What is life cycle assessment (LCA)?

Life cycle assessment — LCA — is a standardised method for measuring the environmental impact of a product or service across every stage, from extracting raw material to disposing of it as waste. Two words in that definition carry the weight: every stage and standardised.

It has to be every stage, because looking at one stage misleads. An electric vehicle has no tailpipe emissions in use; but manufacturing its battery carries markedly higher emissions than an internal combustion car’s. A comparison that looks only at use says zero emissions; one that looks at the life cycle tells the truth.

Why standardisation matters

There are infinite ways to measure environmental impact, and if everyone uses their own the results cannot be compared. ISO 14040 and ISO 14044 define how an LCA is done: which decisions must be made, how they are justified, and what the report must contain. These standards do not determine the result — they determine the method.

The four phases

ISO 14040 splits an LCA into four phases, carried out iteratively rather than in a straight line — each feeding back into the others.

• Goal and scope definition — What are you measuring, and why? The functional unit and system boundary are set here. The shortest phase, and the most decisive.
• Inventory analysis (LCI) — Counting every flow in and out of the system: energy, materials, emissions, waste. The most labour-intensive phase.
• Impact assessment (LCIA) — Translating hundreds of inventory flows into meaningful indicators such as climate change or acidification.
• Interpretation — What the results mean, how much they depend on which assumptions, and which decision they support.

The functional unit: the most misunderstood concept

LCA measures a function, not a product. That distinction changes everything. Measure a paint’s impact per litre and a paint with twice the coverage looks twice as bad. The right question is: what is the impact of protecting one square metre of surface for ten years? That definition is the functional unit, and it alone decides whether a comparison is fair.

System boundary: where it starts and ends

Every LCA has to stop somewhere. Three boundaries are common: cradle-to-gate (raw material → factory gate), cradle-to-grave (raw material → disposal) and cradle-to-cradle (a closed system where recycling feeds a new cycle). Which one was chosen must be stated explicitly — two numbers from different boundaries cannot be compared.

What LCA does not do

• It does not tell you which product is ‘better’ — it gives indicators; weighing them is your decision
• It does not measure local or momentary effects; the nuisance a plant causes its neighbour does not appear in an LCA
• It does not cover social and economic dimensions — S-LCA and life cycle costing exist for those
• It is not a permitting process and should not be confused with environmental impact assessment
• It does not produce one exact number — every result is read together with its assumptions and data quality

Where to start

Do not aim for perfection on your first LCA. Pick one product, narrow the boundary to cradle-to-gate, model the main materials and energy consumption, and see where the result concentrates. That first rough model tells you which data is worth collecting — and that is where LCA’s real value lies anyway.