Are EVs actually worse for ambient air quality than cars with combustion engines?

Question

Most air pollution comes not from exhaust fumes but from wear and tear of tyres (it's 1000 times worse, some say). EVs are heavier because of their batteries and therefore release those tyre particles more. Are EVs actually worse for ambient air quality than cars with combustion engines?

Answer 1

This totally depends on what you consider pollution and how you measure it.

If you measure pollution by weight, the vast majority of pollution is carbon dioxide. One liter of fuel produces 2.35 kg of it, so about 42 000 kg of carbon dioxide waste is produced during the lifetime of a combustion engine car. That's about 30-40 times the weight of the car. In that case, EVs win.

I would find it hard to believe that a vehicle would consume 42 000 kg of tyres during its lifetime. A set of tyres loses maybe 15 kg of rubber from new to fully worn, and a car maybe uses 4 set of tyres during its lifetime, so that's 60 kg of tyre rubber waste.

However, if you somehow think that carbon dioxide is not a waste but tyres are, then maybe, maybe not. The second most prominent gaseous pollutant a gasoline combustion engine car produces according to Euro 6 is carbon monoxide. At most 1 gram of it can be produced per kilometer. So in 300 000 km, that's 300 kg. But that's the absolute maximum. A good vehicle could very well produce only 50 kg of it, less than a vehicle produces tyre waste.

However, in today's world carbon monoxide is simply not an issue unless you plan to run your car in unventilated spaces. There's so little of it in air thanks to catalytic converters, so maybe you should consider something actually harmful, like volatile hydrocarbons or nitrogen oxides that produce smog, and even when they don't, nitrogen oxides are directly harmful to human health. A gasoline engine produces at most 0.16 g / km of these combined, or 48 kg during a typical lifetime, so yes, there's less HC + NOx than there's worn tyre rubber. (Especially considering that 0.16 g / km is the absolute maximum, usually the amount is much less.)

So you have to ignore at least two types of pollutants (carbon dioxide, carbon monoxide) to say that tyre rubber is the most significant pollutant. And even then, an EV wouldn't produce twice the amount of tyre rubber waste, maybe it would produce 1.3 - 1.4 times the amount of tyre rubber waste. So if that's the case, even then an EV would pollute less.

Besides, it's very difficult to do these comparisons since comparing by mass may not be the best way to do these comparisons.

Another thing to think about: EVs produce less brake dust due to regenerative braking. That, however, shouldn't matter anymore today since brake pads are free of asbestos.

Still, there's a valid point: tyre rubber waste is a significant problem, and for example biodegradable rubber could be a solution -- if we could only make rubber last long enough when installed in a car, but when broken to fine particles, degrade quickly enough in the environment, while still having excellent grip in tyres.

Answer 2

You need to ask are those numbers realistic:

• Article says car emitted “5.8 grams per kilometer”.
• We assume that car has 4 tyres.
• Kwik-fit (A company that wants to sell tyres, so may be an under estimate) “A general recommendation is that your tyres are changed every 20,000 miles or every 10 years.” (that is 32186.88km)

If we do the maths then we see that we will have used 46.67 kg (102.8 pounds) from each tyre. Are tyres this heavy?

Two blogs say

• Here are some examples: 155/70 R13 can weigh about 6.5 kg. 185/70 R13 can weigh between 7.0 and 7.2 kg. 175/65 R14 can weigh between 6.5 and 7.2 kg
• The average tire is around 15 to 25 pounds (6.8 kg to 11.3 kg).

Therefore, we know that the numbers are bogus.

Answer 3

The relative contribution of tyre wear and tear to the total global amount of plastics ending up in our oceans is estimated to be 5-10%. In air, 3-7% of the particulate matter (PM2.5) is estimated to consist of tyre wear and tear, indicating that it may contribute to the global health burden of air pollution.

source: https://pubmed.ncbi.nlm.nih.gov/29053641/

But we should have in mind that 3-7% are all of tyre wear, from all kind of vehicles. If all vehicles were replaced by EVs, how this number will change?

Let's say it jumps from 3-7 to 5-10%. I don't think that the difference is enough to say it will make any noticeable difference in air quality.

@juhist I think you made a typo, the amount of carbon dioxide produced by 1 liter of fuel should be 2.35 g, not kg.

Answer 4

EV cars have advantages they don't directly pollute in their vicinity. Power plant emissions are dependant on fuel type.

• Coal: there aren't enough EV cars on market to care for exacerbate increased coal use, improvements in air scrubbing technology reduces pollutants. Since plants are often far from cities their pollution is not generally a factor. But typically a ton of particulates is produced per Gigawatt hour
• Natural gas: methane has 2 combustion products, carbon dioxide and water, neither of which are atmospheric pollutants, some nitrous emissions are made due to combustion reaction with atmospheric nutrogen, but considerably less than coal
• hydroelectric: inconsequential, no atmospheric pollutants
• nuclear: inconsequential, no atmospheric pollutants
• wood: considerable, however outside third world and some European nations wood as electricity fuel is rare. However pollutants from wood burning are volatile organics, thus pose no long-term environmental consequences. Forest fires are naturally occurring.