So Just How Green Are Electric Vehicles, Really?

These days you can practically generate electricity writing about electric vehicles. The topic has become a lightning rod for partisan rhetoric. For some, the EV personifies everything evil about government influence and free markets. From the other side, you might get the impression that the EV is the salvation of humankind and planet Earth.

Recent research into the environmental and energy impacts of EVs has revealed that the picture is (surprise) more nuanced than the extremists might like to admit.

Just considering “pure” battery electric vehicles (BEVs) — i.e., completely grid-dependent EVs — the International Energy Agency (IEA) estimates the global stock rose from about 180,000 vehicles in late 2012 to 665,000 units at the end of 2014, with the US leading the way at 39% of the market. The movement of BEVs is increasing rapidly, shooting up from 45,000 sold worldwide in 2011 to more than 300,000 in 2014.

EVs now account for more than 1% of new car sales in the US, Norway, Sweden, and the Netherlands. The automobile isn't the only transportation mode that's going electric. IEA says that at the end of 2014, the global stock of electric buses stood at 46,000; electric two-wheeled bikes were at an astonishing 235 million units.

Debates over the greenness of vehicle technologies tend to center around tailpipe emissions. To evaluate lifecycle emissions of a vehicle, you have to go beyond driving emissions (the air pollutants resulting from operating the vehicle).

EVs offer an important environmental benefit via their zero tailpipe emissions (kind of a paradoxical term, as an EV has no tailpipe.) Zero emissions are clearly valuable in an urban setting.

However, critics point out that the electricity an EV needs has to be generated somewhere, so the zero-emissions descriptor ignores the air pollutants emitted during power generation.

Both observations have merit. A MIT study found that air pollution causes 200,000 premature deaths per year in the US. Out of those deaths, 53,000 can be attributed to road transportation and 52,000 to power generation. The study found that the danger tends to be localized, i.e., those living or working close to the emissions are more likely to be killed by them.

The National Academy of Sciences recently released a study by a team at the University of Minnesota that considerably updates our understanding of the air-quality impacts of light-duty vehicles in the US. The group, led by biosystems engineering researcher Christopher W. Tessum, compared 10 alternatives to conventional gasoline vehicles, including gasoline hybrids, diesel vehicles, compressed natural gas (CNG) vehicles, and corn and cellulosic ethanol vehicles. The researchers also studied the environmental impacts of BEVs powered by electricity generated by various sources, including coal, natural gas, an average US power-generation mix, and a mix of renewable sources (wind, hydro, and solar).

Tessum calculated the lifecycle health impacts of emissions from the 11 types of passenger cars (conventional gasoline plus the ten alternatives). Because this was a lifecycle analysis, the study took into account emissions during both production (manufacturing) and consumption (tailpipe), examining health effects of ground-level ozone (O3) and fine particulate matter (PM2.5).

The researchers confirmed that the air-quality impacts of EVs really do depend on how their power is generated. Their study showed that vehicles powered by coal-generated electricity, corn ethanol, or grid-average electricity increased health impacts by 80% or more relative to conventional gasoline. Employing natural gas or renewables decreased health impacts by 50% or more over conventional gasoline.

These results point to health and environmental benefits from the use of EVs in areas where low-emission power generation is employed. They also suggest the potential health benefits of a long-term shift away from coal-fired generation to natural gas generation and renewables.

However, the batteries used in electric vehicles have environmental effects that distinguish them in important ways from internal-combustion engine counterparts. In a future article we'll examine those impacts and how they will likely be affected by the rapid innovation taking place around battery technologies.

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Al Bredenberg is a writer, analyst, consultant, and communicator. He writes about technology, design, innovation, management, and sustainable business, and specializes in investigating and explaining complex topics. He holds a master's degree in organization and management from Antioch University New England. He has served as an editor for print and online content and currently serves as senior analyst at the Institute for Innovation in Large Organizations.

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