Scope 3 Emissions for SMEs: Which Categories Matter
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Scope 3 is the part of carbon accounting that covers everything beyond your direct operations and purchased energy — your supply chain, business travel, employee commuting, waste, and the use and disposal of your products. It is typically the largest share of a company’s total emissions, but also the hardest to measure.
If you have not yet calculated your Scope 1 and 2 emissions, start there. Our carbon accounting guide covers the fundamentals. This post is for SMEs that have Basic covered and are ready to tackle Scope 3, either because VSME Comprehensive requires it or because a counterparty has specifically asked.
When Scope 3 enters the picture
Scope 3 is not part of VSME Module Basic. You can produce a complete Basic report with only Scope 1 and 2. Scope 3 becomes relevant when:
- You move to VSME Comprehensive (which asks for Scope 3 categories where data is available)
- A large customer under CSRD asks you for product-level or supply-chain emissions data
- A bank asks for total carbon footprint including value chain
- You are setting science-based targets (SBTi requires Scope 3 if it exceeds 40% of total emissions)
If none of these apply, skip Scope 3 for now. Get Scope 1 and 2 right first.
The 15 Scope 3 categories
The GHG Protocol defines 15 categories of Scope 3 emissions, split into upstream (your supply chain) and downstream (your customers and product end-of-life). Not all apply to every business.
Upstream categories
| Category | What it covers | Typical relevance for SMEs |
|---|---|---|
| 1. Purchased goods & services | Emissions from producing everything you buy | High — usually the largest Scope 3 category |
| 2. Capital goods | Emissions from producing equipment and buildings you buy | Medium — relevant if you made major capital purchases |
| 3. Fuel & energy activities | Upstream emissions from your energy supply (beyond Scope 2) | Low — often small relative to other categories |
| 4. Upstream transportation | Emissions from inbound logistics | High for manufacturing and retail |
| 5. Waste generated in operations | Emissions from treating your waste | Medium — relevant for manufacturing |
| 6. Business travel | Flights, hotels, rental cars | High for consulting and services |
| 7. Employee commuting | Employees travelling to work | Medium — relevant for larger office-based SMEs |
| 8. Upstream leased assets | Emissions from assets you lease (if not in Scope 1/2) | Low — usually already covered |
Downstream categories
| Category | What it covers | Typical relevance for SMEs |
|---|---|---|
| 9. Downstream transportation | Emissions from outbound logistics | Medium for manufacturing |
| 10. Processing of sold products | Emissions from customers processing your product | Low for most SMEs |
| 11. Use of sold products | Emissions from customers using your product | Sector-dependent |
| 12. End-of-life treatment | Emissions from disposal of your product | Low for services, medium for products |
| 13. Downstream leased assets | Emissions from assets you lease to others | Rarely relevant |
| 14. Franchises | Emissions from franchisees | Only for franchise models |
| 15. Investments | Emissions from financial investments | Only for holding companies |
Where to start: the pragmatic three
Most SMEs get 80% of their Scope 3 picture from three categories:
Category 1 — Purchased goods and services
This is almost always the largest category. It covers the cradle-to-gate emissions of everything you buy — raw materials, components, office supplies, professional services, software, cleaning.
Spend-based method (fastest): Take your total procurement spend by category, multiply by emission factors from a spend-based database (e.g., EXIOBASE, DEFRA Scope 3 factors, or the US EPA EEIO factors). This gives a directional estimate.
Activity-based method (more accurate): For your largest purchased items, use supplier-specific data or product-level emission factors. This requires more work but produces more credible results.
For a first cycle, use spend-based for the bulk and activity-based for your top 5 purchased items by spend.
Category 6 — Business travel
Flights, hotels, and rental cars booked for business purposes.
Data sources: Travel management system, expense reports, credit card statements.
Calculation:
- Flights: number of flights by distance band (short-haul, medium-haul, long-haul) and class × DEFRA air travel factors
- Hotels: number of nights by country × DEFRA hotel factors
- Rental cars: km driven by fuel type × DEFRA vehicle factors
This is usually straightforward because SMEs book travel centrally or can extract it from expense claims.
Category 7 — Employee commuting
Emissions from employees travelling between home and work.
Data sources: Employee survey (distance, mode of transport, frequency) or estimate based on average commuting distance for your region.
Calculation: Average one-way distance × 2 × working days per year × number of employees × emission factor per km by transport mode.
For a first cycle, a simple employee survey or a national-average estimate is sufficient.
Calculation approaches compared
| Approach | Accuracy | Effort | Best for |
|---|---|---|---|
| Spend-based | Low–Medium | Low | First cycle, broad coverage |
| Average-data (activity) | Medium | Medium | Top categories with physical data |
| Supplier-specific | High | High | Key suppliers who share their data |
| Hybrid | Medium–High | Medium | Spend-based baseline + supplier data for top items |
Most SMEs should use the hybrid approach: spend-based for the long tail, supplier-specific or activity-based for the largest line items.
Data quality and disclosure
VSME Comprehensive asks you to disclose:
- Which Scope 3 categories you assessed
- The methodology used per category (spend-based, activity-based, or supplier-specific)
- The estimated emissions per included category
- A note on data quality and limitations
Be transparent about methodology. Stating “Category 1 was estimated using spend-based EXIOBASE factors, covering 85% of procurement spend” is a perfectly acceptable disclosure.
Common mistakes
- Trying to cover all 15 categories in the first cycle. Start with 2–3 categories. You are not a multinational — not all categories are material.
- Using outdated emission factors. Spend-based factors change annually. Use factors from the year matching your data.
- Double-counting with Scope 1 and 2. Energy consumed at your premises is Scope 1/2. Do not also count it under Category 3 unless you are specifically reporting well-to-tank emissions.
- Confusing relevance with materiality. A category can be “relevant” (it exists for your business) but immaterial (the emissions are negligible). Focus on categories that are both relevant and significant.
Next steps
Once you have Scope 1 + 2 from carbon accounting and Scope 3 for your material categories, you have a total carbon footprint. This feeds into:
- Your VSME Comprehensive report under the emissions disclosure
- Your double materiality assessment where climate change is a material topic
- Science-based target setting (if you choose to pursue SBTi)
- Responding to customer data requests that go beyond Basic
The key principle: Scope 3 is a journey. Start with what you can measure, disclose your methodology, and improve over time.
Frequently asked questions
Do SMEs need to report Scope 3 emissions?
Not under VSME Module Basic. Scope 3 is only part of VSME Comprehensive, and even there it is limited to categories where data is reasonably available. Most SMEs should complete Scope 1 and 2 first before considering Scope 3.
Which Scope 3 categories are most relevant for SMEs?
For most SMEs, Category 1 (purchased goods and services), Category 6 (business travel), and Category 7 (employee commuting) are the most accessible starting points. Manufacturing SMEs should also consider Category 4 (upstream transportation) and Category 5 (waste generated in operations).
How accurate does Scope 3 data need to be for VSME?
VSME Comprehensive acknowledges that Scope 3 data quality is inherently lower than Scope 1 and 2. Spend-based estimates are accepted for a first cycle. The expectation is directional accuracy — within the right order of magnitude — not precision. Improve data quality over subsequent cycles.
What is the difference between spend-based and activity-based Scope 3 calculation?
Spend-based uses your procurement spending multiplied by sector-average emission factors (e.g., kgCO₂e per euro spent). Activity-based uses physical quantities like kg of materials, km transported, or number of flights. Activity-based is more accurate but requires more detailed data. Most SMEs start with spend-based.