Scope 3 emissions: the numbers you have to ask other people for

Scope 3 emissions are the ones you cause but do not control: what your suppliers emitted making what you bought, what your customers emit using what you sold, what your staff emit commuting and travelling. Scope 1 is fuel you burn, scope 2 is electricity you buy, and both are countable from invoices. Scope 3 is typically the large majority of a company’s footprint and the part that cannot be measured without asking other organisations for numbers they may not have.

The fifteen categories, and the ones that matter

• Upstream: purchased goods and services, capital goods, fuel and energy activities, transport and distribution, waste, business travel, employee commuting, leased assets.
• Downstream: transport and distribution, processing of sold products, use of sold products, end-of-life treatment, leased assets, franchises, investments.
• For most companies two or three categories are the overwhelming majority. Purchased goods and services dominates for anyone who buys physical inputs; use of sold products dominates for anyone selling something that consumes energy.
• Screen all fifteen roughly, then measure properly only the ones that are large. A precise number for business travel next to a rough one for purchased goods is effort spent backwards.
• Document the categories excluded and why — omissions are acceptable and unexplained omissions are not.

Getting scope 3 emissions from spend to a number

1. Start with spend-based estimation: multiply what you spent in a category by a published emissions factor. It is crude, it is accepted as a starting point, and it tells you where to look.
2. Move the largest categories to activity-based data — tonnes of steel rather than pounds spent on steel — because spend-based numbers fall when prices fall, which is not a reduction in emissions.
3. Ask your significant suppliers for their own figures, and expect a low response rate the first year. Asking through the supplier onboarding process for new suppliers works better than a mass email to existing ones.
4. Record the method per category, because mixing methods across years destroys comparability and the first question an assurer asks is what changed.
5. Set a base year and restate it when the method improves rather than presenting an improvement in measurement as a reduction in emissions.

The single most common misrepresentation in this area is a fall in the number caused by better data or lower prices being reported as progress. If the methodology changed, say so and restate the comparison. Assurers look for this specifically, and so increasingly do customers running their own value chain calculations.

Collecting supplier data without a platform

• Ask a small number of questions: do you measure, what were your scope 1 and 2 totals, what proportion of your output do we represent, and do you have a target.
• Ask the same questions every year in the same form, so answers are comparable.
• Tell suppliers what you will do with it — a request with no stated purpose gets deprioritised.
• Accept partial answers and record gaps rather than leaving blanks, since a blank cannot be distinguished from an unanswered question later.
• Where the supplier code of conduct already asks for environmental compliance, extend it rather than starting a separate programme with different governance.

Where the data lives

Ettex Forms handles the supplier request side: the same short structured questionnaire each year, with responses landing as dated records you can filter by category and by response status — which is what turns a chase into a list rather than an inbox search. The calculation itself belongs in a sheet with the factors and methods visible per category. Ettex is not a carbon accounting platform: it holds no emissions factor database, performs no conversions and produces no report in a standard’s format. For a company under formal reporting obligations that tooling is worth buying; what this covers is the data collection underneath it, which the platforms are consistently worse at than they claim.