How can you identify the most relevant impact categories for your LCA?

1 Goal and scope

The first step to identify the most relevant impact categories for your LCA is to define the goal and scope of your study. The goal and scope should specify the purpose, context, and boundaries of your LCA, as well as the intended audience and application of the results. The goal and scope should also include the functional unit, which is the reference unit for comparing the environmental performance of different alternatives. Based on the goal and scope, you can select the impact categories that best reflect the environmental aspects and issues that are relevant for your study.

2 Data availability and quality

The second step to identify the most relevant impact categories for your LCA is to assess the availability and quality of data for each impact category. Data availability and quality can vary depending on the sources, methods, and assumptions used to collect and process the data. Some impact categories may require more data than others, or more specific or regional data. For example, water scarcity and land use impacts may depend on the location and time of the water or land use, while climate change impacts may be more global and generic. You should select the impact categories that have sufficient and reliable data for your LCA, and avoid those that have significant data gaps or uncertainties.

3 Stakeholder expectations and communication needs

The third step to identify the most relevant impact categories for your LCA is to consider the stakeholder expectations and communication needs. Stakeholders are the individuals or groups that have an interest or influence on your LCA, such as customers, suppliers, regulators, investors, or NGOs. Stakeholders may have different expectations and preferences for the impact categories that they want to see in your LCA, depending on their values, objectives, and perspectives. For example, some stakeholders may be more concerned about local or regional impacts, while others may be more interested in global or long-term impacts. You should select the impact categories that meet the stakeholder expectations and communication needs, and explain the rationale and limitations of your choices.

4 Impact category selection methods

Identifying the most relevant impact categories for your LCA is the fourth step. Impact category selection methods are systematic approaches or criteria for choosing the impact categories. Examples include the ISO 14040/44 standards, which provide a list of mandatory and optional impact categories based on scientific consensus and international relevance; the ILCD handbook, which provides recommended impact categories and indicators based on scientific robustness and operational applicability; the ReCiPe method, which aggregates impacts into three areas of protection; and the stakeholder consultation method, which involves engaging stakeholders to solicit their feedback. You should use one or more impact category selection methods that are consistent with the goal and scope of your LCA, complementing data availability, quality, stakeholder expectations, and communication needs.

5 Impact category prioritization

The fifth step to identify the most relevant impact categories for your LCA is to prioritize the impact categories based on their relative importance and significance. This can help you focus on the impact categories that have the most influence on the environmental performance of your LCA, as well as reduce complexity and uncertainty of results. There are several methods for prioritization, such as the screening LCA method, which involves performing a simplified or preliminary LCA to estimate contributions, the sensitivity analysis method, which involves varying data, assumptions, or methods to assess sensitivity of each category, and the weighting method, which involves assigning numerical values or weights. When deciding which method to use, you should consider transparency, justification for your LCA, goal and scope of your LCA, stakeholder expectations, and communication needs.

6 Impact category review

The sixth and final step to identify the most relevant impact categories for your LCA is to review the impact categories and indicators for your LCA, and to verify that they are appropriate and valid. To do this, you can employ the critical review method, which involves submitting your LCA to an independent panel of experts or peers. Alternatively, you can use the benchmarking method, which involves comparing your LCA with other similar or relevant LCAs. Additionally, the feedback method allows you to present your LCA to stakeholders and obtain their feedback and comments. Whichever method you choose, it should be rigorous and constructive for your LCA, so that you can improve and refine the impact categories and indicators for your LCA.