Pollution Efficiency of Alternative Fuel Cars

Every now and then, when discussing EVs (electric vehicles) or other alternative fuel cars1, that offer basically zero pollution (in the form of green house gases and other poisonous gases) someone always raises the argument that these cars just “move the pollution upstream” to the electric power plants and you are still polluting just the same.

But this argument only works if the power production “upstream” really is polluting as much as an onboard gas engine – which really sounds weird to me, because as you increase the success of the engine – from something that had to be small enough to fit in a car to something that basically only had the limit of required to be cost effective – surely you can have large efficiency gains, even if burning the same fuel?

So here are some numbers:

[These are mostly based on US sources because these are easy to come by – and unfortunately these use imperial units instead of SI units. Because all of my figures use these units in not going to bother converting them. While I expect figures from other countries to be a bit different, the difference should be much smaller than my margins of error.]

According to the US Energy Information Administration, the pollution of electric power production using coal – the most polluting commonly used power source – when used in a commercial steam based power generator produces 2.18lb of CO2 per KW/Hr of electricity generated.

Next we can consult Wikipedia’s summary of MPGe rating for some EVs2. MPGe calculation is mostly about comparing the energy content of different fuels, and not at all about pollution, so I’m going to ignore that number and use the KW/Hr numbers quoted there: disregarding the really inefficient cars, the EVs on the list there have high (inefficient) numbers around 0.4 KW/Hr Mile. So a mediocre car that is charged from a lousy power plant generates  about 0.4 * 2.18 = 0.872lb of CO2 per mile traveled.

From the US Environment Protection Agency’s report on average pollution of passenger cars, we learn that the average pollution from passenger cars is 0.916 lb per mile traveled.

So, at worst3 by moving to an EV in reducing my pollution production by 5%. So the argument about EVs just moving the pollution upstream seems legit right?

Well, I still disagree – according to the World Coal Association, coal is used to generate 45% of electric power in the US (58% in Israel). Other fossil fuels can be even twice better pollution-wise, and more and more power generation is moved to zero-emissions power sources such as solar, wind powered, hydro electric, tide power or even nuclear. This is one side of the equation – the other side are the cars themselves – EVs are a new technology: while gasoline engine have been around for more than 100 years and it’s hard b to continue improve on the amount of harmful emissions from these engines4, while there are already EVs that are 30% more efficient than the numbers quoted above, and we can expect large improvements as the technology gets more mature.

A few more back of the envelope calculation can show that current pollution efficiency is more than twice better for EVs vs gasoline cars (considering everything), and the gap is widening fast.

  1. like the new “hydrogen powered” cars []
  2. MPGe is an artificial rating used in the USA to compare efficiency of EVs to gasoline powered cars, as inherently these two different engines use different units to measure cost of energy []
  3. nor really the worst because I’m disregarding the Chinese BYD e6 []
  4. not impossible, but hard and improvements are expected to be small []

2 Responses to “Pollution Efficiency of Alternative Fuel Cars”

  1. Eran:

    One more thing, by moving the pollution upstream, if you’re still using messy polluting power plants, you’re concentrating the impact. That way, it’s easier to capture it.

    • Oded:

      True – by moving all the pollution to large providers you make it easier to solve the pollution problems by:
      1. improve on current technologies (as you noted)
      2. replace current generation technology with newer technology that is inherently less polluting
      3. Increase the market for “green credits” – large polluting entities are easier to regulate and can be forced to invest in new clean technologies (not only the power generation business) by buying “green credits”.

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