|Fig. 1: All-electric car battery at CODA Automotive. (Source: Wikimedia Commons)|
It is mostly thought that electric vehicles (EVs) are far less harmful for the environment than traditional internal combustion engine vehicles (ICEVs). Since EVs do not emit any greenhouse gases while they are being driven, one is easily led to think that they have no environmental footprint. This is untrue for a number of reasons. Firstly, EVs run on electricity, and in the United States most electricity is generated from the combustion of fossil fuels. According to the US Energy Information Administration, as of January 2015 fossil fuels meet 82% of US energy demand.  Secondly, the production of EVs has a significantly larger enviromental footprint than that of ICEVs. This is mainly because of their intricate lithium-based batteries (Fig. 1), which are costly to make and even more costly to dispose of. Whether these environmental drawbacks are enough to reconsider electric vehicles as "green alternatives" will be the subject of our inquiry here.
In a 2012 paper published in the Yale Journal of Industrial Ecology, a team of researchers lead by Dr. Troy Hawkins gauged the overall environmental impact of the production of EVs.  Their study centers on EVs powered by lithium iron phosphate batteries and lithium nickel cobalt manganese batteries, the latter being marginally more energy-efficient and thus environmentally-friendly. It finds that as a whole the global warming potential (GWP) of producing electric vehicles is in the region of 87-95 grams carbon dioxide equivalent per kilometer, of which battery production contributes roughly 40%. It is about twice the 43 g CO2~eq/km associated with the production of ICEVs. Thus, producing the battery of an EV is about as costly to the environment as producing an entire ICEV. This is because the metals used in making the batteries- cobalt, lithium, lead, nickel- are mined mainly in South America and Australia. As such, the environmental costs associated with their extraction and transportation are very high.
Hawkins et al.'s overall life cycle analysis of European EVs versus ICEVs shows that despite having twice as large a GWP in production phase, EVs typically had a lesser GWP over their entire lives. They estimate that from its production until its retirement, an EV has a GWP that is 20%-24% less than that of an equivalent gasoline powered ICEV, and 10%-14% less than that of a diesel-powered one.
These figures are contingent upon a number of important assumptions. The expected vehicle lifespan of a vehicle is 150,000 km, which is generous for an EV. The marginal benefit of EVs shrinks when this expectation is reduced to 100,000 km. Secondly, and perhaps most importantly, the assumed energy source for powering the EVs is average European electricity. This is another favorable assumption, as Europe is heavily invested in renewable energy, and no more dependent on coal than it is on nuclear.
As such the GWP associated with EVs' power consumption is low in Europe. In a country such as China, which relies more heavily on "dirty" energy, the use phase GWP of EVs is far more significant and may actually exceed that of ICEVs. In 2012, a study of the externalities associated with EV and ICEV usage in Shanghai showed that because of their dependency on coal-generated power, EVs in Shanghai were of greater harm to air quality than ICEVs overall. 
The Lithium batteries that power EVs are difficult to dispose of and harmful to the environment. They contain toxic metals- namely nickel, lead and copper- as well as toxic and flammable electrolytes containing LiClO4, LiBF4, and LiPF6. Exposure to these materials during the battery production phase is strictly regulated by US federal law, but the legislation on their disposal is inconsistent internationally. They present a serious human hazard, especially in areas that lack the infrastructure for solid waste collection and recycling, both in the US and abroad. There is an additional threat: even discharged EV batteries can deliver powerful shocks, or present a serious fire hazard, if mishandled. 
Recycling EV batteries is, as a whole, expensive yet feasible. There is little incentive for manufacturers to recycle EV batteries when Lithium- their "main ingredient" - costs five times more to recycle than to produce. EV manufacturers have attempted different ways to reduce costs. Toyota is shipping used American Prius batteries back to Japan, where it can recycle at lower cost; GM and Nissan have started selling used batteries to power companies for the storage of excess wind and solar energy. While these recycling methods have been successful in mitigating the damage caused by EV battery disposal, they are costly and still far from being protocol. Specialized EV battery recycling plants are appearing, but only by the graces of government subsidy. In 2011 The US department of energy funded a $9.5 million dollar EV battery recycling plant in Ohio, today managed by Toxco. Efforts in the UK are still in their experimental stages.
We can fairly conclude that whether or not buying an EV is an environmentally friendly decision depends on where you are in the world, and how sustainable power is there. EVs are significantly more pollutant than ICEVs in production phase; but they will make up for it over the course of their usage if they run on relatively clean power. If they do not, then they are found both to pollute more and cause more deaths than ICEVs.
The threat posed by the disposal of EV batteries is still difficult to quantify. It is a human hazard rather than a global warming threat, which persists though infrastructure for recycling the batteries is in place. However, it remains an inaccessibly expensive technology, so for now the long-term fate of EV batteries remains undetermined.
© Louis Lambilliotte. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "Monthly Energy Review," U.S. Energy Information Administration, DOE/EIA-0035(2015/05), May 2015, Table 1.3.
 T. R. Hawkins et al., "Comparative Environmental Life Cycle Assessment of Conventional and Electric Vehicles," J. Ind. Ecol. 17, 53 (2013)
 S. Ji et al., "Electric Vehicles in China: Emissions and Health Impacts," Environ. Sci. Technol. 46, 2018 (2012).
 J. Kanter, "Fancy Batteries in Electric Cars Pose Reycling Challenges, New York Times, 30 Aug 11.