Paradigm shifts for environmental assessment of decarbonizing energy systems: Emerging dominance of embodied impacts and design-oriented decision support needs

As energy systems decarbonize, their environmental impacts will change. Historically, energy consumption has been a reliable proxy for environmental impacts of interest due to the dominance of fossil fuel combustion. With a normative transition to decarbonized energy, however, environmental assessment of energy systems faces two major paradigm shifts: 1) environmental profiles are likely to be dominated by embodied rather than operational impacts; and 2) the primary analytical need is for prospective and trustworthy analysis to support system design decisions. Ensuring that analysis of diverse potential decarbonized futures is rigorous and granted legitimacy by potential users is critical if such analysis is to be used and useful as decision support. This review uses both computational and narrative methods to evaluate the English language literature on 12 environmental impact categories and 18 types of decarbonized energy resources or energy carriers to ask: what issues does environmental assessment need to be able to rigorously evaluate to support decisions about designing a decarbonized energy supply? We find that embodied impacts are likely to dominate. We suggest that land use metrics might displace energy consumption as the best single proxy for overall energy supply system impacts, though translating land use inventory data to environmental impacts requires significantly more contextualization than does fossil fuel combustion. Individual energy resources or energy carriers have diverse potential environmental impacts that are highly context dependent and dynamic under technological and environmental change, which suggests that mitigation pathways might depend on project design choices more than technological mitigation.