• Jul 24th 2009 at 2:02PM
  • 45
A common attack on electric vehicles is to claim that all Americans switching their cars from gasoline to electric would be counterproductive in the effort to reduce carbon emissions. The reason is that we'd simply need more polluting coal plants pumping out more carbon dioxide and get collapsed electric grids as a result. Well, we know there are emerging solutions to the grid problem but how about calculating the actual carbon numbers that result from gasoline vs. electricity from coal?
Dvice has gone and done just this, and found that, when it comes to CO2, electricity sourced from coal has a 60 percent lower impact than gasoline. Of course, this equation doesn't take in consideration other pollutants that result from burning either fuel.

Let's take our calculators out and check Dvice's numbers: Americans have 250 million cars. Supposing each of these cars could be fitted to a 25 kWh battery (the Tesla Roadster holds 53 kWh, the Chevy Volt will use a 16 kWh pack) and that we can drive 2 or 3 miles per kWh. Assuming that all these cars are used at current average levels (something the source doesn't exactly specify), this translates into 100 charge cycles per year. Total electricity bill: 600 billion kWh per year, and that's just 15 percent of current production (about 4 trillion kWh).

Now, onto the carbon figures: Every kWh from a coal plant produces two pounds of CO2, so we're talking 1.2 trillion pounds of CO2. The U.S. burned 3.3 billion barrels of gasoline in 2008, and a single gallon becomes 20 pounds of CO2 at the exhaust pipe, which turns out to be which about 3 trillion pounds of CO2. Ergo, coal emits 60 percent less.

[Source: Dvice]

I'm reporting this comment as:

Reported comments and users are reviewed by Autoblog staff 24 hours a day, seven days a week to determine whether they violate Community Guideline. Accounts are penalized for Community Guidelines violations and serious or repeated violations can lead to account termination.

    • 1 Second Ago
      • 6 Years Ago
      "Of course, this equation doesn't take in consideration other pollutants that result from burning either fuel."

      Yup. Burning coal emits mercury and other toxins into the environment.

      CO2 is only part of the equation.

      And this doesnt change the fact that it takes much more energy to manufacture an EV than an equivalent gas powered car.
        • 6 Years Ago
        The final plug for EV in the comparison between gasoline cars and coal power plants is the requirement to "start somewhere"

        Even if they came out equal in pollutants ya gotta start somewhere ;) Can't build better EVs without building mediocre ones first.
        • 6 Years Ago
        Don't forget that you can't pump gasoline out of the ground. We pump crude and then expend a lot of energy to refine it into light distillates and other fuels. But what's left over will often be prepared for fueling large ships. And it's very nasty stuff that's full of murcury, sulfur, other heavy metals etc. Even if it's not burned near populated areas it still gets out there. And it's very difficult to scrub at point of use.

        While coal is the dirtiest of fossil fuels it can be very efficiently converted to power and today environmental regs require a lot of high efficiecy aftertreatment that is much cleaner than the essentially untreated exhaust coming out if ships stacks.
        • 6 Years Ago
        Burning gas emits NOx, unburned hydrocarbons and formaldehyde into the environment.
        • 6 Years Ago
        Yes, you're right on both counts. Ideally, though, we can get more and more electricity from renewable sources as time goes on. This will cut out the other pollutants and make the extra power that it takes to make an EV less destructive than nearly any amount that would be used to make anything else with electricity from coal.
        • 6 Years Ago
        EPA provides detailed numbers for emissions of all the major power plants in the US, covering CO2, NOx, and SO2. I found them easily with a little googling. I did my own research paper on exactly this topic, taking into account the energy required to manufacture batteries, and also taking into account the limited lifespan of a battery pack.
        I took a more generous 5 mile/kWh which I based on such examples as the EV1, Chevy Volt, and Reva G-Wiz (all very similar numbers, probably thanks to regen braking which somewhat negates the effect of vehicle mass, and also thanks to the pretty consistent efficiency of an electric motor). The conventional vehicle used for comparison was a 30mpg Ford Focus. I also took into account electricity transmission losses, as well as the losses associated with gasoline refining and distribution (well-to-wheel analysis is often applied to electrics but forgotten for ICEs). For the comparison I looked at a car driving 40 miles a day, 5 days a week over a 10 year vehicle life span.

        I found similar results in terms of CO2 as these guys, looking at a purely coal-charged electric car. I also found that modern cars (which have come a LONG way in terms of reducing NOx and SO2 emissions over the past 20 years) are actually cleaner in terms of NOx and SO2 for this imaginary "coal-only" grid. Needless to say, the case for the EV is much stronger when looking at the actual grid emissions for the US, and especially for Canada with over 50% hydroelectricity.

        @Dave - as you'll see in any life cycle analysis on cars, the manufacturing energy for a car is much lower than the energy used during the life of the car. Just look at any of the critiques of that lame Hummer vs Prius report. My report found that even with a li-ion EV, assuming the battery had to be replaced twice over 10 years (I doubt that would be the case anyways!), the energy requirements to make 3 8kWh packs was much less than the energy required to charge the car over 10 years.
        • 6 Years Ago
        "Even if they came out equal in pollutants ya gotta start somewhere ;) Can't build better EVs without building mediocre ones first." - ghen


        As long as the mediocrity isn't forced down anyone's throat in a hurry, we will be okay in the long run.
      • 6 Years Ago
      If only I could get that efficient coal burning, turbine based technology into an electric drive train hybrid car. Remove the range restriction of batteries and still have less CO2.
      • 6 Years Ago
      link? can we actually read the study?
      • 6 Years Ago
      one point source vs millions. i would go for a single point source even if it was coal every single time. it just makes more sense and is easier to regulate and control
      • 4 Years Ago
      This is a very, very simplistic argument.

      Your average coal fired power plants are no more efficient than gas engines. The best do no better than diesel engines. On top of that, you have transmission losses, conversion losses, charger losses -- you're lucky if you achieve 30% carnot efficiency from fuel to road.

      Taking the energy content of a battery and extrapolating is ignoring a lot of reality. First off, it's an unfair comparison, because a vehicle that gets 2 or 3 miles per kWh is going to be an extremely lightweight one, like a Smart car. If you think consumers are going to put up with that, why not simply use Smart cars instead?

      Transmission line losses can reach several percent. A battery charger will lose several percent. And the battery itself will lose closer to ten percent. These inefficiencies multiply each other.

      Don't get me wrong; I'm not against electric cars. But I'm totally against the "just do this and we can have life as usual" thinking that seems to be going on here.

      In the future, people will be driving a whole lot less, be it electric, coal-to-liquid, diesel hybrid, you name it. Petroleum production has peaked. Those who claim we have lots of coal forget the little footnote: "At current levels of consumption." If you start dumping the current petroleum energy load onto coal, some analysts think we'll hit Peak Coal within ten years. 85 million barrels a day is roughly 150,000 megawatt-hours! That means we need 75,000 new coal-fired plants in the next couple decades to make up for an expected 4% annual decline of petroleum.

      So do what you can to reduce your use. Because there ain't no silver bullet -- electric or gas.
      • 6 Years Ago
      This is incorrect. First he goes through a bunch of unnecessary calculations and assumptions (charges per week etc.) and then he compares apples to oranges: the result of these assumptions versus the actual consumption of gasoline. Very prone to inaccuracy. Let's just compare apples to apples: rates of CO2 consumption.

      Let's be optimistic. Let's ignore transmission losses and assume an EV gets 3 miles per kwh. Then the rate of CO2 production is (1/3 kwh/mile)*(2 lbs/kwh) = 2/3 lbs/mile CO2 production from a coal-powered EV. Compare this to a 30 mpg car. (1/30 gal/mile)*(20 lbs/gal) = 2/3 lbs/mile CO2. The same. Therefore the only way EVs will save CO2 is if we have cleaner electricity production!!
        • 6 Years Ago
        Tesla Roadster with its 53kWh pack can have range over 200 miles. Then it's at least 3.7m/kw. Consider all those CO2 emission from transporting fuels (to fuel stations) too. Even if EV aren't better in absolute sense they open other possibilities. Who know what technological improvements we may expect in regards of electricity generations? (that's for solar panel, breeding nuclear reactors, maybe a nuclear fussion at some point of time)
        And you can generate electricity domestically - think about money which wouldn't have to go abroad for oil imports.
        • 6 Years Ago
        Of course it costs energy to produce batteries as well. I'm not sure how the numbers work out.
        • 6 Years Ago
        Whoops, you have 100% of your electricity coming from coal! Coal now accounts for only 46% of electricity production.


        Whoops, you have accounted for the generation of electricity, but you have gasoline magically springing from the ground, fully refined, right at you local filling station! In realty it takes quite a bit of energy to make and transport gasoline. Refineries are estimated to use about 7KWH to make a gallon of gasoline. An electric car can already go about 25 miles on that much electricity. You also need to account for oil drilling, pumping, water injection, water separation, and shipping. New oil sources coming online from tar sands require massive amounts of energy to turn it into anything useful.

        In realty it's no contest at all. Besides, if coal is such a bad thing, then don't we need to clean that up just to power our homes? Why does it only become a problem when you plug in an electric car?
      • 6 Years Ago
      "Of course it costs energy to produce batteries as well."

      Only once, and then after 100,000 miles you can recycle them.
      • 6 Years Ago
      Pardon me, but this "Greenling" humbly asks if anybody knows where (on that referenced EPA site, perhaps?) do they explain how 19.4 pounds of CO2 are emitted from a gallon of gasoline that weighs between 5.8 and 6.85 pounds per gallon? I got that weight figure from here: http://www.faqs.org/qa/qa-2617.html

      Does it involve some partial pressure equations or something? I'm sure it's clearly explained somewhere, but I'm at a loss to find out how that do that.
        • 6 Years Ago
        CO2 is made up from one atom of carbon (from the gasoline) and two atoms of oxygen (from the air). A carbon atom has an atomic mass of 12 amus (atomic mass units) and an oxygen atom has an atomic mass of 16 amus. Therefore CO2 has a molecular mass of 44 amus, of which only 12 amus come from the gasoline. Gasoline also contains hydrogen atoms (roughly 2 H for each C) with an atomic mass of 1 amu per H. So, if you calculate the mass ratio for n(CH2) to n(CO2) you find that it is roughly the same ratio as gasoline to CO2 produced, i.e. 1 : 3.14. Hope that helps.
        • 6 Years Ago
        Thank you! I'd failed utterly to take into account that this reaction is COMBINING the oxygen from the atmosphere with the carbon in the fuel!
      • 6 Years Ago
      You can lead an EV to a gas station but you can't make it drink.

      "The need for sustainable organic feedstocks and sustainable fuels will remain and ever increase, whether or not EV's thrive sooner or later."

      Yes wouldn't it be nice to use oil for manufacturing goods instead of blowing it up into the atmosphere. I don't agree with your sentence above. EV's sooner would save more gas. But have little effect if China and India continue to use it. Less of our money going over seas would be a benefit.

      China is a toilet and they need to flush it. Next Olympics over there and the athletes will have to bring there own oxygen.
      • 6 Years Ago
      I have different numbers for coal CO2 emission:

      A conventional Coal-burning power plant produces 6150 kWh per Ton of Coal burned or it burns 0.325 lb per kWh that produces. 1 lb of Coal burning releases 3.667 lb of CO2; therefore, 0.325x3.667=1.19 lb(CO2) per kWh.

      With an EV traveling between 2 and 3 miles per kWh, it would compare to a gasoline vehicle that can travel between 32 and 48 miles on one gallon of gasoline. However, EV's are more efficient than that, my conversion EV, a 1994 Saturn could travel 3 miles on one kWh using Lead acid batteries, but the Tesla roadster can do about 4 miles on one kWh, about 64 miles per gallon-equivalent.

      I also think there is an inconsistency on your data, 100 charging cycles per year equals to 2500 kWh per car, at 2 to 3 miles per kWh, that is 5000 to 7500 miles per car per year. 3.3 billion barrels of gasoline is 138.6 billion gallons of gasoline, if each vehicle travels the same 5000 to 7500 miles per year and there are 250 million vehicles, that would be 138600/250=554 gallons per car per year, each one would have to travel only 9 to 13.5 miles per gallon, not realistic.
      • 6 Years Ago
      Burning coal for electricity is still nasty because of the toxic elements released such as mercury, Sulfur, nitrogen oxide & radioactive isotopes. But the smokestack is not the only problem, coal ash is toxic and mining for coal takes its toll on people and the environment.

      But thankfully the electric energy we use comes from a variety of sources depending on where you live. A natural gas plant in my neighborhood is 70% efficient because it uses waste heat to warm campus buildings. I buy wind energy for my house for 1 cent per kWh extra.

      Recently 1.2 billion dollar 300MW coal power plant proposed for Cassville WI that was able to "burn up to 10%* organic waste" was denied by the public service commission because of its high costs and poor emissions. *The actual permit application only listed different types of coal and refinery waste.

      A friend of mine at the electric utility says that payback time on an electric wind turbine is 7 years. When wind is combined with hydro electric and pumped storage there is no good reason to build any more new coal power plants.
        • 6 Years Ago
        Coal isn't nice indeed. But I'm not sure if all those oil related cost are nice too (refineries, drill platforms, geopolitical tensions...). At least with EV it looks like being workable alternative to ICE powered cars. Hopefully there will be bigger push for solar technologies and modern nuclear power plants.
      • 6 Years Ago
      Useful information to counter the rising tide of Stupid EV Myths. It rather reminds me of all the Stupid Hybrid Myths that we had to deal with in the last decade, they still pop up every now and then, but thankfully they are becoming scarce as hybrids are becoming common.

      It looks like we'll be fighting Stupid EV Myths for another decade, until plug-ins become common.
    • Load More Comments
    Share This Photo X