 3 Category 1?
Scope 3 Category 1 covers the greenhouse gas emissions embedded in everything your company purchases — raw materials, components, packaging, software licences, and third-party services. For a manufacturer, this often represents the single largest emissions category: the steel, plastic, chemicals, and electronics you buy before a product is made.
Unlike Scope 1 (your own combustion) and Scope 2 (your electricity), Category 1 emissions happen at your suppliers' sites — which makes them harder to measure but equally important to disclose under CSRD.
Who Actually Needs to Report Category 1?
Category 1 is mandatory under CSRD for large companies (250+ employees or EUR 40M+ turnover). For most SME suppliers, enterprise clients asking for Scope 3 data primarily want Categories 3, 5, 6, and 7 — not Category 1. However, if you are a manufacturer or distributor with significant purchased goods, you may receive specific requests for it.
The Three Methods for Category 1 Estimation
The GHG Protocol's Scope 3 guidance describes three approaches, listed from least to most accurate:
1. Spend-Based Method
Multiply your annual spend on each category by an emissions factor (kgCO2e per EUR spent).
Formula: Spend (EUR) x Spend-based EF (kgCO2e/EUR) / 1,000 = tCO2e
Emissions factors source: Environmentally Extended Input-Output (EEIO) databases. The EXIOBASE database provides EU-specific factors. Example factors:
| Spend category | Approximate EF (kgCO2e/EUR) |
|---|---|
| Steel products | 1.8–3.2 |
| Plastics | 2.1–4.0 |
| Electronics | 0.8–1.5 |
| Professional services | 0.2–0.5 |
| Packaging | 1.5–2.8 |
When to use it: When you have spend data but no physical quantity or supplier-specific data. Least accurate but fastest to calculate.
2. Average-Data Method
Multiply physical quantities purchased by an average industry emission factor per unit.
Formula: Quantity (kg or units) x Average EF (kgCO2e/unit) = kgCO2e / 1,000 = tCO2e
When to use it: When you know how much of each material you buy (in kg, litres, tonnes) but your suppliers cannot provide product-specific data.
3. Supplier-Specific Method
Use the actual emissions data your suppliers report for their products — typically a Product Carbon Footprint (PCF) from each key supplier.
When to use it: For your top 5–10 suppliers by spend and emissions impact. Most accurate but requires supplier engagement.
A Worked Example: Packaging Manufacturer
A company spends EUR 280,000 per year on cardboard packaging.
- Spend-based method: EUR 280,000 x 1.8 kgCO2e/EUR = 504,000 kgCO2e = 504 tCO2e
- Average-data method: 420 tonnes of cardboard x 800 kgCO2e/tonne = 336,000 kgCO2e = 336 tCO2e
The difference is 168 tCO2e — a 33% variance. This is typical. Always document which method you used.
What to Report
On a procurement questionnaire asking for Category 1 data, report:
- The method used (spend-based, average-data, or supplier-specific)
- The emissions factor source (EXIOBASE, ecoinvent, supplier PCF)
- The resulting tCO2e estimate
- The percentage of spend or purchase volume covered
If you genuinely cannot calculate Category 1, it is acceptable to state: "Category 1 not yet calculated. We are using the spend-based method and will include this in the next annual report." Transparency beats omission.
Frequently Asked Questions
What is Scope 3 Category 1?
Scope 3 Category 1 covers emissions from the extraction, production, and transportation of goods and services purchased by your organisation. It is typically the largest Scope 3 category for manufacturing and retail companies, often representing 50–80% of total corporate emissions.
What are the three methods for calculating Scope 3 Category 1?
The GHG Protocol defines three methods: (1) Spend-based — multiply spend in each category by an emission factor per £/€; (2) Average-data — multiply physical quantity by a product-level emission factor; (3) Supplier-specific — use actual emissions data reported by your suppliers. Supplier-specific is most accurate; spend-based is the practical starting point.
Where do I find emission factors for purchased goods?
DEFRA publishes spend-based emission factors in the supplementary tables of their annual conversion factors release. The US EPA also publishes EEIO (Environmentally-Extended Input-Output) factors. For EU-specific factors, the Exiobase database is the most comprehensive peer-reviewed source.
How accurate is the spend-based method for Category 1?
Spend-based estimates carry ±50–100% uncertainty, which is acceptable for initial materiality screening. They are not suitable for target-setting or science-based alignment without transitioning to average-data or supplier-specific data for your top 5–10 spending categories.
Does DeCarbonOPS calculate Scope 3 Category 1?
DeCarbonOPS currently calculates Scope 3 Categories 3 (upstream fuel emissions), 5 (waste), 6 (business travel), and 7 (commuting). Category 1 (purchased goods) requires spend data and sector-specific emission factors — a feature planned for future development. For now, you can add your Category 1 estimate manually in the report notes.
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