Making LCA results count
To make LCA results count, it’s important to consider your audience. Not only when choosing the topic of your study or writing your conclusions, but also when you select your impact assessment method.
An important challenge in life cycle assessment (LCA) is transforming the raw data into useful information. People don’t just do an LCA because they want to generate tables upon tables of random facts – people do an LCA because they want to help their businesses understand their impact on the environment, make better decisions regarding sustainability and track their improvements over time. Therefore, it’s worth the effort to determine ahead of time who your audience is and what they’re hoping to learn. That way, you can select the LCA method that is most suitable for them.
What results does your audience need to see?
It’s important to present your information in a way that your intended viewer can understand. Say you want to illustrate to a high-level manager that a new design has environmental benefits. Showing specific differences in eutrophication and particulate matter formation impacts would perhaps be of interest to an LCA practitioner, but only add confusion in a situation like this. Instead, you need to be able to show benefits and drawbacks in a way that is intuitively understandable, especially to non-LCA experts, so that the focus is on how to move forward.
Determining who your audience is and how they need to be approached isn’t something you can leave until the last possible minute. You only get the results you need if you pick an impact assessment method that presents the results with the right level of detail, and you’re going to have to make this choice before you calculate your results and start your interpretation. There are many different ways to calculate and visualize LCA data that you can consider, but for now, we’ll focus on the distinction between midpoint and endpoint results.
Midpoint and endpoint methods give different levels of detail
When calculating the results of an LCA, you can use many different impact assessment methods. Although these methods vary in several aspects, one main distinction is between midpoint and endpoint methods. These methods use different stages in the cause-effect chain to calculate the impact.
As an example, let’s consider the cause-effect chain for a toxic chemical. Emission of the chemical into the groundwater may allow it to flow into a lake, where the chemical concentration might increase to a dangerous level. Fish could start dying, decreasing the overall fish population. In the end, the fish species might go extinct, possibly even having a negative effect on other species as well that rely on it for food.
An endpoint method looks at environmental impact at the end of this cause-effect chain. In this example, it determines the effect on the extinction of species. Endpoint results are typically shown as an impact on human health, ecosystem quality, and resource depletion (figure below). These three endpoints capture the effect of many different endpoints, since many different environmental impact pathways eventually end up as damage to human health, damage to ecosystems, or as depletion of resources.
A midpoint method looks at the impact earlier along the cause-effect chain before the endpoint is reached. In our example, a midpoint method might look at the increased concentration of the chemical in the lake water. It is at this point that it determines potential environmental impact.
Which type of method to use?
If we go back to the case of illustrating the environmental benefits of a new design to your high-level manager, it is probably a good idea to present your results at the endpoint level. Interpretation of these results doesn’t require extensive knowledge of environmental effects, and there are only three impact categories to consider. As a result, your manager will be able to take the information in quickly and apply it to the context of making decisions.
A drawback of endpoint methods is that the statistical uncertainties are higher. Data gaps and assumptions stack up along the cause-effect chain, so the further along it you express your environmental impact, the lower the reliability of the results. If you use a method like this, make sure you check that the differences are significant enough to account for this.
In other situations, it might be better to present your results at the midpoint level. Midpoint results can look a bit more daunting and require a bit more time to comprehend, but they provided a lot more detailed insight in return (figure below). For example, midpoints allow you to identify trade-offs. Consider a situation where one product has a high impact on climate change, while another product has a high impact on ozone layer depletion. Both of these impact categories contribute to the endpoints of human health and ecosystem quality, so in the endpoint results they could cancel each other out. But at the midpoint level, this difference is clearly visible and you can take that trade-off into account. On top of that, midpoint results have a lower statistical uncertainty, so the calculated results are more reliable.
Of course, the drawback of midpoint methods is that you need at least some knowledge of the multitude of environmental effects to properly interpret the results, and drawing overall conclusions can be more difficult.
Make an informed, conscious decision
In the great scheme of all things LCA, your target audience is just one thing to consider when selecting the impact assessment method for your LCA. But it’s an important factor that at least deserves some consideration and should not be overlooked. And whatever method you end up using, make sure you choose it consciously and consider all the options. Don’t just pick one because it’s familiar or it’s the method you always choose. In the end, this will help you to create more value with your LCA and make sure the results are actually put to use.
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My background in industrial design made it clear to me that the current system of consumption and disposal cannot be maintained in the long run. I quickly became interested in quantifying sustainability, so that well-supported decisions can be made in our move towards a more sustainable world. LCA provides the ability to focus on the facts.