Scope 3: why 90% of companies get it wrong the first time
The hardest scope in the GHG Protocol is also the most audited. Here are the 7 most common mistakes, how to avoid them, and how to structure value chain data collection without it becoming an operational nightmare.
Why Scope 3 is so hard
There are 15 different categories, data coming from the entire value chain (suppliers, clients, carriers, employees) and emission factors scattered across sources. On average, Scope 3 accounts for 70 to 90% of a company's total emissions, and it is the part the auditor examines most closely when the report lands on the desk.
Unlike Scope 1 (which lives inside the company) and Scope 2 (which sits in the energy contract), Scope 3 depends on third-party information, with variable quality and a long collection time. That is why the first attempt almost always comes back with structural errors.
The 15 categories, one line each
Upstream:
- Purchased goods and services.
- Capital goods.
- Fuel and energy (not covered in Scope 1+2).
- Upstream transport and distribution.
- Waste generated in operations.
- Business travel.
- Employee commuting.
- Upstream leased assets.
Downstream:
- Downstream transport and distribution.
- Processing of sold products.
- Use of sold products.
- End-of-life treatment of sold products.
- Downstream leased assets.
- Franchises.
- Investments.
The 7 most common mistakes
1. Skipping categories without justification
The standard requires every omitted category to carry a documented justification (materiality below the threshold, or data unavailable with an action plan for the next cycle). Silent omission equals non-conformity.
2. Using secondary data when primary data exists
Spend-based or activity-based with a default factor is only acceptable when primary data is unavailable. When it exists, the auditor requires it. Otherwise inventory quality drops and it can fail independent verification.
3. Confusing "outsourced" with Scope 3
An outsourced fleet for your own use (a third-party driver operating the company's vehicle, under your control) is Scope 1. A carrier contracted for freight is Scope 3 category 4 or 9. A rental car for occasional use is category 6 (travel). A recurring source of confusion.
4. Ignoring business travel (category 6)
It is one of the fastest categories to calculate (the travel agency or the HR system consolidates it) and it is usually forgotten. For a professional services firm it can reach 15-20% of total emissions.
5. Underestimating purchased goods and services (category 1)
Usually the largest source, and it needs spend-based or activity-based done properly. Companies start with an aggregate factor per product class and refine year by year. Common mistake: applying one generic factor across a base of 5,000 different suppliers.
6. Forgetting use of sold products (category 11)
For equipment, automotive, electronics and software manufacturers (yes, software too, through the client's server consumption), it is frequently the largest category. A company that ignores 11 is omitting more than 50% of its emissions.
7. Not engaging suppliers early
Without primary data, precision drops and the auditor asks for improvement plans. Engaging the 20-30 suppliers that account for 70-80% of spend is the path with the best return.
The good-practice methodological hierarchy
For each category, climb the hierarchy across cycles:
- Primary supplier data (best): their audited actual emissions, allocated to your consumption.
- Activity-based with a local factor: physical unit × verified regional factor.
- Activity-based with a default factor: physical unit × IPCC or DEFRA factor.
- Spend-based: monetary value × monetary factor (ecoinvent, CDP, MCTI).
- Default value: a single sector figure, with no collection. Last resort.
Suggested operational roadmap
| Cycle | Depth |
|---|---|
| Year 1 | Spend-based across every material category; primary only for travel, energy and fuel |
| Year 2 | Activity-based in the 3 most material categories; primary from 5-10 strategic suppliers |
| Year 3 | Primary from the 30 suppliers making up 70-80% of spend; activity-based everywhere else |
| Year 4+ | System integrated with the ERP and a supplier platform; automated collection |
How Mangue solves it
Crab.AI maps invoices to emission factors across the 15 Scope 3 categories automatically, in seconds, with an audit trail. The platform sends structured forms to suppliers and consolidates everything in one dashboard. The consulting validates materiality, the collection plan and the narrative.
Typical result for a new client: a first complete Scope 3 inventory in 8 to 12 weeks, covering more than 90% of spend, at a quality approved under limited assurance.
- Every omitted category needs documented justification (materiality below the threshold, or data unavailable with an action plan).
- Methodological hierarchy: primary data > activity-based > spend-based > default value. Climb the hierarchy year by year.
- Categories 1 (purchased goods and services) and 11 (use of sold products) usually hold most of the emissions; prioritise them.
- Engage the 20-30 suppliers that make up 70-80% of spend: the relationship is where primary collection becomes viable.
- A platform with a structured supplier form cuts collection time from months to weeks.
Perguntas frequentes
Can I skip Scope 3 and report only 1 and 2?+
For internal use, yes; for CDP, IFRS S2, CSRD and SBTi, no. SBTi requires a Scope 3 target whenever it is more than 40% of total emissions (it was 67% before V2). CDP penalises the score if Scope 3 is not covered. IFRS S2 and CSRD expect full reporting, with documented justification for every omitted category.
What is the difference between activity-based and spend-based?+
Activity-based uses a physical unit (kg of steel, kWh of energy, km driven) multiplied by an emission factor. Spend-based uses a financial value (money spent) multiplied by an emission factor per monetary unit. Activity is more precise; spend is faster for initial collection. An auditor accepts spend as a starting point with a plan to migrate to activity.
Is an outsourced fleet Scope 1 or Scope 3?+
It depends on operational control. If you control the operation and are responsible for maintenance, it is Scope 1 (even if a third party owns the vehicle). If the fleet is contracted operation (a third-party carrier), it is Scope 3 category 4 (upstream transport) or 9 (downstream). This mix-up is the most common mistake in logistics.
How do I calculate Scope 3 category 11 (use of sold products)?+
For a product that consumes energy in use (an appliance, a vehicle, software): multiply average lifetime consumption by the emission factor of the expected energy source. For a product that becomes fuel or feedstock: account for downstream combustion or processing emissions. It is the category that fails industrial audits most often.
How long does it take to close Scope 3 at a mid-sized company?+
First full cycle: 4 to 8 months for a mid-sized company, depending on the maturity of internal data and supplier engagement. The second cycle drops to 2-3 months once the platform and the process are in place.
- Scope 3
- Indirect emissions that occur in the company's value chain, split into 15 upstream and downstream categories by the GHG Protocol.
- GHG Protocol
- Greenhouse Gas Protocol Corporate Standard. The global standard for corporate emissions inventories, maintained by WRI and WBCSD.
- Activity-based
- A calculation method based on a physical unit of the activity (kg, kWh, km) multiplied by an emission factor.
- Spend-based
- A method based on financial value multiplied by an emission factor per monetary unit. Less precise, faster.
- Materiality
- The principle that you report what is relevant. A category below the materiality threshold can be omitted with documented justification.
- Category 1
- Purchased goods and services. Usually the largest category for retail, services and light industry.
- Category 11
- Use of sold products. Usually the largest for equipment, automotive and electronics manufacturers.
- Emission factor
- The coefficient that converts a unit of activity or spend into tCO₂e. Databases used: DEFRA, MCTI, ecoinvent, IPCC, CDP.
Frameworks mencionados neste artigo
IFRS S1 & S2 Roadmap
The 12 decisions your CFO has to make before 2027. Free.
