Raw materials vs. process inputs: what goes where in your LCA

When you model a product in an LCA, every material you enter is either a raw material or a process input. Choosing the wrong one is the most common modelling mistake — and it quietly changes your carbon result. This article explains the difference, shows examples across industries, and covers why it matters.

The core distinction

A raw material is a material that physically becomes part of the final product. A process input (also called a consumption) is a material used up while making the product, but that does not end up in it.

	Raw material	Process input (consumption)
Ends up in the product?	Yes — it is part of what you ship	No — it is consumed during production
Where you model it	Raw material block	Inside the process, as a consumption
Transport included?	Yes — the material travels to your site	No transport modelled by default
Mental test	”Is this in the box I hand the customer?"	"Did I use this up to make the box?”

The single question that resolves almost every case: does this material leave the factory inside the product? If yes, it is a raw material. If it is consumed and stays behind, it is a process input.

The chair example

A wooden chair is the clearest way to see it.

The wood, screws, and fabric become part of the chair. They are raw materials.
If the metal frame arrives dirty and you wash it before assembly, the water and detergent used for cleaning are process inputs — they are consumed, they do not become part of the chair.

Same factory, same day, two very different roles.

Examples across industries

Industry	Product	Raw materials (in the product)	Process inputs (consumed)
Furniture	Wooden chair	Wood, screws, foam, fabric	Cleaning water, sandpaper, glue solvent that evaporates
Food & beverage	Bottled juice	Fruit, sugar, water in the drink, bottle, label	Cleaning-in-place water, steam for pasteurisation, filter media
Automotive	Steel part	Steel coil, coating that stays on the part	Cutting fluid, press lubricant, rinse water
Textiles	T-shirt	Cotton yarn, dye that fixes to the fabric, thread	Process water, softeners rinsed out, energy for drying
Cell-cultured / biotech	Biomass	Cells and any medium retained in the final biomass	Culture media consumed by cells, cleaning reagents, buffers
Cosmetics	Face cream	Every ingredient in the formula, jar, cap	Sterilisation steam, tank cleaning agents

Notice the pattern: water appears in both columns. Water that is part of the drink is a raw material; water used to clean the tank is a process input. The role — not the substance — decides the block.

Why this matters for your calculation

This is not just bookkeeping. The two choices are calculated differently.

A raw material block includes the upstream chain. When you enter a raw material, the LCA pulls in the full “cradle-to-gate” impact of producing that material and the transport of moving it to your site. A process input, by default, does not carry transport.

RAW MATERIAL (e.g. steel coil)
   ├── extraction of iron ore
   ├── steelmaking
   ├── rolling into coil
   └── TRANSPORT to your factory   ← included

PROCESS INPUT (e.g. cutting fluid)
   └── production of the fluid       ← included
       (no transport leg modelled by default)

So if you put a real raw material in as a process input, you understate its footprint — you drop the transport of that material entirely. Over a bill of materials with many bought-in parts, that gap adds up fast.

Common mistake

Entering a bought-in component as a process input to "save time." You lose its transport impact, and it no longer shows up as part of the product's material composition.

One process or several?

If you add the same material at several stages, model it where it is actually added.

If a chair passes through four processes and you add wood in each one, create a raw material block at each of those four processes — because each stage brings its own material (and its own transport).
If you have 4 kg of wood and you do not know the split across stages, create one raw material block with the 4 kg. Don’t invent a breakdown you don’t have.

Raw materials are not "spent"

A useful framing: process inputs are consumed, raw materials are incorporated. You spend water cleaning a part; you don't "spend" the wood — it becomes the chair. If you catch yourself saying a material is "used up," it's probably a process input.

Why this matters for your EPD

Only if you are preparing an EPD

This section is only relevant if you are working towards an Environmental Product Declaration. If you are not, you can skip it.

An Environmental Product Declaration (EPD) is a standardised, third-party-verified report of a product’s environmental impact, following ISO 14025 and EN 15804. EPDs are built directly on your LCA model, and they are structured by life-cycle stages — the A1–A3 modules for production:

Module	Stage	What belongs here
A1	Raw material supply	Your raw materials — the cradle-to-gate impact of each
A2	Transport to factory	Transport of those raw materials
A3	Manufacturing	Energy and process inputs consumed during production

The classification you choose maps straight onto these modules. Raw materials populate A1 and A2; process inputs populate A3. Get the split wrong and the EPD reports the impact in the wrong stage — which a verifier will flag, because A2 transport is expected to reflect the raw materials declared in A1.

Do this before you publish

Review your bill of materials and ask, item by item, "is this in the final product?" Everything that is becomes a raw material (A1/A2). Everything consumed during manufacturing stays as a process input (A3). This one pass prevents the most common EPD review comments.

Quick reference

In the product → raw material block (carries upstream production + transport)
Consumed to make it → process input (production impact only)
Water, energy carriers, and chemicals can be either — decide by role, not by substance
Added at multiple stages → one raw material block per stage; if the split is unknown, one block with the total
Never downgrade a real raw material to a process input — you lose its transport