What is life cycle assessment (LCA)?

Life cycle assessment (LCA) is a standardized method for measuring the environmental impact of a product, process, or service across its entire life — from extracting raw materials, through manufacturing and use, to end of life. It is the difference between guessing which option is greener and actually knowing, with numbers you can defend.

Instead of looking at a single number like energy use, an LCA accounts for the whole system: the steel in a pump, the electricity to run it, the fuel burned, the emissions to air and water, and what happens when it is retired. That full-system view is what stops a decision from simply moving a problem somewhere else — a “greener” material that is far worse to manufacture, or an electric vehicle on a coal-heavy grid.

The four phases of an LCA (ISO 14040 / 14044)

Every credible LCA follows the same four phases defined by the ISO 14040 and 14044 standards:

1. Goal & scope. Define what you are assessing, the functional unit (the “per what” — per litre treated, per kWh, per km), and the system boundary (how much of the life cycle is included).
2. Life cycle inventory (LCI). Build the ledger of every input (energy, materials, water) and every output (emissions to air, water, and soil) needed to deliver one functional unit.
3. Life cycle impact assessment (LCIA). Multiply those flows by characterization factors to express them as impact categories — global warming (kg CO₂e), acidification, eutrophication, water use, and more.
4. Interpretation. Find the hotspots (which stage or input dominates), test how sensitive the result is to assumptions, and draw a conclusion you can act on.

Key terms, in plain English

• Functional unit — the unit of service you compare on, so two options are weighed on equal terms.
• System boundary — cradle-to-grave (full life), cradle-to-gate (up to the factory gate), or cradle-to-cradle (crediting recycling).
• Inventory flow — a single input or emission, e.g. “1.2 kWh grid electricity” or “0.4 kg CO₂ to air.”
• Impact category — an environmental effect such as global warming, acidification, or water consumption.
• Characterization factor — the multiplier that converts a flow into an impact (e.g. methane = 27–30× CO₂ over 100 years under IPCC AR6).
• Allocation — how impact is split between co-products (milk vs meat, heat vs power).

Impact assessment methods

The LCIA step uses a published set of characterization factors. The common methods are EPA TRACI 2.1 (North America), EF 3.1 (the EU Environmental Footprint method), and ReCiPe (global), with IPCC global-warming potentials shared across all of them. FreeLCA uses TRACI 2.1 and IPCC AR6 today, plus inventory indicators for land and water use. See the methodology page for the full data sources per industry.

Why LCA matters

Big decisions — which treatment plant to build, which power source to back, which packaging or material to specify — increasingly need an environmental number next to the cost. Grant criteria, procurement rules, and climate commitments ask for it. LCA is how that number is produced in a way that is transparent and comparable rather than a marketing claim.

How long does an LCA take?

A full, third-party-reviewed study by a specialist can take weeks to months. But most real-world decisions don't need that — they need a credible comparison between a few alternatives. That is what template-based tools make fast: pick a starting point, change the numbers that matter, and read the result in about an hour.

Run a life cycle assessment for free

FreeLCA is free LCA software for everyone — 214 literature-sourced templates across water, energy, transport, waste, packaging, buildings, and food, on TRACI 2.1 + IPCC AR6 with US and international electricity grids. No license, no LCA degree required. You can see a worked example with no signup, read how the numbers are produced, or start your own assessment.

Frequently asked questions