Life cycle assessment, or LCA, has a reputation for being complicated. The detail certainly can be. The structure, however, is simple, and understanding it makes it much easier to commission, read or challenge an LCA.
LCA is described in the international standards ISO 14040 and ISO 14044, which set out four connected phases.
1. Goal and scope
This is the most important step, and the one most often rushed. Here you decide:
- what question the study is trying to answer
- who it is for
- what exactly is being assessed, and where its boundaries lie
- the functional unit, which is the thing you measure everything per
The functional unit is what makes comparisons fair. Comparing a kilogram of one material with a kilogram of another can be misleading if one lasts three times as long. Comparing “one pair of shoes worn for a defined period” is more meaningful.
2. Inventory analysis
Here you collect the data: the materials, energy, water and transport that go into each stage, and the emissions and wastes that come out. In leather this might run from farming and slaughter through tanning and manufacturing to use and disposal. A mass balance, following how much of every input ends up in the product and how much ends up as waste, is the foundation. Good data is the hard part, and it is the reason many LCAs begin with a data-collection exercise.
3. Impact assessment
The inventory is a long list of flows. Impact assessment translates them into environmental effects, such as climate change, water use, acidification or eutrophication, so that the results can be understood and compared.
4. Interpretation
Finally, you check the results against the goal. Which stages matter most? How sensitive are the conclusions to assumptions? What are the limits of the data? A trustworthy LCA is open about its uncertainty rather than hiding it.
Different types of study
An attributional LCA describes the impacts of a product as it is. A consequential LCA asks what would change if you made a decision, such as switching material. Comparative studies set options side by side. Which you need depends on the question.
Starting small
You do not need a perfect model to begin. Many companies start by collecting data on their main processes and building up. What matters is that you decide the question first.
If you are starting out, or reviewing an existing study, we are happy to help.
By Authenticae. Back to the blog