Abstract
Deep decarbonization of national energy systems requires high percentages of renewable electricity supply and significant electrification of transport and heat. As the proportion of renewable electricity supply increases, operational emissions will gradually decrease, making embodied emissions a more important component of the total emissions of these future electricity systems. Embodied emissions from electricity systems remain largely overlooked in existing energy and climate policy frameworks that prioritise operational emissions. Life cycle assessment (LCA) provides a systematic approach to evaluating both the operational and embodied emissions from these electricity systems. However, systematic LCA studies of future highly renewable electricity systems are scarce, and previous studies have omitted emissions associated with distribution and transmission infrastructure. To address these gaps, this study applies scenario-based LCA modelling to six future decarbonization scenarios for the New Zealand national electricity system, including a scenario that achieves 100 % renewable supply by 2045. Comparative analysis of two periods (2020–2035 vs. 2036–2050) shows operational and maintenance emissions drop from 85 % to 60 % of total life cycle emissions, while the share of embodied emissions more than doubles. Mitigation priorities should therefore shift from reducing fossil fuel use to improving and decarbonizing renewable energy technologies as their share grows. Including embodied emissions results in all five scenarios exceeding the electricity sector's allocated carbon budget by around 2037. The framework and findings in this study are applicable to other countries pursuing deep decarbonization of their energy system.