Life Cycle Assessment (LCA) methodology: methods and tools

Life Cycle Assessment (LCA) is the benchmark methodology for objectively and quantitatively evaluating the environmental impact of products, processes, and services across all their stages, from raw material extraction to end of life. This holistic view makes it possible to locate the critical points where the greatest environmental burdens are concentrated and to take data-based improvement decisions.

This guide explains how LCA methodology is structured according to the ISO standards, what impact assessment methods exist, and what software is used in practice.

What standards is LCA methodology based on?

LCA relies on two complementary international standards: ISO 14040, which defines the principles and general framework, and ISO 14044, which sets out the detailed requirements and guidelines. Together they ensure the transparency, consistency, and comparability of studies. For the product carbon footprint there is also ISO 14067, which applies LCA principles to a single impact category: climate change.

The four phases of an LCA

The ISO methodology structures every LCA into four phases:

1. Goal and scope definition: the purpose of the study is set, along with the functional unit (for example, 1 kg of product or 1 km travelled) and the system boundaries.
2. Life cycle inventory (LCI): all input and output flows are gathered (materials, energy, water, emissions, waste).
3. Life cycle impact assessment (LCIA): the inventory data are translated into impact categories (climate change, eutrophication, toxicity, etc.).
4. Interpretation: the results are analysed, critical points are identified, and improvements are proposed.

The inventory and the impact assessment are usually the most time-consuming phases, because they depend on the availability and quality of the data.

Impact assessment methods: which one to choose

An impact assessment method is the set of characterisation factors that converts inventory data into comparable environmental indicators. The most widely used are:

• Environmental Footprint (EF) 3.1: the official method of the European Commission and the basis of the Product Environmental Footprint (PEF). It is the reference when comparability within the EU is the goal.
• ReCiPe 2016: a widely used method that provides indicators at both midpoint and endpoint (damage) level, covering categories such as climate change, human toxicity, ecotoxicity, or land use.
• IMPACT World+: allows impacts to be assessed at global and regional scales, useful when factors such as resource depletion or water scarcity matter.
• TRACI: developed by the US EPA, suited to studies with a North American focus.

The choice of method depends on the objective, the target market, and the reference framework. For a European Environmental Product Declaration (EPD), EF 3.1 facilitates comparability; for a product carbon footprint, the climate change category is enough.

Software for carrying out an LCA

Apart from very basic approximations, a rigorous LCA requires specialised software and inventory databases. The best-known tools on the market are:

• SimaPro: one of the most widespread professional LCA platforms.
• Sphera LCA for Experts (formerly GaBi): a reference software in industrial environments.
• OpenLCA: a free, open-source tool that is combined with paid databases.

The quality of the result depends largely on the inventory database. The most widely used is Ecoinvent; for the agri-food sector, Agribalyse or Agri-footprint are also common. In addition to specialised software, management platforms such as Manglai's product footprint make it possible to structure and automate data collection and connect it with corporate reporting.

Step-by-step process for carrying out an LCA

1. Define goal and scope: determine the purpose, the functional unit, and the system boundaries (for example, cradle to gate or cradle to grave).
2. Gather the inventory: prioritise primary data measured on site and complement them with recognised databases.
3. Select the impact method: choose between EF 3.1, ReCiPe, IMPACT World+, or others, depending on the objective.
4. Model the life cycle in the software: enter the data and build the process model.
5. Interpret the results: identify the critical points and the improvement opportunities.
6. Communicate: produce clear reports and, where appropriate, submit the study to critical review before publishing it.

Common barriers and how to tackle them

• Lack of supplier data: include data-provision clauses in purchasing contracts and start with well-documented secondary data.
• Software complexity: begin with simple models and add detail in layers.
• Licence cost: one option is to combine OpenLCA with paid databases only for the critical stages.

Good practices that save time and reduce errors

It is advisable to draw a flow diagram of the system from day one, prioritise primary data in the processes that concentrate most of the impact, and check the consistency of the model with a mass and energy balance between inputs and outputs. Documenting every assumption makes it easier to carry out the critical review required by ISO 14044 when the study is published.

Frequently asked questions about LCA methods and tools

Which impact method does ISO 14044 require?

The standard does not require a specific one; it requires you to justify the choice. Methods such as EF 3.1 or ReCiPe meet its requirements.

Can I work with secondary data only?

Yes for initial approximations, but it increases uncertainty. A public EPD requires a relevant share of primary data and a critical review.

How do I link water footprint and LCA?

A water footprint under ISO 14046 is a water-focused LCA. You can integrate it with the water resources module of the impact method or calculate it separately, as explained in the article on the blue water footprint.

Do I need technical experience to use these tools?

Yes, advanced software requires training, although simplified calculators exist for a first approximation.

Can I carry out an LCA without specialised software?

Only for very basic estimates. For rigorous, comparable, and publishable results, software is essential.