How to collect emissions data from your suppliers

Why ask suppliers for their figures

The emissions in what you buy are part of your Scope 3, as defined in the Greenhouse Gas Protocol (GHG Protocol) Scope 3 Standard. You can estimate them from averages, but averages treat every supplier of the same material as identical. Supplier figures are more accurate, and they are the only way a supplier's real reductions show up in your numbers.

The requests you receive draw on these figures too. Customer questionnaires ask for Scope 3. Central government contracts worth more than £5 million a year ask for a Carbon Reduction Plan under Procurement Policy Note 006 (PPN 006). That plan includes five Scope 3 categories: upstream and downstream transport and distribution, waste, business travel and employee commuting.

For large UK companies under Streamlined Energy and Carbon Reporting (SECR), most Scope 3 reporting is voluntary. So the pull to measure it usually comes from customers rather than the law.

There is a cost reason as well. Asking suppliers to measure encourages them to look at their own energy and waste, which can lower the emissions in what you buy, and sometimes the cost.

Step 1: map your purchases

Start with your purchase ledger. Group spend by supplier and by category, then attach quantities for your main materials: tonnes of steel, polymer or packaging bought in the year. This gives you a map of where your purchased emissions come from.

Next, choose a method for each category. The GHG Protocol describes three.

Most manufacturers end up with a hybrid: spend for the long tail of small purchases, quantities for their main materials, and supplier figures where they matter most.

Build a first Scope 3 on spend, because it covers everything. Do not wait for perfect supplier data before you begin. The spend picture shows which suppliers and materials matter, even though it cannot yet tell one supplier from another.

Step 2: choose the suppliers to ask first

In many supply chains, a small share of suppliers accounts for most of the purchased emissions. Your own map will show whether that is true for you. Rank suppliers by estimated emissions, or by spend if that is all you have, and start with a short list at the top.

Use averages for everyone else for now. Each year, extend requests further down the list and switch more of the largest categories from spend to quantities.

Watch for suppliers that are small by spend but large by emissions. A modest bill for castings, heat treatment or galvanising can carry more carbon than a larger bill for office services, because the process uses a lot of energy. Spend alone can hide these, which is why quantities help.

Where you buy a product in volume, ask the supplier for a figure per product as well as a company total. It is the figure that will move most when either of you makes a change.

Step 3: design one short request

Use one template for every supplier, so the answers are consistent and can be added together. For most suppliers, start with this:

• Scope 1 and 2 totals for their most recent 12-month period;
• the method and emission factors they used;
• the share of their emissions that relates to what they sell you, and how they worked it out;
• figures per product for the items you buy in volume, where they have them;
• whether any figures have been independently checked;
• any reduction target and the main actions behind it.

Say which methods and factors you accept. For UK suppliers, the government's conversion factors from the Department for Energy Security and Net Zero (DESNZ) are a sensible default. Accept estimates, marked as such, and ask for better figures next year.

Send the same template again next year with only the dates changed. A repeat request is easier for suppliers to answer, and your figures stay comparable over time.

Step 4: send, support and follow up

Many of your suppliers will be small firms that have never measured. How you ask decides whether you get an answer.

1. 1Explain the reasonSay why you are asking and how you will use the data. Mention what is in it for them: lower energy costs, and ready answers for their other customers.
2. 2Give them a way inSend short guidance with the template. Point them to free help such as the DESNZ conversion factors on GOV.UK, the UK Business Climate Hub and the SME Climate Hub.
3. 3Name a contact and a dateGive one person to call with questions and a realistic deadline, not one set by your own reporting rush.
4. 4Follow upChase politely once the deadline passes, and accept a partial answer over none.
5. 5Recognise progressThank suppliers who reply and those who improve year on year. It makes next year's request easier.

Step 5: check the answers and build them into buying

Where a supplier's figure matters to your own reporting or to a customer, ask how it was calculated and whether it has been independently verified. A certified environmental management system, such as ISO 14001, is a sign the supplier handles environmental data in a structured way. Keep a record of what you received and when.

Expect the first year to be uneven. Some suppliers will send full figures, some an estimate and some nothing. Record which is which, so your own customers can see how much of your Scope 3 rests on supplier data and how much on averages.

Some suppliers will send only company totals. Allocate them by your share of that supplier's revenue and mark the result as an estimate. Replace averages in your Scope 3 line by line, and note the source of each figure.

As supplier data replaces averages, your totals will change for reasons that have nothing to do with real reductions. The GHG Protocol Corporate Standard sets out when to recalculate your base year. Restate it on the better method, so you compare like with like, and say that you did.

Make it part of how you buy

• State in your purchasing policy that carbon is considered alongside price, quality and delivery.
• Add emissions reporting to your supplier code of conduct or contract terms for new suppliers.
• Agree reduction goals with your largest suppliers and review them together each year.
• Bring purchasing into the work, because most Scope 3 changes are buying decisions: recycled content, lower-carbon grades, lighter designs and fuller loads.

How ESGen helps with supplier data

Here is what is live today. The ESGen platform measures your own Scope 1 and 2 from electricity, gas, diesel and petrol with the DESNZ factors. It adds staff car mileage and the upstream energy share of Scope 3, and keeps the bill and calculation behind every figure. That is the baseline your own suppliers' figures sit alongside.

Collecting data from suppliers inside the platform is not yet available to UK customers. Scope 3 beyond energy, including a supplier programme like the one above, is a new piece of work that we scope with you first. We say plainly what we will do and by when. Our team also prepares answers to your own customers' questionnaires from the same records. Read more about supplier engagement and our supply chain work.

To talk through your purchase ledger and where to start, book a demo.