Regional electricity consumption mixes using trade data for representative inventories

Electricity flows are frequently used life cycle assessment modeling and are often a significant source of emissions so creating inventories based on detailed inventories, representative of regional differences in grid supplied power, is important. We sought to understand the influence electricity trades have on consumption mixes and developed a method for creating regionalized US electricity inventories based on publicly available data for electricity generation and trades. With generation inventories for the eGRID subregions and trading within NERC regions, the trading operates within boundaries representative of distinct production regions while enabling trading. We created two approaches for allocating electricity trades within NERC regions, gross, and net trading. Trading is modeled using FERC data. Gross trading assumes that all trades within a NERC region contribute to each eGRID subregion receiving trades in to satisfy their demand while the net trading approach assumes that only eGRID subregions producing surplus electricity contribute to the mix in regions with deficits. We introduce the concept of trade pools for modeling electricity flows between individual eGRID subregions and the corresponding NERC regions. Challenges for modeling electricity trade flows are described in the Methodology section. We compare the results of the two trading approaches demonstrating the influence of prioritizing eGRID subregion generation mixes or trading within NERC regions. While trades represent a relatively small portion of total consumed electricity, some eGRID regions, like CAMX and those in New York state, rely heavily on trade to in order to meet their consumptive demand. The method presented here establishes the basis for eGRID-level consumption mixes which account for energy trades and provide regionalized life cycle inventories for electricity in the USA. We provide recommendations for their use including in attributional LCA as well as approaches requiring marginal electricity demands. The trading approaches have been implemented in a US EPA repository to provide these inventories and can be found at https://github.com/USEPA/ElectricityLCI .