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Paul Stenquist of the New York Times attempted to educate us last Sunday by suggesting that pollution from electric cars is as clear as a sixth grade math problem. However, by 9th grade, we should begin to understand that although we can add any numbers together, it is the relationship between those numbers and something in the real world which gives us sensible results.


Are Electric Cars “Green” No Matter Where You Plug-In?

Paul Stenquist of the New York Times attempted to educate us last Sunday by suggesting that pollution from electric cars is as clear as a sixth grade math problem. However, by 9th grade, we should begin to understand that although we can add any numbers together, it is the relationship between those numbers and something in the real world which gives us sensible results.


Paul Stenquist of the New York Times attempted to educate us last Sunday by suggesting that pollution from electric cars is as clear as a sixth grade math problem. However, by 9th grade, we should begin to understand that although we can add any numbers together, it is the relationship between those numbers and something in the real world which gives us sensible results.

Programmers learn that many calculations can be made but that only when the right assumptions are used do we avoid the pitfall of: “garbage in, garbage out.” Mr. Stenquist is in pursuit of the “carbon footprint” for charging an electric vehicle. However, while the EV may have a carbon footprint that is related to its manufacture, the vehicle will never have a carbon footprint related to its operation. In part, this is because it is a zero emissions vehicle — while it is operating, there are no emissions. But will the vehicle produce emissions or, more to the point, be responsible for emissions while it is charging?

The Relationships Are Fundamental: EV / Owner / Power Plant

It is a convenient but inaccurate shorthand to say that an electric vehicle pollutes when, by definition, it is the human operator usage, not an object, that has a carbon footprint. We are used to simple answers for a petrol vehicle: Calculate the miles per gallon, add in that approximately 19 pounds of carbon dioxide are produced for every gallon burned, and you have a result. There is very little most operators can change. There is one engine and it takes one kind of fuel and the vehicle pollutes in its operation. We think of the operator as fixed, and the pollution from burning gasoline relatively fixed. Only the vehicle is a variable. So, we think of the vehicle as having a carbon footprint.

For an electric vehicle, as is pointed out in the Union of Concerned Scientists study that he relies upon and we have reported on elsewhere, the electricity that is used to charge a battery-operated vehicle can come from many sources. It may be an operator’s power choice that determines pollution levels. It may be a power plant mix that determines pollution levels. It may be the time of day for a charge that determines pollution levels. But it is not the vehicle. The vehicle does not produce emissions. In this case, it is the vehicle that is relatively fixed while the operator choices and power plant both offer elements that can change. It makes the least sense to identify the “carbon footprint” with the vehicle. The electric car is a “green vehicle.” The operator and the electrical source may not be. Yet, popular media and Paul Stenquist persists in discussing the greenhouse emissions of an electric car.

Attributing pollution from power plants to electric vehicles is also known as the “long tailpipe argument” and I have written on this previously. The argument tries to forge a relationship between polluting power plants and clean electric vehicles that will tarnish the pure emissions prospect for the EV. It is as if Mrs. EV decides to marry the only available guy in town — Mr. Polluting Power Plant. Should she be branded with a family history that she can’t change? To do so would be either an unjustified attack or ignorance.

We only have to examine the differences between gasoline and electric vehicles to see that the long tailpipe argument also stands upon two unmentioned assumptions. First, that the vehicle operator is not a variable in the equation. And second, like gasoline, for every unit of electricity being used some static unit of pollution is being produced. Even more fundamental, and unlike petrol vehicles, there is with a ZEV the possibility of comparing the clean renewable energy available to the number of vehicles in operation. With electric vehicles, it is probably a poor choice to compare the vehicle to electrical grid pollution levels at all.

Pollution Depends upon the Operator

If we have a petrol vehicle and go to the gas pump, our choices are limited and pollution is built into the engine and the fuel. An electric vehicle owner, however, can charge their vehicle at night or during the day to make a difference. They can seek or build clean sources of electrical power. No petrol owner is going to build their own refinery and their fuel choices are limited.

Pollution Depends upon the Time of Charging

Petrol production can continue 24/7 and each unit of pollution can be attributed to each unit of gasoline produced. Coal-fired power plants are the most emission-producing forms of electrical generation. They are also baseload power plants. They must be run 24/7 or suffer boiler failures. But electricity must be used as it is produced. Production tries to match demand but fails where there are many coal-fired power plants. Especially in areas with a high coal usage, there is likely to be an excess in generation capacity over the demand present at night. The plants are running in any event. They are polluting in any event.

In this case, each unit of pollution does not match each unit of electricity used. Some electric vehicles charging at that time will not be “responsibile” for any added pollution from these coal-fired power plants. The coal plants would be running and polluting in any event. The connection is broken because the nature of electrical generation is different from petrol production, which is a form of energy storage. In this case, the electric vehicle provides the energy storage. Paradoxically, where the electrical production is most polluting, the EV is most helpful in reducing that pollution (to the extent of unused capacity).

Measuring the Electrical Energy Mix is Always a Guess

We speak with authority about the electrical energy mix of an area or our country, but, in every case, we are using historical data to extrapolate our present situation. It is what we call an educated guess. The use of coal has been on a dramatic decline for electrical generation in the US for almost 10 years. Renewable sources of energy have been on the rise. In some areas of the country, wind power has out-produced all other forms of electrical production, for a time.


We like to count all the power sources in an area and make a guess what the average mix will be. We do this despite operator variability. We do this despite a varying grid energy mix or time of day usage, and then we have the hubris to ascribe pollution to the one fixed and non-polluting element, the electric car. But we also discuss carbon offsets. There is a sense that if we can reduce carbon production sufficiently, our activities will have a net zero impact.

We could examine the amount of electrical generation in an area that is provided by renewable energy. By comparing this to the equivalent heat energy, we can compare electrical energy to the energy provided by gasoline. From this, we could determine the number of electric cars that could be supported by renewable sources of electrical production. On a US national level, we would find that if we replaced all of our approximately 300 million vehicles with electrical-powered ones, we would require approximately 30% of our present electrical usage. About 1/3 or 100 million electrical vehicles could be powered using the available renewable energy in the US. If we added the 20% of our energy presently produced by nuclear energy, we see that we have enough emission-free electrical energy production in the US to power our entire fleet of vehicles. Up to 84% of these vehicles could be presently powered with no extra equipment if they were charged at night.

And while we pursued this zero emission alternative, the numbers of polluting petrol vehicles on the roads would be reduced.

Our present hope is to have 1 million electric vehicles on the road by 2015. This is about 1/3 of 1% of our fleet. Put in this perspective, concerns over the pollution of electric vehicle are insignificant and we already have enough renewable electrical energy production for many years and a much, much, much larger electrical vehicle fleet. But most interesting is that those areas in the center of the US with a high coal usage are also, because of the long distances between cities, most likely to adopt a limited numbers of electric vehicles. But those vehicles would be most helpful to the overall pollution picture in the areas.

The long tailpipe argument attempts to diminish an environmental rationale for buying an electric vehicle. But it is not the only rational. Cost and strategic reasons can be even more important and these are also mentioned in the UCSS executive summary:

[Electrical vehicle fueling from the electrical grid and not the gas pump will result] “…in significant reductions in the oil consumption, global warming emissions, and fueling costs of driving.”

There are many reasons to buy an electrical vehicle. In some of the most polluting areas of the country, they can be the brightest star. The connection between the EV and pollution is not a clear one and some writers can be drawn into the seductive call of misleading arguments. Precisely because EV energy supplies are so complex and likely of marginal impact to our overall pollution, it may be insignificant. At the very least, we can say that the long tailpipe argument is not a sound rationale to avoid a “green” electric vehicle choice.

Photo Credit: Wikimedia Commons

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We share this World; its past, present resources and our combined future. With every aspiration, the very molecules we use for life are passed to others through time and space so that each of us may be considered a Breath on the Wind. This part of the world's consciousness lives in NYC; has worked in law, research, construction, engineering; has traveled, often drawn to Asia; writes on Energy and Electric Vehicle issues and looks forward to all your comments.   "If you would persuade, you must appeal to interest rather than intellect." -- Benjamin Franklin


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