Your EV may not be so green – but then again, it may.

Nissan LEAF EV

Here we go again. A mainstream news source distills (some would say “distorts”) a complex scientific study into a sensational headline, and the online echo chamber spins the story into a narrative that’s almost the opposite of what the study actually found.

The study, Life Cycle Air Quality Impacts of Conventional and Alternative Light-Duty Transportation in the United States, conducted by the University of Minnesota, examined the air pollution impact for different types of vehicle powertrains, including gas, diesel, CNG, ethanol, hybrid and EV.

Under the headline “Your all-electric car may not be so green,” the AP made much of one of the study’s findings – that an EV powered by dirty energy sources causes substantially more air pollution than does a legacy gas vehicle.

Here’s what the study says: “We find that powering vehicles with corn ethanol or with coal-based or ‘grid average’ electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles.”

The AP article (which does not actually quote from the study) focuses on the first sentence above (EVs bad), briefly summarizing the next two sentences (EVs good) at the end of the piece.

Several EV writers, including John Voelcker and Nikki Gordon-Bloomfield, have already written detailed rebuttals of the AP article. Those few who read the study itself will find that it is far from an indictment of EVs. Rather, its conclusions serve as a call to continue the trend toward cleaner sources of electricity.

Nissan LEAF Rav4 EV

“Our assessment…of 10 alternatives to conventional gasoline vehicles finds that EVs powered by electricity from natural gas or wind, water, or solar power are best for improving air quality, whereas vehicles powered by corn ethanol and EVs powered by coal are the worst,” wrote co-authors Christopher W. Tessum, Jason D. Hill and Julian D. Marshall. “Our findings thus reinforce the benefit of pairing EVs with clean electricity.”

While many eagerly seized on the AP’s headline as the complete story (and some didn’t even trouble to include the word “may”), some at the other end of the spectrum will be reluctant to accept even the assertion that a coal-fired vehicle is dirtier than a gas guzzler. The study does leave unanswered several questions that bear on this point, including:

  • The findings seem to contradict an April 2012 study by the Union of Concerned Scientists, which found that “even when charging an EV with electricity made only from coal, the dirtiest electricity source, the EV has better emissions than the average new compact gasoline vehicle.” The two studies may not be using the same sets of figures – the authors of the new study don’t specify exactly what they mean by a “gasoline vehicle.” Prius, Hummer, or something in between?
  • A coal-powered EV may be a dirty beast, but how many such vehicles are out there? The states with the largest proportion of coal-generated juice (Illinois, Ohio, North Dakota, West Virginia, and Wyoming) have few EVs. California, home to almost half of the nation’s pure EVs, gets almost all of its electricity from natural gas, nuclear and renewables. Instead of comparing an ICE vehicle to a hypothetical coal-mobile, would it be more relevant to compare it to the average EV actually on the road today?

 

Sources: AP, Green Car Reports, Transport Evolved, National Academy of Sciences, Energy Information Administration, Union of Concerned Scientists
Images courtesy of Arnold de Leon/Flickr

  • http://www.GogreenMotion.com Bill Williams

    I saw this coming and in my slides I show the “coal factor”! They are simply wrong and have taken a small piece of the much bigger picture!

    http://www.slideshare.net/greenmotioninc/ev-charging-can-be-simple

  • Chris Kreider

    I’m going to view more of the study to see if their methodology is explained. I’m always surprised though when people talk about how the electricity is made but only talk about the GHG generated at the tailpipe, not including the energy to make the fuel. Extracting transporting, refining, etc should be a large part of the picture and like the different generation types what type of oil and where it comes from make a difference in the generation of pollutants.

  • dogphlap dogphlap

    Here is a link to the study (pdf):

    http://www.pnas.org/content/early/2014/12/10/1406853111

    Best regards.

  • dogphlap dogphlap

    I’ve spent a little time on fig 3 of that report.
    After some false starts and scaling off that bar graph here are the $ damages per gasoline equivalent gallon for diesel, gasoline and an EV fuelled from a fully coal fired power station.

    Diesel: $0.46
    Gasoline: $0.53
    EV (coal): $2.68

    So the EV is 5 times as bad as the gasoline fuelled vehicle and almost 6 times worse than a diesel (in terms of <2.5 micron particulate matter and ozone (O3)). I find these results hard to believe. Please point out any errors I have have made here.
    The graph I found confusing because it uses a false zero (i.e. zero is the $0.53 damage per gallon of gasoline).

    Best regards.

  • http://www.shockwavemotors.com/ ShockwaveMotors .

    Having read the article, I noticed no mention was made of the fact that it takes about 8 kilowatt-hours of electricity to make one gallon of gas. That much electricity will power an efficient electric vehicle 40 to 50 miles.

    • dogphlap dogphlap

      Do you have a source for that ? I’m assuming those are US gallons.
      I normally use 1kWh/Litre which is very roughly half the energy you suggest (but I’m very unsure of this figure so I am interested in your number).
      Best regards.

      • http://www.shockwavemotors.com/ ShockwaveMotors .

        There are several sources. This one: http://gatewayev.org/how-much-electricity-is-used-refine-a-gallon-of-gasoline “Jack Rickard …. had done some research and estimated it was between 4-7.5 Kwh per gallon.” and here is a interview where Elon Musk talks about it taking 4 to 6 kilowatt-hours. http://www.businessinsider.com/elon-musk-and-chris-paine-explain-how-the-electric-car-got-its-revenge-2011-10 These figures are costs for the refinement and don’t include transportation costs.

        • dogphlap dogphlap

          Hi Shockwave,
          I miss-directed my reply to you to myself.
          I’d guess you can see it OK though.
          Best regards.

        • dogphlap dogphlap

          OK, so it looks like both our factors fall within the uncertainty band, I’m on the low end while you are closer to the high end. The oil refiners themselves don’t like to publish these numbers. Thank you for the info. My figure comes from Robert Llewellyn (see Fully Charged videos on YouTube etc, but he works in imperial gallons though I prefer litres).
          Best regards

      • dogphlap dogphlap

        This reply should have been directed to ShockwaveMotors.
        OK, so it looks like both our factors fall within the uncertainty band, I’m on the low end while you are closer to the high end. The oil refiners themselves don’t like to publish these numbers. Thank you for the info. My figure comes from Robert Llewellyn (see Fully Charged videos on YouTube etc, but he works in imperial gallons though I prefer litres).
        Best regards

      • Michael B

        I believe it takes 4-8 kWh of *energy*, not electricity, to refine a gallon. Maybe 10% of that energy is electric, and the rest in the form of heat. The people who claim this convert the heat BTUs to kWh, which is the source/cause of this deceptive and oft-repeated canard.

        • dogphlap dogphlap

          You can believe that if you wish. Does not make it true though.

  • http://Getgreentv.com/ Jeff Theisen

    The facts are clear anyone that says EV is not as clean as a gas guzzler is just lying to get attention. They should never again be considered credible for any factual opinion.

  • Michael B

    California may get “almost all of its electricity from natural gas” (LOL), but Los Angeles surely does not. Quite recently more than half of LADPW’s electricity came from coal-fired plants (imported from out of state so I guess that doesn’t count, right? Ha!). They are mandated to eliminate that, however (by 2025).