Life Cycle Assessment (LCA): definition and principles

Life Cycle Assessment(LCA) is an essential methodology for evaluating theenvironmental impact of a product, service or project throughout its life cycle. The method is recognized for its scientific robustness, and is the benchmark for implementing aneco-design strategy.

What is LCA (Life Cycle Assessment)?

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LCA aims to identify the environmental impacts of a product compared to a situation in which this product would not exist. It is based on a dual life-cycle and multi-criteria approach.

💡 Did you know? Historically, the first work on LCA dates back to the 1960s. It was the Coca Cola company that developed this methodology to find a way to reduce the energy consumption of its manufacturing process.

LCA has since been ISO-standardized in 1997 and updated in 2006. ISO 14040 and ISO 14044 are the current standards governing LCA.

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A lifecycle approach

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LCA assesses the impact of all stages in a product's life cycle. 

The entire life cycle of a product is analyzed during an LCA. The life cycle of a product is composed of 5 phases:

• Raw materials: extraction, processing, supply
• Manufacture of the finished product: assembly, packaging, construction, etc.
• Distribution: marketing, delivery, etc.
• Use: consumption, maintenance, etc.
• End-of-life: collection, transport, recycling, waste treatment, etc.

A multi-criteria approach

LCA makes it possible to determine the environmental impact of a product in terms of various indicators, and is not restricted to greenhouse gas emissions measured in kgCO2eq. There are some forty indicators, but generally around fifteen are analyzed. A distinction is made between "mid-point" and "end-point" impact categories:

Mid-point

These are indicators measuring environmental problems such as water acidification. These indicators are designed to help product designers reduce their impact.

End-point

These are indicators that measure environmental damage, such as biodiversity loss. These indicators are intended for use by decision-makers in implementing more global policies.

End-points are the consequences of mid-points: water acidification increases the mortality of certain fish species, thus reducing biodiversity. This is why, for ecodesign purposes, most of the indicators used in LCA fall into the "mid-point" category.

Thanks to this dual approach, LCA differs from other environmental methods such as Bilan Carbone or energy audits. In fact, such an approach makes it possible to avoid transferring impacts during product design.

A transfer of impact occurs when a decrease in impact on one life-cycle stage occurs at the expense of an increase in impact on another stage. Impact transfer can also occur when a decrease in impact on one indicator leads to an increase on another.

💡 Let's take the example of a T-shirt: synthetic fibers from the petrochemical industry are regularly used as raw materials, but their manufacture emits large quantities of CO2eq. To avoid these emissions, these fibers can be replaced by cotton, which emits far less CO2eq. However, cotton production requires high water and pesticide consumption. Here we see a transfer of impact from one indicator, greenhouse gas emissions, to the other, water consumption and pollution.

How tocarry out an LCA?

An LCA of a product is carried out in 4 interdependent stages.

1. Definition of objectives and assumptions

Before any measurements are taken, the objectives of the analysis must be determined: is the LCA being carried out for communication purposes? for eco-design? for comparison with a competitor's product? The assumptions to be made depend heavily on these objectives. The results of an LCA depend largely on these assumptions, which is why the objectives must be precisely defined to reduce the uncertainty arising from the assumptions.

Functional unit

In the same way that a consumer compares the price of two fruits on a per kilo basis, to compare the environmental impacts of two products, we reduce the impacts to a common unit of measurement. The functional unit is "the unit of measurement used to assess the service rendered by the product", according to ADEME. It must be precise, measurable and additive, and must answer the questions "what", "how much", "how" and "how long".

💡 For example, for a t-shirt, we can propose the following functional unit: "wear and wash a t-shirt 1 day a week for 3 years".

System boundaries

The next step is to define the scope of the product study. This scope depends on the objectives set beforehand. The two most frequently studied perimeters are :

• Cradle-to-gate: the stages concerned are raw materials extraction through to the factory gate. Distribution, use and end-of-life stages are not taken into account.
• Cradle-to-grave: the stages involved are the extraction of raw materials, their transformation, distribution, use and disposal or recycling.

2. Life cycle inventory

The life cycle inventory stage consists of listing all the materials and energies consumed (cotton, wood, biogas, electricity, etc.) and emitted (CO2, pollutants, thermal energy, etc.) throughout a product's life cycle. These are known as input and output flows. There are two types of data:

• Primary data: this is observed or measured data. For example, the mass of cotton used to manufacture a T-shirt.
• Secondary data: calculated, hypothetical, averaged data. For example, average electricity consumption per T-shirt in the weaving mill.

The life cycle inventory is the most complex stage in a life cycle analysis. Indeed, it is necessary to be able to collect precise data on a product's entire value chain. It is therefore necessary to talk to suppliers in order to obtain this data, as well as to know the use and end-of-life scenarios for your products.

3. Environmental impact assessment

Based on the life cycle inventory (LCI), each flow is associated with impact factors taken from databases (Ecoinvent, Base Impacts, ILCD, etc.). Various impact calculation methods (ReciPe, CML, etc.) link flows and impact factors to obtain results for each impact indicator. Depending on the method chosen, "mid-point" or "end-point" impacts are obtained.

4. Interpretation of results and analysis

Assumptions and uncertainties

This last stage is crucial in an LCA. It involves checking the consistency of the results by testing the sensitivity of the assumptions. It is necessary to interpret the results obtained in the light of this sensitivity, and to add the equivalent uncertainties.

Critical review

For internal use or even external communication, LCA does not need to be standardized. For ISO certification, however, a critical review must be carried out by independent experts, who must check the consistency of assumptions and the reliability of data used. A critical review is particularly advisable when comparing a product with a competing solution.

Adding value to your LCA

Once this interpretation stage has been completed, the results of the LCA can be used to communicate the environmental impact of the product to the consumer, or to implement an eco-design approach to reduce this impact.

What software is needed to carry out an LCA?

Most LCA software programs can be used to define all the flows in and out of a product, and thus to draw up a life-cycle inventory. These include high-performance software designed for LCA experts, such as SimaPro, Gabi and OpenLCA. Other software, such as Waro, aims to make LCA easier by applying the methodology in a rigorous way, while simplifying the user experience. The aim is to break down the technical barriers that separate the worlds of business and LCA.

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