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According to this Flanders Today (a local Belgian newspaper) article

a new small car on petrol in the city creates less fine dust than an electric car of average size.

The researcher, Bruno Van Zeebroeck, claims that this is because

Fine dust is created not just by a car’s motor but also by the wearing out of tyres and braking. Those so-called non-exhaust emissions are higher in electric cars because most of them are heavier than other kinds of cars. These non-exhaust emissions are a particular problem in the city, where drivers brake often.

[...] Van Zeebroeck pointed out that the test didn’t examine the smallest particles of fine dust, which are the most harmful to human health. These particles are mostly emitted by diesel-fuelled cars.

However, I can’t find any research that backs up this claim. Is there any truth in this?

Note: to be clear I'm not interested in possible dust particle emissions from electricity generation, but only emissions that stem from using the car so from tyre wear and braking of electric cars.

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They certainly do not create more particulate emissions, but they might not create that much less than a gasoline powered car, depending on the model of car considered.

First, what was previously thought? According to point IV.a.55 of this report the council of Europe's standing committee on Science and Technology, electric vehicles produce no fine particulate emissions. The report is dated 1998 however, so things may have changed since.

The new study (perhaps review' orarticle' would be better? It's a think tank's internal publication, not peer reviewed) can be read in full here (google translate did a pretty good job this time), but you need to look at the Dutch version for the graphs.

The very first section already answers our question. The author never claims that electric cars produce more particulate emissions than ordinary cars. The title of the section says it all: "Electric cars produce almost as much particulate matter (PM) [as] modern petrol or diesel cars".

The first graph in this section solidifies this. The electric cars considered all have lower total PM emissions than any of the similarly sized cars that are not EVs, though only modestly lower for the most part. A small gasoline car produces slightly less emissions than a medium sized EV however.

Figures 3 and 4 suggest that the reason the advantage is so small now is because tighter emissions standards have dramatically reduced PM from cars over the last 25 years. So when the council of Europe report was written, it probably was fair to say that electric vehicles had no PM emissions at all (as compared to existing gasoline powered cars), but this is apparently no longer true.

The last part of the section concerned with emissions seems very badly done to me, and at best is educated speculation. The author tries to mathematically compute an estimate for the increase in PM emissions from the extra weight of an electric car, but uses an unsourced formula with very nice round numbers, that I believe is likely to have been made up on the spot (33.33% factors for everything?). Even this slipshod analysis finds that the electric version of a normal family car is no worse than the gasoline version for PM emissions, and smaller EVs are much better.

On the whole, I think the news story ought to have been: "Emissions Standards so Good that Gasoline Cars Now Competitive with EVs!" which is still exciting, but doesn't mislead the reader into thinking this was always the case, or that it's an argument against EVs in and of itself (remember, EVs are unchanged at the level of PMs that Council of Europe considered to be zero. It's that gasoline powered cars have dropped by > 75% for gasoline, and even more for diesel since the report was written).

  • 6
    Do electric cars use regenerative braking instead of friction-operated brake pads? – ChrisW Dec 30 '14 at 18:59
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    This is considered by the article, near the end of the section concerned with emissions. They conclude that the use of regenerative breaks offsets some of the brake pad dust emissions, but only a very small amount (16% as I recall...). However, I'm also not confident the methodology in that section is at all good. – John Doucette Dec 30 '14 at 19:25
  • @ChrisW and John - AIUI, the 16% comes from a 33% attribution of particulates to brakes, and a 50% reduction in that from regenerative braking. Each of these seem to be numbers pulled out of the air for the sake of being able to do a calculation. (table 2 and other bits of page 6 of the report) – EnergyNumbers Jan 5 '15 at 14:10
  • This report umweltbundesamt.de/sites/default/files/medien/publikation/long/… (German Ministry of Environment, 2007) may give some useful estimates. According to their projection, the abrasion (both tires and brakes) : exhaust PM2.5 was to be about 1:1 in 2010 and 2:1 by now, and for cars (as opposed to small and large trucks) by now 4x as much abrasive PM2.5 than exhaust PM2.5. Other comparisons: PM2.5 by car exhaust is a bit more than PM2.5 by BBQs, 30% of PM2.5 by cigarette smoke or 62% of PM2.5 by fireworks (happy new year!). – cbeleites supports Monica Jan 14 '15 at 16:05
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The source of electricity may be a bigger issue than tyres and brakes.

The Economist had a recent article "Cleaner than what? Why an electric car may be much dirtier than a petrol one". It concluded

Overall, the research shows that electric cars are cleaner than those that rely on internal-combustion engines only if the power used to charge them is also clean. That is hardly a surprise, but the magnitude of the difference is. How green electric cars really are, then, will depend mainly on where they are driven. In France, which obtains more than half its power from nuclear stations, they look like a good bet. In China—which is keen on electric cars, but produces some 80% of its electricity from coal—rather less so.

It was pointing at a recent article "Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States" by Christopher W. Tessuma, Jason D. Hill, and Julian D. Marshall in PNAS vol. 111 no. 52, 18490–18495, doi: 10.1073/pnas.1406853111, which included the following chart

enter image description here

Fig. 2. Air quality health impacts in the United States for each scenario: attributable increases in annual mortality (upper scale) and the resulting monetized health impacts (lower scale).

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    All that this shows is that using power generated from coal produces lots of PM output. The cars themselves do not produce more PMs than gasoline powered ones. Further, the Council of Europe's report in my answer notes that the reason PM emissions from EVs should be discounted is that the emissions do not need to be concentrated in densely populated areas, unlike the emissions from gasoline powered cars. – John Doucette Dec 30 '14 at 20:34
  • @John Doucette: I'm not sure people in China would necessarily agree that dispersion works. – Henry Dec 30 '14 at 21:28
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    The OP's claim is clearly not about emissions caused by the entire life cycle, so while interesting, this doesn't answer the question. – Is Begot Dec 31 '14 at 0:45
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    I think you mean to respond to @Geobits in your second comment? I'm not sure what your point is. Just because China hasn't made use of low-emissions fuels for their electricity generation, and hasn't or can't place their plants far from inhabited areas, doesn't mean that you couldn't do so elsewhere. In Germany or France for instance, PM emissions for EVs would be far lower because a much larger share of their electricity comes from cleaner sources. If the emissions depend on where you are, then clearly it's not a problem with the car -- it's a problem with your fuel. – John Doucette Dec 31 '14 at 1:52
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    @Henry There's a question more specifically asking about life cycle impact here. Nothing in the OP asks about anything other than point-of-use emissions (engine, tires, brakes, etc). – Is Begot Dec 31 '14 at 13:27

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