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Why Your Electric Vehicle Might Not Be as Green as You Think

Electric vehicles don’t reduce air pollution and improve health unless they’re combined with a move toward alternative ways to generate electricity, scientists confirm.

Will electric vehicles really lead to cleaner air and healthier people? Only if they are coupled with cleaner ways of generating electricity, scientists say in a new study today.

It’s a familiar back-and-forth: Advocates alternative energy vehicles point to their positive environmental qualities, such as reducing carbon emissions from the tailpipe. Their opponents point out the hidden costs, such as the fact that the energy for electric cars comes largely from burning coal. Scientists want to attach some hard numbers to this debate. And so a team led by Christopher Tessum, an environmental engineer at the University of Minnesota, Minneapolis, set out to study the effects on human health of various alternative ways to power a car. Their findings are presented today in the Proceedings of the National Academy of Sciences.

The researchers investigated ten alternatives to gasoline. They include diesel, compressed natural gas, ethanol derived from corn, and ethanol derived from cellulose, as well as electric vehicles powered in six different ways: by electricity from coal, natural gas, corn leaf and stalk combustion, wind, water, or solar energy. They then modeled the effects of replacing 10 percent of U.S. vehicles that currently run on gasoline by 2020.

Jason Hill, study co-author and environmental engineer at the University of Minnesota, says it’s important to note that this is a study about pollutants and how they affect human health—not about climate change. “We looked all the way from all the stages of production and use of a fuel, such as extracting, refining and transporting it, to the way it changes ozone levels and atmospheric pollutant concentrations,” he says. “We also looked at where people live in the United States and used meteorology and chemical transport models to see how often and how much people would be exposed to pollutants, calculated damage to health, and the economic costs associated with this damage.”

The findings showed a dramatic swing the positive and negative effects on health based on the type of energy used. Internal combustion vehicles running on corn ethanol and electric vehicles powered by electricity from coal were the real sinners; according the study, their health effects were 80 percent worse compared to gasoline vehicles. However, electric vehicles powered by electricity from natural gas, wind, water, or solar energy might reduce health impacts by at least 50 percent compared to gasoline vehicles.

“We were surprised that many alternative vehicle fuels and technologies that are put forward as better for the environment than conventional gasoline vehicles did not end up causing large decreases in air quality-related health impacts,” Tessum says. “The most important implication is that electric vehicles can cause large public health improvements, but only when paired with clean electricity. Adapting electric vehicles without taking steps to clean up electric generation would be worse for public health than continuing to use conventional gasoline vehicles.”

EV batteries are a problem, too, but a changing one. According to Tessum, previous studies have suggested that emissions from electric car battery production make such vehicles worse for public health than gasoline vehicles, even when the electricity to power them comes from non-polluting sources. “However, battery technology is evolving quickly,” he explains.” Using updated estimates of emissions from battery production, and accounting for the fact that much of the pollutant emissions from the battery production supply chain occurs in remote areas far from people, we found that the health impacts of electric vehicle battery production are much lower than previously estimated.”

In the future, Tessum says, the team wants to explore the potential impacts of alternative fuel use outside the United States. “We can also investigate if some areas might benefit more from electric vehicles than others, to know if there are ways to deploy electric vehicle fleets for optimal impact,” Hill says. “Perhaps subsidies or tax breaks could help those areas benefit most.”

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