On the relevance of scope 3 emissions and power trade for regional life cycle inventories of electricity consumption in the USA

Abstract

Most life cycle inventories (LCIs) of electricity consumed in different regions of the USA disregard the power that is being traded between these regions, while the US EPA’s eGRID database does not contain scope 3 or noncombustion emissions. The relevance of these omissions has not yet been comprehensively quantified in the literature. This paper aims to close this knowledge gap. The parameterized inventory models that underlie all publicly available grid mix datasets in the GaBi databases were configured to create 26 eGRID subregional LCIs based on data from EPA’s eGRID2014 database and the Federal Energy Regulatory Commission’s FERC-714 report on power trade for the same reference year. Results were calculated regarding climate change, acidification, eutrophication, particulate matter, smog formation, and blue water consumption per kilowatt hour of electricity and compared for direct plant emissions only, the cradle-to-gate production mix (including scope 3), and the cradle-to-gate consumption mix (including scope 3 and power imports). Results showed that the scope 3 burdens represent the most significant data gap if not accounted for. Specifically, the GWP results show median increases of around + 18% for GWP100 and of + 30% for GWP20 when scope 3 GHG emissions are added to the direct plant emissions. Other impact categories showed even larger increases when compared to direct plant emissions, with a maximum increase of + 573% in eutrophication potential for the subregion CAMX. While the median deviations of the consumption mixes compared to the production mixes are moderate, individual subregions show significant increases in environmental burdens for selected metrics. However, power trade seems less of an issue for the impact category of climate change as only the CAMX subregion shows an increase larger than 10% when power trade is accounted for. A cradle-to-gate production mix can be a suitable proxy of the environmental burdens of electricity consumed in many subregions, but it can also lead to significant errors for others depending on the environmental metric(s) one is trying to assess. Power plant emissions by themselves (scope 2) that exclude both scope 3 emissions and power trade cannot be recommended for use in any kind of carbon accounting or other environmental analysis because they suffer from severe data gaps and may skew the comparison of the environmental burdens associated with power consumption in the different subregions significantly.