Scope 3 data collection: how to request emissions data from suppliers

You have decided to start Scope 3 accounting and you are facing your first supplier survey. What do you ask, who do you ask, in what format, and what do you do when half of them do not respond? This article walks through practical guidance for building a supplier survey and handling the responses.

Why supplier data is the hardest part of Scope 3

Suppliers rarely have emissions data ready in a form you can use directly. Large companies report their own Scope 1+2 figures in annual reports, but smaller suppliers have nothing prepared. Response rates in first-round supplier surveys are typically low if the survey is sent without prior discussion or a contractual basis.

This is the most labour-intensive part of a Scope 3 project, and it is where consultants add the most value. Sending the supplier survey, tracking responses, sending reminders, and filling gaps in incomplete data can easily take weeks of calendar time. Most SMEs do not want their procurement or finance team spending their own working hours on this, which is why data collection can be outsourced.

Which suppliers to prioritise

Do not send a survey to all dozens or hundreds of suppliers. Follow the 80/20 rule.

Start with the 10–20 largest suppliers by procurement volume (in euros). This group typically covers 70–90% of Category 1 purchases. The rest can be handled with a spend-based method using industry-specific emission factors.

Also prioritise strategic suppliers whose product is emissions-intensive. For example, a small but emissions-intensive raw material supplier (metals, concrete, chemicals) may be more important than a large but low-emission supplier (e.g. office supplies).

Take into account contractual leverage. Long-term and significant customers have more leverage to request data. If you are a small customer to a supplier, the threshold is higher and response rates will be lower.

What to ask suppliers

A good survey is concise: 5–10 questions, no more. A long survey reduces response rates.

Product-specific carbon footprint, if one exists. This is the ideal answer. A Product Carbon Footprint (PCF) compliant with ISO 14067 or an EPD provides a direct figure: kg CO2e per unit sold.

The supplier’s total Scope 1+2 emissions and revenue. From this, a rough intensity (kg CO2e per €) can be derived and used when no product-specific PCF is available.

The methodology and emission factor the supplier uses, if they already have a calculation. It is important to know whether the figure is based on activity-based or spend-based methods, and which emission factor library is in use (Ecoinvent, EXIOBASE, DEFRA, etc.).

Whether the supplier has an SBTi target or a CDP response. Validated targets and CDP scores are additional information that indicates the supplier’s maturity level.

Contact person and update frequency. So that you do not have to start from scratch the following year.

Survey structure: a streamlined model

An effective survey contains four elements.

Cover letter. 3–4 sentences: why you are asking, what the data will be used for, what the deadline is, and who the contact person is. If the supplier is large and receives dozens of similar requests, emphasise the purpose (e.g. CSRD reporting or an SBTi target), and keep the information easy to compare with other customers’ surveys.

Questionnaire. Excel or an online form. 5–10 questions, some open-ended, some numerical. Provide clear units (tCO2e, kg CO2e per €, kg CO2e per kg of product).

Timeline. A realistic deadline: 4–6 weeks from sending. A shorter timeline reduces response rates. Let suppliers know in advance that a reminder will be sent after 2 weeks.

Contact. One person the supplier can contact for further information. Avoid generic group mailboxes.

NGS delivers this entire package as a ready-made template and handles the survey distribution, follow-up, and compilation of responses on your behalf. The survey reaches suppliers under NGS’s name on behalf of the client, or under the client’s own name, depending on which better suits the business relationship.

What to do when a supplier does not respond

Response rates almost always fall below 100%. The GHG Protocol allows a hybrid approach in which primary data is used where available and secondary data fills the gaps elsewhere.

Practical workflow:

PCF or emissions figures received from suppliers as the primary source.
Public annual reports and CDP responses for large suppliers that did not respond.
Industry-specific emission factors from EXIOBASE, US EEIO, or an equivalent source for the remainder, multiplied by the procurement spend in euros.

This is the practical golden mean, and it is acceptable under both the GHG Protocol and SBTi validation. The most important thing is to document transparently where each figure comes from and which method was used.

The CDP Supply Chain programme is one international channel that large companies use to collect supplier data. If your supplier is already a CDP respondent, the data can be requested through CDP.

Frequently asked questions

Is a supplier required to respond to the survey?

There is no legal obligation. In practice, many suppliers do respond because their own customers require it, because it is part of the supplier agreement, or because it has become part of normal business practice in the ecosystem around large companies.

What is a typical response rate?

In the first round without prior groundwork, response rates often fall below 50%. With a good cover letter, contractual grounding, and reminders, 50–70% is achievable. With repeated annual surveys and established processes, higher rates are possible.

Is spend-based calculation alone sufficient?

For a start, yes. The spend-based method gives an overview of the whole picture and identifies hot spots. More accurate primary data should be targeted for the largest categories in subsequent rounds. SBTi accepts spend-based methods for target-setting, as long as the methodology is documented.

Can data collection be outsourced?

Yes, and this is typical in SMEs that do not have their own Scope 3 team. The NGS model is that we send the surveys, track responses, and compile the data. You do not need to coordinate supplier communications.

What if a supplier only provides their Scope 1+2 figures?

This is a good starting point. You can allocate the supplier’s total emissions to your share as a proportional share of revenue or procurement volumes. This is approximate but an accepted method when no product-specific PCF is available.

Let us handle the supplier survey

NGS sends surveys to your suppliers, tracks responses, and compiles the data. You do not need to coordinate it.

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