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Imagine an electric car in a country where most energy come from coal (which i believe is the dirtiest). Add this to the pollution that disposing the batteries will create, or the carbon footprint generated during its production.

Is this car really beneficial in terms of carbon emission and pollution compared to a modern petrol or diesel engine car?

ariel
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  • While the claim is implicit here, I think it is a valid question. Manufactures and proponents of electric car often claim such cars are ecological. Still, some link to some particular claim would probably make the question better. – Suma Aug 05 '11 at 19:41
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    related: http://skeptics.stackexchange.com/questions/351/does-a-car-with-a-hybrid-engine-and-lithium-batteries-pollute-more-than-a-car-wit – Borror0 Aug 05 '11 at 20:15
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    Cars powered by gasoline are getting quite efficient (including hybrid vehicles). Nevertheless, a real advantage of vehicles that get their power by the grid is *adaptability*. As new methods of generating power (including green) come on-line, vehicles can automatically use them. They aren't necessarily tied to oil. – Mike Dunlavey Aug 06 '11 at 03:00
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    Your question has an explicit assumption of coal-sourced electricity. You've set the parameters to the question, and that is legitimate. But, it means the title to the question is misleading. In countries that are have, or are trying to have, less fossil-fuel-based electricity, the answer may be very different. – Oddthinking Aug 07 '11 at 02:23
  • @oddthinking i believe the answer to this question is pretty obvious for a country where most electric energy is from low carbon sources, isn't it? – ariel Aug 08 '11 at 04:53
  • Ariel, not [*obvious*](http://skeptics.stackexchange.com/questions/351/does-a-car-with-a-hybrid-engine-and-lithium-batteries-pollute-more-than-a-car-wit), no. And even if it was, the title is still misleading. – Oddthinking Aug 08 '11 at 08:10
  • @Suma - The gains are on local air quaility. You are not buring the fuel locally there is less air pollution. In a place like LA and Phoenix that matters as traffic exhaust contributes to signifigant Air pollution that stays in place due to the weather patterns and effect of the mountains around them. Sure there is lots of pollution in flyover country but we dont really care about that so long as the left coast is clear and we can make it look like its because we love the enviornment... Did i mention some people are getting rich from it to boot. Win all around for the left. – Chad Aug 08 '11 at 15:04
  • actually, using the coal carbon footprint as a benchmark is relevant also in countries where is only part of the energy sources for electricity. as what we should consider is the marginal pollution - which should consider the most polluting energy source – Ophir Yoktan Jul 20 '12 at 20:24
  • The main environmental benefit of electric cars is not CO2 but urban air quality. They have a secondary benefit which is that where electricity can be generated from renewables or nuclear then that electricity can be used for transportation, but it is only a secondary benefit, not the real reason why they are a good idea. Note also carbon capture is much easier to implement in power stations than it is in cars, so that is another consideration. –  Mar 18 '16 at 16:28

3 Answers3

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This question can be answered using a Life Cycle Analysis, which looks at emissions over the total life cycle of a product - including manufacture, use, and disposal. Many such studies have been performed, here are two examples:

A 2012 UCLA study for the California Air Resources Board, and

A 2015 study by The Union of Concerned Scientists

Both of these conclude that electric vehicles produce lower greenhouse gas emissions than conventional vehicles using California or US electric mix.

From the UCLA study (where BEV means Battery Electric Vehicle, and CV means Conventional Vehicle):

In terms of environmental impacts, the BEV was determined to have the least overall impact, followed by the hybrid, and lastly the CV.

Here is a chart from that report showing the life cycle impacts using California's electric grid fuel mix [coal (7%), nuclear (14%), natural gas (42%), total hydropower (13%), wind (5%), geothermal (5%), solar (0%), and biomass (2%)]. The Battery electric vehicle emits about half the CO2 of the conventional vehicle over its lifetime.

enter image description here

The question specifically asks about the worst case for CO2 emissions - a country where most electricity comes from coal. This is also addressed in the CARB report, through the following figure which looks at different electricity mixes. The study used this mix for China: coal (79%), nuclear (2%), natural gas (2%), hydropower (16%), oil (2%), wind (0%), geothermal (0%), solar (6%), and biomass (0%).

The BEV emissions from the China electric mix are about 2.25 times higher than for the California mix, which would put them at slightly higher than a conventional vehicle, based on the first figure.

enter image description here

It is clear that the cradle-to-grave CO2 emissions are comparable to a conventional vehicle in the most coal-intensive electric grid, and considerably better as the percentage of coal drops. Given that the trend is toward less coal globally, it is clear that the situation will improve from here.

The Union of Concerned Scientists report is focused on the United States, and concludes that electric vehicles produce less CO2 than typical conventional vehicles everywhere in the US

We found that: (1) driving the average electric vehicle in any region of the country produces lower global warming emissions than the average new gasoline car achieving 29 MPG; (2) our ratings in 20 out of 26 regions have improved since our 2012 report; and (3) about 66 percent of Americans—up from 45 percent just three years ago—live in regions where power- ing an EV on the regional electricity grid produces lower global warming emissions than a 50 MPG gasoline car.

Mark
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No, not really.

An electric car uses around 250-300 Wh per mile (1,2) or 155-186 Wh/km. Let's be generous and assume 250 Wh per mile. Coal produces around 2.3 lb of Carbon Dioxide (CO2) per kWh (3) or about 1 kg/kWh. That means your electric car produces 250 g/mile or 155 g/km on average. Even a good petrol engine will beat this; a VW Golf BlueMotion Diesel gets 99 g/mile (4) or 62 g/km.

However, it's not all bleak for electric cars. As an example, in the UK only uses 33% coal (5), so an electric car in the UK would only produce 83 g/mile or 52 g/km CO2, although other fuels produce CO2 as well, they produce it in smaller amounts. It will especially become more environmentally friendly as wind power and other renewable sources are used more.

You also have to take into account the distribution of the fuel; after all, it has to be transported to the fuel station for you to fill up your car, and you have to drive to the fuel station in question, compared to electricity which loses minimal energy in the transmission process, and charging can be done at home.

Oddthinking
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Thomas O
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  • that assumes perfect storage of the electricity (impossible according to thermodynamics) – ratchet freak Aug 06 '11 at 00:59
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    @ratchet Charge/discharge of lithium polymer batteries is about 99% efficient. – Thomas O Aug 06 '11 at 10:59
  • there's also electricity transport from power plant to car. all I'm saying is that the 300Wh/mile would have been a better approximation – ratchet freak Aug 06 '11 at 11:09
  • @ratchet I agree - I was being generous to electric cars and still proving them as being bad for the environment compared to a good diesel, for example. – Thomas O Aug 06 '11 at 12:19
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    You will need many more references to support this post... – Sklivvz Aug 06 '11 at 17:08
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    @Sklivvz I have added references in my post. The statistics, such as Wh per mile, are extremely variable, and sources are hard to find. – Thomas O Aug 06 '11 at 17:27
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    What I meant is that you should really point to studies confirming that your line of thought is correct and not put together bits of information. The environmental impact of a car isn't only determined by its running usage emissions. For example, if you buy a car and never drive it, you are still impacting the environment. – Sklivvz Aug 07 '11 at 09:19
  • You also have to take into account change over time. A gas/diesel vehicle is likely to last 10+ years if taken care of reasonably well. I live in an area where most of our power comes from coal and natural gas, but what power sources will my area use in 10 years? Electric cars are the ultimate in "flex fuel," since they can be fueled by anything that produces electricity. The analyses I've seen that claim electric cars are worse for the environment than gas engines tend to assume coal-heavy electric for the entire life of the car, and don't take into account fuel transport, oil, etc. – Erik Harris Aug 07 '11 at 13:17
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    @ratchet. It's also worth noting that gas and coal don't just appear out of thin air. If you really want to get a thorough analysis of which is cleaner, you should probably look at the total carbon footprint of collecting the raw materials, crude oil, coal, uranium (if you use nuclear power for the electric), or whatever else when figuring out how much carbon is produced when comparing electric to gas engines. – Kibbee Aug 08 '11 at 00:05
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    @thomas O - This covers the CO2 but what about the more signifigant immediate air pollutants like CO and other exhaust fumes created by combustion engines. These are not as naturally occuring and to my mind make a more signifigant threat to the environment. – Chad Aug 08 '11 at 16:11
  • @Sklivvz - Do you have references to back up the claim that not driving a car impacts the environment? – Chad Aug 08 '11 at 16:16
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    @chad, merely the *production* and *destruction* of a car have environmental impact. Do you really need references for that? :-) – Sklivvz Aug 08 '11 at 18:02
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    @sklivvz - Buying that already produced car and just letting it sit is not the same as producing and destroying it though. Particularly if you are buying an old gas guzzler with out modern emmission controls. – Chad Aug 08 '11 at 18:52
  • Manufacturing cost and fuel consumption/transportation also aren't the only factors... electric cars don't use engine coolant, motor oil, transmission fluid, etc... And they probably use other consumables that internal combustion engines don't. – Flimzy Oct 27 '11 at 09:48
  • It is much easier to perform carbon capture and storage at a power plant than it is on a car, so the amount of CO2 produced from coal could be reduced in the future, so there is potential for electric cars to contribute to reducing CO2. –  Mar 21 '16 at 12:08
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If you can install solar panels on your roof, then yes. If you're getting your power from the grid, then no.

Keep in mind, that the solution to CO2 emissions isn't "should we make all cars electric, or should we replace all of our coal power plants", it's both. You can't say "Oh, well, electric cars are no good then" because your local electricity generators are too dirty. Both need to be replaced ASAP. Full stop. And as we do the work to replace the dirty power plants, we simultaneously make existing electric cars cleaner. No further work needs to be done.

So let's stop complaining about how this solution or that solution isn't perfect, and get to work.

Ernie
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    Please [provide some references](http://meta.skeptics.stackexchange.com/q/5) to support your claims. – Oddthinking Mar 18 '16 at 16:15
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    Claim #1: If you can install solar panels on your roof, (or otherwise get power from a zero-emissions source, like hydro or wind power), then yeah, you're reducing the emissions from your electricity to pretty much zero. I don't see how this needs verification. – Ernie Mar 18 '16 at 17:15
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    Claim #2: We need to replace both gas cars and coal power plants to effectively reduce CO2 emissions. What are you looking for here, basic chemistry? – Ernie Mar 18 '16 at 17:17
  • The hypothetical question asked about a hypothetical country that gets all its grid power from coal power plants. Those are literally the dirtiest powerplants in the world. Anything would be an improvement over that. – Ernie Mar 18 '16 at 17:25
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    If this hypothetical question was asked today, rather than in the Beta period where we were still developing our standards, it probably would have been closed as a strawman. – Oddthinking Mar 18 '16 at 23:46
  • Claim #1 needs references. It is frequently called into dispute. See other questions about it here. But your claims also totally ignore the issues posited in the question - the pollution (and energy used in manufacturing) of the batteries and other parts of the electric car. – Oddthinking Mar 18 '16 at 23:49
  • If you get your your power from the grid anywhere in the United States, then yes. If you get your power from the grid in China, then not quite. See the answer I just posted. – Mark Mar 21 '16 at 01:00
  • @Ernie See [Mark's answer](http://skeptics.stackexchange.com/a/32231/21485) if you are confused about the actual complexities here. – Jason C Mar 21 '16 at 03:10