26 August 2026

How to Update an LCA When Your Product BOM Changes

A changed bill of materials can alter quantities, materials, suppliers, processes, transport and packaging. Updating the LCA requires more than importing the latest spreadsheet: preserve the old model, isolate what changed, review affected inventory data and calculate a controlled new version.

TL;DR

Freeze the existing BOM and LCA as a baseline, create a new product version and compare the BOMs line by line. Update only the affected inventory and evidence, keep the impact method and database version controlled, recalculate, review the differences and record why the new result changed.

1. Preserve the current BOM and LCA

Do not overwrite the model that produced the existing result. Save or lock the current BOM, its LCA study, mappings, datasets, method, database version and supporting files. This creates a reproducible baseline for the comparison.

Versioning is not just housekeeping. Makersite recommends creating a new BOM version when a product changes and says saved versions can be locked for traceability. The GHG Protocol Product Standard also addresses inventory-change tracking and data-management planning.

The evidence supports a controlled sequence: preserve the baseline, create a new version, compare line items, update affected inventory data, recalculate and document the decision.

Process from preserving the baseline BOM through versioning, comparison, inventory updates, recalculation and documentation

In Dawn, teams can use version-controlled assembly BOMs to keep parts, assemblies, variants and versions connected to their LCA studies. Excel/CSV part import is available, but the imported file still needs review before it becomes the basis for a new result.

2. Compare the old and new BOM line by line

Run a structured comparison rather than looking only at total product mass. Identify added, removed and replaced parts; quantity changes; material substitutions; supplier changes; revised subassemblies; and changes to packaging, scrap or transport assumptions.

Check identifiers as well as descriptions. A renamed part may be the same physical item, while an unchanged part number may hide a new material or supplier. Review units carefully: kilograms, grams, pieces and square metres cannot be treated as interchangeable without the correct conversion. See Dawn’s guide to units used in LCA for the underlying unit logic.

The Product Standard covers data collection, quality, allocation, uncertainty, calculation and inventory-change tracking, making these useful controls for classifying each BOM difference (GHG Protocol Product Standard).

Matrix connecting quantity, component, supplier, process, packaging and function changes to required LCA checks

A practical comparison file should record the old value, new value, change type, affected LCA process, evidence source and reviewer decision. It should also flag duplicate parts, deleted subassemblies, missing supplier evidence and unmatched rows.

3. Separate physical changes from modelling changes

Keep the impact method and background database version unchanged while assessing the physical BOM update. Otherwise, a result difference could come from two sources at once: the product changed and the calculation basis changed.

For example, substituting a material while also moving to a newer background dataset makes it difficult to attribute the result. First calculate the revised BOM using the original method and database version. If a method or dataset update is also required, calculate that as a separate scenario and document both effects.

This control follows the Product Standard’s treatment of calculation, data quality, uncertainty, reporting and inventory-change tracking. It also fits the four-phase structure of LCA under ISO 14044: goal and scope definition, inventory analysis, impact assessment and interpretation.

4. Update the affected inventory and mappings

For each changed row, confirm that the mapped LCA process still represents the actual material, geography, technology and supplier situation. Do not assume an old mapping remains valid after a description or supplier change.

Review these inputs where applicable:

Material type and quantity
Unit and conversion factor
Recycled or secondary content represented by the selected dataset
Supplier-specific evidence
Manufacturing energy and scrap
Inbound and outbound transport
Packaging materials
Nested assemblies and allocation
Product function and functional unit

Several tools support parts of this workflow, but importing or refreshing a BOM is not the completed assessment. Human review remains necessary for uncertain rows, mappings and modelling decisions.

Tool	BOM update capability	Review or control described
Dawn	Excel/CSV part import; assemblies, variants, versions and suppliers in a living product-and-LCA model	Product versions and shared product/LCA data can be maintained through product information management for manufacturers
Earthster	Creates or updates product LCAs from CSV and XLSX BOM files	Recognizes common columns and supports functional units and nested products; Generator is a Corporate-plan feature (Earthster Generator documentation)
Sphera	BOM Import add-on for LCA for Experts	Supports BOM uploads and design-scenario comparisons (Sphera BOM Import)
Makersite	Creates and edits BOMs, including nested structures	New versions can be locked; unlocked BOMs can synchronize updated component-emission values (Makersite BOM documentation)
Ecochain	Imports, exports and copies product-composition BOMs	Requires a material list, material weight per product unit and units of measurement (Ecochain Helix documentation)
One Click LCA	Early Access AI importer accepts XLSX files	Requires description, quantity and unit; normalizes units and flags uncertain rows for review (One Click LCA importer documentation)
SimaPro	External Model Calculator receives a BOM from a business-intelligence system	Uses data mapping and placeholder processes, then recalculates after mappings are created (SimaPro External Model Calculator guide)
openLCA	Referenced-process changes are reflected in product-system calculations	The displayed system can be refreshed by reopening or reloading it (openLCA support answer)

5. Recalculate and explain the difference

Run the revised model only after mappings and units pass review. Compare the new result with the frozen baseline by impact category, life-cycle stage, component, supplier, transport and manufacturing energy—not only by total carbon footprint.

Investigate unexpected movements. A large change may be valid, but it may also indicate a unit conversion error, duplicated component, deleted subassembly, changed allocation or accidental dataset substitution. A nearly unchanged total can also hide offsetting increases and decreases across stages.

In Dawn, product LCAs can use Ecoinvent-based databases with EN 15804, EF 3.1 and cutoff methods, with reports showing hotspots, life-cycle stages and kg CO2e through the workflow to calculate product carbon footprints. A product carbon footprint is the carbon result on an LCA study, not a separate object, and it should not be treated as automatically equivalent to an ISO 14067 study or an EN 15804 declaration.

6. Decide what must be updated externally

Separate internal model maintenance from customer-facing reports and externally reviewed publications. An internal LCA can be revised as part of product data control. A customer report may require a new issue date and explanation. An EPD follows its program operator’s rules and external verification process.

The International EPD System says an EPD must be updated during its validity when an aggregated result for a declared indicator increases by at least 10%, or when substantial changes occur in the product, manufacturing site, composition, supplier data or underlying datasets. That is program-specific guidance, not a universal threshold for every LCA or EPD program (International EPD System update guidance).

10% or more increase in an aggregated declared indicator is one International EPD System update trigger

EPD-style table exports can support the handoff, but method choices, missing primary data and verifier discussions remain human responsibilities. Verification occurs outside Dawn; the software does not issue or certify EPDs.

BOM-change LCA checklist

Before approving the revised result, confirm that the team has:

Preserved the previous BOM, LCA result and supporting evidence
Created a distinct product or assembly version
Compared added, removed, replaced and quantity-changed lines
Checked units, conversions, duplicate parts and nested assemblies
Reviewed material, supplier, process and geography mappings
Updated packaging, transport, scrap and manufacturing inputs where affected
Kept the impact method and database version controlled
Recalculated all affected product models and variants
Compared results by category, stage, component and hotspot
Explained material differences and unexpected results
Recorded assumptions, evidence gaps and reviewer decisions
Checked whether customer reports or externally reviewed publications require an update

A repeatable process turns BOM changes into controlled LCA revisions rather than one-off rebuilds. The essential rule is simple: version first, change one calculation basis at a time, and retain enough evidence to explain every meaningful difference.