Usability of national reporting data as a reference for generic unit processes

Abstract

Background, aim and scope

The reliability of the results of Life Cycle Assessment (LCA) studies is highly dependent on the appropriateness of the data that are used for Life Cycle Inventory (LCI) modelling. In practice, the modelling of background systems is commonly based on generic data—which are often outdated and rarely provide information on the current situation in a representative manner. Meanwhile, an increasing number of policy directives, international agreements and national legislations to regulate the reporting of environmentally relevant data for companies and economies entered into force over the past few years. The purpose of this study is, therefore, to compare data reported in such a manner from selected sources with detailed existing generic LCI data and to evaluate their usability as a reference for LCI modelling on a unit process level. Depending on the scope of the selected reports, the study reflects considerations on a national scale.

Materials and methods

Selected data from an existing LCI study are compared with data from environmental reporting approaches, in order to analyse the degree of variation between generic data and related reporting data. Two selected reporting obligations are described in more detail and characterised methodologically from the LCI perspective: (1) the ‘United Nations Framework Convention on Climate Change’ (UNFCCC) and (2) the European Union’s Directive on ‘Integrated Pollution Prevention and Control’ (IPPC). The national data that can be derived from these two reports are compared with generic LCI data provided by the ‘Environmental Profile Report for the European Aluminium Industry’ from European Aluminium Association (EAA).

Results

The number of processes and elementary flows is originally different across the three data sources due to divergent system boundaries. Therefore, in order to perform the comparison against a common reference, the analysis is done at a unit process level: only the emissions featured in all three sources are analysed (i.e. emissions of CO, CO₂, PFCs and SO₂ resulting from anode production, electrolysis and cast house). The comparison of data from this limited number of processes shows differences across the three data sources.

Discussion

A key reason for the differences is the divergent scopes considered in the different data sets (i.e. geographical coverage and time period). Still, despite the differences in scale and scope, the deviation between the data from IPPC and EAA is found to be within reasonable and acceptable margins—especially when also the different technological conditions are considered. Thus, the dataset of EAA is judged to be reliable—within its original scope. However—with the exception of PFCs—the differences between the data from the EAA report and those derived from UNFCCC cannot be explained this way.

Conclusions

This study exemplifies drawbacks and opportunities of the usability of data from environmental reporting as a national reference for existing LCI data. By comparing reporting data and existing LCI data, deviations can be explained and inappropriate or outdated data can be detected. For this procedure, knowledge about temporal coverage and individual system boundaries of the data is required. Also, expert knowledge about the processes themselves and technologies applied within these is indispensable, in order to explain differences between data sources.

Recommendations and perspectives

From an LCA perspective, the referencing of generic LCI data provides an important informative basis to focus data collection and update. However, inconsistencies due to the limited amount of elementary flows covered in reporting still need to be resolved—keeping in mind the individual aim of the study. Additional data from upcoming Pollutant Release and Transfer Registers provide a promising perspective.