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What is Lifecycle Assessment—and Why Does it Matter?

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Hi, I’m Rachael and I recently joined the UCS team as a Kendall Science Fellow in the Clean Vehicles group. My focus during the fellowship will be on the lifecycle impacts of advanced vehicle technologies, so first I’m going to start with a brief background on what lifecycle assessment is and why it’s important.

What is lifecycle assessment?

Lifecycle assessment, or LCA, is an analysis to understand the total cradle-to-grave impacts of a good or service. The impacts most commonly measured are costs, energy, and emissions. The lifecycle assessment of costs has been measured for hundreds of years. Accounting for all the costs of a good or service is necessary to determine if a product or service will be profitable and competitive. However, accounting for all the costs can be complex depending on your final product or service.

Robots in the Tesla manufacturing line. Understanding the lifecycle impacts of vehicle production allows us to better evaluate the true cost of driving. Source: Patrick Herbert

Robots in the Tesla manufacturing line. Understanding the lifecycle impacts of vehicle production allows us to better evaluate the true cost of driving. Source: Patrick Herbert

More recently, energy and emissions have become a larger part of the lifecycle dialogue spurred by growing concern of climate change. If you think costs are difficult to estimate, think about how much more difficult energy and emissions are to assess across making a vehicle. With energy, like electricity or natural gas use, it’s always flowing and with emissions, it’s rare to have specific measurements.

When I’ve taught this as part of an outreach program at Carnegie Mellon University, called the Green Design Apprenticeship, we’ve used a toaster as an example. In our toaster example, it may be reasonable to estimate the energy required to create the entire toaster—but measuring the energy of all the pieces (the plastic sides, the heating device, the electronics, the cord, the plug, etc.) may be more difficult. The same occurs with emissions, but emissions aren’t measured as well as energy (emissions don’t have running meters like electricity does). Therefore, analysts rely on modeling to estimate the lifecycle energy and emissions of goods and services. Common components of an LCA of a product are extraction of raw materials, manufacturing and assembly, transportation, use of the good or service, recycling or reuse, and waste or disposal.

Why is it important?

LCA is important because you may have a good or service that reduces costs, energy, or emissions in one area of its use, but overall the impacts are larger. For example, someone develops an amazing process to reduce the manufacturing costs, energy, and emissions of a toaster, but then during the use of the toaster it uses more electricity than it used to. Depending on how much more electricity is used it could offset the costs, energy, or emissions savings in the manufacturing of the toaster, undermining the objective to reduce the overall costs, energy, and emissions of making a piece of toast.

Put another way, lifecycle assessment lets us better understand the true impacts of any given good or service. It’s important information for scientists, consumers, and policymakers alike.

What should you know?

1. All LCA’s should have a functional unit.

The functional unit is how the LCA is measured and varies across goods and services. For example, a toaster supplier may be interested in the impacts of the toaster as a unit, whereas a consumer would be interested in the impacts of the toaster per slice of toast it produces. The LCA results of a whole toaster versus a slice of toast would be very different, proving the importance of defining the functional unit properly.

There are international standards on how to do an LCA, and having a functional unit is one of the first requirements.

2. Not all LCA’s are comparable despite having the same functional unit.

Just because two different LCAs have the same functional unit does not mean they are comparable. This is because of the underlying assumptions the analyst has to make.

To use the toaster example, these assumptions may include how long the toaster lasts, what materials were used, and where the electricity comes from to manufacture and use it. All those assumptions change the results of an LCA and make comparing separate results difficult.

3. There is no “right” answer, but there are good recommendations.

As unsatisfactory as it may sound, the answer of every LCA should be “it depends.” Why is this? Because the analyst must make assumptions to get to a final result. Those assumptions need to be justified and well-documented. The analyst may be able to suggest and recommend what they believe the most reasonable result to be, but there will always be others who disagree with the assumptions and therefore don’t agree with the result. Equally important is an analysis of how the LCA results change when the assumptions change. This is called a sensitivity analysis and can help you understand whether an assumption has a large impact on the final result or not. Overall, the final results are very much based on the analyst’s data availability and judgment.

I hope I have explained the basics of  LCA and have convinced you how important this type of analysis can be when making decisions. Stay tuned for more on how LCA relates to advanced vehicle technologies!

Posted in: Vehicles Tags: ,

About the author: Rachael Nealer is an engineer and Kendall Science Fellow exploring the lifecycle environmental impacts of advanced vehicles, specifically hybrid-electric, plug-in electric, and fuel cell vehicles. See Rachael's full bio.

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