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Articles on Electric Vehicles

November 14, 2015
Paul Gipe

Why We Drive Electric: Much Fewer Overall Emissions

This is the third in a series on why chose to lease a Nissan Leaf in the fall of 2014. There are several reasons to drive an Electric Vehicle (EV). Any one of them alone is enough to take the plunge.

Electric Vehicles (EVs) are simply cleaner than driving cars powered by fossil fuels, regardless of whether they use gasoline or diesel fuel.

Now there are some, especially here in Bakersfield, the oil capital of California that find this hard to accept—or worse don’t think it’s very important.

For many though, how we produce and use energy is important and especially so in an era of rampant climate change. We need to burn less fossil fuels and those that we do burn we need to burn as efficiently as possible for those uses where it can’t be avoided.

EVs are no environmental panacea. They do nothing to curb suburban sprawl, for example. Nor are they better for the environment than using an electrified train for intercity travel. And, of course, they are quite inferior to walking or cycling to pick up the proverbial loaf of bread.

Nevertheless, if we are to address air pollution and climate change from transit, we are going to have to switch from cars using Internal Combustion Engines to EVs. The sooner, the better.

While EVs don’t have a tail pipe and produce no tail-pipe emissions, they do require electricity and that electricity may be generated by burning fossil fuels. This is sometimes called the Long Tail Pipe.

In most respects EVs are just like conventional cars. They are manufactured the same way, using the same materials. However, they don’t have an engine. They have a large traction battery. With today’s battery technology, the traction batteries are slightly more energy intensive than that of an engine. This contributes slightly to the Long Tail Pipe.

How much total pollutants are emitted powering EVs relative to an ICE burning gasoline or diesel is a function of the power plants used to generate the electricity for the EV.

It’s the Mix, Stupid

It’s not far off the mark to say that there’s no overall environmental benefit from burning coal to generate electricity for an EV. (An EV still provides local air quality benefits to prevent ground level smog.)

Yet even in states, such as Indiana, that predominantly use coal to generate electricity, coal doesn’t provide all the electricity. There is always a mix of resources used to generate electricity. It’s the mix that’s important in determining the emissions from electricity generation.

There is little or no air pollution from hydro-electricity. Similarly, there’s relatively little air pollution from generating electricity with solar panels or wind turbines.

And specifically in terms of global warming gases or CO2e (or carbon dioxide equivalent), generating electricity with natural gas emits half the carbon of burning coal.

Generating electricity with wind energy, even after accounting for the energy used in the steel, fiberglass, and concrete, emits two orders of magnitude less global warming emissions than using gasoline, diesel, or coal.

Argonne National Laboratory created a detailed input-output model of emissions and energy used in the manufacture and production of various goods, such as the traction batteries in EVs and the electricity that’s used to power them.

The Union of Concerned Scientists (UCS), an advocacy group, used the Argonne model to calculate the mpg equivalent of carbon dioxide emissions for EVs relative to conventional Light Duty Vehicles by region. Their report, Cleaner Cars from Cradle to Grave (2015), updates UCS’ earlier work to include the emissions in the manufacture of EV traction batteries relative to that of conventional vehicles.

Not surprisingly, the manufacture of traction batteries adds only slightly to the total emissions of an EV relative to that of conventional vehicle because of the mass of material in the engine.

For a midsize EV, such as the Nissan Leaf, the manufacture of the traction battery adds only 15% to the total emissions from manufacturing the vehicle relative to that conventional vehicle. For a large EV, such as the Tesla Model S, the traction battery adds about 68% to the emissions from manufacturing the vehicle relative to a large conventional car.

In both cases, though, total lifetime emissions from a conventional vehicle overwhelm any increase in emissions from the traction battery in an EV. The overall emissions from a conventional vehicle are twice that for an EV using the average generating mix in the United States.

But it gets even better. Some regions, such as New York State, the Pacific Northwest, and California use far less fossil fuels than the average. Consequently, the emissions for powering an EV in these regions are far less than that elsewhere. For example, the Pacific Northwest generates nearly two-thirds of its electricity with renewables, New York generates one-third, and California—the laggard—generates 23%.

In terms of total greenhouse gas emission relative to a conventional passenger vehicle, the average EV in California gets the equivalent of 87 mpg, that in the Pacific Northwest 94 mpg, and that in New York State 135 mpg.

Our Nissan Leaf charging here at home in Bakersfield, California gets the equivalent of 97 mpg and emits only 112 grams of greenhouse gases per mile travelled. Our Leaf produces only 29% of the emissions of an average new passenger vehicle, and only 60% of the emissions of a new hybrid.

This is one of the reasons why we drive electric. Our EV produces significantly less total pollution than a conventional vehicle.

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