This report is one in a series of Electrification Futures Study (EFS) publications. The EFS is a multi-year research project to explore potential widespread electrification in the future energy system of the United States. Electrification is defined as the substitution of electricity for direct combustion of non-electricity-based fuels (e.g., gasoline and natural gas) used to provide similar services.The EFS is specifically designed to examine electric technology advancement and adoption for end uses in all major economic sectors as well as electricity consumption growth and load profiles, future power system infrastructure development and operations, and the economic and environmental implications of electrification. Because of the expansive scope and the multi-year duration of the study, research findings and supporting data will be published as a series of reports, with each report released on its own timeframe. The table below shows the various research topics planned for examination under the EFS and how this report fits with the other components of the study. Topic Relation to this Report Electric technology cost and performance projections Provides technology data used in this report (Jadun et al. 2017) Electrification demand-side adoption scenarios This report Electric system supply-side scenarios Relies on electricity consumption reported in this report Electricity consumption patterns Relies on technology adoption projections reported in this report Electric system operations Relies on the consumption patterns and supplyside scenarios from other reports, which rely on data from this report Impacts assessment Relies on the technology adoption projections in this report along with data from other reportsThis report is the second publication in this series and presents scenarios of electric end-use technology adoption and resulting electricity consumption in the United States. The scenarios reflect a wide range of electricity demand growth through 2050 that result from various electric technology adoption and efficiency projections in the transportation, residential and commercial buildings, and industrial sectors. The report describes the methodology, assumptions, and limitations of the analysis. The demand scenarios provided in this report will be used to inform the supply scenarios and impacts to be presented in future reports under the EFS project. Results from the current demand-side scenarios can also be used by other researchers who wish to explore implications of electrification and demand growth in the U.S. economy.More information, the supporting data associated with this report, links to other reports in the EFS study, and information about the broader study are available at www.nrel.gov/efs. vi

In this article we consider interactions between life cycle emissions and materials flows associated with lightweighting (LW) automobiles. Both aluminum and high-strength steel (HSS) lightweighting are considered, with LW ranging from 6% to 23% on the basis of literature references and input from industry experts. We compare the increase in greenhouse gas (GHG) emissions associated with producing lightweight vehicles with the saved emissions during vehicle use. This yields a calculation of how many years of vehicle use are required to offset the added GHG emissions from the production stage. Payback periods for HSS are shorter than for aluminum. Nevertheless, achieving significant LW with HSS comparable to aluminum-intensive vehicles requires not only material substitution but also the achievement of secondary LW by downsizing of other vehicle components in addition to the vehicle structure. GHG savings for aluminum LW varies strongly with location where the aluminum is produced and whether secondary aluminum can be utilized instead of primary. HSS is less sensitive to these parameters. In principle, payback times for vehicles lightweighted with aluminum can be shortened by closed-loop recycling of wrought aluminum (i.e., use of secondary wrought aluminum). Over a 15-year time horizon, however, it is unlikely that this could significantly reduce emissions from the automotive industry, given the challenges involved with enabling a closed-loop aluminum infrastructure without downcycling automotive body structures.

We would like to thank all contributors for useful analysis, data, and input throughout the project. A technical review committee of senior-level experts provided invaluable input to the overall This report is available at no cost from the National Renewable Energy Laboratory at www.nrel.gov/publications.

NREL prints on paper that contains recycled content.

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Primary aluminum ingot is a globally traded commodity, and large regional differences in technology and electricity fuel mixes exist among the industry's smelters. A life cycle assessment model is developed to calculate absolute emissions and emissions intensities of greenhouse gases (GHGs) from the production, trade, and consumption of primary ingot in six world regions. Global production emissions are estimated at 283 (+/-18) Mt CO2-eq (14.7 (+/-0.95) kg CO2-eq/kg primary ingot) in 1990 and 468 (+/-26) Mt CO2-eq (14.7 (+/-0.80) kg CO2-eq/kg primary ingot) in 2005. In total, the production of primary aluminum accounts for 0.78 and 0.93% of world GHG emissions in 1990 and 2004, respectively. Regional production GHG intensities in 2005 range from 7.07 (+/-0.69) kg CO2-eq/kg primary ingot in Latin America to 21.9 (+/-3.0) kg CO2-eq/kg primary ingot in Asia. The GHG implications of expanding global trade of primary ingot are examined in terms of the emissions embodied in the imports and exports and the consumption-weighted emissions intensities of each region.

Life cycle assessment practitioners struggle to accurately allocate environmental burdens of metals recycling, including the temporal dimension of environmental impacts. We analyze four approaches for calculating aluminum greenhouse gas emissions: the recycled content (RC) or cut-off approach, which assumes that demand for recycled content displaces primary production; end-of-life recycling (EOLR), which assumes that postuse recycling displaces primary production; market-based (MB) approaches, which estimate changes in supply and demand using price elasticities; and value-corrected substitution (VCS), which allocates impact based on price differences between primary and recycled material. Our analysis suggests that applications of the VCS approach do not adequately account for the changing scrap to virgin material price ratio over time, whereas MB approaches do not address stock accumulation and depletion. The EOLR and RC approaches were analyzed using two case studies: U.S. aluminum beverage cans and vehicle engine blocks. These approaches produced similar results for beverage cans, which have a closed material loop system and a short product life. With longer product lifetimes, as noted with the engine blocks, the magnitude and timing of the emissions differs greatly between the RC and EOLR approaches. The EOLR approach indicates increased impacts at the time of production, offset by negative impacts in future years, whereas the RC approach assumes benefits to increased recycled content at the time of production. For vehicle engine blocks, emissions using EOLR are 140% higher than with RC. Results are highly sensitive to recycled content and future recycling rates, and the choice of allocation methods can have significant implications for life cycle studies. Keywords:automobile beverage cans consequential LCA industrial ecology life cycle assessment (LCA) metals Supporting information is available on the JIE Web site

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