Sep 05, 22

What is a life-cycle assessment (LCA)?


According to the European Environmental Agency, Life-cycle assessment (LCA) is the process of evaluating the effects that a product has on the environment over the entire period of its life. In this way, it determined a product’s impact on the environment. We are, for example, used to considering solar panels as a green alternative to fossil fuels. However, a LCA reveals that while the use phase of these products is indeed carbon neutral, the production phase weighs pretty heavily in terms of CO2 emissions1

To get a better impression of what LCA is, we will go through a recent study that estimated the environmental impact of different kinds of shopping bags. As LCA requires a life cycle perspective, the authors of the article considered different stages, namely grocery bag production, transoceanic shipping, local distribution transport, waste collection, incineration of the waste, energy recovery from incineration process, ash transport to transfer stations and offshore landfill. 

Once the life cycle of the product has been defined, we are left with the three key steps of LCA analysis: inventory analysis, impact assessment and definition of the functional unit.


Step 1: Inventory analysis

Inventory analysis is the first step of the LCA process – identification of all inputs which are necessary for the product, and the corresponding environmental consequences. In the case of a plastic shopping bag, the list of inputs includes ethylene and propylene polymers, energy consumed in the production process and fossil fuels necessary for the transportation to the final consumer and then to the landfill. The list of environmental consequences linked to these inputs includes CO2 emissions, the release of toxic substances, and air and water pollution.

Step 2: Impact assessment

In this phase inputs and environmental consequences are quantified and translated into impact categories. Said differently, we need to answer the question: how much?
How much CO2 is produced during the life cycle of a shopping bag? How many toxic substances are released?

This is where it gets tricky. Picture this: to estimate even just the emissions coming from the transportation of plastic bags we need to know where the shipping takes place, how often, how many plastic bags fit into one container, how much they weigh etc. Such accurate analysis needs to take place across the whole life cycle of a plastic bag, not only for its transportation phase. 


Step 3: The identification of the functional unit

On top of everything, the quantification must also be consistent so collected data must always refer to a standard unit. In the article we cited above2, all impact measurements refer to the standard amount of 820 million bags: the annual uptake of plastic bags from supermarkets in Singapore. 

Research is a tedious thing and when looking for data linked to the environmental impact of a product, especially when we are interested in its whole life cycle, it is very rare to find reports referring to the same functional unit. Maybe CO2 emissions were estimated for the production process of 100 plastic bags but then transport emissions data are expressed only in terms of the number of containers shipped and do not say anything about the number of bags per container which is an evident impediment to the consistency of the research. Luckily patience and competence allow experts to get around these obstacles most of the time. 


What is the result of the LCA?

So, let’s say that we collected all information, all inputs, and environmental effects, quantified them and were able to adopt the same functional unit. What is the result of the LCA? 

Well, at this point it will be easy to compare the negative environmental effects of products and for each of their lifecycle phases. In the case of solar panels, we could realize that even though they are considered green, they still hide a high carbon cost in their production or displacement phase. Another useful application of LCA is the comparison of similar product categories. In the article2 different shopping bags were compared and the performed LCA revealed that reusable bags have a lower impact on the environment than single use ones.

Finally, if you are not sure about the environmental impact of any of your everyday items, be sure someone out there has performed an LCA on it. And if you are manufacturing a whole new item, take into consideration performing a LCA on it. It is an excellent instrument to openly communicate about environmental performances.



Peng, J., Lu, L., & Yang, H. (2013). Review on life cycle assessment of energy payback and greenhouse gas emission of solar photovoltaic systems. Renewable and sustainable energy reviews, 19, 255-274.

2 Ahamed, A., Vallam, P., Iyer, N. S., Veksha, A., Bobacka, J., & Lisak, G. (2021). Life cycle assessment of plastic grocery bags and their alternatives in cities with confined waste management structure: A Singapore case study. Journal of Cleaner Production, 278, 123956.