Custom Emission Factors (LCA / EPD)

Last updated: 18 August 2026

Custom Emission Factors LCA EPD Supply Chain

By default, NetNada calculates supply chain emissions using industry-average emission factors — the standard approach when all you know about a purchase is what it was and what it cost. Custom emission factors let you go a step further: when a supplier provides a Life Cycle Assessment (LCA) or Environmental Product Declaration (EPD), you can apply their verified, supplier-specific emission intensity to the relevant transactions instead of the generic average.

In this article, you'll learn how to:

Understand what LCAs and EPDs are, and why they improve your Scope 3 accuracy
Prepare supplier evidence before making any changes
Apply a custom emission factor to transactions on the Audit Page — individually or in bulk
Keep your custom factors defensible for auditors and up to date over time

Why Custom Factors Matter

Industry-average factors assume your supplier performs like the average business in their sector. If a key supplier has genuinely decarbonised — switched to renewable electricity, changed materials, redesigned their product — an average factor hides that progress, and your footprint won't reflect the better purchasing decision you made. Supplier-specific data (called primary data) replaces the estimate with evidence, which matters most for your highest-impact materials and biggest suppliers.

An LCA analyses a product's environmental impact across its whole life — raw materials, manufacturing, transport, use, and disposal. An EPD is a standardised, independently verified document built on an LCA that states the product's emission intensity (for example, kilograms of CO₂e per tonne of material). Either can supply the numbers behind a custom emission factor.

Prerequisites

Before applying custom factors you need: the supplier's evidence document (LCA report or EPD certificate), the emission intensity value from that document with its unit, and existing transactions in your carbon inventory to apply it to.

How to Apply a Custom Emission Factor

Gather the supplier's evidence

Request the LCA or EPD from your supplier and note the emission intensity value and its unit. Check that the document is current — EPDs carry a validity period, typically five years.

Open the Audit Page and find the transactions

Navigate to the Audit Page and filter by supplier name to see every transaction for that supplier. You can also use the AI search — for example, "show me all entries from this supplier".

Edit the emission factor

Select the entry (or entries) and choose Edit Emission Factor. Pick the appropriate replacement factor, keeping the unit consistent with the transaction's activity data.

Apply in bulk where it makes sense

For suppliers with many transactions, apply your filter first, then use Select All — the selection covers only the filtered entries — and apply the factor to all of them in one action.

Verify the result

Emissions for the affected transactions recalculate immediately and your dashboards refresh to match. Each change is recorded in the audit trail with a timestamp, and the source file link on each entry keeps the evidence one click away.

Two things that cause problems: editing factors without keeping the supporting LCA or EPD on file undermines your position at assurance time, and mismatched units (for example, applying a per-kilogram factor to per-tonne activity data) produce calculation errors. Always confirm the unit before applying.

Keeping Custom Factors Audit-Ready

Custom factors shift your inventory from generalised estimates to primary data — a genuine accuracy improvement, but one your auditor will scrutinise. Three habits keep it defensible:

Prioritise ruthlessly. Target your highest-spending suppliers and highest-impact materials first — a handful of custom factors on major suppliers moves accuracy far more than dozens on minor ones.
Document every change. The audit trail records who changed what and when; keep the LCA or EPD itself uploaded so evidence and change sit together.
Review annually. Suppliers update their EPDs as they decarbonise. Revisit custom factors each reporting period and refresh any built on expired documents.

FAQ

What is the difference between an LCA and an EPD?

A Life Cycle Assessment (LCA) analyses the environmental impact of a product across its entire lifecycle. An Environmental Product Declaration (EPD) is a standardised document based on an LCA that provides verified emission intensity data. Both can be used as custom emission factors.

Can I apply a custom factor to multiple transactions at once?

Yes. Use the bulk selection feature on the Audit Page — filter for the relevant supplier or category, select all, and apply the custom factor to all matching entries simultaneously.

What happens to my existing calculations when I change an emission factor?

The emissions for affected transactions are recalculated immediately. Dashboards update automatically. The change is logged in the audit trail with a timestamp.

How often should I update custom emission factors?

Review annually, or whenever a supplier provides an updated LCA or EPD. Emission factors can change as suppliers decarbonise their operations.

Will my auditor be able to see which entries use custom factors?

Yes. Every factor change is timestamped in the audit trail, and the Audit Page can display the emission factor source for each entry — so custom factors are clearly distinguishable from database factors during assurance.

My supplier can't provide an LCA or EPD — what should I do?

Keep using the industry-average factor for now, and raise primary data as part of your supplier engagement. Many suppliers are being asked for this by multiple customers, so requests increasingly get results — start with your highest-spend suppliers.

Audit Page How to analyse your supply chain emissions