Replacing location-based electricity consumption with market-based residual mixes in background data to avoid possible double counting: a quantitative analysis of effects and challenges

Abstract

PurposeMost life cycle inventory (LCI) datasets include location-based electricity mixes. Using these LCI datasets in combination with market-based electricity accounting in life cycle assessments (LCAs) leads to double counting of electricity from specific sources, such as renewable energy. The goal of this paper is to analyze market-based accounting by replacing location-based electricity consumption with market-based residual mixes in all processes of the ecoinvent database. The python script for this replacement procedure is openly available.Materials and methodsWe use the Brightway 2 software package to replace European location-based electricity consumption in all 21,238 processes of the ecoinvent database with residual electricity mixes on the corresponding voltage level. The ecoinvent database provides residual electricity mixes for all countries involved in European trade with market-based energy attribute certificates—Guarantees of Origin. We analyze the induced changes to the database both on an individual process level and on a database-wide level. The analysis focusses on the impact category climate change but is further extended to the impact categories terrestrial acidification, freshwater eutrophication, marine eutrophication, ozone depletion, and particulate matter formation.Results and discussionFor European processes, the implementation of the residual electricity mixes leads to average changes in the life cycle impact assessment (LCIA) results for climate change of 1%, 10%, 20%, and 50% for 2958, 733, 387, and 107 processes, respectively. Changes are especially pronounced for Norwegian and Icelandic processes due to the large differences among their location-based and residual electricity mixes. For the other analyzed impact categories, the changes in LCIA results are particularly high for freshwater eutrophication. With the push towards more primary data in LCA and GHG accounting, the impacts of using residual electricity mixes instead of location-based electricity mixes need further research on basis of quantified figures, which we present in this paper.ConclusionThis paper presents an approach towards enabling more consistent market-based accounting throughout LCAs and thereby contributes to the avoidance of double counting. Since only European residual mixes are considered, the database of this paper leads to distortion of LCA results. Further, research is needed to address double counting beyond the European electricity sector. This includes an expansion of this research to a global level and other industrial sectors. Furthermore, research is needed regarding industry-specific electricity sources in LCI datasets, which may also lead to double counting.