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Large-scale production and use of all-electric vehicles have environmental implications in two key areas. The first is the increased consumption of electricity, leading to environmental issues noted above for electric power generation. Although a recent study indicated that the existing power generation system can accommodate significant penetration of plug-in hybrid electric vehicles (PHEVs), the study also pointed out that "Higher system loading could impact the overall system reliability when the entire infrastructure is used near its maximum capability for long periods" [68]. The study also noted that, if significant numbers of vehicles were being charged during load "valleys," the impact on the generating system could be to emphasize more base-load type generation as opposed to the smaller units installed to meet peak demands. This could result in overall greater energy and environmental efficiencies; although the report also noted that maintenance scheduling could be more difficult in the absence of current cyclical load patterns.

Overall, it is estimated that GHG and other emissions would be reduced by broad use of PHEVs, based on a national average 33-mile round trip length. The reductions would vary by region, and in some locations with very high coal generation, total emissions could increase. In the U.S. Northeast, for instance, GHG emissions could be reduced by 39% and NOx emissions by 59%, while in the Northern Plains, GHG emissions could increase by 1% and NOx emissions by 35% due to the high reliance on coal-fired generation [68]. Although these results are for PHEVs, the general results will hold for all-electric vehicles as well, because the study assumed that the PHEVs would be able to operate in all-electric mode for 33 miles, with longer trips being powered by fossil fuels.

The second implication is related to the increase in production and disposal of the electric storage system. Current all-electric vehicles use batteries as the energy storage system, although there has been considerable work to develop ultra capacitors that would allow rapid charging and higher power density. The most common type of battery now in use is the nickel-metal-hydride (NiMH) battery, with lithium (Li) ion, Li ion polymer, valve regulated lead acid (VRLA), and nickel-cadmium batteries also are under development for vehicle use. Increased use of NiMH batteries will necessarily require significant increases in nickel (Ni) production and the associated impacts associated with Ni mining and refining. Lave et al. noted that the key issues may be with the other metals needed for NiMH or Li ion batteries, cerium and cobalt, which tend to be present as minor trace elements in other metal ores and are more difficult to extract. This would lead to additional environmental consequences as large amounts of ore would need to be processed to obtain the necessary amounts of metals, even at the relatively low levels of penetration assumed by Lave et al. in their analysis (11% of the fleet for NiMH and 22% for lithium ion) [69]. Similarly, Andersson and Rade evaluated the long-term resource constraints associated with substantial penetration of electric vehicles. Such increased demand would likely result in increased metal prices and subsequent increases in metal mining and refining [70]. Vimmerstedt et al. evaluated the recycling of lead from lead-acid batteries that could be used in vehicle propulsion systems, and noted that lead recovery facilities may need to install additional infrastructure such as backup power generation to ensure adequate environmental protection [71]. Current battery recycling programs recover 90-95% of lead in batteries, but presumably this would increase as replacement of propulsion batteries moved to professional shops rather than being done by vehicle owners at home.

Lithium ion batteries have received considerable attention as a promising battery technology. If anticipated improvements are achieved using Li, it is likely that lithium extraction and processing will increase substantially, with a corresponding increase in potential releases of Li into the environment. Lithium has long been used to treat aggressive behavior [72]. The potential health effects of its long-term use have been evaluated in this context, with the finding that there are few effects even at intake levels that are much higher than would be typical of environmental exposure [73]. However, there is some indication that there are adverse impacts associated with Li concentrations in the ambient environment [74], although additional studies are needed to more fully understand the potential impacts.

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