Life cycle assessment applying planetary and regional boundaries to the process level: a model case study

Abstract

The planetary boundaries framework contains regional boundaries in addition to global boundaries. Geographically resolved methods to assess regional environmental impacts are therefore needed. Existing planetary boundaries-based life cycle assessment (PB-LCA) methods have limited geographical resolution or are not applicable to full product systems, due to high spatial requirements on inventory data. Here, we enable PB-LCA of full product systems across a comprehensive set of regional and global PB impact categories. We propose comparing environmental impacts of individual processes within a product system to assigned shares of regional or global safe operating space (SOS). This is followed by aggregation of process-level results so that accumulated exceedance of assigned SOS is derived across the entire life cycle. We then present a procedure for aggregating geographically resolved characterization factors (CFs) and SOS to country, continent and global levels, ensuring compatibility with typical life cycle inventory results. We then apply the new techniques to a model laundry case study. It involves 61 selected processes, two geographically resolved PB-LCA methods, related to impacts from freshwater use and nitrogen emissions, and a largely spatially generic PB-LCA method that covers a comprehensive set of impact categories. The calculation of accumulated exceedance of assigned SOS may help inform decisions about where in a life cycle to focus impact reduction efforts most urgently. The number of case study processes that exceed their assigned SOS differs when applying the geographically resolved methods, as opposed to the largely spatially generic method. Case study results differ greatly across PB-LCA impact categories, reaffirming the importance of covering a comprehensive set. Geographically resolved methods are needed for all regional impact categories and software support would be advantageous. Existing methods will require periodic updates to reflect ongoing advancements in PB science. Best practice approaches or a consensus for assigning regional SOS to processes are needed. Our study provides a step towards greater operability of geographically resolved PB-LCA methods by enabling application to a full product system within an assessment that covers a comprehensive set of impact categories. The case study application shows potential advantages of the process-level approach and points to the need for quantifying uncertainties in such assessments. Future studies should seek to explore the potential role of PB-LCA in decision support compared with conventional LCA.