The Life Cycle Assessment (LCA) is the most common methodology for assessing the potential environmental impacts associated with the entire life cycle of a product. With the rising concern for environmental issues worldwide, more and more businesses are conducting an LCA on their key products. Keep reading as we’ll show you how to do an LCA

The rulebooks: ISO 14040 & ISO 14044

In an attempt to standardize how to do an LCA, the International Organization for Standardization (ISO) developed ‘Principles and framework’ (ISO 14040) and ‘Requirements and guidelines’ (ISO 14044). 

This article is based mostly on these two ISO standards which can be difficult to read. We hope this page will make it much easier and faster to understand how to do an LCA.

Note: we inserted Chinese characters in order to make it easier to communicate on this topic with Chinese suppliers, who sometimes have great difficulty understanding these topics.

What is a product's life cycle?

We drew a simplified graph about a product’s life cycle below:

product lifecycle image

It starts with the product design. Designers have a lot of control and/or influence over the impact of the product. They pick the materials, they pick the manufacturing processes, but also have multiple ways to make the product last longer, to make it easier to maintain, to enable recycling of some of its components, and so on.

After that, all the physical steps, from raw material extraction all the way to what happens after the product is no longer in use, are listed. Each of those steps may have an important impact on the environment.

The 4 phases in a Life Cycle Assessment [生命周期评估] study

An LCA always follows this sequence:

  • 1. Goal and scope definition phase [目标与范畴界定單元] – to understand and clearly state the purpose of this study, the target audiences, and the intended use of the result (e.g. will it be used for the public to be able to compare the impact of 2 products?). The depth and width of the scope vary depending on the goal. 
  • 2. Life cycle inventory (LCI) analysis phase生命周期盘查分析單元 – to quantify and collect all the necessary input/output data (e.g. the mass of materials, energy consumption, CO2 emission) regarding the system being studied.
  • 3. Life cycle impact assessment (LCIA) phase 生命周期冲击评估單元 – to provide additional information to help evaluate the LCI results of the product system, in order to better understand their environmental significance.
  • 4. Life cycle interpretation phase 生命周期阐释單元 – to summarise and interpret the results of the LCI and the LCIA for conclusions, recommendations, and decision-making.
Source: ISO 14040:2006 – Environmental management — Life cycle assessment — Principles and framework, 4.2.3

Let’s look at these 4 phases in more detail:

lca lifecycle assessment framework
Figure 1 – Stages of an LCA

Phase 1: Goal and scope definition phase


Do you want to have an idea of a product’s impact on the environment? But why?

  • Do you want to work on improvement, for example, make the next generation of your product more eco-conscious by acting on the largest sources of impact of your current products?
  • Do you want to evaluate if certain products are more or less harmful to the environment than other products? (In that case, the goal is “comparative assertion”, which is defined in ISO 14040 as “the environmental claim regarding the superiority or equivalence of one product versus a competing product that performs the same function”.)
  • Do you need to comply with a request for information from a customer?
  • Do you need to comply with a certain regulation?
  • Is it something else?

System Boundaries

The system boundary determines the set of criteria specifying which unit processes [单元过程] are included in the LCA, and which are excluded (what are the cut-off criteria?). It must be consistent with the goal and scope of the study. 

A nice graphic about the scope

Here is a nice way to look at the ‘unit processes’ and what to include in the scope of the assessment, without going into all the small details:

unit processes included in lca scope
Source: Bossagh, Iman & Hassanzadeh, Majid. (2012). LCA-Introduction.

Common boundaries for LCA – From cradle to grave [从摇篮到坟墓]

The widely used “cradle to grave” boundary is a requirement both in ISO 14040 and ISO 14044. It includes all stages of a product’s lifecycle, from resource extraction to end-of-life. Both upstream (e.g. suppliers) and downstream (e.g. waste management) processes associated with the production (e.g., production of raw, auxiliary, and operating materials), use phase, and final disposal (e.g. recycling, waste incineration). 

Can one decide to skip some sections of the product life cycle?

Not if those sections may have a significant impact on the environment. ISO 14044 makes this clear: 

“The deletion of life cycle stages, processes, inputs or outputs is only permitted if it does not significantly change the overall conclusions of the study. And the omission shall be clearly stated and explained.”

Other boundaries to be considered

  • Boundaries in relation to other products’ life cycles: co-products (which are made at the same time as the product being studied); materials recycling/reusing in other products). You may have to set up allocations (i.e. the partitioning and relating of inputs and outputs of a process to the relevant products and by-products).
  • Geographical boundaries– e.g. to take into account environmental laws and regulations from different countries. 
  • Time boundaries – e.g. new and old technologies and production methods.
  • Boundaries in relation to capital and personnel – e.g. staff transportation, consumption of food and drink. 

How to decide what to include? Refer back to the goal and the scope of the assessment, and it should be relatively obvious.

And what if you are still unsure? Always use a sensitivity analysis [敏感性分析]  (also called ‘What-If analysis’) to determine the significance (and potential impact) of the elements to include or exclude. If an element is quite unlikely to have a medium or large impact, excluding it is usually no problem.

Going deeper into the scope definition

If you need to do an LCA now, you will need to follow the steps we explained below. Otherwise, if you just want to have an overview of what an LCA includes, skip to phase 2.

🚨 WARNING, the remainder of phase 1 is quite dry and technical… ⚠️ 

Define the function(s) of the ‘product system’

The ‘functions’ (in other words, the performance characteristics) of the system being studied shall be specified in the scope of LCA. It helps clarify what data to collect and how to do calculations.

Scenario: A wood door manufacturer is preparing a proposal for a government housing estate tender. The estimated carbon footprint of each door needs to be suggested in the proposal.

carbon footprint for wooden doors estimate

Without specifying the function(s), this company would simply calculate the average footprint per door, as follows:

carbon footprint calculation

However, that is the wrong approach. They will miss two important topics, with examples.

a) They cannot see positive impact

This company produces all kinds of doors in different types of wood and, in most cases, it does not check if the source is sustainable. Regarding this tender, the company takes the first eco-step and finds new FSC-certified suppliers for this project. The carbon footprint of material extraction will be lower than their average.

b) They cannot see negative impact

This company usually sells the doors to local markets (mostly about 10 miles away). In this tender, the doors will be shipped 100 miles away for installation. The CO2 footprint for transportation will be higher than the average.

In other words, it is important to focus only on what is in that “product system”:

In the case of comparative studies, specifying the functions allows various products/systems to be compared based on similar function(s). Many products are multi-functional; when their secondary functions differ a lot, the validity of the comparison becomes questionable. (For example, it is unfair to compare the battery duration of a ‘smartphone’ with that of a ‘feature phone’ with a much smaller display).

cell phone feature comparison

‘Functional Unit’ and ‘Reference Flow’ 

The purpose of a functional unit is to quantify the system function, to define it clearly, to meet the goal and scope of the LCA, and to be measurable. 

If the objective is to allow the comparison between 2 products/systems/services, their functional units must be equivalent. 

‘Reference flow’ is the measure of product components and materials needed to fulfil the function, as defined by the functional unit.

Let’s take an example: a comparison between plastic disposable straws and stainless-steel straws:

a comparison between plastic disposable straws and stainless-steel straws

‘Functional Units’ indicate the environmental impact per unit of service. When selecting functional units, be careful to choose the unit of service to allow fair comparisons between the products. From the above example, if you just want to compare the environmental impact of a disposable plastic straw vs. a stainless-steel straw in 1 cup of serving, the plastic one probably comes with a lower impact, but that is misleading since stainless steel can last for a longer time and be used hundreds of times.  

The harsh reality: an LCA always tends to suffer from limitations related to its boundaries

Even when following the two above-mentioned ISO standards, the results of an LCA on the exact same product can vary a lot because of different practitioners’ biases and assessment approaches. Here are common examples:

  • They might set boundaries that are not very clear
  • They might double count the collected data
  • They might overlook co-products (made at the same time in the same processes)
  • They might assume that some components are recycled into the same product (closed loop) or into other products (open loop)

Phase 2: Life cycle inventory (LCI)

This phase’s purpose is to collect and calculate all quantitative and qualitative data that represent the environmental impacts in every unit process of the selected system boundaries. 

Gathering all the data into one table

After all the process-related data is collected, an inventory table for the whole product system is created. It is usually shown as a table listing all the material and energy inputs and outputs for the system. The data is usually classified under major headings, including 

  • energy inputs, raw material inputs, ancillary inputs, other physical inputs, 
  • products, co-products and waste, 
  • emissions to air, discharges to water and soil, and 
  • other environmental aspects

Here is what standard ISO 14044 suggests in annex B:

Data collection

The LCI phase sounds simple in theory but is complicated in practice. 

When collecting the data, some data on materials or processes that are involved in the product’s lifecycle are often not available. For instance, a manufacturing plant may not know anything about the extraction of raw materials, the transportation of materials, or the ways consumers use and dispose of the product. Facing uncertainty, the factory often has to use the data available, make reasonable assumptions, and estimate the best item or combination of items as a substitute. 

The good news is, many LCI databases are now available in the market or are provided by the local government. Those databases help industries measure their environmental footprint. 

Tip: always run multiple sensitivity analyses with different substitutions to see how sensitive the results are based on your different assumptions. Spend more time refining your data when a change in data leads to a large charge in the impact.

Dividing the work between a manufacturer and a customer

This has to be done quite often. There are many cases where no one party knows everything, so a realistic approach is to divide the work. 

Let’s take an example:

  • The customer in Europe has designed the product.
  • A manufacturer in Asia purchases components (already fabricated) and assembles them
  • The manufacturer has no visibility beyond their own direct (tier-1) suppliers
  • The customer manages transportation from the Asian factory

What data will each party provide? It may look like this:

LCI data provided by manufacturer and customer

What about the data about the environmental impact of raw material extraction, processing, etc.? Specialized LCA software usually has databases that allow a rough assessment of their impacts, as we mentioned above.

And what data will the customer need to provide? The data about all the processes after assembly. Let’s take Apple, for example. They have data about product usage (how many iPhones are still in use, get software upgrades, get a repair, etc.) and they collect some old iPhones for recycling or trade-in & refurbishment. Unfortunately, many companies work with much more limited data and they need to make rough estimates.

Data Quality

The quality of data has a large influence on the results of the LCA study. It is good to determine data quality at the beginning of the study. Assessing the data quality can only be done when the data quality characteristics and requirements are sufficiently documented. 

The following should be considered when it comes to data quality: 

  • Source of data: do the data come from primary sources (first-hand measurements), or secondary sources (from literature/databases)? Do they come from a reliable source or a rough estimation? 
  • Time-related coverage (age of data): when were the data collected? Any major changes that may affect the result? 
  • Geographical coverage: for what country or region is this data relevant? 
  • Technology coverage: was the data collected by outdated technology?
  • Precision: are the data a precise representation of the system? 
  • Completeness: are any data missing? How are data gaps filled? 
  • Representativeness, consistency, reproducibility and uncertainty of the information.

Phase 3: Life cycle impact assessment (LCIA)

Impacts considered in an LCIA phase include all relevant inputs from the environment (e.g., ores and crude oil, water, land use) as well as outputs (emissions into the air, water and soil). 

The main categories of outputs include climate change, ozone depletion, eutrophication, acidification, human toxicity (cancer and non-cancer related) respiratory inorganics, ionizing radiation, ecotoxicity, photochemical ozone formation, land use, and resource depletion. 

The mandatory and optional elements of the LCIA phase mentioned in ISO 14040:2006 are as below:

life cycle impact assessment phases
Source: ISO 14040:2006 – Environmental management — Life cycle assessment — Principles and framework, 5.4.2 

Phase 4: Life cycle interpretation

In this phase, the significant issues are identified based on the results of the LCI and LCIA phases. 

They are checked and evaluated to see if their completeness, sensitivity, and consistency meet the goal and the scope definition. 

The goal of the life cycle interpretation phase is to draw conclusions,  identify limitations, and make recommendations for the intended audience of the LCA. 


ISO 14044 requires full transparency in terms of values picked, rationales, and expert judgments. The results of the LCI and LCIA, as well as all data, methods, assumptions, and limitations, shall be presented in a clear, transparent, structured and sufficiently detailed manner. 

If the LCA’s goal is to allow for comparison between different products, the ISO standards (14040 and 14044) also require critical reviews done by external/internal experts or a panel of interest parties (e.g. customers, NGO, government dept, affected industries, maybe even competitors).

Is an LCA mandatory?

It depends on your situation.

If you are getting certified to ISO 14001, it is not mandatory. Here is a quote from clause 6.1.2:

“When determining environmental aspects, the organization considers a life cycle perspective. This does not require a detailed life cycle assessment; thinking carefully about the life cycle stages that can be controlled or influenced by the organization is sufficient.”

However, certain countries have passed regulations that make it mandatory in certain industries. It is becoming more and more common for construction materials and textile products, in particular. 

And this trend is going to accelerate due to the upcoming EU Ecodesign for Sustainable Products Regulation.

What are the main drawbacks of an LCA?

As we wrote above, an LCA addresses potential environmental impacts only.

It does NOT predict environmental impacts with any degree of precision nor does it look at, for example, economic or social impacts.

Sustainability regulations and approaches the LCA is related to.

A lifecycle assessment is also related to the following topics:

  • The EU Ecodesign for Sustainable Products Regulation – importers of products into the EU will need to manufacture more sustainable products and make their supply transparent in order to prove that the materials, components, and manufacturing processes are sustainable. A lifecycle assessment will be an important tool to assist in this goal.
  • Designing New Products With A Cradle To Cradle Cycle In Mind – you can’t design your product to be more ‘circular’ if you don’t know your supply chain’s environmental impact, therefore an LCA is useful here.


We at Sofeast are not lawyers. What we wrote above is based only on our understanding of the regulatory requirements. We do not present this information as a basis for you to make decisions, and we do not accept any liability if you do so. Please consult a lawyer before taking action.

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