Compared to gasoline powered cars, electric cars may be worse for the environment and for climate change, according to a new analysis published in the Proceedings of the National Academy of Sciences. It depends on where your electricity comes from.
The authors performed a lifetime analysis in which they estimated not only the pollution and emissions that come from the tailpipe of your car, but also the pollution and emissions resulting from manufacturing the fuel. So, for instance, oil has to be extracted from the ground, refined, and transported to your local gas station. All of that causes both pollution and GHG emissions. Similarly, an electric car requires a battery. The chemicals used in the battery have to be mined, and the battery has to be manufactured. Then the battery must be charged with electricity, which has to be generated. All of this mining, manufacturing, and generating causes both pollution and GHG emissions. The study estimates the total amount of pollution from all of these processes.
The authors studied gasoline and 10 alternative fuels that are commonly discussed as future gasoline alternatives:
- Gasoline hybrid
- Concentrated natural gas
- Corn grain ethanol
- Corn stover ethanol
- EV charged by grid average electricity (“EV” = electric vehicle)
- EV charged by electricity from coal
- EV charged by electricity from natural gas
- EV charged by electricity from corn stover
- EV charged by electricity from wind, water, or solar
The authors weren’t interested in comparing results across states, so they did not look at differences in electrical generation between states. They focused on differences between the fuel types.
They found that in the future all fuel types resulted in increased emissions and pollution. This is because the number of miles driven is expected to increase in the future. I want to emphasize this point, because otherwise some of the charts below may give the wrong impression. Environmental damage from automobiles is projected to increase because more miles are expected to be driven.
However, compared to gasoline, some alternative fuels are projected to produce less harm, and some more harm. The chart at right shows the damage from the 10 alternative fuels relative to gasoline. Bars on the negative side of the chart do not mean damage will be reduced, they only mean that damage will increase less than in the case of gasoline. The black portion of the bar represents damage from pollution, the white portion of the bar represents damage from climate change.
(Click on chart for larger view.)
Compared to a regular gasoline powered car, an electric vehicle charged with electricity from wind, water, or solar is the best, causing about $0.40 less in pollution damage per gallon of gasoline equivalent, and about $0.50 less in climate change damage. Corn stover ethanol is second best, though its advantage is almost entirely from reduced climate change damages. Third best is an electric vehicle charged with electricity generated by burning natural gas.
The worst scenario involved an electric vehicle charged with electricity from coal. It had almost $1.50 more pollution damage per gallon of gasoline equivalent than a standard car, plus another $0.10 or so from climate change damages. Second worst was an electric vehicle powered by grid average electricity. Third worst was a car powered by corn grain ethanol. Most of Missouri’s electricity is generated by burning coal, so that makes Missouri a state in which an electric vehicle would be particularly damaging.
The series of maps at right shows the projected concentrations for PM2.5, particulate matter smaller than 2.5 microns in diameter. I discuss it briefly in Update on Missouri Air Quality. Many experts feel it to be the form of air pollution that causes the most damage to human health.
In the series of maps, the blue and red map at upper left shows the baseline concentration of PM2.5; it should be read against the colored bar on the lower left. The remaining 12 maps show the changes in PM2.5 levels expected in the future, and should be read against the colored bar on the lower right.
Notice that every fuel causes an increase in the PM2.5 level. However, there are some stark differences. The increase from electric vehicles charged by electricity from coal really turns the map red, as if the country were bleeding. Electric vehicles charged by electricity from the grid average, and vehicles powered by corn grain ethanol are nearly as bad.
Notice that Missouri is in the region of maximum damage from EV Coal and from corn grain ethanol.
The fuel that causes the smallest increase in PM2.5 is an electric vehicle charged by electricity generated from wind, water, or solar. That map is almost white, only very slightly pink in some areas. The map for natural gas appears to be the next whitest, and the one for gasoline hybrid appears to be the third whitest. You can do a lot worse than simply driving your good old hybrid.
Tessum, Christopher W., Jason D. Hill, & Julian D. Marshall. 2014. “Life Cycle Air Quality Impacts of Conventional and Alternative Light-Duty Transportation in the United States.” Proceedings of the National Academy of Sciences, Vol 111 (32), 18490-18495. http://www.pnas.org/content/early/2014/12/10/1406853111.abstract?