Global environmental impacts: data sources and methodological choices for calculating normalization factors for LCA

Characterizing environmental impacts at the global scale is crucial to define references against which compare the environmental profile of products and systems. Within this study, global emissions and resource uses have been collected and characterized for the following impact categories: climate change, ozone depletion, human toxicity (cancer and non-cancer), ecotoxicity, particulate matter, ionizing radiation, photochemical ozone formation, acidification, eutrophication (terrestrial, marine, and freshwater), land use, water use, and resource use. The results can be used as normalization factors (NFs) in the context of the life cycle assessment (LCA). The global NFs are built on an extensive collection of data on emissions and resources extracted at a global scale in 2010, gathering different sources and comparing them. A hierarchical approach was applied to the selection of data sources. Extrapolations, mainly temporal data-gap filling, were applied for complementing the inventories for missing data. In order to calculate NFs, the inventory was characterized by using the International Reference Life Cycle Data System (ILCD) midpoint indicators and the EU Environmental Footprint (EF) set, which includes recently released models. The resulting global NFs (ILCD and EF) were reported and discussed for each impact category. Coverage completeness and robustness of both the underpinning inventories and impact assessment models were used to define the level of uncertainty in the calculations. Based on the contribution analysis of the main elementary flows, it resulted that only few elementary flows drive the overall impact for most of the impact categories. Moreover, the ratio between the NFs at EU27 in 2010 and global level showed that Europe generally covers less than 10% of the global impact. The quantification of the current levels of environmental pressures entails critical aspects, as it consists of accounting of emissions and resources, relying on data often incomplete or based on modeling. Despite the attempts made for increasing NFs coverage and robustness, the calculation in the present study highlights the need of further efforts aiming at overcoming the uncertainties and the limitations identified both at the inventory (i.e., difficulty in retrieving complete and recent data) and characterization levels (e.g., consistency between inventory and impact assessment regarding spatialization, system boundaries). Most importantly, any assessment based on the use of NFs should be carefully discussed and interpreted in light of the limitations discussed in this paper.