# What do I do when there is no emission factor for a material I buy?

Canonical: https://senseible.earth/answers/no-emission-factor-for-material

Work down a ladder: ask the supplier for a product footprint, then look for a published factor for the same material, then use a documented proxy for a similar material, then fall back to a spend-based factor. If the line is small, you may exclude it with a stated reason. Never leave a guessed number unlabelled.

## The ladder, best option first

1. Supplier-specific data: an ISO 14067 product footprint or an environmental product declaration for the exact product.
2. A published factor for the same material from a recognised database, matched as closely as possible on technology and region.
3. A proxy: a factor for a similar material or a main ingredient, for example a generic polymer factor for a specialty compound. Write down why it is similar.
4. Spend-based: rupees spent x an economic input-output factor for that product group. Fast, but an average across many products.
5. Exclude, only if the purchase is small against your total and you state the reason and estimated size.

## How to judge a proxy

The GHG Protocol Scope 3 Standard asks you to rate data on five indicators: technological, temporal and geographical representativeness, completeness, and reliability. A proxy usually scores poorly on technology. Record the score, so readers know which figures are weak and which to replace first.

## Mistakes to avoid

- Using a factor in the wrong unit, such as a per-kg factor on a per-piece quantity.
- Mixing CO2-only factors with CO2e factors in one total without saying so.
- Using spend-based factors without adjusting for currency and price year, which can move results by a large margin.
- Filling the gap with zero. A line with no factor is a gap, not a zero.

## What to record for every gap

- The material, quantity and spend.
- Which rung of the ladder you used, the factor, its source and year.
- The data quality rating and the plan to get better data, usually a supplier request.

## What Senseible does here

Senseible follows a strict rule here: no factor, no figure. A purchase line with no matching factor is flagged in the supplier evidence trail and left without an emissions number, rather than filled with a guess. Choosing and documenting a proxy or spend-based factor is your decision.

- [Selecting emission factors](https://senseible.earth/climate-intelligence/emission-factors-selection-guidance)
- [Spend-based vs activity-based Scope 3](https://senseible.earth/climate-intelligence/spend-based-vs-activity-based-scope-3-method-choice)
- [Filling gaps in Scope 3 data](https://senseible.earth/answers/how-to-fill-gaps-in-scope-3-data)

Sources: [GHG Protocol Corporate Value Chain (Scope 3) Standard (2011), Chapter 7: data quality](https://ghgprotocol.org/corporate-value-chain-scope-3-standard), [GHG Protocol Technical Guidance for Calculating Scope 3 Emissions (2013)](https://ghgprotocol.org)

Last reviewed 2026-10-15.