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

Eleonora Crenna,Michela Secchi,Lorenzo Benini,Serenella Sala

doi:10.1007/s11367-019-01604-y

Abstract

PurposeCharacterizing 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).Material and methodsThe 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.Results and discussionThe 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.Conclusion and outlookThe 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.

Highlights

The growth of human population and the increase in consumption intensity at the global level have led to an Responsible editor: Jeroen Guinée Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Life cycle assessment (LCA) is a reference methodology for the evaluation of environmental impacts along the supply chain
The environmental pressures associated to emissions into air, soil, and water and to resource extraction are traditionally estimated by adopting a territorial perspective, namely collecting statistical information associated with emissions and resource use occurring within a defined spatial scale
Following the collection of data for compiling the global inventories and their mapping into elementary flows according to the International Reference Life Cycle Data System (ILCD) nomenclature, the inventories were characterized by using ILCD characterization factors (CFs) at the midpoint (EC-JRC 2012)

Summary

Introduction

Life cycle assessment (LCA) is a reference methodology for the evaluation of environmental impacts along the supply chain. Life cycle–based methodology is increasingly adopted to assess production and consumption patterns and to identify hotspots of impact which may represent the key areas of. In the LCA context and according to ISO 14044 (ISO 2006), normalization is an optional step that allows the interpretation of the characterized results in terms of relative environmental relevance of the impacts. Normalization provides a reference situation for the environmental pressures of all the impact categories, meaning that—through normalization— absolute impact scores are converted into relative contributions of the analyzed product or system to a reference situation (Sleeswijk et al 2008). Normalization factors (NFs) are often composed of regional and global inventories of emissions and resource use, coupled with estimations of missing elementary flows (e.g., proxy for chemical emissions leading to impacts on toxicity, Cucurachi et al 2014), and characterized by using an impact assessment method and the related models

Methods

Results

Conclusion