Consider Your Audience When Doing Impact Assessment
One of the strong points of Life Cycle Assessment (LCA) is that it is based on scientific data, making it one of the more reliable methods to determine environmental impacts. It is unavoidable that an LCA process also results in a lot of new data.
An important challenge in LCA is transforming the raw data into useful information. People don’t just do LCAs because they want to generate tables upon tables of random facts – people do LCA because they want to help their businesses to make better decisions regarding sustainability. It’s worth the effort to determine ahead of time who your audience is and to 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 only be confusing. You need to be able to show benefits and drawbacks that are intuitively obvious, especially to non-experts.
Deciding 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 the 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, but for now we’ll focus on the distinction between midpoint and endpoint results.
Midpoint and Endpoint Methods Give Different Detail Levels
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, that look at different stages in the cause-effect chain to calculate the impact.
Let’s consider the cause-effect chain for a toxic chemical. Emission of the chemical into the groundwater will 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 (figure 1).
Figure 1 - Example of a cause-effect chain
An endpoint method looks at environmental impact at the end of this cause-effect chain. In this example, at the extinction of a species. 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.
Which Type Of Method Should You Use?
When 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. Endpoint results are usually shown as impact on human health, ecosystem quality and resource depletion (figure 2). Interpretation of these results doesn’t require extensive knowledge of environmental effects, and your manager will be able to easily make decisions. A drawback of endpoint methods is that the statistical uncertainties are higher. Data gaps and assumptions stack up along the cause-effect chain. If you use a method like this, make sure you check that the differences are significant.
Figure 2 – fictional example of endpoint results
In other cases, it might be better to present your results at the midpoint level. Midpoint results can be more difficult to interpret because they consider a large number of impacts, but they offer more detail in return (figure 3). 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. Midpoint results give you the chance to make a well-founded decision either way. Endpoint results would merely show a high impact on ecosystem quality and human health, without indicating the source. In addition, midpoint results have lower statistical uncertainty. The drawback of midpoint methods, as we’ve shown, is that you need at least some knowledge of the multitude of environmental effects to properly interpret the results.
Figure 3 - fictional example of midpoint results
Make An Informed, Conscious Decision
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 should not be overlooked. Whatever method you decide to use, make sure you choose it consciously and not just because it is the method you always choose. In the end this will help you to create more value with your LCA and make sure your report doesn’t end up on a shelf collecting dust.