Just how environmentally friendly are electric vehicles?
By Darren Quick
August 31, 2010
Because they produce no exhaust gases in operation electric vehicles (EVs) are seen as the eco-friendly alternative to conventional gas-fueled cars. While zero-local emissions is clearly a big plus, other factors contributing to the overall environmental impact of EVs are often overlooked – namely the manufacture, usage and disposal of the batteries used to store the electrical energy and the sources of power used to charge them. Now, for the first time, a team of scientists from the Swiss Federal Laboratories for Materials Testing and Research (or EMPA) have made a detailed life cycle assessment or ecobalance of the type of lithium-ion batteries most frequently used in EVs, to see if they really are as environmentally friendly as their manufacturers would have us believe.
Fuel source is the keyThe investigation shows that, if the power used to charge the battery is not derived from purely hydroelectric sources, then it is primarily the operation of the EV that has an environmental impact, exactly as is the case with conventionally fueled vehicles. In other words, the size of the environmental footprint depends on which sources of power are used to “fuel” the EV. Contrary to initial expectations that the manufacture of the batteries could negate the advantages of electric drive vehicles, the Li-ion battery itself was actually found to have a limited effect.
The team calculated the ecological footprints of electric cars fitted with Li-ion batteries, taking into account factors such as those associated with the production of individual parts, the operation of the vehicle during its lifetime, all the way through to the scrapping of the vehicles and the disposal of the remains. The electric vehicles evaluated were equivalent in size and performance to a VW Golf, and the power used to charge the batteries was assumed to be derived from sources representing an average European electricity mix – that is, a mixture of atomic, coal-fired and hydroelectric power stations.
For comparison the team used a new petrol-engined car, meeting the Euro 5 emission regulations. It consumes on average 5.2 liters (1.37 U.S. gallons) per 100km (62 miles) when put through the new European Driving Cycle (NEDC), a value significantly lower than the European average. In this respect, therefore, the conventional vehicle belongs to the best of its class on the market.
ResultsThe study shows that the electric car’s Li-ion battery drive is in fact only a moderate environmental burden. At most only 15 per cent of the total burden can be ascribed to the battery (including its manufacture, maintenance and disposal). Half of this figure, that is about 7.5 per cent of the total environmental burden, occurs during the refining and manufacture of the battery’s raw materials, copper and aluminum. The production of the lithium, in the other hand, is responsible for only 2.3 per cent of the total.
“Lithium-ion rechargeable batteries are not as bad as previously assumed,” according to Dominic Notter, coauthor of the study which has just been published in the scientific journal Environmental Science & Technology.
The outlook is not as rosy when one looks at the operation of an electric vehicle over an expected lifetime of 150,000 kilometers (93,205 miles). The greatest ecological impact is caused by the regular recharging of the battery, that is, the “fuel” of the e-car. Topping-up with electricity sourced from a mixture of atomic, coal-fired and hydroelectric power stations, as is usual in Europe, results in three times as much pollution as from the Li-ion battery alone. If the electricity is generated exclusively by coal-fired power stations, the ecobalance worsens by another 13 per cent. If, on the other hand, the power is purely hydroelectric, then this figure improves by no less than 40 per cent.
The EMPA team concluded that a petrol-engined car must consume between three and four liters per 100km (or about 70mpg) in order to be as environmentally friendly as the electric car studied, powered with Li-ion batteries and charged with a typical European electricity mix.