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Study finds total PM10 emissions from EVs equal to those of modern ICEVs; role of weight and non-exhaust PM

18 April 2016

A new study by a team from the University of Edinburgh and independent engineering company INNAS BV has found that, when factoring in the additional weight and non-exhaust PM factors, total PM10 emissions from electric vehicles (EVs) are equal to those of modern internal combustion engine vehicles (ICEVs). Non-exhaust PM factors include tire wear, brake wear, road surface wear and resuspension of road dust.

For PM2.5 emissions, EVs deliver only a negligible reduction in emissions, the team found. Compared to an average gasoline ICEV, the EV emits 3% less PM2.5; compared to an average diesel ICEV, the EV emits 1% less PM2.5. Therefore, Victor Timmers and Peter A.J. Achten conclude, the increased popularity of electric vehicles will likely not have a great effect on PM levels. Their paper is published in the journal Atmospheric Environment.

Pm10
Comparison of the expected total emissions of PM10 for EVs, gasoline ICEVs and diesel ICEVs. Data from Timmers and Achten (2016). Click to enlarge.

Non-exhaust emissions tend to contain mostly PM10, but a significant proportion of the emissions contains fine PM2.5 as well. The chemical characteristics of non-exhaust PM emissions vary per source, but are mainly made up of heavy metals such as zinc (Zn), copper (Cu), iron (Fe) and lead (Pb), among others. There are several toxicological studies that have found links between non-exhaust emissions and adverse health effects, such as lung-inflammation and DNA damage, and a review of epidemiological studies concluded that PM10 indeed has an effect on mortality.

… It can be hypothesized that each of the sources of non-exhaust PM emissions should be influenced by vehicle weight. We know that road abrasion and tire wear are caused by the friction between the tire thread and road surface. Friction is a function of the friction coefficient between the tyres and the road, as well as a function of the normal force of the road. This force is directly proportional to the weight of the car. This means that increasing vehicle weight would increase the frictional force and therefore the rate of wear on both the tire and road surface. Brake wear is caused by the friction between the brake pads and the wheels. The energy needed to reduce the momentum of a vehicle is proportional to the vehicle’s speed and mass. Therefore, as the mass of the vehicle increases, more frictional energy is needed to slow it down, leading to greater brake wear.

Resuspension is caused by the wake of a vehicle, which in turn is determined by the size, weight and aerodynamics of the vehicle. Furthermore, heavier vehicles are able to grind down larger particles into smaller, more easily suspended PM. In addition, many heavier vehicles will also be larger, resulting in a larger wake. These factors together should cause increased resuspension.

—Timmers and Achten (2016)

Timmers and Achten analyzed the existing literature on non-exhaust emissions of different vehicle categories, and found that there is a positive relationship between weight and non-exhaust PM emission factors.

Further, they found that EVs are on average 24% heavier than equivalent ICEVs. For example, the Ford Focus Electric and gasoline-powered Ford Focus hatchback have almost exactly the same specifications; the EV, however is 219 kg heavier. Likewise, the Honda Fit EV is 335 kg heavier than the conventional version; the Kia Soul EV is 311 kg heavier than the regular Kia Soul, etc.

A 2013 study by a team at Paul Scherrer Institute found that an increase in weight of 280 kg will result in a PM10 increase of 1.1 mg per vehicle-kilometer (mg/vkm) for tire wear, 1.1 mg/vkm for brake wear and 1.4 mg/vkm for road wear. For PM2.5, these values are 0.8 mg/vkm, 0.5 mg/vkm and 0.7 mg/vkm for tire, brake and road wear, respectively.

However, a different study found that the brake wear of EVs tends to be lower because of their regenerative brakes. Because there is little research which has investigated the actual reduction in emissions resulting from EV braking, Timmers and Achten assumed a conservative estimate of zero brake wear emissions for EVs.

Based on a different study, they assumed a linear relationship between weight and resuspension, and used a 24% increase in resuspension for EVs (due to the on average 24% increase in weight).

On the combustion side, the advent of PM emission standards and new particulate filter technology has greatly reduced exhaust particle emissions from new ICEVs.

Averaging the emission factors from US and European emission inventories, Timmers and Achten obtained a PM10 emission factor of 3.1 mg/vkm for gasoline cars and 2.4 mg/vkm for diesel cars. In terms of PM2.5, these values were 3.0 mg/vkm and 2.3 mg/vkm for gasoline and diesel cars, respectively.

Timmers
Timmers and Achten (2016). Click to enlarge.

… EVs are not likely to have a large impact on PM emissions from traffic. Non-exhaust sources account for more than 90% of PM10 and 85% of PM2.5 emissions from passenger cars, and this proportion is likely to increase in the future as vehicles become heavier. Policy so far has only focused on reducing PM from exhaust emissions. Therefore, future European legislation should set non-exhaust emission standards for all vehicles and introduce standardized measurement methods. In addition, it is recommended that EV technology such as lightweight car bodies and regenerative brakes be applied to ICEVs, and incentives provided for consumers and car manufacturers to switch to less heavy vehicles.

—Timmers and Achten (2016)

Resources

  • Victor R.J.H. Timmers, Peter A.J. Achten (2016) “Non-exhaust PM emissions from electric vehicles,” Atmospheric Environment, Volume 134, Pages 10-17, doi: 10.1016/j.atmosenv.2016.03.017

April 18, 2016 in Electric (Battery), Emissions | Permalink | Comments (16)

Comments

Reducing total weight of BEVs and FCEVs by 50%, improving tires and braking materials would do a lot towards less PM 2.5 and PM 10.0

Using automated e-drones for city delivery would also help?

Reducing mail delivery (with Internet) by another 50% would also help to reduce the number of vehicles of the streets/roads.

Am I reading this correctly: They're counting "resuspension" of particles against EVs? Does that truly mean to resuspend or kick up dust and particulates left on the road by other vehicles? ....so...they're blaming EVs for SH*T left behind by other vehicles?
Do they also blame wind for this? Forget nukes, the new chant is "NO WIND! NO WIND! NO WIND!!!" LMAO!!!

This "resuspension" accounts for 75.5% of the "Total PM" they attribute to EVs. So ICE vehicles dump shyt on the road, and it's the EV's fault for rolling through it!!! LMMFAO!!!

I believe this is one of the most irresponsible and MORONIC studies I've seen in years.

They also ignore the fact that most EVs use harder compounds to reduce rolling resistance which reduces particulate coming from their own tire wear. But that's a tiny fraction of the total miss on this study so who really cares.

I think the “resuspension” is a bit of a red herring. Yes, it’s true that a heavier, larger vehicle would grind more debris and create a greater wake disturbance (ceteris paribus), but it seems like a temporary effect that would be relevant only in the immediate locality of the wake event and not meaningful beyond a small radius.

So ignore that altogether. What you get is still something you wouldn’t expect: the PM emissions of an equivalent BEV and ICE car are not nearly as different as one would expect. If someone were to say that the measureable difference would not be 100% less PM but “only” about 35-40%, I think most of us would be surprised. Moreover, if some mild 48v electrification were added to the ICE with little additional weight but a 10-15% fuel economy improvement and modest regeneration, the difference would close even more.

I believe Engineer-Poet has noted the significant effects of tire wear on particulates, and thus the effect of EV excess weight on measureable pollutants.

The internal combustion engine requires a new operating cycle because existing cycles do not satisfy the law of conservation of energy.

"Brake wear is caused by the friction between the brake pads and the wheels." They also don't take into account that most EV utilize regenerative almost completely eliminating brake pad dust.

Pao: "existing cycles do not satisfy the law of conservation of energy" In what way does this violation of fundamental physics occur?

Paroway: Methinks you didn't read the article or look at the chart. From the article: "Because there is little research which has investigated the actual reduction in emissions resulting from EV braking, Timmers and Achten assumed a conservative estimate of zero brake wear emissions for EVs." So they assume it's ZERO, which is pretty low. Also look at the chart, and see that there is no layer on the bar for "brake wear".

EVs will become lighter with each successive generation of battery technology. As BMW has shown, it is possible to drop 1,200 lbs off of a contemporary passenger car, with battery cost savings offsetting part of the lightweighting cost penalty.

I suspect that the linear extrapolation of weight to resuspension may be flawed. CoD probably has an effect, and EVs are usually superior in this regard.

The good news is that BMW i3 has heavy regen, so 90% of the time no brake dust is created. The Volt 2.0 how has a regen button under the steering wheel, and the Leaf has a heavy regen option.

I suspect this is a study that is funded by lobbyists from the oil industry and the old auto industry that are interested in talking bad about the quality long-range BEVs they don’t want to make.

The study “fails to tell” that emissions from combustion engines is by far the most life-shortening emissions a car produce.

The study “fails to tell” that the second most dangerous type of emissions come from braking dust that contains high levels of toxic cobber. These are emissions that BEVs have almost none of and gassers have lots of.

The study “fails to tell” that the third most important kind of emission is dust created when wearing down the transmission system and moving engine parts which causes much more emissions in a gasser that has a far more complex transmission and hundreds of times more moving engine parts than battery electric vehicles.

The least important kind of emissions is that of rubber and road dust created from friction between the road and the wheels. The only dangerous materials that are on the road are residual exhaust particles and braking particles already produced exclusively or primarily by the gassers not the BEVs. That should not count as particle emissions from BEVs. When all vehicles become BEVs there will be none of these particles left on the road.

With regard to tire wear which is the only type of emission that BEVs may have that is higher than gassers because of more weight the problem is not analyzed properly. Is rubber dust dangerous for the environment or not and to what degree and how it is related to vehicle weight? These questions are the relevant to study.

Again self-driving BEVs will be much less heavy than today’s non-fully self-driving BEVs because they can be right sized in a taxi service only sending a two seater when transport for one or two is ordered. They also share capital cost for the vehicle among many making it more profitable to make self-driving vehicles with low weight materials that cost more but can save on fuel and maintenance.

False title:
"total PM10 emissions from EVs equal to those of modern ICEVs".
In the test you can see that it refers to "non exhaust emissions".
But, what is the proportion of the "exhaust emissions" and the "non exhaust emissions" in all the emissions of a ICEV vehicle?

If there is a proportion of 90% of exhaust, and 10% non exhaust.... Then there is not absolutely any importance in the "non exhaust" emissions of the EV vehicle.

Who paid for this research? Very, very poor job!

The 'expected' values need objective measurements which fortunately can be done with road-size metrics today. It won't be the first time that a paper study crash into reality.

I am a little concerned with all three models have exactly the same total value. It suggests the basis of estimate needs empirical observation.

Bob Wilson

Feel free to read "The most detailed analysis of human health impact of Electric Vehicles" at
http://mobi.vub.ac.be/mobi/news/the-most-detailed-analysis-of-human-health-impact-of-electric-vehicles-by-mobi/

This study is scientifically valid and there is nothing wrong with it, contrary to many critics above.

A heavier vehicle will require more tire contact area with the road and thus will kick up more dust, as well as generating more tire wear and road wear.

Some critic above are blaming on the dust particles produced by ICEV's like brake pad wear and exhaust particles, however, fine and very fine dust particles are found on the surface of the Moon and Mars where there are no vehicles, let alone ICEV's. So, dust will be there no matter whether there are vehicles or not, and heavier vehicles will kick up more dust as they pass by.

The vehicles that are generating the least particles are the Hybrid gasoline-Electric Vehicle (HEV), having weight comparable to a non-hybrid gasoline vehicle, yet very little brake pad wear, and ultra-low-emission engine without engine idling produces very exhaust emission, in comparison to a gasoline non-hybrid with higher engine emission due to operation at low loads and at idle, with poor combustion.

Policy makers should have more incentives to promote more HEV's instead of heavier and more resource-consuming Battery Electric Vehicles (BEV's). The BEV tax credit incentive are consuming precious tax dollars while in fact, the now un-promoted HEV's are giving the most health benefit and economic benefit.

The study doesn't talk about lightweight EV like BMW i3... one of the best EV/PHEV.


So what is the validity of the study if the study ignore that ?!

The study title is "Study finds total PM10 emissions from EVs equal to those of modern ICEVs; role of weight and non-exhaust PM". The total PM10 will include exhaust emission which is currently about the same as non-exhaust, so diesel emission about 2x BEV. Gasoline/gas PM emissions are small in mass but maybe not number. Hybrid EVs have batteries and may well be heavier than non hybrid versions.

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