LCA Engineering key terms

A way of reasoning that considers every stage of a product or service, from raw material extraction through production, use and end-of-life, so that improvements in one stage are not achieved by shifting burdens to another.

A structured technique for compiling and evaluating the inputs, outputs and potential environmental impacts of a product system throughout its life cycle, organised into four phases: goal and scope, inventory, impact assessment and interpretation.

A modelling approach that allocates a share of total environmental burdens to a product based on average existing supply chains, answering the question of what part of global impacts belongs to the product studied.

A modelling approach that estimates how environmental flows change in response to a decision, typically by modelling marginal suppliers and market-mediated effects rather than average supply-chain shares.

The unintended transfer of environmental pressure from one life-cycle stage, impact category, region or stakeholder to another when a system is changed, which LCA seeks to detect and prevent.

International standard that sets out the principles and framework for life cycle assessment, defining the four phases, their relationships and general requirements such as iterative working, transparency and reporting.

International standard that specifies detailed requirements and guidance for conducting LCA, including goal and scope definition, inventory analysis, impact assessment, interpretation, reporting and critical review conditions.

The first LCA phase, in which the intended application, reasons for the study, audience, product system, functional unit, system boundary, allocation rules, impact methods and data requirements are specified and documented.

A quantified description of the performance a product system must deliver, used as the reference basis to which all inputs, outputs and impacts are normalised so that alternative systems can be compared fairly.

The amount of product output required from a system to fulfil the functional unit, providing the physical link between the functional unit and the inventory data collected for that system.

A quantified amount of product, such as one cubic metre of concrete or one kilogram of steel, used as the basis for footprint or EPD results when the function is not comparable or cannot be fully described.

The set of criteria specifying which processes and flows are included in or excluded from the studied product system, such as cradle-to-gate or cradle-to-grave coverage and cut-off rules.

A system boundary covering the life cycle from raw material extraction up to the point where the product leaves the manufacturing site, excluding distribution, use and end-of-life stages.

A system boundary that includes all life-cycle stages: raw material extraction, production, distribution, use and end-of-life treatment such as recycling or disposal.

Specified quantitative or qualitative limits on mass, energy or environmental significance that determine which inputs, outputs and processes may be excluded from an inventory, with exclusions documented.

The partitioning of input or output flows of a multi-output process between the product system under study and other co-products, ideally avoided by subdivision or system expansion.

An allocation approach in which the system boundary is widened to include the additional functions provided by co-products, so that compared systems deliver equivalent functions and no partitioning is needed.

Any of two or more products or outputs produced by the same unit process, whose shared inputs and emissions must be partitioned or otherwise attributed among the outputs.

A negative burden given to a product system when one of its outputs displaces a conventionally produced alternative, credited at the avoided burden of the displaced product or material.

The LCA phase in which data are collected and calculations performed to quantify all relevant inputs of energy, materials and resources and outputs of emissions and wastes crossing the system boundary.

The smallest element of a product system for which input and output data are quantified, such as one production step at one facility, and which is linked to others to build the full model.

Measured quantities of material, energy or service use at a process, such as litres of fuel or kilograms of steel consumed, which are multiplied by emission or resource factors to obtain inventory flows.

Inventory information specific to the product system under study, collected from the operator's own facilities, suppliers or directly measured processes, in contrast to background data drawn from generic databases.

Inventory information taken from generic databases or literature for processes not directly controlled by the study, such as average electricity supply or commodity material production.

The LCA phase that translates inventory flows into potential environmental impacts using characterisation models, with mandatory steps of classification and characterisation and optional steps such as normalisation and weighting.

A class of environmental concern representing a specific environmental issue, such as climate change, acidification or freshwater ecotoxicity, to which inventory results are assigned and whose indicator is quantified.

A model-derived multiplier that converts an inventory flow into a contribution to an impact category indicator, for example the global warming potential of a greenhouse gas over a stated time horizon.

An impact measure located along the environmental mechanism between emissions and final damage, such as radiative forcing for climate change, retaining closer links to inventory flows but less relevance to end effects.

An impact measure expressed at the level of protection of areas of concern such as human health, ecosystem quality or resources, aggregating midpoint results through damage models and involving greater modelling uncertainty.

An optional LCIA step in which indicator results are divided by a reference value, such as regional or global emissions per person per year, to express their relative magnitude and aid interpretation.

An optional LCIA step that applies value-based factors to normalised or characterised results to aggregate them into a single score or ranking, reflecting subjective priorities that must be reported transparently.

A characterisation factor expressing the radiative forcing of a greenhouse gas over a chosen time horizon, usually 100 years, relative to carbon dioxide, which is assigned a value of one.

The LCA phase in which findings are analysed against the goal and scope through completeness, sensitivity and consistency checks, leading to conclusions, limitations and recommendations that are reported transparently.

A systematic procedure for testing how changes in key assumptions, data values, allocation choices or methodological choices affect the results, thereby identifying which parameters drive the conclusions.

A procedure for quantifying the variability or imprecision of inventory and impact results, for example through Monte Carlo simulation, so that ranges or confidence intervals can be reported alongside point estimates.

A documented evaluation of an LCA by an internal or external expert or panel, checking that the method follows the applicable standards, that data are appropriate and that conclusions are supported by the study.

The degree to which inventory data meet requirements for temporal, geographical and technological representativeness, completeness, precision and reliability, often assessed with a pedigree matrix and reported in the study.

A scoring tool that rates data on indicators such as reliability, completeness, temporal and geographical correlation, converting the scores into uncertainty factors used to estimate inventory uncertainty.

A compiled collection of unit process datasets with documented geography, technology and reference year, such as ecoinvent or GaBi databases, used to supply background data for modelling.

The sum of greenhouse gas emissions and removals expressed as carbon dioxide equivalent over the life cycle of a product, organisation or activity, calculated according to a defined scope and method.

International standard specifying principles, requirements and guidance for quantifying and reporting the carbon footprint of a product, based on LCA principles and including communication requirements.

A verified, standardised report presenting quantified life-cycle environmental information for a product, based on product category rules and intended for comparable communication between business customers or consumers.

A set of sector-specific rules, requirements and guidelines for developing an environmental product declaration for a product group, harmonising functional unit, boundaries, data and impact categories.

International standard establishing principles and procedures for Type III environmental declarations, covering programme operation, product category rules, verification and the content of declaration reports.

A voluntary, multiple-criteria, third-party certified label awarded to products meeting specified environmental leadership criteria within a product category, governed by the ISO 14024 standard.

A quantified environmental declaration providing life-cycle data for a product, verified by a third party and based on product category rules, of which the environmental product declaration is the main example.

An economic model that keeps materials and products in use for as long as possible through reuse, repair, remanufacturing and recycling, reducing primary resource extraction and waste generation.

The life-cycle stage after product use in which the product is collected and treated by recycling, energy recovery, incineration or landfill, whose modelling strongly influences overall results.

A benefit assigned in LCA modelling to account for avoided primary material production when a product's material is recycled, with the size and timing of the credit depending on the chosen allocation method.

The integration of environmental considerations into product design and development, using life-cycle information to reduce impacts across all stages while maintaining or improving product function and quality.

An assessment combining environmental LCA, life cycle costing and social life cycle assessment to evaluate the three pillars of sustainability for a product system, ideally using a consistent functional unit and boundary.

A situation in which improving one impact category or life-cycle stage worsens another, requiring explicit weighing of options and transparent reporting rather than a single unqualified conclusion.