How do you incorporate spatial and temporal aspects of impacts in LCA impact assessment?

2 Temporal variability

Another challenge of impact assessment in LCA is to account for the temporal variability of environmental impacts. Different time scales may have different implications for the assessment of impacts, especially for long-term and delayed effects. For example, the impact of greenhouse gas (GHG) emissions depends on the time horizon chosen for the global warming potential (GWP) indicator, which can range from 20 to 500 years. Similarly, the impact of radioactive waste depends on the decay rate and the exposure time of the receptors. To address this challenge, some impact assessment methods use temporal differentiation or discounting, which reflect the time preferences and uncertainties of the impacts. However, this also involves ethical and subjective choices, and may affect the comparability and consistency of the results.

3 Uncertainty and variability

A third challenge of impact assessment in LCA is to deal with the uncertainty and variability of the data and the methods. Uncertainty refers to the lack of knowledge or precision about the inputs or outputs of the LCA, while variability refers to the natural or human-induced diversity or heterogeneity of the system. Both uncertainty and variability can affect the accuracy and reliability of the impact assessment results, and may lead to different conclusions or recommendations. To address this challenge, some impact assessment methods use sensitivity analysis, scenario analysis, or probabilistic approaches, which explore the range and distribution of the possible outcomes and their implications. However, this also requires more data and computational resources, and may complicate the interpretation and communication of the results.

4 Value choices and trade-offs

A fourth challenge of impact assessment in LCA is to deal with the value choices and trade-offs involved in the selection and aggregation of impact categories and indicators. Different impact assessment methods may use different criteria and methods to define, measure, and weight the environmental impacts, which reflect different perspectives and preferences of the stakeholders. For example, some methods may focus on human health and ecosystem quality, while others may include social and economic aspects. Some methods may use a single score or index to aggregate the impacts, while others may use a multi-criteria approach. To address this challenge, some impact assessment methods use transparent and participatory processes, which involve the stakeholders in the definition and evaluation of the impacts. However, this also requires more time and effort, and may not resolve all the conflicts and controversies.