Tuesday, August 30, 2016

Is an electric car really better for the environment?

The Question

A family member recently asked me this...

"I read that hybrid cars are not environmentally friendly because they use rare minerals (from China) that destroy the land as they are mined.  Also, the battery does not last long so when it is tossed, it also pollutes the soil. Regular petrol cars have improved in mileage and pollutants and are pretty much environmentally safe."

She also forwarded an article from The Economist that reviews a published paper from the Proceedings of the National Academy of Sciences, focusing on the number of lives lost from air pollution over the life cycle of various cars. 


The Short Answer

Electric cars are better for the environment. 

The Long Answer

I recently attended a lecture at the Commonwealth Club. One of the guest speakers was Dr. Mark Jacobson, a professor of environmental engineering at Stanford. He had three points about the current state of things. 

1. Electricity is more efficient than gasoline. In an electric car, 80% of the energy is used to propel the car forward and 20% is lost to waste heat. In a conventional car, 20% is used to propel the car and 80% is lost to heat. 

2. Mining for oil is indefinite. Mining for rare minerals is not. Mining for minerals is "orders of magnitude better for the environment" than mining for fossil fuels. 

3. Given the current energy mix, air pollution from conventional cars leads to significantly more deaths (more on this topic a bit later). And those deaths disproportionately affect the poor.  

He also had a few things to say about the likely future state of things.

1. Scientists are currently studying how to efficiently recover rare minerals from recycled consumer products. In the future, it is possible that the majority of rare minerals will come from existing stock, not mining. 

2. Electric cars can support a smarter, more flexible energy grid by using their batteries to store up energy in off-peak times.

3. Renewable energy (wind, water, solar, etc) is getting cheaper and more efficient every year. 

Now let's tackle that article from The Economist....

First off, the article grossly misinterprets the findings from the scientific paper. In the paper, the authors state that they ran a variety of simulations to see which scenarios were better or worse in terms of the number of deaths caused from air pollution. For example, in scenario A all cars were conventional. In scenario B all cars were electric cars, where the electricity came from coal power plants. In scenario C all cars were electric and the electricity came from solar and wind. And so on for 11 different scenarios. In the scenario where all cars are electric and the electricity comes from coal power plants, there were more deaths than the scenario with conventional cars. 

But the current mix of energy is nowhere near 100% coal. In fact, coal has been declining as a source of energy over the last few decades in the United States (currently it is near 30% of the mix). The authors are very upfront about the fact that their assumptions have obvious limitations. They realized that they could not predict what the energy mix will be years into the future, so they had to create baselines. 

Let's be clear that I am not blaming the scientists who wrote that paper. I think that their underlying methodology was clearly explained, along with the pros and cons. The fault lies with The Economist. The newspaper used a provocative title to draw in readers, but waited until the very last paragraph to discuss where the energy comes from. 

Just to reiterate, given current trends, the most likely scenario is where electricity comes from sources other than coal. Under those conditions, the scientific paper states that electric cars will save vastly many more lives. 

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