LCA glossary

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Life cycle assessment (LCA)

Compilation and evaluation of the inputs, outputs and potential environmental impacts of a product system throughout its life cycle. Framework in ISO 14040, requirements in ISO 14044.

Life cycle

The consecutive and interlinked stages of a product system, from raw material acquisition through production, distribution and use to end of life.

Product system

The collection of unit processes that performs one or more defined functions and models the life cycle. It is what an LCA studies — not the product on its own.

Unit process

The smallest process element for which inventory data is collected (e.g. mixing, kiln, packaging). The building block of the model; cut-off criteria are applied per unit process.

Goal and scope definition

The first phase of an LCA: why and for whom the study is done, the functional/declared unit, system boundary, cut-off criteria, allocation approach, impact categories, data-quality requirements and limitations are written down here.

Functional unit

The quantified performance of a product system used as the reference unit for results (e.g. covering 1 m² of surface for 50 years at a given performance). A comparison is meaningful only when the function is the same.

Declared unit

A quantity reference used when no function is defined (e.g. 1 tonne, 1 m³, 1 m²). Common in EPDs under EN 15804; not to be confused with the functional unit.

Reference flow

The amount of product needed to deliver the function defined by the functional unit (e.g. the kg of product required to cover 1 m²).

System boundary

The boundary that decides which unit processes are part of the product system. Terms such as cradle to gate and cradle to grave describe the system boundary.

Cradle to gate

Scope from raw material acquisition to the product leaving the factory gate. Modules A1–A3 in the EN 15804 module structure.

Cradle to grave

Full life-cycle scope from raw materials to end-of-life disposal. Modules A–C in EN 15804 (D is reported separately).

Life cycle modules (A1–D)

The stage blocks EN 15804 defines for construction products: A1–A3 production, A4–A5 construction, B1–B7 use, C1–C4 end of life, D benefits and loads beyond the system boundary.

Cut-off criteria

The rule deciding which minor inputs/outputs may be neglected. EN 15804+A2: 1% of mass and of primary energy per unit process, 5% in total per module; environmentally significant flows may not be neglected.

Life cycle inventory (LCI)

The second phase of an LCA: collecting the inputs and outputs of the product system (materials, energy, emissions, waste) per unit process and scaling them to the functional unit.

Primary (specific) data

Data measured at or taken from the records of the plant or supplier (meters, invoices, production reports). It is the data whose traceability is questioned in EPD verification.

Secondary (generic) data

Data taken from background databases or literature, not specific to the plant (e.g. grid mix, raw-material production). Documented with name, version and geography.

Background data

Data for processes outside the manufacturer's control (raw-material production, energy, transport, waste treatment); mostly from secondary databases.

Foreground data

Data for the processes at the focus of the study, under the manufacturer's direct control; mostly primary data.

Reference year

The period the plant data belongs to. Consumption and production must belong to the same reference year; EPD programmes set limits on how recent the data must be.

Allocation

Sharing the inputs and outputs of a multi-product process between its products. The ISO 14044 order: avoid first (subdivision / system expansion), then physical relationship, and only then other relationships (e.g. economic).

System expansion

One way of avoiding allocation: including in the system boundary the function the co-product displaces. Its use in attributional EPD studies is limited by the PCR.

Co-product

A second product with economic value leaving the same process. Its distinction from waste is defined in EN 15804+A2 and decides how allocation is done.

Life cycle impact assessment (LCIA)

The third phase of an LCA: converting inventory results into impact categories with characterisation factors.

Impact category

A class of environmental issue to which inventory results are assigned: climate change, acidification, eutrophication, ozone depletion, resource depletion and so on.

Characterisation factor

The coefficient that converts an inventory flow into an impact-category indicator (e.g. 1 kg CH₄ → x kg CO₂e). The method and version used are part of the result.

Global warming potential (GWP)

The climate-change indicator in kg CO₂ equivalent. EN 15804+A2 requires four separate values: GWP-total, GWP-fossil, GWP-biogenic and GWP-land use and land use change.

Biogenic carbon

Carbon of biomass origin (e.g. wood, paper). Under EN 15804+A2 its uptake and release are tracked separately under GWP-biogenic; it is not used as a credit or offset.

Environmental Footprint (EF) method

The impact assessment method and characterisation set developed by the European Commission's JRC. The core indicators of EN 15804+A2 are based on it.

Interpretation

The fourth phase of an LCA: identifying significant issues (hotspots); completeness, sensitivity and consistency checks; conclusions, limitations and recommendations.

Hotspot analysis

The analysis showing which material, process or module the total impact comes from. The output a manufacturer can actually act on.

Sensitivity analysis

A check showing how much the result changes when one assumption or data point is changed. Different from uncertainty analysis; one variable is moved at a time.

Data-quality requirements

The characteristics ISO 14044 requires to be defined in the scope phase: time-related, geographical and technology coverage; precision, completeness, representativeness, consistency, reproducibility, sources and uncertainty.

Critical review

An independent assessment of whether an LCA study conforms to ISO 14040/44. Mandatory as a panel review for comparative assertions disclosed to the public. A separate mechanism from EPD verification.

Comparative assertion

A claim of environmental superiority or equivalence of one product over a competing product. Subject to additional requirements and a critical review panel under ISO 14044.

Attributional LCA

The approach that describes the flows and impacts "belonging" to a product system over its life cycle. EPDs use the attributional approach.

Consequential LCA

The approach that models how a decision changes processes outside the system. Used in policy analysis; not suitable for EPDs.

Product category rules (PCR)

The document setting the rules for preparing an EPD for a product group (declared unit, modules, scenarios, data requirements). EN 15804 is the core PCR for construction products; operators publish complementary PCRs (c-PCR).

Environmental product declaration (EPD)

A Type III environmental declaration presenting LCA results in a standard format under a PCR, independently verified and published by a programme operator (ISO 14025).

Product carbon footprint (PCF)

The sum of greenhouse gas emissions and removals of a product system over its life cycle, in CO₂e (ISO 14067). The climate dimension of an LCA only.

Scenario

The documented set of assumptions, made according to the PCR, for stages outside the manufacturer's control (transport, use, end of life). Module C and D results depend on the scenario.

Module D

Net benefits and loads beyond the system boundary from reuse, recovery and recycling. Reported separately under EN 15804+A2; not added to the A–C total.