Frequently Asked Questions
Do electric vehicles produce more particulates than petrol or diesel vehicles?
No. Although the difference between electric vehicles and conventional combustion engine vehicles is smaller than people might think.
Despite having no tailpipe, Battery Electric Vehicles (BEVs) still produce particulate matter (PM). Some may be generated from electricity production if the energy mix includes the burning of fossil fuels such as coal. However, the grid is reducing its reliance on fossil fuels every year, so aside from electricity production, the main PM emissions are from mechanical braking, tyres, the road surface and resuspension of road dust.
Electric vehicles use regenerative braking, converting the vehicle's momentum back into electricity, recharging the battery in the process. Hence, electric vehicles hardly use brake pads at all - a fact attested to by C&C taxis in Newquay, who after 100,000 miles of driving their first Nissan Leaf, were still on their first set of brake pads. However, the heavier a vehicle is, the more road dust they can "kick up" when moving, and EVs weigh more due to their batteries.
It's an topic of study where research results vary in their conclusions, with more recent studies generally showing reductions in impacts from battery electric vehicles. As with calculating CO² emissions, it's not a straightforward task to measure and compare results to conventional cars as there are many factors which affect the results. The 2018 report Electric vehicles from life cycle and circular economy perspectives published by the European Environment Agency, looked at the broad environmental impacts of EVs, referencing and comparing a number of the leading studies. It states:
BEVs also emit PM from tyre-road abrasion and resuspension but emit zero PM from exhaust, and emissions from brake pad abrasion are reduced thanks to their use of regenerative braking where possible. Estimates of local PM emissions from BEVs, and the comparison with those of ICEVs, vary considerably because of the difficulty of measuring them reliably in real-life conditions. Using emission factors used in a range of national emission inventories, Timmers and Achten (2016) concluded that BEVs likely produce levels of PM10 and PM2.5 pollution similar to or only slightly lower than those of ICEVs. The rationale for this is that tyre and road wear and resuspension combined make up around 80 % of PM emissions from Euro 6 petrol and diesel vehicles, and that BEVs tend on average to be heavier than the equivalent ICEVs, causing greater rates of road and tyre wear. In contrast Hooftman et al. (2016) found that, when using data on real-world exhaust emissions of PM from ICEVs, BEVs emit only around half and one eighth the total amount of local PM10 compared with Euro 6 petrol and diesel vehicles, respectively. A further consideration is the effect of driving conditions. For example, in stop-start urban driving where speeds are low, brake wear particles can constitute up to 55 % of total PM10 emissions from ICEVs, so regenerative braking by BEVs is likely to provide a large reduction in local PM emissions relative to ICEVs in these conditions (Hooftman et al., 2016). In contrast, on motorways brake wear particles may account for only 3 % of total PM10 emissions from ICEVs (Hooftman et al., 2016), so the advantage of BEVs over ICEVs is smaller, being based mainly on their having zero exhaust emissions.
Thankfully, technology is innovating all the time, and there is potential to reduce particulate pollution from all vehicles by improvements to tyre and brake technologies.
ENSO is a new company developing sustainable tyres, specifically for electric vehicles. They aim to create not only a tyre which performs better, improving the efficiency of EVs and therefore optimising CO² reduction. But also a product with a circular business model - not only with the materials they use but also identifying end-of-life partners who can reuse tyre materials.
Porsche has recently developed a new brake pad system called Porsche Surface Coated Brakes (PSCB), which use tungsten-carbide coated discs. Their system massively reduces the amount of brake dust by around 90% while also improving braking performance. You can see a technical review of these brakes from YouTube channel Engineering Explained. Traditional cast iron brakes are responsible for iron-rich nanoparticles from air pollution which permeate millions of mitochondria inside our hearts, causing cardiac stress and affecting our hearts' ability to pump correctly. So, developments in brake technology must improve for all vehicles to improve public health.
Article last updated on July 10th 2020.