What does scope 3 actually require a small organisation to measure?

Three of the fifteen scope 3 categories usually carry nearly all of a small organisation's emissions: purchased goods and services, business travel, and employee commuting. Take those from the purchase ledger, expense claims and one annual staff survey, then state which categories you excluded and why.

Fifteen categories, most of them empty

The Greenhouse Gas Protocol Corporate Value Chain (Scope 3) Standard defines fifteen categories. They were written for organisations with subsidiaries, franchises, leased estates and investment portfolios, so a ten-person organisation will find that most of them describe something it does not do. An empty category is not a gap in the report. It is a fact about the organisation, and it should be recorded as one.

The ones that usually apply

Category	What it covers	Where the number comes from
1. Purchased goods and services	Everything you buy, from laptops to accountancy	Purchase ledger, grouped by spend category
6. Business travel	Trains, flights, hotels, private cars on business	Expense claims
7. Employee commuting	Journeys to work, plus energy used working from home	One staff survey a year
5. Waste in operations	What leaves the building and how it is treated	Contractor invoices, in tonnes
4. Upstream transport	Deliveries in, where you pay for them	Courier and supplier invoices

If you sell a physical product, categories 9 to 12 (downstream transport, use of sold products, end-of-life treatment) apply too, and category 11 often dwarfs everything else. If you sell your time, they do not.

Category 1 is the difficult one

Purchased goods and services is usually the largest number and the least precise. There are two ways to produce it:

• Spend-based. Multiply what you spent in a category by an emissions factor per pound. Fast, complete, and rough. It also has the perverse property that paying more for the same thing raises your reported footprint.
• Supplier-specific. Ask your largest suppliers for their own figures. Slow, better, and only worth doing for the handful of suppliers that account for most of the spend.

Start spend-based across everything, then replace the top few suppliers with real data as they provide it. Keep the two clearly distinguished in the spreadsheet.

What is actually required of you

For most small organisations in the UK, nothing is required by law. Streamlined Energy and Carbon Reporting applies to quoted companies and to large unquoted companies and LLPs, and even then scope 3 is limited to business travel in employee-owned vehicles (the government's environmental reporting guidelines).

The pressure comes from elsewhere: a customer measuring its own category 1 will ask you for your figure, and a funder will ask before awarding. Being asked is the reason to have a number, and the number does not need to be perfect to be useful.

Say what you left out

A short exclusions note does more for credibility than a larger total. One line per omitted category, giving the reason: not applicable, immaterial, or no data available this year. Anyone checking your figure will look for that note first, and its absence is what makes a total look invented.

How long it takes

Adding scope 3 to an existing scope 1 and 2 footprint is a day for the ledger work, plus however long it takes to get a staff survey back. The survey is the part that slips, so send it before starting on the ledger.

More answers

• How does a small organisation work out its carbon footprint without buying software?

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