Life Cycle Assessments Part 1

by Kevin Boehnke

Featured picture from Sustainable graphic design

With sustainability being a big buzzword these days, consumers are trying to lower their carbon footprint and find the most environmentally conscious products. However, while many companies are doing a great job providing such products, there have been instances of companies using bogus claims to cash in on the higher prices commanded by ‘green’ goods, otherwise known as greenwashing. Because of this, it’s important to have a way to quantify whether different products are actually as environmentally friendly as they claim or if they are merely greenwashed


Just a little green paint and voila! You’re sustainable! From Grist. org

I recently finished my third semester in graduate school, and I thought about whether I had learned anything in my classes to see if there were any lessons that could be applied to this problem. Surprisingly, I realized that I had taken a class that could provide broad insights for this very problem: An Overview of Life Cycle Assessments. 

 Life cycle assessments are a way of measuring and comparing the environmental and human health impacts of different consumer goods. Life cycle assessments evaluate products that provide the same service, that is, the same functional unit. This was initially little bit tricky for me to understand, so I will illustrate it with an example. You are trying to make your house more energy efficient, and decide to replace all of your incandescent light bulbs. However, you don’t know what kinds of bulbs you want to replace them with: LED or fluorescent. LEDs cost more, but they also have a longer lifetime. How do you determine which is better?

You can’t simply compare one fluorescent bulb and one LED bulb since they don’t provide the same number of hours of light. How do you reconcile this? By using the service of the bulb: providing light of a certain quality for a certain amount of time (e.g. 400 lumens for 10,000 hours). Let’s pretend that the LED bulb provides 10,000 hours of light and the fluorescent bulb provides 5,000 hours of light. Thus, you need one LED bulb and two fluorescent bulbs to provide your functional unit of 10,000 hours of light.


Following the establishment of your functional unit, you then determine all of the costs and materials associated with that functional unit. At this stage, it is important to define system boundaries, that is, how far you plan to follow each material in the LCA. Let’s think about the production of another set of products: paper and plastic grocery bags. For example, if we consider the wood used to make the paper bag, should we consider the equipment that was used to process the paper? And the machines used to build the paper processing equipment? And the raw materials to make those machines?  This process can go on ad infinitum, and system boundaries must be carefully defined to avoid wasting processing power and time to quantify minuscule impacts. LCA practitioners typically use a 1-5% cut-off, i.e. any process that contributes less than 1-5% of total emissions is not included.

It keeps going and going and going… From Desktop Nexus

Continuing with our back example, we would need to characterize the resources used for all life stages of the paper and plastic bag, including: raw materials, manufacturing, packaging, transportation, energy used during the lifetime, and disposal. This involves a lot of smart thinking about inputs and outputs – we do not want to leave out anything important – but the math is simple arithmetic. While compiling these data, we could also determine the monetary cost of each of these processes in order to consider both the environmental and economic impacts of the functional unit. This can be key for interventions that aim to streamline production or services.

Impact assessment

Once the above steps are complete, we would plug our results into an LCA software program (of which there are many). This software then characterizes the energy consumed, emissions (e.g. heavy metals, particulate matter, or carbon dioxide) produced by the respective products, and the relative impacts of those emissions on human and environmental health. Finally, the results are used to identify the relative impacts of each process and determine processes that pollute the most heavily or have the largest impacts on human health. This last step is necessary to tease out the processes that are most important to change to lessen monetary costs, environmental damage, etc…

File:Superfund EPa sign.jpg

Ideally, we’ll avoid creating more of these. Source: Wikimedia Commons

So, who would actually want to do this or to have this done?

  1. Companies that manufacture products or provide services: The beauty of having a well-done LCA is that it helps target the processes that consume the most energy, are the least efficient, or produce the most pollution in order to carry out interventions to improve these steps. This can help companies by providing them with higher profits due to lower production costs. Further, by reducing pollution, companies can spend less on pollution treatment and also market themselves as an environmentally friendly company without the risk of being called out as a greenwasher.
  2. Consumers: As mentioned above, when it comes to buying products of all kinds, consumers are jumping on the ‘green’ and ‘sustainable’ train. Having LCA information available would allow consumers to make informed decisions and support companies with lower environmental impacts, saving our society money on healthcare and pollution cleanup efforts.
  3. Governments: Using LCAs, regulators could have any easier time managing pollution and also quantifying the outputs from each company. This would provide more transparency and ideally allow for more targeted laws that focus on the most harmful of emissions.

Some notes of caution

Clearly, there are some issues with this sort of modeling. LCAs are necessarily limited because we cannot include all of the impacts in order to maintain a reasonable timeline. Furthermore, companies typically provide most of their own data to be used in the LCA, as it is usually proprietary information. This data may be incomplete for multiple reasons, including not accurately defining all of the impacts, not thinking carefully about all the layers of the system, miscalculation, deliberate obfuscation, etc… It’s also necessary to think about all of the reasonable product options – in our bag example, adding re-usable bags into the mix would certainly have made it a more realistic comparison, since many people use these on a regular basis. No model actually replicates reality, so findings must be carefully checked to ensure that they actually make sense. This can be done by verifying them in multiple LCA databases, performing uncertainty analyses to test the validity of the model, and having a secondary party audit the entire LCA after it is complete. LCAs typically incorporate some or all of these steps.

Despite the limitations of LCAs, a careful LCA can provide a compelling picture of the costs associated with all stages of life in a product, and overturn a few of our assumptions about sustainability. For instance, using a paper bag is surely better than using plastic grocery bag, since paper is recyclable,and plastic persists in the environment, right? Probably not: plastic bags have been consistently  shown to have a lower environmental impact than paper bags.

LCAs also form the basis for new models to understand how our consumption affects the environment and people globally, tracking where the emissions from consumption actually end up (hint: a large portion of it ends up in developing nations with more lax labor and pollution laws).


So that’s where all of our electronics end up… Source: Science Blogs

In short, LCAs are one of the best modeling tools available to help us truly see the impacts we have as consumers. They provide us with valuable insight about how to choose the most environmentally responsible products and how to make decisions to lessen the damage that we inflict on our global habitat.

This post is the first of a two part series. This post will discuss the process of performing a Life Cycle Assessment (LCA) and why it is useful for consumers and institutions. The second part will critically assess some published literature, demonstrating some places where LCAs would be merited and/or may provide a more complete answer to the questions asked.


  • Lewis, Helen, Karli Verghese, and Leanne Fitzpatrick. “Evaluating the sustainability impacts of packaging: the plastic carry bag dilemma.” Packaging Technology and Science 23.3 (2010): 145-160. DOI
  • Special thanks to Dr. Olivier Jolliet and Dingsheng Li at the University of Michigan for teaching me about this neat tool