Electric vehicles (EVs) have long been advertised as the “green” answer to the world’s growing transportation problem as our cities struggle against the effects of global warming, smog and air pollution. They also dominate the public arena, from celebrities driving luxury EVs (just look at Justin Bieber’s 18th birthday present) to government subsidies and major infrastructure upgrades encouraging us to “go green” and buy electric cars (cities such as Denver and Fort Collins, CO are spending hundreds of thousands of dollars to offer charging stations at airports and public parking stations). Recently, however, EVs have come under scrutiny as to whether they really are a more environmentally-friendly option for consumers. While it is true that running an EV causes no exhaust emissions, there remain some key environmental concerns regarding the energy sources used to charge EVs, as well as the impacts of vehicle production.
Popular culture and advertising firms might characterize EVs as “emission-less,” but that’s hardly the case. EVs are powered by electricity, over 68% of which is from fossil fuels in the United States, and the largest percentage of which is coal-powered. Is burning coal, then, better than burning gasoline? Jason Haraldsen, a post-doctoral researcher at the Los Alamos National Laboratory and Assistant Professor at James Madison University, has explored this question, calculating the energy and CO2 released by both coal and gasoline. He found that burning gasoline gives you about twice as much power as burning coal, with fewer CO2 emissions per MJ of energy. According to these calculations, coal power is more detrimental to the environment (while producing less energy) than gasoline.
Taking this calculation further and considering the fact that electric engines are more efficient than combustion engines, however, the scale tips more evenly. Electric engines require only 144 MJ of energy to go 100 miles, whereas less efficient combustion engines require 215 MJ. While more coal is needed to go 100 miles compared to gasoline (6kg of coal versus only 4.7kg of gasoline), the more efficient electrical engine does save about one pound of CO2 entering the atmosphere compared to traditional engines. An EV powered by natural gas comes out even better, with roughly the same power generated per kg as gasoline, but releasing about 10 pounds less CO2 than gasoline.
This gives us hope, but emphasizes the importance of the energy portfolio of the electricity used to charge an EV, especially in the US as energy sources vary greatly by region. The Southeast and Midwest rely the most on coal and natural gas, while in the West and Northeast you’ll find a lot more energy from renewable sources. So is an EV owner in Los Angeles a better environmental steward than one in Atlanta (the third fastest growing market for EVs like the Nissan Leaf)? Arguably yes, but there are drawbacks to renewables as well.
Solar cells, a common emissions-free energy choice, are actually very energy-intensive to produce and, for the most part, are too slow to power EVs. Solar cells are products of fossil fuels, and their manufacture releases heavy metals that can have 23,000 times as much global warming potential as CO2, according to the IPCC. While renewable energy is still preferable to dirtier sources like coal, it’s important to know that nothing is a totally clean source of energy to power vehicles.
When we look at the “greenness” of EVs, the biggest risk comes from environmental impacts over the vehicle’s entire lifecycle. According to a 2012 study by the Norwegian University of Science and Technology, the production of EVs has about twice the Global Warming Potential (GWP) (87-95 grams of CO2 equivalent per KM) as that of traditional cars (43g CO2-eq/km). Production of the batteries is the most significant concern, contributing up to 41% of the GWP for EV production.
EV batteries traditionally use cathodes with nickel and cobalt, both of which have dangerous impacts on environmental and human health, increasing the Human Toxicity Potential (HTP) by 180% to 290% over traditional combustion engine alternatives. The current trend to switch to lithium-ion batteries has also caused concern over safety and health, as they contain dangerous metals such as copper, nickel and lead, as well as flammable electrolytes linked to a number of recently reported fires.
So where are we left when considering the environmental impact of EVs? Can they still be a solution to the growing demand for transportation and the increasing threats of pollution and global warming? While the 2012 Norwegian study did find that the residual effects of EV production are much worse for the environment than traditional cars, it also found that running EVs on the current electricity mix in Europe (which includes much more renewable energy than on average in the US) offers a 10%–24% reduction in Global Warming Potential (GWP) relative to traditional cars over a lifetime of 150,000km, or even up to 30% for a 200,000km lifetime.
That’s good news for countries moving toward renewable energy, including the US if it continues to move away from coal and gas electricity. While a Chevy Volt owner in Atlanta is probably not any more environmentally friendly today than a traditional car owner, that could change as we incorporate more renewable energy into our economy. Battery and component technologies are also improving, with less toxic alternatives being discovered and incorporated every new car season. While the environmental benefits of electric vehicles may not be as big as we all think right now, continued demand, more renewable energy and improvements in technology means the outlook for electric cars is getting better every year.
Correction, 09/30/13: This article originally stated that Jason Haraldsen is a researcher at Los Alamos National Library. He is a researcher at Los Alamos National Laboratory.
Image Credit: NRMA Motoring and Services from Sydney, Australia (2011 Chevrolet Volt)