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Life cycle assessment (LCA) Definition

A life cycle assessment (LCA) estimates a product's or service's potential environmental impacts for a defined function and life-cycle boundary, using recorded inputs, stated impact methods, and a documented interpretation of the results.

What is a life cycle assessment?

An LCA evaluates potential environmental impacts tied to a product or service across the life-cycle boundary you define. ISO 14040:2006 organizes an LCA into four phases: set the goal and scope, build the life cycle inventory (LCI), calculate environmental impacts, and interpret the findings. The goal names the intended use and audience. The scope states the function being measured, the included life-cycle stages, the data needed, and the impact methods used.

The LCI counts material, energy, transport, waste, and emission flows for that functional unit. The life cycle impact assessment (LCIA) applies an impact model to those flows, for example converting greenhouse gases into a climate-change result. Interpretation checks whether missing data, method choices, or inconsistent inputs could change the conclusion. A product carbon footprint is narrower because it reports only GHG impact, usually in kg CO2e per functional unit.

Why does a life cycle assessment matter to you?

A customer may ask for a product or service footprint to improve its Scope 3 Category 1 purchased-goods-and-services data. The request can require the functional unit, cradle-to-gate or cradle-to-grave boundary, primary-data share, factor sources, allocation, exclusions, and review status. Unilever's 2025 Sustainability Statement says validated supplier PCFs submitted through its Supplier Climate Programme followed PACT and entered its Scope 3 calculation; the Keslio Unilever supplier guide covers the request context.

PACT Methodology V3 covers cradle-to-gate product carbon footprints and includes service-based businesses. Its June 2026 page says V2 is withdrawn for new calculations, so record the method and revision instead of using an undated spreadsheet.

How does a life cycle assessment work?

Start with one measurable function. For a cleaning service, this could be "maintain 10,000 m2 of office space to the contract specification for one month." Map the chemicals, water, equipment energy, travel, waste, and flows needed to deliver it. State the geography, period, service quality, life-cycle stages, and reference flow before collecting quantities.

Then collect process data, match each quantity to a factor or impact model, allocate shared processes on a stated basis, and total each impact per functional unit. GHG Protocol Product Standard chapters 6 and 7 require a functional unit for final products, all attributable processes, a process map, and justified exclusions. Chapter 8 requires primary data for processes you own or control and a data-quality assessment.

What mistakes should you avoid?

  • Using company-wide annual electricity as the service result without allocating it to the functional unit.
  • Comparing options with different functions, service lives, boundaries, geographies, data years, or impact methods.
  • Calling a cradle-to-gate GHG total a full LCA, or presenting kg CO2e as proof that every environmental impact improved.
  • Dropping an attributable chemical, trip, or waste flow without the GHG Protocol Chapter 7 estimation and disclosure record.

Is an LCA the same as a product carbon footprint?

No. A product carbon footprint applies life-cycle methods to one impact, climate change, and reports GHG emissions in CO2e. An LCA can assess several environmental impacts. If a request says PCF, give the climate result, functional unit, boundary, and method rather than only a multi-impact LCA report.

Does an LCA always cover cradle to grave?

No. The goal and method determine the boundary, but you must label a partial study. Under GHG Protocol Product Standard Chapter 7, a conforming final-product inventory covers cradle to grave, while a justified cradle-to-gate inventory for an intermediate product excludes use and end-of-life results.

What should you send when a customer asks for an LCA?

Start with the goal, audience, functional unit, reference flow, process map, boundary, life-cycle stages, geography, and period. Attach the quantities and source files, factor or database versions, allocation equations, exclusions, and impact results per unit. Add the sensitivity findings and critical-review or assurance status so the customer can reproduce the result and see its limits.

Worked example

Suppose a facilities-services company in Dubai tests the climate-change result for one functional unit: cleaning and maintaining 10,000 m2 of office space to the contract specification for one month. The first calculation covers allocated equipment electricity and service-vehicle diesel. It excludes cleaning chemicals, water, waste, equipment manufacture, and end-of-life, so it is an incomplete result, not a finished LCA or cradle-to-grave product carbon footprint.

Shared cleaning equipment uses 500 kWh during the month, and vehicle records show 60 litres of diesel across all contracts. Timesheets allocate 40% of equipment hours and vehicle logs allocate 25% of fuel use to this contract. The functional unit therefore receives 500 kWh x 40% = 200 kWh and 60 litres x 25% = 15 litres.

For electricity, the Keslio factors dataset uses 0.3833 kg CO2e/kWh from the DEWA Sustainability Report 2025. This is a Dubai grid proxy for the United Arab Emirates. For diesel, it uses 2.58354 kg CO2e/litre from the UK DESNZ and DEFRA Government GHG Conversion Factors for Company Reporting 2026. The diesel value is disclosed as a United Kingdom proxy because the dataset has no UAE-specific diesel factor.

Climate-change calculation: 200 kWh x 0.3833 kg CO2e/kWh = 76.66 kg CO2e. Then 15 litres x 2.58354 kg CO2e/litre = 38.7531 kg CO2e. The partial total is 115.4131 kg CO2e per 10,000 m2-month, or 0.01154131 kg CO2e per m2-month. Before calling this an LCA result, the company must add every attributable process and each selected impact category. It should also recalculate the result with a second defensible allocation basis, such as contract hours, and report how much the result changes.

Where you'll meet it

GHG Protocol functional unit and reference-flow requirements for final and intermediate productsProduct Life Cycle Accounting and Reporting Standard, Chapter 6, section 6.2 and Table 3.1Official sourceGHG Protocol boundary, process-map, life-cycle-stage, and exclusion requirementsProduct Life Cycle Accounting and Reporting Standard, Chapter 7, section 7.2 and Table 3.1Official sourcePACT cradle-to-gate product carbon footprints and service-based business methodPACT Methodology V3, scope and version noticeOfficial sourceUnilever supplier PCFs following PACT and LCA-based cradle-to-gate factors for Scope 3 Category 1Unilever Sustainability Statement 2025, Supplier Climate Programme on page 227 and Category 1 methodology on page 231

Related terms

Product carbon footprint (PCF)

A product carbon footprint (PCF) is the greenhouse gas emissions assigned to one product across a stated life-cycle boundary and expressed per declared or functional unit.

Scope 3 Emissions

Scope 3 emissions are the indirect greenhouse gas emissions from goods, services, transport, product use, investments, and other upstream and downstream activities outside your company's Scope 1 and Scope 2 boundary.

Emission factor

An emission factor converts a measured activity, such as kilowatt-hours of electricity or litres of fuel, into greenhouse gas emissions by stating the emissions released per unit of that activity.

Carbon Accounting

Carbon accounting is the process of defining a company’s greenhouse gas inventory, collecting activity data, applying emission factors, and reporting Scope 1, Scope 2, and Scope 3 emissions on a consistent basis.

Sources

  • International Organization for Standardization

    ISO 14040:2006 goal and scope, LCI, LCIA, interpretation, reporting, critical review, and limitations

    2026-08-19

  • GHG Protocol

    Functional units, reference flows, product boundaries, process maps, exclusions, data quality, allocation, calculation, assurance, and reporting

    2026-08-19

  • Unilever

    Supplier PCFs following PACT and LCA-based cradle-to-gate factors used for Scope 3 Category 1

    2026-08-19

Last verified 2026-08-19

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Life cycle assessment (LCA) Definition | Keslio