Moving from estimates to measured data

What is the difference between an estimate and a measured figure?

The factor, not the input. Every emissions figure is something you know (money spent, tonnes bought, litres burned) multiplied by an emission factor. A first estimate uses an industry average factor: so many kilograms of CO2e for a typical pound or euro spent on steel, or for a typical tonne of it. A better figure uses a factor that belongs to the actual thing: your steel supplier's own published emissions, the measured fuel of your haulier, or a carbon footprint for the exact product you buy. The GHG Protocol calls the first kind secondary data and the second kind primary data. Spend can be the input for either; what changes is whose number multiplies it.

Why does the factor matter more than the input?

Because an industry average cannot tell one supplier from another and does not change when your supplier improves. If your steel supplier switches to an electric arc furnace running on renewable electricity, a sector-average figure for "steel" shows nothing. Their own factor applied to the same purchase shows the drop. That is what a customer means by better data, and it is the same reason your customer wants your figure rather than an average for your sector: an average never moves when you do.

The input is a separate question. Spend is a perfectly good input where it is what you have, and a supplier's own factor applied to your spend with them is primary data under the standard. Tonnes or litres are better inputs where you hold them, because they do not move with prices. A product footprint is better still for the items that matter. Improve the factor first, then the input, and say which you have done.

How does a figure improve, step by step?

For any one line of your Scope 3, there is a ladder. You move up it as data becomes available, and you do not need to reach the top for every line.

1. Industry average applied to spend. Where you start. Quick, rough, and it cannot show improvement.
2. Your supplier's own factor applied to spend. Costs you nothing extra if the supplier has published a footprint. Changes when they reduce. This is the step most companies do not know is available.
3. Actual activity data. Tonnes of material, tonne-kilometres of freight, litres of fuel, multiplied by a published factor for that activity. Separates two suppliers of the same thing and does not move with prices.
4. A product carbon footprint. A figure for the exact item from the supplier that makes it, checked against a standard. The most accurate and the most work, so reserve it for the products that matter.

Your customer will accept: a footprint where each line says which rung it is on. They are far more interested in that label than in whether every line has reached the top.

Which categories should I improve first?

The largest ones, because that is where a better factor changes the total. For most suppliers that means, in order: Scope 1 and 2 (already measured from bills if you followed the earlier guides); freight, where many hauliers now report emissions per shipment on request; the two or three biggest purchased materials, where asking the supplier for their published footprint moves you to rung 2 for free; business travel from expense records; and waste tonnes from your contractor. Leave the long tail (office supplies, small services) on an industry average and say so. A footprint that is specific where it is large and averaged where it is small is what a customer wants to see.

Where does the better data come from?

From the people who already hold it. Your main suppliers, for their own published figure or a product footprint: ask them the question you were asked, and the Lead stage covers how. Your haulier for freight per consignment. Your waste contractor for tonnes by type. Your finance or purchasing system for quantities on purchase orders, which many systems record alongside spend. For the published factors on rung 3, national databases are free: France's Base Empreinte and Japan's emission factor database both cover materials, freight and waste, and the GHG Protocol's calculation tools give category-by-category guidance on what to collect.

How do I show which factor I used?

In a column next to each line of your footprint: "industry average", "supplier's own figure", "activity data" or "product footprint", with the source. Customers increasingly ask for exactly this, and some rate the quality of a supplier's data on it. It also protects you: when a line rises because you replaced an average with the supplier's real figure, the label is how you explain that the data got better, not the performance worse.

How long does this take?

A category or two a year is a reasonable pace for a small company. Year one: Scope 1 and 2 measured, everything else on industry averages, labelled. Year two: freight from the haulier, main materials on the suppliers' own figures. Year three: travel, waste, and a product footprint for anything a customer has asked about. By then the averaged share is small and the total moves when you and your suppliers act.

Do this week: add a factor column to your footprint spreadsheet and label every line. Then email your two largest suppliers and your haulier and ask whether they publish an emissions figure.

What should I do next?

Publishing your numbers and what "verified" means covers how to present the figure with its labels. Once your supplier-specific data is in, claim your DitchCarbon profile if your customer uses it, so the improved figure is what they see.