Will Electric Vehicles Really Reduce Pollution?

[Note to reader: topic sentences are in green; remaining weakness in red.]


The amount of pollution created by electric vehicles depends mostly on the source of the electricity used to charge them. This makes it impossible to determine if electric vehicles pollute less than internal combustion engine vehicles without considering where they are to be deployed and by what sources of electricity they are to be powered. An electric vehicle that is charged with energy from a clean source, like hydroelectric power, will produce very little pollution, while one charged with energy from an unclean source, like coal or oil, may produce more pollution than an internal combustion engine vehicle. The sources of energy for most regions fall somewhere between these two extremes. The use of electric vehicles will allow new possibilities in pollution control and management that may outweigh some of their potentia.l failings. While not ready to be used everywhere, electric vehicles have the potential to pollute much less than internal combustion engine vehicles.


Internal combustion engine vehicles are responsible for the vast majority of pollutants that plague urban areas today. Studies of the sources of air pollution have shown that transportation accounts for the majority of nitrogen oxide (54%) and carbon monoxide (89%) emissions in the United States [1]. Furthermore, internal combustion engines are also believed to be one of the largest single sources of carbon dioxide (28%) emissions [1]. [The next sentence undercuts main point of introduction by bringing up a new topic.] Internal combustion engine vehicles also generate other types of pollution, including sulfur oxides and hydrocarbons, however, the amounts generated by transportation are small compared to other activities.

These emissions are directly responsible for many of the air quality problems faced in major urban areas. For example, carbon monoxide readily bonds with hemoglobin in blood, taking the place that would normally be occupied by oxygen molecules. Exposure to high concentrations of carbon monoxide can cause death, essentially suffocating a person as their cells are deprived of oxygen. Nitrogen oxides are also problematic for urban dwellers because sunlight causes hydrocarbons and nitrogen oxides to react and form ozone. Even at low concentrations, ozone damages the body's cells and tissues and causes respiratory ailments. [The next sentence is not about air quality.] Although carbon dioxide is not directly harmful to us since we exhale a large quantity of it every day, it is believed to be a greenhouse gas, that is, it may affect global temperatures.

Pollution from power plants

Electric vehicles produce little or no pollution directly; most of the pollution associated with their use is created at the power plant that provides their electricity. In the case of localities with high percentages of electricity coming from very clean energy source,s the emissions associated with electric vehicles is negligible. A good example of this scenario is California, which derives only about 20% of its electricity from so-called dirty sources like coal and oil [2]. The primary sources of electricity in California are natural gas-burning power plants and hydroelectric generators; both are clean sources of energy. A study from the Natural Resources Defense Council and Environmental Defense Fund indicates that the replacement of all internal combustion engine vehicles with electric vehicles in the Los Angeles Basin may cause reductions of between 37% and 99% in all categories of transportation related pollutants except for sulfur oxides [3]. A more detailed comparison of the amount of pollutants emitted by electric vehicles and modern, catalyst equipped, internal combustion engine vehicles is given in table 1. The distinction, the the L.A. Basin, is important because there is very little coal-fired [poor word choice] electricity used in Los Angeles. The study also noted that most of the pollutants caused by the electric vehicles came from the small component of electricity generated by coal-fired power plants. These predictions [poor word choice] highlight the potential cleanliness of electric vehicles when charged with a clean power source.

Estimates of the pollution emitted by electric vehicles relative to modern internal combustion engine vehicles
A comparison of the pollutants emitted by internal combustion engine vehicles and electric vehicles charged by various energy sources. Notice that carbon monoxide and hydrocarbon emissions are negligible when using electric vehicles, but that the emission of sulfur oxides increases. Also note the increasing emissions of carbon dioxide, nitrogen oxides, and sulfur oxides that occur when using greater proportions of coal and oil derived electricity.
Region Studied LA Basin Germany Ideal Internal Combustion
Amount of Electricity from Coal or Oil 21% 49% 100% (for comparison)
Carbon Monoxide 0.007 0 0 1
Carbon Dioxide 0.34 1 2.5 1
Hydrocarbons 0.01 0 0 1
Nitrogen Oxides 0.27 1 3.3 1
Sulfur Oxides 1.72 10 25.0 1

While studies of the pollution-reducing ability of electric vehicles in California are quite favorable, they cannot be applied to the rest of the world as a whole. The truth is that when using electricity generated from dirty sources such as coal and oil, electric vehicles may actually create more of some pollutants than comparable internal combustion engine vehicles. A report by the U.S. General Accounting Office (GAO) cited a German study that estimated the environmental impact of electric vehicles with two distinct energy mixes: one comprised of only 49% coal-fired electricity, and one comprised solely of coal-fired electricity [1]. The estimates provided by the study are given in table 1. Assuming that 49% of an electric vehicle's charging energy being derived from coal, the study found that electric vehicles would cause comparable levels of nitrogen oxides and carbon dioxide to be emitted, and that sulfur oxide emissions would increase by a factor of 10 [1]. Furthermore, when assuming that an electric vehicle is charged with 100% coal-fired electricity, the study estimated that the electric vehicles would emit 150% more carbon dioxide, 250% more nitrogen oxides, and 2400% more sulfur oxides than a comparable internal combustion engine vehicle [1].

While these coal-fired electric vehicles will emit more of some pollutants, they still will emit less carbon monoxide and hydrocarbons than a comparable internal combustion engine vehicle. The GAO reported noted that mandatory pollution controls at power plants ensure that electric vehicles will always produce less carbon monoxide and hydrocarbons than internal combustion engine vehicles, regardless of the source of the electricity [1]. The German study offers some insights into how electric vehicles would perform in the United States. Their value of 49% represents the portion of German electricity generation that is based on coal, and is close to that of the United States, which, as a whole, derives 55% of its electricity from coal and oil [4]. We can expect similar results for the United States, namely, that while electric vehicles produce much less carbon monoxide and hydrocarbons, they use similar levels of nitrogen oxides and carbon dioxide, and increased levels of sulfur oxides.

Not all pollutants related to electric vehicles arise from t he generation of electricity. Any discussion of the environmental impact of electric vehicles must also take into consideration the problems associated with the manufacturing and disposal of their batter packs. The typical electric vehicle contains no less than half a ton of batteries (often of the lead-acid variety) that need to be replaced every 20-25 thousand miles [1]. There have not been any definitive studies on the pollution caused by the manufacture and disposal of these batteries, as no one is sure what the batteries used in production electric vehicles of the next century will be like. Furthermore, since current electric vehicle batter packs have not yet begun to produced on a large scale, say, in the million of units per year, there is little hard data available on their environmental impact. The prevailing opinion is that the batteries will not pose much of an environmental problem because of their large weight and high cost. The rationale is that since electric vehicle battery packs weigh several hundred pounds and cost several thousand dollars, they will most likely be replaced by certified repair centers, that will return them to the manufacturer for recycling. Unlike regular car batteries, it will not be economical to simply throw electric vehicle battery packs away when they can no longer hold a charge. The batteries will most likely be refilled, and the original contents recycled, just as motor oil is today.

Enhanced control of pollution at the source

While electric vehicles may not always hold an outright advantage in terms of pollution reduction, they allow for more control over the pollution that is generated. Because electric vehicles emit little or no pollution directly, their use would shift the source of emissions from the individual vehicle to the electric power plants, allowing more precise measurements of the amount of pollutants emitted. Using this information, regulators could conceivably rotate the operation cycles of power plants to keep local emissions in line with air quality regulations. Since the electricity used to power electric vehicles could come from all over the region, pollutants could be redistributed away from crowded urban areas where they are potentially more dangerous. One foreseeable problem with this redistribution approach is the greatly increased emission of sulfur oxides that will result when electric vehicles are powered by coal-fired electricity. The abundance of sulfur oxides produced by coal-fired power plants in the Northeast has already manifested itself in the form of acid rain. It is unlikely that the addition of several million power-hungry electric vehicles will alleviate the problem, as more coal-fired power plants would be brought on-line to meet the extra demand (keep in mind that coal is the most cost-effective means of generating electricity in the Northeast and it will remain so for many years to come.) Even with the potential of increased occurrences of acid rain, several Northeastern states are considering the use of electric vehicles to reduce carbon monoxide and hydrocarbon emissions in urban areas.

The use of electric vehicles would allow even further decreases in auto emissions over time because only about 10,500 power plants will have to be monitored, maintained, and upgraded as opposed to the over 100 million private automobiles. [4] Despite the vast amounts of money spent each year in this country to maintain the emissions systems of gas-powered automobiles, cars generally emit more pollution as they age. Deterioration of the catalytic converter and other critical emissions control components eventually leads to an increase of emissions from older cars. Electric vehicles would not suffer from this problem because electric power plants receive more maintenance at regular intervals than would be afforded to a private automobile. In fact, the U.S. Government already maintains a strict testing schedule for electric power plants, making sure that they comply with emissions standards once a month. Another advantage of this centralized approach is that any new pollution reduction technologies can be universally applied to every electric vehicle by simply upgrading the power plants.

Because so many tradeoffs in local versus global pollution are involved, it is impossible to say with certainty that electric vehicles provide the best short term solution to transportation related pollution. The example of sulfur oxides in the Northeast is but one instance where electric vehicles may prove more harmful to the environment than their internal combustion counterparts. it is likely that some localities may be better served by internal combustion engine vehicles with more stringent pollution controls. Government officials in Germany have concluded that, for the time being, catalyst-equipped internal combustion engine vehicles would reduce pollution more than electric vehicles [1]. They came to this conclusion because most of Germany's overflow electricity generation is coal-based, that is to say, as electricity demand increases, the percentage coming from coal-fired power plants increases. It was their final opinion that "the broad-scale introduction of electric vehicles into the Federal Republic of Germany is justifiable only if the zero emission at the place of use is considered more important than the increased emissions at the power plant." Many regions around the world will face similar decisions regarding the importance of local pollution reduction versus the effect on the global environment.


At present, for the vast majority of the country, neither electric vehicles or comparable gasoline-powered vehicles holds a solid advantage over the other in cleanliness. This balance will probably not change any time in the near future as the problem with electric vehicles is not inherent to them, but rather to the means by which we generate our electricity. Although electric vehicles offer some compelling advantages over internal combustion engine vehicles in terms of pollution management, the real advantage of electric vehicles lies in the future when more electricity is produced from cleaner sources. For those living in California, or in other regions with a high percentage of energy production coming from clean sources, the future is already here.



[1] Electric Vehicles: Likely Consequences of U.S. and Other Nations' programs and Policies. (1994). In Gateway Japan [Online]. Available: http://www.gwjapan.org/ftp/pub/policy/gao/1994/95-7.txt [20 November 1995].
[2] California Historical Energy Statistics. (1995). In California Energy Commission [Online]. Available: http://www.energy.ca.gov/reports/stats/statistics.html#electricity [8 July 1996].
[3] Francis Chapman, Chris Calwell and Diane Fisher. (1994). What's the Charge? Estimating the Emissions Benefits of Electric Vehicles in Southern California. In Calstart Resources [Online]. Available: http://www.calstart.org/reference/papers/emission.html [No Date].
[4] US Energy Information Administration Annual Energy Review 1995. (1996). In US Energy Information Administration [Online], Available: http://www.eia.doe.gov/emeu/aer/contents.html [15 April 1997]. See table 4.

Your comments and suggestions are appreciated.

Edited by: wilkins@mps.ohio-state.edu [August 1997]